bluuebunny/crossref_metadata_2025 huggingface dataset:
Liver Transplant Patients with High Preoperative Serum Bilirubin Levels Are at Increased Risk of Postoperative Delirium: A Retrospective Study
Authors: Park Kyu Hee , Son Hyo Jung , Choi Yoon Ji , Park Gene Hyun , Lee Yoon Sook , Park Ju Yeon , Ri Hyun-Su , Shim Jae Ryong
Published: May 2020

Postoperative delirium is a common complication after liver transplantation (LT). A high model for end-stage liver disease (MELD) score is an independent risk factor for postoperative delirium, but it is unclear which of the components of this score are risk indicators. The aim of this study was to analyze the incidence of postoperative delirium according to the preoperative serum bilirubin level, a component of the MELD score, in patients who underwent LT. The medical records of 325 patients who underwent LT from January 2010 to February 2019 at a single university hospital were retrospectively reviewed. The patients were divided into two groups: those who experienced postoperative delirium (Delirium group, n = 69) and those who did not (Control group, n = 256). Data on the patients’ demographic characteristics, perioperative management, and postoperative complications were collected. Mean preoperative bilirubin level was higher in the Delirium group than in the Control group (p < 0.0001). In the Delirium group, 54 (78.26%) patients had preoperative bilirubin levels above 3.5 mg/dL. In the multivariate analysis, preoperative bilirubin above 3.5 mg/dL was associated with postoperative delirium (p = 0.002). Therefore, preoperative hyperbilirubinemia is an independent risk factor for postoperative delirium.
Automated Classification of Colorectal Neoplasms in White-Light Colonoscopy Images via Deep Learning
Authors: Yang Young Joo , Cho Bum-Joo , Lee Myung-Je , Kim Ju Han , Lim Hyun , Bang Chang Seok , Jeong Hae Min , Hong Ji Taek , Baik Gwang Ho
Published: May 2020

Background: Classification of colorectal neoplasms during colonoscopic examination is important to avoid unnecessary endoscopic biopsy or resection. This study aimed to develop and validate deep learning models that automatically classify colorectal lesions histologically on white-light colonoscopy images. Methods: White-light colonoscopy images of colorectal lesions exhibiting pathological results were collected and classified into seven categories: stages T1-4 colorectal cancer (CRC), high-grade dysplasia (HGD), tubular adenoma (TA), and non-neoplasms. The images were then re-classified into four categories including advanced CRC, early CRC/HGD, TA, and non-neoplasms. Two convolutional neural network models were trained, and the performances were evaluated in an internal test dataset and an external validation dataset. Results: In total, 3828 images were collected from 1339 patients. The mean accuracies of ResNet-152 model for the seven-category and four-category classification were 60.2% and 67.3% in the internal test dataset, and 74.7% and 79.2% in the external validation dataset, respectively, including 240 images. In the external validation, ResNet-152 outperformed two endoscopists for four-category classification, and showed a higher mean area under the curve (AUC) for detecting TA+ lesions (0.818) compared to the worst-performing endoscopist. The mean AUC for detecting HGD+ lesions reached 0.876 by Inception-ResNet-v2. Conclusions: A deep learning model presented promising performance in classifying colorectal lesions on white-light colonoscopy images; this model could help endoscopists build optimal treatment strategies.
Monitoring of Delayed Cerebral Ischemia in Patients with Subarachnoid Hemorrhage via Near-Infrared Spectroscopy
Authors: Park Jeong Jin , Kim Chulho , Jeon Jin Pyeong
Published: May 2020

We investigated the role of near infrared spectroscopy (NIRS) in identifying delayed cerebral ischemia (DCI) in patients with subarachnoid hemorrhage (SAH). We measured the cerebral regional oxygen saturation (rSO2) continuously for 14 days. The differences in rSO2 according to DCI were analyzed. We also compared the diagnostic accuracy of NIRS and transcranial Doppler ultrasonography (TCD) for DCI detection using the area under receiver operator characteristic (ROC) curve. Fifty-two patients treated with coil embolization were enrolled, including 18 with DCI (34.6%) and 34 without DCI (65.4%). Significant differences in rSO2 levels were observed from days 7 to 9. The rSO2 level was 60.95 (58.10–62.30) at day 7 in the DCI vs. 63.90 (62.50–67.10) in the non-DCI patients. By day 8, it was 59.50 (56.90–64.50) in the DCI vs. 63.30 (59.70–68.70) in the non-DCI cases. By day 9, it was 61.85 (59.40–65.20) in the DCI vs. 66.00 (62.70–68.30) in the non-DCI. A decline of >12.7% in SO2 rate yielded a sensitivity of 94.44% (95% CI: 72.7–99.9%) and a specificity of 70.59% (95% CI: 52.5–84.9%) for identifying DCI. Changes in NIRS tended to yield better diagnostic accuracy than TCD, but were not statistically significant. NIRS is a feasible method for real-time detection of DCI.
Impact of the Gut Microbiota on Atorvastatin Mediated Effects on Blood Lipids
Authors: Zimmermann Friederike , Roessler Johann , Schmidt David , Jasina Andrzej , Schumann Paul , Gast Martina , Poller Wolfgang , Leistner David , Giral Hector , Kränkel Nicolle , Kratzer Adelheid , Schuchardt Sven , Heimesaat Markus M. , Landmesser Ulf , Haghikia Arash
Published: May 2020

