bluuebunny/crossref_metadata_2025 huggingface dataset:
A Comparative Study of Problem-Based Learning and Traditional Approaches in College English Classrooms: Analyzing Pedagogical Behaviors Via Classroom Observation
Authors: Tang Shifang , Long Manli , Tong Fuhui , Wang Zhuoying , Zhang Henan , Sutton-Jones Kara L.
Published: June 2020

In this study, we described and compared an English as a foreign language (EFL) teacher’s pedagogical behaviors in traditional and problem-based learning (PBL) classroom settings in a Chinese university. In spring 2019, we collected six 45-min videos, three in each condition, covering three modules: (a) warm-up and vocabulary, (b) essay structure, and (c) writing. The analyses of the teacher’s pedagogical behaviors and her interaction with students indicated that the instructor spent most of the instructional time delivering higher-order thinking content in both traditional and PBL classes. The teacher’s activity structure influenced students’ communication mode. Although the instructor provided students with more group discussion activities in the PBL classroom, lecturing was observed to be the primary delivery method in both classes. These results suggest that the application of PBL strategies in the EFL classroom did not significantly restructure the teacher’s pedagogical behaviors, and thus, failed to achieve the goal of providing students with more opportunities for improving their expressive English language proficiency. These findings underscore the need to develop an effective PBL-related curriculum and professional development opportunities for EFL teachers to effectively implement the PBL approach in the classroom.
The Effect of Taxation on Investment Demand in the Real Estate Market: The Italian Experience
Authors: Manganelli Benedetto , Morano Pierluigi , Rosato Paolo , De Paola Pierfrancesco
Published: June 2020

This study investigates the effect that property taxation has on investment in the real estate market. There is a close relationship between investments in the real estate market and taxes, local communities, public policies and economic development. The analysis was developed with reference to the Italian real estate market and its tax regime. In Italy, taxation on real estate affects possession, transfers and income. These three tax rates vary according to the subjects who exchange assets and manage them, to the intended use of the real estate property and to the options for choosing the type of tax regime permitted by law. On the basis of these parameters, a financial analysis of real estate investment is constructed and simulated in order to understand to which types of taxation investment is most sensitive. The results showed that a change in income taxation can have an important effect on the investment choice. This evidence may also suggest fiscal policy actions aimed at stimulating the real estate market.
Asymmetry in Charge Transfer Pathways Caused by Pigment–Protein Interactions in the Photosystem II Reaction Center Complex
Authors: Sato Yoshihiro , Sicotte Danielle
Published: June 2020

This article discusses the photoinduced charge transfer (CT) kinetics within the reaction center complex of photosystem II (PSII RC). The PSII RC exhibits a structural symmetry in its arrangement of pigments forming two prominent branches, D1 and D2. Despite this symmetry, the CT has been observed to occur exclusively in the D1 branch. The mechanism to realize such functional asymmetry is yet to be understood. To approach this matter, we applied the theoretical tight-binding model of pigment excitations and simulated CT dynamics based upon the framework of an open quantum system. This simulation used a recently developed method of computation based on the quasi-adiabatic propagator path integral. A quantum CT state is found to be dynamically active when its site energy is resonant with the exciton energies of the PSII RC, regardless of the excitonic landscape we utilized. Through our investigation, it was found that the relative displacement between the local molecular energy levels of pigments can play a crucial role in realizing this resonance and therefore greatly affects the CT asymmetry in the PSII RC. Using this mechanism phenomenologically, we demonstrate that a near 100-to-1 ratio of reduction between the pheophytins in the D1 and D2 branches can be realized at both 77 K and 300 K. Our results indicate that the chlorophyll Chl D 1 is the most active precursor of the primary charge separation in the D1 branch and that the reduction of the pheophytins can occur within pico-seconds. Additionally, a broad resonance of the active CT state implies that a large static disorder observed in the CT state originates in the fluctuations of the relative displacements between the local molecular energy levels of the pigments in the PSII RC.
Sustainable Synthesis of Epoxidized Cynara C. Seed Oil
Authors: Turco Rosa , Di Serio Martino
Published: June 2020

The use of non-edible vegetable oils to produce oleochemicals has been attracting more attention in recent years. Cardoon seed oil, derived from the Cynara C. plant, growing in marginal and contaminated lands, represents a non-edible alternative to soybean oil to obtain plasticizers through epoxidation reaction. The use of hydrogen peroxide as oxidant and in the presence of a heterogeneous catalyst allows overcoming the limits of epoxidation with peracids. γ-alumina has been shown to have an active catalyst epoxidation reaction with hydrogen peroxide, mainly using acetonitrile as solvent. However, the use of acetonitrile as solvent is widely debated due to its hazardous character and health issues. For these reasons, the influence of solvent on the reaction was studied in this work to find a more environmentally friendly and stable solvent. The study showed that the epoxidation reaction takes place also in the absence of solvent although with lower selectivity. The type of solvent influences both the epoxidation and decomposition reactions of hydrogen peroxide. γ-valerolactone was found to be the most promising solvent for cardoon oil epoxidation reaction. This finding represents a noteworthy novelty in the field of epoxidation of vegetable oils with hydrogen peroxide, opening the way to greener and cleaner process. Finally, an optimization study showed that the most effective molar ratio between hydrogen peroxide and double bonds for better selectivity was 4.5 and the need to use the highest possible initial concentration of hydrogen peroxide (approximately 60 wt. %).
Enhanced Heterogeneous Photodegradation of Organic Pollutants by a Visible Light Harvesting CoO@meso–CN@MoS2 Nanocomposites
Authors: Chen Linjer , Nguyen Thanh Binh , Lin Yi-Li , Wu Chung-Hsin , Chang Jih-Hsing , Chen Chiu-Wen , Dong Cheng-Di
Published: June 2020

