bluuebunny/crossref_metadata_2025 huggingface dataset:
The Stationary Concentrated Vortex Model
Authors: Onishchenko Oleg , Fedun Viktor , Horton Wendell , Pokhotelov Oleg , Astafieva Natalia , Skirvin Samuel J. , Verth Gary
Published: February 2021

A new model of an axially-symmetric stationary concentrated vortex for an inviscid incompressible flow is presented as an exact solution of the Euler equations. In this new model, the vortex is exponentially localised, not only in the radial direction, but also in height. This new model of stationary concentrated vortex arises when the radial flow, which concentrates vorticity in a narrow column around the axis of symmetry, is balanced by vortex advection along the symmetry axis. Unlike previous models, vortex velocity, vorticity and pressure are characterised not only by a characteristic vortex radius, but also by a characteristic vortex height. The vortex structure in the radial direction has two distinct regions defined by the internal and external parts: in the inner part the vortex flow is directed upward, and in the outer part it is downward. The vortex structure in the vertical direction can be divided into the bottom and top regions. At the bottom of the vortex the flow is centripetal and at the top it is centrifugal. Furthermore, at the top of the vortex the previously ascending fluid starts to descend. It is shown that this new model of a vortex is in good agreement with the results of field observations of dust vortices in the Earth’s atmosphere.
Carbonation Resistance of Surface Protective Materials Modified with Hybrid NanoSiO2
Authors: Xia Kailun , Gu Yue , Jiang Linhua , Guo Mingzhi , Chen Lei , Hu Feilong
Published: February 2021

To date, reinforcement concrete is the main construction material worldwide. As the concentration of atmospheric CO2 is steadily increasing, carbonation of the reinforcement concrete becomes a pressing concern. In this study, novel surface protective materials (SPMs) modified with hybrid nanoSiO2 (HNS), fly ash, and slag were developed to reduce CO2 emissions and extend the service life of the reinforcement concrete. The carbonation depths were measured by phenolphthalein to reflect the carbonation resistance. X-ray diffraction (XRD), fourier-transform infrared spectroscopy (FTIR), and thermal gravimetric analysis (TGA) were conducted to analyze the chemical components of the samples after carbonation. In addition, MIP was carried out to examine the microstructures of the samples prior to carbonation. Thermodynamic modeling was employed to calculate the changes in the phase assemblages of each blends in an ideal situation. The experimental results showed that the carbonation depth and CaCO3 content of the SPM modified with HNS decreased by 79.0% and 64.6% compared with the reference, respectively. The TGA results showed that after carbonation, the CaCO3 contents were 4.40% and 12.42% in the HNS modified samples and reference samples, respectively. MIP analysis demonstrated that the incorporation of HNS in SPM led to a 48.3% and 58.5% decrease in big pores and capillary pores, respectively. Overall, the SPMs modified with HNS in this study possessed better carbonation resistance and refined pore structures.
Flexible Structural Color Films Based on Electro-Hydrodynamic Inkjet Printing
Authors: Choi Ju-Hwan , Ahn Ju-Hun , Lee Chang-Yull
Published: February 2021

Structural coloration based on nanostructures is one of the alternatives that can prevent environmental pollution compared to the use of chemically synthesized materials. This technique has attracted considerable attention for various applications, including displays and sensors. In this study, a photonic crystal structure based on spherical silica was formed to provide structural color using an electro-hydrodynamic (EHD) equipment, a printed electronic system attracting considerable interest. The EHD inkjet printing equipment could print micro- and nanostructures using the voltage applied between the nozzle and substrate. Silica-based ink samples were prepared for use in the EHD equipment. Appropriate printing parameters for the EHD inkjet printing were set using the prepared sample. Spherical silica was printed on a polyimide (PI) film layer. The spherical silica nanoparticles discharged during the EHD inkjet printing were not deformed by the EHD process. A photonic crystal structure was formed on a polydimethylsiloxane (PDMS) layer by EHD printing by covering the PDMS layer on the PI film. The spherical-silica-based photonic crystal structure formed on the PDMS layer with elasticity and flexibility exhibited a color change with bending loads.
Investigation on Chalcogenide Glass Additive Manufacturing for Shaping Mid-infrared Optical Components and Microstructured Optical Fibers
Authors: Carcreff Julie , Cheviré François , Lebullenger Ronan , Gautier Antoine , Chahal Radwan , Adam Jean Luc , Calvez Laurent , Brilland Laurent , Galdo Elodie , Le Coq David , Renversez Gilles , Troles Johann
Published: February 2021

In this work, an original way of shaping chalcogenide optical components has been investigated. Thorough evaluation of the properties of chalcogenide glasses before and after 3D printing has been carried out in order to determine the impact of the 3D additive manufacturing process on the material. In order to evaluate the potential of such additive glass manufacturing, several preliminary results obtained with various chalcogenide objects and components, such as cylinders, beads, drawing preforms and sensors, are described and discussed. This innovative 3D printing method opens the way for many applications involving chalcogenide fiber elaboration, but also many other chalcogenide glass optical devices.
Use of Recycled Concrete Aggregates in Production of Green Cement-Based Concrete Composites: A Review
Authors: Makul Natt , Fediuk Roman , Amran Mugahed , Zeyad Abdullah M. , Murali Gunasekaran , Vatin Nikolai , Klyuev Sergey , Ozbakkaloglu Togay , Vasilev Yuriy
Published: February 2021

