bluuebunny/crossref_metadata_2025 huggingface dataset:
Kv7 Channels in Cyclic-Nucleotide Dependent Relaxation of Rat Intra-Pulmonary Artery
Authors: Al-Chawishly Mohammed , Loveland Oliver , Gurney Alison M.
Published: March 2022

Pulmonary hypertension is treated with drugs that stimulate cGMP or cAMP signalling. Both nucleotides can activate Kv7 channels, leading to smooth muscle hyperpolarisation, reduced Ca2+ influx and relaxation. Kv7 activation by cGMP contributes to the pulmonary vasodilator action of nitric oxide, but its contribution when dilation is evoked by the atrial natriuretic peptide (ANP) sensitive guanylate cyclase, or cAMP, is unknown. Small vessel myography was used to investigate the ability of Kv7 channel blockers to interfere with pulmonary artery relaxation when cyclic nucleotide pathways were stimulated in different ways. The pan-Kv7 blockers, linopirdine and XE991, caused substantial inhibition of relaxation evoked by NO donors and ANP, as well as endothelium-dependent dilators, the guanylate cyclase stimulator, riociguat, and the phosphodiesterase-5 inhibitor, sildenafil. Maximum relaxation was reduced without a change in sensitivity. The blockers had relatively little effect on cAMP-mediated relaxation evoked by forskolin, isoprenaline or treprostinil. The Kv7.1-selective blocker, HMR1556, had no effect on cGMP or cAMP-dependent relaxation. Western blot analysis demonstrated the presence of Kv7.1 and Kv7.4 proteins, while selective activators of Kv7.1 and Kv7.4 homomeric channels, but not Kv7.5, caused pulmonary artery relaxation. It is concluded that Kv7.4 channels contribute to endothelium-dependent dilation and the effects of drugs that act by stimulating cGMP, but not cAMP, signalling.
Dynamic Centrifuge Test and Numerical Modelling of the Seismic Response of the Tunnel in Cohesive Soil Foundation
Authors: Chen Zhengfa , Bian Minghui
Published: March 2022

Few studies have been published on the dynamic centrifuge model test of cohesive soil under earthquake action. The seismic response of cohesive soil foundation and tunnel was studied by the centrifuge experiment and numerical modelling. Through a comparison of the acceleration results of tunnel and cohesive soil foundation and the pore pressure and displacement of cohesive soil foundation, the influence of tunnel on cohesive soil foundation is discussed. The weak position of the tunnel under earthquake is predicted by effective numerical modelling. The results show that: (1) Under the Parkfield seismic wave, the natural frequency of the cohesive soil foundation with the tunnel is about 0.3 Hz, which is the most clear for the amplification of the low frequency component and the amplification of the seismic acceleration from bottom to top; (2) The acceleration response of the tunnel itself is small, and the effect of seismic wave on the surrounding soil is weakened due to the existence of tunnels; (3) The maximum bending moment and shear force appear at the corner of the rectangular tunnel, and the maximum axial force appears at the top of the rectangular tunnel; (4) The lateral displacement of the surface soil is the largest, and the pore pressure reduction in the middle soil is the largest compared with other soil layers. The existence of tunnels weakens the liquefaction potential of the surrounding soil.
Heterogeneous Catalysis and Advanced Oxidation Processes (AOPs) for Environmental Protection (VOC Oxidation, Air and Water Purification)
Authors: Fiorenza Roberto
Published: March 2022

The quality of air and water is a crucial and critical contemporary problem [...]
Insights into a New Formation Mechanism of Robust Cu/SiO2 Catalysts for Low-Temperature Dimethyl Oxalate Hydrogenation Induced by a Chelating Ligand of EDTA
Authors: Li Tianyou , Lin Ling , Chen Chongchong , Ye Runping , Huang Long , Yang Jinxia , Zhang Peng , Qin Yeyan , Cheng Jiankai , Yao Yuangen
Published: March 2022

The Cu/SiO2 catalyst has been widely used in dimethyl oxalate (DMO) hydrogenation due to its low cost and high efficiency. However, the reaction temperature of DMO hydrogenation is higher than the Hüttig temperature of Cu, and the smaller Cu particles are easier to agglomerate. Therefore, there is much interest in constructing a catalyst with a small particle size and strong stability. In the present work, the effect of introducing EDTA on Cu/SiO2 catalysts is systematically investigated. It not only was beneficial to form smaller copper nanoparticles (CuNPs) but also to enhance the stability of Cu species by introducing a suitable amount of EDTA. Furthermore, the surface Cu species were more evenly dispersed, and the number of active sites was increased with the introduction of EDTA; subsequently, the synergistic effect between Cu+ and Cu0 was enhanced. The best performance of 0.08E-Cu/SiO2 had been achieved in the DMO hydrogenation to ethylene glycol (EG), and the DMO conversion and EG selectivity reached 99.9% and 97.7%, respectively. Above all, the 0.08E-Cu/SiO2 catalyst exhibited a high level of stability during the 1200 h life test at 180 °C.
Temperature-Dependent Activity of Gold Nanocatalysts Supported on Activated Carbon in Redox Catalytic Reactions: 5-Hydroxymethylfurfural Oxidation and 4-Nitrophenol Reduction Comparison
Authors: Scurti Stefano , Allegri Alessandro , Liuzzi Francesca , Rodríguez-Aguado Elena , Cecilia Juan Antonio , Albonetti Stefania , Caretti Daniele , Dimitratos Nikolaos
Published: March 2022