Developing simple and effective synthetic strategies regarding the formation of heterostructure photocatalytic semiconductors remains an intense challenge in research matters. Uniform heterostructure cobalt oxide@meso–CN@MoS2 (CoO@meso–CN@MoS2) photocatalyst exhibits excellent photocatalytic redox performance for pollutant degradation under visible light. By adjusting the weight ratio of CoO@meso–CN and MoS2, we fabricated a CoO@meso–CN@MoS2 heterostructure photocatalyst, and the established heterostructure between CoO@meso–CN and MoS2 was indicated by various physicochemical and morphological characterizations. The photocatalytic response to the fabricated hybrid was determined by rodamine B (RhB), methylene blue (MB), and congo red (CR) degradation in aqueous solution under visible light, and the nanocomposites with a slight content consisting of CoO@meso–CN achieved better catalysis than pure MoS2. This finding confirmed the propriety of this heterostructure as a valuable photocatalyst. The experimental results demonstrated that the apparent reaction rate constant of the 3 wt% CoO@meso–CN modified MoS2 was about two times higher than that of pure MoS2. The present work serves as a new approach for designing highly efficient visible light-induced heterostructure-based photocatalysts for environmental applications in the future.
Sustainable Option for Hydrogen Production: Mechanistic Study of the Interaction between Cobalt Pincer Complexes and Ammonia Borane
Authors: Li Yan , Tsang Chi-Wing , Chan Eve Man Hin , Wong Eugene Yin Cheung , Ho Danny Chi Kuen , Lu Xiao-Ying , Liang Changhai
Published: June 2020

The mechanism of the solvolysis/hydrolysis of ammonia borane by iridium (Ir), cobalt (Co), iron (Fe) and ruthenium (Ru) complexes with various PNP ligands has been revisited using density functional theory (DFT). The approach of ammonia borane (NH3BH3) to the metal center has been tested on three different possible mechanisms, namely, the stepwise, concerted and proton transfer mechanism. It was found that the theoretical analyses correlate with the experimental results very well, with the activities of the iridium complexes with different PNP ligands following the order: (tBu)2P > (iPr)2P > (Ph)2P through the concerted mechanism. The reaction barriers of the rate-determining steps for the dehydrogenation of ammonia borane catalyzed by the active species [(tBu)2PNP-IrH] (Complex I-8), are found to be 19.3 kcal/mol (stepwise), 15.2 kcal/mol (concerted) and 26.8 kcal/mol (proton transfer), respectively. Thus, the concerted mechanism is the more kinetically favorable pathway. It is interesting to find that stable (tBu)2PNP Co-H2O and (tBu)2PNP Co-NH3 chelation products exist, which could stabilize the active I-8 species during the hydrolysis reaction cycle. The use of more sterically hindered and electron-donating PNP ligands such as (adamantyl)2P- provides similar activity as the t-butyl analogue. This research provides insights into the design of efficient cobalt catalysts instead of using precious and noble metal, which could benefit the development of a more sustainable hydrogen economy.
Characterization of Sulfated SnO2-ZrO2 Catalysts and Their Catalytic Performance on the Tert-Butylation of Phenol
Authors: Marlowe Justin , Acharya Shreyas , Zuber Adam , Tsilomelekis George
Published: June 2020

Understanding the catalytic behavior of sulfated metal oxides has been the topic of several research studies in the past few decades. Their apparent super-acidic behavior has been correlated with the molecular structure of the surface sulfate species. Herein, we couple FTIR and Raman spectroscopies to study the molecular structural evolution of surface sulfate species on mixed metal hydroxides as well as calcined oxides. We show that on the surface of hydroxides, monodentate and possibly bidentate species are dominant, while for SnO2-rich samples, clusters of polymeric sulfate species may also be present. After calcination, sulfate species bind strongly on the surface of mixed oxides, and different configurations can be seen with a range of S=O functionalities of varying strength. Through comparison of the catalytic performance of all sulfate oxides in the tert-butylation of phenol, it was found that SnO2-rich samples show high TBA conversion, with monoalkylated phenols as the primary product.
Effect of Laser Processing on Surface Properties of Additively Manufactured 18-Percent Nickel Maraging Steel Parts
Authors: Černašėjus Olegas , Škamat Jelena , Markovič Vladislav , Višniakov Nikolaj , Indrišiūnas Simonas
Published: June 2020