Recycled concrete aggregates (RCA) are used in existing green building composites to promote the environmental preservation of natural coarse aggregates (NCA). Besides, the use of RCA leads to potential solutions to the social and economic problems caused by concrete waste. It is found that insufficient information on the longevity and sustainability of RCA production is a serious issue that requires close attention due to its impact on changing aspects of the sector. However, more attention has been paid to explaining the effect of RCA on concrete durability, as well as the properties of fresh and hardened concrete. Therefore, this study aims to provide a critical review on the RCAs for the production of high-performances concrete structures. It begins by reviewing the source, originality, types, prediction of service life, features and properties of RCA, as well as the effect of RCA on concrete performance. In addition, this literature review summarizes the research findings to produce complete insights into the potential applications of RCA as raw, renewable, and sustainable building materials for producing greener concrete composite towards industrializing ecofriendly buildings today. Further, it has also highlighted the differences in the current state of knowledge between RCAs and NCAs, and offers several future research suggestions. Through this critical and analytical study, it can be said that RCA has the possible use in the production of high-performance structural concrete depending on the source and type of recycled aggregate while the RCA can be used widely and safely to produce traditional green concrete.
Synthesis, Photophysical, and Computational Studies of a Bridged IrΙΙΙ-PtΙΙ Heterodimetallic Complex
Authors: Wu Si-Hai , Ma Dian-Xue , Gong Zhong-Liang , Ma Junjie , Shao Jiang-Yang , Yang Rong , Zhong Yu-Wu
Published: February 2021

An IrIII-PtII heterodimetallic complex [(ppy)2Ir(dapz)PtCl2]Cl (4), together with the corresponding monometallic complexes [(dapz)PtCl2] (2) and [(ppy)2Ir(dapz)]Cl (3) was designed and prepared, where dapz is 2,5-di(N-methyl-N′-(pyrid-2-yl)amino)pyrazine and ppy is 2-phenylpyridine, respectively. Single-crystal X-ray analysis was carried out for complex 4, displaying the intermolecular Pt∙∙∙Pt and aromatic plane∙∙∙plane distances of 3.839 and 3.886 Å, respectively. The monometallic complex 2 exhibits a single emission maximum at 432 nm with a shorter excited-state lifetime (τ) of 6 ns, while complex 3 exhibits an emission band at 454 nm with a longer excited-state lifetime of 135 ns in CH3CN (N2-saturated) under ambient conditions. In contrast, the heterodimetallic complex 4 displays intriguing excitation wavelength-dependent dual singlet and triplet emissions. Theoretical calculations of the electronic structures and absorption spectra of these complexes were carried out to assist the interpretation of these experimental findings.
Higher Efficiency of Percutaneous Microwave (MWA) Than Radiofrequency Ablation (RFA) in Achieving Complete Response in Cirrhotic Patients with Early Hepatocellular Carcinoma
Authors: Gaia Silvia , Ciruolo Michela , Ribaldone Davide Giuseppe , Rolle Emanuela , Migliore Enrica , Mosso Elena , Vola Simone , Risso Alessandra , Fagoonee Sharmila , Saracco Giorgio Maria , Carucci Patrizia
Published: February 2021

Background: Contrasting data are available in the literature regarding the superiority of percutaneous microwave ablation (MWA) or radiofrequency ablation (RFA) in very early or early (BCLA 0 or A) hepatocellular carcinoma (HCC). Aims: The primary outcome was to compare the efficacy of RFA and MWA in achieving complete response in cirrhotic patients with early and very early HCC. The secondary outcomes were to evaluate the overall survival and the recurrence rate. Methods: A retrospective, observational, single-center study was performed. Inclusion criteria were liver cirrhosis, new diagnosis of a single node of HCC measuring a maximum of 50 mm or up to three nodules with diameter up to 35 mm, treatment with RFA or MWA. Radiological response was evaluated with multiphasic contrast-enhanced Computed Tomography or Magnetic Resonance Imaging at 5–7 weeks after thermal ablation. Complete response was defined when no vital tissue was detected after treatment. Results: Overall, 251 HCC patients were included in this study; 81 patients were treated with MWA and 170 with RFA. The complete response rate was similar in MWA and RFA groups (out of 331 nodules, 87.5% (91/104) were treated with MWA and 84.2% (186/221) were treated with RFA, p = 0.504). Interestingly, a subanalysis demonstrated that for 21–35 mm nodules, the probability to achieve a complete response using MWA was almost 5 times higher than for RFA (OR = 4.88, 95% CI 1.37–17.31, p = 0.014). Moreover, recurrence rate in 21–35 mm nodules was higher with RFA with respect to MWA (31.9% versus 13.5%, p = 0.019). Overall survival was 80.4% (45/56) when treated with MWA and 62.2% (56/90) when treated with RFA (p = 0.027). No significant difference was observed between MWA and RFA treatment in the 15–20 mm nodules group. Conclusion: This study showed that MWA is more efficient than RFA in achieving complete response in HCC nodules with 21 to 35 mm diameter.
The Influence of Work Environment Factors on the Ocular Surface in a One-Year Follow-Up Prospective Clinical Study
Authors: Chlasta-Twardzik Edyta , Górecka-Nitoń Aleksandra , Nowińska Anna , Wylęgała Edward
Published: February 2021

