bluuebunny/crossref_metadata_2025 huggingface dataset:
Lower Respiratory Tract Pathogens and Their Antimicrobial Susceptibility Pattern: A 5-Year Study
Authors: Santella Biagio , Serretiello Enrica , De Filippis Anna , Folliero Veronica , Iervolino Domenico , Dell’Annunziata Federica , Manente Roberta , Valitutti Francesco , Santoro Emanuela , Pagliano Pasquale , Galdiero Massimiliano , Boccia Giovanni , Franci Gianluigi
Published: July 2021

Lower respiratory tract infections (LRTIs) are the most common infections in humans. It is estimated that 2.74 million deaths worldwide occur each year due to LRTIs. The aim of the study was to determine the frequency and antibiotic susceptibility pattern of microorganisms isolated from respiratory samples of patients with LRTIs. Between January 2015 and December 2019, a total of 7038 sputum and bronchoaspirate samples from suspected LRTI patients were collected. Among them, 2753 samples (39.1%) showed significant microbial growth on culture media. The LRTI rate was higher in patients with male gender (67.1%) and with age between 40–59 years (48.6%). The microorganism identification and antibiotic susceptibility testing were performed with Vitek 2. Out of 4278 isolates species, 3102 (72.5%) were Gram-negative bacteria, 1048 (24.5%) were Gram-positive bacteria, and 128 (3.0%) were Candida spp. Major microorganisms isolated were Acinetobacter baumannii (18.6%), Staphylococcus aureus (15.2%), Pseudomonas aeruginosa (14.2%), and Klebsiella pneumoniae (10.9%). In antimicrobial susceptibility testing, Staphylococcus aureus isolates were mostly resistant to Penicillin G (84.1%) and Oxacillin (48.1%), whereas they demonstrated maximum sensitivity to Tigecycline (100%) and Linezolid (99.5%). Among Gram-negative isolates, Acinetobacter baumannii showed maximum sensitivity to Colistin but was resistant to other antibiotics (95–99%). Klebsiella pneumoniae isolates were mostly resistant to Cefotaxime (72.7%) and sensitive to Gentamicin (54.3%), and Pseudomonas aeruginosa was resistant to Ciprofloxacin (40.3%) and sensitive to Amikacin (85.9%). Gram-negative bacteria represented the species most commonly isolated. A high rate of antimicrobial resistance was observed in this study. In conclusion, the correct identification of causative microorganisms and their susceptibility patterns to antibiotics is crucial for choosing targeted and effective antibiotic therapy in LRTIs, and to prevent the emergence of multidrug-resistant bacteria.
Potential Impact of the Involvement of Clinical Pharmacists in Antimicrobial Stewardship Programs on the Incidence of Antimicrobial-Related Adverse Events in Hospitalized Patients: A Multicenter Retrospective Study
Authors: Suh Yewon , Ah Young-Mi , Chun Ha-Jin , Lee Su-Mi , Kim Hyung-sook , Gu Hyun-Jun , Kim A-Jeong , Chung Jee-Eun , Cho Yoonsook , Lee Young-Hee , Hwangbo Shin-Yi , Kim Jeongmee , Kim Eu-Suk , Kim Hong-Bin , Lee Eunsook , Lee Ju-Yeun
Published: July 2021

Although specialized pharmacists have been suggested to be essential members of antimicrobial stewardship programs (ASPs), not all hospitals in Korea operate ASPs with pharmacists involved. We aimed to evaluate the association of involvement of clinical pharmacists as team members of multidisciplinary ASPs with the incidence of antimicrobial-related adverse drug events (ADEs). Five tertiary teaching hospitals participated in this retrospective cohort study. At each participating hospital, we randomly selected 1000 participants among patients who had received systemic antimicrobial agents for more than one day during the first quarter of 2017. We investigated five categories of antimicrobial-related ADEs: allergic reactions, hematologic toxicity, nephrotoxicity, hepatotoxicity, and antimicrobial-related diarrhea. Multivariate logistic regression analysis was used to evaluate the potential impact of pharmacist involvement in ASPs on the incidence of ADEs. A total of 1195 antimicrobial-related ADEs occurred in 618 (12.4%) of the 4995 patients included in the analysis. The overall rate of ADE occurrence was 17.4 per 1000 patient days. Hospitals operating ASPs with pharmacists showed significantly lower AE incidence proportions than other hospitals (8.9% vs. 14.7%; p < 0.001). Multidisciplinary ASPs that included clinical pharmacists reduced the risk of antimicrobial-related ADEs by 38% (adjusted odds ratio 0.62; 95% confidence interval 0.50–0.77). Our results suggest that the active involvement of clinical pharmacists in multidisciplinary ASPs may contribute to reduce the incidence of antimicrobial-related ADEs in hospitalized patients.
Novel Nitro-Heteroaromatic Antimicrobial Agents for the Control and Eradication of Biofilm-Forming Bacteria
Authors: Koenig Heidi N. , Durling Gregory M. , Walsh Danica J. , Livinghouse Tom , Stewart Philip S.
Published: July 2021

