bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical investigation of effective parameters of falling film evaporation in a vertical‐tube evaporator
Authors: Haghsheno Maryam , Kouhikamali Ramin
Published: November 2020

Wastewater treatment is one of the most effective solutions to manage the problem of water scarcity. Falling film evaporators are excellent technology in wastewater treatment plants. These wastewater evaporators provide high heat transfer, short residence time in the heating zone, and high‐purity distilled water. In the present study, the mechanism of turbulent falling film evaporation in a vertical tube has been investigated. A model has been developed for symmetrical two‐dimensional pure and saline water flow in a vertical tube under constant wall heat flux. The numerical simulation has been carried out by a commercial computational fluid dynamics code. The evaporation of saturated liquid film is simulated utilizing a two‐phase volume of fluid method and Tanasawa phase‐change model. The main objective of this study is to evaluate the effects of water salinity, liquid Reynolds number, wall heat flux, and liquid film thickness on the two‐phase heat transfer coefficient and vapor volume fraction. The numerical heat transfer coefficients are compared with the obtained results by Chen's empirical correlation. With a MAPE ≤ 11%, this study proves that the numerical method is highly effective at predicting the heat transfer coefficient. Moreover, the empirical coefficient of the Tanasawa model and the minimum thickness of the falling film are determined.
Perceptions of safety and subjective well‐being of Brazilian children
Authors: Sarriera Jorge Castellá , Bedin Lívia Maria , Strelhow Miriam Raquel W.
Published: November 2020

Safety is considered an important aspect of life and well‐being. However, few studies have examined the relationship between safety and well‐being among children, especially in Latin American. This study aims at analyzing the relationship between perceptions of safety and children's subjective well‐being, considering children's school, city context, and sex. Participants were 2,200 Brazilian children (10–13 years old) who answered the single item on Overall Life Satisfaction, the Satisfaction With Life Student Scale, and four items regarding safety perceptions. Through analysis of variance and structural equation modeling (SEM), results indicate that children who live in inner cities and study in private schools have significantly higher averages of safety perception. Also, boys present higher averages about how safe they feel. SEM presents a positive and significant relationship between safety perception and children's subjective well‐being and multigroup SEM indicates invariance of the model across groups. Safety is presented as an important component of well‐being. Interventions aimed at promoting safety and community ties can enhance children's well‐being.
Psychological sense of community and motivation toward collective social change among community coalition members of color in the southwestern United States
Authors: Lardier David T. , Merrill Erica A. , Cantu Irene N.
Published: November 2020

Drawing on McMillan and Chavis's psychological sense of community framework among southwestern community coalition members (N = 18), data were examined for narratives of how psychological sense of community and experiences of community manifest among coalition members. We were also interested in knowing how coalition members make meaning of social change. Findings illustrate that dimensions of psychological sense of community (e.g., membership, emotional connection, needs' fulfillment, and influence) are important in how members made meaning of community needs and their own participation in the coalition. Implications are put forward for theory and community programming.
Hospital Dentistry: The Swiss‐Army Knife of Dental Medicine
Authors: Kunkel George H. , Roberts Gary K.
Published: November 2020

Hospital Dentistry is an inclusive synergism of the recognized dental specialties in an emergency/hospital atmosphere. This perspective composition serves to display the breadth of Hospital Dentistry from an observational and creative viewpoint while elucidating the role of the Hospital Dentist in the dynamic large university hospital setting. It calls for increased awareness of the field of Hospital Dentistry and the potential for its specialized role in the future of dental medicine. Hospital‐based General Practice Residencies (GPR) expose trainees to Hospital Dentistry and its integrated role in medicine. Exploring the ventures of Hospital Dentistry highlight the need to increase Hospital Dentistry‐focused student groups while encouraging advanced dental education through GPR programs. The rising geriatric community, complex patient caseload, and population growth call for the need to expand the field of Hospital Dentistry through its recognition as a specialty in the future of dental medicine.
Predictive value of cytokine/chemokine responses for the disease severity and management in children and adult cases with COVID‐19
Authors: Ozsurekci Yasemin , Aykac Kubra , Er Ahmet Gorkem , Halacli Burcin , Arasli Mehmet , Oygar Pembe Derin , Gürlevik Sibel , Cura Yayla Burcu Ceylan , Karakaya Jale , Alp Alparslan , Topeli Arzu , Cengiz Ali Bülent , Akova Murat , Ceyhan Mehmet
Published: November 2020

