bluuebunny/crossref_metadata_2025 huggingface dataset:
Nontrivial Solutions of Systems of Perturbed Hammerstein Integral Equations with Functional Terms
Authors: Infante Gennaro
Published: February 2021

We discuss the solvability of a fairly general class of systems of perturbed Hammerstein integral equations with functional terms that depend on several parameters. The nonlinearities and the functionals are allowed to depend on the components of the system and their derivatives. The results are applicable to systems of nonlocal second order ordinary differential equations subject to functional boundary conditions, this is illustrated in an example. Our approach is based on the classical fixed point index.
Mutated Specification-Based Test Data Generation with a Genetic Algorithm
Authors: Wang Rong , Sato Yuji , Liu Shaoying
Published: February 2021

Specification-based testing methods generate test data without the knowledge of the structure of the program. However, the quality of these test data are not well ensured to detect bugs when non-functional changes are introduced to the program. To generate test data effectively, we propose a new method that combines formal specifications with the genetic algorithm (GA). In this method, formal specifications are reformed by GA in order to be used to generate input values that can kill as many mutants of the target program as possible. Two classic examples are presented to demonstrate how the method works. The result shows that the proposed method can help effectively generate test cases to kill the program mutants, which contributes to the further maintenance of software.
Factors Associated with Spa Tourists’ Satisfaction
Authors: Anaya-Aguilar Rosa , Gemar German , Anaya-Aguilar Carmen
Published: February 2021

Most spas are surrounded by beautiful natural environments, so these facilities contribute to sustainable economic development and their guests are national and local tourists with a high average stay. This study has the objective of analyzing the factors associated with the level of satisfaction and the profile of spa tourists in Andalusia, southern Spain. The methodology used was a quantitative study based on a stratified cross-sectional survey. Each stratum was a spa, with a population of 53,231 users per year, whose final sample included 725 users. The results found were that the profile of Andalusian spa tourists is predominantly female, over 56 years old, and retired with average incomes below one thousand euros. The level of satisfaction of its users is above the average in the factors of accommodation, restaurants, spa, and public roads and natural environment and most of these clients would recommend it to others [92.4%] and express the intention to return [63.6%] which indicates that Andalusian spas show a very high level of customer loyalty. The study has the limitation of being cross-sectional quantitative research carried out in Andalusia that could be complemented in future research with a qualitative study with experts. The research presents contributions for companies since they could develop strategies to attract users with younger profiles with activities, prices, or spaces that are more appropriate to their needs and seek the conditions to increase the satisfaction of these segments. The study is original since this research is a quantitative study that shows the real profile of the Andalusian spa tourist and their high level of satisfaction with the spa and their loyalty. The surveys were conducted at each spa by a face-to-face researcher with a response rate of 98%.
A Piecewise Polynomial Harmonic Nonlinear Interpolatory Reconstruction Operator on Non Uniform Grids—Adaptation around Jump Discontinuities and Elimination of Gibbs Phenomenon
Authors: Ortiz Pedro , Trillo Juan Carlos
Published: February 2021

In this paper, we analyze the behavior of a nonlinear reconstruction operator called PPH around discontinuities. The acronym PPH stands for Piecewise Polynomial Harmonic, since it uses piecewise polynomials defined by means of an adaption based on the use of the weighted Harmonic mean. This study is carried out in the general case of nonuniform grids, although for some results we restrict to σ quasi-uniform grids. In particular we analyze the numerical order of approximation close to jump discontinuities and the elimination of the Gibbs effects. We show, both theoretically and with numerical examples, that the numerical order is reduced but not completely lost as it is the case in their linear counterparts. Moreover we observe that the reconstruction is free of any Gibbs effects for sufficiently small grid sizes.
Double Roman Graphs in P(3k, k)
Authors: Shao Zehui , Erveš Rija , Jiang Huiqin , Peperko Aljoša , Wu Pu , Žerovnik Janez
Published: February 2021

A double Roman dominating function on a graph G=(V,E) is a function f:V→{0,1,2,3} with the properties that if f(u)=0, then vertex u is adjacent to at least one vertex assigned 3 or at least two vertices assigned 2, and if f(u)=1, then vertex u is adjacent to at least one vertex assigned 2 or 3. The weight of f equals w(f)=∑v∈Vf(v). The double Roman domination number γdR(G) of a graph G is the minimum weight of a double Roman dominating function of G. A graph is said to be double Roman if γdR(G)=3γ(G), where γ(G) is the domination number of G. We obtain the sharp lower bound of the double Roman domination number of generalized Petersen graphs P(3k,k), and we construct solutions providing the upper bounds, which gives exact values of the double Roman domination number for all generalized Petersen graphs P(3k,k). This implies that P(3k,k) is a double Roman graph if and only if either k≡0 (mod 3) or k∈{1,4}.
Covering Rational Surfaces with Rational Parametrization Images
Authors: Caravantes Jorge , Sendra J. Rafael , Sevilla David , Villarino Carlos
Published: February 2021

Let S be a rational projective surface given by means of a projective rational parametrization whose base locus satisfies a mild assumption. In this paper we present an algorithm that provides three rational maps f,g,h:A2⇢S⊂Pn such that the union of the three images covers S. As a consequence, we present a second algorithm that generates two rational maps f,g˜:A2⇢S, such that the union of its images covers the affine surface S∩An. In the affine case, the number of rational maps involved in the cover is in general optimal.
New Jochemsz–May Cryptanalytic Bound for RSA System Utilizing Common Modulus N = p2q
Authors: Adenan Nurul Nur Hanisah , Kamel Ariffin Muhammad Rezal , Sapar Siti Hasana , Abd Ghafar Amir Hamzah , Asbullah Muhammad Asyraf
Published: February 2021