The synthesis and biological activity of several novel nitrothiazole, nitrobenzothiazole, and nitrofuran containing antimicrobial agents for the eradication of biofilm-forming Gram-negative and Gram-positive pathogens is described. Nitazoxanide (NTZ), nitrofurantoin, and furazolidone are commercial antimicrobials which were used as models to show how structural modification improved activity toward planktonic bacteria via minimum inhibitory concentration (MIC) assays and biofilms via minimum biofilm eradication concentration (MBEC) assays. Structure–activity relationship (SAR) studies illustrate the ways in which improvements have been made to the aforementioned antimicrobial agents. It is of particular interest in this regard that the introduction of a chloro substituent at the 5-position of NTZ (analog 1b) resulted in marked activity enhancement, as did the replacement of the 2-acetoxy substituent in the latter compound with a basic amine group (analog 7b). It is also of importance that analog 4a, which is a simple methacrylamide, displayed noteworthy activity against S. epidermidis biofilms. These lead compounds identified to have high activity towards biofilms provide promise as starting points in future pro-drug studies.
Failure of the Brain Glucagon-Like Peptide-1-Mediated Control of Intestinal Redox Homeostasis in a Rat Model of Sporadic Alzheimer’s Disease
Authors: Homolak Jan , Babic Perhoc Ana , Knezovic Ana , Osmanovic Barilar Jelena , Salkovic-Petrisic Melita
Published: July 2021

The gastrointestinal system may be involved in the etiopathogenesis of the insulin-resistant brain state (IRBS) and Alzheimer’s disease (AD). Gastrointestinal hormone glucagon-like peptide-1 (GLP-1) is being explored as a potential therapy as activation of brain GLP-1 receptors (GLP-1R) exerts neuroprotection and controls peripheral metabolism. Intracerebroventricular administration of streptozotocin (STZ-icv) is used to model IRBS and GLP-1 dyshomeostasis seems to be involved in the development of neuropathological changes. The aim was to explore (i) gastrointestinal homeostasis in the STZ-icv model (ii) assess whether the brain GLP-1 is involved in the regulation of gastrointestinal redox homeostasis and (iii) analyze whether brain-gut GLP-1 axis is functional in the STZ-icv animals. Acute intracerebroventricular treatment with exendin-3(9-39)amide was used for pharmacological inhibition of brain GLP-1R in the control and STZ-icv rats, and oxidative stress was assessed in plasma, duodenum and ileum. Acute inhibition of brain GLP-1R increased plasma oxidative stress. TBARS were increased, and low molecular weight thiols (LMWT), protein sulfhydryls (SH), and superoxide dismutase (SOD) were decreased in the duodenum, but not in the ileum of the controls. In the STZ-icv, TBARS and CAT were increased, LMWT and SH were decreased at baseline, and no further increment of oxidative stress was observed upon central GLP-1R inhibition. The presented results indicate that (i) oxidative stress is increased in the duodenum of the STZ-icv rat model of AD, (ii) brain GLP-1R signaling is involved in systemic redox regulation, (iii) brain-gut GLP-1 axis regulates duodenal, but not ileal redox homeostasis, and iv) brain-gut GLP-1 axis is dysfunctional in the STZ-icv model.
Modeling of Antioxidant Activity, Polyphenols and Macronutrients Content of Bee Pollen Applying Solid-State 13C NMR Spectra
Authors: Mazurek Sylwester , Szostak Roman , Kondratowicz Mateusz , Węglińska Magdalena , Kita Agnieszka , Nemś Agnieszka
Published: July 2021

An application of solid 13C nuclear magnetic resonance (NMR) spectroscopy for the determination of macronutrients, total polyphenols content, antioxidant activity, N C S elements, and pH in commercially available bee pollens is reported herein. Solid-state 13C NMR spectra were recorded for homogenized pollen granules without chemical treatment or dissolution of samples. By combining spectral data with the results of reference analyses, partial least squares models were constructed and validated separately for each of the studied parameters. To characterize and compare the models’ quality, the relative standard errors of prediction (RSEP) were calculated for calibration and validation sets. In the case of the analysis of protein, fat and reducing sugars, these errors were in the 1.8–2.5% range. Modeling the elemental composition of bee pollen on the basis of 13C NMR spectra resulted in RSEPcal/RSEPval values of 0.3/0.6% for the sum of NHCS elements, 0.3/0.4% for C, 1.8/1.9% for N, and 4.2/6.1% for S quantification. Analyses of total phenolics and ABTS antioxidant activity resulted in RSEP values in the 2.7–3.5% and 2.8–3.8% ranges, respectively, whereas they were 1.4–2.1% for pH. The obtained results demonstrate the usefulness of 13C solid-state NMR spectroscopy for direct determination of various important physiochemical parameters of bee pollen.
Comparative Study on Phenolic Content and Antioxidant Activity of Different Malt Types
Authors: Shopska Vesela , Denkova-Kostova Rositsa , Dzhivoderova-Zarcheva Mina , Teneva Desislava , Denev Petko , Kostov Georgi
Published: July 2021