The purpose of this study was to assess the effect of environmental working conditions on the symptoms and signs of dry eye disease and to examine whether and how those conditions impact the ocular surface. Methods: This single-center, prospective clinical study with a 1-year follow-up included 150 patients. The following parameters were evaluated: non-invasive keratograph break-up time (NIKBUT), tear meniscus height (TMH), and conjunctival and limbal hyperemia. We also performed staining of the surface of the eye for simulated fluorescein images, Schirmer’s test I, assessment of Meibomian gland dysfunction (MGD), and an Ocular Surface Disease Index (OSDI) questionnaire. Results: In the OW (office workers) group, in people working >4 h at the computer, the NIKBUT before work and the Schirmer test results were statistically significantly lower than in people working <4 h. The conjunctival hyperemia result before work was statistically significantly higher for people working >4 h at a computer in both groups and after work in the MW (medical workers) group. Low relative air humidity in the building and air-conditioned rooms negatively affects the tear film, causing the symptoms of dry eye disease. At the 1-year follow-up, there was a statistically significant reduction in conjunctival and limbal hyperemia in the OW group as well as a statistically significant reduction in TMH at the first examination before and after work, and in the second examination after 1 year in both groups. Conclusions: Environmental factors such as reduced relative air humidity, increased air temperature, and decreased illumination have a negative impact on the ocular surface.
Prenatal Biochemical and Ultrasound Markers in COVID-19 Pregnant Patients: A Prospective Case-Control Study
Authors: Cosma Stefano , Carosso Andrea Roberto , Borella Fulvio , Cusato Jessica , Bovetti Marialuisa , Bevilacqua Federica , Carosso Marco , Gervasoni Fiammetta , Sciarrone Andrea , Marozio Luca , Revelli Alberto , Rolfo Alessandro , Filippini Claudia , Ghisetti Valeria , Di Perri Giovanni , Benedetto Chiara
Published: February 2021

This prospective observational study aimed to evaluate whether women with SARS-CoV-2 infection during the first trimester of pregnancy are at higher risk of noninvasive prenatal screening test alterations and/or of congenital fetal anomalies at the second-trimester fetal anatomy scan. Maternal symptoms were secondly investigated. The study was carried out on 12-week pregnant women admitted for noninvasive prenatal testing (16 April and 22 June 2020). The cohort had seromolecular tests for SARS-CoV-2, after which they were divided into a positive case group and a negative control group. Both groups had 20-week ultrasound screening. Seventeen out of the 164 women tested positive for SARS-CoV-2 (10.3%). There were no significant differences in mean nuchal translucency thickness or biochemical markers (pregnancy-associated plasma protein A, alpha-fetoprotein, human chorionic gonadotropin, unconjugated estriol) between cases and controls (p = 0.77, 0.63, 0.30, 0.40, 0.28) or in the fetal incidence of structural anomalies at the second-trimester fetal anatomy scan (p = 0.21). No pneumonia or hospital admission due to COVID-19-related symptoms were observed. Asymptomatic or mildly symptomatic SARS-CoV-2 infection during the first trimester of pregnancy did not predispose affected women to more fetal anomalies than unaffected women. COVID-19 had a favorable maternal course at the beginning of pregnancy in our healthy cohort.
Implementation of a Pilot Elementary Mathematics Specialist Endorsement Program
Authors: Henrikson Robin , Lumpe Andrew
Published: February 2021

We present the results of a mixed methods study focusing on the implementation of a pilot elementary mathematics specialist (EMS) endorsement program implemented in partnership with the several educational organizations to provide teachers in high needs rural areas an opportunity to earn the EMS endorsement through coursework and instructional leadership experiences. The data presented draw from social cognitive theory and andragogy to describe the experiences of the EMS candidates throughout their endorsement program and to provide recommendations for programmatic improvements. We sought to explore ways in which the EMS candidates’ experiences within the program and school-based internship impacted their levels of self-efficacy and perceived success within the program. We also sought to determine the opportunities and barriers that exist with the EMS candidates’ respective learning environments as they implemented professional learning plans with a core set of teachers they collaborated with to improve mathematics instruction. The results of this study indicate that both EMS candidates and the teachers they worked with increased their levels of mathematics content knowledge. EMS candidates also improved their levels of self-efficacy regarding mathematics teaching and leadership skills. Furthermore, both EMS candidates and their core set of teachers improved in time spent focused on ongoing professional learning activities. Recommendations include a need to support teachers as they expand their role into instruction as well as equip school leaders to ensure they can support teacher leadership candidates in their professional growth.
D-PARK: User-Centric Smart Parking System over BLE-Beacon Based Internet of Things
Authors: Park Soochang
Published: February 2021