Background and Aims: The mechanisms of interindividual variation of lipid regulation by statins, such as the low-density lipoprotein cholesterol (LDL) lowering effects, are not fully understood yet. Here, we used a gut microbiota depleted mouse model to investigate the relation between the gut microbiota and the regulatory property of atorvastatin on blood lipids. Methods: Mice (C57BL/6) with intact gut microbiota or antibiotic induced abiotic mice (ABS) were put on standard chow diet (SCD) or high fat diet (HFD) for six weeks. Atorvastatin (10 mg/kg body weight/day) or a control vehicle were applied per gavage for the last four weeks of dietary treatment. Blood lipids including total cholesterol, very low-density lipoprotein, low-density lipoprotein, high-density lipoprotein and sphingolipids were measured to probe microbiota-dependent effects of atorvastatin. The expression of genes involved in hepatic and intestinal cholesterol metabolism was analyzed with qRT-PCR. The alteration of the microbiota profile was examined using 16S rRNA qPCR in mice with intact gut microbiota. Results: HFD feeding significantly increased total blood cholesterol and LDL levels, as compared to SCD in both mice with intact and depleted gut microbiota. The cholesterol lowering effect of atorvastatin was significantly attenuated in mice with depleted gut microbiota. Moreover, we observed a global shift in the abundance of several sphingolipids upon atorvastatin treatment which was absent in gut microbiota depleted mice. The regulatory effect of atorvastatin on the expression of distinct hepatic and intestinal cholesterol-regulating genes, including Ldlr, Srebp2 and Npc1l1 was altered upon depletion of gut microbiota. In response to HFD feeding, the relative abundance of the bacterial phyla Bacteroidetes decreased, while the abundance of Firmicutes increased. The altered ratio between Firmicutes to Bacteroidetes was partly reversed in HFD fed mice treated with atorvastatin. Conclusions: Our findings support a regulatory impact of atorvastatin on the gut microbial profile and, in turn, demonstrate a crucial role of the gut microbiome for atorvastatin-related effects on blood lipids. These results provide novel insights into potential microbiota-dependent mechanisms of lipid regulation by statins, which may account for variable response to statin treatment.
Effects of Polyphenol-Rich Interventions on Cognition and Brain Health in Healthy Young and Middle-Aged Adults: Systematic Review and Meta-Analysis
Authors: Ammar Achraf , Trabelsi Khaled , Boukhris Omar , Bouaziz Bassem , Müller Patrick , M Glenn Jordan , Bott Nicholas T. , Müller Notger , Chtourou Hamdi , Driss Tarak , Hökelmann Anita
Published: May 2020

Context: Affecting older and even some younger adults, neurodegenerative disease represents a global public health concern and has been identified as a research priority. To date, most anti-aging interventions have examined older adults, but little is known about the effects of polyphenol interventions on brain-related aging processes in healthy young and middle-aged adults. Objective: This systematic review and meta-analysis aimed to evaluate the acute and chronic effects of (poly)phenol-rich diet supplementation on cognitive function and brain health in young and middle-aged adults. In July 2019, two electronic databases (PubMed and Web of Science) were used to search for relevant trials examining the effect of acute or chronic (poly)phenol-rich supplementation on cognitive function and neuroprotective measures in young and middle-aged adults (<60 years old). A total of 4303 records were screened by two researchers using the PICOS criteria. Fifteen high quality (mean PEDro score = 8.8 ± 0.58) trials with 401 total participants were included in the final analyses. Information on treatment, study design, characteristics of participants, outcomes and used tools were extracted following PRISMA guidelines. When items were shown to be sufficiently comparable, a random-effects meta-analysis was used to pool estimates across studies. Effect size (ES) and its 95% confidence interval (CI) was calculated. The meta-analysis indicated that (poly)phenol supplementation significantly increased brain-derived neurotrophic factor (ES = 3.259, p = 0.033), which was accompanied by higher performance in serial (7s) subtraction (ES = 1.467, p = 0.001) and decreases in simple reaction time (ES = −0.926, p = 0.015) and mental fatigue (ES = −3.521, p = 0.010). Data related to cognitive function were skewed towards an effect from acute compared to chronic polyphenol intervention; data related to BDNF were skewed toward an effect from higher bioavailability phenolic components. Conclusion: This meta-analysis provides promising findings regarding the usefulness of polyphenol-rich intervention as an inexpensive approach for enhancing circulation of pro-cognitive neurotrophic factors. These beneficial effects appear to depend on the supplementation protocols. An early acute and/or chronic application of low- to high-dose phenolic components with high bioavailability rates (≥30%) at a younger age appear to provide more promising effects.
Relationship between HIF-1 and Circadian Clock Proteins in Obstructive Sleep Apnea Patients—Preliminary Study
Authors: Gabryelska Agata , Sochal Marcin , Turkiewicz Szymon , Białasiewicz Piotr
Published: May 2020