In the present work, the experimental study on laser processing of additively manufactured (AM) maraging steel part surface was conducted. Nanosecond pulsed laser at ablation mode was used for surface modification in oxidizing atmosphere. The morphology, roughness, elemental and phase composition, microhardness and tribological properties of the processed surfaces were investigated. The obtained results revealed that pulsed laser processing under the ablation mode in air allows obtaining modified surface with uniform micro-texture and insignificant residual undulation, providing 3 times lower roughness as compared with the as-manufactured AM part. The intensive oxidation of surface during laser processing results in formation of the significant oxides amount, which can be controlled by scanning speed. Due to the presence of the oxide phase (such as Fe2CoO4 and Ti0.11Co0.89O0.99), the hardness and wear resistance of the surface were significantly improved, up to 40% and 17 times, respectively. The strong correlation between the roughness parameter Ra and mass loss during the tribological test testifies the significant role of the obtained morphology for the wear resistance of the surface.
Deposition of Multicomponent AlTiCrMoN Protective Coatings for Metal Cutting Applications
Authors: Chang Yin-Yu , Chuang Chih-Cheng
Published: June 2020

The high potential of the protective coatings for metal machining applications using the physical vapor deposition (PVD) processes is one to be valued, and will accelerate development of the multicomponent coating design and increase the cutting efficiency. In this study, nanostructured AlTiCrMoN coatings in a multilayered structure were fabricated using cathodic-arc deposition (CAD). Controlling the cathode current of both CrMo and AlTi alloy targets in a nitrogen environment, multilayered AlTiN/CrMoN coatings were deposited. The AlTiN and AlTiN/CrMoN multilayered coatings exhibit a face-centered cubic (fcc) structure with columnar morphologies. The highest hardness of 35.6 ± 1.5 GPa was obtained for the AlTiN coating; however, the H3/E*2 and H/E* values were the lowest (0.124 and 0.059, respectively). The multilayered AlTiN/CrMoN coatings possessed higher H3/E*2 and H/E* values of up to 0.157 and 0.071, respectively. The present study investigated the cutting performance of end mills in the milling of SUS316L stainless steel. The cutting performance was evaluated in terms of cutting length and tool wear. Because of high resistance to adhesive and abrasive wear, the end mills coated with multilayered AlTiN/CrMoN showed less flank wear than monolithic AlTiN. The introduction of CrMoN sublayers improved the cutting tool life of AlTiN.
Effect of Zirconium Doping on Electrical Properties of Aluminum Oxide Dielectric Layer by Spin Coating Method with Low Temperature Preparation
Authors: Zhou Yue , Liang Zhihao , Yao Rihui , Zuo Wencai , Zhou Shangxiong , Zhu Zhennan , Wang Yiping , Qiu Tian , Ning Honglong , Peng Junbiao
Published: June 2020

In recent years, significant efforts have been devoted to the research and development of spin-coated Al2O3 thin films, due to their large band gaps, high breakdown voltage and stability at high annealing temperature. However, as the alumina precursor has a large surface energy, substrates need to be treated by plasma before spin coating. Therefore, to avoid the expensive and process-complicated plasma treatment, we incorporated zirconium nitrate into the aluminum nitrate solution to decrease the surface energy of the precursor which improve the spreadability. Then, the electrical performances and the surface morphologies of the films were measured. For comparison, the pure Al2O3 films with plasma treatments were also prepared. As a result, after low temperature annealing (200 °C), the relative dielectric constant of Zr–AlOx spin-coated thin-film MIM (Metal-Insulator-Metal) devices can reach 12 and the leakage current density is not higher than 7.78 × 10−8 A/cm2 @ 1 MV/cm when the concentration of zirconium nitrate is 0.05 mol/L. The Aluminum oxide film prepared by zirconium doping has higher stability and better electrical properties than the pure films with plasma treatments and high performance can be attained under low-temperature annealing, which shows its potential application in printing and flexible electronic devices.
Microstructures and Mechanical Properties of Nanocrystalline AZ31 Magnesium Alloy Powders with Submicron TiB2 Additions Prepared by Mechanical Milling
Authors: Zhou Haiping , Zhang Chengcai , Han Baokun , Qiu Jianfeng , Qin Shengxue , Gao Kuidong , Liu Jie , Sun Shuai , Zhang Hongbin
Published: June 2020

In this work, nanocrystalline AZ31 magnesium alloy powders, reinforced by submicron TiB2 particles, were prepared via mechanical milling. It was found that TiB2 particles stimulated the fracture and welding of AZ31/TiB2 powders, leading to the acceleration of the milling process. Meanwhile, the TiB2 particles were refined to submicron-scale size during the milling process, and their distribution was uniform in the Mg matrix. In addition, the matrix was significantly refined during the milling process, which was also accelerated by the TiB2 particles. The formation of grain boundary segregation layers also led to the weakened TiB2 peaks in the XRD patterns during the mechanical milling. The grain sizes of AZ31–2.5 wt % TiB2, AZ31–5 wt % TiB2 and AZ31–10 wt % TiB2 powders were refined to 53 nm, 37 nm and 23 nm, respectively, after milling for 110 h. Under the combined effect of the nanocrystalline matrix and the well-dispersed submicron TiB2 particles, the AZ31/TiB2 composites exhibited excellent micro-hardness. For the AZ31–10 wt % TiB2 composite, the micro-hardness was enhanced to 153 HV0.5.
Effect of Deposition Power on the Thermoelectric Performance of Bismuth Telluride Prepared by RF Sputtering
Authors: Zang Kai-Yan , Hu Er-Tao , Wang Zheng-Yong , Tu Hua-Tian , Zheng Yu-Xiang , Wang Song-You , Zhao Hai-Bin , Yang Yue-Mei , Lee Young-Pak , Chen Liang-Yao
Published: June 2020