Our daily life services are quickly becoming smarter with intelligence and information through artificial intelligence (AI) and Big Data technologies. Parking services are one of the most frequently used in our daily life-cycle. This parking application could be classified into several features according to demands and properties, such as parking capacity balancing on a city-level view, parking fee maximization for achieving the service provider demand, empty parking spot notification within a parking lot, etc. This paper concentrates on parking space detection and alert to users. Most smart services rely on smart mobile derives of users such as smartphones and smartwatches. The proposed novel mechanism for smart parking is based on a smart device to gather mobile sensing data such as users’ activity and position data. Acquired mobile data are analyzed via machine learning technologies to provide dedicated parking services per user. Based on real testbed setups on campus and the proof-of-concept implementation, the proposed localization can achieve accuracy of a parking spot scale (2m-second guess 95%); moreover, it shows a much lower service operation period of 6.8 times (34s) than the legacy approach (230s).
Coordinated Multi-Agent Deep Reinforcement Learning for Energy-Aware UAV-Based Big-Data Platforms
Authors: Jung Soyi , Yun Won Joon , Kim Joongheon , Kim Jae-Hyun
Published: February 2021

This paper proposes a novel coordinated multi-agent deep reinforcement learning (MADRL) algorithm for energy sharing among multiple unmanned aerial vehicles (UAVs) in order to conduct big-data processing in a distributed manner. For realizing UAV-assisted aerial surveillance or flexible mobile cellular services, robust wireless charging mechanisms are essential for delivering energy sources from charging towers (i.e., charging infrastructure) to their associated UAVs for seamless operations of autonomous UAVs in the sky. In order to actively and intelligently manage the energy resources in charging towers, a MADRL-based coordinated energy management system is desired and proposed for energy resource sharing among charging towers. When the required energy for charging UAVs is not enough in charging towers, the energy purchase from utility company (i.e., energy source provider in local energy market) is desired, which takes high costs. Therefore, the main objective of our proposed coordinated MADRL-based energy sharing learning algorithm is minimizing energy purchase from external utility companies to minimize system-operational costs. Finally, our performance evaluation results verify that the proposed coordinated MADRL-based algorithm achieves desired performance improvements.
Multi-UAV Enabled Data Collection with Efficient Joint Adaptive Interference Management and Trajectory Design
Authors: Pi Weichao , Zhou Jianming
Published: February 2021

This paper studies interference in a data collection scenario in which multiple unmanned aerial vehicles (UAVs) are dispatched to wirelessly collect data from a set of distributed sensors. To improve the communication throughput and minimize the completion time, we design a joint resource allocation and trajectory optimization framework that not only is compatible with the traditional time-division scheme and interference coordination scheme but also combines their advantages. First, we analyse a basic quasi-stationary scenario with two UAVs and four devices, in which the two UAVs hover at optimal displacements to execute the data collection mission, and it is proven that the proposed optimal resource allocation and trajectory solution is adaptively adjustable according to the severity of the interference and that the common throughput of the network is non-decreasing. Second, for the general mobile case, we design an efficient algorithm to jointly address resource allocation and trajectory optimization, in which we first apply the block coordinate descent method to decompose the original non-convex problem into three non-convex sub-problems and then employ a dedicated genetic algorithm, a penalty function and the sequential convex approximation (SCA) technique to efficiently solve the individual sub-problems and obtain a satisfactory locally optimal solution with an adaptive initialization scheme. Subsequently, numerical experiments are presented to demonstrate that the completion time of the data collection task with our proposed method is at least 25% shorter than those with several baseline dynamic orthogonal schemes when 4 UAVs are deployed. Finally, we provide a practical application principle concerning the maximum suitable number of UAVs to avoid the inherent deficiencies of the proposed algorithm.
Traffic Police Gesture Recognition Based on Gesture Skeleton Extractor and Multichannel Dilated Graph Convolution Network
Authors: Xiong Xin , Wu Haoyuan , Min Weidong , Xu Jianqiang , Fu Qiyan , Peng Chunjiang
Published: February 2021

Traffic police gesture recognition is important in automatic driving. Most existing traffic police gesture recognition methods extract pixel-level features from RGB images which are uninterpretable because of a lack of gesture skeleton features and may result in inaccurate recognition due to background noise. Existing deep learning methods are not suitable for handling gesture skeleton features because they ignore the inevitable connection between skeleton joint coordinate information and gestures. To alleviate the aforementioned issues, a traffic police gesture recognition method based on a gesture skeleton extractor (GSE) and a multichannel dilated graph convolution network (MD-GCN) is proposed. To extract discriminative and interpretable gesture skeleton coordinate information, a GSE is proposed to extract skeleton coordinate information and remove redundant skeleton joints and bones. In the gesture discrimination stage, GSE-based features are introduced into the proposed MD-GCN. The MD-GCN constructs a graph convolution with a multichannel dilated to enlarge the receptive field, which extracts body topological and spatiotemporal action features from skeleton coordinates. Comparison experiments with state-of-the-art methods were conducted on a public dataset. The results show that the proposed method achieves an accuracy rate of 98.95%, which is the best and at least 6% higher than that of the other methods.
Use and Adaptations of Machine Learning in Big Data—Applications in Real Cases in Agriculture
Authors: Cravero Ania , Sepúlveda Samuel
Published: February 2021