Obstructive sleep apnea (OSA) is characterized by intermittent hypoxia and associated with the disruption of circadian rhythm. The study aimed to assess the relationship between hypoxia-inducible factor (HIF) subunits, circadian clock proteins, and polysomnography (PSG) variables, in healthy individuals and severe OSA patients. The study included 20 individuals, who underwent PSG and were divided into severe OSA group (n = 10; AHI ≥ 30) and healthy control (n = 10; AHI < 5) based on apnea-hypopnea index (AHI). All participants had their peripheral blood collected in the evening before and the morning after the PSG. HIF-1α, HIF-1β, BMAL1, CLOCK, CRY1, and PER1 protein concertation measurements were performed using ELISA. In a multivariate general linear model with the concentration of all circadian clock proteins as dependent variables, evening HIF-1α protein level was the only significant covariant (p = 0.025). Corrected models were significant for morning and evening PER1 (p = 0.008 and p = 0.006, respectively), evening (p = 0.043), and evening BMAL protein level (p = 0.046). In corrected models, evening HIF-1α protein level had an influence only on the evening PER1 protein level. Results suggest that OSA patients are at risk for developing circadian clock disruption. This process might be mediated by subunit α of HIF-1, as its increased protein level is associated with overexpression of circadian clock proteins.
Development of Algorithm for Clinical Management of Sickle Cell Bone Disease: Evidence for a Role of Vertebral Fractures in Patient Follow-up
Authors: De Franceschi Lucia , Gabbiani Daniele , Giusti Andrea , Forni Gianluca , Stefanoni Filippo , Pinto Valeria Maria , Sartori Giulia , Balocco Manuela , Dal Zotto Chiara , Valenti Maria Teresa , Dalle Carbonare Luca
Published: May 2020

Sickle-cell disease (SCD) is a worldwide distributed hemoglobinopathy, characterized by hemolytic anemia associated with vaso-occlusive events. These result in acute and chronic multiorgan damage. Bone is early involved, leading to long-term disability, chronic pain and fractures. Here, we carried out a retrospective study to evaluate sickle bone disease (SBD) in a cohort of adults with SCD. We assessed bone density, metabolism and turnover. We also evaluated the presence of fractures and the correlation between SCD severity and skeletal manifestations. A total of 71 patients with SCD were analyzed. The mean age of population was 39 ± 10 years, 56% of which were females. We found osteoporosis in a range between 7% and 18% with a high incidence of vertebral fractures. LDH and AST were predictive for the severity of vertebral fractures, while bone density was not. Noteworthy, we identified -1.4 Standard Deviations T-score as the cutoff for detecting the presence of fractures in patients with SCD. Collectively our data allowed us to develop an algorithm for the management of SBD, which may be useful in daily clinical practice to early intersect and treat SBD.
Neutrophil Phenotypes in Coronary Artery Disease
Authors: Maréchal Patrick , Tridetti Julien , Nguyen Mai-Linh , Wéra Odile , Jiang Zheshen , Gustin Maxime , Donneau Anne-Françoise , Oury Cécile , Lancellotti Patrizio
Published: May 2020

Clinical evidence indicates that innate immune cells may contribute to acute coronary syndrome (ACS). Our prospective study aimed at investigating the association of neutrophil phenotypes with ACS. 108 patients were categorized into chronic stable coronary artery disease (n = 37), unstable angina (UA) (n = 19), Non-ST-Elevation Myocardial Infarction (NSTEMI) (n = 25), and ST-Elevation Myocardial Infarction (STEMI) (n = 27). At the time of inclusion, blood neutrophil subpopulations were analysed by flow cytometry. Differential blood cell count and plasma levels of neutrophilic soluble markers were recorded at admission and, for half of patients, at six-month follow-up. STEMI and NSTEMI patients displayed higher neutrophil count and neutrophil-to-lymphocyte ratio than stable and UA patients (p < 0.0001), which normalized at six-month post-MI. Atypical low-density neutrophils were detected in the blood of the four patient groups. STEMI patients were characterized by elevated percentages of band cells compared to the other patients (p = 0.019). Multivariable logistic regression analysis revealed that plasma levels of total myeloperoxidase was associated with STEMI compared to stable (OR: 1.434; 95% CI: 1.119–1.837; P < 0.0001), UA (1.47; 1.146–1.886; p = 0.002), and NSTEMI (1.213; 1.1–1.134; p = 0.0001) patients, while increased neutrophil side scatter (SSC) signal intensity was associated with NSTEMI compared to stable patients (3.828; 1.033–14.184; p = 0.045). Hence, changes in neutrophil phenotype are concomitant to ACS.
Development of Broadband Underwater Radio Communication for Application in Unmanned Underwater Vehicles
Authors: Smolyaninov Igor , Balzano Quirino , Young Dendy
Published: May 2020