In this work, we present a simple method to improve the thermoelectric performance of the RF sputtered bismuth telluride films by raising the power of deposition. The as-deposited samples synthesized under different powers were investigated and compared. It shows that the films prepared under relatively higher power conditions exhibit much higher electrical conductivity to result in a greater power factor accompanied with a minor drop in the Seebeck coefficients. A relationship is established between the improvement in thermoelectric performance and the decrease in crystallinity, which might also reduce the thermal conductivity. A maximum power factor of 5.65 × 10−4 W·m−1·K−2 at 470 K is obtained for the sample deposited under 50 W with its Seebeck coefficient being −105 μV/K. The temperature-dependent behaviors of the samples are also looked into and discussed. This work might offer an in-situ and cost-effective approach to improve the performance of thermoelectric materials.
Mechanisms of Grain Structure Evolution in a Quenched Medium Carbon Steel during Warm Deformation
Authors: Panov Dmitriy , Dedyulina Olga , Shaysultanov Dmitriy , Stepanov Nikita , Zherebtsov Sergey , Salishchev Gennady
Published: June 2020

The as-quenched medium-carbon low-alloy Fe-0.36wt.%C-1wt.%Cr steel was subjected to warm deformation via uniaxial compression at temperatures of 400–700 °C and strain rates of 10−4–10−2 s−1. At low temperatures (400–550 °C), the microstructure evolution was mainly associated with dynamic recovery with the value of activation energy of 140 ± 35 kJ/mol. At higher temperatures (600–700 °C), dynamic recrystallization was developed, and activation energy in this case was 243 ± 15 kJ/mol. The presence of nanoscale carbide particles in the structure at temperatures of 400–600 °C resulted in the appearance of threshold stresses. A two-component <001>//compression direction (CD) and <111>//CD deformation texture was formed during deformation. Deformation at the low temperatures resulted in the formation of elongated ferritic grains separated mainly by high-angle boundaries (HAB) with a strong <001>//CD texture. The grains with the <111>//CD orientation were wider in comparison with those with the <001>//CD orientation. The development of substructure in the form of low-angle boundaries (LAB) networks was also observed in the <111>//CD grains. The development of dynamic recrystallization restricted the texture formation. The processing map for warm deformation of the 0.36C-1Cr steel was constructed.
A Recurrent Exertional Syncope and Sudden Cardiac Arrest in a Young Athlete with Known Pathogenic p.Arg420Gln Variant in the RYR2 Gene
Authors: Stępień-Wojno Małgorzata , Ponińska Joanna , Biernacka Elżbieta , Foss-Nieradko Bogna , Chwyczko Tomasz , Syska Paweł , Płoski Rafał , Bilińska Zofia
Published: June 2020

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is one of causes of sudden cardiac death in the young, especially in athletes. Diagnosis of CPVT may be difficult since all cardiological examinations performed at rest are usually normal, and exercise stress test-induced ventricular tachycardia is not commonly present. The identification of a pathogenic mutation in RYR2 or CASQ2 is diagnostic in CPVT. We report on a 20-year-old athlete who survived two sudden cardiac arrests during swimming. Moreover, he suffered repeated syncopal spells on exercise. The diagnosis was made only following genetic testing using a multi-gene panel, and the p.Arg420Gln RYR2 variant was identified. We present diagnostic and therapeutic issues in this young athlete with CPVT.
Plasma Osteopontin Levels is Associated with Biochemical Markers of Kidney Injury in Patients with Leptospirosis
Authors: Chagan-Yasutan Haorile , Hanan Firmanto , Niki Toshiro , Bai Gaowa , Ashino Yugo , Egawa Shinichi , Telan Elizabeth Freda O. , Hattori Toshio
Published: June 2020

: Leptospirosis becomes severe, with a fatality rate of >10%, and manifests as severe lung injury accompanied by acute kidney injury. Using urine and blood samples of 112 patients with leptospirosis, osteopontin (OPN), galectin-9 (Gal-9) and other kidney-related biomarkers were measured to understand the pathological and diagnostic roles of OPN and Gal-9 in leptospirosis. Plasma levels of full-length (FL)-OPN (pFL-OPN) (p < 0.0001), pFL-Gal-9(p < 0.0001) and thrombin-cleaved OPN (p < 0.01) were significantly higher in patients with leptospirosis than in healthy controls (n = 30), as were levels of several indicators of renal toxicity: serum cystatin C (p < 0.0001), urine N-acetyl-β-glucosaminidase (NAG)/creatinine (p < 0.05), and urine clusterin/creatinine (p < 0.05). pFL-Gal-9 levels were negatively correlated with pFL-OPN levels (r = −0.24, p < 0.05). pFL-OPN levels were positively correlated with serum cystatin C (r = 0.41, p < 0.0001), urine NAG/creatinine (r = 0.35, p < 0.001), urine clusterin/creatinine (r = 0.33, p < 0.01), and urine cystatin C/creatinine (r = 0.33, p < 0.05) levels. In a group of patients with abnormally high creatinine levels, significantly higher levels of serum cystatin C (p < 0.0001) and pFL-OPN (p < 0.001) were observed. Our results demonstrate that pFL-OPN reflect kidney injury among patients with leptospirosis.
Generalized Entropies, Variance and Applications
Authors: Toomaj Abdolsaeed , Di Crescenzo Antonio
Published: June 2020