Malt is the main raw material for beer production, which determines not only its taste and aroma profile, but to a large extent its biological value, as well. The aim of the present research was to determine the antioxidant profile of different malt types as a basis for the development of new types of beer with increased antioxidant activity. In the present study the main brewing characteristics, the phenolic profile and the antioxidant potential of 20 malt types used in craft breweries in Bulgaria have been examined. The main brewing characteristics have been determined by the standardized methods of the European Brewing Convention. Malt phenolic content was determined by two methods, and antioxidant potential by five different methods. Based on a statistical factor analysis performed by the principal component analysis, it was confirmed that there was a relationship between malt color and phenolic compounds content. The principal component analysis confirmed that there was a link between the content of the Maillard reaction products and malt biological activity. Malts with the highest degree of heat treatment were characterized by the highest antioxidant activity, which was due to the content of Maillard reaction products with antioxidant capacity.
Quercetin Alleviates the Accumulation of Superoxide in Sodium Iodate-Induced Retinal Autophagy by Regulating Mitochondrial Reactive Oxygen Species Homeostasis through Enhanced Deacetyl-SOD2 via the Nrf2-PGC-1α-Sirt1 Pathway
Authors: Hsu Min-Yen , Hsiao Yai-Ping , Lin Yu-Ta , Chen Connie , Lee Chee-Ming , Liao Wen-Chieh , Tsou Shang-Chun , Lin Hui-Wen , Chang Yuan-Yen
Published: July 2021

Oxidative damage of retinal pigment epithelium (RPE) cells plays an important role in the pathogenesis of blindness-related diseases, such as age-related macular degeneration (AMD). Quercetin, a bioactive flavonoid compound, has been shown to have a protective effect against oxidative stress-induced cell apoptosis and inflammation in RPE cells; however, the detailed mechanism underlying this protective effect is unclear. Therefore, the aim of this study was to investigate the regulatory mechanism of quercetin in a sodium iodate (NaIO3)-induced retinal damage. The clinical features of the mice, the production of oxidative stress, and the activity of autophagy and mitochondrial biogenesis were examined. In the mouse model, NaIO3 treatment caused changes in the retinal structure and reduced pupil constriction, and quercetin treatment reversed the oxidative stress-related pathology by decreasing the level of superoxide dismutase 2 (SOD2) while enhancing the serum levels of catalase and glutathione. The increased level of reactive oxygen species in the NaIO3-treated ARPE19 cells was improved by treatment with quercetin, accompanied by a reduction in autophagy and mitochondrial biogenesis. Our findings indicated that the effects of quercetin on regulating the generation of mtROS were dependent on increased levels of deacetyl-SOD2 through the Nrf2-PGC-1α-Sirt1 signaling pathway. These results demonstrated that quercetin may have potential therapeutic efficacy for the treatment of AMD through the regulation of mtROS homeostasis.
Modeling of Heat Phenomenon in Rolling Kinematic Pairs Using the Finite Element Method
Authors: Kosmol Jan
Published: July 2021

In the spindles of HSC (High Speed Cutting) machines with rolling bearings, higher temperatures in the bearings can be expected, which may affect the resistance to movement of the bearing itself. Therefore, to estimate these resistances, it is necessary to know the temperatures of the bearing components. The article presents the results of FEM simulation tests of temperature distribution in a rolling bearing. These studies were focused on assessing the influence of such features as the distribution of heat sources, the geometric form and size of the contact areas of the balls with the raceways, the conditions of heat convection to the environment and heat conduction inside the bearing. It has been recognized that FEM simulations for the default conditions offered by most commercial FEM systems can lead to out-of-the-box results. As part of the experimental research, conclusions from the simulation studies were verified.
Combinatorial Optimization Problems and Metaheuristics: Review, Challenges, Design, and Development
Authors: Peres Fernando , Castelli Mauro
Published: July 2021

In the past few decades, metaheuristics have demonstrated their suitability in addressing complex problems over different domains. This success drives the scientific community towards the definition of new and better-performing heuristics and results in an increased interest in this research field. Nevertheless, new studies have been focused on developing new algorithms without providing consolidation of the existing knowledge. Furthermore, the absence of rigor and formalism to classify, design, and develop combinatorial optimization problems and metaheuristics represents a challenge to the field’s progress. This study discusses the main concepts and challenges in this area and proposes a formalism to classify, design, and code combinatorial optimization problems and metaheuristics. We believe these contributions may support the progress of the field and increase the maturity of metaheuristics as problem solvers analogous to other machine learning algorithms.
Optimization of Design Parameters in LSTM Model for Predictive Maintenance
Authors: Kim Do-Gyun , Choi Jin-Young
Published: July 2021

Predictive maintenance conducts maintenance actions according to the prognostic state of machinery, which can be demonstrated by a model. Due to this characteristic, choosing a proper model for describing the state of machinery is important. Among various model-based approaches, we address an artificial intelligence (AI) model-based approach which uses AI models obtained from collected data. Specifically, we optimize design parameters of a predictive maintenance model based on long short-term memory (LSTM). To define an effective and efficient health indicator, we suggest a method for feature reduction based on correlation analysis and stepwise comparison of features. Then, hyperparameters determining the structure of LSTM are optimized by using genetic algorithm. Through numerical experiments, the performance of the suggested method is validated.
Geotechnical Evaluation of Diesel Contaminated Clayey Soil
Authors: Hernández-Mendoza Christian E. , García Ramírez Pamela , Chávez Alegría Omar
Published: July 2021

