bluuebunny/crossref_metadata_2025 huggingface dataset:
QoS-Aware Downlink Traffic Scheduling for Cellular Networks with Dual Connectivity
Authors: Su Haoru , Pan Meng-Shiuan , Mai Hung-Wei
Published: September 2022

In a cellular network, how to preserve users’ quality of service (QoS) demands is an important issue. To provide better data services, researchers and industry have discussed the deployment of small cells in cellular networks to support dual connectivity enhancement for user equipments (UEs). By such an enhancement, a base station can dispatch downlink data to its surrounding small cells, and UEs that are located in the overlapping areas of the base station and small cells can receive downlink data from both sides simultaneously. We observe that previous works do not jointly consider QoS requirements and system capabilities when making scheduling decisions. Therefore, in this work, we design a QoS traffic scheduling scheme for dual connectivity networks. The designed scheme contains two parts. First, we propose a data dispatching decision scheme for the base station to decide how much data should be dispatched to small cells. When making a dispatching decision, the proposed scheme aims to maximize throughput and ensure that data flows can be processed in time. Second, we design a radio resource scheduling method, which aims to reduce dropping ratios of high-priority QoS data flows, while avoiding wasting radio resources. In this work, we verify our design using simulation programs. The experimental results show that compared to the existing methods, the proposed scheme can effectively increase system throughput and decrease packet drop ratios.
Design of Compact Planar Monopole UWB MIMO Antenna with Four Orthogonal Elements and Tapered Fed Configuration for Wireless Diversity Applications
Authors: Kolangiammal Shanmugam , Balaji Loganathan , Mahdal Miroslav
Published: September 2022

In this paper, we introduce a four-port self-isolated UWB MIMO antenna for diversity applications. First, we have developed a basic radiating element of the proposed antenna in four stages of design, where patches of geometrically different shapes were added at each stage to arrive at the final radiator form. The antenna was designed on an FR-4 substrate with a compact size of 28 × 28 × 1.6 mm3. A tapered microstrip feeding was employed to enhance the antenna’s impedance matching. An orthogonal arrangement of the four radiators was adopted to mitigate the mutual coupling between them, avoiding the use of a separate isolation structure. A prototype was built and measured with a close agreement between the experimental and simulated results. The MIMO antenna performed well in the entire frequency spectrum of 3.1–10.6 GHz, with an isolation better than 20 dB. The measured envelope correlation coefficient (ECC) was less than 0.001, the diversity gain (DG) was greater than 0.99 dB, and the total active reflection coefficient (TARC) was less than −10 dB. The performance of the proposed antenna design was compared with existing designs. The comparison showed that the proposed quad-element UWB MIMO array is compact, has good isolation and diversity performance compared to existing designs, and is well-suited for wireless diversity applications.
Fast CU Partition Decision Algorithm for VVC Intra Coding Using an MET-CNN
Authors: Wang Yanjun , Dai Pu , Zhao Jinchao , Zhang Qiuwen
Published: September 2022

The newest video coding standard, the versatile video coding standard (VVC/H.266), came into effect in November 2020. Different from the previous generation standard—high-efficiency video coding (HEVC/H.265)—VVC adopts a more flexible block division structure, the quad-tree with nested multi-type tree (QTMT) structure, which improves its coding performance by 24%. However, it also causes a substantial increase in computational complexity. Therefore, this paper first proposes the concept of a stage grid map, which divides the overall division of a 32 × 32 coding unit (CU) into four stages and represents it as a structured output. Second, a multi-stage early termination convolutional neural network (MET-CNN) model is devised to predict the full partition information of a CU with a size of 32 × 32. Finally, a fast CU partition decision algorithm for VVC intra coding based on an MET-CNN is proposed. The algorithm can predict all partition information of a CU with a size of 32 × 32 and its sub-CUs in one run, completely replacing the complex rate-distortion optimization (RDO) process. It also has an early exit mechanism, thereby greatly reducing the encoding time. The experimental results illustrate that the scheme proposed in this paper reduces the encoding time by 49.24% on average, while the Bjøntegaard Delta Bit Rate (BDBR) only increases by 0.97%.
Formal Modeling and Verification of Smart Contracts with Spin
Authors: Yang Zhe , Dai Meiyi , Guo Jian
Published: September 2022

Smart contracts are the key software components to realize blockchain applications, from single encrypted digital currency to various fields. Due to the immutable nature of blockchain, any bugs or errors will become permanent once published and could lead to huge economic losses. Recently, a great number of security problems have been exposed in smart contracts. It is important to verify the correctness of smart contracts before they are deployed on the blockchain. This paper aims to verify the correctness of smart contracts in Ethereum transactions, and the model checker Spin is adopted for the formal verification of smart contracts in order to ensure their execution with respect to parties’ willingness, as well as their reliable interaction with clients. In this direction, we propose a formal method to construct the models for smart contracts. Then, the method is applied to a study case in the Ethereum commodity market. Finally, a case model is implemented in Spin, which can simulate the process’s execution and verify the properties that are abstracted from the requirements. Compared with existing techniques, formal analysis can verify whether smart contracts comply with the specifications for given behaviors and strengthen the credibility of smart contracts in the transaction.
A Comprehensive Framework for Direct Lightning-Structure-Human Interaction Modelling in Heritage Monuments and Safety Assessment
Authors: Sreedhar Srisailam , Indragandhi Vairavasundaram
Published: September 2022