The data generated in modern agricultural operations are provided by diverse elements, which allow a better understanding of the dynamic conditions of the crop, soil and climate, which indicates that these processes will be increasingly data-driven. Big Data and Machine Learning (ML) have emerged as high-performance computing technologies to create new opportunities to unravel, quantify and understand agricultural processes through data. However, there are many challenges to achieve the integration of these technologies. It implies making some adaptations to ML for using it with Big Data. These adaptations must consider the increasing volume of data, its variety and the transmission speed issues. This paper provides information on the use of Big Data and ML for agriculture, identifying challenges, adaptations and the design of architectures for these systems. We conducted a Systematic Literature Review (SLR), which allowed us to analyze 34 real cases applied in agriculture. This review may be of interest to computer or data scientists and electronic or software engineers. The results show that manipulating large volumes of data is no longer a challenge due to Cloud technologies. There are still challenges regarding (1) processing speed due to little control of the data in its different stages, raw, semi-processed and processed data (value data); (2) information visualization systems, which support technical data little understood by farmers.
Design of Cut Off-Frequency Fixing Filters by Error Compensation of MAXFLAT FIR Filters
Authors: Chung Daewon , Cho Woon , Jeong Inyeob , Jeon Joonhyeon
Published: February 2021

Maximally-flat (MAXFLAT) finite impulse response (FIR) filters often face a problem of the cutoff-frequency error due to approximation of the desired frequency response by some closed-form solution. So far, there have been plenty of efforts to design such a filter with an arbitrarily specified cut off-frequency, but this filter type requires extensive computation and is not MAXFLAT anymore. Thus, a computationally efficient and effective design is needed for highly accurate filters with desired frequency characteristics. This paper describes a new method for designing cutoff-frequency-fixing FIR filters through the cutoff-frequency error compensation of MAXFLAT FIR filters. The proposed method provides a closed-form Chebyshev polynomial containing a cutoff-error compensation function, which can characterize the “cutoff-error-free” filters in terms of the degree of flatness for a given order of filter and cut off-frequency. This method also allows a computationally efficient and accurate formula to directly determine the degree of flatness, so that this filter type has a flat magnitude characteristic both in the passband and the stopband. The remarkable effectiveness of the proposed method in design efficiency and accuracy is clearly demonstrated through various examples, indicating that the cutoff-fixing filters exhibit amplitude distortion error of less than 10−14 and no cut off-frequency error. This new approach is shown to provide significant advantages over the previous works in design flexibility and accuracy.
Thermally Conductive Backsheets (TCB) of PV Modules: Positive Impacts on Performance, Lifetime and LCOE
Authors: Pavgi Ashwini , Oh Jaewon , TamizhMani GovindaSamy
Published: February 2021

The operating temperatures of photovoltaic (PV) modules can be impacted by the selection of specific packaging materials, e.g., backsheets and encapsulants. This research focuses on the evaluation of operating temperature reduction of one-cell modules by comparing conventional Tedlar/polyester/Tedlar (TPT) backsheet with novel thermally conductive backsheets (TCBs) materials. A large number of one-cell modules with two TCB types (TCB_A and TCB_B) and baseline TPT type were fabricated and installed in three different climatic conditions of the hot-dry desert in Arizona (high and low wind speed locations) and North Carolina (temperate with low wind speed location). In this study, these two TCBs were compared with conventional TPT backsheet in terms of performance, lifetime and levelized cost of energy (LCOE). The field results were analyzed for thermal performance of TCBs compared to TPT at three sites for two and half years. This study concludes that the thermal and electrical performances of the PV modules can be improved by using TCB_A in hot and dry climate sites and TCB_B at temperate climate sites. Therefore, the lifetime of TCB-based modules is expected to be higher than TPT-based modules. Using backsheet-specific power degradation levels and assuming the same cost for both types of backsheets, the LCOE of modules using TCBs is estimated to be lower than that of TPT.
SlurryNet: Predicting Critical Velocities and Frictional Pressure Drops in Oilfield Suspension Flows
Authors: Sarraf Shirazi Alireza , Frigaard Ian
Published: February 2021