Soil contamination by different hydrocarbons has rapidly expanded worldwide, surpassing the self-purification capacity of soils and increasing the number of contaminated sites. Although much effort has been devoted to study the effects of diesel contamination on the geotechnical properties of soil, there is still limited available information about it. Moreover, there is no available information about the maximum diesel retention that soil can have and its effect on the geotechnical behavior of the soil. Thus, in this paper, we determined the maximum diesel retention by an unsaturated clayey soil and evaluated the impact of diesel contamination on its geotechnical properties. The results showed that the soil could only retain 12.6% of the added diesel and the excess was expulsed. At such a diesel concentration, the saturation rate of the soil was lower than 80%. Diesel contamination increased the plasticity and the internal friction angle of the soil, while its cohesion was considerably decreased. It should be noted that the matric suction of contaminated soil was lower than the one obtained for natural soil. However, its osmotic suction was considerably higher. This indicates that osmotic suction must be considered to evaluate the shear strength of contaminated soils.
Quantifying the Impact of Student Enrollment Patterns on Academic Success Using a Hidden Markov Model
Authors: Boumi Shahab , Vela Adan Ernesto
Published: July 2021

Simplified classifications have often led to college students being labeled as full-time or part-time students. However, student enrollment patterns can be much more complicated at many universities, as it is common for students to switch between full-time and part-time enrollment each semester based on finances, scheduling, or family needs. While previous studies have identified part-time enrollment as a risk factor to students’ academic success, limited research has examined the impact of enrollment patterns or strategies on academic performance. Unlike traditional methods that use a single-period model to classify students into full-time and part-time categories, in this study, we apply an advanced multi-period dynamic approach using a Hidden Markov Model to distinguish and cluster students’ enrollment strategies into three categories: full-time, part-time, and mixed. We then investigate and compare the academic performance outcomes of each group based on their enrollment strategies while taking into account student type (i.e., first-time-in-college students and transfer students). Analysis of undergraduate student records data collected at the University of Central Florida from 2008 to 2017 shows that the academic performance of first-time-in-college students who apply a mixed enrollment strategy is closer to that of full-time students, as compared to part-time students. Moreover, during their part-time semesters, mixed-enrollment students significantly outperform part-time students. Similarly, analysis of transfer students shows that a mixed-enrollment strategy is correlated with similar graduation rates as the full-time enrollment strategy and more than double the graduation rate associated with part-time enrollment. This finding suggests that part-time students can achieve better overall outcomes by increased engagement through occasional full-time enrollments.
Pharmacokinetics of Vancomycin Installation in Pleural Cavity—A Clinical Case with Animal Experiments
Authors: Lee Soojin , Ahn Hyo Yeong , Kim Keunyoung , Kim Jeong Hun , Moon Soo Young , Kim Yeong Dae
Published: July 2021

(1) background: Postpneumonectomy empyema is often observed in patients after a complete pneumonectomy. The management of these cases can be challenging when the condition of patients is complicated by a bronchopleural fistula. A multidisciplinary approach is required to manage these critically ill patients, especially when they are not suitable candidates for surgery; (2–3) Methods & Results: we report a case of successfully treated postpneumonectomy empyema caused by a bronchopleural fistula and pharmacokinetics of vancomycin installation in pleural cavity using rat experiments; (4) Conclusions The experiments provide evidence that irrigation of the pleural cavity with an antibiotic solution containing vancomycin may be an efficient treatment strategy, especially in the case of an MRSA infection in the thickened pleura.
Integrated IR Modulator with a Quantum Cascade Laser
Authors: Mikołajczyk Janusz , Szabra Dariusz
Published: July 2021

This paper presents an infrared pulsed modulator into which quantum cascade lasers and a current driver are integrated. The main goal of this study was to determine the capabilities of a new modulator design based on the results of its electrical model simulation and laboratory experiments. A simulation model is a unique tool because it includes the electrical performance of the lasing structure, signal wiring, and driving unit. In the laboratory model, a lasing structure was mounted on the interfacing poles as close to the switching electronics as possible with direct wire bonding. The radiation pulses and laser biasing voltage were registered to analyze the influence of laser module impedance. Both simulation and experimental results demonstrated that the quantum cascade laser (QC laser) design strongly influenced the shape of light, driving current, and biasing voltage pulses. It is a complex phenomenon depending on the laser construction and many other factors, e.g., the amplitude and time parameters of the supplying current pulses. However, this work presents important data to develop or modify numerical models describing QC laser operation. The integrated modulator provided pulses with a 20–100 ns duration and a frequency of 1 MHz without any active cooling. The designed modulator ensured the construction of a sensor based on direct laser absorption spectroscopy, applying the QC laser with spectral characteristics matched to absorption lines of the detected substances. It can also be used in optical ranging and recognition systems.
Correction for the Partial Volume Effects (PVE) in Nuclear Medicine Imaging: A Post-Reconstruction Analytic Method
Authors: Di Martino Fabio , Barca Patrizio , Bortoli Eleonora , Giuliano Alessia , Volterrani Duccio
Published: July 2021