This paper describes an attack on the Rivest, Shamir and Adleman (RSA) cryptosystem utilizing the modulus N=p2q where p and q are two large balanced primes. Let e1,e2<Nγ be the integers such that d1,d2<Nδ be their multiplicative inverses. Based on the two key equations e1d1−k1ϕ(N)=1 and e2d2−k2ϕ(N)=1 where ϕ(N)=p(p−1)(q−1), our attack works when the primes share a known amount of least significant bits (LSBs) and the private exponents share an amount of most significant bits (MSBs). We apply the extended strategy of Jochemsz–May to find the small roots of an integer polynomial and show that N can be factored if δ<1110+94α−12β−12γ−130180γ+990α−180β+64. Our attack improves the bounds of some previously proposed attacks that makes the RSA variant vulnerable.
Geometric Ergodicity of the Random Walk Metropolis with Position-Dependent Proposal Covariance
Authors: Livingstone Samuel
Published: February 2021

We consider a Metropolis–Hastings method with proposal N(x,hG(x)−1), where x is the current state, and study its ergodicity properties. We show that suitable choices of G(x) can change these ergodicity properties compared to the Random Walk Metropolis case N(x,hΣ), either for better or worse. We find that if the proposal variance is allowed to grow unboundedly in the tails of the distribution then geometric ergodicity can be established when the target distribution for the algorithm has tails that are heavier than exponential, in contrast to the Random Walk Metropolis case, but that the growth rate must be carefully controlled to prevent the rejection rate approaching unity. We also illustrate that a judicious choice of G(x) can result in a geometrically ergodic chain when probability concentrates on an ever narrower ridge in the tails, something that is again not true for the Random Walk Metropolis.
Inverse Problem of Recovering the Initial Condition for a Nonlinear Equation of the Reaction–Diffusion–Advection Type by Data Given on the Position of a Reaction Front with a Time Delay
Authors: Lukyanenko Dmitry , Yeleskina Tatyana , Prigorniy Igor , Isaev Temur , Borzunov Andrey , Shishlenin Maxim
Published: February 2021

In this paper, approaches to the numerical recovering of the initial condition in the inverse problem for a nonlinear singularly perturbed reaction–diffusion–advection equation are considered. The feature of the formulation of the inverse problem is the use of additional information about the value of the solution of the equation at the known position of a reaction front, measured experimentally with a delay relative to the initial moment of time. In this case, for the numerical solution of the inverse problem, the gradient method of minimizing the cost functional is applied. In the case when only the position of the reaction front is known, the method of deep machine learning is applied. Numerical experiments demonstrated the possibility of solving such kinds of considered inverse problems.
Comparative Investigation on Hydrodynamic Performance of Pump-Jet Propulsion Designed by Direct and Inverse Design Methods
Authors: Zhou Yunkai , Wang Longyan , Yuan Jianping , Luo Wei , Fu Yanxia , Chen Yang , Wang Zilu , Xu Jian , Lu Rong
Published: February 2021

Pump-jet propulsion, a new propulsion technology, is primarily designed for underwater vehicles. Because of its concealment and excellent performance, it has been widely used, but due to its confidentiality and complexity, few studies have been published. To explore the relevant design theory of pump-jet propulsion with the aim of increasing its performance, in this study, we applied the direct and inverse design methods to construct a three-dimensional pump-jet model. The direct design method was carried out by comparing the lifting and lifting-line design methods, followed by further geometric optimization of the better model. In a numerical study using computational fluid dynamics (CFD) simulations, the Reynolds Averaged Naviere-Stokes (RANS) equations with SST k-ω turbulence model were solved in a cylindrical computational domain around the pump-jet propulsion device. A numerical investigation of the E779A propeller was carried out beforehand, using different advance ratios, in order to validate the accuracy of the numerical simulation method. The results show that for the direct method, although the model designed using the lifting-line method produced a greater thrust and the pump-jet designed using the lifting method was more efficient and stable, which is more suitable for small and medium underwater vehicles. When considering the inverse design method, the pump-jet propeller obviously accelerated the fluid, and the speed was obviously greater than that designed using the direct design method, while the turbulent kinetic energy in the flow field was higher, as well as the energy loss. Therefore, for small- and medium-sized underwater vehicles, if the priorities are high thrust and high efficiency, the inverse design method is the best option, whereas if stability and lower energy loss are preferred, the direct design method should be adopted.
Optimal Rotor Design of Synchronous Reluctance Machines Considering the Effect of Current Angle
Authors: Rezk Hegazy , Tawfiq Kotb B. , Sergeant Peter , Ibrahim Mohamed N.
Published: February 2021