In this study, the temperature-dependent activity of Au/AC nanocatalysts in redox catalytic reactions was investigated. To this end, a series of colloidal gold catalysts supported on activated carbon and titania were prepared by the sol immobilization method employing polyvinyl alcohol as a polymeric stabilizer at different hydrolysis degrees. The as-synthesized materials were widely characterized by spectroscopic analysis (XPS, XRD, and ATR-IR) as well as TEM microscopy and DLS/ELS measurements. Furthermore, 5-hydroxymethylfurfural (HMF) oxidation and 4-nitrophenol (4-NP) reduction were chosen to investigate the catalytic activity as a model reaction for biomass valorization and wastewater remediation. In particular, by fitting the hydrolysis degree with the kinetic data, volcano plots were obtained for both reactions, in which the maximum of the curves was represented relative to hydrolysis intermediate values. However, a comparison of the catalytic performance of the sample Au/AC_PVA-99 (hydrolysis degree of the polymer is 99%) in the two reactions showed a different catalytic behavior, probably due to the detachment of polymer derived from the different reaction temperature chosen between the two reactions. For this reason, several tests were carried out to investigate deeper the observed catalytic trend, focusing on studying the effect of the reaction temperature as well as the effect of support (metal–support interaction) by immobilizing Au colloidal nanoparticles on commercial titania. The kinetic data, combined with the characterization carried out on the catalysts, confirmed that changing the reaction conditions, the PVA behavior on the surface of the catalysts, and, therefore, the reaction outcome, is modified.
MRGPRX2-Mediated Degranulation of Human Skin Mast Cells Requires the Operation of Gαi, Gαq, Ca++ Channels, ERK1/2 and PI3K—Interconnection between Early and Late Signaling
Authors: Wang Zhao , Franke Kristin , Bal Gürkan , Li Zhuoran , Zuberbier Torsten , Babina Magda
Published: March 2022

The recent discovery of MRGPRX2 explains mast cell (MC)-dependent symptoms independently of FcεRI-activation. Because of its novelty, signaling cascades triggered by MRGPRX2 are rudimentarily understood, especially in cutaneous MCs, by which MRGPRX2 is chiefly expressed. Here, MCs purified from human skin were used following preculture or ex vivo and stimulated by FcεRI-aggregation or MRGPRX2 agonists (compound 48/80, Substance P) in the presence/absence of inhibitors. Degranulation was assessed by β-hexosaminidase or histamine release. Phosphorylation events were studied by immunoblotting. As a G protein-coupled receptor, MRGPRX2 signals by activating G proteins; however, their nature has remained controversial. In skin MCs, Gαi and Gαq were required for degranulation, but Gαi was clearly more relevant. Ca++ channels were likewise crucial. Downstream, PI3K was essential for granule discharge initiated by MRGPRX2 or FcεRI. ERK1/2 and JNK were additional participants, especially in the allergic route. Addressing possible points of intersection between early and later events, pERK1/2 and pAKT were found to depend on Gαi, further highlighting its significance. Gαq and Ca++ channels made some contributions to the phosphorylation of ERK. Ca++ differentially affected PI3K activation in FcεRI- vis-à-vis MRGPRX2-signaling, as channel inhibition increased pAKT only when triggered via FcεRI. Collectively, our study significantly extends our understanding of the molecular framework behind granule secretion from skin MCs.
Robotic Anxiety—Parents’ Perception of Robot-Assisted Pediatric Surgery
Authors: Ammer Elisabeth , Mandt Laura Sophie , Silbersdorff Isabelle Christine , Kahl Fritz , Hagmayer York
Published: March 2022

In contrast to many other countries, robot-assisted (RA) pediatric surgery is not yet very common in Germany. Although the first pediatric RA intervention was published in 2001, RA pediatric surgery is still perceived as a “new technology”. As a consequence, little is known about parents’ perception of this operation method. In this study, we analyzed parents‘ intention to let their child undergo RA and laparoscopic (LA) surgery. Two subsamples (online and at the University Medical Center Goettingen) received a questionnaire addressing attitude towards RA and LA pediatric surgery with the help of a case example. Results showed that parents had a higher intention to consent to LA surgery. Perceiving more benefits, assuming a positive attitude of the social environment, and feeling less anxiety increased intention. A mediation analysis indicated that the type of surgery affected intentions through assumed attitude of the social environment. Exploratory analyses showed that the perception of risks and anxiety reduced intention for only RA surgery. These findings should be considered in preoperational discussions with parents. Anxiety and perceived risks should especially be addressed in order to encounter hesitancy.
Integration of Vestibular and Auditory Information in Ontogenesis
Authors: Nikolaeva Elena I. , Efimova Victoria L. , Vergunov Eugeny G.
Published: March 2022