The disease course of children with coronavirus disease 2019 (COVID‐19) seems milder as compared with adults, however, actual reason of the pathogenesis still remains unclear. There is a growing interest on possible relationship between pathogenicity or disease severity and biomarkers including cytokines or chemokines. We wondered whether these biomarkers could be used for the prediction of the prognosis of COVID‐19 and improving our understanding on the variations between pediatric and adult cases with COVID‐19. The acute phase serum levels of 25 cytokines and chemokines in the serum samples from 60 COVID‐19 pediatric (n = 30) and adult cases (n = 30) including 20 severe or critically ill, 25 moderate and 15 mild patients and 30 healthy pediatric (n = 15) and adult (n = 15) volunteers were measured using commercially available fluorescent bead immunoassay and analyzed in combination with clinical data. Interferon gamma‐induced protein 10 (IP‐10) and macrophage inflammatory protein (MIP)−3β levels were significantly higher in patient cohort including pediatric and adult cases with COVID‐19 when compared with all healthy volunteers (p ≤ .001 in each) and whereas IP‐10 levels were significantly higher in both pediatric and adult cases with severe disease course, MIP‐3β were significantly lower in healthy controls. Additionally, IP‐10 is an independent predictor for disease severity, particularly in children and interleukin‐6 seems a relatively good predictor for disease severity in adults. IP‐10 and MIP‐3β seem good research candidates to understand severity of COVID‐19 in both pediatric and adult population and to investigate possible pathophysiological mechanism of COVID‐19.
Investigating glass beads and the funerary rituals of ancient Vaccaei culture (S. IV‐I BC) by Raman spectroscopy
Authors: Pinto J. , Prieto A.C. , Coria‐Noguera J.C. , Sanz‐Minguez C. , Souto J.
Published: November 2020

Glass pieces were highly appreciated goods in the Protohistory of the Iberian Peninsula. The specialized production of these glass pieces seems noncompatible with local workshops, and therefore, they are proof of commercial relationships with other cultures with the technical capability to produce such pieces. However, detailed studies of glass beads of archaeological relevance are scarce, as these samples usually appeared without a clear historical context. Nevertheless, the archaeological site of Pintia (Padilla de Duero, Valladolid, Spain) is a relevant exception to this situation. About 600 pieces have been recovered by 2018, with a significant percentage found in closed tombs. In this work, a set of 15 representative pieces from the Vaccaei culture (IV‐I centuries BC) have been studied by Raman spectroscopy and ESEM/EDX. The combination of both techniques provided valuable information about the fabrication of these samples, identifying diverse features that could be related to different workshops or origins. In particular, the characteristics of a sophisticated bifacial pendant were found to be compatible with their provenance from Carthage. Also, some of the pigments employed on these samples were identified by Raman spectroscopy, finding lead oxides, calcium antimoniate, hematite, and Naples yellow. The diverse trousseaus and viatic offerings found in the Vaccaei tombs show the relevance and complexity of the funerary cremation rituals in their culture. The study by Raman spectroscopy of well‐preserved and thermally altered glass beads found in the same tomb allowed estimating the maximum temperature reached during the cremation in about 600°C, which confirmed previous estimations derived from the state of conservation of the bone remains.
Resolution Enhancement and Background Suppression in Optical Super‐Resolution Imaging for Biological Applications
Authors: Li Chuankang , Le Vannhu , Wang Xiaona , Hao Xiang , Liu Xu , Kuang Cuifang
Published: November 2020

For decades, the spatial resolution of conventional far‐field optical imaging has been constrained due to the diffraction limit. The emergence of optical super‐resolution imaging has facilitated biological research in the nanoscale regime. However, the existing super‐resolution modalities are not feasible in many biological applications due to weaknesses, like complex implementation and high cost. Recently, various newly proposed techniques are advantageous in the enhancement of the system resolution, background suppression, and improvement of the hardware complexity so that the above‐mentioned issues could be addressed. Most of these techniques entail the modification of factors, like hardware, light path, fluorescent probe, and algorithm, based on conventional imaging systems. Particularly, subtraction technique is an easily implemented, cost‐effective, and flexible imaging tool which has been applied in widespread utilizations. In this review, the principles, characteristics, advances, and biological applications of these techniques are highlighted in optical super‐resolution modalities.
Enhanced Graphene Plasmonic Mode Energy for Highly Sensitive Molecular Fingerprint Retrieval
Authors: Nong Jinpeng , Tang Linlong , Lan Guilian , Luo Peng , Li Zhancheng , Huang Deping , Yi Juemin , Shi Haofei , Wei Wei
Published: November 2020