Quantitative analyses in nuclear medicine are increasingly used, both for diagnostic and therapeutic purposes. The Partial Volume Effect (PVE) is the most important factor of loss of quantification in Nuclear Medicine, especially for evaluation in Region of Interest (ROI) smaller than the Full Width at Half Maximum (FWHM) of the PSF. The aim of this work is to present a new approach for the correction of PVE, using a post-reconstruction process starting from a mathematical expression, which only requires the knowledge of the FWHM of the final PSF of the imaging system used. After the presentation of the theoretical derivation, the experimental evaluation of this method is performed using a PET/CT hybrid system and acquiring the IEC NEMA phantom with six spherical “hot” ROIs (with diameters of 10, 13, 17, 22, 28, and 37 mm) and a homogeneous “colder” background. In order to evaluate the recovery of quantitative data, the effect of statistical noise (different acquisition times), tomographic reconstruction algorithm with and without time-of-flight (TOF) and different signal-to-background activity concentration ratio (3:1 and 10:1) was studied. The application of the corrective method allows recovering the loss of quantification due to PVE for all sizes of spheres acquired, with a final accuracy less than 17%, for lesion dimensions larger than two FWHM and for acquisition times equal to or greater than two minutes.
Two-Beam Free-Electron Lasers and Self-Injected Nonlinear Harmonic Generation
Authors: Sabia Elio , Di Palma Emanuele , Dattoli Giuseppe
Published: July 2021

The possibility of extending the tunability of Free-Electron Lasers towards short wavelengths has been explored through the design of devices conceived to enhance the mechanisms of nonlinear harmonic generation. In this respect, different schemes of operation have been suggested in the past, such as harmonic seeding, bi-harmonic undulators, and two-beam self-seeding devices. In this paper, we discuss how these methods can be merged into a tool, extending the performance of FEL devices.
Reverse Logistics Location Based on Energy Consumption: Modeling and Multi-Objective Optimization Method
Authors: Chang Lijun , Zhang Honghao , Xie Guoquan , Yu Zhenzhong , Zhang Menghao , Li Tao , Tian Guangdong , Yu Dexin
Published: July 2021

The low-carbon economy, as a major trend of global economic development, has been a widespread concern, which is a rare opportunity to realize the transformation of the economic way in China. The realization of a low-carbon economy requires improved resource utilization efficiency and reduced carbon emissions. The reasonable location of logistics nodes is of great significance in the optimization of a logistics network. This study formulates a double objective function optimization model of reverse logistics facility location considering the balance between the functional objectives of the carbon emissions and the benefits. A hybrid multi-objective optimization algorithm that combines a gravitation algorithm and a particle swarm optimization algorithm is proposed to solve this reverse logistics facility location model. The mobile phone recycling logistics network in Jilin Province is applied as the case study to verify the feasibility of the proposed reverse logistics facility location model and solution method. Analysis and discussion are conducted to monitor the robustness of the results. The results prove that this approach provides an effective tool to solve the multi-objective optimization problem of reverse logistics location.
Temporal Analysis of Influence of Resource Failures on Cyber-Physical Systems Based on Discrete Timed Petri Nets
Authors: Hsieh Fu-Shiung
Published: July 2021

Advancement of IoT and ICT provide infrastructure to manage, monitor and control Cyber-Physical Systems (CPS) through timely provision of real-time information from the shop floor. Although real-time information in CPS such as resource failures can be detected based on IoT and ICT, improper response to resource failures may cripple CPS and degrade performance. Effective operations of CPS relies on an effective scheme to evaluate the impact of resource failures, support decision making needed and take proper actions to respond to resource failures. This motivates us to develop a methodology to assess the impact of resource failures on operations of CPS and provide the decision support as needed. The goal of this study is to propose solution algorithms to analyze robustness of CPS with respect to resource failures in terms of the impact on temporal properties. Given CPS modeled by a class of discrete timed Petri nets (DTPNs), we develop theory to analyze robustness of CPS by transforming the models to residual spatial-temporal network (RSTN) models in which capacity loss due to resources is reflected. We formulate an optimization problem to determine the influence of resource failures on CPS based on RSTNs and analyze the feasibility to meet the order deadline. To study the feasibility to solve a real problem, we analyze the computational complexity of the proposed algorithms. We illustrate the proposed method by application scenarios. We conduct experiments to study efficiency and verify computational feasibility of the proposed method to solve a real problem.
Spectral-Element Simulation of the Turbulent Flow in an Urban Environment
Authors: Stuck Maxime , Vidal Alvaro , Torres Pablo , Nagib Hassan M. , Wark Candace , Vinuesa Ricardo
Published: July 2021

The mean flow and turbulence statistics of the flow through a simplified urban environment, which is an active research area in order to improve the knowledge of turbulent flow in cities, is investigated. This is useful for civil engineering, pedestrian comfort and for health concerns caused by pollutant spreading. In this work, we provide analysis of the turbulence statistics obtained from well-resolved large-eddy simulations (LES). A detailed analysis of this database reveals the impact of the geometry of the urban array on the flow characteristics and provides for a good description of the turbulent features of the flow within a simplified urban environment. The most prominent features of this complex flow include coherent vortical structures such as the so-called arch vortex, the horseshoe vortex and the roof vortex. These structures of flow have been identified by an analysis of the turbulence statistics. The influence of the geometry of urban environment (and particularly the street width and the building height) on the overall flow behavior has also been studied. Finally, the well-resolved LES results were compared with an available experimental database to discuss differences and similarities between the respective urban configurations.
Application of an Additive Manufactured Hybrid Metal/Composite Shock Absorber Panel to a Military Seat Ejection System
Authors: Acanfora Valerio , Corvino Chiara , Saputo Salvatore , Sellitto Andrea , Riccio Aniello
Published: July 2021