Lightning is a perilous and unavoidable event of nature that presents major deleterious consequences on humans, tall structures, electrical power systems, forests, etc. Though several research studies have been carried out to analyse the sufficiency of a Lightning Protection System (LPS), very few research findings have been reported to assess the extent of risk due to lightning-human interaction in the vicinity of tall structures. This research aims at carrying out detailed modelling and simulation studies of LPS for heritage structure. Several current waveshapes as stipulated in IEC 62305 are modelled appropriately and presented to the electrical equivalent circuit representation of a heritage monument in South India (Brihadisvara Temple) to ascertain the impact of lightning parameters on heritage monuments. In addition, to assess the effectiveness of the earthing system, detailed earthing models during lightning is developed to assess the role played by aspects such as soil resistivity (single and double), earth electrode dimensions, nature of elements in the equivalent circuit, etc. Further, the role of lightning strikes on human due to step and touch potential is ascertained by formulating a lumped electrical equivalent model of human to assess its role and impact on dry and wet skin.
Life Cycle Energy Consumption and Air Emissions Comparison of Alternative and Conventional Bus Fleets in Vietnam
Authors: Luu Le Quyen , Riva Sanseverino Eleonora , Cellura Maurizio , Nguyen Hoai-Nam , Tran Hoai-Phuong , Nguyen Hong Anh
Published: September 2022

The study (a) assesses the life cycle energy consumption and air emissions impacts of battery electric buses (e-buses) and conventional buses operated in Vietnam, and (b) compares them with those of hydrogen buses. The results indicate that e-buses and hydrogen buses are preferred options compared to conventional buses in terms of energy consumption, GHG emissions and other air quality impacts over their whole life cycle. Life cycle energy consumption of diesel buses is triple that of e-buses, and is significantly higher than that of hydrogen buses. Replacing conventional buses with e-buses can reduce energy consumption by 50%. For GHG emissions and air quality impacts, the adoption of electric and hydrogen mobility in replacement of conventional buses will reduce GHG emissions by 39%, and other impacts related to air quality by 13% to 90%.
Changes in Energy Sector Strategies: A Literature Review
Authors: Sulich Adam , Sołoducho-Pelc Letycja
Published: September 2022

Sustainable development (SD) can indicate the direction of the development of modern organizations’ transition and transformation strategies in the energy sector. Currently, in most countries, the main challenge for the energy sector’s strategies is to deal with energy security. The implementation of SD induces changes both in strategy and technology. The strategies are based on the technological transition toward renewable energy sources (RES). The aim of this paper is to explore business management literature dedicated to the transformation and transition strategies in the energy sector. The adopted methods are a systematic literature review (SLR) accompanied by a classical literature review (CLR) in Scopus database exploration. A literature review is developed in VOSviewer software and keyword co-occurrences analysis allowed to identify the main changes of direction in energy sector transformation strategies. The literature was explored by the 26 queries which resulted with 11 bibliometric maps. The analysis of the bibliometric maps was a challenge due to the cross-disciplinary strategic directions of development presented in indexed publications in the Scopus database. The identification of the changes in energy sector strategies is important because of its reliance on depleting resources and natural environment degradation. As a result of this paper, there is a visible shift of the trend in explored scientific publication from not only technological-based solutions but also towards managerial and organizational practices to achieve sustainability in the energy sector. This paper, besides the results, presents the theoretical contribution and managerial recommendations for business practices and addresses future research avenues. There are discussed implications of the presented analysis for further research.
To Join or Not to Join? The Energy Community Dilemma: An Italian Case Study
Authors: De Santi Federico , Moncecchi Matteo , Prettico Giuseppe , Fulli Gianluca , Olivero Sergio , Merlo Marco
Published: September 2022

Energy Communities (EC) are becoming a major driver to foster the energy transition in Europe and the regulatory framework adopted by each Member State (MS) plays a key role for a prosperous deployment of ECs. This paper is thus divided into two layers. The first layer of this paper addresses the current regulations introduced by MSs regarding ECs, providing a critical comparison of each solution used. The second layer of research concerns the introduction of a Mixed Integer Linear Programming (MILP) optimization algorithm early studied by some of the authors furtherly developed to assess the conditions that favour prosumers’ participation to ECs. Both these models have been tested on a case study located in the city of Magliano Alpi, in the north of Italy. The results demonstrate that the proposed methodology correctly evaluates the key parameters influencing participation of citizens in ECs and indicate that for the Italian EC under study, there is the possibility to further expand the capacity installed without undermining the profitability of investment.
Design and Control of Three-Phase Power System with Wind Power Using Unified Power Quality Conditioner
Authors: Mahdi Dheyaa Ied , Gorel Goksu
Published: September 2022

