bluuebunny/crossref_metadata_2025 huggingface dataset:
Structure Identification of Fractional-Order Dynamical Network with Different Orders
Authors: Zhou Mingcong , Wu Zhaoyan
Published: August 2021

Topology structure and system parameters have a great influence on the dynamical behavior of dynamical networks. However, they are sometimes unknown or uncertain in advance. How to effectively identify them has been investigated in various network models, from integer-order networks to fractional-order networks with the same order. In the real world, many systems consist of subsystems with different fractional orders. Therefore, the structure identification of a dynamical network with different fractional orders is investigated in this paper. Through designing proper adaptive controllers and parameter updating laws, two network estimators are well constructed. One is for identifying only the unknown topology structure. The other is for identifying both the unknown topology structure and system parameters. Based on the Lyapunov function method and the stability theory of fractional-order dynamical systems, the theoretical results are analytically proved. The effectiveness is verified by three numerical examples as well. In addition, the designed estimators have a good performance in monitoring switching topology. From the practical viewpoint, the designed estimators can be used to monitor the change of current and voltage in the fractional-order circuit systems.
An Imitation and Heuristic Method for Scheduling with Subcontracted Resources
Authors: Antonova Anna , Aksyonov Konstantin , Aksyonova Olga
Published: August 2021

A scheduling problem with subcontracted resources is widely spread and is associated with the distribution of limited renewable and non-renewable resources, both own and subcontracted ones based on the work’s due dates and the earliest start time. Scheduling’s goal is to reduce the cost of the subcontracted resources. In the paper, application of a few scheduling methods based on scheduling theory and the optimization algorithm is considered; limitations of these methods’ application are highlighted. It is shown that the use of simulation modeling with heuristic rules for allocation of the renewable resources makes it possible to overcome the identified limitations. A new imitation and heuristic method for solving the assigned scheduling problem is proposed. The comparison of the new method with existing ones in terms of the quality of the found solution and performance of the methods is carried out. A case study is presented that allowed a four-fold reduction of the overall subcontracted resources cost in a real project portfolio.
New Inequalities of Cusa–Huygens Type
Authors: Zhu Ling
Published: August 2021

Using the power series expansions of the functions cotx,1/sinx and 1/sin2x, and the estimate of the ratio of two adjacent even-indexed Bernoulli numbers, we improve Cusa–Huygens inequality in two directions on 0,π/2. Our results are much better than those in the existing literature.
Preparation and Characterization of κ-Carrageenan Modified with Maleic Anhydride and Its Application in Films
Authors: Zhou Yuan , Chen Fu-Quan , Chen Si , Xiao Qiong , Weng Hui-Fen , Yang Qiu-Ming , Xiao An-Feng
Published: August 2021

In this work, the physicochemical properties of maleic anhydride (MAH)-modified κ-carrageenan (κCar) (MC) were characterized and compared with those of native κ-carrageenan (NC). The Fourier transform infrared spectrum of MC exhibited that κCar was successfully modified. Thermogravimetric analysis indicated that the thermal stability of MC was decreased. When the degree of substitution was 0.032, MC exhibited a low gel strength (759 g/cm2), gelling temperature (33.3 °C), and dehydration rate (60.3%). Given the excellent film-forming ability of κCar, MC films were then prepared and were found to have better mechanical and barrier properties (UV and water) than NC films. With regard to optical properties, MC films could completely absorb UV light in the range of 200–236 nm. The water contact angle of MC films was higher than that of NC films. Moreover, the elongation at break increased from 26.9% to 163%. These physicochemical property changes imply that MC can be employed in polysaccharide-based films.
Elemental Composition and Cell Mass Quantification of Cultured Thraustochytrids Unveil Their Large Contribution to Marine Carbon Pool
Authors: Sen Biswarup , Li Jiaqian , Lu Lyu , Bai Mohan , He Yaodong , Wang Guangyi
Published: August 2021

The element stoichiometry of bacteria has received considerable attention because of their significant role in marine ecosystems. However, relatively little is known about the composition of major structural elements of the unicellular heterotrophic protists—thraustochytrids, despite their widely recognized contribution to marine nutrient cycling. Here, we analyze the cell volume and elemental C, N, H, and S cell content of seven cultured thraustochytrids, isolated from different marine habitats, in the exponential and stationary growth phases. We further derive the relationships between the cell volume and elemental C and N content of the cultured thraustochytrids. The cell volumes varied significantly (p < 0.001) among the isolates, with median values of 96.9 and 212.5 μm3 in the exponential and stationary phases, respectively. Our results showed a significantly higher percentage of C (64.0 to 67.5) and H (9.9 to 13.2) but a lower percentage of N (1.86 to 2.16) and S (0.34 to 0.91) in the stationary phase, along with marked variations of C and N fractions among isolates in the exponential phase. The cell C (5.7 to 203.7 pg) and N (0.65 to 6.1 pg) content exhibited a significant (p < 0.001) linear relationship with the cell volume (27.7 to 510 μm3). On further analysis of the relationship across the two growth phases, we found the equation (cell C (pg) = 0.356 × cell volume (μm3) + 20.922) for stationary phase cells more appropriate for C estimation of natural thraustochytrids. This study provides the first experimental evidence of higher cell C density than the current estimate and relatively larger C contribution of thraustochytrids than bacteria to the marine organic pool.
Influence of SARS-CoV-2 Virus Infection on the Course of Psoriasis during Treatment with Biological Drugs
Authors: Mroz Magdalena , Mućka Szymon , Miodońska Martyna , Ziolkowska Dominika , Hadas Ewa , Bożek Andrzej
Published: August 2021