Graphene plasmons with tightly confined fields and actively tunable resonant frequencies enable the selective detection of molecular vibrational fingerprints with ultrahigh sensitivity, significantly promoting the development of surface‐enhanced infrared absorption spectroscopies (SEIRAS). However, current experimentally obtained enhancements are much smaller than the theoretical prediction due to the extremely low graphene plasmonic mode energy. In this paper, the strategies to improve the mode energy are theoretically and experimentally investigated in a one‐port graphene plasmonic system. By optimizing the Fabry–Pérot cavity length and employing multi‐layer graphene to drive the system into the near critical coupling regime, the localized graphene plasmonic absorptions can be improved from 3% to more than 92%. This induces a 37 times improvement of graphene plasmonic mode energy from 0.4 × 10−13 to 1.5 × 10−12 J per period for the strong plasmon–molecule interactions, enabling the highly sensitive detection of 8 nm thick molecular film. The SEIRAS experimental results demonstrate that a maximum enhancement factor of 162 can be achieved, which is one order larger than that of the reported localized graphene plasmonic sensors. The results showcase the practical usability of localized graphene plasmons for the next‐generation high sensitive nanoscale infrared spectroscopy.
Extremely Polarized and Efficient Hot Electron Intraband Luminescence from Aluminum Nanostructures for Nonlinear Optical Encoding
Authors: Zhang Yinan , Han Jing , Shi Liu , Chen Shiren , Feng Ziwei , Lu Hua , Gu Min , Li Xiangping
Published: November 2020

Hot electron intraband luminescence from plasmonic nanostructures is of critical importance for integrated photonic devices and applications in ultracompact nanospectrometer, bioimaging, information encryption et al. Although, the past few decades have witnessed tremendous progress in enhancing the luminescence efficiency of plasmonic nanostructures, the luminescence is usually unpolarized or partially polarized and difficult to be tailored because of its incoherent and broadband feature, significantly limiting its applications. Here the current limitation, demonstrating extremely polarized hot electron intraband luminescence with record‐high degree of linear polarization (≈1) and ≈40 000‐fold enhancement from judiciously designed aluminium (Al) plasmonic nanostructures, is broken through. The designed nanostructures exhibit strong polarization‐dependent anisotropic scattering across the visible band which efficiently modulates the luminescence in orthogonal directions. Leveraging this appealing feature, high‐contrast analyzer controlled optical image encryption and camouflage for information security applications are demonstrated. This research lays the groundwork for integrated nonlinear photonic devices based on complementary metal–oxide–semiconductor (CMOS)‐compatible plasmonic materials and paves the way for ultracompact on‐chip photonic devices demanding polarized white light sources.
Polarization‐Engineered Noninterleaved Metasurface for Integer and Fractional Orbital Angular Momentum Multiplexing
Authors: Zhang Kuang , Yuan Yueyi , Ding Xumin , Li Haoyu , Ratni Badreddine , Wu Qun , Liu Jian , Burokur Shah Nawaz , Tan Jiubin
Published: November 2020

Vortex beam carrying orbital angular momentum (OAM) has been widely explored in optical and microwave regions attributed to its potential characteristics in communication systems. For circular polarization incidence, Pancharatnam–Berry (PB) phase is a direct resource to generate phase gradient along the azimuthal direction required by specific OAM mode. The main drawback of PB phase is that it only affects cross‐polarized fields and keeps the copolarized part unmodulated. Here, a paradigm‐shift perspective of noninterleaved metasurfaces is proposed, which can simultaneously generate separate multiple integer and fractional OAM modes occupying both copolarized and cross‐polarized output channels. The scheme is validated by a series of experimental demonstrations in the microwave regime. By adjusting the polarization states of both input and receiving ends, different integer and fractional OAM modes are demonstrated in the full transmission channels. The results offer a unique recipe to enhance information capacity of metasurfaces and trigger versatile electromagnetic (EM) wave function integrations for advanced compact systems. A variety of applications can be readily expected in spin‐selective optics, spin‐Hall metadevices, and multitask metasurfaces operating in both reflection and transmission modes.
Magnetic Schrödinger operators with delta‐type potentials
Authors: Rabinovich Vladimir
Published: November 2020

We consider the magnetic anisotropic Schrödinger operator on

where
is the vector potential of the magnetic field and W(x) is the scalar potential of the electric field. We assume that aj and ϱij are real‐valued functions belonging to the space
of bounded with first derivatives on
functions, whereas
is a complex‐valued electric potential. Let Σ  be a C2‐hypersurface in
dividing
on two open domains Ω± with common boundary Σ.  We assume that Σ  is a closed C2‐hypersurface or unbounded hypersurface of bounded geometry. We consider the magnetic Schrödinger operator  
with singular potentials Ws with supports on Σ. We associate with
an unbounded operator
in
generated by Hϱ,a, W with domain in H2(Ω+) ⊕ H2(Ω−) consisting of functions satisfying interaction conditions on Σ. We study the self‐adjointness of the operator
and its Fredholm properties. Moreover, we consider the spectral problem

and reduce this problem to a spectral problem for some boundary pseudodifferential operators on Σ. We describe the domains in
where problem (2) has the discrete spectrum.
Abnormal lung quantification in chest CT images of COVID‐19 patients with deep learning and its application to severity prediction
Authors: Shan Fei , Gao Yaozong , Wang Jun , Shi Weiya , Shi Nannan , Han Miaofei , Xue Zhong , Shen Dinggang , Shi Yuxin
Published: November 2020