This paper presents several novel designs of small form factor underwater radio antennas operating in the 2 MHz, 50 MHz and 2.4 GHz bands. These antennas efficiently excite surface electromagnetic waves (SEW) which propagate along the surface of seawater. The antenna operation is made possible due to implementation of an impedance matching enclosure, which is filled with de-ionized water. Enhanced coupling to surface electromagnetic waves is enabled by the enhancement of the electromagnetic field at the antenna apex. These features allow us to make antenna dimensions considerably smaller compared to typical free space designs. They also considerably improve coupling of electromagnetic energy to the surrounding seawater. Since SEW propagation length is considerably larger than the skin depth in seawater, this technique is useful for underwater broadband wireless communication. We conclude that the developed broadband underwater radio communication technique will be useful in networking of unmanned underwater vehicles.
An Integrated Reconstruction of the Multiannual Wave Pattern in the Gulf of Naples (South-Eastern Tyrrhenian Sea, Western Mediterranean Sea)
Authors: Saviano Simona , Cianelli Daniela , Zambianchi Enrico , Conversano Fabio , Uttieri Marco
Published: May 2020

Surface gravity waves retrieved by a network of HF (High Frequency) radars and measured in situ by an ADCP (Acoustic Doppler Current Profiler) current meter connected to an elastic beacon were used to carry out a multiple-year characterization of the wave field of the Gulf of Naples (south-eastern Tyrrhenian Sea, western Mediterranean). The aim of the work was to create a climatology of the study area and to demonstrate the potential of an integrated platform for coastal studies. The patterns recorded by the different instruments were in agreement with the wave climatology of the southern Tyrrhenian Sea as well as with previous scores for the same area. The results presented in this work also highlight seasonal and interannual consistency in the wave patterns for each site. In a wider context, this study demonstrates the potential of HF radars as long-term monitoring tools of the wave field in coastal basins, and supports the development of integrated observatories to address large-scale scientific challenges such as coastal ocean dynamics and the impact of global change on the local dynamics.
Verification of Novel Maritime Route Extraction Using Kernel Density Estimation Analysis with Automatic Identification System Data
Authors: Lee Jeong-Seok , Son Woo-Ju , Lee Hyeong-Tak , Cho Ik-Soon
Published: May 2020

A maritime route is used by sea transportation vessels to access the trading ports, and route design standards for the safety of maritime traffic have been established in various countries and organizations. However, no quantitative safety verification method related to route design currently exists. In this study, a novel maritime route was created and compared with the original route in Incheon, the Republic of Korea, based on the relevant automatic identification system (AIS) data. The attendant traffic density was revealed via kernel density estimation analysis of the AIS data, with the results used to create the boundary of the novel route through an image processing technique. The boundary and the centerline of the maritime route were determined using a line smoothing technique. For safety verification, the centerline of the original route and that of the novel maritime route were compared in terms of sinuosity, intersection angle, and route change envelope (RCE). The sinuosity analysis demonstrated that the route was stable in terms of the outer harbor limit, while the intersection angle analysis demonstrated that the novel maritime route intersection angle was stable. The RCE was used to objectively compare the absolute values of the distance change in the centerline.
Manoeuvrability of a Large Cruise Ship after Damage for Safe Return to Port
Authors: Yuura Tetsuhiro , Hashimoto Hirotada , Matsuda Akihiko
Published: May 2020

Free-running model tests were conducted using a scaled model of a large cruise ship with a damaged compartment, to investigate the effects of damage opening and floodwater on the manoeuvring performance in calm water and regular and irregular head waves. Drifting tests in regular beam waves were also performed. The experimental results indicated that the course-keeping ability in waves and turning ability became worse in the damaged condition. However, the target ship retained its manoeuvrability for safe return to the port, on its own, even in a damaged state. As it is time- and cost-consuming to conduct a free-running model experiment, a captive model test was also carried out to develop a system-based simulation model for evaluating the manoeuvrability of large cruise ships after damage.
Effective Mistuning Identification Method of Integrated Bladed Discs of Marine Engine Turbochargers
Authors: Píštěk Václav , Kučera Pavel , Fomin Oleksij , Lovska Alyona
Published: May 2020

Radial turbine and compressor wheels form essential cornerstones of modern internal combustion engines in terms of economy, efficiency and, in particular, environmental compatibility. As a result of the introduction of exhaust gas turbochargers in the extremely important global market for diesel engines, higher engine efficiencies are possible, which in turn reduce fuel consumption. The associated reduced exhaust emissions can answer questions that results from environmentally relevant aspects of the engine development. In shipping, the international Maritime Organisation (IMO) prescribes the step-by-step reduction of nitrogen oxide and other types of emissions. To reduce these emissions, various systems are being developed, in which turbochargers are an important part. The requirements for the reliability and service life of turbochargers are constantly increasing. Turbocharger blade vibration is one of the most important problems to be solved when designing the rotors. In the case of real rotors, so-called mistuning arises, which is a slight deviation of the properties of the individual blades from the design parameters. The article deals with an effective method of mistuning identification for cases of integrated bladed discs of marine engine turbochargers. Unlike approaches that use costly scanning laser Doppler vibrometers, this method is based on using only a simple laser vibrometer in combination with a computational model of the integrated bladed disc. The added value of this method is, in particular, a significant reduction in the cost of laboratory equipment and a reduction in the time required to obtain the results.
Candida-Associated Denture Stomatitis and Murine Models: What Is the Importance and Scientific Evidence?
Authors: Sugio Carolina Yoshi Campos , Garcia Amanda Aparecida Maia Neves , Albach Thaís , Moraes Gustavo Simão , Bonfante Estevam Augusto , Urban Vanessa Migliorini , Neppelenbroek Karin Hermana
Published: May 2020