The generalized cumulative residual entropy is a recently defined dispersion measure. In this paper, we obtain some further results for such a measure, in relation to the generalized cumulative residual entropy and the variance of random lifetimes. We show that it has an intimate connection with the non-homogeneous Poisson process. We also get new expressions, bounds and stochastic comparisons involving such measures. Moreover, the dynamic version of the mentioned notions is studied through the residual lifetimes and suitable aging notions. In this framework we achieve some findings of interest in reliability theory, such as a characterization for the exponential distribution, various results on k-out-of-n systems, and a connection to the excess wealth order. We also obtain similar results for the generalized cumulative entropy, which is a dual measure to the generalized cumulative residual entropy.
Silanes for Building Protection: A Case Study in Systems Thinking Approach to Materials Science Education
Authors: Ciriminna Rosaria , Albo Yael , Fidalgo Alexandra , Ilharco Laura , Pagliaro Mario
Published: June 2020

Silanes, and organically modified silanes in particular, are commercially used to protect the built environment from deterioration and, in indoor applications, to minimize water vapor condensation and microbiological contamination. Increasing their uptake, we argue in this study, includes the need to adopt a systems-thinking view of this green chemistry technology. After identifying the key advantages of these coatings, we highlight important educational consequences to undergraduate courses and doctoral programs in chemistry and materials science which are common in many research topics, well beyond nanocoating science and technology.
Mechanisms of Moral Disengagement Used to Justify School Violence in Sicilian Primary School
Authors: Méndez Inmaculada , Liccardi Giuseppa , Ruiz-Esteban Cecilia
Published: June 2020

This study investigated the mechanisms of moral disengagement most commonly used to justify school violence in Sicilian primary school. The main objective of this study was to analyze the mechanisms of moral disengagement that are set in motion by those involved in situations of school violence (victims, aggressors, and bystanders) in Sicilian primary school. Likewise, the differences by gender and age are investigated. A total of 113 subjects in primary school were recruited (56.6% girls). The ages ranged from 8 to 11 (M = 9.56, SD = 0.99). The first scale used was the Bullying Inventory by Olweus (1993) in the Italian translation by Genta, Menesini, Fonzi, Costabile, and Smith (1996) and the questionnaire on moral disengagement developed by Caprara, Barbaranelli, Vicino, and Bandura (1996) is also used. The regression analysis showed that the sociodemographic variables and the mechanisms of moral disengagement are different depending on a person’s role (aggressor, victim, or bystander). Moral justification predicted the role of victim in school violence, dehumanization predicted the role of the aggressor (and gender), and the disclosure of responsibility (and dehumanization) predicted the role of the bystander in school violence. The conclusions of this study will facilitate the prevention of school violence, for example, by promoting social integration and minimizing situations of school violence (emphasizing morality, ethics, etc.), thereby establishing balanced and satisfactory interpersonal relationships.
Outage Performance of Power Beacon-Aided Multi-Hop Cooperative Cognitive Radio Protocol Under Constraint of Interference and Hardware Noises
Authors: Minh Nam Pham , Trung Duy Tran , Van Ca Phan , Ngoc Son Pham , Hoang An Ngo
Published: June 2020

In this paper, we evaluate end-to-end outage probability of a multi-hop decode-and-forward relaying protocol in underlay cognitive radio network. In the proposed protocol, named COOP, secondary nodes including source and relays have to harvest radio-frequency energy from multiple secondary power beacons, and adjust their transmit power, follows a pre-determined interference threshold given by multiple primary users. To enhance the outage performance for the secondary network under an joint constraint of the interference threshold, Rayleigh fading channel and hardware noises caused by imperfect transceiver hardware, the secondary relays on the source-destination path cooperate to forward the source data to the destination. Particularly, they attempt to receive the source data from their previous nodes, and forward it to the secondary destination if requested. Moreover, whenever the destination cannot receive the source data successfully, a successful relay that has the shortest distance to the destination is selected for retransmission. Due to usage of the cooperative transmission, the proposed COOP protocol obtains better performance, as compared with the corresponding multi-hop relaying one (denoted DIRECT) which only uses direct transmission at each hop. We evaluate the outage performance of COOP and DIRECT via both simulation and theory. The obtained results present a significant performance enhancement, as comparing COOP with DIRECT.
From Non-Modular to Modular Concept of Bidirectional Buck/Boost Converter for Microgrid Applications
Authors: Frivaldsky Michal , Kascak Slavomir , Morgos Jan , Prazenica Michal
Published: June 2020