Objective

Computed tomography (CT) provides rich diagnosis and severity information of COVID‐19 in clinical practice. However, there is no computerized tool to automatically delineate COVID‐19 infection regions in chest CT scans for quantitative assessment in advanced applications such as severity prediction. The aim of this study was to develop a deep learning (DL)‐based method for automatic segmentation and quantification of infection regions as well as the entire lungs from chest CT scans.

Methods

The DL‐based segmentation method employs the “VB‐Net” neural network to segment COVID‐19 infection regions in CT scans. The developed DL‐based segmentation system is trained by CT scans from 249 COVID‐19 patients, and further validated by CT scans from other 300 COVID‐19 patients. To accelerate the manual delineation of CT scans for training, a human‐involved‐model‐iterations (HIMI) strategy is also adopted to assist radiologists to refine automatic annotation of each training case. To evaluate the performance of the DL‐based segmentation system, three metrics, that is, Dice similarity coefficient, the differences of volume, and percentage of infection (POI), are calculated between automatic and manual segmentations on the validation set. Then, a clinical study on severity prediction is reported based on the quantitative infection assessment.

Results

The proposed DL‐based segmentation system yielded Dice similarity coefficients of 91.6% ± 10.0% between automatic and manual segmentations, and a mean POI estimation error of 0.3% for the whole lung on the validation dataset. Moreover, compared with the cases with fully manual delineation that often takes hours, the proposed HIMI training strategy can dramatically reduce the delineation time to 4 min after three iterations of model updating. Besides, the best accuracy of severity prediction was 73.4% ± 1.3% when the mass of infection (MOI) of multiple lung lobes and bronchopulmonary segments were used as features for severity prediction, indicating the potential clinical application of our quantification technique on severity prediction.

Conclusions

A DL‐based segmentation system has been developed to automatically segment and quantify infection regions in CT scans of COVID‐19 patients. Quantitative evaluation indicated high accuracy in automatic infection delineation and severity prediction.
Trends in prenatal diagnosis: An analysis of 40 years of Medical Subject Heading (MeSH) terms in publications
Authors: Lu Ya‐Ling , Bianchi Diana W.
Published: November 2020

Objective

To understand the evolution of the field of prenatal diagnosis over the past four decades.

Method

We analyzed the publications in the journal Prenatal Diagnosis from its inception in 1980 to 2019 using Medical Subject Headings (MeSH) to examine the major research topics and trends. The results were analyzed by 10‐year intervals.

Results

Publications on prenatal cytogenetics, congenital anomalies and fetal imaging predominated during the first three decades, with a steady increase in molecular genetics over time. Publications on NIPT did not appear until the most recent decade and are likely under‐counted because there was no MeSH term for NIPT until 2020.

Conclusion

The topics covered in Prenatal Diagnosis articles have evolved considerably over the past four decades and reflect a response to advances in technology and widespread incorporation of prenatal screening and diagnosis into standard obstetric care. The strengths of this analysis are its objective nature, its use of the standard MeSH terms used for coding, and application of a novel cluster analysis to visualize trends. The analysis also pointed out the fact that MeSH terms in this sub‐specialty area are often inconsistent due to manually coding based on individual subject matter expertise.
Advancing understanding of the classification of broad autism phenotype and attention‐deficit/hyperactivity disorder symptom dimensions within the Hierarchical Taxonomy of Psychopathology
Authors: Stanton Kasey , DeLucia Elizabeth A. , Brown Matthew F. D. , McDonnell Christina G.
Published: November 2020