The Unified Power Quality Conditioner (UPQC) is one of the Custom Power devices (CP), and it mitigates both load current and supply voltage problems (voltage swells, sags, harmonics, etc.) simultaneously. By using CP, we are getting more familiar with renewable energy’s high penetration on the electrical grid because of its intermittent nature, which causes power flection. We are also using powered electronic devices, and non-linear loads produce harmonics that affect the voltage and current waveform. In this paper, a UPQC will be used with a sensitive load that is connected to a grid (grid–wind turbine) power system. The UPQC will operate under different disturbances such as phase-to-ground fault, non-linear load on the grid side, and non-linear load in parallel with the sensitive load, using pulse-width modulation and hysteresis as switching techniques. Simulation results using MATLAB/Simulink are used to compare the two pulsing-generating techniques and show that electrical power is continuously fed to the load in all disturbances with total harmonic distortion (THD) less than 5% for voltage and 4.5% for current.
Influences of Clay Mineral and Organic Matter on Nanoscale Pore Structures of the Cretaceous Lacustrine Shales in the Songliao Basin, Northeast China
Authors: Zeng Weizhu , Song Zhiguang
Published: September 2022

The Cretaceous lacustrine shales of the Qingshankou Formation (K2qn) from the Songliao Basin are recognized as a potential shale oil reservoir in China. Pore structure of shale within the oil window could be significantly influenced by several factors, including mineral and organic matter (OM) compositions. For a better understanding of the factors controlling the pore structure of these shales, 15 core shales from the K2qn were subjected to low-pressure N2 adsorption measurement for both the initial and solvent extracted samples, and the relationships between shale compositions and pore structure parameters were discussed. The results show that the average specific surface area (SSA) and pore volume (PV) increase from 10.14 m2/g to 29.74 m2/g and from 0.0276 cm3/g to 0.0554 cm3/g respectively after extraction, which suggests that the nanopores in these shales could be significantly occupied by the soluble OM, especially for the pores smaller than 10 nm in size. For the extracted samples, the good positive correlations between the SSA and the illite/smectite (I/S) content indicate that a significant amount of small pores are associated with this mineral, while the overall positive correlations between the PVs with the I/S and OM contents suggest that I/S mineral and organic matter (kerogen) have contributed most to pores lager than 10 nm. It is assessed that OM pores contribute approximately 16% to total PV of these shales. Our results will improve the understanding of pore characterization of the clay- and OM-rich lacustrine shales and provide some implications for shale oil accumulation in the Songliao Basin.
Cooperative Optimization of A Refrigeration System with A Water-Cooled Chiller and Air-Cooled Heat Pump by Coupling BPNN and PSO
Authors: Deng Qinli , Xu Liangxin , Zhao Tingfang , Hong Xuexin , Shan Xiaofang , Ren Zhigang
Published: September 2022

Aiming at the issues of unreasonable cooperation schemes and inappropriate setting of parameters of the refrigeration system with multi-chiller plants, this paper presents a cooperative optimization method to improve the energy performance of the system composed of water-cooled chillers and air-cooled heat pumps. The cooperative optimization process includes scheme optimization and parameter optimization. To content the dynamic cooling load, the working sequence of air-cooled heat pumps and water-cooled chillers with variable frequency chilled water pumps is first optimized. Based on the optimal scheme, a back-propagation neural network (BPNN) coupled with particle swarm optimization (PSO) is implemented to explore the preferred operating parameters of multiple chiller plants corresponding to the best coefficient of performance (COP). Compared with the performance of the initial operation module, the energy consumption of the water pump and fan decreases by over 50%, and the COP of the refrigeration system is improved by 16% (COP = 3.85) through the scheme operation. After parameter optimization, the total energy consumption is reduced by 21.7%, and COP is increased by 26.5% (COP = 4.20). Therefore, the proposed cooperative optimization method can provide useful operation guidance for the refrigeration system with multi-chiller plants.
Petroleum Resource Potential Assessment of Members 1 and 3 of the Paleogene Shahejie Formation, Qikou Sag: Insights from Hydrocarbon Generation and Expulsion Capabilities
Authors: Wu Zhuoya , Zhao Xianzheng
Published: September 2022