Improving the accuracy of the slurry flow predictions in different operating flow regimes remains a major focus for multiphase flow research, and it is especially targeted at industrial applications such as oil and gas. In this paper we develop a robust integrated method consisting of an artificial neural network (ANN) and support vector regression (SVR) to estimate the critical velocity, the slurry flow regime change, and ultimately, the frictional pressure drop for a solid–liquid slurry flow in a horizontal pipe, covering wide ranges of flow and geometrical parameters. Three distinct datasets were used to develop machine learning models with totals of 100, 325, and 125 data points for critical velocity, and frictional pressure drops for heterogeneous and bed-load regimes respectively. For each dataset, 80% of the data were used for training and the rest 20% for evaluating the out of sample performance. The K-fold technique was used for cross-validation. The prediction results of the developed integrated method showed that it significantly outperforms the widely used existing correlations and models in the literature. Additionally, the proposed integrated method with the average absolute relative error (AARE) of 0.084 outperformed the model developed without regime classification with the AARE of 0.155. The proposed integrated model not only offers reliable predictions over a wide range of operating conditions and different flow regimes for the first time, but also introduces a general framework of how to utilize prior physical knowledge to achieve more reliable performances from machine learning methods.
An Experimental Study on the Characteristics of NOx Distributions at the SNCR Inlets of a Large-Scale CFB Boiler
Authors: Yan Jin , Lu Xiaofeng , Zhang Changfei , Li Qianjun , Wang Jinping , Liu Shirong , Zheng Xiong , Fan Xuchen
Published: February 2021

The unknown NOx distributions inside large-scale CFB (circulating fluidized bed) boilers have always hindered the economy of the SNCR (selective non-catalytic reduction) process. In this study, field tests were carried out on a typical 300 MW CFB boiler, where multi-level 316 L-made probe and Ecom-J2KN/Testo 350 analyzers were used to perform detailed two-dimensional distributions of flue gas composition at SNCR inlets for the first time. The penetration depth inside the horizontal flue pass was up to 7 m. The NOx distributions were analyzed in detail combining with the auxiliary test in the dilute phase zone. Key results show that the average O2 concentrations in #A and #C regions were 6.52% and 0.95%, respectively. The vertical NOx distributions of #A and #C SNCR inlets were similar, showing a trend of first increasing and then decreasing with peak value all appeared at 5 m depth, while the NOx distribution of #B SNCR inlet was basically increasing. Some local areas with extremely high NOx concentration (over 2000 mg/m3) were observed near the inclined edge of SNCR inlets, which has never been reported before. Based on this, the optimization of urea injections was conducted, which could save 15.7% of the urea solution consumption while ensuring ultra-low emission of NOx.
On the Predictability of China Macro Indicator with Carbon Emissions Trading
Authors: Chen Qian , Gao Xiang , Xie Shan , Sun Li , Tian Shuairu , Hamori Shigeyuki
Published: February 2021

Accurate and timely macro forecasting requires new and powerful predictors. Carbon emissions data with high trading frequency and short releasing lag could play such a role under the framework of mixed data sampling regression techniques. This paper explores the China case in this regard. We find that our multiple autoregressive distributed lag model with mixed data sampling method setup outperforms either the auto-regressive or autoregressive distributed lag benchmark in both in-sample and out-of-sample nowcasting for not only the monthly changes of the purchasing managers’ index in China but also the Chinese quarterly GDP growth. Moreover, it is demonstrated that such capability operates better in nowcasting than h-step ahead forecasting, and remains prominent even after we account for commonly-used macroeconomic predictive factors. The underlying mechanism lies in the critical connection between the demand for carbon emission in excess of the expected quota and the production expansion decision of manufacturers.
Influence of Water Saturation, Grain Size of Quartz Sand and Hydrate-Former on the Gas Hydrate Formation
Authors: Zaripova Yulia , Yarkovoi Vladimir , Varfolomeev Mikhail , Kadyrov Rail , Stoporev Andrey
Published: February 2021

The development of technologies for the accelerated formation or decomposition of gas hydrates is an urgent topic. This will make it possible to utilize a gas, including associated petroleum one, into a hydrate state for its further use or to produce natural gas from hydrate-saturated sediments. In this work, the effect of water content in wide range (0.7–50 mass%) and the size of quartz sand particles (porous medium; <50 μm, 125–160 μm and unsifted sand) on the formation of methane and methane-propane hydrates at close conditions (subcooling value) has been studied. High-pressure differential scanning calorimetry and X-ray computed tomography techniques were employed to analyze the hydrate formation process and pore sizes, respectively. The exponential growth of water to hydrate conversion with a decrease in the water content due to the rise of water–gas surface available for hydrate formation was revealed. Sieving the quartz sand resulted in a significant increase in water to hydrate conversion (59% for original sand compared to more than 90% for sieved sand). It was supposed that water suction due to the capillary forces influences both methane and methane-propane hydrates formation as well with latent hydrate forming up to 60% either without a detectable heat flow or during the ice melting. This emphasizes the importance of being developed for water–gas (ice–gas) interface to effectively transform water into the hydrate state. In any case, the ice melting (presence of thawing water) may allow a higher conversion degree. Varying the water content and the sand grain size allows to control the degree of water to hydrate conversion and subcooling achieved before the hydrate formation. Taking into account experimental error, the equilibrium conditions of hydrates formation do not change in all studied cases. The data obtained can be useful in developing a method for obtaining hydrates under static conditions.
Intensification of Processes for the Production of Ethyl Levulinate Using AlCl3·6H2O
Authors: Pastore Carlo , D’Ambrosio Valeria
Published: February 2021