Considering the high prevalence and recurrence of Candida-associated denture stomatitis (CADS), in vivo studies in animal models are necessary before those in humans to evaluate new therapeutic strategies. This study aimed to review the literature on murine models of CADS induction using acrylic intraoral devices simulating dentures. Rats are recommended as experimental animals in these models as well as the adoption of a pasty diet. For maintenance in the proper position during the experiments, intraoral appliances must be obtained by individual impressions, using and retained exclusively by cementation on the molars. The region of interest for histopathological analysis was standardized as that corresponding to the area between the first molars. However, there is no consensus among the studies on the CADS induction rat models in relation to the Candida albicans inoculation and need for immunosuppression and/or administration of antibacterial drugs of animals. The greatest difficulty of the available models refers to maintaining the course of the lesion for a sufficient period to evaluate the effectiveness of the proposed treatment, considering the rapid and efficient murine immune response to candidal colonization. Therefore, future studies are necessary for the development of a robust and reproducible CADS model.
A Comprehensive Gene Expression Profile of Pectin Degradation Enzymes Reveals the Molecular Events during Cell Wall Degradation and Pathogenesis of Rice Sheath Blight Pathogen Rhizoctonia solani AG1-IA
Authors: Bhaskar Rao Talluri , Chopperla Ramakrishna , Prathi Naresh Babu , Balakrishnan Marudamuthu , Prakasam Vellaisamy , Laha Gouri Sankar , Balachandran Sena Munuswamy , Mangrauthia Satendra K.
Published: May 2020

Sheath blight disease of rice caused by Rhizoctonia solani Kühn (teleomorph: Thanatephorus cucumeris) remains a global challenge due to the absence of reliable resistance genes and poor understanding of pathogen biology. Pectin, one of the most vital constituents of the plant cell wall, is targeted by pectin methylesterases, polygalacturonases, and few other enzymes of fungal pathogens. In this study, we catalogued the expressed genes of the fungal genome from RNAseq of R. solani infected four rice genotypes. Analysis of RNAseq revealed 3325 pathogen genes commonly expressed in all rice genotypes, in which 49, 490, and 83 genes were specific to BPT5204, Tetep, and Pankaj genotypes, respectively. To identify the early and late responding genes of R. solani during plant cell wall degradation, a real-time PCR analysis of 30 pectinolytic enzymes was done at six different time points after inoculation. The majority of these genes showed maximum induction at the 72 h time point, suggesting that it is the most crucial stage of infection. Pankaj showed lesser induction of these genes as compared to other genotypes. Leaf-blade tissue and 45 days old-growth stage are more favorable for the expression of pectin degradation genes of R. solani. Additionally, the expression analysis of these genes from four different strains of R. solani suggested differential regulation of genes but no distinct expression pattern between highly virulent and mild strains. The implications of the differential regulation of these genes in disease development have been discussed. This study provides the first such comprehensive analysis of R. solani genes encoding pectin degrading enzymes, which would help to decipher the pathogen biology and sheath blight disease development.
Spatial Planning, Urban Governance and the Economic Context: The Case of ‘Mehr’ Housing Plan, Iran
Authors: Zanganeh Shahraki Saeed , Ahmadifard Narges , Farhadikhah Hossein , Fotouhi Mehrabani Bagher , Haydari Asghar , Abdali Yaghob , Abbasi Fallah Vahid , Farhadi Ebrahim , Cividino Sirio , Vinci Sabato , Salvati Luca
Published: May 2020

With the increasing concentration of population and economic activities in metropolitan regions, dwelling shortages and housing quality have become critical issues in urban management. Town plans considering social, economic, political, and cultural features of local communities have been developed with the aim of supporting housing, especially in emerging economies. In Iran, the ‘Mehr Housing’ Plan has been considered as one of the most relevant strategies for social housing since the 2000s. However, the acceptance of ‘Mehr Housing’ plans at the community scale has been rather low, reflecting the fact that it is a top-down, non-participatory policy. The present study investigates the most important factors affecting social acceptance of ‘Mehr Housing’ plans by interviewing 45 experts through a structured questionnaire that evaluated multiple analyses’ dimensions of housing and urban planning in Iran. Results showed that six dimensions (physical, institutional-managerial, economic, socio-cultural, legal, and locational) had contributed to social dissatisfaction with ‘Mehr Housing’ local initiatives. In particular, socio-cultural and legal dimensions were demonstrated to have a large impact on local communities’ dissatisfaction.
Test Modes for Establishing the Tribological Profile under Slip-Rolling
Authors: Patzer Gregor , Woydt Mathias , Shah Raj , Miller Curtis , Iaccarino Philip
Published: May 2020