The torque density and efficiency of synchronous reluctance machines (SynRMs) are greatly affected by the geometry of the rotor. Hence, an optimal design of the SynRM rotor geometry is highly recommended to achieve optimal performance (i.e., torque density, efficiency, and power factor). This paper studies the impact of considering the current angle as a variable during the optimization process on the resulting optimal geometry of the SynRM rotor. Various cases are analyzed and compared for different ranges of current angles during the optimization process. The analysis is carried out using finite element magnetic simulation. The obtained optimal geometry is prototyped for validation purposes. It is observed that when considering the effect of the current angle during the optimization process, the output power of the optimal geometry is about 3.32% higher than that of a fixed current angle case. In addition, during the optimization process, the case which considers the current angle as a variable has reached the optimal rotor geometry faster than that of a fixed current angle case. Moreover, it is observed that for a fixed current angle case, the torque ripple is affected by the selected value of the current angle. The torque ripple is greatly decreased by about 34.20% with a current angle of 45° compared to a current angle of 56.50°, which was introduced in previous literature.
Some Important Criteria for Oscillation of Non-Linear Differential Equations with Middle Term
Authors: Althobati Saad , Bazighifan Omar , Yavuz Mehmet
Published: February 2021

In this work, we present new oscillation conditions for the oscillation of the higher-order differential equations with the middle term. We obtain some oscillation criteria by a comparison method with first-order equations. The obtained results extend and simplify known conditions in the literature. Furthermore, examining the validity of the proposed criteria is demonstrated via particular examples.
Lipid Inhibitory Effect of (−)-loliolide Isolated from Sargassum horneri in 3T3-L1 Adipocytes: Inhibitory Mechanism of Adipose-Specific Proteins
Authors: Lee Hyo-Geun , Kim Hyun-Soo , Je Jun-Geon , Hwang Jin , Sanjeewa K. K. Asanka , Lee Dae-Sung , Song Kyung-Mo , Choi Yun-Sang , Kang Min-Cheol , Jeon You-Jin
Published: February 2021

Sargassum horneri (S. horneri) is a well-known brown seaweed widely distributed worldwide. Several biological activities of S. horneri have been reported. However, its effects on lipid metabolism and the underlying mechanisms remain elusive. In the present study, we examined the inhibitory effect of the active compound “(−)-loliolide ((6S,7aR)-6-hydroxy-4,4,7a-trimethyl-5,6,7,7a-tetrahydro-1-benzofuran-2(4H)-one (HTT))” from S. horneri extract on lipid accumulation in differentiated adipocytes. MTT assays demonstrated that (−)-loliolide is not toxic to 3T3-L1 adipocytes in a range of concentrations. (−)-loliolide significantly reduced intracellular lipid accumulation in the differentiated phase of 3T3-L1 adipocytes as shown by Oil Red O staining. Western blot analysis revealed that (−)-loliolide increased the expression of lipolytic protein phospho-hormone-sensitive lipase (p-HSL) and thermogenic protein peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1). Additionally, (−)-loliolide decreased expression of adipogenic and lipogenic proteins, including sterol regulatory element-binding protein-1 (SREBP-1), peroxisome proliferator-activated receptor-γ (PPAR-γ), CCAAT/enhancer-binding protein-α (C/EBP-α), and fatty acid-binding protein 4 (FABP4) in 3T3-L1 adipocytes. These results indicate that (−)-loliolide from S. horneri could suppress lipid accumulation via regulation of antiadipogenic and prolipolytic mechanisms in 3T3-L1 cells. Considering the multifunctional effect of (−)-loliolide, it can be useful as a lipid-lowering agent in the management of patients who suffer from obesity.
SARS-CoV-2 Seroprevalence in Healthcare Workers of Kaunas Hospitals during the First Wave of the COVID-19 Pandemic
Authors: Pereckaitė Laura , Dambrauskienė Asta , Urbonienė Daiva , Sadauskas Saulius , Petrikonis Kęstutis , Naudžiūnas Albinas , Vitkauskienė Astra
Published: February 2021

Background and objective: Serologic testing is a useful additional method for the diagnosis of COVID-19. It is also used for population-based seroepidemiological studies. The objective of the study was to determine SARS-CoV-2 seroprevalence in healthcare workers of Kaunas hospitals and to compare two methods for specific SARS-CoV-2 antibody testing. Materials and Methods: A total of 432 healthcare workers in Kaunas hospitals were enrolled in this study. Each participant filled a questionnaire including questions about their demographics, contact with suspected or confirmed COVID-19, acute respiratory symptoms, and whether they contacted their general practitioner, could not come to work, or had to be hospitalized. Capillary blood was used to test for SARS-CoV-2 specific immunoglobulin G (IgG) and immunoglobulin M (IgM) a lateral flow immunoassay. Serum samples were used to test for specific IgG and IgA class immunoglobulins using semiquantitative enzyme-linked immunosorbent assay (ELISA) method. Results: 24.77% of study participants had direct contact with a suspected or confirmed case of COVID-19. A total of 64.81% of studied individuals had at least one symptom representing acute respiratory infection, compatible with COVID-19. Lateral flow immunoassay detected SARS-CoV-2 specific IgG class immunoglobulins in 1.16% of the tested group. Fever, cough, dyspnea, nausea, diarrhea, headache, conjunctivitis, muscle pain, and loss of smell and taste predominated in the anti-SARS-CoV-2 IgG-positive group. Using ELISA, specific IgG were detected in 1.32% of the tested samples. Diarrhea, loss of appetite, and loss of smell and taste sensations were the most predominant symptoms in anti-SARS-CoV-2 IgG-positive group. The positive percent agreement of the two testing methods was 50%, and negative percent agreement was 99.66%. Conclusions: 1.16% of tested healthcare workers of Kaunas hospitals were anti-SARS-CoV-2 IgG-positive. The negative percent agreement of the lateral flow immunoassay and ELISA exceeded 99%.
Twelve-Weeks of Bench-Step Exercise Training Ameliorates Cardiopulmonary Fitness and Mood State in Patients with Schizophrenia: A Pilot Study
Authors: Kuo Yu-Chi , Chang Dan-Yan , Liao Yi-Hung
Published: February 2021