Research on personality and psychopathology associations has informed the classification of many symptom dimensions within the Hierarchical Taxonomy of Psychopathology (HiTOP). However, classification of symptom dimensions defining autism and attention‐deficit/hyperactivity disorder (ADHD) within the HiTOP framework remains unclear in many ways. To address this issue, we examined the joint factor structure of (a) measures assessing characteristics relevant to ADHD and autism and (b) normal range personality traits in a sample of 547 adults recruited from Amazon Mechanical Turk, many of whom reported elevated autism‐relevant and ADHD‐relevant characteristics. We also examined how factors identified in these analyses correlated with measures of internalizing symptoms and select externalizing traits. Our results indicated that some measures assessing autism‐relevant and ADHD‐relevant characteristics (e.g. communication issues, hyperactivity/impulsivity) defined a distinct Attention and Communication Difficulties factor, with scores on this factor correlating strongly with internalizing symptom ratings. However, other relevant characteristics such as aloofness may be indicators of existing HiTOP spectra such as detachment. We discuss how these findings inform classification of autism‐relevant and ADHD‐relevant characteristics within the HiTOP, as well as key future directions for extending the limited research in this area.
Joint analysis of longitudinal measurements and survival times with a cure fraction based on partly linear mixed and semiparametric cure models
Authors: Yang Lu , Song Hui , Peng Yingwei , Tu Dongsheng
Published: November 2020

In a joint analysis of longitudinal quality of life (QoL) scores and relapse‐free survival (RFS) times from a clinical trial on early breast cancer conducted by the Canadian Cancer Trials Group, we observed a complicated trajectory of QoL scores and existence of long‐term survivors. Motivated by this observation, we proposed in this paper a flexible joint model for the longitudinal measurements and survival times. A partly linear mixed effect model is used to capture the complicated but smooth trajectory of longitudinal measurements and approximated by B‐splines and a semiparametric mixture cure model with the B‐spline baseline hazard to model survival times with a cure fraction. These two models are linked by shared random effects to explore the dependence between longitudinal measurements and survival times. A semiparametric inference procedure with an EM algorithm is proposed to estimate the parameters in the joint model. The performance of proposed procedures are evaluated by simulation studies and through the application to the analysis of data from the clinical trial which motivated this research.
Nonfragile sampled‐dataH∞control design for high‐speed train with parametric uncertainties
Authors: Subramanian K. , Muthukumar P. , Trinh Hieu
Published: November 2020

This study proposes the nonfragile sampled‐dataH∞control design for a high‐speed train (HST) with parametric uncertainties. Unlike the existing studies, the HST model is formulated together with the damping force, parametric uncertainties, and uncertain factors. To guarantee the desired tracking speed of HST, and at the equilibrium state, the stability of relative spring displacement between two adjacent carriages, sufficient conditions are addressed under nonfragile sampled‐dataH∞control based on the actual sampling pattern with an input delay approach. Meanwhile, aH∞disturbance attenuation performance is obtained for the uncertain factors, which ensures the safety and comfort of operating the HST. By utilizing experimental Japan Shinkansen HST parameter values, numerical examples are employed to verify the proposed method.
Separation and preparative purification ofl‐ andd‐valine ester: Diastereomeric conjugates of atazanavir using a combination of 2‐propanol and acetonitrile in reversed‐phase high‐performance liquid chromatography
Authors: Shyamsundar Murugesan , Chauthe Siddheshwar Kisan , Subramani Lakshumanan , Subbaiah Murugaiah A. M. , Gupta Anuradha , Bajpai Lakshmikant , Bagadi Muralidhararao , Mathur Arvind
Published: November 2020

The production of pure diastereomers and the quality control of chiral drug substances have become key issues for the pharmaceutical industry and regulatory agencies due to differences in their biological properties in vivo. This study discusses the unusual case study for analytical method development and preparative purification of diastereomers derived from the conjugation ofl‐ andd‐valine ester with the HIV‐1 protease inhibitor atazanavir prodrug. While thel‐valine ester conjugate diastereomers could be successfully separated using acetonitrile and 10 mM ammonium acetate on SunFire‐C18OBD column, the correspondingd‐valine ester conjugate diastereomers co‐eluted under the same method conditions. This observation led to a series of method development and optimization work that resulted in an improved chromatographic condition, using acetonitrile:2‐propanol (70:30) v/v combination as an organic modifier with 0.1% HCOOH on SunFire‐C18 column. The same method was further scaled up for isolation of individual diastereomers on preparative high‐performance liquid chromatography.
“Necklaces”: A Didactic Sequence for Missing-Value Proportionality Problems
Authors: Reséndiz Laura , Block Sevilla David
Published: November 2020

This research presents a sequence of didactic situations involving a proportionality relationship in which every value in a set (a number of necklaces) is mapped to a pair, a triad, or a quartet of values (numbers of blue beads, red beads, green beads, etc., required to make that number of necklaces) from another set. The sequence includes relatively simple multiplication and division problems, as well as more complex “missing-value” problems. This paper also presents the results of applying the sequence with a group of 4th grade students in a Mexican primary school (9 and 10 years old).
Taiwan: Performance in the Programme for International Student Assessment
Authors: Lin Su-Wei , Tzou Huey-Ing , Lu I-Chung , Hung Pi-Hsia
Published: November 2020

