bluuebunny/crossref_metadata_2025 huggingface dataset:
Global Stability Analysis of a Five-Dimensional Unemployment Model with Distributed Delay
Authors: Kaslik Eva , Neamţu Mihaela , Vesa Loredana Flavia
Published: November 2021

The present paper proposes a five-dimensional mathematical model for studying the labor market, focusing on unemployment, migration, fixed term contractors, full time employment and the number of available vacancies. The distributed time delay is considered in the rate of change of available vacancies that depends on the past regular employment levels. The non-dimensional mathematical model is introduced and the existence of the equilibrium points is analyzed. The positivity and boundedness of solutions are provided and global asymptotic stability findings are presented both for the employment free equilibrium and the positive equilibrium. The numerical simulations support the theoretical results.
{0,1}-Brauer Configuration Algebras and Their Applications in Graph Energy Theory
Authors: Agudelo Muñetón Natalia , Cañadas Agustín Moreno , Espinosa Pedro Fernando Fernández , Gaviria Isaías David Marín
Published: November 2021

The energy E(G) of a graph G is the sum of the absolute values of its adjacency matrix. In contrast, the trace norm of a digraph Q, which is the sum of the singular values of the corresponding adjacency matrix, is the oriented version of the energy of a graph. It is worth pointing out that one of the main problems in this theory consists of determining appropriated bounds of these types of energies for significant classes of graphs, digraphs and matrices, provided that, in general, finding out their exact values is a problem of great difficulty. In this paper, the trace norm of a {0,1}-Brauer configuration is introduced. It is estimated and computed by associating suitable families of graphs and posets to Brauer configuration algebras.
Representation and Reasoning about Strategic Abilities with ω-Regular Properties
Authors: Xiong Liping , Guo Sumei
Published: November 2021

Specification and verification of coalitional strategic abilities have been an active research area in multi-agent systems, artificial intelligence, and game theory. Recently, many strategic logics, e.g., Strategy Logic (SL) and alternating-time temporal logic (ATL*), have been proposed based on classical temporal logics, e.g., linear-time temporal logic (LTL) and computational tree logic (CTL*), respectively. However, these logics cannot express general ω-regular properties, the need for which are considered compelling from practical applications, especially in industry. To remedy this problem, in this paper, based on linear dynamic logic (LDL), proposed by Moshe Y. Vardi, we propose LDL-based Strategy Logic (LDL-SL). Interpreted on concurrent game structures, LDL-SL extends SL, which contains existential/universal quantification operators about regular expressions. Here we adopt a branching-time version. This logic can express general ω-regular properties and describe more programmed constraints about individual/group strategies. Then we study three types of fragments (i.e., one-goal, ATL-like, star-free) of LDL-SL. Furthermore, we show that prevalent strategic logics based on LTL/CTL*, such as SL/ATL*, are exactly equivalent with those corresponding star-free strategic logics, where only star-free regular expressions are considered. Moreover, results show that reasoning complexity about the model-checking problems for these new logics, including one-goal and ATL-like fragments, is not harder than those of corresponding SL or ATL*.
Innovative Mesosystems Algorithm for Sustainable Development Priority Areas Identification in Industry Based on Decision Trees Construction
Authors: Shinkevich Aleksey I. , Ershova Irina G. , Galimulina Farida F. , Yarlychenko Alla A.
Published: November 2021

Globally, assessing sustainable development methodology is kept in sustainable society index (SSI) format, but at the level of meso- and microsystems it remains undeveloped. The aim of the study is to typologize innovative mesosystems in Russian industry in the context of sustainable development based on the CART algorithm and to develop an algorithm for identifying priority areas of sustainable development. The research methods applied included formalization, a systematic approach, and the CART algorithm (calculation of the Gini index, training sample segmentation, the use of a recursive function and regression assessment). As a result of the study, the algorithm for the differentiated identification of innovative mesosystems sustainable development priority directions in industry based on the unique author’s methodology (ISDI) is proposed. The predominance of mesosystems with weak level of sustainable development requiring state support in favor of such mesosystems restructure is revealed. The novelty of the research lies in the development of new science-based solutions to ensure an accelerated transition of industry to the path of sustainable development. The difference of the author’s approach from the provisions known in science is the inclusion of environmental innovations in the mechanism for managing the sustainable development of innovative mesosystems and subsequent accounting in the process of mathematical processing of an array of data, which determines the uniqueness of the constructed decision trees.
Efficient Covering of Thin Convex Domains Using Congruent Discs
Authors: Gul Shai , Cohen Reuven
Published: November 2021

We present efficient strategies for covering classes of thin domains in the plane using unit discs. We start with efficient covering of narrow domains using a single row of covering discs. We then move to efficient covering of general rectangles by discs centered at the lattice points of an irregular hexagonal lattice. This optimization uses a lattice that leads to a covering using a small number of discs. We compare the bounds on the covering using the presented strategies to the bounds obtained from the standard honeycomb covering, which is asymptotically optimal for fat domains, and show the improvement for thin domains.
Plenty of Fish in the Sea: Divorce Choice and the Quality of Singles
Authors: Gronchi Giorgio , Parilina Elena , Tampieri Alessandro
Published: November 2021