Background and objectives: Unhealthy, physically inactive lifestyles increase the risk of future cardiovascular events and impaired physical fitness in individuals with schizophrenia. Insufficient literature exists to provide fundamental information about appropriate exercise training modality for this population. This pilot study preliminarily investigated the effects of a 12-week moderate-intensity bench-step exercise training (BSET) program on cardiopulmonary fitness, mood state, and cognition in patients with schizophrenia. Methods: Twenty-eight patients with schizophrenia completed this study. The participants were allocated into either bench-step exercise-training (BSET; N = 14) or control (CTRL; N = 14) groups according to their preferences. The BSET group received a 12-week bench-step intervention, whereas the CTRL group did not participate in any training. The Beck Depression Inventory-II (BDI-II), 6-min walk test (6MWD), and Symbol Digit Modalities Test (SDMT) were assessed at baseline (PRE) and at the end of the intervention (POST) to determine mood state, endurance fitness, and attention, respectively. Results: After a 12-week BSET intervention, the 6MWD was significantly increased in the BSET (p = 0.007) but not in the CTRL (p > 0.05). The participants with BSET intervention showed a significant decrease in BDI-II at the end of the intervention (p = 0.03). However, SDMT scores were not different in both BSET and CTRL (p > 0.05). Conclusions: This study demonstrated that the 12-week intervention of moderate-intensity bench-step exercise training (frequency: 1 session/week; each session of 30 min; step cadence: 96 beats/min) might effectively enhance cardiopulmonary fitness and mood state in patients with schizophrenia. However, attention did not change after the bench-step exercise intervention.
Microendoscope-Assisted Versus Open Posterior Lumbar Interbody Fusion for Lumbar Degenerative Disease: A Multicenter Retrospective Cohort Study
Authors: Fukushima Masayoshi , Ohtomo Nozomu , Noma Michita , Kumanomido Yudai , Nakarai Hiroyuki , Tozawa Keiichiro , Yoshida Yuichi , Sakamoto Ryuji , Miyahara Junya , Anno Masato , Kawamura Naohiro , Higashikawa Akiro , Takeshita Yujiro , Inanami Hirohiko , Tanaka Sakae , Oshima Yasushi
Published: February 2021

Background and objectives: Minimally invasive surgery has become popular for posterior lumbar interbody fusion (PLIF). Microendoscope-assisted PLIF (ME-PLIF) utilizes a microendoscope within a tubular retractor for PLIF procedures; however, there are no published reports that compare Microendoscope-assisted to open PLIF. Here we compare the surgical and clinical outcomes of ME-PLIF with those of open PLIF. Materials and Methods: A total of 155 consecutive patients who underwent single-level PLIF were registered prospectively. Of the 149 patients with a complete set of preoperative data, 72 patients underwent ME-PLIF (ME-group), and 77 underwent open PLIF (open-group). Clinical and radiographic findings collected one year after surgery were compared. Results: Of the 149 patients, 57 patients in ME-group and 58 patients in the open-group were available. The ME-PLIF procedure required a significantly shorter operating time and involved less intraoperative blood loss. Three patients in both groups reported dural tears as intraoperative complications. Three patients in ME-group experienced postoperative complications, compared to two patients in the open-group. The fusion rate in ME-group at one year was lower than that in the open group (p = 0.06). The proportion of patients who were satisfied was significantly higher in the ME-group (p = 0.02). Conclusions: ME-PLIF was associated with equivalent post-surgical outcomes and significantly higher rates of patient satisfaction than the traditional open PLIF procedure. However, the fusion rate after ME-PLIF tended to be lower than that after the traditional open method.
Oral Solitary Fibrous Tumor: A Retrospective Clinico-Pathological Study and Long-Term Follow-Up
Authors: Shmuly Tom , Ben Zvi Yehonatan , Chaushu Gabriel , Kaplan Ilana
Published: February 2021

Background and Objectives: This was a retrospective single-center study to analyze and describe the clinical and histological features of all cases of oral solitary fibrous tumor (SFT). Study design: the study included all consecutive cases of oral SFT diagnosed between 2008–2018 at a single tertiary center. Materials and Methods: Clinical data was retrieved from medical charts. The diagnosis of oral SFT was based upon the morphologic features of the lesions, in routine hematoxylin and eosin (H&E) stained sections and confirmed by immunohistochemical analyses including CD34, CD99, Bcl2, and stains for STAT6. Results: Seven cases of oral SFT were found. Of these, three (42%) were in males and four (58%) in females. The age range was 24–63 years (mean 47 ± 13). Four (58%) lesions were located in the buccal mucosa, two (28%) in the labial mucosa and one (14%) on the floor of the mouth. The diameter ranged between 3–50 mm (mean 22 ± 14 mm). All patients were treated with local excision. Follow-up periods were between 2–74 months (mean 41 ± 27). No recurrences were reported. Conclusions: We present a series of oral SFT, which were all non-aggressive in presentation and did not recur after conservative surgery (local excision) over a relatively long follow-up period.
Estimation of the Number of General Anesthesia Cases Based on a Series of Nationwide Surveys on Twitter during COVID-19 Pandemic in Japan: A Statistical Analysis
Authors: Fujii Yosuke , Daijo Hiroki , Hirota Kiichi
Published: February 2021