Taiwan has, from 2006, participated in five Programme for International Student Assessment (PISA) surveys. This chapter discusses Taiwan’s performance in PISA and its implications. At first, the education system and the process of educational reform in Taiwan were described. Then Taiwan’s performances for reading, math, and science in PISA were delineated. Taiwanese students have had consistently excellent performance for math and science; its reading performance, although not as outstanding as those for math and science, has improved significantly from 2009 to 2018. The gender gap in reading, in favour of female students, has narrowed, and the gender gap in math and science has been small. Educational equity, especially between rural and urban students, has also improved from 2006 to 2018. The proportion of high performers in reading and the proportion of low performers in reading, math, and science has increased from 2006 to 2018, while the proportions of top performers in math and science have decreased. These findings are interpreted from the perspectives of cultural beliefs, changes in the education system and national assessment, government investment in the related domains, and the nature of the PISA assessment.
Influence of Lattice Curvature and Nanoscale Mesoscopic Structural States on the Wear Resistance and Fatigue Life of Austenitic Steel
Authors: Panin Viktor E. , Egorushkin Valery E. , Surikova Natalya S.
Published: November 2020

The gauge dynamic theory of defects in a heterogeneous medium predicts the nonlinearity of plastic flow at low lattice curvatureand structural turbulence with the formation of individual dynamic rotations at high curvature of the deformed medium. The present work is devoted to the experimental verification of the theoretical predictions. Experimentally studied are the influence of high-temperature radial shear rolling and subsequent cold rolling on the internal structure of metastable Fe–Cr–Mn austenitic stainless steel, formation of nonequilibrium ε- and α′-martensite phases, appearance of dynamic rotations on fracture surfaces, fatigue life in alternating bending, and wear resistance of the material. Scratch testing reveals a strong increase in the damping effect in the formed hierarchical mesosubstructure. The latter is responsible for a nanocrystalline grain structure in the material, hcp ε martensite and bcc α′ martensite in grains, a vortical filamentary substructure on the fracture surface as well as for improved high-cycle fatigue and wear resistance of the material. This is related to a high concentration of nanoscale mesoscopic structural states, which arise in lattice curvature zones during high-temperature radial shear rolling combined with smooth-roll cold rolling. These effects are explained by the self-consistent mechanical behavior of hcp ε-martensite laths in fcc austenite grains and bcc α′-martensite laths that form during cold rolling of the steel subjected to high-temperature radial shear rolling.
Autowave Mechanics of Plastic Flow
Authors: Zuev Lev B.
Published: November 2020

The notions of plastic flow localization are reviewed here. It have been shown that each type of localized plasticity pattern corresponds to a given stage of deformation hardening. In the course of plastic flow development a changeover in the types of localization patterns occurs. The types of localization patterns are limited to a total of four pattern types. A correspondence has been set up between the emergent localization pattern and the respective flow stage. It is found that the localization patterns are manifestations of the autowave nature of plastic flow localization process, with each pattern type corresponding to a definite type of autowave. Propagation velocity, dispersion and grain size dependence of wavelength have been determined experimentally for the phase autowave. An elastic-plastic strain invariant has also been introduced to relate the elastic and plastic properties of the deforming medium. It is found that the autowave’s characteristics follow directly from the latter invariant. A hypothetic quasi-particle has been introduced which correlates with the localized plasticity autowave; the probable properties of the quasi-particle have been estimated. Taking the quasi-particle approach, the characteristics of the plastic flow localization process are considered herein.
Adhesion Hysteresis Due to Chemical Heterogeneity
Authors: Popov Valentin L.
Published: November 2020

According the JKR theory of adhesivecontact, changes of the contact configuration after formation of the adhesive neck and before detaching are completely reversible. This means, that after formation of the initial contact, the force-distance dependencies should coincide, independently of the direction of the process (indentation or pull-off). In the majority of real systems, this invariance is not observed. The reasons for this may be either plastic deformation in the contacting bodies or surface roughness. One further mechanism of irreversibility (and corresponding energy dissipation) may be chemical heterogeneity of the contact interface leading to the spatial dependence of the specific work of adhesion. In the present paper, this “chemical” mechanism is analyzed on a simple example of an axisymmetric contact (with axisymmetric heterogeneity). It is shown that in the asymptotic case of a “microscopic heterogeneity”, the system follows, during both indentation and pull-off, JKR curves, however, corresponding to different specific surface energies. After the turning point of the movement, the contact area first does not change and the transition from one JKR curve to the other occurs via a linear dependency of the force on indentation depth. The macroscopic behavior is not sensitive to the absolute and relative widths of the regions with different surface energy but depends mainly on the values of the specific surface energy.
Transfer of a Biological Fluid Through a Porous Wall of a Capillary
Authors: Nazarenko Nelli N. , Knyazeva Anna G.
Published: November 2020