Background and objectives: Biological treatment is an important and effective therapy for psoriasis. During the COVID-19 pandemic, it remains unclear whether this type of therapy affects the course of SARS-CoV-2 infection. The aim of the study was to observe patients with psoriasis undergoing biological or other systemic treatment in relation to the impact of SARS-CoV-2 infection on the course of psoriasis and the COVID-19 disease itself. Materials and methods: A one-year observational study included 57 patients with diagnosed psoriasis who qualified for biological treatment and a group of 68 similar patients who were administered a different systemic treatment. Patients were analyzed monthly for psoriasis (including Psoriasis Area Severity Index (PASI) assessment) and constantly for SARS-CoV-2 infection (telephone contact). Cases of COVID-19 were confirmed by Polymerase Chain Reaction (PCR) at the study center. Results: SARS-CoV-2 infection was confirmed by a positive Real Time Polymerase Chain Reaction (RT-PCR) test in eight patients (14.0%) with psoriasis on biological therapy. None of the cases in this group required hospitalization for COVID-19. Similar data were obtained in the control group. Specifically, 11 (16%) patients were confirmed to be infected with SARS-CoV-2. These results were statistically comparable (p > 0.05). In the group of patients undergoing biological treatment, six (75%) of eight patients developed an exacerbation of psoriasis during SARS-CoV-2 infection, and similar results were noted in the control group, with eight (72%) patients experiencing an exacerbation of psoriasis. Conclusions: Patients with psoriasis who were administered biological treatment or other systemic therapy may experience a mild course of SARS-CoV-2 infection but might also experience a temporary exacerbation of skin lesions.
Changes in Health Perception among Patients with Aortic Diseases in a Severe COVID-19 Area in the West of Germany: A Longitudinal Study between the First and Second Wave of the COVID-19 Pandemic
Authors: Parys Alan , Klinge Sarah , Dönmez Alina , Rammos Christos , Rassaf Tienush , Jánosi Rolf Alexander , Lortz Julia
Published: August 2021

Background and Objectives: The rapid spread of the novel coronavirus disease (COVID-19) has become the most challenging global health pandemic since the 1918 flu. In Germany, more than 3.4 million cases are confirmed so far, including 83,000 deaths. Increased fatality rates among patients with pre-existing cardiovascular diseases (CVD) represent this group at particular risk. The aim of this study was to evaluate changes in health perception among patients with aortic diseases during the first (w1) and second wave (w2) of the COVID-19 pandemic in Germany. Material and Methods: Patients (n = 262) diagnosed with aortic disease participated in telephone interviews during w1 and w2. The perception of COVID-19 as a threat was examined using relevant items of the Brief Illness Perception (BIP) questionnaire. Results: The BIP score increased from 9.18 (SD = 7.132) to 14.58 (SD = 6.956) between w1 and w2 (p < 0.001). Although this population is at high risk their overall perception of COVID-19 as a threat was low in the beginning, but surged during w2. Main reasons were increased effects on personal life and elevated concerns about the pandemic, but did not include the educational aspect of COVID-19. Conclusions: Tailored risk communication strengthens the mental health of people in a public health crisis and ensures the success of governmental guidelines.
Is Non-Stimulated C-Peptide at Diagnosis a Good Predictive Value for Insulin Use at Two Years after Diagnosis in Pediatric Diabetic Patients?
Authors: Chou Wei-Chih , Chou Yen-Yin , Pan Yu-Wen , Tsai Meng-Che
Published: August 2021

Background and Objectives: Insulin treatment may be initially required to stabilize patients presenting with metabolic crisis at type 1 and 2 diabetes mellitus (DM) onset. Some patients with type 2 DM may need persistent insulin treatment. This study aimed to examine the predictive performance of non-stimulated C-peptide level at the time of diagnosis for future insulin use in pediatric diabetic patients. Materials and Methods: We reviewed the medical charts of diabetic patients aged 18 years or younger in a medical center in southern Taiwan from January 2000 to December 2019. Clinical and individual data were collected at the time of DM diagnosis. Outcomes were persistent insulin use at the time of diagnosis, as well as at one and two years after diagnosis. Results: The final analysis included a total of 250 patients. The best cut-off point of non-stimulated C-peptide was 0.95 ng/mL, and the predictive indices for the insulin use were 0.84 for sensitivity and 0.94 for specificity at two years after DM diagnosis. Incorporating age at onset and presence of GAD antibodies can further increase the predictive power of non-stimulated C-peptide. Conclusions: The value of non-stimulated C-peptide at diabetic onset was feasible and effective for predicting future insulin treatment up to the time point of two years after diagnosis.
Pilot Study on the Use of the “Monocyte-Rich” Platelet-Rich Plasma in Combination with 1927 nm Fractional and 308 nm Excimer Lasers for the Treatment of Vitiligo
Authors: Mercuri Santo Raffaele , Di Nicola Matteo Riccardo , Brianti Pina , Bianchi Vittoria Giulia , Paolino Giovanni
Published: August 2021