The complex nature of slip-rolling contacts in many applications such as gear tooth flanks, rolling bearings, and heavy machinery often makes determining the friction and wear properties, as well as the fatigue resistance, of tribosystems difficult. The establishment of the tribological profile of a tribocouple under high Hertzian contact pressure and under slip-rolling will allow for the measurement and comparison of friction and wear coefficients as well as slip-rolling resistance by continuously monitoring the wear rate, coefficient of friction, temperature, oil film thickness, and/or electrical contact resistance using high-resolution signal analysis (HRA). A twin disc system can provide insight into the adhesive behavior of material and lubricant products such as alternative base oils and additives, ceramics, alloys, and thin film coatings. The strength and endurance of these products are often characterized through fatigue and resistance tests, which apply high Hertzian contact pressures to the rolling contact until seizure or failure is obtained. The further observation of the formation of tribofilms on the surface of contact yields information about the reactivity and thermochemical properties of additives. This review aims to illustrate how the implementation of different screening methodologies can be used as a meaningful tool for assessing the aforementioned tribological profile properties for the development of slip-rolling tribosystems.
Tribochemical Interactions between Carbon Nanotubes and ZDDP Antiwear Additive during Tribofilm Formation on Uncoated and DLC-Coated Steel
Authors: Dzięgielewski Wojciech , Kowalczyk Joanna , Kulczycki Andrzej , Madej Monika , Ozimina Dariusz
Published: May 2020

The data from the authors’ earlier investigations show that molecules of zinc dithiophosphate (ZDDP) added to a lubricant can absorb energy emitted by a solid surface, which is where triboreactions occur. If the lubricant contains structures able to conduct energy, the ZDDP reactions can occur even at a relatively large distance from the solid surface, which should increase the effectiveness of ZDDP as an antiwear additive. The purpose of this paper was to verify the thesis that the tribocatalytic effect depends on the ability of the solid surface to emit electrons/energy and the ability of ordered molecular structures, such as carbon nanotubes (CNTs), to conduct energy and, most likely, to enhance the energy transfer. The tribological tests were performed using a TRB3 tribotester for 100Cr6 steel balls and uncoated or a-C:H coated HS6-5-2C steel discs. Polyalphaolefin 8 (PAO8) and PAO8 mixed with ZDDP and CNTs were used as lubricants. The results of the tribological tests suggested that: (a) the effect of the interactions between ZDDP and CNTs was clearly visible; (b) the structure and properties of the solid surface layer had a significant influence on the antiwear action of the ZDDP additive.
A Study on Microstructure, Residual Stresses and Stress Corrosion Cracking of Repair Welding on 304 Stainless Steel: Part I-Effects of Heat Input
Authors: Luo Yun , Gu Wenbin , Peng Wei , Jin Qiang , Qin Qingliang , Yi Chunmei
Published: May 2020

In this paper, the effect of repair welding heat input on microstructure, residual stresses, and stress corrosion cracking (SCC) sensitivity were investigated by simulation and experiment. The results show that heat input influences the microstructure, residual stresses, and SCC behavior. With the increase of heat input, both the δ-ferrite in weld and the average grain width decrease slightly, while the austenite grain size in the heat affected zone (HAZ) is slightly increased. The predicted repair welding residual stresses by simulation have good agreement with that by X-ray diffraction (XRD). The transverse residual stresses in the weld and HAZ are gradually decreased as the increases of heat input. The higher heat input can enhance the tensile strength and elongation of repaired joint. When the heat input was increased by 33%, the SCC sensitivity index was decreased by more than 60%. The macroscopic cracks are easily generated in HAZ for the smaller heat input, leading to the smaller tensile strength and elongation. The larger heat input is recommended in the repair welding in 304 stainless steel.
E-Learning in the Teaching of Mathematics: An Educational Experience in Adult High School
Authors: Moreno-Guerrero Antonio-José , Aznar-Díaz Inmaculada , Cáceres-Reche Pilar , Alonso-García Santiago
Published: May 2020

Currently, the e-learning method, due to the period of confinement that is occurring due to COVID-19, has increased its use and application in the teaching and learning processes. The main objective of this research is to identify the effectiveness of the e-learning method in the teaching of mathematics with adults who are in high school, in contrast to the traditional expository method. The study developed is quantitative, descriptive and correlational. The research design is quasi-experimental, with a control group and an experimental group. The results show that the use of the e-learning method has a positive influence on motivation, autonomy, participation, mathematical concepts, results and grades. It can be concluded that the e-learning method leads to improvement in adult students who are studying the mathematical subject in the educational stage of high school, provided that it is compared with the expository method. Therefore, this method is considered effective for its implementation in adults.
Fekete-Szegö Type Problems and Their Applications for a Subclass of q-Starlike Functions with Respect to Symmetrical Points
Authors: Srivastava Hari Mohan , Khan Nazar , Darus Maslina , Khan Shahid , Ahmad Qazi Zahoor , Hussain Saqib
Published: May 2020

In this article, by using the concept of the quantum (or q-) calculus and a general conic domain Ω k , q , we study a new subclass of normalized analytic functions with respect to symmetrical points in an open unit disk. We solve the Fekete-Szegö type problems for this newly-defined subclass of analytic functions. We also discuss some applications of the main results by using a q-Bernardi integral operator.
Existence and Stability Analysis for Fractional Impulsive Caputo Difference-Sum Equations with Periodic Boundary Condition
Authors: Ouncharoen Rujira , Chasreechai Saowaluck , Sitthiwirattham Thanin
Published: May 2020