The treatise proposes a model of biological fluid transfer in a dedicated macropore with microporous walls. The distribution of concentrations and velocity studies in the capillary wall for two flow regimes—convective and diffusive. The largest impact on the redistribution of concentration between the capillary volume and its porous wall is made by Darcy number and correlation of diffusion coefficients and concentration expansion. The velocity in the interface vicinity increases with rising pressure in the capillary volume or under decreasing porosity or without consideration of the concentration expansion.
A New Method for Seismically Safe Managing of Seismotectonic Deformations in Fault Zones
Authors: Ruzhich Valery V. , Shilko Evgeny V.
Published: November 2020

The authors outline the results of long-term interdisciplinary research aimed at identifying the possibility and the methods of controlling tangential displacements in seismically dangerous faults to reduce the seismic risk of potential earthquakes. The studies include full-scale physical and numerical modeling of P-T conditions in the earth’s crust contributing to the initiation of displacement in the stick-slip regime and associated seismic radiation. A cooperation of specialists in physical mesomechanics, seismogeology, geomechanics, and tribology made it possible to combine and generalize data on the mechanisms for the formation of the sources of dangerous earthquakes in the highly stressed segments of faults. We consider the prospect of man-caused actions on the deep horizons of fault zones using powerful shocks or vibrations in combination with injecting aqueous solutions through deep wells to manage the slip mode. We show that such actions contribute to a decrease in the coseismic slip velocity in the fault zone, and, therefore, cause a decrease in the amplitude and energy of seismic vibrations. In conclusion, we substantiate the efficiency of the use of combined impacts on potentially seismically hazardous segments of fault zones identified in the medium-term seismic prognosis. Finally, we discuss the importance of the full-scale validation of the proposed approach to managing the displacement regime in highly-stressed segments of fault zones. Validation should be based on large-scale tests involving advanced technologies for drilling deep multidirectional wells, injection of complex fluids, and localized vibrational or pulse impacts on deep horizons.
A Tool for Studying the Mechanical Behavior of the Bone–Endoprosthesis System Based on Multi-scale Simulation
Authors: Smolin Alexey Yu. , Eremina Galina M. , Shilko Evgeny V.
Published: November 2020

The chapter presents recent advances in developing numerical models for multiscale simulation of the femur–endoprosthesis system for the case of hip resurfacing arthroplasty. The models are based on the movable cellular automaton method, which is a representative of the discrete element approach in solid mechanics and allows correctly simulating mechanical behavior of a variety of elastoplastic materials including fracture and mass mixing. At the lowest scale, the model describes sliding friction between two rough surfaces of TiN coatings, which correspond to different parts of the friction pair of hip resurfacing endoprosthesis. At this scale, such parameters of the contacting surfaces as the thickness, roughness, and mechanical properties are considered explicitly. The next scale of the model corresponds to a resurfacing cap for the femur head rotating in the artificial acetabulum insert. Here, sliding friction is explicitly computed based on the effective coefficient of friction obtained at the previous scale. At the macroscale, the proximal part of the femur with a resurfacing cap is simulated at different loads. The bone is considered as a composite consisting of outer cortical and inner cancellous tissues, which are simulated within two approaches: the first implies their linear elastic behavior, the second considers these tissues as Boit’s poroelastic bodies. The later allows revealing the role of the interstitial biological fluid in the mechanical behavior of the bone. Based on the analysis of the obtained results, the plan for future works is proposed.
Material Transfer by Friction Stir Processing
Authors: Eliseev Alexander A. , Kalashnikova Tatiana A. , Filippov Andrey V. , Kolubaev Evgeny A.
Published: November 2020