In this work, a preliminary numerical assessment on the application of an additive manufactured hybrid metal/composite shock absorber panels to a military seat ejection system, has been carried out. The innovative character of the shock absorber concept investigated is that the absorbing system has a thickness of only 6 mm and is composed of a pyramid-shaped lattice core that, due to its small size, can only be achieved by additive manufacturing. The mechanical behaviour of these shock absorber panels has been examined by measuring their ability to absorb and dissipate the energy generated during the ejection phase into plastic deformations, thus reducing the loads acting on pilots. In this paper the effectiveness of a system composed of five hybrid shock absorbers, with very thin thickness in order to be easily integrated between the seat and the aircraft floor, has been numerically studied by assessing their ability to absorb the energy generated during the primary ejection phase. To accomplish this, a numerical simulation of the explosion has been performed and the energy absorbed by the shock-absorbing mechanism has been assessed. The performed analysis demonstrated that the panels can absorb more than 60% of the energy generated during the explosion event while increasing the total mass of the pilot-seat system by just 0.8%.
An Expert Artificial Intelligence Model for Discriminating Microseismic Events and Mine Blasts
Authors: Rao Dijun , Shi Xiuzhi , Zhou Jian , Yu Zhi , Gou Yonggang , Dong Zezhen , Zhang Jinzhong
Published: July 2021

To reduce the workload and misjudgment of manually discriminating microseismic events and blasts in mines, an artificial intelligence model called PSO-ELM, based on the extreme learning machine (ELM) optimized by the particle swarm optimization (PSO) algorithm, was applied in this study. Firstly, based on the difference between microseismic events and mine blasts and previous research results, 22 seismic parameters were selected as the discrimination feature parameters and their correlation was analyzed. Secondly, 1600 events were randomly selected from the database of the microseismic monitoring system in Fankou Lead-Zinc Mine to form a sample dataset. Then, the optimal discrimination model was established by investigating the model parameters. Finally, the performance of the model was tested using the sample dataset, and it was compared with the performance of the original ELM model and other commonly used intelligent discrimination models. The results indicate that the discrimination performance of PSO-ELM is the best. The values of the six evaluation indicators are close to the optimal value, which shows that PSO-ELM has great potential for discriminating microseismic events and blasts. The research results obtained can provide a new method for discriminating microseismic events and blasts, and it is of great significance to ensure the safe and smooth operation of mines.
Development of a Lightweight Tungsten Shielding Fiber That Can Be Used for Improving the Performance of Medical Radiation Shields
Authors: Kim Seon-Chil
Published: July 2021

Radiation exposure in medical institutions is mainly due to low doses. Low-dose radiation mainly means scattered radiation, and such scattered radiation can be shielded with a lightweight shielding suit. In this study, the shielding performance of shielding fabrics woven by winding polyethylene (PE) yarn around a 30 μm tungsten wire was evaluated. To improve the shielding performance, an air pressure dispersion process of coating tungsten nanopowder on the fiber was developed. The radiation shielding effectiveness of the shielding fibers with and without dispersed tungsten nanopowder were compared by measuring the spatial dose inside the diagnostic X-ray imaging room of a medical institution. The results of the experiment confirmed that the fabric coated with tungsten nanopowder improved the shielding performance of the general tungsten fiber by approximately 15% and provided relatively effective low-dose radiation shielding at approximately 1.2 m of the X-ray imaging equipment. This study shows that tungsten fiber can be helpful in manufacturing lightweight shielding clothing for protection from scattered radiation in medical institutions.
Feed-Forward Neural Networks for Failure Mechanics Problems
Authors: Aldakheel Fadi , Satari Ramish , Wriggers Peter
Published: July 2021

This work addresses an efficient neural network (NN) representation for the phase-field modeling of isotropic brittle fracture. In recent years, data-driven approaches, such as neural networks, have become an active research field in mechanics. In this contribution, deep neural networks—in particular, the feed-forward neural network (FFNN)—are utilized directly for the development of the failure model. The verification and generalization of the trained models for elasticity as well as fracture behavior are investigated by several representative numerical examples under different loading conditions. As an outcome, promising results close to the exact solutions are produced.
Lp-Norm Inversion of Gravity Data Using Adaptive Differential Evolution
Authors: Song Tao , Hu Xing , Du Wei , Cheng Lianzheng , Xiao Tiaojie , Li Qian
Published: July 2021