In this article, the practical comparison of the operational performance of the modular (or multiport) and non-modular bidirectional buck/boost (bi-BB) DC/DC converter is realized. The main contribution of the work is the evaluation of both concepts based on various aspects, considering the qualitative indicators of the systems relevant for microgrids. Here, we discuss efficiency, electrical properties, costs, and component values. At the same time, critical comparisons are provided for converters based on SiC and GaN technology (non-modular high-voltage SiC-based dual-interleaved converter and modular low-voltage GaN-based). The concepts are specific with their operating frequency, whereby for each solution, the switching frequency is different and directly influences relevant components. The efficiency, overall system volume, output voltage ripple, and input current ripple are compared mutually between both concepts with a dependency on power delivery. These factors, together with overall volume and costs, are very important considering modern converters for microgrid systems. The summary of pros and cons is realized for each of the proposed converters, whereby the evaluation criterion is reflected within the electrical properties targeting microgrid application.
Development of Future Compact and Eco-Friendly HVDC Gas-Insulated Systems: Shape Optimization of a DC Spacer Model and Novel Materials Investigation
Authors: Zebouchi Nabila , Li Haoluan , Haddad Manu A.
Published: June 2020

Testing and validating the electrical insulation performance of full-size compact high-voltage direct current (HVDC) gas-insulated systems, gas-insulated transmission lines (GIL) and gas-insulated switchgears (GIS) is very costly and take long time. Therefore, a reduced scale system was designed and constructed to study thoroughly the spacer’s performance when subjected to higher electric fields under HVDC with different shapes, made of new advanced materials, and housed in new SF6-free gas environment. Since the stationary DC electric field distribution along the spacer is controlled by spacer material conductivity and strongly depends upon its shape, this, the first part of two articles, proposes in a first step based on electric field calculations with COMSOL Multiphysics software, an optimized shape of a spacer model using a standard high-voltage alternating current (HVAC) alumina-filled epoxy material. Then, two novel types of materials were introduced and investigated: (i) modified filled epoxy material with a lower temperature-dependent conductivity than that of the standard HVAC material, which is interpreted by a lower thermal activation energy; and (ii) nonlinear resistive field grading material with a low nonlinearity coefficient, with and without the presence of a temperature gradient which occurs under operating service load. The numerical results show that, despite that the DC optimized profile of the spacer made of standard HVAC, alumina-filled epoxy is very effective in relaxing the electric field magnitudes along the spacer under uniform temperature—its distribution is significantly affected by the presence of a high temperature gradient causing the maximum electric field shifts along the spacer surface towards the earthed flange. Under this condition, the modified filled epoxy material with a weaker temperature-dependent conductivity results in a significant reduction of the electric field enhancement, representing thus a relevant key solution for HVDC GIL/GIS applications. Nonlinear resistive field grading material is also effective but seems unnecessary. The optimized DC spacer models are being fabricated for tests verification with C4-Perfluoronitrile (C4-PFN, 3MTM NovecTM 4710)/CO2 and Trifluoroiodomethane (CF3I)/CO2 gas mixtures in the reduced scale gas-insulated test prototype.
Retrofit Methodology Based on Energy Simulation Modeling Applied for the Enhancement of a Historical Building in L’Aquila
Authors: De Vita Mariangela , Massari Giulia , De Berardinis Pierluigi
Published: June 2020

Energy loss has not been addressed effectively by policies introduced to encourage the preservation and enhancement of historical structures. Material and other constraints, together with safety standard improvements, do not always guarantee adequate levels of environmental performance. An optimization of retrofit measures to align with new uses, new standards of comfort, and energy saving are needed, as are studies based on new best practices for the enhancement of architectural heritage. This paper presents a method that uses dynamic models tared on non-destructive surveys, and based on compatible energy and structural interventions derived from preliminary analyses integrated into special design tools. Energy simulations were carried out using Design Builder (6.1.5.002, Designbuilder Software Ltd, Stroud, UK) software. The case study is a former hospital, S. Salvatore, in L’Aquila, an architecturally important building, severely damaged by an earthquake in 2009. The methodology presented in this research includes in-depth investigations coherently systematized into a multi-scenario output using simulation software. The results guarantee a high level of compatibility with restoration and seismic guidelines, and new building environmental performance requirements.
Hydrophilic Coating of Copper Particle Monolayer Wicks for Enhanced Passive Water Transport
Authors: Kameya Yuki , Osonoe Ryota , Anjo Yuto
Published: June 2020

Passive water transport through thin-surface wicks made of heat conducting material is important for developing thermal management devices such as heat pipes and spreaders. In this study, we demonstrated the hydrophilic coating of a Cu particle monolayer wick for enhanced water transport. We fabricated a Cu particle monolayer using Cu powder with a nominal particle diameter of 100 μm and determined the particle size distribution using scanning electron microscopy (SEM). We observed a remarkable change in the water contact angle on the application of a hydrophilic coating, which demonstrated the enhanced passive water transport. The elemental mapping of Cu, O, and Si obtained by electron probe microanalysis confirmed the deposition of the SiO2-based coating material on each Cu particle. Although the Cu particles were only partially covered by SiO2, a remarkable enhancement in wettability was achieved. Finally, we conducted a rate-of-rise experiment to quantitatively characterize the water transport performance of the coated Cu particle monolayer. Thus, we propose hydrophilic coating as a simple and effective method to enhance passive water transport through Cu particle monolayer wicks.
An Improved SOM-Based Method for Multi-Robot Task Assignment and Cooperative Search in Unknown Dynamic Environments
Authors: Tang Hongwei , Lin Anping , Sun Wei , Shi Shuqi
Published: June 2020