In the literature of marriage, divorce choices are usually assumed to not affect the distribution of types in the pool of singles. The scope of the present paper is to overcome this assumption. We analyse divorce choices when separation decision influences the distribution of singles and, thus, their expected quality. We consider a three-period model where heterogeneous individuals may unilaterally experience divorce and return to the marriage market. The choices of individuals are based on the change in the distribution of singles and the cost of waiting and divorcing, taking into consideration the individual’s eligibility in the marriage market. There are two main findings: Firstly, positive assortative matching dissolves with divorce for some intermediate types. Therefore, the endogenous positive assortative matching that usually emerges in models with nontransferable utility is weakened when matches can dissolve. Secondly, the existence of ranges where divorce emerges among individuals with positive assortative matching implies the existence of two disconnected classes of types. If matchings in the first period were to occur between individuals of different classes, such matches would be dissolved later.
Systematic Review of the Development of Spatial Intelligence through Augmented Reality in STEM Knowledge Areas
Authors: del Cerro Velázquez Francisco , Morales Méndez Ginés
Published: November 2021

This study presents a systematic review (SR) of the literature on the use of Augmented Reality (AR) for the development of spatial skills of secondary and higher education students in the teaching of subjects related to the area of Science, Technology, Engineering and Mathematics (STEM). Numerous researchers have confirmed that students tend to have difficulties in acquiring learning content with a high visual load, which is why AR is being used to improve teaching–learning processes. This paper aims to present information of interest to researchers, teachers and software developers about the advantages and limitations of AR in the development of spatial intelligence, the integration and development of AR applications, as well as the predominant spatial skills and assessment methods. In this regard, an initial search was carried out which returned 242 articles. After reviewing and assessing their eligibility, a total of 17 papers published since 2002 were selected. The findings reveal an increase in the number of investigations over the last few years. Some of the most notable findings are the improvement of spatial skills of students through the inclusion of AR in educational environments, the need for teacher training, the lack of personalization in the applications developed and the scarcity of augmented materials in the form of Open Educational Resources (OER).
An Ideal-Based Dot Total Graph of a Commutative Ring
Authors: Ashraf Mohammad , Asalool Jaber H. , Alanazi Abdulaziz M. , Alamer Ahmed
Published: November 2021

In this paper, we introduce and investigate an ideal-based dot total graph of commutative ring R with nonzero unity. We show that this graph is connected and has a small diameter of at most two. Furthermore, its vertex set is divided into three disjoint subsets of R. After that, connectivity, clique number, and girth have also been studied. Finally, we determine the cases when it is Eulerian, Hamiltonian, and contains a Eulerian trail.
Categorical Functional Data Analysis. The cfda R Package
Authors: Preda Cristian , Grimonprez Quentin , Vandewalle Vincent
Published: November 2021

Categorical functional data represented by paths of a stochastic jump process with continuous time and a finite set of states are considered. As an extension of the multiple correspondence analysis to an infinite set of variables, optimal encodings of states over time are approximated using an arbitrary finite basis of functions. This allows dimension reduction, optimal representation, and visualisation of data in lower dimensional spaces. The methodology is implemented in the cfda R package and is illustrated using a real data set in the clustering framework.
Mathematical Modeling of Lymph Node Drainage Function by Neural Network
Authors: Tretiakova Rufina , Setukha Alexey , Savinkov Rostislav , Grebennikov Dmitry , Bocharov Gennady
Published: December 2021

The lymph node (LN) represents a key structural component of the lymphatic system network responsible for the fluid balance in tissues and the immune system functioning. Playing an important role in providing the immune defense of the host organism, LNs can also contribute to the progression of pathological processes, e.g., the spreading of cancer cells. To gain a deeper understanding of the transport function of LNs, experimental approaches are used. Mathematical modeling of the fluid transport through the LN represents a complementary tool for studying the LN functioning under broadly varying physiological conditions. We developed an artificial neural network (NN) model to describe the lymph node drainage function. The NN model predicts the flow characteristics through the LN, including the exchange with the blood vascular systems in relation to the boundary and lymphodynamic conditions, such as the afferent lymph flow, Darcy’s law constants and Starling’s equation parameters. The model is formulated as a feedforward NN with one hidden layer. The NN complements the computational physics-based model of a stationary fluid flow through the LN and the fluid transport across the blood vessel system of the LN. The physical model is specified as a system of boundary integral equations (IEs) equivalent to the original partial differential equations (PDEs; Darcy’s Law and Starling’s equation) formulations. The IE model has been used to generate the training dataset for identifying the NN model architecture and parameters. The computation of the output LN drainage function characteristics (the fluid flow parameters and the exchange with blood) with the trained NN model required about 1000-fold less central processing unit (CPU) time than computationally tracing the flow characteristics of interest with the physics-based IE model. The use of the presented computational models will allow for a more realistic description and prediction of the immune cell circulation, cytokine distribution and drug pharmacokinetics in humans under various health and disease states as well as assisting in the development of artificial LN-on-a-chip technologies.
The Future of Medicine: Frontiers in Integrative Health and Medicine
Authors: Seetharaman Mahadevan , Krishnan Geetha , Schneider Robert H.
Published: November 2021