As a popular population based heuristic evolutionary algorithm, differential evolution (DE) has been widely applied in various science and engineering problems. Similar to other global nonlinear algorithms, such as genetic algorithm, simulated annealing, particle swarm optimization, etc., the DE algorithm is mostly applied to resolve the parametric inverse problem, but has few applications in physical property inversion. According to our knowledge, this is the first time DE has been applied in obtaining the physical property distribution of gravity data due to causative sources embedded in the subsurface. In this work, the search direction of DE is guided by better vectors, enhancing the exploration efficiency of the mutation strategy. Besides, to reduce the over-stochastic of the DE algorithm, the perturbation directions in mutation operations are smoothed by using a weighted moving average smoothing technique, and the Lp-norm regularization term is implemented to sharpen the boundary of density distribution. Meanwhile, in the search process of DE, the effect of Lp-norm regularization term is controlled in an adaptive manner, which can always have an impact on the data misfit function. In the synthetic anomaly case, both noise-free and noisy data sets are considered. For the field case, gravity anomalies originating from the Shihe iron ore deposit in China were inverted and interpreted. The reconstructed density distribution is in good agreement with the one obtained by drill-hole information. Based on the tests in the present study, one can conclude that the Lp-norm inversion using DE is a useful tool for physical property distribution using gravity anomalies.
Thread-Aware Mechanism to Enhance Inter-Node Load Balancing for Multithreaded Applications on NUMA Systems
Authors: Chiang Mei-Ling , Su Wei-Lun
Published: July 2021

NUMA multi-core systems divide system resources into several nodes. When an imbalance in the load between cores occurs, the kernel scheduler’s load balancing mechanism then migrates threads between cores or across NUMA nodes. Remote memory access is required for a thread to access memory on the previous node, which degrades performance. Threads to be migrated must be selected effectively and efficiently since the related operations run in the critical path of the kernel scheduler. This study focuses on improving inter-node load balancing for multithreaded applications. We propose a thread-aware selection policy that considers the distribution of threads on nodes for each thread group while migrating one thread for inter-node load balancing. The thread is selected for which its thread group has the least exclusive thread distribution, and thread members are distributed more evenly on nodes. This has less influence on data mapping and thread mapping for the thread group. We further devise several enhancements to eliminate superfluous evaluations for multithreaded processes, so the selection procedure is more efficient. The experimental results for the commonly used PARSEC 3.0 benchmark suite show that the modified Linux kernel with the proposed selection policy increases performance by 10.7% compared with the unmodified Linux kernel.
Machine Learning-Based Tools for Wind Turbine Acoustic Monitoring
Authors: Ciaburro Giuseppe , Iannace Gino , Puyana-Romero Virginia , Trematerra Amelia
Published: July 2021

The identification and separation of sound sources has always been a difficult problem for acoustic technicians to tackle. This is due to the considerable complexity of a sound that is made up of many contributions at different frequencies. Each sound has a specific frequency spectrum, but when many sounds overlap it becomes difficult to discriminate between the different contributions. In this case, it can be extremely useful to have a tool that is capable of identifying the operating conditions of an acoustic source. In this study, measurements were made of the noise emitted by a wind turbine in the vicinity of a sensitive receptor. To identify the operating conditions of the wind turbine, average spectral levels in one-third octave bands were used. A model based on a support vector machine (SVM) was developed for the detection of the operating conditions of the wind turbine; then a model based on an artificial neural network was used to compare the performance of both models. The high precision returned by the simulation models supports the adoption of these tools as a support for the acoustic characterization of noise in environments close to wind turbines.
Application of Biochar Functionalized with Layered Double Hydroxides: Improved Plant Growth Performance after Use as Phosphate Adsorbent
Authors: Buates Jittrera , Imai Tsuyoshi
Published: July 2021

The objective of this study was to verify the feasibility of using biochar, functionalized with layered double hydroxides, as a fertilizer after its use in phosphate treatment (P-BC-LDHs). It was conducted with several levels of P-BC-LDHs using seed germination and early growth assays of lettuce (Lactuca sativa L.). The application of P-BC-LDHs resulted in successful seedling emergence, with an excellent germination capacity of over 96% for all treatments. However, compared to the controls, P-BC-LDHs did not provide favorable seedling traits. In contrast, in the latter experiments, lettuce cultivated under mixtures with P-BC-LDHs, particularly at an application rate of 2.5% (w/w), displayed superior growth quality to those under non-treated conditions. The length of lettuce shoots and roots from this optimal dosage were increased by at least 24% compared to untreated samples. A 17% reduction in biomass yield was observed for the samples from non-supplemented substrates. The nutrient release profiles showed that P-BC-LDHs were capable of slowly supplying phosphorus, thereby increasing the long-term nutrient availability for plants. The findings reported here provide important insights into these materials and confirm that P-BC-LDHs can be used for agricultural purposes after phosphate remediation applications. The results of this study provide constructive information to facilitate the implementation of biochar-based LDH composites for sustainable phosphate removal and recovery.
Optimization of PID Controller to Stabilize Quadcopter Movements Using Meta-Heuristic Search Algorithms
Authors: Sheta Alaa , Braik Malik , Maddi Dheeraj Reddy , Mahdy Ahmed , Aljahdali Sultan , Turabieh Hamza
Published: July 2021