Background: We analyzed the hypothesis that the vestibular and auditory systems are integrative functions. Methods: The study involved 383 children (5.5 ± 2.4 years old). We assessed the conduct of auditory information by recording the auditory brain stem response (ABR), post-rotational nystagmus (PRN), and cervical vestibular evoked myogenic potentials (cVEMP), and calculated the integration of the parameters. All procedures were carried out using the JACOBI 4 software package. Results: We have found out that PRN, ABR, and cVEMP represent three different groups of integrative functions, each of which is conditioned by its own integrative mechanism. We have proven that PRN and ABR are associated with age, but no relationship was found between cVEMP and age. Conclusion: According to our data, the severity of ABR and PRN depended on age, while cVEMP was not associated with age. The functional immaturity of the child’s vestibular system, which probably arose in utero, often becomes apparent only at school when reading and writing must be mastered. These skills require maturity of both the vestibule ocular and vestibule spinal functions of the vestibular system.
Both Medical and Context Elements Influence the Decision-Making Processes of Pediatricians
Authors: Schurmans Lisa , De Coninck David , Schoenmakers Birgitte , de Winter Peter , Toelen Jaan
Published: March 2022

We wanted to investigate the relationship of medical and non-medical factors with the clinical decision-making of pediatricians. We hypothesize that the addition of relevant medical information (either alarming or reassuring) will influence the physician’s decision-making, but that the addition of non-medical information will also play a role. To investigate this, we designed an online questionnaire containing ten clinical case-based scenarios, of which five focused on medical factors and five on non-medical/context factors, each scored on a five-point Likert scale. In total, 113 pediatricians completed the online questionnaire. Both medical and non-medical/context factors were considered relevant to change the initial decision in most cases. Additional information of an alarming nature induces the physician to become more worried, whereas reassuring information decreases this worry. In some cases, with the medical factors, the gender and the age of the pediatrician does have some effect on the clinical decision-making. We conclude that medical decision-making is affected by multiple intrinsic and extrinsic factors that differ between physicians. Our data indicate that these non-medical factors must be considered when making a medical decision, as it is crucial to be aware that they have a substantial influence on that decision-making.
Tinaksite and Tokkoite: X-ray Powder Diffraction, Optical, and Vibrational Properties
Authors: Kaneva Ekaterina , Shendrik Roman
Published: March 2022

In this study, natural tinaksite (K2Ca2NaTi[Si7O18OH]O) and tokkoite (K2Ca4[Si7O18OH](OH,F)) collected in charoite rocks of the Murun alkaline massif (Siberia, Russia) were examined by X-ray diffraction and optical and vibrational spectroscopic methods. A comparative analysis of the experimental diffraction patterns with respect to the calculated X-ray powder diffraction patterns was carried out for tinaksite and tokkoite powders. The shift in the diffraction peaks of tinaksite is explained by the smaller values of the unit cell parameters a and b as compared with those of tokkoite. A similar shift of the peaks is also observed in the Raman and infrared absorption spectra; however, this feature is explained by the difference in the chemical composition of the minerals. The shoulder in the absorption spectra at about 800 nm in tinaksite and 700 nm in tokkoite corresponds to the presence of Mn2+ and Fe3+ absorption bands, the presence of which determines the color of tinaksite and tokkoite. The luminescence band with a maximum at about 540–550 nm in the photoluminescence spectra is related to Mn2+ centers, while an additional band at about 610 nm can be associated with Ti3+ centers in tinaksite. The intensity of the Fe3+ ESR signal increases in both samples after heating, while the intensities of the bands associated with OH groups decrease in tinaksite and tokkoite. This characteristic is the result of iron oxidation and dehydrogenation reaction.
Clinic, Endoscopic and Histological Features in Patients Treated with ICI Developing GI Toxicity: Some News and Reappraisal from a Mono-Institutional Experience
Authors: Parente Paola , Maiorano Brigida Anna , Ciardiello Davide , Cocomazzi Francesco , Carparelli Sonia , Guerra Maria , Ingravallo Giuseppe , Cazzato Gerardo , Carosi Illuminato , Maiello Evaristo , Bossa Fabrizio
Published: March 2022

Background: Immune checkpoint inhibitors (ICIs) have widened the therapeutic scenario of different solid tumors over the last ten years. Gastrointestinal (GI) adverse events (AEs), such as diarrhea and colitis, occur in up to 50% of patients treated with ICIs. Materials and methods: We conducted a single-center retrospective analysis in patients with solid tumors treated with ICIs in a 6-year period, from 2015 to 2021, developing GI AEs, for which an endoscopic analysis was performed, with available histological specimens or surgery. Results: Twenty-one patients developed GI AEs under ICIs. The median time from the start of ICIs to the onset of GI AEs was 5 months. Diarrhea was the most frequent symptom (57.2%), upper GI symptoms presented in four patients (19%), while three patients (14.3%) had no symptoms and were diagnosed occasionally. Two patients underwent surgical resection for acute abdomen. Histological findings observed in endoscopic sampling were eosinophilic-pattern gastro-enterocolitis, apoptotic damage, IBD-like features, and ischemic-like changes. Histological damage was also documented in patients with unremarkable endoscopy. Conclusions: Under ICI therapy, GI toxicity is an expected event. Since GIAEs can mimic a broad range of primary GI diseases, a multidisciplinary approach is advocated with upper and lower GI mucosal sampling to remodel therapy and avoid complications.
Abrasion Behavior of Different Charcoal Toothpastes on Human Dentin When Using Electric Toothbrushes
Authors: Osmanaj Nadin , Petersen Svea , Eisenburger Michael , Greuling Andreas
Published: March 2022