Background and objectives: Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has spread to more than 200 countries. In light of this situation, the Japanese Government declared a state of emergency in seven regions of Japan on 7 April 2020 under the provisions of the law. The medical care delivery system has been under pressure. Although various surgical societies have published guidelines on which to base their surgical decisions, it is not clear how general anesthesia has been performed and will be performed in Japan. Materials and Methods: One of the services provided by the social network service Twitter is a voting function—Twitter Polls—through which anonymous surveys were conducted. We analyzed the results of a series of surveys 17 times over 22 weeks on Twitter on the status of operating restrictions using quadratic programming to solve the mathematical optimizing problem, and public data provided by the Japanese Government were used to estimate the current changes in the number of general anesthesia performed in Japan. Results: The minimum number of general anesthesia cases per week was estimated at 67.1% compared to 2015 on 27 April 2020. The timeseries trend was compatible with the results reported by the Japanese Society of Anesthesiologists (correlation coefficient r = 0.69, p < 0.001). Conclusions: The number of general anesthesia was reduced up to two-thirds during the pandemic of COVID-19 in Japan and was successfully quantitatively estimated using a quick questionnaire on Twitter.
Clinical Impact of Psychopathy on Bipolar Disorder
Authors: Calabrò Giuseppina , Musolino Antonio Francesco , Filippo Andrea Adolfo , de Filippis Renato , Carbone Elvira Anna , Rania Marianna , Aloi Matteo , Pugliese Valentina , Segura-Garcia Cristina
Published: February 2021

Background and Objectives. Bipolar disorder (BD) is associated with a significant burden due to affective symptoms and behavioral manifestations, but also cognitive and functional impairment. Comorbidity with other psychiatric conditions, including personality disorders, is frequent. The comorbidity with psychopathy deserves special consideration given that both disorders share some clinical characteristics, such as grandiosity, risky behavior or poor insight, among others, that can worsen the outcome of BD. Therefore, this study aimed to evaluate the prevalence of psychopathy in a sample of clinically stabilized patients with BD and its impact on the severity of BD. Materials and Methods. A sample of 111 patients with BD (38 type I and 73 type II) was studied. The Hamilton Depression Rating Scale (HAM-D) and the Young Mania Rating Scale (YMRS) served to assess the severity of BD. Psychopathy was measured by means of the Psychopathic Personality Inventory-Revised (PPI-R). Patients were divided into three groups according to the severity of psychopathy (Group 1: no psychopathy; Group 2: “psychopathic” trait; Group 3: clinical psychopathy). Other measures regarded impulsiveness (Barratt Impulsiveness Scale-11, BIS-11) and empathy (Empathy Quotient, EQ). Comparisons of mania, depression, impulsivity and empathy scores were run with MANOVA considering psychopathy and diagnosis as independent variables. Results. The prevalence of psychopathy was 5.4%. A significant association between the level of psychopathy and YMRS, attentional/cognitive impulsivity and motor impulsivity scores emerged. No interaction between psychopathy and BD diagnosis was found. Post hoc analysis demonstrated significantly higher YMRS scores in Group 3 than in Group 1; that is, patients with psychopathy have more manic symptoms. Conclusion. Psychopathy seems quite frequent among patients with BD. The association of psychopathy with BD results in higher impulsivity and manic symptoms. In light of this, psychopathy should be investigated when assessing patients with BD, regardless of the comorbidity of BD with other personality disorders.
The Laser Alloying Process of Ductile Cast Iron Surface with Titanium
Authors: Kotarska Aleksandra
Published: February 2021

The article presents the results of the laser alloying process of ductile cast iron EN-GJS 350-22 surface with titanium. The laser alloying process was conducted on 2 kW high power diode laser (HPDDL) Rofin Sinar DL02 with rectangular focus and uniform power density distribution in the focus axis. The laser alloying was conducted with constant laser beam power and processing speed with titanium powder feed rate variation. The tests of the produced surface layers included macrostructure and microstructure observations, X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) analysis, Vickers hardness, and solid particle erosion according to ASTM G76-04 standard. To assess the erosion mechanism, SEM observations of worn surfaces after erosive test were carried out. As a result of laser alloying of a ductile cast iron surface, the in situ metal-matrix composite structure was formed with TiC reinforcing particles. The microstructure change resulted in the increase of surface layers hardness and erosion resistance in comparison to the base material.
Corrosion Mechanisms of High-Mn Twinning-Induced Plasticity (TWIP) Steels: A Critical Review
Authors: Bastidas David M. , Ress Jacob , Bosch Juan , Martin Ulises
Published: February 2021