In this paper, by using the Banach contraction principle and the Schauder’s fixed point theorem, we investigate existence results for a fractional impulsive sum-difference equations with periodic boundary conditions. Moreover, we also establish different kinds of Ulam stability for this problem. An example is also constructed to demonstrate the importance of these results.
A New Wavelet Tool to Quantify Non-Periodicity of Non-Stationary Economic Time Series
Authors: Bolós Vicente J. , Benítez Rafael , Ferrer Román
Published: May 2020

We introduce a new wavelet tool, the windowed scale index, to study the degree of non-periodicity of time series. The windowed scale index is based on some recently defined tools, such as the windowed scalogram and the scale index. This novel measure is appropriate for non-stationary time series whose characteristics change over time and, therefore, it can be applied to a wide variety of disciplines. Furthermore, we revise the concept of the scale index and pose a theoretical problem: it is known that if the scale index of a function is not zero then it is non-periodic, but if the scale index of a function is zero, then it is not proved that it has to be periodic. This problem is solved for the particular case of the Haar wavelet, reinforcing the interpretation of the windowed scale index as a useful tool to quantify non-periodicity. In addition, the applicability of this wavelet-based measure is illustrated through several examples, including an economic application which compares the non-periodicity of two major commodities in the world economy, such as crude oil and gold. Finally, we discuss the relationship between non-periodicity and unpredictability, comparing the windowed scale index with the sample entropy.
Singular Special Curves in 3-Space Forms
Authors: Huang Jie , Pei Donghe
Published: May 2020

We study the singular Bertrand curves and Mannheim curves in the 3-dimensional space forms. We introduce the geometrical properties of such special curves. Moreover, we get the relationships between singularities of original curves and torsions of another mate curves.
A Second-Order Well-Balanced Finite Volume Scheme for the Multilayer Shallow Water Model with Variable Density
Authors: Guerrero Fernández Ernesto , Castro-Díaz Manuel Jesús , Morales de Luna Tomás
Published: May 2020

In this work, we consider a multilayer shallow water model with variable density. It consists of a system of hyperbolic equations with non-conservative products that takes into account the pressure variations due to density fluctuations in a stratified fluid. A second-order finite volume method that combines a hydrostatic reconstruction technique with a MUSCL second order reconstruction operator is developed. The scheme is well-balanced for the lake-at-rest steady state solutions. Additionally, hints on how to preserve a general class of stationary solutions corresponding to a stratified density profile are also provided. Some numerical results are presented, including validation with laboratory data that show the efficiency and accuracy of the approach introduced here. Finally, a comparison between two different parallelization strategies on GPU is presented.
Improved Oscillation Criteria for 2nd-Order Neutral Differential Equations with Distributed Deviating Arguments
Authors: Moaaz Osama , El-Nabulsi Rami Ahmad , Muhsin Waad , Bazighifan Omar
Published: May 2020

In this study, we establish new sufficient conditions for oscillation of solutions of second-order neutral differential equations with distributed deviating arguments. By employing a refinement of the Riccati transformations and comparison principles, we obtain new oscillation criteria that complement and improve some results reported in the literature. Examples are provided to illustrate the main results.
A Novel Technique to Solve the Fuzzy System of Equations
Authors: Mikaeilvand Nasser , Noeiaghdam Zahra , Noeiaghdam Samad , Nieto Juan J.
Published: May 2020

The aim of this research is to apply a novel technique based on the embedding method to solve the n × n fuzzy system of linear equations (FSLEs). By using this method, the strong fuzzy number solutions of FSLEs can be obtained in two steps. In the first step, if the created n × n crisp linear system has a non-negative solution, the fuzzy linear system will have a fuzzy number vector solution that will be found in the second step by solving another created n × n crisp linear system. Several theorems have been proved to show that the number of operations by the presented method are less than the number of operations by Friedman and Ezzati’s methods. To show the advantages of this scheme, two applicable algorithms and flowcharts are presented and several numerical examples are solved by applying them. Furthermore, some graphs of the obtained results are demonstrated that show the solutions are fuzzy number vectors.
Comparison of Supervised Classification Models on Textual Data
Authors: Hsu Bi-Min
Published: May 2020

Text classification is an essential aspect in many applications, such as spam detection and sentiment analysis. With the growing number of textual documents and datasets generated through social media and news articles, an increasing number of machine learning methods are required for accurate textual classification. For this paper, a comprehensive evaluation of the performance of multiple supervised learning models, such as logistic regression (LR), decision trees (DT), support vector machine (SVM), AdaBoost (AB), random forest (RF), multinomial naive Bayes (NB), multilayer perceptrons (MLP), and gradient boosting (GB), was conducted to assess the efficiency and robustness, as well as limitations, of these models on the classification of textual data. SVM, LR, and MLP had better performance in general, with SVM being the best, while DT and AB had much lower accuracies amongst all the tested models. Further exploration on the use of different SVM kernels was performed, demonstrating the advantage of using linear kernels over polynomial, sigmoid, and radial basis function kernels for text classification. The effects of removing stop words on model performance was also investigated; DT performed better with stop words removed, while all other models were relatively unaffected by the presence or absence of stop words.
Convergence of Generalized Lupaş-Durrmeyer Operators
Authors: Qasim Mohd , Mursaleen Mohammad , Khan Asif , Abbas Zaheer
Published: May 2020