A process for obtaining ethyl levulinate through the direct esterification of levulinic acid and ethanol using AlCl3·6H2O as a catalyst was investigated. AlCl3·6H2O was very active in promoting the reaction and, the correspondent kinetic and thermodynamic data were determined. The reaction followed a homogeneous second-order reversible reaction model: in the temperature range of 318–348 K, Ea was 56.3 kJ·K−1·mol−1, whereas Keq was in the field 2.37–3.31. The activity of AlCl3·6H2O was comparable to that of conventional mineral acids. Besides, AlCl3·6H2O also induced a separation of phases in which ethyl levulinate resulted mainly (>98 wt%) dissolved into the organic upper layer, well separated by most of the co-formed water, which decanted in the bottom. The catalyst resulted wholly dissolved into the aqueous phase (>95 wt%), allowing at the end of a reaction cycle, complete recovery, and possible reuse for several runs. With the increase of the AlCl3·6H2O content (from 1 to 5 mol%), the reaction proceeded fast, and the phases’ separation improved. Such a behavior eventually results in an intensification of processes of reaction and separation of products and catalyst in a single step. The use of AlCl3·6H2O leads to a significant reduction of energy consumed for the final achievement of ethyl levulinate, and a simplification of line-processes can be achieved.
Stakeholders’ Analysis of Environmental Sustainability in Urban Logistics: A Case Study of Tricity, Poland
Authors: Rześny-Cieplińska Jagienka , Szmelter-Jarosz Agnieszka
Published: February 2021

Environmental sustainability, defined as the responsibility to protect the global ecosystem in a holistic way, has become an integral factor of city strategies. Designing and implementing environment-friendly solutions to make the standard of living in cities better is indispensable for present and future generations. This article’s main objective is to identify the most environmentally friendly urban logistics measures from the perspective of urban transport system stakeholders. A multi-method approach was implemented to achieve the article’s main findings. Firstly, the literature review provided the basics for designing the research framework. Then, a three-layer methodological approach was used: The first layer included designing and carrying out the case study approach; the second layer comprised a Delphi study involving interviews with urban logistics stakeholders; and the third layer included analyzing the voices of Delphi interviewees to assess which urban logistics measures are the most important for them. The study provides an initial insight into the opinions of stakeholders for a general audience, but at the same time, also presents specific, detailed views of Tricity urban space users and decision-makers. Significant differences in opinions were observed and confirmed in the interviewed group. This study can contribute to the scientific discussion about the stakeholders’ analysis of urban logistics goals.
Progress in Material Development for Low-Temperature Solid Oxide Fuel Cells: A Review
Authors: Fallah Vostakola Mohsen , Amini Horri Bahman
Published: February 2021

Solid oxide fuel cells (SOFCs) have been considered as promising candidates to tackle the need for sustainable and efficient energy conversion devices. However, the current operating temperature of SOFCs poses critical challenges relating to the costs of fabrication and materials selection. To overcome these issues, many attempts have been made by the SOFC research and manufacturing communities for lowering the operating temperature to intermediate ranges (600–800 °C) and even lower temperatures (below 600 °C). Despite the interesting success and technical advantages obtained with the low-temperature SOFC, on the other hand, the cell operation at low temperature could noticeably increase the electrolyte ohmic loss and the polarization losses of the electrode that cause a decrease in the overall cell performance and energy conversion efficiency. In addition, the electrolyte ionic conductivity exponentially decreases with a decrease in operating temperature based on the Arrhenius conduction equation for semiconductors. To address these challenges, a variety of materials and fabrication methods have been developed in the past few years which are the subject of this critical review. Therefore, this paper focuses on the recent advances in the development of new low-temperature SOFCs materials, especially low-temperature electrolytes and electrodes with improved electrochemical properties, as well as summarizing the matching current collectors and sealants for the low-temperature region. Different strategies for improving the cell efficiency, the impact of operating variables on the performance of SOFCs, and the available choice of stack designs, as well as the costing factors, operational limits, and performance prospects, have been briefly summarized in this work.
Validated Analytical Modeling of Diesel Engines Intake Manifold with a Flexible Crankshaft
Authors: Elmoselhy Salah A. M. , Faris Waleed F. , Rakha Hesham A.
Published: February 2021