The Shahejie Formation (Fm) in the Bohai Bay Basin is well-known for its substantial conventional resource potential and long-term history of exploration. Shale oil has been confirmed as a sustainable resource following breakthroughs in shale exploration in the first and third members of the Paleogene Shahejie Fm (Mbr1 and Mbr3) in Qikou Sag, particularly Mbr3, which has a more desirable output. However, the limited distribution of exploration wells for shale oil around the southwest of Qikou Sag calls for a comprehensive evaluation of shale oil (or gas) potential in all of Qikou Sag. Here, we clarify the shale oil (or gas) resource potential and areas favorable for exploration in Mbr3 by using a hydrocarbon generation potential model (HGPM) based on the material balance method and the principle of hydrocarbon (HC) generation dynamics. Apart from the quantified characteristics of the oil generation process of Mbr3 source rocks, the source rocks of both Mbr1 and Mbr3 were compared to interpret the discrepancies in HC generation. The results show that Mbr3 source rocks have high-quality geological and geochemical features, a thickness of 1200 m, and adequate organic matter (1.66% TOC on average, dominated by kerogen II&III, and in the mature stage). The threshold of expulsion is Ro = 0.78%; correspondingly, HC generation potential (Qg), HC expulsion potential (Qe), and retention potential (Qr) are, at maximum, 605.89, 169.65, and 436.24 mg HC/g TOC. The intensity of HC generation (Ig), expulsion (Ie), retention (Ir), and effective retention (Ire) is focused on the main depression and the Qibei Sub-sag and can reach as high as 250 × 104, 65 × 104, 170 × 104, and 110 × 104 t/km2, respectively. The resource potential for the retention of shale was calculated to be 13.3 × 108 t (movable shale oil and gas 8.0 × 108 t), and conventional and tight oil or gas resources were calculated to be 4.7 × 108 t (equivalent oil resources). Favorable exploration targets are spread around the main depression and the Qibei Sub-sag. There are disparities in the thermal process and thermal generation, and expulsion features between Mbr1 and Mbr3 source rocks are derived from kerogen-type and non-isolated deposit environments. Thus, a quantitative, advanced evaluation and a comparison offer more precise exploration predictions of shale in this Fm and further boost the low-risk exploration process.
Study on Hydrogen Production by Supercritical Water Gasification of Unsymmetrical Dimethylhydrazine under Multi-Parameters
Authors: Yi Lei , Chen Jingwei , Liu Zhigang , Chen Huiming , Liu Daoxiu , Liu Zheng , Chen Bin
Published: September 2022

Unsymmetrical dimethylhydrazine (UDMH) is very toxic and hard to decompose in traditional ways. In this paper, the gasification of unsymmetrical dimethylhydrazine (UDMH) in supercritical water was studied in a batch reactor under different conditions. The hydrogen production process of supercritical water gasification of UDMH in metal containers is a multiphase reaction process. The effects of reaction temperature, alkaline catalysts, residence time, and oxidation on gasification were systematically studied. COD and ammonia nitrogen of the residual liquid were tested. Results showed that the maximum molar fraction and yield of hydrogen were 87.0% and 97.9 mol/kg, respectively, with KOH at 600 °C, 23 MPa. The COD removal efficiency in relation to alkaline catalysts was in the following order: NaOH > Na2CO3 > KOH > K2CO3. The highest COD removal efficiency (up to 95%) can be obtained at the temperature of 600 °C, 23 MPa with NaOH as the catalyst, and a residence time of 20 min. Ammonia nitrogen can be decreased by adding an oxidant. The COD and ammonia nitrogen of the residual liquid can meet the requirement of the Chinese emission standard of water pollution for space propellants. In addition, the organic compounds formed under different conditions were also identified.
Examining the Relationship between Renewable Energy and Environmental Awareness
Authors: Szeberényi András , Rokicki Tomasz , Papp-Váry Árpád
Published: September 2022

The use of green and renewable energies undeniably plays an essential role in today’s society. Energy from these sources plays a key role in transforming the energy sector and significantly impacts the way of life and the quality of life of different social groups. The main aspects of this study are to briefly describe the situation of clean and renewable energy in Hungary and to investigate the extent to which the younger generation of different social groups is involved in using renewable energy sources in their everyday lives and their attitudes towards environmental awareness. In our research, we also investigate whether there is a strong statistical correlation between environmental awareness, environmentally damaging activities and the perceptions of different environmental problems among the target groups and, if so, how these affect the research topic. Our primary research can be considered representative, as we surveyed all primary and secondary school students in the Gyöngyös micro-region of the North-Hungarian region and also included the opinion of university students in the mentioned micro-region. The questionnaire was asked in person, and 2180 students completed it. The research was carried out in several phases, the first occurring between 2017 and 2019 and the second between 2020 and 2021. Three research questions were formulated, and the main findings show that the students’ main goal in the research was not to protect or support the environment but to prefer material well-being and related factors. On the results of statistical correlation analyses, overall, the examination by educational level (primary, secondary and higher) does not show significant differences between student groups, i.e., students with higher education do not have higher levels of environmental awareness and attitudes. Another important finding is that using renewable energy sources is considered too expensive for low-income families to take advantage of this kind of energy.
Impact of Reactive Power from Public Electric Vehicle Stations on Transformer Aging and Active Energy Losses
Authors: Pavlićević Ana , Mujović Saša
Published: September 2022