Background and objectives: Vitiligo is an acquired chronic and idiopathic skin disorder, characterized by selective loss of melanocytes and resulting in a cutaneous depigmentation. Treatment for vitiligo remains a challenge for dermatologists; thus, it is frustrating both for physicians and patients. The objective of this study was to evaluate a combination treatment characterized by the use of a leukocyte-rich platelet-rich plasma, which is particularly rich in monocytes (defined here as monocyte-rich PRP), in combination with a 1927 nm fraxel laser and a 308 nm excimer laser. Materials and Methods: Treatment with monocyte-rich PRP combined with 1927 nm fraxel laser and 308 nm excimer laser was performed in nine sessions in 80 days and the median follow-up of the patients was 10 months. A total of 27 Caucasian patients were included in the present study. The median age of patients was 41 years, ranging between 20 and 69 years. Results: A re-pigmentation occurred in 16 cases (59%) with a reduction of the Vitiligo Extent Score (VES) and absence of re-pigmentation in untreated areas. Performing a rank correlation between VES and re-pigmentation in the treated areas, we found that there was a significant correlation (p < 0.0001). The presence of progressive vitiligo (p = 0.1) and the anatomic areas (p = 0.1) did not influence the treatment. Untreated areas did not show any improvement of the depigmented lesions, except in one case (p < 0.0001). Conclusions: in this report, we show for the first time how PRP rich in monocytes, in combination with laser therapies, gives a long therapeutic response, which persists even after 10 months of follow-up.
Hybrid Surgery to Manage Aortic Arch Pathology
Authors: Gelpi Guido , Romagnoni Claudia , Epifani Francesco , Contino Monica , Antona Carlo
Published: August 2021

Background and Objectives: Aortic arch disease is still a high-risk surgical challenge despite major advances both in surgical and anesthesiological management. A combined surgical and endovascular approach has been proposed for aortic arch disease treatment to avoid hypothermia and circulatory arrest in high-risk patients. Materials and Methods: Between June 2004 and June 2021, 112 patients were referred to our department for aortic arch surgery; 38 (33.9%) patients underwent supra-aortic debranching and endovascular treatment. Of these, 21 (55%) patients underwent type I aortic arch hybrid debranching procedure and in 17 (45%) patients a type II aortic arch hybrid debranching procedure was performed. None of the patients were emergent. Results: No intra-operative deaths were recorded. In the type I aortic arch hybrid debranching patients’ group, one patient died at home waiting the endovascular step, one developed ascending aortic dissection and another one developed a pseudoaneurysm at the site of the debranching at follow-up. In the type II aortic arch hybrid debranching patients’ group, left carotid artery branch closure was detected at follow-up in one patient. Thirty day/in-hospital rates of adverse neurological events for both the surgical and endovascular procedures were 3% for minor stroke, with no permanent neurological deficit and 0% for permanent paraplegia/paraparesis. In 100% of the cases, the endovascular step succeeded and the type Ia endoleak rate was 0%. Conclusions: Hybrid arch surgery is a valuable option for aortic arch aneurysm treatment in patients with high surgical risk. The choice of aortic arch debranching between type I or type II is crucial and depends on anatomic and clinical patient characteristics. Further larger scale studies are needed to better define the advantages of these techniques.
Association of Periodontal Disease with the Occurrence of Unruptured Cerebral Aneurysm among Adults in Korea: A Nationwide Population-Based Cohort Study
Authors: Woo Ho-Geol , Chang Yoon-Kyung , Lee Ji-Sung , Song Tae-Jin
Published: August 2021

Background and Objectives: Cerebral aneurysms can cause disability or death during rupture, but information on the etiology of cerebral aneurysms is currently lacking. Periodontal disease causes both systemic inflammation and local inflammation of the oral cavity. Systemic inflammation is a major cause of cerebral aneurysms. The aim of our study was to determine whether the presence of periodontal disease is related to the occurrence of unruptured cerebral aneurysms in a nationwide population-based cohort. Materials and Methods: We analyzed data on demographics, previous medical history, and laboratory test results of 209,620 participants from the Korean National Health Insurance System-Health Screening Cohort. The presence of periodontal disease and oral hygiene parameters, including the number of lost teeth, tooth brushing frequency per day, dental visits for any reason, and expert teeth scaling, were investigated. The occurrences of unruptured cerebral aneurysms (I67.1) were defined according to the International Statistical Classification of Diseases Related Health Problems-10. Results: The mean age of the participants was 53.7 ± 8.7 years, and 59.4% were male. Periodontal disease was found in 20.9% of the participants. A total of 2160 (1.0%) cases of unruptured cerebral aneurysms developed after 10.3 years of median follow up. In multivariate analysis, the presence of periodontal disease was significantly associated with an increased risk of unruptured cerebral aneurysms (hazard ratio: 1.21, 95% confidence interval: 1.09–1.34, p < 0.001). Conclusion: The presence of periodontal disease could be associated with the occurrence of unruptured cerebral aneurysms. It should be noted that when periodontal diseases are present, the risk of aneurysms is increased in the future.