Despite advances in modern medicine, contemporary society has experienced a series of epidemics and pandemics of noncommunicable, chronic diseases and communicable, infectious diseases [...]
Effective Initial Treatment of Diffuse Pulmonary Lymphangiomatosis with Sirolimus and Propranolol: A Case Report
Authors: Dimiene Ieva , Bieksiene Kristina , Zaveckiene Jurgita , Andrulis Mindaugas , Optazaite Daiva-Elzbieta , Vaguliene Neringa , Zemaitis Marius , Miliauskas Skaidrius
Published: November 2021

Diffuse pulmonary lymphangiomatosis (DPL), an exceptionally rare disease, mainly occurs in children and young adults of both sexes. Even though DPL is considered to be a benign disease, its prognosis is relatively poor. Because of its rarity, little guidance on diagnosis and treatment is available, which makes working with patients with DPL challenging for clinicians. We present here a case of a young man with DPL in whom treatment with sirolimus and propranolol rapidly achieved positive radiological and clinical effects.
Zulfiqar Frailty Scale: Overview, Stakes, and Possibilities
Authors: Zulfiqar Abrar-Ahmad , Dembélé Ibrahima
Published: November 2021

Very few frailty scales are used by general practitioners, as they are time consuming and cumbersome. We developed a frailty screening tool for use in primary care, referred to as the Zulfiqar Frailty Scale (ZFS). This scale was tested in multiple general practitioners’ offices in France, and these studies were published. In this paper, we offer a summary of these results.
Steep Subthreshold Swing and Enhanced Illumination Stability InGaZnO Thin-Film Transistor by Plasma Oxidation on Silicon Nitride Gate Dielectric
Authors: Liu Yiming , Liu Chang , Qin Houyun , Peng Chong , Lu Mingxin , Chen Zhanguo , Zhao Yi
Published: November 2021

In this paper, an InGaZnO thin-film transistor (TFT) based on plasma oxidation of silicon nitride (SiNx) gate dielectric with small subthreshold swing (SS) and enhanced stability under negative bias illumination stress (NBIS) have been investigated in detail. The mechanism of the high-performance InGaZnO TFT with plasma-oxidized SiNx gate dielectric was also explored. The X-ray photoelectron spectroscopy (XPS) results confirmed that an oxygen-rich layer formed on the surface of the SiNx layer and the amount of oxygen vacancy near the interface between SiNx and InGaZnO layer was suppressed via pre-implanted oxygen on SiNx gate dielectric before deposition of the InGaZnO channel layer. Moreover, the conductance method was employed to directly extract the density of the interface trap (Dit) in InGaZnO TFT to verify the reduction in oxygen vacancy after plasma oxidation. The proposed InGaZnO TFT with plasma oxidation exhibited a field-effect mobility of 16.46 cm2/V·s, threshold voltage (Vth) of −0.10 V, Ion/Ioff over 108, SS of 97 mV/decade, and Vth shift of −0.37 V after NBIS. The plasma oxidation on SiNx gate dielectric provides a novel approach for suppressing the interface trap for high-performance InGaZnO TFT.
Design and Development of a Computational Tool for a Dialyzer by Using Computational Fluid Dynamic (CFD) Model
Authors: Yaqoob Tuba , Ahsan Muhammad , Farrukh Sarah , Ahmad Iftikhar
Published: November 2021

In order to reduce the hemodialysis cost and duration, an investigation of the effect of dialyzer design and process variables on the solute clearance rate is required. It is not easy to translate the in vivo transfer process with in vitro experiments, as it involves a high cost to produce various designs and membranes for the dialyzer. The primary objective of this study was the design and development of a computational tool for a dialyzer by using a computational fluid dynamic (CFD) model. Due to their complexity, only researchers with expertise in computational analysis can use dialyzer models. Therefore, COMSOL Inc. (Stockholm, Sweden) has made an application on membrane dialysis to study the impact of different design and process parameters on dialyzed liquid concentration. Still, membrane mathematical modeling is not considered in this application. This void hinders an investigation of the impact of membrane characteristics on the solute clearance rate. This study has developed a stand-alone computational tool in COMSOL Multiphysics 5.4 to fill this void. A review of the literature conducted shows that there are no suitable stand-alone computational tools for kidney dialysis. Very little work has been undertaken to validate the stand-alone computational tool. Medical staff in the hospitals require a computational tool that can be installed quickly and provide results with limited knowledge of dialysis. This work aims to construct a user-friendly computational tool to solve this problem. The development of a user-friendly stand-alone computational tool for the dialyzer is described thoroughly. This application simulates a mathematical model with the Finite Element Method using the COMSOL Multiphysics solver. The software tool is converted to a stand-alone version with the COMSOL compiler. The stand-alone computational tool provides the clearance rate of six different toxins and module packing density. Compared with the previous application, the stand-alone computational tool of membrane dialysis enables the user to investigate the impact of membrane characteristics and process parameters on the clearance rate of different solutes. The results are also inconsistent with the literature data, and the differences ranges are 0.09–6.35% and 0.22–2.63% for urea clearance rate and glucose clearance rate, respectively. Statistical analysis of the results is presented as mean with 95% confidence intervals (CIs) and p values 0.9472 and 0.833 of the urea and glucose clearance rates, respectively.
Comparative Atomic-Level Analysis of Sorption and Diffusion Properties of Membrane Materials on the Base of Polymer and Its Prepolymer: A Case Study of Polyheteroarylenes
Authors: Petrov Andrey V. , Toikka Alexander M.
Published: November 2021