Climate change at the global level has accelerated the energy transition around the world. With the aim of reducing CO2 emissions, the paradigm of using electric vehicles (EVs) has been globally accepted. The impact of EVs and their integration into the energy system is vital for accepting the increasing number of EVs. Considering the way the modern energy system functions, the role of EVs in the system may vary. A methodology for analyzing the impact of reactive power from public electric vehicle charging stations (EVCSs) on two main indicators of the distribution system is proposed as follows: globally, referring to active power losses, and locally, referring to transformer aging. This paper indicates that there is an optimal value of reactive power coming from EV chargers at EVCSs by which active energy losses and transformer aging are reduced. The proposed methodology is based on relevant models for calculating power flows and transformer aging and appropriately takes into consideration the stochastic nature of EV charging demand.
Research on Space Vector Overmodulation Technology of Two-Level PWM Converters
Authors: Zhou Jin , Li Shanhu , Zhang Jianning , Fang Tianrui , Zhang Xiuyun
Published: September 2022

In this paper, the characteristics of the voltage transfer ratio (VTR) and low-order harmonics of the major modern space vector overmodulation strategies for two-level PWM converters are discussed under different VTRs, and the complexity of the modulation algorithm is subsequently elaborated. First, the principles of these overmodulation strategies are summarized. After that, the accuracy and linearization of the VTR are obtained using the Fourier transform analysis, and the relationship between the main low harmonic components and the VTR is obtained in the same way. All the analysis results are verified through experiments. In addition, the merits and demerits of these overmodulation strategies and applications are revealed by comparing the simplicity of their modulation algorithm, digitization, and other characteristics. Finally, this paper reveals the essence of space vector overmodulation strategies. The results facilitate the design, performance prediction, and development of high-performance overmodulation strategies, as well as the transplantation of space vector overmodulation strategies into different converter topologies.
Effects of Elastically Supported Boundaries on Flutter Characteristics of Thin-Walled Panels
Authors: Tian Sumei , Wang Meng , Qi Wuchao
Published: September 2022

In order to investigate flutter characteristics of thin-walled panels with elastically supported boundaries, a method for dealing with the stiffness matrix constraint relationship is developed based on penalty functions. Combined with the first-order piston theory, flutter velocities and frequencies of thin-walled panels with the different cases of elastically supported boundaries are calculated. Firstly, a thin-walled panel is discretized by the finite element method, and springs with real stiffness coefficients are introduced to simulate elastically supported boundaries. Then, the pressure difference between the outer and inner surfaces of the panel and modal aerodynamic expressions are obtained by introducing the first-order piston theory. Finally, flutter equations are obtained in the time domain by combining the structural dynamic equations with the modal aerodynamic forces. Subsequently, they are transformed to the frequency domain at the flutter state. Then, flutter characteristics of the panel are obtained using the U−g method. The results show that the existence of elastically supported boundaries may reduce the flutter velocity and flutter frequency of the panel but can be enhanced and recovered through some appropriate damping configuration schemes. Calculating the flutter characteristics of thin-walled panels under elastically supported boundaries can more accurately simulate real supported situations and result in a safer design scheme for thin-walled panel structures.
Dynamic Stability Study of Grid-Connected Inverter Based on Virtual Synchronizer under Weak Grid
Authors: Li Yinghui , Chen Jianan , Wang Xiaohuan , Zhang Xudong , Zhao Xiaojun
Published: September 2022

The power grid has the characteristics of a weak grid with an increase in new energy penetration in the power system. Power electronic-based renewable generation brings issues that weaken the entire system, including the loss of inertia. Low inertia and weak damping cause system oscillation. Virtual synchronous generator (VSG) technology gives power electronic equipment inertia-support capability but increases the complexity of control system parameter design. Many researchers have studied the design method of VSG considering the frequency disturbance of the power grid. The traditional VSG parameter design method ignores the influence of source-side and grid-side fluctuations on the transient stability of the system, resulting in the difference between the actual dynamic and static indicators and the design indicators of VSG in a weak grid. This paper analyzes a small-signal model based on power fluctuations and frequency fluctuations and proposes a control parameter design method that combines the influence of grid impedance to ensure the dynamic stability of the system under a weak power grid. The simulation and experimental results verify the correctness and feasibility of the control method.
Impact of an E-Highway on the Required Battery Capacities and Charging Infrastructure for Cargo Transport with E-Trucks on the Basis of a Real Use Case
Authors: Netzer Lukas , Wöss David , Märzinger Thomas , Müller Werner , Pröll Tobias
Published: September 2022