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Effects of Pressure Control Device (SensAwake™) on Obstructive Sleep Apnea (OSA) Patients Who Remove the Mask for Unknown Reasons during Automatic Continuous Positive Airway Pressure (Auto-CPAP) Therapy: A Prospective Randomized Crossover Trial
Authors: Chen Yen-Lung , Chuang Li-Pang , Lin Shih-Wei , Huang Hung-Yu , Liu Geng-Hao , Hsu Hung-Fu , Chen Ning-Hung
Published: August 2021

Backgroundand Objectives: Obstructive sleep apnea (OSA) patients may remove their mask unconsciously during automatic continuous positive airway pressure (Auto-CPAP) therapy and therefore cannot receive good treatment. The discomfort from the airflow of Auto-CPAP may be one reason for interrupted sleep. Sens Awake (SA) can detect the arousal and lower the pressure to prevent patients from fully awakening from sleep. Materials and Methods: To evaluate the effect of SA, we designed a prospective, randomized, crossover trial comparing Auto-CPAP with and without SA on Epworth Sleepiness Scale (ESS), Pittsburgh Sleep Quality Index (PSQI), Nasal Obstruction Symptom Evaluation (NOSE) Scale and recorded data from the auto-CPAP machine. Results: In the 25 patients who completed the study, the gender, age, body mass index, neck circumference, polysomnography data, and previous CPAP use were not significantly different between the two arms. The average and 90th percentile pressures were significantly lower during SA on (SA on vs. off: 6.9 ± 2.7 vs. 7.3 ± 2.6 [p = 0.032] and 8.6 ± 3.0 vs. 9.2 ± 2.9 [p = 0.002], respectively). The time used, days used, compliance, average and 90th percentile leaks, and the residual Apnea-Hypopnea Index (AHI) were not significantly changed between the SA on-and-off. Based on the subjective evaluation, PSQI, ESS, and NOSE were not significantly different between the SA on-and-off; however, based on additional analyses which were compared with baseline data, the ESS was significantly lower when the SA was on (SA on vs. baseline: 11.1 ± 6.1 vs. 13.2 ± 6.0 [p = 0.023]). Conclusions: CPAP therapy with or without two weeks of the SA had a similar effect on CPAP use, sleep quality, daytime sleepiness, and nasal obstruction. The SA may have a tendency to improve daytime sleepiness, but needs further study with a longer duration of treatment.
Optimization of Spiral-Wound Microfiltration Process Parameters for the Production of Micellar Casein Concentrate
Authors: Marella Chenchaiah , Sunkesula Venkateswarlu , Hammam Ahmed R. A. , Kommineni Anil , Metzger Lloyd E.
Published: August 2021

A systematic selection of different transmembrane pressures (TMP) and levels of diafiltration (DF) was studied to optimize these critical process parameters during the manufacturing of micellar casein concentrate (MCC) using spiral-wound polymeric membrane filtration. Three TMPs (34.5, 62.1, and 103.4 kPa) and four DF levels (0, 70, 100, and 150%) were applied in the study. The effect of the TMP and DF level on flux rates, serum protein (SP) removal, the casein-to-total-protein ratio, the casein-to-true-protein ratio, and the rejection of casein and SP were evaluated. At all transmembrane pressures, the overall flux increased with increases in the DF level. The impact of DF on the overall flux was more pronounced at lower pressures than at higher pressures. With controlled DF, the instantaneous flux was maintained within 80% of the initial flux for the entire process run. The combination of 34.5 kPa and a DF level of 150% resulted in 81.45% SP removal, and a casein-to-true-protein ratio of 0.96. SP removal data from the lab-scale experiments were fitted into a mathematical model using DF levels and the square of TMPs as factors. The model developed in this study could predict SP removal within 90–95% of actual SP removal achieved from the pilot plant experiments.
Porous Medium Equation in Graphene Oxide Membrane: Nonlinear Dependence of Permeability on Pressure Gradient Explained
Authors: Mrazík Lukáš , Kříž Pavel
Published: August 2021

Membrane performance in gas separation is quantified by its selectivity, determined as a ratio of measured gas permeabilities of given gases at fixed pressure difference. In this manuscript a nonlinear dependence of gas permeability on pressure difference observed in the measurements of gas permeability of graphene oxide membrane on a manometric integral permeameter is reported. We show that after reasoned assumptions and simplifications in the mathematical description of the experiment, only static properties of any proposed governing equation can be studied, in order to analyze the permeation rate for different pressure differences. Porous Medium Equation is proposed as a suitable governing equation for the gas permeation, as it manages to predict a nonlinear behavior which is consistent with the measured data. A coefficient responsible for the nonlinearity, the polytropic exponent, is determined to be gas-specific—implications on selectivity are discussed, alongside possible hints to a deeper physical interpretation of its actual value.
Highly Segregated Biocomposite Membrane as a Functionally Graded Template for Periodontal Tissue Regeneration
Authors: Qasim Syed Saad B. , Baig Mirza Rustum , Matinlinna Jukka Pekka , Daood Umer , Al-Asfour Adel
Published: August 2021