The main aim of this paper is to establish summation-integral type generalized Lupaş operators with weights of Beta basis functions which depends on μ having some properties. Primarily, for these new operators, we calculate moments and central moments, weighted approximation is discussed. Further, Voronovskaya type asymptotic theorem is proved. Finally, quantitative estimates for the local approximation is taken into consideration.
Exponential Stabilization of Linear Time-Varying Differential Equations with Uncertain Coefficients by Linear Stationary Feedback
Authors: Zaitsev Vasilii , Kim Inna
Published: May 2020

We consider a control system defined by a linear time-varying differential equation of n-th order with uncertain bounded coefficients. The problem of exponential stabilization of the system with an arbitrary given decay rate by linear static state or output feedback with constant gain coefficients is studied. We prove that every system is exponentially stabilizable with any pregiven decay rate by linear time-invariant static state feedback. The proof is based on the Levin’s theorem on sufficient conditions for absolute non-oscillatory stability of solutions to a linear differential equation. We obtain sufficient conditions of exponential stabilization with any pregiven decay rate for a linear differential equation with uncertain bounded coefficients by linear time-invariant static output feedback. Illustrative examples are considered.
Numerical Solution of Nonlinear Diff. Equations for Heat Transfer in Micropolar Fluids over a Stretching Domain
Authors: Ahmad Farooq , Almatroud A. Othman , Hussain Sajjad , Farooq Shan E. , Ullah Roman
Published: May 2020

A numerical study based on finite difference approximation is attempted to analyze the bulk flow, micro spin flow and heat transfer phenomenon for micropolar fluids dynamics through Darcy porous medium. The fluid flow mechanism is considered over a moving permeable sheet. The heat transfer is associated with two different sets of boundary conditions, the isothermal wall and isoflux boundary. On the basis of porosity of medium, similarity functions are utilized to avail a set of ordinary differential equations. The non-linear coupled ODE’s have been solved with a very stable and reliable numerical scheme that involves Simpson’s Rule and Successive over Relaxation method. The accuracy of the results is improved by making iterations on three different grid sizes and higher order accuracy in the results is achieved by Richardson extrapolation. This study provides realistic and differentiated results with due considerations of micropolar fluid theory. The micropolar material parameters demonstrated reduction in the bulk fluid speed, thermal distribution and skin friction coefficient but increase in local heat transfer rate and couple stress. The spin behavior of microstructures is also exhibited through microrotation vector N ( η ) .
Semantic Segmentation to Develop an Indoor Navigation System for an Autonomous Mobile Robot
Authors: Teso-Fz-Betoño Daniel , Zulueta Ekaitz , Sánchez-Chica Ander , Fernandez-Gamiz Unai , Saenz-Aguirre Aitor
Published: May 2020

In this study, a semantic segmentation network is presented to develop an indoor navigation system for a mobile robot. Semantic segmentation can be applied by adopting different techniques, such as a convolutional neural network (CNN). However, in the present work, a residual neural network is implemented by engaging in ResNet-18 transfer learning to distinguish between the floor, which is the navigation free space, and the walls, which are the obstacles. After the learning process, the semantic segmentation floor mask is used to implement indoor navigation and motion calculations for the autonomous mobile robot. This motion calculations are based on how much the estimated path differs from the center vertical line. The highest point is used to move the motors toward that direction. In this way, the robot can move in a real scenario by avoiding different obstacles. Finally, the results are collected by analyzing the motor duty cycle and the neural network execution time to review the robot’s performance. Moreover, a different net comparison is made to determine other architectures’ reaction times and accuracy values.
Outliers Detection Models in Shewhart Control Charts; an Application in Photolithography: A Semiconductor Manufacturing Industry
Authors: Raji Ishaq Adeyanju , Lee Muhammad Hisyam , Riaz Muhammad , Abujiya Mu’azu Ramat , Abbas Nasir
Published: May 2020

Shewhart control charts with estimated control limits are widely used in practice. However, the estimated control limits are often affected by phase-I estimation errors. These estimation errors arise due to variation in the practitioner’s choice of sample size as well as the presence of outlying errors in phase-I. The unnecessary variation, due to outlying errors, disturbs the control limits implying a less efficient control chart in phase-II. In this study, we propose models based on Tukey and median absolute deviation outlier detectors for detecting the errors in phase-I. These two outlier detection models are as efficient and robust as they are distribution free. Using the Monte-Carlo simulation method, we study the estimation effect via the proposed outlier detection models on the Shewhart chart in the normal as well as non-normal environments. The performance evaluation is done through studying the run length properties namely average run length and standard deviation run length. The findings of the study show that the proposed design structures are more stable in the presence of outlier detectors and require less phase-I observation to stabilize the run-length properties. Finally, we implement the findings of the current study in the semiconductor manufacturing industry, where a real dataset is extracted from a photolithography process.