With the goal of reducing greenhouse gas emissions, the logistics sector is increasingly coming into focus. While increasing electrification is taking place in the road transport sector, the numbers in heavy-goods transport have so far been vanishingly small. Payload limitations, high investment costs, and charging times make it difficult for logistics companies to think about a conversion. An e-highway on Austria’s highways could provide an approach to counter these problems. Based on route data of an entire truck fleet in the construction logistics sector and by creating a model with Openrouteservice and MATLAB, calculations are carried out to show the savings potential of required battery capacities and charging infrastructure. The results show a high potential for reducing battery capacities and the required charging infrastructure at the locations approached. The results show high reduction potential, keeping the average required capacities in all scenarios below 350 kWh. Having a higher-powered e-highway of 150 kW nets slightly better results, but a major effect can still be achieved with a power of 60 kW. The cost reduction potential related to batteries and charging stations is up to 65% for individual scenarios. Thus, the result of this work primarily aims at presenting the advantages of a potential e-highway for logistics companies operating on Austria’s roads but can also be considered from the regulatory side when it comes to incentivizing sustainable logistics solutions from the political side.
Triggering Shock Wave Positions by Patterned Energy Deposition
Authors: Andrews Philip , Lax Philip , Leonov Sergey
Published: September 2022

The problem considered in this work is shock wave (SW) positioning control in shock-dominated flows. Experiments are conducted to investigate the triggering effect of patterned near-surface electrical discharges on SW reflection from plane walls. In the wind tunnel, M=4, P0 = 4 bar, a solid wedge SW generator is mounted on the upper wall. Q-DC filamentary electrical discharges were arranged on the opposite wall, so that the SW from the wedge impinged on the plasma filaments that are arranged flow-wise in either a row of three or a single central filament. Within the supersonic flow, narrow subsonic areas are actuated by electrical discharge thermal deposition, resulting in pressure redistribution, which, in turn, relocates the reflection of impinging SW to a predefined position. Mie scattering, schlieren imaging, and wall pressure measurements are used to explore the details of plasma-SW interaction. Using Mie scattering, the three-dimensional shape of the SW structure is mapped both before and after electrical discharge activation. Plasma-based triggering mechanisms are described in terms of the physical principles of flow control and a criterion for determining the effectiveness of the flowfield control.
Experimental Study on Hydraulic Fracture Initiation and Propagation in Hydrated Shale
Authors: Duan Guifu , Mou Jianye , Zou Yushi , Gao Budong , Yang Lin , He Yufei
Published: September 2022

Shale reservoirs contain a certain amount of clay minerals, which can hydrate through imbibition when in contact with various water-based fluids during drilling and completion. Shale hydration can lead to structural changes in the shale such as the expansion of bedding planes and propagation of microfractures, consequently affecting the initiation and propagation of hydraulic fractures. However, the effect of shale hydration under confining pressure on hydraulic fracture propagation and stimulation effect is still unclear. To this end, a novel experimental method integrating shale hydration and hydraulic fracturing was proposed based on the laboratory triaxial hydraulic fracturing simulation system. This method enables a more realistic simulation of shale hydration and hydraulic fracturing process happening in downhole conditions. The experimental results show that under simulated reservoir conditions, water imbibition increases over time with the imbibition rate reaching its peak within 24 h. The breakdown pressure, number of fractures, and complexity of fractures are positively correlated with imbibition time. The increase in fracture complexity could be attributed to the increase in the number of fractures. In contrast, imbibition pressure (injection pressure for imbibition) has little influence on water imbibition. For specimens under different imbibition pressure, the breakdown pressure and the number of fractures are close, and the complexity of fractures does not change prominently; all are T-shaped fractures. It is believed that the closure of microfractures under confining pressure caused by hydration is the main reason for the increase in breakdown pressure. Higher breakdown pressure means higher net pressure in the wellbore, which facilitates fracture initiation where the breakdown pressure is higher. Therefore, shale hydration is conducive to the initiation of multiple fractures, thus increasing the number and complexity of fractures.
Mechanisms for Tax Regulation of CO2-Equivalent Emissions
Authors: Borodin Alex , Zaitsev Vladislav , Mamedov Zahid F. , Panaedova Galina , Kulikov Andrey
Published: September 2022

The aim of the work is to develop a mechanism for cross-border carbon regulation for countries importing products to the EU, which will equally allow importing countries to fulfill the conditions of the Carbon Border Adjustment Mechanism (CBAM), encourage manufacturers to reduce CO2 emissions, and also provide importing countries with opportunities to replenish their budget by introducing paid emission quotas greenhouse gases. The work makes a significant contribution to stimulating the reduction of CO2 emissions by producers due to the proposed tax mechanism and preventing the leakage of greenhouse gases on the territory of third countries according to the CBAM policy. The EU evaluates double taxation, so if a carbon tax has been withdrawn in the territory of the exporting country, then such a tax will not be levied again in the EU. All this involves stimulating exporting countries by creating their own taxation systems, which will have international qualifications and be recognized by countries around the world. When choosing a taxation mechanism, it is important to choose the specifics for visiting group gases. The study was conducted on the basis of methods of comparison, modeling, analysis and deduction.
Context-Aware Policy Analysis for Distributed Usage Control
Authors: Gil Gonzalo , Arnaiz Aitor , Higuero Mariví , Diez Francisco Javier , Jacob Eduardo
Published: September 2022