Twinning-induced plasticity (TWIP) steels have higher strength and ductility than conventional steels. Deformation mechanisms producing twins that prevent gliding and stacking of dislocations cause a higher ductility than that of steel grades with the same strength. TWIP steels are considered to be within the new generation of advanced high-strength steels (AHSS). However, some aspects, such as the corrosion resistance and performance in service of TWIP steel materials, need more research. Application of TWIP steels in the automotive industry requires a proper investigation of corrosion behavior and corrosion mechanisms, which would indicate the optimum degree of protection and the possible decrease in costs. In general, Fe−Mn-based TWIP steel alloys can passivate in oxidizing acid, neutral, and basic solutions, however they cannot passivate in reducing acid or active chloride solutions. TWIP steels have become as a potential material of interest for automotive applications due to their effectiveness, impact resistance, and negligible harm to the environment. The mechanical and corrosion performance of TWIP steels is subjected to the manufacturing and processing steps, like forging and casting, elemental composition, and thermo-mechanical treatment. Corrosion of TWIP steels caused by both intrinsic and extrinsic factors has posed a serious problem for their use. Passivity breakdown caused by pitting, and galvanic corrosion due to phase segregation are widely described and their critical mechanisms examined. Numerous studies have been performed to study corrosion behavior and passivation of TWIP steel. Despite the large number of articles on corrosion, few comprehensive reports have been published on this topic. The current trend for development of corrosion resistance TWIP steel is thoroughly studied and represented, showing the key mechanisms and factors influencing corrosion processes, and its consequences on TWIP steel. In addition, suggestions for future works and gaps in the literature are considered.
Hot Compression Behavior of New Al-6Mg and Al-8Mg Alloy with Improved Hot Workability Fabricated by Direct Chill Casting Method
Authors: Kim Nam-Seok , Choi Kweon-Hoon , Yang Seung-Yoon , Ha Seong-Ho , Yoon Young-Ok , Kim Bong-Hwan , Lim Hyun-Kyu , Kim Shae K. , Hyun Soong-Keun
Published: February 2021

A hot compression test of new Al-6Mg and Al-8Mg alloys was conducted to understand the dynamic recrystallization (DRX) behavior by Mg contents. To investigate the hot workability of Al-Mg with high Mg contents, the hot deformation behavior of Al-6Mg and Al-8Mg alloys was analyzed by a hot compression test in the temperature range of 300–450 °C, and the strain rate range of 10−3–100/s. Subsequently, high-temperature deformation behavior was investigated through the processing map and microstructure observation. In this study, the results have shown that, as the Mg contents increase, the maximum and yield strength increase while rapid flow softening after the peak strain has been observed due to accelerated dynamic recrystallization (DRX). Finally, the increase of Mg contents affects an increase of heat dissipation efficiency to be an indicator of regular deformation.
Effect of FeO Content on Foaming and Viscosity Properties in FeO-CaO-SiO2-MgO-Al2O3 Slag System
Authors: Chang Wei-Ti , Lin Chi-Ming , Su Yu-Lang , Li Chia-Chun , Chang Yu-En , Shen Jyun-Ming , Wu Weite
Published: February 2021

The foaming process is an important part of the electric arc furnace (EAF) steelmaking process. It can promote thermal efficiency and reduce refractory consumption. FeO is a key material used during the foaming process. Unlike with other components used in forming foaming slag, the amount of FeO can be controlled by oxygen or carbon injection. Therefore, adjusting the content of FeO is the most economical foaming mode adopted for the EAFs steelmaking process. In this study, the influence of FeO content on the physical properties of slag was discussed. The melting temperature of the slag was evaluated using three methods: viscosity experiment, using Thermo-Calc simulation software, and high-temperature optical method. The experimental results revealed that the viscosity of slag increases as FeO content decreases. The results also revealed that foam height ratio exhibited a positive correlation with the viscosity of slag.
Deep Learning-Based Ultrasonic Testing to Evaluate the Porosity of Additively Manufactured Parts with Rough Surfaces
Authors: Park Seong-Hyun , Hong Jung-Yean , Ha Taeho , Choi Sungho , Jhang Kyung-Young
Published: February 2021

Ultrasonic testing (UT) has been actively studied to evaluate the porosity of additively manufactured parts. Currently, ultrasonic measurements of as-deposited parts with a rough surface remain problematic because the surface lowers the signal-to-noise ratio (SNR) of ultrasonic signals, which degrades the UT performance. In this study, various deep learning (DL) techniques that can effectively extract the features of defects, even from signals with a low SNR, were applied to UT, and their performance in terms of the porosity evaluation of additively manufactured parts with rough surfaces was investigated. Experimentally, the effects of the processing conditions of additive manufacturing on the resulting porosity were first analyzed using both optical and scanning acoustic microscopy. Second, convolutional neural network (CNN), deep neural network, and multi-layer perceptron models were trained using time-domain ultrasonic signals obtained from additively manufactured specimens with various levels of porosity and surface roughness. The experimental results showed that all the models could evaluate porosity accurately, even that of the as-deposited specimens. In particular, the CNN delivered the best performance at 94.5%. However, conventional UT could not be applied because of the low SNR. The generalization performance when using newly manufactured as-deposited specimens was high at 90%.
Challenges in Ecofriendly Battery Recycling and Closed Material Cycles: A Perspective on Future Lithium Battery Generations
Authors: Doose Stefan , Mayer Julian K. , Michalowski Peter , Kwade Arno
Published: February 2021