The aim of this study was to investigate abrasion on human dentin after brushing with activated charcoal toothpastes. A self-designed brushing machine was used to brush five groups (Group A: Water, Group B: Sensodyne Pro Schmelz, Group C: Splat Blackwood, Group D: Curaprox Black is White, and Group E: Prokudent Black Brilliant) with electrically powered toothbrushes for 4 h. The abrasive dentin wear was calculated using profilometry data. Furthermore, thermogravimetric analyses and scanning electron microscopy were used to analyze the composition of the toothpastes. Mean dentin loss by brushing were (71 ± 28) µm (Splat Blackwood), (44 ± 16) µm (Curaprox Black is White), (38 ± 13) µm (Prokudent Black Brilliant), (28 ± 14) µm (Sensodyne Pro Schmelz), and (28 ± 13) µm (Water). Groups A/B/D/E and group C each lie in one subset, which is statistically different from the other subset according to a post hoc Tukey test (p = 0.05). Within the limitations, it can be concluded that the content of activated charcoal in charcoal toothpastes had little influence on the observed abrasive behavior, although one of the charcoal toothpastes showed the highest abrasion on dentin.
Functional Connectivity Methods and Their Applications in fMRI Data
Authors: Shahhosseini Yasaman , Miranda Michelle F.
Published: March 2022

The availability of powerful non-invasive neuroimaging techniques has given rise to various studies that aim to map the human brain. These studies focus on not only finding brain activation signatures but also on understanding the overall organization of functional communication in the brain network. Based on the principle that distinct brain regions are functionally connected and continuously share information with each other, various approaches to finding these functional networks have been proposed in the literature. In this paper, we present an overview of the most common methods to estimate and characterize functional connectivity in fMRI data. We illustrate these methodologies with resting-state functional MRI data from the Human Connectome Project, providing details of their implementation and insights on the interpretations of the results. We aim to guide researchers that are new to the field of neuroimaging by providing the necessary tools to estimate and characterize brain circuitry.
A Multi-Classification Hybrid Quantum Neural Network Using an All-Qubit Multi-Observable Measurement Strategy
Authors: Zeng Yi , Wang Hao , He Jin , Huang Qijun , Chang Sheng
Published: March 2022

Quantum machine learning is a promising application of quantum computing for data classification. However, most of the previous research focused on binary classification, and there are few studies on multi-classification. The major challenge comes from the limitations of near-term quantum devices on the number of qubits and the size of quantum circuits. In this paper, we propose a hybrid quantum neural network to implement multi-classification of a real-world dataset. We use an average pooling downsampling strategy to reduce the dimensionality of samples, and we design a ladder-like parameterized quantum circuit to disentangle the input states. Besides this, we adopt an all-qubit multi-observable measurement strategy to capture sufficient hidden information from the quantum system. The experimental results show that our algorithm outperforms the classical neural network and performs especially well on different multi-class datasets, which provides some enlightenment for the application of quantum computing to real-world data on near-term quantum processors.
A Comprehensive Overview of Education during Three COVID-19 Pandemic Periods: Impact on Engineering Students in Sri Lanka
Authors: Ilangarathna Gayanthi A. , Ranasinghe Yasiru , Weligampola Harshana , Attygalla Erandi , Ekanayake Janaka , Yatigammana Sakunthala , Pinnawala Mallika , Godaliyadda Roshan , Herath Vijitha , Ekanayake Parakrama , Thilakaratne Ganga , Dharmarathne Samath
Published: March 2022

The COVID-19 pandemic has impacted the education system in Sri Lanka, similar to many countries in the world. As a result, the mode of education shifted from conventional face-to-face classes to online mode. The main objective of this study is to provide a comprehensive overview of the changes to the educational system due to the COVID-19 pandemic among engineering undergraduates of Sri Lanka over three identified pandemic periods. Quantitative descriptive analysis was used together with chi-square statistics to answer the research questions using the data collected through a google survey from engineering undergraduates in Sri Lanka. According to the results, students’ attendance in online classes has improved over time compared to the initial pandemic period. Nearly 50% of students’ family income has been impacted, either stopped or reduced due to the pandemic. Most students have issues regarding computing devices, internet connectivity, and the home environment. According to the chi-square statistics results, few of these issues had a statistically significant relationship between the family income; lower the income, higher the negative impact on students. More than half of the students felt isolated when studying at home during the pandemic. Still, more than 50% of students agreed that lecturers were well prepared to guide and deliver lessons remotely. The overall recommendations of the study are implementing workshops, training on new technologies, awareness programs for educational stakeholders, providing incentives to purchase digital devices, and improving internet connectivity to improve the new standard education system of Sri Lanka.
Study of Kindergarten Teachers’ Intentions to Choose Content and Teaching Method for Teaching Science
Authors: Zoupidis Anastasios , Tselfes Vasilis , Papadopoulou Penelope , Kariotoglou Petros
Published: March 2022