To boost data spaces and benefit from the great opportunities that they present, data sovereignty must be provided by Distributed Usage Control (DUC). Assuming that DUC will be managed by implementing and enforcing policies, notable efforts have already been undertaken in the context of Access Control (AC) regarding policy analysis due to the impact of low-quality policies on security. In this regard, this paper proposes that policy analysis in the DUC context should be understood as an extension of the AC, which is further affected by other challenging features, chief among which are context-aware control and extended control through action requirements. This paper presents a novel Context-Aware Policy Analysis (CAPA) algorithm for detecting inconsistencies and redundancies for DUC policies by supporting a large set of heterogeneous conditions. In this regard, the dependent relationship of conditions is formulated which will lead to more efficient conflict detection. By implementing this concept, a novel tree structure that combines a resource and a policy structure is presented to search for and compare relevant rules from policies. Built on the tree structure and through the formalization of rule conflicts, CAPA is developed and the security and performance it provides is tested in a wind energy use case.
Future Research Tendencies and Possibilities of Using Cogeneration Applications of Solar Air Heaters: A Bibliometric Analysis
Authors: Ifrim Visarion Cătălin , Milici Laurențiu Dan , Atănăsoae Pavel , Irimia Daniela , Pentiuc Radu Dumitru
Published: September 2022

Solar air heater systems are equipment that uses energy captured directly from the sun to heat an existing airflow through the module. The technology to operate these systems is based on clean, renewable and free energy. Solar air heaters absorb thermal energy from the sun using an ab-sorption surface and achieve a transfer of heat from the absorption surface to the air flow supplied by one or two fans. This type of equipment can be used for space heating, drying, or ventilation processes. In addition, the equipment is capable of operating in cogeneration with other systems, e.g., preheating the air used for drying wood, preheating the air used to heat industrial premises, or preheating the water used in different heating systems. This scientific work is meant to reveal the current research context and the future opportunities in the case of cogeneration applications of solar air heaters, which are analyzed in light of their actual evolving dynamics. On this basis, we highlight expectations regarding the main problems that the regenerable energy is currently facing in this specific research and development environment as well as focusing our direction on the eventual solutions that are considered in the present and on their shortcomings in the future with evolved necessities.
Correction Method for Logging Curves in Clay-Rich Tight Glutenite Reservoir: Upper Wuerhe Formation in Mahu Oilfield, China
Authors: Wang Linsheng , Xiong Qian , Jiang Qingping , Wang Zhifeng , Qiu Zigang , Liu Kai , Kong Chuixian , Liu Canhua , Zhang Xiaoli
Published: September 2022

Mahu Oilfield is the largest tight glutenite oilfield in the world, and the upper Wuerhe formation is an important succeeding exploration horizon. However, the upper Wuerhe formation in the Mahu 1 zone has a high clay content, which can lead to serious wellbore collapse. Meanwhile, the horizontal well logging is not corrected. These factors lead to the inconsistency between the logging interpretation results and the oil test results. The interpretation precision of the clay content, water saturation, and porosity, which are crucial to reservoir evaluation, is very low. In this paper, a workflow of logging curve correction using multiple methods is proposed. The multiple linear fitting is used to correct boreholes, and then histogram frequency distribution matching is used to standardize multi-well logging curves. Finally, the optimization method is used to build a volume model based on skeleton analysis, and the results are calibrated with core analysis results. Horizontal well density logs are corrected using adjacent vertical well logs. The interpretation results of clay content, water saturation, and porosity with high precision are obtained. The reservoir interpretation is more in line with the oil test results than the original interpretation. The clay content distribution is more reasonable.
Assessment of an Adaptive Efficient Thermal/Electric Skipping Control Strategy for the Management of a Parallel Plug-in Hybrid Electric Vehicle
Authors: Bellis Vincenzo De , Piras Marco , Malfi Enrica
Published: September 2022

In the current scenario, where environmental concern determines the evolution of passenger cars, hybrid electric vehicles (HEV) represent a hub in the automotive sector to reach net-zero CO2 emissions. To fully exploit the energy conversion potential of advanced powertrains, proper energy management strategies are mandatory. In this work, a simulation study is presented, aiming at developing a new control strategy for a P3 parallel plug-in HEV (PHEV). The simulation model is built on MATLAB/Simulink. The proposed strategy is based on an alternative utilization of the thermal engine and electric motor to provide the vehicle power demand (efficient thermal/electric skipping strategy (ETESS)). An adaptive function is then introduced to develop a charge-blended control strategy. Fuel consumption along different driving cycles is evaluated by applying the novel adaptive-ETESS (A-ETESS). To have a proper comparison, the same adaptive function is built on the equivalent consumption minimization strategy (ECMS). Processor-in-the-loop (PIL) simulations are performed to benchmark the A-ETESS. Simulation results highlighted that the proposed strategy provides for a fuel economy similar to ECMS (worse of about 2.5% on average) and a computational effort reduced by 99% on average, opening the possibility of real-time on-vehicle applications.
Predictive Controller for Refrigeration Systems Aimed to Electrical Load Shifting and Energy Storage
Authors: Di Mattia Edoardo , Gambarotta Agostino , Marzi Emanuela , Morini Mirko , Saletti Costanza
Published: September 2022