The sorption properties of polymers and the mobility of penetrants are the main factors which determine the trans-membrane processes. Other factors concern the membrane material structure and chemical nature. In this paper, we consider the case of polymers with similar structure units, namely a polymer and its pre-polymer (polybenzoxazinoneimide and imide-containing polyamic acid). The available experimental data show a great difference in the pervaporation process using these two polymeric membranes. Some explanation of this difference can be found at the atomic-level study. A comparative analysis of the diffusion of water and isopropanol molecules was carried out using the density functional theory and molecular dynamics simulations
Putative Internal Control Genes in Bovine Milk Small Extracellular Vesicles Suitable for Normalization in Quantitative Real Time-Polymerase Chain Reaction
Authors: Rahman Md. Matiur , Takashima Shigeo , Kamatari Yuji O. , Badr Yassien , Shimizu Kaori , Okada Ayaka , Inoshima Yasuo
Published: November 2021

Bovine milk small extracellular vesicles (sEVs) contain many biologically important molecules, including mRNAs. Quantitative real-time polymerase chain reaction (qRT-PCR) is a widely used method for quantifying mRNA in tissues and cells. However, the use, selection, and stability of suitable putative internal control genes in bovine milk sEVs for normalization in qRT-PCR have not yet been identified. Thus, the aim of the present study was to determine suitable putative internal control genes in milk sEVs for the normalization of qRT-PCR data. Milk sEVs were isolated from six healthy Holstein-Friesian cattle, followed by RNA extraction and cDNA synthesis. In total, 17 mRNAs were selected for investigation and quantification using qRT-PCR; they were further evaluated using geNorm, NormFinder, BestKeeper, and ∆CT algorithms to identify those that were highly stable putative internal control genes in milk sEVs. The final ranking of suitable putative internal control genes was determined using RefFinder. The mRNAs from TUB, ACTB, DGKZ, ETFDH, YWHAZ, STATH, DCAF11, and EGFLAM were detected in milk sEVs from six cattle by qRT-PCR. RefFinder demonstrated that TUB, ETFDH, and ACTB were highly stable in milk sEVs, and thus suitable for normalization of qRT-PCR data. The present study suggests that the use of these genes as putative internal control genes may further enhance the robustness of qRT-PCR in bovine milk sEVs. Since these putative internal control genes apply to healthy bovines, it would be helpful to include that the genes were stable in sEVs under “normal or healthy conditions”.
Enhanced Specific Mechanism of Separation by Polymeric Membrane Modification—A Short Review
Authors: Siekierka Anna , Smolińska-Kempisty Katarzyna , Wolska Joanna
Published: November 2021

Membrane technologies have found a significant application in separation processes in an exceeding range of industrial fields. The crucial part that is decided regarding the efficiency and effectivity of separation is the type of membrane. The membranes deal with separation problems, working under the various mechanisms of transportation of selected species. This review compares significant types of entrapped matter (ions, compounds, and particles) within membrane technology. The ion-exchange membranes, molecularly imprinted membranes, smart membranes, and adsorptive membranes are investigated. Here, we focus on the selective separation through the above types of membranes and detect their preparation methods. Firstly, the explanation of transportation and preparation of each type of membrane evaluated is provided. Next, the working and application phenomena are evaluated. Finally, the review discusses the membrane modification methods and briefly provides differences in the properties that occurred depending on the type of materials used and the modification protocol.
High Photoresponse Black Phosphorus TFTs Capping with Transparent Hexagonal Boron Nitride
Authors: Yue Dewu , Rong Ximing , Han Shun , Cao Peijiang , Zeng Yuxiang , Xu Wangying , Fang Ming , Liu Wenjun , Zhu Deliang , Lu Youming
Published: December 2021

Black phosphorus (BP), a single elemental two-dimensional (2D) material with a sizable band gap, meets several critical material requirements in the development of future nanoelectronic applications. This work reports the ambipolar characteristics of few-layer BP, induced using 2D transparent hexagonal boron nitride (h-BN) capping. The 2D h-BN capping have several advantages over conventional Al2O3 capping in flexible and transparent 2D device applications. The h-BN capping technique was used to achieve an electron mobility in the BP devices of 73 cm2V−1s−1, thereby demonstrating n-type behavior. The ambipolar BP devices exhibited ultrafast photodetector behavior with a very high photoresponsivity of 1980 mA/W over the ultraviolet (UV), visible, and infrared (IR) spectral ranges. The h-BN capping process offers a feasible approach to fabricating n-type behavior BP semiconductors and high photoresponse BP photodetectors.
In Situ Evaluation of the Influence of Interstitial Oxygen on the Elastic Modulus of La2NiO4
Authors: Kimura Yuta , Nakamura Takashi , Amezawa Koji , Yashiro Keiji , Kawada Tatsuya
Published: November 2021