The methods of task assignment and path planning have been reported by many researchers, but they are mainly focused on environments with prior information. In unknown dynamic environments, in which the real-time acquisition of the location information of obstacles is required, an integrated multi-robot dynamic task assignment and cooperative search method is proposed by combining an improved self-organizing map (SOM) neural network and the adaptive dynamic window approach (DWA). To avoid the robot oscillation and hovering issue that occurs with the SOM-based algorithm, an SOM neural network with a locking mechanism is developed to better realize task assignment. Then, in order to solve the obstacle avoidance problem and the speed jump problem, the weights of the winner of the SOM are updated by using an adaptive DWA. In addition, the proposed method can search dynamic multi-target in unknown dynamic environment, it can reassign tasks and re-plan searching paths in real time when the location of the targets and obstacle changes. The simulation results and comparative testing demonstrate the effectiveness and efficiency of the proposed method.
Analysis of Inter-Temporal Change in the Energy and CO2 Emissions Efficiency of Economies: A Two Divisional Network DEA Approach
Authors: Mehmood Khalid , Iftikhar Yaser , Chen Shouming , Amin Shaheera , Manzoor Alia , Pan Jinlong
Published: June 2020

Measuring changes in energy consumption and carbon dioxide emissions of various large economies is fundamental for analyzing the impact and effectiveness of various policies in this direction. This study analyzes intertemporal changes in energy and CO2 emissions efficiency of economies by applying a network data envelopment analysis approach that takes into consideration the internal structure of the analysis units. We have applied two divisional network data envelopment analysis models for analysis of the economic and distributive efficiency of economies from 2001 to 2011. The results are very useful in analyzing the situation; we found that none of the economies was efficient in both aspects in the sample period, implying that none of the countries in the analysis was efficient in the production and distribution of economic outputs simultaneously. Brazil, Canada, China and Germany showed improvement in economic efficiency but the distribution efficiency of the most of the economies is low because of the increase in population and high-income class. Most of the countries had an increase in the high-income class but China performed better in the second division because it has managed to improve its middle-income class in the recent past by moving more people from low-income class to middle income class. It is suggested that countries should emphasize on economic restructuring and expansion of the middle-income class to improve their performance in the production and distribution of economic outputs.
The Influence of Luminaire Photometric Intensity Curve Measurements Quality on Road Lighting Design Parameters
Authors: Czyżewski Dariusz , Fryc Irena
Published: June 2020

This article presents the research on a road lighting design. In this kind of design for a specific type of a roadway, the number and spacing of luminaires are calculated on the basis of luminaire photometric parameters such as intensity curve (LPIC) and luminous flux. The values of these parameters are measured using the luxmeter, i.e., a measuring instrument in which the spectral sensitivity should imitate spectral sensitivity of the human eye V(λ). However, the luxmeter’s spectral sensitivity S(λ) is not perfectly matched with the required one and varies for different instruments, resulting in measurement errors. To avoid this measurement error, the spectral mismatch correction factor (SMCF) should be applied to luxmeter’s readings. For a given luxmeter, the SMCF values depend on the measured light’s spectral composition SPD (described also by the lamp’s correlated color temperature CCT). Unfortunately, many laboratories do not apply SMCF to their luxmeter readings. Typical measurement laboratories are not in possession of SMCF data as this kind of data is hard to obtain and can be provided only by the state-of-the-art photometric laboratories for a high cost. Consequently, these typical measurement laboratories provide inaccurate LPIC data to costumers. In this article, it has been shown that a design process of road lighting installations needs to be based on lighting fixture LPIC’s measurements with SMCF values being taken into account. Omitting this fact may result in road lighting installation made on the basis of a design utilizing incorrect LPIC data, which would have higher energy consumption then expected at a design stage.
Adaptable Source-Grid Planning for High Penetration of Renewable Energy Integrated System
Authors: Tang Ming , Wang Jian , Wang Xiaohua
Published: June 2020

To adapt to the growing scale of renewable energy and improve the consume ability of the power system, it is necessary to design a highly adaptable planning scheme for high penetration of the renewable energy integrated system. Thus, this paper firstly gives the conception of system adaptability and designs an adaptability index system, which considers the supply and demand balance, operation state, and network structure of the high penetrated renewable energy integrated system. It can help to comprehensively evaluate the system ability towards uncertain shocks. Then, a two-stage source-grid coordinative expansion planning model is presented. The adaptability indexes of supply and demand balance are used as objection of the source planning stage, the adaptability indexed of the operation state and network structure are used to guide the grid planning stage. The model is further solved based on the coordination between the source and grid planning stage. Finally, the case study verifies that the obtained optimal plan has good adaptability to the impact of renewable energy on the power supply capacity and security operation.
Parameters of Transition from Deepening Longitudinal to Continuous Lateral Surface Mining Methods to Decrease Environmental Damage in Coal Clusters
Authors: Zhironkin Sergey , Selyukov Alexey , Gasanov Magerram
Published: June 2020