The global use of lithium-ion batteries of all types has been increasing at a rapid pace for many years. In order to achieve the goal of an economical and sustainable battery industry, the recycling and recirculation of materials is a central element on this path. As the achievement of high 95% recovery rates demanded by the European Union for some metals from today’s lithium ion batteries is already very challenging, the question arises of how the process chains and safety of battery recycling as well as the achievement of closed material cycles are affected by the new lithium battery generations, which are supposed to enter the market in the next 5 to 10 years. Based on a survey of the potential development of battery technology in the next years, where a diversification between high-performance and cost-efficient batteries is expected, and today’s knowledge on recycling, the challenges and chances of the new battery generations regarding the development of recycling processes, hazards in battery dismantling and recycling, as well as establishing a circular economy are discussed. It becomes clear that the diversification and new developments demand a proper separation of battery types before recycling, for example by a transnational network of dismantling and sorting locations, and flexible and high sophisticated recycling processes with case-wise higher safety standards than today. Moreover, for the low-cost batteries, recycling of the batteries becomes economically unattractive, so legal stipulations become important. However, in general, it must be still secured that closing the material cycle for all battery types with suitable processes is achieved to secure the supply of raw materials and also to further advance new developments.
Statistical Soil Characterization of an Underground Corroded Pipeline Using In-Line Inspections
Authors: Amaya-Gómez Rafael , Bastidas-Arteaga Emilio , Muñoz Felipe , Sánchez-Silva Mauricio
Published: February 2021

Underground pipelines have a space-dependent condition that arises from various soil properties surrounding the pipeline (e.g., moisture content, pH, aeration) and the efficiency of protection measures. Corrosion is one of the main threats for pipelines and is commonly monitored with in-line inspections (ILI) every 2 to 6 years. Preliminary characterizations of the surrounding soil allow pipeline operators to propose adequate protective measures to prevent any loss of containment (LOC) of the fluid being transported. This characterization usually requires detailed soil measurements, which could be unavailable or very costly. This paper implements categorical measurements of soil properties and defect depth measurements obtained from ILI to characterize the soil in the surroundings of a pipeline. This approach implements an independence test, a multiple correspondence analysis, and a clustering method with K-modes. The approach was applied to a real case study, showing that more severe defects are likely located in poorly drained soils with high acidity.
Bioleaching of Pyrrhotite with Bacterial Adaptation and Biological Oxidation for Iron Recovery
Authors: Kim Bong-Ju , Koh Yong-Kwon , Kwon Jang-Soon
Published: February 2021

The microbially mediated recovery of valuable metals contained in mining waste presents an economical alternative to conventional hydrometallurgical processes. In order to investigate the effect of bacterial adaptation and biological oxidation on bioleaching, the microbially mediated bioleaching of a pyrrhotite sample from mine waste, with indigenous bacteria existing in acid mine drainage, was studied. The indigenous bacteria were sub-cultured repeatedly for iron adaptation, and Acidithiobacillus ferrooxidans was identified as the dominant member of the microbial consortium. The point of zero charge (PZC) of pyrrhotite sampled from mine waste was determined as 3.0. The performance of bioleaching by contact and non-contact biological oxidation was compared by conducting bioleaching under different initial pH (pHini) conditions (2.8 and 3.2). Negatively charged bacteria could be attached onto the pyrrhotite, which has a positive surface charge at lower pHini (2.8) than the PZC (3.0). Bacteria attachment and corrosion pits on the surface of the pyrrhotite residues were observed at pHini of 2.8. Under bacteria-adapted conditions, the leaching concentration of Fe (44.2 mg/L) at pHini of 2.8 was 2.1 times greater than that (21.3 mg/L) at pHini of 3.2. Under non-adapted bacteria conditions, the extent of Fe leaching was not significantly different between the pHini of 2.8 and 3.2. This could be attributed to the fact that the adapted bacteria could more easily attach onto the pyrrhotite surfaces at pHini 2.8, allowing contact biological oxidation during the bioleaching experiments. We demonstrate here that the bioleaching of pyrrhotite could increase Fe recovery through bacterial adaptation and contact biological oxidation.
Effect of Severe Plastic Deformation on Structure Refinement and Mechanical Properties of the Al-Zn-Mg-Fe-Ni Alloy
Authors: Brodova Irina , Rasposienko Dmitriy , Shirinkina Irina , Petrova Anastasia , Akopyan Torgom , Bobruk Elena
Published: February 2021

This paper identifies the mechanisms of phase and structural transformations during severe plastic deformation by shearing under pressure (high-pressure torsion) of an Al-Zn-Mg-Fe-Ni-based aluminum alloy depending on different initial states of the material (an ingot after homogenizing annealing and a rod produced by radial-shear rolling). Scanning and transmission electron microscopy are used to determine the morphological and size characteristics of the structural constituents of the alloy after high-pressure torsion. It has been found that, irrespective of the history under high-pressure torsion, fragmentation and dynamic recrystallization results in a nanostructural alloy with a high microhardness of 2000 to 2600 MPa. Combined deformation processing (high-pressure torsion + radial-shear rolling) is shown to yield a nanocomposite reinforced with dispersed intermetallic phases of different origins, namely Al9FeNi eutectic aluminides and MgZn2, Al2Mg3Zn3, and Al3Zr secondary phases. The results of uniaxial tensile testing demonstrate good mechanical properties of the composite (ultimate tensile strength of 640 MPa, tensile yield strength of 628 MPa, and elongation of 5%).
Solvent Extraction of Iron(III) from Al Chloride Solution of Bauxite HCl Leaching by Mixture of Aliphatic Alcohol and Ketone
Authors: Sokolov Artem , Valeev Dmitry , Kasikov Aleksandr
Published: February 2021