Lattice defects significantly affect the mechanical properties of crystalline metal oxides. The materials for the components of solid oxide fuel cells (SOFCs) are no exception, and hence understanding of the interplay between lattice defects and the mechanical properties of components is important to ensure the mechanical stability of SOFCs. Herein, we performed an in situ evaluation of the temperature and P(O2) dependence of the elastic moduli of La2NiO4 (LN214), a candidate for the cathode material of SOFCs, using the resonance method to understand the influence of interstitial oxygen on its elastic properties. Above 873 K, both the Young’s and shear moduli of LN214 slightly decreased with increasing P(O2), suggesting that these elastic moduli are correlated with interstitial oxygen concentration and decreased with increasing interstitial oxygen. We analyzed the influence of interstitial oxygen on the Young’s modulus of LN214, based on numerically obtained lattice energy. The P(O2) dependence of the Young’s modulus of LN214 was found to be essentially explained by variation in the c-lattice constant, which was triggered by variation in interstitial oxygen concentration. These findings may contribute to a better understanding of the relationship between lattice defects and mechanical properties, and to the improvement of the mechanical stability of SOFCs.
High-Temperature Surface Oxide Growth Kinetics of Al–Si–Zr Bulk Alloys and Ribbons
Authors: Kiradzhiyska Denitsa , Vassilev Gueorgui , Mancheva Rositsa , Yaneva Svetlana , Milcheva Nikolina
Published: November 2021

A typical modification technique of the functional properties of Al–Si based alloys is the addition of some third element in trace level. In the present work, ternary Al–Si–Zr bulk and ribbon alloys have been prepared. The kinetics of high-temperature surface oxidation has been studied by thermogravimetric method. It was found that at the start of the experiment the chemical reaction velocity is rate-controlling while for longer times the (oxygen) diffusion is the rate-controlling process. Activation energy of the two stages of oxidation has been obtained. Additional studies such as thermochemical analysis, optical and electron microscopy, and microhardness tests have been done.
Microstructure, Mechanical Properties, and Thermal Stability of Carbon-Free High Speed Tool Steel Strengthened by Intermetallics Compared to Vanadis 60 Steel Strengthened by Carbides
Authors: Michalcová Alena , Pečinka Vojtěch , Kačenka Zdeněk , Šerák Jan , Kubásek Jiří , Novák Pavel , Vojtěch Dalibor
Published: November 2021

High speed tool steels are materials that exhibit superior mechanical properties (e.g., high hardness). They should also be resistant to thermal exposure to maintain high hardness during the machining process. In this paper, a C-free tool steel formed of Fe matrix and a Mo6Co7 intermetallic phase was studied. This steel was compared to the well-known Vanadis 60 steel containing Fe matrix and carbides. Microstructures were investigated by scanning (SEM) and transmission (TEM) electron microscopy, and the mechanical properties and thermal stability of both materials were compared. It was proven that the strengthening in the Vanadis 60 steel was mainly caused by the carbides, while the C-free steel was strengthened by the Mo6Co7 phase. The hardness values of both materials were comparable in the utilization state (approx. 950 HV). The hardness of Vanadis 60 steel decreased after several minutes of annealing at 650 °C under the value that enables material utilization. The hardness value of the steel strengthened by the intermetallics also decreased but significantly slower. Based on these results, the main finding of this study is that the C-free steel exhibited much better thermal stability and may be utilized at higher temperatures for longer periods of time than Vanadis 60.
Influence of Preheating Temperature on Changes in Properties in the HAZ during Multipass MIG Welding of Alloy AW 6061 and Possibilities of Their Restoration
Authors: Novakova Iva , Moravec Jaromir , Novak Jan , Solfronk Pavel
Published: November 2021

Fusion welding of heat-treatable aluminum alloys is generally accompanied by a significant decrease in mechanical properties in the HAZ caused by the dissolution of the hardening phase. The intensity of this decrease in mechanical properties can be reduced by limiting the heat input value. However, this approach is in direct conflict with the principles for welding aluminum and its alloys. Due to the very high thermal conductivity of aluminum alloys, it is necessary to use preheating for thicknesses larger than 5 mm to eliminate non-penetration and cold joints. This paper aims to show the influence of multiple temperature cycles, performed at different preheating temperatures, on changes in the microstructure and mechanical properties. At the same time, the extent to which the original properties of the material can be restored by natural and artificial aging at 160, 175 and 190 °C is also investigated.
Selective Leaching of Molybdenum from Bulk Concentrate by Electro-Oxidation
Authors: Chung Kyeong Woo , Yoon Ho-Sung , Kim Chul-Joo , Jeon Ho-Seok
Published: November 2021