The flexibility of a crankshaft exhibits significant nonlinearities in the analysis of diesel engines performance, particularly at rotational speeds of around 2000 rpm. Given the explainable mathematical trends of the analytical model and the lack of available analytical modeling of the diesel engines intake manifold with a flexible crankshaft, the present study develops and validates such a model. In the present paper, the mass flow rate of air that goes from intake manifold into all the cylinders of the engine with a flexible crankshaft has been analytically modeled. The analytical models of the mass flow rate of air and gas speed dynamics have been validated using case studies and the ORNL and EPA Freeway standard drive cycles showing a relative error of 7.5% and 11%, respectively. Such values of relative error are on average less than those of widely recognized models in this field, such as the GT-Power and the CMEM, respectively. A simplified version for control applications of the developed models has been developed based on a sensitivity analysis. It has been found that the flexibility of a crankshaft decreases the mass flow rate of air that goes into cylinders, resulting in an unfavorable higher rate of exhaust emissions like CO. It has also been found that the pressure of the gas inside the cylinder during the intake stroke has four elements: a driving element (intake manifold pressure) and draining elements (vacuum pressure and flow losses and inertial effect of rotating mass). The element of the least effect amongst these four elements is the vacuum pressure that results from the piston’s inertia and acceleration. The element of the largest effect is the pressure drop that takes place in the cylinder because of the air/gas flow losses. These developed models are explainable and widely valid so that they can help in better analyzing the performance of diesel engines.
Coordination of Lateral Vehicle Control Systems Using Learning-Based Strategies
Authors: Németh Balázs
Published: February 2021

The paper proposes a novel learning-based coordination strategy for lateral control systems of automated vehicles. The motivation of the research is to improve the performance level of the coordinated system compared to the conventional model-based reconfigurable solutions. During vehicle maneuvers, the coordinated control system provides torque vectoring and front-wheel steering angle in order to guarantee the various lateral dynamical performances. The performance specifications are guaranteed on two levels, i.e., primary performances are guaranteed by Linear Parameter Varying (LPV) controllers, while secondary performances (e.g., economy and comfort) are maintained by a reinforcement-learning-based (RL) controller. The coordination of the control systems is carried out by a supervisor. The effectiveness of the proposed coordinated control system is illustrated through high velocity vehicle maneuvers.
Factors Influencing the Preventive Practice of International Students in South Korea against COVID-19 during the Pandemic
Authors: Jang Gun Ja , Jang Ginam , Ko Sangjin
Published: February 2021

As the novel coronavirus disease (COVID-19) spreads worldwide, quarantine guidelines are being constantly updating to prevent the transmission of this virus. Regardless of which country international students live in, they might receive limited crucial quarantine guidelines from that country’s government. The purpose of this study was to identify factors influencing the preventive practice of international students in South Korea during the COVID-19 pandemic. This was a cross-sectional descriptive study. Data were collected from international students in three universities from July 10 to July 31 in 2020. A total of 261 international students participated in the survey, using an online questionnaire. Data were analyzed by independent t-test, one-way ANOVA, Pearson correlation coefficients, and multiple regression analysis. Preventive practice during the COVID-19 pandemic was affected by duration of stay in Korea (β = −0.21, p < 0.001), attitudes (β = 0.22, p = 0.001), and trust in Korea’s quarantine system (β = 0.33, p < 0.001). This study showed that attitudes and trust in the quarantine system could affect personal preventive practice during the outbreak of a highly contagious disease such as COVID-19.
Indol-3-Carbinol and Quercetin Ameliorate Chronic DSS-Induced Colitis in C57BL/6 Mice by AhR-Mediated Anti-Inflammatory Mechanisms
Authors: Riemschneider Sina , Hoffmann Maximilian , Slanina Ulla , Weber Klaus , Hauschildt Sunna , Lehmann Jörg
Published: February 2021

Inflammatory bowel diseases (IBD), such as Crohn’s disease and ulcerative colitis, are multifactorial inflammatory disorders of the gastrointestinal tract, characterised by abdominal cramps, bloody diarrhoea, and anaemia. Standard therapies, including corticosteroids or biologicals, often induce severe side effects, or patients may develop resistance to those therapies. Thus, new therapeutic options for IBD are urgently needed. This study investigates the therapeutic efficacy and safety of two plant-derived ligands of the aryl hydrocarbon receptor (AhR), quercetin (Q), and indol-3-carbinol (I3C), using a translationally relevant mouse model of IBD. Q and I3C are administered by gavage to C57BL/6 wild-type or C57BL/6 Ahr-/- mice suffering from chronic colitis, induced by dextran sulphate sodium (DSS). The course of the disease, intestinal histopathological changes, and in-situ immunological phenotype are scored over 25 days. Our results show that both Q and I3C improved significantly clinical symptoms in moderate DSS colitis, which coincides with a significantly reduced histopathological score. Even in severe DSS colitis I3C, neither Q nor the therapy control 6-thioguanine (6-TG) can prevent a fatal outcome. Moreover, treatment with Q or I3C restored in part DSS-induced loss of epithelial integrity by induction of tight-junction proteins and reduced significantly gut inflammation, as demonstrated by colonoscopy, as well as by immunohistochemistry revealing lower numbers of neutrophils and macrophages. Moreover, the number of Th17 cells is significantly reduced, while the number of Treg cells is significantly increased by treatment with Q or I3C, as well as 6-TG. Q- or I3C-induced amelioration of colitis is not observed in Ahr-/- mice suggesting the requirement of AhR ligation and signalling. Based on the results of this study, plant-derived non-toxic AhR agonists can be considered promising therapeutics in IBD therapy in humans. However, they may differ in terms of efficacy; therefore, it is indispensable to study the dose-response relationship of each individual AhR agonist also with regard to potential adverse effects, since they may also exert AhR-independent effects.