In this paper, we investigate the intentions of kindergarten teachers to use the content and to apply the teaching methods that they acquired in a one-day teacher training seminar. According to the theory of planned behavior, the answer to this research question is directly related to a series of social-psychological personal criteria assessments, such as an assessment of the personal gains or losses, the opinions of important third persons, the teacher’s own assessment of the value of the students’ learning, and the perceived behavioral control assessment. A total of 114 participants completed a 5-point Likert-scale questionnaire that consisted of two sets of five questions each. The results show that the kindergarten teachers’ intentions to use particular content and teaching methods are based on whether they have the skills to apply them successfully, and on their assessment of the ability of their students to acquire meaningful knowledge. The teacher’s choice of teaching method is also associated with the assessment of the personal gains or losses, as well as with the opinions of important third persons. Furthermore, the study findings show that there are two distinct categories of kindergarten teachers: those whose teaching is based on the tradition of science education, and those whose teaching is based on the tradition of early childhood education. The teaching implications of the results are also discussed.
A LoRaWAN Network Architecture with MQTT2MULTICAST
Authors: Navarro-Ortiz Jorge , Chinchilla-Romero Natalia , Delgado-Ferro Felix , Ramos-Munoz Juan Jose
Published: March 2022

In this work, an architecture for IoT networks oriented towards environmental sustainability is presented. Due to the suitability of its characteristics in terms of coverage, power and support of a large number of devices, an enhanced LoRaWAN network has been chosen as the basis for this proposal. The architecture is completed with the virtualization of the different LoRaWAN network entities and the usage of a software-defined network for their interconnection. The publication and subscription to environmental data is carried out by using the MQTT protocol. MQTT has been optimized thanks to the use of the SDN network and the use of edge computing resources, which allows multicasting of published data. Thanks to our developed MQTT2MULTICAST protocol, latency is improved by approx. 90% and the traffic load within the SDN network is reduced by 55%. An scalability analysis shows that this solution is able to support tens of thousands of LoRaWAN gateways. The proposed architecture has been implemented using commercial equipment as a proof of concept.
A Survey of One Class E-Commerce Recommendation System Techniques
Authors: Khoali Mohamed , Laaziz Yassin , Tali Abdelhak , Salaudeen Habeeb
Published: March 2022

Although several recommendation algorithms are widely used by both commercial and non-commercial platforms, they face unique challenges such as sparse data sets and the absence of negative or “neutral” feedback. One-class algorithms attempt to overcome the data sparsity problem by using the implicit feedback inherent in user’s clicks and purchases, which are deduced from both positive and negative feedback. Existing literature uses several heuristic strategies to derive the negative samples needed for training, such as using random sampling or utilizing user-item interaction. However, these assumptions do not always reflect reality. In addition, with the explosive increase in the availability of big data for training recommendation systems, these methods might not adequately encapsulate the representations of the latent vectors. In this paper, we address the common issues of one-class recommendation and provide a survey on approaches that have been used to mitigate the existing challenges. To tackle the identified problems, we propose a neural network-based Bayesian Personalized Ranking (BPR) for item recommendation and personalized ranking from implicit feedback. BPR provides an optimization criterion derived from Bayesian analysis of a problem to develop an optimized model for such a problem. We conduct several experiments on two varieties of MovieLens datasets to illustrate the performance of the proposed approach. Our approach shows an impressive result in mitigating the issues of one-class recommendation when compared with the complexity of the state-of-the-art methods.
A Study of the Vibration Characteristics of Flexible Mechanical Arms for Pipe String Transportation in Oilfields
Authors: Wang Yan , Lu Shuwen , Gao Sheng , Ren Yongliang , Zhang Ruijie
Published: March 2022

During the drilling and repairing of wells, the pipe string transfer equipment has a high work frequency. The movement accuracy, response speed, and controllability of the equipment have significant impacts on the stability. In this paper, we propose an analysis method of mechanical arms to lift pipe strings using a rigid–flexible coupling model. With the mechanical arm as a flexible body and the mechanical hand as a rigid body, a numerical calculation model of the rigid-flexible coupling of the system was established based on the Lagrangian equation. ADAMS and Ansys software were applied to numerical simulations of this system to investigate the lifting characteristics, the influence of the operation parameters and structure parameters, and the contact collision analysis of the mechanical arm. The conditions of rigid–flexible modeling for the multi-body system and the main factors affecting the vibration characteristics of the flexible arm are described. We conclude that the arm should be modeled as a rigid body if the structure parameter [w/l] (elastic deformation/length) is between 1/650 and 1/1000, the system can be modeled as a rigid–flexible coupling if [w/l] is between 1/400 and 1/650, and the arm should be modeled as a flexible body and the influence and compensation of the control method should be considered if [w/l] is between 1/250 and 1/400.
Electricity Sector Reform Performance in Sub-Saharan Africa: A Parametric Distance Function Approach
Authors: Asantewaa Adwoa , Jamasb Tooraj , Llorca Manuel
Published: March 2022