This paper proposes selective leaching of molybdenum from Mo/Cu complex bulk concentrates in a 5 M NaCl solution using the electro-oxidation method. Here, the effects of several factors such as pH, pulp density, current density, and temperatures were investigated. A higher leaching yield of Mo increased with increasing pH from 5 to 9 and decreased with increasing pulp density from 1 to 10%. A rise in current density did not help enhance Mo, and the elevating temperature did not always result in a higher leaching yield. Application of ultrasonic led to higher leaching yield of Mo. Ninety-two percent of leaching yield was obtained upon leaching of Mo in 5 M NaCl at 25 °C, pulp density of 5%, and the current density of 0.292 A/g under ultrasonic irradiation with a power of 27 kW. The resultant residue mainly consisted of chalcopyrite.
Innovations in Monitoring, Control and Design of Laser and Laser-Arc Hybrid Welding Processes
Authors: Ma Zheng-Xiong , Cheng Pei-Xin , Ning Jie , Zhang Lin-Jie , Na Suck-Joo
Published: November 2021

With the rapid development of high power laser, laser welding has been widely used in many fields including manufacturing, metallurgy, automobile, biomedicine, electronics, aerospace etc. Because of its outstanding advantages, such as high energy density, small weld size, easy automation. Combining the two heat sources of laser and arc for welding can achieve excellent results due to the synergistic effect. Laser welding is a complicated physical and chemical metallurgical process, involving the laser beam and molten pool, keyholes and materials melting, evaporation and multiple physical process. Process monitoring and quality control are important content of research and development in the field of laser welding, which is the premise to obtain fine weld with high quality. Numerical simulation technology can describe many complex physical phenomena in welding process, which is very important to predict weld forming and quality and clarify the underline mechanism. In this paper, the research progress of process monitoring, quality control and autonomous intelligent design of laser and laser-arc hybrid welding based on numerical simulation were reviewed, and the research hotspots and development trends of laser welding in the future are predicted.
A Novel Classification Method for Pores in Laser Powder Bed Fusion
Authors: Nudelis Natan , Mayr Peter
Published: November 2021

Nowadays, additive manufacturing (AM) using laser powder bed fusion (LPBF) is acknowledged for its ability to generate near-net-shape components for various industries such as aerospace, automotive, and health industries. However, internal defects seem to be the inevitable concomitant in the current state of laser powder bed fusion of Al alloys. Hence, knowledge of the formation, different types, and morphologies of pores and their suppression is an essential element for successful future AM applications. The purpose of this research is to qualify a new approach of defect classification using X-ray tomography. In this framework, this research examined the influence of size, shape, and location of pores on crack initiation for AlSi10Mg parts produced by LPBF. For this reason, a total number of 39,228 pores detected in a cylindrical sample were categorised. Additionally, 26 selected pores of different morphology from the X-ray scan were analysed by means of finite element analysis (FEA). Moreover, fracture mechanics determinations were carried out to examine the correlations between pore characteristics and degree of stress concentration. The result is an evaluated novel pore classification method that can be used for process adjustments, quality assurance, as well as further research.
Enhanced Leaching of Zinc from Zinc-Containing Metallurgical Residues via Microwave Calcium Activation Pretreatment
Authors: Ma Aiyuan , Zheng Xuemei , Gao Lei , Li Kangqiang , Omran Mamdouh , Chen Guo
Published: November 2021

Given the shortage of zinc resource, the low utilisation efficiency of secondary zinc resource, and the crucial problem that the synchronous dissolution of zinc from different mineral phases, an activation pretreatment method merged with calcium activation and microwave heating approach was proposed to enhance the zinc leaching from complex encapsulated zinc-containing metallurgical residues (ZMR). Results indicated that under the optimal pretreatment conditions, including microwave activation temperature of 400 °C, CaO addition of 25% and activation time of 20 min, the zinc leaching rate reached 91.67%, which was 3.9% higher than that by conventional roasting pretreatment. Meanwhile, microwave heating presents excellent treatment effects, manifested by the zinc leaching rates, all exceeding that of conventional roasting under the same conditions, while the process temperature is decreased by 200 °C. In addition, XRD and SEM-EDS analysis denoted that microwave calcification pretreatment can effectively promote the transformation of the refractory zinc minerals like Zn2SiO4 and ZnFe2O4 into the easily leachable zinc oxides. The distinctive selective heating characteristics of microwave heating strengthened the dissociation of mineral inclusion, and the generated cracks increased the interfacial reaction area and further enhancing the leaching reaction of zinc from ZMR.
How Austenitic Is a Martensitic Steel Produced by Laser Powder Bed Fusion? A Cautionary Tale
Authors: Zhang Fan , Stoudt Mark R. , Hammadi Souzan , Campbell Carelyn E. , Lass Eric A. , Williams Maureen E.
Published: November 2021

Accurate phase fraction analysis is an essential element of the microstructural characterization of alloys and often serves as a basis to quantify effects such as heat treatment or mechanical deformation. Additive manufacturing (AM) of metals, due to the intrinsic nonequilibrium solidification and spatial variability, creates additional challenges for the proper quantification of phase fraction. Such challenges are exacerbated when the alloy itself is prone to deformation-induced phase transformation. Using commonly available in-house X-ray diffraction (XRD) and electron backscatter diffraction (EBSD) and less commonly used synchrotron-based high-energy X-ray diffraction, we characterized nitrogen-atomized 17-4 precipitation-hardening martensitic stainless steel, a class of AM alloy that has received broad attention within the AM research community. On the same build, our measurements recovered the entire range of reported values on the austenite phase fractions of as-built AM 17-4 in literature, from ≈100% martensite to ≈100% austenite. Aided by Calphad simulation, our experimental findings established that our as-built AM 17-4 is almost fully austenitic and that in-house XRD and EBSD measurements are subject to significant uncertainties created by the specimen’s surface finish. Hence, measurements made using these techniques must be understood in their correct context. Our results carry significant implications, not only to AM 17-4 but also to AM alloys that are susceptible to deformation-induced structure transformation and suggest that characterizations with less accessible but bulk sensitive techniques such as synchrotron-based high energy X-ray diffraction or neutron diffraction may be required for proper understanding of these materials.
Hot-Deformation Behavior and Processing Maps of a Low-Carbon Fe-2 wt% Nb Steel
Authors: Luo Wentao , Cai Pengzhan , Hou Ziyong , Wang Yuhui , Zhang Ling , Wu Guilin
Published: December 2021