Guided tissue regeneration (GTR) membranes are used for treating chronic periodontal lesions with the aim of regenerating lost periodontal attachment. Spatially designed functionally graded bioactive membranes with surface core layers have been proposed as the next generation of GTR membranes. Composite formulations of biopolymer and bioceramic have the potential to meet these criteria. Chitosan has emerged as a well-known biopolymer for use in tissue engineering applications due to its properties of degradation, cytotoxicity and antimicrobial nature. Hydroxyapatite is an essential component of the mineral phase of bone. This study developed a GTR membrane with an ideal chitosan to hydroxyapatite ratio with adequate molecular weight. Membranes were fabricated using solvent casting with low and medium molecular weights of chitosan. They were rigorously characterised with scanning electron microscopy, Fourier transform infrared spectroscopy in conjunction with photoacoustic sampling accessory (FTIR-PAS), swelling ratio, degradation profile, mechanical tensile testing and cytotoxicity using human osteosarcoma and mesenchymal progenitor cells. Scanning electron microscopy showed two different features with 70% HA at the bottom surface packed tightly together, with high distinction of CH from HA. FTIR showed distinct chitosan dominance on top and hydroxyapatite on the bottom surface. Membranes with medium molecular weight showed higher swelling and longer degradation profile as compared to low molecular weight. Cytotoxicity results indicated that the low molecular weight membrane with 30% chitosan and 70% hydroxyapatite showed higher viability with time. Results suggest that this highly segregated bilayer membrane shows promising potential to be adapted as a surface layer whilst constructing a functionally graded GTR membrane on its own and for other biomedical applications.
The Effect of Far-Infrared Therapy on the Peritoneal Membrane Transport Characteristics of Uremic Patients Undergoing Peritoneal Dialysis: An Open-Prospective Proof-of-Concept Study
Authors: Li Ching-Po , Chen Chyong-Mei , Chan Chia-Hao , Li Szu-Yuan , Tsai Ming-Tsun , Chen Chun-Fan , Chen Yung-Tai , Chen Tz-Heng , Chen Fan-Yu , Yang Ching-Han , Chou Yi-Hsin , Wang Tsung-Yueh , Tan Ann Charis , Lin Chih-Ching
Published: August 2021

Long-term peritoneal dialysis (PD) can lead to detrimental changes in peritoneal membrane function, which may be related to the accumulation of glucose degradation products. A previous study demonstrated that 6 months of far-infrared (FIR) therapy may decrease glucose degradation products in PD dialysate. Due to limited literature on this matter, this study aims to investigate the effect of FIR therapy on the peritoneal membrane transport characteristics of PD patients. Patients were grouped according to baseline peritoneal transport status: lower transporters (low and low-average) and higher transporters (high-average and high). Both groups underwent 40 min of FIR therapy twice daily for 1 year. In lower transporters, FIR therapy increased weekly dialysate creatinine clearance (6.91 L/wk/1.73 m2; p = 0.04) and D/P creatinine (0.05; p = 0.01). In higher transporters, FIR therapy decreased D/P creatinine (−0.05; p = 0.01) and increased D/D0 glucose (0.05; p = 0.006). Fifty percent of high transporter patients shifted to high-average status after FIR therapy. FIR therapy may decrease D/P creatinine for patients in the higher transporter group and cause high transporters to shift to high-average status, which suggests the potential of FIR therapy in improving peritoneal membrane function in PD patients.
Role of NaCl, CO2, and H2S on Electrochemical Behavior of 304 Austenitic Stainless Steel in Simulated Oil Industry Environment
Authors: Abdo Hany S. , Seikh Asiful H.
Published: August 2021

The electrochemical behavior of 304 austenitic stainless steel (304ASS) was studied by different methods such as potentiodynamic polarization, EIS, SEM, and Raman spectroscopy. Potentiodynamic polarization data suggest that 304 ASS could be more susceptible to corrosion due to the presence of H2S. The coexistence of H2S and Cl−-type ionic species in 304 ASS lead to a decrease in the corrosion resistance as compared to the H2S-free condition. It is seen that CO2 helps form a passive layer on the metallic surface, which eventually decreases its corrosion rate. Raman spectroscopy analysis shows that the passive layer developed under different condition consists of FeCO3, FeS2, Fe2O3, Fe(OH)2, etc. SEM images further confirm that elemental S− and Cl− can infiltrate the passive film and cause the passive film to deteriorate.
Application and Evaluation of Mathematical Models for Prediction of the Electric Energy Demand Using Plant Data of Five Industrial-Size EAFs
Authors: Reimann Alexander , Hay Thomas , Echterhof Thomas , Kirschen Marcus , Pfeifer Herbert
Published: August 2021

The electric arc furnace (EAF) represents the most important process route for recycling of steel and the second most productive steelmaking process overall. Considering the large production quantities, the EAF process is subject to continuous optimization, and even small improvements can lead to a significant reduction in resource consumption and operating cost. A common way to investigate the furnace operation is through the application of mathematical models. In this study the applicability of three different statistical modeling approaches for prediction of the electric energy demand is investigated by using more than 21,000 heats from five industrial-size EAFs. In this context, particular consideration is given to the difference between linear and nonlinear regression models. Detailed information on the treatment of the process data is provided and the applied methods for regression are described in short, including information on the choice of hyperparameters. Subsequently, the results of the models are compared. Gaussian process regression (GPR) was found to yield the best overall accuracy; however, the benefit of applying nonlinear models varied between the investigated furnaces. In this regard, possible reasons for the inconsistent performance of the methods are discussed.
The Role of Retained Austenite in Tempered Martensite Embrittlement of 4340 and 300-M Steels Investigated through Rapid Tempering
Authors: Euser Virginia K. , Williamson Don L. , Findley Kip O. , Clarke Amy J. , Speer John G.
Published: August 2021