The present paper deals with an original way to reduce the environmental damage caused to land and air resources by surface coal mines with external dumping, due to the transition to internal dumping with filling the worked out space of the surface mine with overburden. The basic principle of the proposed idea is the transition from the deepening longitudinal mining method for the development of inclined and steep coal seam strata to lateral ones. This article substantiates the choice of technology for a block-and-layer continuous lateral mining method, including the construction of a first-stage pit, the use of a combined transport and direct dumping technology for moving overburden to an internal dump when mining blocks using draglines. The advantage of the presented technology, along with filling the internal capacity of the surface mine field with overburden, is the possibility of leveling the relief within the boundaries of the pit allotment and the implementation of reclamation as the mining front moves forward, without waiting for the dump to be completely filled in the boundary contours. Attention is also paid to the economic benefits of block-layer technology and the continuous lateral mining method, in the transition to which the overburden transporting costs can be significantly reduced, while the limitations of the proposed method’s implementation concern specific coal deposits that make up a small part of the fields being developed today by surface mining.
An Autonomous Home Energy Management System Using Dynamic Priority Strategy in Conventional Homes
Authors: Shakeri Mohammad , Amin Nowshad , Pasupuleti Jagadeesh , Mehbodniya Abolfazl , Asim Nilofar , Tiong Sieh Kiong , Low Foo Wah , Yaw Chong Tak , Samsudin Nurul Asma , Rokonuzzaman Md , Hen Chong Kok , Lai Chin Wei
Published: June 2020

With the growth in smart technology, customers have a chance to contribute to demand response programs and reduce their bills of electricity actively. This paper presents an intelligent wireless smart plug demonstration, which is designed to control the electrical appliances in the home energy management system (HEMS) application with a response to the utility company’s signal. Besides, a linear model of an energy management system utilizing a dynamic priority for electrical appliances is used as an energy management strategy. This can be useful for decreasing energy consumption in peak hours. Proposed hardware is tested with two different price strategies such as real-time pricing and a combination of this and incremental block rate (IBR) pricing. A small one-story house with ordinary electrical appliances is used as a test-bed for the proposed hardware and strategy. Initial results show that intelligent plugs can decrease the energy cost by 9% per day with an effective peak-to-average ratio deduction compared to the domicile without deploying intelligent plugs and controllers.
Continuous Control Set Model Predictive Control of a Switch Reluctance Drive Using Lookup Tables
Authors: Anuchin Alecksey , Demidova Galina L. , Hao Chen , Zharkov Alexandr , Bogdanov Andrei , Šmídl Václav
Published: June 2020

A problem of the switched reluctance drive is its natural torque pulsations, which are partially solved with finite control set model predictive control strategies. However, the continuous control set model predictive control, required for precise torque stabilization and predictable power converter behavior, needs sufficient computation resources, thus limiting its practical implementation. The proposed model predictive control strategy utilizes offline processing of the magnetization surface of the switched reluctance motor. This helps to obtain precalculated current references for each torque command and rotor angular position in the offline mode. In online mode, the model predictive control strategy implements the current commands using the magnetization surface for fast evaluation of the required voltage command for the power converter. The proposed strategy needs only two lookup table operations requiring very small computation time, making instant execution of the whole control system possible and thereby minimizing the control delay. The proposed solution was examined using a simulation model, which showed precise and rapid torque stabilization below rated speed.
The Effect of Alcohol Precipitants on Structural and Morphological Features and Thermal Properties of Lyocell Fibers
Authors: Makarov Igor S. , Golova Lyudmila K. , Vinogradov Markel I. , Levin Ivan S. , Shandryuk Georgiy A. , Arkharova Natalia A. , Golubev Yaroslav V. , Berkovich Anna K. , Eremin Timofei V. , Obraztsova Elena D.
Published: June 2020

This research examines the possibilities of regulating the structure of cellulose precursor fibers spun from solutions in N-methylmorpholine-N-oxide when replacing aqueous coagulation baths with thermodynamically softer alcohol baths at different temperatures. The fibers were spun by the dry jet–wet method in isobutanol coagulation baths with a temperature of 25 °C and 70 °C. The study of the phase state of the solvent–coagulant system using viscometry and point cloud methods revealed the temperature-concentration regions of the single-phase and two-phase states of the system. Using elemental analysis, DSC (differential scanning calorimetry) and XRD (X-ray diffraction) methods, it was shown that just spun fibers, due to the presence of a residual amount of solvent and coagulant in them, regardless of the temperature of the precipitator, have an amorphous structure. Additional washing with water completely washed away the solvent and coagulant as well, however, the structure of cellulose changes slightly, turning into a defective amorphous-crystalline one. A relationship was found between the phase composition, structure, and properties of just spun fibers and precursors washed with water. Thus, the loss of structural ordering of both just spun and washed cellulose fibers leads to a decrease in strength characteristics and an increase in deformation. The thermal behavior of the fibers is determined by their phase composition. Fibers just spun into hot alcohol containing a coagulant and traces of solvent acquire thermal stability up to 330 °C. During the pyrolysis of the obtained precursors up to 1000 °C, the value of the carbon yield doubles. The amorphized structure of the obtained fibers allows us to consider it as a model when analyzing the transformation of the structure of precursors during thermolysis.
Editorial on Special Issues “Aerogels” and “Aerogels 2018”
Authors: Quignard Françoise , Tanchoux Nathalie
Published: June 2020

Aerogels can be defined as ultralight materials with a 3D porous structure, similar to their parent wet gels, where the solvent has been replaced by a gas without a collapse of the gel structure, thanks to the drying process used (supercritical CO2 drying, freeze drying, etc [...]