In the present work, the deformation behavior and processing maps of a low-carbon Fe-2 wt% Nb steel were studied by means of hot-compression tests at temperatures of 800–1150 °C and strain rates of 0.01–10 s−1. The hot-processing maps at different strains and corresponding microstructural evolution were constructed and discussed. The hot-deformation behaviors of two different phase regions, i.e., austenite + NbC dual-phase and ferrite + NbC dual-phase, were predicted by determining the constitutive equations using Arrhenius-type and Zener–Hollomon models. The results suggest that the hot-deformed microstructures of the material present a strong correlation with the processing parameters in the hot-processing maps. In addition, the optimum parameters based on the processing maps were obtained, and the instable and the safe domains during the hot deformation in the hot-processing maps provide solid theoretical guidance for industrial production.
Amino Acid and Phospholipid Metabolism as an Indicator of Inflammation and Subtle Cardiomyopathy in Patients with Marfan Syndrome
Authors: Bartenbach Lisa , Karall Thomas , Koch Jakob , Keller Markus Andreas , Oberacher Herbert , Scholl-Bürgi Sabine , Karall Daniela , Oemer Gregor , Baumgartner Daniela , Meinel Katharina , Aly Safwat , Odri-Komazec Irena , Geiger Ralf , Michel Miriam
Published: November 2021

Patients with Marfan syndrome (MFS) have an increased risk of aortic aneurysm formation, dissection and development of a subtle cardiomyopathy. We analyzed amino acid and lipid metabolic pathways in MFS patients, seeking biomarker patterns as potential monitoring tools of cardiovascular risk with deterioration of myocardial function. We assessed myocardial function in 24 adult MFS patients and compared traditional laboratory values and mass spectrometry-based amino acid, phospholipid and acylcarnitine metabolomes in patients with those in healthy controls. Analytes for which values differed between patients and controls were subjected to regression analysis. A high proportion of patients had signs of impaired diastolic function and elevated serum levels of NT-proBNP. Patients had lower serum levels of taurine, histidine and PCaeC42:3 than controls. The evidence of diastolic dysfunction, aortic root dimensions and history of aortic root surgery correlated with NT-proBNP and taurine levels. Alterations in serum levels of metabolism derived analytes link MFS pathophysiology with inflammation, oxidative stress and incipient cardiomyopathy.
Untargeted Microbial Exometabolomics and Metabolomics Analysis of Helicobacter pylori J99 and jhp0106 Mutant
Authors: Kao Cheng-Yen , Kuo Pei-Yun , Liao Hsiao-Wei
Published: November 2021

Untargeted metabolomic profiling provides the opportunity to comprehensively explore metabolites of interest. Herein, we investigated the metabolic pathways associated with Jhp0106, a glycosyltransferase enzyme in Helicobacter pylori. Through untargeted exometabolomic and metabolomic profiling, we identified 9 and 10 features with significant differences in the culture media and pellets of the wild-type (WT) J99 and jhp0106 mutant (Δjhp0106). After tentative identification, several phosphatidylethanolamines (PEs) were identified in the culture medium, the levels of which were significantly higher in WT J99 than in Δjhp0106. Moreover, the reduced lysophosphatidic acid absorption from the culture medium and the reduced intrinsic diacylglycerol levels observed in Δjhp0106 indicate the possibility of reduced PE synthesis in Δjhp0106. The results suggest an association of the PE synthesis pathway with flagellar formation in H. pylori. Further investigations should be conducted to confirm this finding and the roles of the PE synthesis pathway in flagellar formation. This study successfully demonstrates the feasibility of the proposed extraction procedure and untargeted exometabolomic and metabolomic profiling strategies for microbial metabolomics. They may also extend our understanding of metabolic pathways associated with flagellar formation in H. pylori.
Enhancing Metabolomic Coverage in Positive Ionization Mode Using Dicationic Reagents by Infrared Matrix-Assisted Laser Desorption Electrospray Ionization
Authors: Xi Ying , Muddiman David C.
Published: November 2021