Electricity sector reforms have transformed the structure and organization of the sector worldwide. While outcomes of reforms in developed and developing countries have been extensively examined, there is limited analysis of the reforms in sub-Saharan Africa (SSA). This paper analyses the performance of electricity sector reforms in 37 SSA countries between 2000 and 2017. We use a stochastic frontier analysis approach to estimate a multi-input multi-output distance function to assess the impact of reform steps and institutional features on indicators of investment and technical efficiency. Results indicate a positive correlation between reforms and installed generation capacity per capita, plant load factor, and technical network losses. The presence of an electricity law, sector regulator, vertical unbundling, and private participation in the management of assets were positively correlated with reform performance. Perceptions of non-violent institutional features such as corruption, regulatory quality and governance effectiveness do not seem to have had a significant effect, but perceptions of political stability, violence, and terrorism influenced reform outcomes. We conclude that a workable reform in SSA involves vertical unbundling with an electricity law, a regulator, and private ownership and management of assets where feasible. However, positive outcomes go hand in hand with higher technical network energy losses which indicates higher investment in the generation segment than in the network segment. Hence, emphasis should be placed on decoupling the energy losses from power generation.
Pore-Scale Flow Fields of the Viscosity-Lost Partially Hydrolyzed Polyacrylamide Solution Caused by Sulfide Ion
Authors: Yu Xiaoluan , Niu Hao , Li Hua , Du Chunan , Song Zhiyong , Kong Debin , Zhu Weiyao
Published: March 2022

The rheology of a partially hydrolyzed polyacrylamide (HPAM) solution plays an important role in its oil recovery during polymer flooding. However, multiple factors in brine, such as sulfide ions, cause a dramatic loss in the viscosity and oil recovery. To better understand the sulfide-induced viscosity loss and the consequent flow mechanisms in pore networks, the morphology of polymer solutions with and without sulfide ion was observed by scanning electron microscopy; and the variations of the pore scale flow fields were demonstrated by a microscopic visualization seepage experiment combined with Micro-PIV (Microscale Particle Image Velocimetry). The results showed that, with the presence of sulfide ion, the microstructure of the polymer changed from a uniform three-dimensional network structure to loose and uneven floccules, which resulted in viscosity loss (over 70% with 5-mg/L sulfide ion). Moreover, higher concentrations of sulfide ions (5 mg/L and 10 mg/L) resulted in earlier shear thinning characteristics than those with lower sulfide concentrations. Due to viscosity loss, the average flow velocity in the main stream of the microscopic seepage experiment increased more significantly than that without sulfide. However, the viscosity loss alone cannot independently explain the severe viscous fingering during the subsequent post-water flooding, which was about five times greater than that of the primary water flooding in terms of the velocity ratio between the mainstream and margin. A further pore-scale flow field analysis exhibited an eccentric and a bimodal velocity distribution in the throat along the radial and axial directions, respectively. The former distribution indicated that the adsorbed polymer on the pore wall was broken through by hydraulic shear due to the collapsed structure caused by sulfide ion. The latter suggested that another sulfide-induced impact was an earlier-occurring non-Newtonian characteristic with a low shear rate. Therefore, instead of viscosity loss, elastic loss is the dominant mechanism affecting the characteristics of the aggregate flow field under the action of sulfide. Microscopic flooding combined with Micro-PIV is a feasible and essential method to reveal pore scale flow mechanisms.
Performance Evaluation of 5G Waveforms for Joint Radar Communication over 77 GHz and 24 GHz ISM Bands
Authors: Khelouani Imane , Elbahhar Fouzia , Elassali Raja , Idboufker Noureddine
Published: March 2022

The V2X environment poses many challenges to emerging wireless communication systems, while it is crucial to ensure the efficiency and safety of road users. Requiring continual localization of the surroundings and accurate obstacle detection while providing high reliability in dense networks and low latency in high-mobility environment communication systems imposes a challenge to the driver-assistance field given that we are overly limited in terms of frequency bands and resources. Hence, pooling of the available frequency resources between different applications can help increase the spectral efficiency. A new collaborative approach multiplexed in the time domain, namely RadCom, which can be described as a joint radar and communication system that performs both vehicle-to-everything communication and detection of the neighboring obstacles in the vehicular environment, has been proposed to overcome the limitations of the existing conventional radar system. Based on orthogonal frequency division multiplexing (OFDM), this RadCom system proved to be suitable up to now for V2X. Moreover, a new RadCom system based on universal frequency multi-carrier (UFMC), an advanced fifth-generation (5G) waveform, has been proposed to enhance the spectral efficiency and surmount the shortcomings induced by the OFDM waveform. This recent RadCom system has been studied in the new frequency range of 76–81 GHz; precisely, 77 GHz. Hence, in this paper, we propose to compare both subsystems of the proposed RadCom system over two different frequency carriers, 24 GHz and 77 GHz, and to adopt the proper system parametrization in order to meet appropriate wireless solutions for automotive RadCom systems.
Time Evolution of Partial Discharges in a Dielectric Subjected to the DC Periodic Voltage
Authors: Imburgia Antonino , Rizzo Giuseppe , Romano Pietro , Ala Guido , Candela Roberto
Published: March 2022