Tempered martensite embrittlement (TME) is investigated in two medium carbon, high strength steels, 4340 (low silicon) and 300-M (high silicon), via rapid (1, 10, or 100 s) and conventional (3600 s) tempering. Rapid tempering of 4340 diminishes the depth of the TME toughness trough, where improvements in impact toughness correspond to the suppression of retained austenite decomposition. In 300-M, retained austenite decomposition is suppressed to an even greater extent by rapid tempering. While toughness improves overall after rapid tempering, TME severity remains consistent in 300-M across the tempering conditions examined. Through interrupted tensile tests, it was found that the 300-M conditions that exhibit TME are associated with mechanically unstable retained austenite. Unstable retained austenite is shown to mechanically transform early in the deformation process, presumably resulting in fresh martensite adjacent to interlath cementite that ultimately contributes to TME. The present results emphasize the role of both the thermal decomposition and mechanical transformation of retained austenite in the manifestation of TME.
Effects of Oxygen Precursor on Resistive Switching Properties of CMOS Compatible HfO2-Based RRAM
Authors: Ryu Hojeong , Kim Sungjun
Published: August 2021

In this work, we investigate the resistive switching behaviors of HfO2-based resistive random-access memory (RRAM) in two different oxidants (H2O and O3) in an atomic layer deposition system. Firstly, the surface characteristics of the Ni/HfO2/Si stack are conducted by atomic force microscopy (AFM). A similar thickness is confirmed by scanning electron microscope (SEM) imaging. The surface roughness of the HfO2 film by O3 (O3 sample) is smoother than in the sample by H2O (H2O sample). Next, we conduct electrical characteristics by current–voltage (I–V) and capacitor–voltage (C–V) curves in an initial process. The forming voltage of the H2O sample is smaller than that of the O3 sample because the H2O sample incorporates a lot of H+ in the film. Additionally, the smaller capacitor value of the H2O sample is obtained due to the higher interface trap in H2O sample. Finally, we compare the resistive switching behaviors of both samples by DC sweep. The H2O sample has more increased endurance, with a smaller on/off ratio than the O3 sample. Both have good non-volatile properties, which is verified by the retention test.
Joint Reduction of NiO/WO3 Pair and NiWO4 by Mg + C Combined Reducer at High Heating Rates
Authors: Zakaryan Marieta , Nazaretyan Khachik , Aydinyan Sofiya , Kharatyan Suren
Published: August 2021

Functional features of Ni-W composite materials combined with successful performance enabled a breakthrough in their broad application. To disclose the formation pathway of Ni-W composite materials at extreme conditions of combustion synthesis in the NiO-WO3-Mg-C and NiWO4-Mg-C systems for the optimization of the synthesis procedure, the process was modeled under programmed linear heating conditions by thermal analysis methods. The reduction kinetics of tungsten and nickel oxides mixture and nickel tungstate by Mg + C combined reducer at non-isothermal conditions was studied at high heating rates (100–1200 °C min−1) by high-speed temperature scanner techniques. It was shown that when moving from low heating to high heating rates, the mechanism of both the magnesiothermic and magnesio-carbothermic reductions of the initial mixtures changes; that is, the transition from a solid-solid scheme to a solid-liquid scheme is observed. The strong influence of the heating rate on the reduction degree and kinetic parameters of the systems under study was affirmed. The simultaneous utilization of magnesium and carbon as reducers allowed the lowering of the starting and maximum temperatures of reduction processes, as evidenced by the synergetic effect at the utilization of a combined reducer. The effective values of activation energy (Ea) for the reactions proceeding in the mixtures NiO + WO3 + 4Mg, NiO + WO3 + 2.5Mg + 1.5C, NiWO4 + 4Mg and NiWO4 + 2Mg + 2C were estimated by Kissinger isoconversional method and were 146 ± 10, 141 ± 10, 216 ± 15 and 148 ± 15 kJ mol−1, respectively.
The Effects of Coexisting Copper, Iron, Cobalt, Nickel, and Zinc Ions on Gold Recovery by Enhanced Cementation via Galvanic Interactions between Zero-Valent Aluminum and Activated Carbon in Ammonium Thiosulfate Systems
Authors: Jeon Sanghee , Bright Sharrydon , Park Ilhwan , Tabelin Carlito Baltazar , Ito Mayumi , Hiroyoshi Naoki
Published: August 2021

The use of galvanic interactions between zero-valent aluminum (ZVAl) and activated carbon (AC) to recover gold (Au) ions is a promising technique to overcome the challenges due to the poor recovery in ammonium thiosulfate systems, but the applicability to practical Au ore processing remains elusive so far. The present study describes (1) the recovery of Au ions from low Au concentrations, which are typical concentrations used in Au ore processing; and (2) an investigation into the effects of various coexisting base metal ions that can be present in pregnant ore-leached solutions. The results showed that high Au recovery (i.e., over 85%) was obtained even at low Au concentrations under the following conditions: 1:1 of 0.15 g of ZVAl and AC with 10 mL of ammonium thiosulfate solution containing 5 mg/L of Au ions at 25 °C for 1 h in an anoxic atmosphere. Selected coexisting metal ions (i.e., copper, iron, cobalt, nickel, and zinc) were studied to establish their effects on Au recovery, and the results showed that the Au recovery was enhanced (about 90%) when copper ions coexist in the solution with minimal effects from other competing base metal ions.
Peculiarities of High-Energy Induction Heating during Surface Hardening in Hybrid Processing Conditions
Authors: Skeeba Vadim Y. , Ivancivsky Vladimir V. , Martyushev Nikita V.
Published: August 2021