Mass spectrometry imaging is a powerful tool to analyze a large number of metabolites with their spatial coordinates collected throughout the sample. However, the significant differences in ionization efficiency pose a big challenge to metabolomic mass spectrometry imaging. To solve the challenge and obtain a complete data profile, researchers typically perform experiments in both positive and negative ionization modes, which is time-consuming. In this work, we evaluated the use of the dicationic reagent, 1,5-pentanediyl-bis(1-butylpyrrolidinium) difluoride (abbreviated to [C5(bpyr)2]F2) to detect a broad range of metabolites in the positive ionization mode by infrared matrix-assisted laser desorption electrospray ionization mass spectrometry imaging (IR-MALDESI MSI). [C5(bpyr)2]F2 at 10 µM was doped in 50% MeOH/H2O (v/v) electrospray solvent to form +1 charged adducted ions with anionic species (−1 charged) through post-electrospray ionization. This method was demonstrated with sectioned rat liver and hen ovary. A total of 73 deprotonated metabolites from rat liver tissue sections were successfully adducted with [C5(bpyr)2]2+ and putatively identified in the adducted positive ionization polarity, along with 164 positively charged metabolite ions commonly seen in positive ionization mode, which resulted in 44% increased molecular coverage. In addition, we were able to generate images of hen ovary sections showing their morphological features. Following-up tandem mass spectrometry (MS/MS) indicated that this dicationic reagent [C5(bpyr)2]2+ could form ionic bonds with the headgroup of glycerophospholipid ions. The addition of the dicationic reagent [C5(bpyr)2]2+ in the electrospray solvent provides a rapid and effective way to enhance the detection of metabolites in positive ionization mode.
Predicting Hair Cortisol and Cortisone Concentration in Postpartum Women through Repeated Measurements of Perceived Stress
Authors: Lang Jessica , Stickel Susanne , Gaum Petra M. , Habel Ute , Bertram Jens , Eickhoff Simon B. , Chechko Natalia
Published: November 2021

To investigate whether hair cortisol (HCC) and hair cortisone (HCNC) can be predicted by repeated stress reports from postpartum women in different mental health conditions (non-depressed, ND, adjustment disorder, AD, postpartum depression, PPD), 240 mothers (mean age 31.8 years; SD = 4.7) were monitored from within 1 to 6 days of childbirth over a period of three months. HCC and HCNC in 3 cm hair samples were assessed via triple mass spectrometry after liquid chromatographic separation. Every second day, participants reported their stress levels online. The summed perceived stress scores were not found to be predictive of HCC. However, perceived stress predicted a decrease in HCNC (rSpearman = –0.153, p = 0.035) and an increase in the HCC/HCNC ratio (rSpearman = 0.304, p < 0.001) in the ND group. With AD in the first few weeks after childbirth, an inverse effect appeared for HCNC (rSpearman = 0.318, p = 0.011), suggesting an overall downregulation of the HPA axis owing to the stressful experience of adjusting to the new situation. No effects were found for mothers developing PPD. The indirect results of HPA-axis activity are better indicators of the experience of psychological stress in postpartum women than the absolute HCC value.
Low Subthreshold Slope AlGaN/GaN MOS-HEMT with Spike-Annealed HfO2 Gate Dielectric
Authors: Yeom Min Jae , Yang Jeong Yong , Lee Chan Ho , Heo Junseok , Chung Roy Byung Kyu , Yoo Geonwook
Published: November 2021

AlGaN/GaN metal-oxide semiconductor high electron mobility transistors (MOS-HEMTs) with undoped ferroelectric HfO2 have been investigated. Annealing is often a critical step for improving the quality of as-deposited amorphous gate oxides. Thermal treatment of HfO2 gate dielectric, however, is known to degrade the oxide/nitride interface due to the formation of Ga-containing oxide. In this work, the undoped HfO2 gate dielectric was spike-annealed at 600 °C after the film was deposited by atomic layer deposition to improve the ferroelectricity without degrading the interface. As a result, the subthreshold slope of AlGaN/GaN MOS-HEMTs close to 60 mV/dec and on/off ratio>109 were achieved. These results suggest optimizing the HfO2/nitride interface can be a critical step towards a low-loss high-power switching device.
Special Issue on Versatile Organ-on-a-Chip Devices
Authors: Dér András
Published: November 2021

The tremendous success of microelectronics at the end of the 20th century, often symbolized by “Moore’s law”, is based on miniaturization of the active and passive elements of electronic circuits [...]
Biomimetic Deposition of Hydroxyapatite Layer on Titanium Alloys
Authors: Baltatu Madalina Simona , Sandu Andrei Victor , Nabialek Marcin , Vizureanu Petrica , Ciobanu Gabriela
Published: November 2021

Over the last decade, researchers have been concerned with improving metallic biomaterials with proper and suitable properties for the human body. Ti-based alloys are widely used in the medical field for their good mechanical properties, corrosion resistance and biocompatibility. The TiMoZrTa system (TMZT) evidenced adequate mechanical properties, was closer to the human bone, and had a good biocompatibility. In order to highlight the osseointegration of the implants, a layer of hydroxyapatite (HA) was deposited using a biomimetic method, which simulates the natural growth of the bone. The coatings were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD), micro indentation tests and contact angle. The data obtained show that the layer deposited on TiMoZrTa (TMZT) support is hydroxyapatite. Modifying the surface of titanium alloys represents a viable solution for increasing the osseointegration of materials used as implants. The studied coatings demonstrate a positive potential for use as dental and orthopedic implants.