Quadrotor UAVs are one of the most preferred types of small unmanned aerial vehicles, due to their modest mechanical structure and propulsion precept. However, the complex non-linear dynamic behavior of the Proportional Integral Derivative (PID) controller in these vehicles requires advanced stabilizing control of their movement. Additionally, locating the appropriate gain for a model-based controller is relatively complex and demands a significant amount of time, as it relies on external perturbations and the dynamic modeling of plants. Therefore, developing a method for the tuning of quadcopter PID parameters may save effort and time, and better control performance can be realized. Traditional methods, such as Ziegler–Nichols (ZN), for tuning quadcopter PID do not provide optimal control and might leave the system with potential instability and cause significant damage. One possible approach that alleviates the tough task of nonlinear control design is the use of meta-heuristics that permit appropriate control actions. This study presents PID controller tuning using meta-heuristic algorithms, such as Genetic Algorithms (GAs), the Crow Search Algorithm (CSA) and Particle Swarm Optimization (PSO) to stabilize quadcopter movements. These meta-heuristics were used to control the position and orientation of a PID controller based on a fitness function proposed to reduce overshooting by predicting future paths. The obtained results confirmed the efficacy of the proposed controller in felicitously and reliably controlling the flight of a quadcopter based on GA, CSA and PSO. Finally, the simulation results related to quadcopter movement control using PSO presented impressive control results, compared to GA and CSA.
Resilient Scheduling as a Response to Uncertainty in Construction Projects
Authors: Milat Martina , Knezić Snježana , Sedlar Jelena
Published: July 2021

Complex construction projects are developed in a dynamic environment, where uncertainty conditions have a great potential to affect project deliverables. In an attempt to efficiently deal with the negative impacts of uncertainty, resilient baseline schedules are produced to improve the probability of reaching project goals, such as respecting the due date and reaching the expected profit. Prior to introducing the resilient scheduling procedure, a taxonomy model was built to account for uncertainty sources in construction projects. Thence, a multi-objective optimization model is presented to manage the impact of uncertainty. This approach can be described as a complex trade-off analysis between three important features of a construction project: duration, stability, and profit. The result of the suggested procedure is presented in a form of a resilient baseline schedule, so the ability of a schedule to absorb uncertain perturbations is improved. The proposed optimization problem is illustrated on the example project network, along which the probabilistic simulation method was used to validate the results of the scheduling process in uncertain conditions. The proposed resilient scheduling approach leads to more accurate forecasting, so the project planning calculations are accepted with increased confidence levels.
Two-Color TeraHertz Radiation by a Multi-Pass FEL Oscillator
Authors: Opromolla Michele , Petrillo Vittoria
Published: July 2021

In this paper, we show that an electron beam produced by a super-conducting linac, driven in a sequence of two undulator modules of different periods, can generate two-color Terahertz radiation with wavelengths ranging from 100 μm to 2 μm. The generated pulses are synchronized, both MW-class, and highly coherent. Their specific properties and generation will be discussed in detail. Besides the single-spike pulse structure, usually observed in oscillators, we show that both the THz pump and probe can be modulated in a coherent comb of pulses, enabling periodic excitation and stroboscopic measurements.
Changes in Power Plant NOx Emissions over Northwest Greece Using a Data Assimilation Technique
Authors: Skoulidou Ioanna , Koukouli Maria-Elissavet , Segers Arjo , Manders Astrid , Balis Dimitris , Stavrakou Trissevgeni , van Geffen Jos , Eskes Henk
Published: July 2021

In this work, we investigate the ability of a data assimilation technique and space-borne observations to quantify and monitor changes in nitrogen oxides (NOx) emissions over Northwestern Greece for the summers of 2018 and 2019. In this region, four lignite-burning power plants are located. The data assimilation technique, based on the Ensemble Kalman Filter method, is employed to combine space-borne atmospheric observations from the high spatial resolution Sentinel-5 Precursor (S5P) Tropospheric Monitoring Instrument (TROPOMI) and simulations using the LOTOS-EUROS Chemical Transport model. The Copernicus Atmosphere Monitoring Service-Regional European emissions (CAMS-REG, version 4.2) inventory based on the year 2015 is used as the a priori emissions in the simulations. Surface measurements of nitrogen dioxide (NO2) from air quality stations operating in the region are compared with the model surface NO2 output using either the a priori (base run) or the a posteriori (assimilated run) NOx emissions. Relative to the a priori emissions, the assimilation suggests a strong decrease in concentrations for the station located near the largest power plant, by 80% in 2019 and by 67% in 2018. Concerning the estimated annual a posteriori NOx emissions, it was found that, for the pixels hosting the two largest power plants, the assimilated run results in emissions decreased by ~40–50% for 2018 compared to 2015, whereas a larger decrease, of ~70% for both power plants, was found for 2019, after assimilating the space-born observations. For the same power plants, the European Pollutant Release and Transfer Register (E-PRTR) reports decreased emissions in 2018 and 2019 compared to 2015 (−35% and −38% in 2018, −62% and −72% in 2019), in good agreement with the estimated emissions. We further compare the a posteriori emissions to the reported energy production of the power plants during the summer of 2018 and 2019. Mean decreases of about −35% and−63% in NOx emissions are estimated for the two larger power plants in summer of 2018 and 2019, respectively, which are supported by similar decreases in the reported energy production of the power plants (~−30% and −70%, respectively).