Research into the solvent extraction of iron(III) from a chloride solution after bauxite HCl leaching by neutral oxygen-containing extractants and their mixtures were studied and the iron(III) extraction degree from chloride solutions using alcohols is presented. The effect of dilution of alcohol with a ketone by an extraction mixture in relation to its effectiveness was investigated. The iron(III) was efficiently extracted by the mixture of 1-octanol and 1-decanol (70%) with 2-undecanone (30%) from hydrochloric bauxite leach liquor at an O:A ratio = 2-4:1 at an iron(III) concentration of 7.4 g/L and 6 M HCl. For the removal of iron-containing organic phase from impurities (Al, Ca, Cr) that are co-extracted with iron(III), we used two step scrubbing at O:A = 5:1 by 7 M HCl as a scrub solution. The iron(III) stripping at the O:A ratio is shown. Using counter-current cascade of extractors, it was possible to obtain an FeCl3 solution with the iron(III) content of 90.5 g/L and total impurities less than 50 mg/L.
Modeling of Endothelial Calcium Responses within a Microfluidic Generator of Spatio-Temporal ATP and Shear Stress Signals
Authors: Li Yong-Jiang , Yu Miao , Xue Chun-Dong , Zhang Hai-Jun , Wang Guo-Zhen , Chen Xiao-Ming , Qin Kai-Rong
Published: February 2021

Intracellular calcium dynamics play essential roles in the proper functioning of cellular activities. It is a well known important chemosensing and mechanosensing process regulated by the spatio-temporal microenvironment. Nevertheless, how spatio-temporal biochemical and biomechanical stimuli affect calcium dynamics is not fully understood and the underlying regulation mechanism remains missing. Herein, based on a developed microfluidic generator of biochemical and biomechanical signals, we theoretically analyzed the generation of spatio-temporal ATP and shear stress signals within the microfluidic platform and investigated the effect of spatial combination of ATP and shear stress stimuli on the intracellular calcium dynamics. The simulation results demonstrate the capacity and flexibility of the microfluidic system in generating spatio-temporal ATP and shear stress. Along the transverse direction of the microchannel, dynamic ATP signals of distinct amplitudes coupled with identical shear stress are created, which induce the spatio-temporal diversity in calcium responses. Interestingly, to the multiple combinations of stimuli, the intracellular calcium dynamics reveal two main modes: unimodal and oscillatory modes, showing significant dependence on the features of the spatio-temporal ATP and shear stress stimuli. The present study provides essential information for controlling calcium dynamics by regulating spatio-temporal biochemical and biomechanical stimuli, which shows the potential in directing cellular activities and understanding the occurrence and development of disease.
Design of Driving Waveform Based on a Damping Oscillation for Optimizing Red Saturation in Three-Color Electrophoretic Displays
Authors: Yi Zichuan , Zeng Weibo , Ma Simin , Feng Haoqiang , Zeng Wenjun , Shen Shitao , Shui Lingling , Zhou Guofu , Zhang Chongfu
Published: February 2021

At present, three-color electrophoretic displays (EPDs) have problems of dim brightness and insufficient color saturation. In this paper, a driving waveform based on a damping oscillation was proposed to optimize the red saturation in three-color EPDs. The optimized driving waveform was composed of an erasing stage, a particles activation stage, a red electrophoretic particles purification stage, and a red display stage. The driving duration was set to 360 ms, 880 ms, 400 ms, and 2400 ms, respectively. The erasing stage was used to erase the current pixel state and refresh to a black state. The particles’ activation stage was set as two cycles, and then refreshed to the black state. The red electrophoretic particles’ purification stage was a damping oscillation driving waveform. The red and black electrophoretic particles were separated by changing the magnitude and polarity of applied electric filed, so that the red electrophoretic particles were purified. The red display stage was a low positive voltage, and red electrophoretic particles were driven to the common electrode to display a red state. The experimental results showed that the maximum red saturation could reach 0.583, which was increased by 27.57% compared with the traditional driving waveform.
Streptococcus suis Induces Expression of Cyclooxygenase-2 in Porcine Lung Tissue
Authors: Dresen Muriel , Schenk Josephine , Berhanu Weldearegay Yenehiwot , Vötsch Désirée , Baumgärtner Wolfgang , Valentin-Weigand Peter , Nerlich Andreas
Published: February 2021

Streptococcus suis is a common pathogen colonising the respiratory tract of pigs. It can cause meningitis, sepsis and pneumonia leading to economic losses in the pig industry worldwide. Cyclooxygenase-2 (COX-2) and its metabolites play an important regulatory role in different biological processes like inflammation modulation and immune activation. In this report we analysed the induction of COX-2 and the production of its metabolite prostaglandin E2 (PGE2) in a porcine precision-cut lung slice (PCLS) model. Using Western blot analysis, we found a time-dependent induction of COX-2 in the infected tissue resulting in increased PGE2 levels. Immunohistological analysis revealed a strong COX-2 expression in the proximity of the bronchioles between the ciliated epithelial cells and the adjacent alveolar tissue. The morphology, location and vimentin staining suggested that these cells are subepithelial bronchial fibroblasts. Furthermore, we showed that COX-2 expression as well as PGE2 production was detected following infection with two prevalent S. suis serotypes and that the pore-forming toxin suilysin played an important role in this process. Therefore, this study provides new insights in the response of porcine lung cells to S. suis infections and serves as a basis for further studies to define the role of COX-2 and its metabolites in the inflammatory response in porcine lung tissue during infections with S. suis.