This paper presents the results obtained when combining mechanical and surface-thermal operations, using the same process equipment. The paper also demonstrates the possibility of implementing high-energy heating with high-frequency currents, and proposes using an integral temperature–time characteristic as the main parameter to specify surface quenching modes. The numerical values of the integral temperature–time characteristic are to be related to the processing modes and the depth of hardening. The experiments confirmed that an increase in the capacity will be commensurate with an increase in power consumption when a volumetric heating scheme (with a hardening depth of 0.5 mm) is realized. However, during the realization of a volumetric heating scheme, when the 0.7 mm depth of the hardened layer is at the boundary of the “hot” depth of the current penetration into the metal (the beginning of the intermediate heating scheme), the increase in the processing capacity will be higher than that in power consumption.
Energetic Materials Based on W/PTFE/Al: Thermal and Shock-Wave Initiation of Exothermic Reactions
Authors: Saikov Ivan , Seropyan Stepan , Malakhov Andrey , Saikova Gulnaz , Denisov Igor , Petrov Evgenii
Published: August 2021

The parameters of combustion synthesis and shock-wave initiation of reactive W/PTFE/Al compacts are investigated. Preliminary thermodynamic calculations showed the possibility of combustion of the W/PTFE/Al system at high adiabatic temperatures (up to 2776 °C) and a large proportion of condensed combustion products. The effect of the Al content (5, 10, 20, and 30 wt%) in the W/PTFE/Al system on the ignition and development of exothermic reactions was determined. Ignition temperatures and combustion rates were measured in argon, air, and rarefied air. A correlation between the gas medium, rate, and temperature of combustion was found. The shock initiation in W/PTFE/Al compacts with different Al content was examined. The extent of reaction in all compacts was studied by X-ray diffraction. The compositions with 10 and 20 wt% Al showed the highest completeness of synthesis after combustion and shock-wave initiation.
Mg-Ca0.3 Electrochemical Activity Exposed to Hank’s Physiological Solution and Properties of Ag-Nano-Particles Deposits
Authors: González-Murguía José Luis , Veleva Lucien , Rodríguez-Gattorno Geonel , Figueroa-Torres Mayra Zyzlila , Feliu Sebastián
Published: August 2021

This work compares the degradation of Mg and Mg-Ca0.3 alloy when they are exposed for 14 days to Hank’s solution at 37 °C. A combination of immersion test, electrochemical techniques (PDP, EIS, EN), and surface characterization methods (SEM-EDS, XRD, and XPS) were carried out. The pH change over time, the lower mass loss (≈20%), and the lower concentration of the released Mg2+ ions (≈3.6 times), as well as the lower level of the surface degradation, allowed to consider the positive effect of Ca, presenting Mg-Ca0.3 alloy with lower electrochemical activity than that of Mg. The positive effect of Ca may be due to the formed layer characteristics on the alloy surface, which impedes the cathodic hydrogen evolution and Mg-ions release. The electroless deposited Ag-nano-particles (Ag-NPs) on Mg-Ca0.3 surface were characterized by SEM-EDS, XRD, UV-Vis, and contact angle. The agar-diffusion test was used to compare the growth of Staphylococcus aureus and Escherichia coli bacteria on Mg-Ca0.3 in the presence of Ag-NPs deposits in different size. Zeta-potential of the bacteria was negative, with respect to pH of the Mueller-Hinton culture broth. The greater antibacterial effect of S. aureus was attributed to its more negative zeta-potential, attracting more released Ag+ ions.
Experimental and Finite Element Study of Polymer Infilled Tube-in-Tube Buckling Restrained Brace
Authors: Alemayehu Robel Wondimu , Kim Youngsik , Park Min Jae , Park Manwoo , K. Ju Young
Published: August 2021

This study presents a tube-in-tube buckling-restrained brace (BRB) infilled with lightweight and rapid hardening polymer. The proposed BRB consists of a circular or square tube core encased with a tube of similar shape and polymer infill. The tube-in-tube arrangement minimizes the filler material volume and enables the use of rolled steel section as opposed to welded profiles commonly utilized when large BRB axial strength is required, although welded profiles suffer from low assembly accuracy resulting from welding deformation. The infilled polymer has a density of approximately half that of mortar and requires a curing time of 24 h, enabling weight and fabrication time reduction. The stability and inelastic deformation capability of the BRB were investigated through brace and subassembly tests of six circular and four-square full-scale specimens, followed by finite element analysis. The test results show that circular BRB designed with a Pcr/Py ratio of 1.46 exhibited a stable hysteresis up to 1.42% and 1.06% core strain in tension and compression, respectively. Circular and square specimens designed with Pcr/Py ratios ranging from 0.82 to 1.06 exhibited stable hysteresis before failing by global buckling at compressive core stains ranging from 0.86% to 1.09%. The slot weld detail adopted for welding core projection stiffener displayed a stable performance in circular BRB specimens, while it resulted in large plastic strain demand in square BRB specimens, leading to core fracture at tensile core strains ranging from 0.64% to 0.71%.
Thermodynamic Optimization of the Ternary Ga-Sn-Te System Using Modified Quasichemical Model
Authors: Kumar Bhupendra , Paliwal Manas , Tiwary Chandra Sekhar , Paek Min-Kyu
Published: August 2021