Partial discharge (PD) detection can be considered one of the most useful tools for assessing the insulation conditions of the power apparatus in high-voltage systems. Under AC conditions, this analysis is widely employed in online and offline tests, such as type tests or commissioning, and can be carried out by applying the phase-resolved PD (PRPD) method, since the patterns can give information about the defect classification. Under DC voltages, the classic pattern recognition method cannot be performed, and the measurements show complexities related to the nature of the phenomena. For this reason, to date, a standard for PD measurements under DC does not exist. In previous papers, a new method for PD detection under DC stress voltages has been proposed by the authors. It is based on the application of a direct current periodic (DCP) waveform useful in obtaining PRPD patterns. The dependence of partial discharge inception voltage (PDIV) and PD repetition rate (PDRR) on the δ shape parameter of the DCP for different materials, as well as the capability to recognize different discharge phenomena, provided valid indications on the behavior of PD in the transition from AC to DC. The aim of this paper is to evaluate the time dependence of PD occurring in a dielectric by applying the DCP waveform. In our previous studies, the investigations were focused on the PD behavior under different values of the DC voltage periodic part. In another work, the DCP waveform with both positive and negative polarity was applied to several dielectric materials. In the proposed work, instead, the DCP waveform is applied for a long time in order to observe its effect on the PD behavior for 72 h. In this way, due to the space charge accumulation phenomenon, the aging effect, also due to the space charge accumulation phenomenon, is evaluated. The methodological approach was to acquire PRPD patterns over time and evaluate their trends in comparison with the sinusoidal case. The experimental results show that, with a DCP waveform having δ = 0.6, the aging effect similar to that provided by pure DC stress is observed, while the acquired PRPD patterns are easily interpretated, as in the AC case.
Permeability Prediction Using Machine Learning Methods for the CO2 Injectivity of the Precipice Sandstone in Surat Basin, Australia
Authors: Rezaee Reza , Ekundayo Jamiu
Published: March 2022

This paper presents the results of a research project which investigated permeability prediction for the Precipice Sandstone of the Surat Basin. Machine learning techniques were used for permeability estimation based on multiple wireline logs. This information improves the prediction of CO2 injectivity in this formation. Well logs and core data were collected from 5 boreholes in the Surat Basin, where extensive core data and complete sets of conventional well logs exist for the Precipice Sandstone. Four different machine learning (ML) techniques, including Random Forest (RF), Artificial neural network (ANN), Gradient Boosting Regressor (GBR), and Support Vector Regressor (SVR), were independently trained with a wide range of hyper-parameters to ensure that not only is the best model selected, but also the right combination of model parameters is selected. Cross-validation for 20 different combinations of the seven available input logs was used for this study. Based on the performances in the validation and blind testing phases, the ANN with all seven logs used as input was found to give the best performance in predicting permeability for the Precipice Sandstone with the coefficient of determination (R2) of about 0.93 and 0.87 for the training and blind data sets respectively. Multi-regression analysis also appears to be a successful approach to calculate reservoir permeability for the Precipice Sandstone. Models with a complete set of well logs can generate reservoir permeability with R2 of more than 90%.
Automatic Inspection of Photovoltaic Power Plants Using Aerial Infrared Thermography: A Review
Authors: de Oliveira Aline Kirsten Vidal , Aghaei Mohammadreza , Rüther Ricardo
Published: March 2022

In recent years, aerial infrared thermography (aIRT), as a cost-efficient inspection method, has been demonstrated to be a reliable technique for failure detection in photovoltaic (PV) systems. This method aims to quickly perform a comprehensive monitoring of PV power plants, from the commissioning phase through its entire operational lifetime. This paper provides a review of reported methods in the literature for automating different tasks of the aIRT framework for PV system inspection. The related studies were reviewed for digital image processing (DIP), classification and deep learning techniques. Most of these studies were focused on autonomous fault detection and classification of PV plants using visual, IRT and aIRT images with accuracies up to 90%. On the other hand, only a few studies explored the automation of other parts of the procedure of aIRT, such as the optimal path planning, the orthomosaicking of the acquired images and the detection of soiling over the modules. Algorithms for the detection and segmentation of PV modules achieved a maximum F1 score (harmonic mean of precision and recall) of 98.4%. The accuracy, robustness and generalization of the developed algorithms are still the main issues of these studies, especially when dealing with more classes of faults and the inspection of large-scale PV plants. Therefore, the autonomous procedure and classification task must still be explored to enhance the performance and applicability of the aIRT method.
Battery State of Charge Estimation Based on Composite Multiscale Wavelet Transform
Authors: Cheng Yan , Zhang Xuesen , Wang Xiaoqiang , Li Jianhua
Published: March 2022

The traditional battery state of charge (SOC) estimation method, which is based on neural networks, directly uses terminal voltage and terminal current as the input data. Although it is convenient to implement, it produces a large estimation error when the current and voltage change drastically. To solve this problem, a new method, which uses a composite multiscale wavelet transform, is proposed to estimate the battery SOC. In the proposed method, a wavelet transform is applied to the input data, and this process obtains the approximate coefficients and detail coefficients of the input data at different scales. A neural network then uses these coefficients as inputs to estimate the SOC. The experimental results show that the proposed method can improve the accuracy of the battery SOC estimation without changing the neural network structure or algorithm.
Dual-Domain Maximum Power Tracking for Multi-Input RF Energy Harvesting with a Reconfigurable Rectifier Array
Authors: Chen Mu-Chun , Sun Tsung-Wen , Tsai Tsung-Heng
Published: March 2022