The need to reduce greenhouse gas emissions is leading to an increase in the use of renewable energy sources. Due to the aleatory nature of these sources, to prevent grid imbalances, smart management of the entire system is required. Industrial refrigeration systems represent a source of flexibility in this context: being large electricity consumers, they can allow large-load shifting by varying separator levels or storing surplus energy in the products and thus balancing renewable electricity production. The work aims to model and control an industrial refrigeration system used for freezing food by applying the Model Predictive Control technique. The controller was developed in Matlab® and implemented in a Model-in-the-Loop environment. Two control objectives are proposed: the first aims to minimize total energy consumption, while the second also focuses on utilizing the maximum amount of renewable energy. The results show that the innovative controller allows energy savings and better exploitation of the available renewable electricity, with a 4.5% increase in its use, compared to traditional control methods. Since the proposed software solution is rapidly applicable without the need to modify the plant with additional hardware, its uptake can contribute to grid stability and renewable energy exploitation.
COVID-19 and Peace in Conflict-Affected Areas
Authors: Ossai Emmanuel Chiwetalu
Published: September 2022

The relationship between COVID-19 and peace has been considered from a variety of perspectives. In addition, different empirical studies on the link between the pandemic and peace in conflict-affected areas exist. However, little work has been performed on examining these studies to highlight key findings on the theme of COVID-19 and peace in conflict-affected areas. A conflict-affected area is a country, or part of a country, where widespread violence or armed conflict was present when COVID-19 emerged in December 2019, or that was transitioning from recent armed conflict to peace by the time the disease arose. What do we know, so far, about how peace has been affected by the COVID-19 pandemic in conflict-affected areas? To address this question, this paper begins by recognizing the multidimensionality of peace and clarifying that the main aspects of peace in conflict-affected areas being considered in the article are relations between conflict parties, peace efforts, and peace processes. Afterwards, the paper discusses existing evidence regarding the impact of COVID-19 and state responses to it on these components of peace in conflict-affected areas. The conflict-affected areas considered include Afghanistan, Colombia, Iraq, Israel-Palestine, Libya, Myanmar, Nigeria, South Sudan, Syria, the Philippines, Yemen, and other zones. The central finding of the article is that the existing studies on COVID-19 and peace in conflict-affected areas present mixed findings. On the one hand, the virus generated opportunities for cooperation between conflict parties in some cases, such as in the West Bank and Gaza Strip of Israel-Palestine. However, on the other hand, it created conditions that enabled conflict and impeded peace efforts and processes in many or most conflict-affected areas. The paper explains that two factors that determined how the disease affected peace in conflict-affected and non-conflict-affected areas are the pre-COVID-19 political and socio-economic conditions in an area, and how state and non-state actors responded to the pandemic. The article closes with a summary of the discussion and identification of its major limitations.
Psychosocial Determinants of Recreational Activity within Urban Green Spaces during the COVID-19 Pandemic in Poland
Authors: Wajchman-Świtalska Sandra , Grabowska-Chenczke Olga , Woźniak Marcin , Bałaj Bibianna
Published: September 2022

Recreational activity undertaken within urban green spaces (UGS) is an action that could be self-governed and self-regulated by a given person under the pressure of COVID-19. We aimed to identify the factors that induce or reduce the frequency of recreational activity during the COVID-19 pandemic. These factors were explored among two distinct fields: (1) demographic variables and (2) stress-coping strategies. The former is associated with a body of literature on socioeconomic determinants of physical activity. The latter is derived from psychological studies on coping responses to problems. In this paper, we present an interdisciplinary perspective on human recreational activity during the pandemic. We collected information on stress-coping strategies and the patterns of urban green recreation among 376 prime-age Polish adults with different places of residence. We observed that people who use forests daily had higher scores of acceptance as a coping strategy than people using green spaces only on weekends. As choosing acceptance as a coping strategy is typical for those who consider their situation to be irreversible, green recreation may help to acclimate individuals to stressful situations that cannot be easily changed or controlled, which is the case for the pandemic. Moreover, we found that active coping, as well as avoidant coping, were predictors of increased use of green spaces during the pandemic. This conclusion affirms that green recreation as a form of reducing COVID-19-induced stress is associated with the dual nature of coping (active and avoidant). Further research is necessary to better understand of motivation to use urban green recreation, especially when practiced as a method of strengthening mental health.