Thermoelectric (TE) materials are of great interest to many researchers because they directly convert electric and thermal energy in a solid state. Various materials such as chalcogenides, clathrates, skutterudites, eutectic alloys, and intermetallic alloys have been explored for TE applications. The Ga-Sn-Te system exhibits promising potential as an alternative to the lead telluride (PbTe) based alloys, which are harmful to environments because of Pb toxicity. Therefore, in this study, thermodynamic optimization and critical evaluation of binary Ga-Sn, binary Sn-Te, and ternary Ga-Sn-Te systems have been carried out over the whole composition range from room temperature to above liquidus temperature using the CALPHAD method. It is observed that Sn-Te and Ga-Te liquids show the strong negative deviation from the ideal solution behavior. In contrast, the Ga-Sn liquid solution has a positive mixing enthalpy. These different thermodynamic properties of liquid solution were explicitly described using Modified Quasichemical Model (MQM) in the pair approximation. The asymmetry of ternary liquid solution in the Ga-Sn-Te system was considered by adopting the toop-like interpolation method based on the intrinsic property of each binary. The solid phase of SnTe was optimized using Compound Energy Formalism (CEF) to explain the high temperature homogeneity range, whereas solid solution, Body-Centered Tetragonal (BCT) was optimized using a regular solution model. Thermodynamic properties and phase diagram in the Ga-Sn-Te and its sub-systems were reproduced successfully by the optimized model parameters. Using the developed database, we also suggested several ternary eutectic compositions for designing TE alloy with improved properties.
Thermal Decomposition and Kinetics of Pentlandite-Bearing Ore Oxidation in the Air Atmosphere
Authors: Božinović Kristina , Štrbac Nada , Mitovski Aleksandra , Sokić Miroslav , Minić Duško , Marković Branislav , Stojanović Jovica
Published: August 2021

The roasting of sulfide ores and concentrates is one of the most important steps in pyrometallurgical metal production from primary raw materials, due to the necessity of excess sulfur removal, present in the virgin material. Pentlandite is one of the main sources for nickel pyrometallurgical production. The knowledge of its reaction mechanism, products distribution during oxidation and reaction kinetics is important for optimizing the production process. Raw pentlandite-bearing ore from the Levack mine (Ontario, Canada) was subjected to oxidative roasting in the air atmosphere. A chemical analysis of the initial sample was conducted according to EDXRF (Energy-Dispersive X-ray Fluorescence) and AAS (Atomic Adsorption Spectrometry) results. The characterization of the initial sample and oxidation products was conducted by an XRD (X-ray Diffraction) and SEM/EDS (Scanning Electron Microscopy with Energy Dispersive Spectrometry) analysis. Thermodynamic calculations, a phase analysis and construction of Kellogg diagrams for Ni-S-O and Fe-S-O systems at 298 K, 773 K, 923 K and 1073 K were used for proposing the theoretical reaction mechanism. A thermal analysis (TG/DTA—Thermogravimetric and Differential Thermal Analyses) was conducted in temperature range 298–1273 K, under a heating rate of 15° min−1. A kinetic analysis was conducted according to the non-isothermal method of Daniels and Borchardt, under a heating rate of 15° min−1. Calculated activation energies of 113 kJ mol−1, 146 kJ mol−1 and 356 kJ mol−1 for three oxidation stages imply that in every examined stage of the oxidation process, temperature is a dominant factor determining the reaction rate.
Effects of Sequential Operation with Heat Treatment and Mechanical Milling on Work Hardening for Superalloy GH4169
Authors: Zhu Pingzhong , Liu Zhanqiang , Ren Xiaoping , Wang Bing , Song Qinghua
Published: August 2021

Engineering components are usually manufactured with sequential production processes. Work hardening due to previous production processes affects the machinability of the workpiece in subsequent operations. In this research, the surface work hardening of a workpiece manufactured by two sequential processes with heat treatment/milling (HT + M) and milling/heat treatment (M + HT) of superalloy GH4169 was investigated. First, the surface microstructure characteristics, including plastic deformation and grain size of the machined workpiece surface processed by the two sequential processes, were quantitatively presented. Then, the microhardness on the machined workpiece surface and its cross-section was measured and analyzed. Finally, a surface microhardness calculation model considering twin boundary deformation was proposed. Here, we also present the microstructure evolution principle of the machined workpiece surface by the two sequential processes. It was found that the degree of work hardening of HT + M machining was 179%, whereas that of M + HT was only 101%. The research results can be applied to the optimized selection of process sequence for manufacturing superalloy GH4169.
Evaluation of Mass Transfer Coefficient during Scrap Melting
Authors: Gao Ming , Gao Jin-Tao , Zhang Yan-Ling
Published: August 2021

Mass transfer is a critical scrap melting step. Herein, mass transfer coefficients (k) during scrap melting were calculated using laboratory-scale experiments. Correlation analysis and the entropy weight method were used to determine the effect of variables on k. The evaluation model under natural and forced convection was established. It was consistent with the experimental results. Under forced convection, at 1573 and 1673 K, when the rotation speed was increased from 141 to 423 r/min, k increased from 7.50 × 10−5 to 1.54 × 10−4 m/s and from 8.42 × 10−5 to 1.72 × 10−4 m/s, respectively. Furthermore, as the bath temperature was increased from 1573 to 1723 K, the k value of a stationary specimen increased from 3.14 × 10−5 to 5.31 × 10−5 m/s, respectively. Correlation analysis and the entropy weight method indicated that the effects of variables on k decreased as follows: molten pool stirring rate > bath temperature > scrap type. Moreover, the explicit functional relationships between k and the factors affecting k under natural and forced convection conditions were established, and the results were consistent with the experimental data. Our results can be used to determine the quantitative relationships between k and the factors affecting k.