This work proposes a dual-domain maximum power tracking (MPPT) technique for multiple-input RF energy harvesting systems. A differential rectifier array is used to implement 4-channel reconfigurable RF to DC power conversion, and an adjustable 4-bit capacitor array is designed to improve the impedance matching between the antennas and the rectifiers. Using the perturbation and observation (P&O) method, both arrays are adaptively configured in the background with the variations of the input energy and output loading. Experimental results show that the proposed circuit successfully tracks the maximum power points while harvesting RF energy, with the peak conversion efficiency of 49.06% when the input energy is −6 dBm. With the proposed dual-domain MPPT, the high efficiency range of the energy harvesting system is greatly extended to 21 dB (−21–0 dBm).
Moisture Transfer Characteristics and Kinetics Determination for Insulated Paperboard in Hot-Pressing Process
Authors: Kong Lingbo , Zhao Jingyi , Li Jiahao , Yuan Yuejin
Published: March 2022

The transport characteristics and kinetics of moisture in hot-pressing are crucial to controlling the insulated paperboard drying process. The effects of operating temperature (110, 120, and 130 °C) on moisture transfer characteristics of an insulated paperboard were investigated. The results showed that the hot-pressing process consists of four successive stages, i.e., the warm-up stage, the boiling-point temperature stabilization stage, the temperature slowly rising stage, and the constant temperature stage. It was observed that a higher temperature mainly affected the medium and later stages of the hot-pressing process. When the operating temperature increased from 110 to 130 °C, the maximum value of the drying rate increased by 16.04%, and the drying time decreased by 62.50% consequently. Furthermore, a new mathematical model used to describe the moisture transfer kinetics for the insulated paperboard hot-pressing was developed in this paper. The results from the proposed new model were evaluated with another eight commonly used models. It showed better predictions and satisfactorily described the moisture transfer kinetics of the insulated paperboard compared with other models under the investigated hot-pressing conditions. The values of R2, χ2, and root mean square error (RMSE) of the new model varied from 0.99961 to 0.99999, 0.00001 to 0.00005, and 0.00120 to 0.00599, respectively.
Dynamics Changes of Microorganisms Community and Fermentation Quality in Soybean Meal Prepared with Lactic Acid Bacteria and Artemisia argyi through Fermentation and Aerobic Exposure Processes
Authors: Wang Weiwei , Tan Zhongfang , Gu Lingbiao , Ma Hao , Wang Zhenyu , Wang Lei , Wu Guofang , Qin Guangyong , Wang Yanping , Pang Huili
Published: March 2022

This study evaluated the effects of Lactiplantibacillus plantarum subsp. plantarum ZA3, Artemisia argyi and their combination, on the fermentation characteristics, microbial community, mycotoxins and crude flavonoids content of fermented soybean meal during fermentation (under anaerobic conditions) and aerobic exposure (under aerobic conditions). The results showed that ZA3, Artemisia argyi and ZA3+ Artemisia argyi groups had lower pH values and higher lactic acid concentrations compared with controls, and additives increased the abundance of Lactiplantibacillus and decreased those of Acetobacter and Enterobacter; in particular, Artemisia argyi and ZA3+ Artemisia argyi reduced the abundance of fungi, such as Aspergillus, Pichia, Fusarium, Cladosporium and Xeromyces. Meanwhile, the contents of mycotoxins were lower in treated groups, and even mycotoxins in the control were significantly reduced after 30 d (p < 0.05). Crude flavonoids that were correlated positively with Lactococcus and negatively with Bacillus, Aspergillus, Enterobacter and Kazachstania were significantly higher in the Artemisia argyi and ZA3+ Artemisia argyi groups (p < 0.05).
Isolation, Characterization and Antioxidant Activity of Yam Polysaccharides
Authors: Li Zhedong , Xiao Wenhao , Xie Jianhua , Chen Yi , Yu Qiang , Zhang Weidong , Shen Mingyue
Published: March 2022

This study aimed to characterize the structure of Chinese yam (Dioscoreae Rhizoma) polysaccharide (CYP) and to investigate its protective effect against H2O2-induced oxidative damage in IEC-6 cells. The chemical composition and structural characteristics of the samples were analyzed by chemical and instrumental methods, including high-performance gel permeation chromatography, high-performance anion-exchange chromatography (HPAEC), Fourier transformed infrared (FT-IR), ultraviolet (UV), and scanning electron microscopy (SEM). Antioxidant activity was evaluated by establishing a cellular model of oxidative damage. The molecular weight of CYP was 20.89 kDa. Analysis of the monosaccharide composition revealed that CYP was primarily comprised of galactose (Gal), glucose (Glu), and galacturonic acid (GalA), and the ratio between them was 28.57:11.28:37.59. Pretreatment with CYP was able to improve cell viability, superoxide dismutase (SOD) activity, and reduce intracellular reactive oxygen species (ROS) production and malondialdehyde (MDA) content after H2O2 injury. CYP also attenuated oxidative damage in cells through the mitogen-activated protein kinase (MAPK) signaling pathway. This study showed that CYP was an acidic heteropolysaccharide with a good protective effect against oxidative damage, and it thus has good prospects in food and biopharmaceutical industries.