Mechanical surface hardening processes have long been of interest to science and technology. Today, surface modification technologies have reached a new level. One of them is friction stir processing that refines the grain structure of the material to a submicrocrystalline state. Previously, the severe plastic deformation occurring during processing was mainly described from the standpoint of temperature and deformation, because the process is primarily thermomechanical. Modeling of friction stir welding and processing predicted well the heat generation in a quasi-liquid medium. However, the friction stir process takes place in the solid phase, and therefore the mass transfer issues remained unresolved. The present work develops the concept of adhesive-cohesive mass transfer during which the rotating tool entrains the material due to adhesion, builds up a transfer layer due to cohesion, and then leaves it behind. Thus, the transfer layer thickness is a clear criterion for the mass transfer effectiveness. Here we investigate the effect of the load on the transfer layer and analyze it from the viewpoint of the friction coefficient and heat generation. It is shown that the transfer layer thickness increases with increasing load, reaches a maximum, and then decreases. In so doing, the average moment on the tool and the temperature constantly grow, while the friction coefficient decreases. This means that the mass transfer cannot be fully described in terms of temperature and strain. The given load dependence of the transfer layer thickness is explained by an increase in the cohesion forces with increasing load, and then by a decrease in cohesion due to material overheating. The maximum transfer layer thickness is equal to the feed to rotation rate ratio and is observed at the axial load that causes a stress close to the yield point of the material. Additional plasticization of the material resulting from the acoustoplastic effect induced by ultrasonic treatment slightly reduces the transfer layer thickness, but has almost no effect on the moment, friction coefficient, and temperature. The surface roughness of the processed material is found to have a similar load dependence.
Einleitung und Überblick
Authors: Jeske Tim
Published: November 2020

Die Digitalisierung und ihre Potenziale für die Arbeitsgestaltung werden in diesem einleitenden Überblicksbeitrag kurz umrissen. Vor diesem Hintergrund werden der Förderschwerpunkt „Arbeit in der digitalisierten Welt“ und seine Begleitung durch das Projekt TransWork beschrieben. Die damit verbundene Strukturierung der insgesamt 29 begleiteten Projekte in Schwerpunktgruppen wird erläutert und die Schwerpunktgruppe „Produktivitätsmanagement“ näher dargestellt. Schließlich werden das vorliegende Werk und der handlungsleitende Aufbau der Beiträge aus der Schwerpunktgruppe beschrieben: vom praktischen Anwendungsbeispiel über ein schrittweises Vorgehen bis hin zu zentralen Ergebnissen und Lessons Learned.
Arbeit 4.0 in der Produktentstehung
Authors: Foullois Marc , Bansmann Michael , Mlekus Lisa , Paruzel Agnieszka , Bentler Dominik , Kato-Beiderwieden Anna-Lena , Jenderny Sascha , Seifert Lars
Published: November 2020

Digitale Technologien haben das Potential unser Leben und die Wertschöpfung nachhaltig zu verändern. Speziell in der Produktentstehung zeigt die Digitalisierung großes Nutzenpotential. Dies hängt unter anderem mit dem Zuwachs an Daten über den gesamten Produktlebenszyklus zusammen. Das Projekt IviPep (Instrumentarium zur Gestaltung individualisierter virtueller Produktentstehungsprozesse in der Industrie 4.0) hat das Ziel der menschengerechten Gestaltung der digitalen Arbeitswelt bei gleichzeitiger Effizienzsteigerung der Produktentstehung. In dem vorliegenden Beitrag wird, ausgehend von der Ausgangssituation (Innovation, steigende Anforderungen, demografischer Wandel), die Einführung digitalisierter Arbeit in der Produktentstehung beschreiben. Weiterführend werden die Erkenntnisse des Forschungsvorhabens beschrieben und mit den Lessons learned abgeschlossen.
Synchronisation von Digitalisierung, Qualitätssicherung und Assistenzsystemen an Arbeitsplätzen mit geringem Automatisierungsgrad
Authors: Rusch Tobias , Riegel Amelie , Hueber Michael , Kerber Florian , Merkel Lukas , Sochor Robin , Merhar Laura , Romanelli Massimo , Guo Zhenqiang , Klug Hermann , Stelzle Benedikt
Published: November 2020

Aufgrund variantenreicher Produktportfolios und steigender Kundenanforderungen im internationalen Wettbewerb stehen KMU vor besonderen Herausforderungen, die durch klassische Automatisierungstechnologien nicht zu lösen sind. Digital vernetzte Assistenzsysteme bieten die Möglichkeit, MitarbeiterInnen bei der Montage individueller Varianten kognitiv und physisch zu unterstützen. Im Projekt SynDiQuAss wurden auf Basis einer von den Partnern gemeinsam erarbeiteten und verabschiedeten Handlungsverpflichtung Methodiken und Technologien für den Einsatz an prototypischen Montagearbeitsplätzen entwickelt. Ziel des Projekts ist es, Produktqualität und Arbeitsproduktivität im Bereich der Montage in kleinen und mittelständischen Unternehmen durch Einsatz von Assistenzsystemen und Digitalisierungstechnologien zu verbessern. Während der Konzept- und Entwicklungsphasen wurden Akzeptanzuntersuchungen, Mitarbeiterbefragungen und Validierungsstudien durchgeführt, um die Qualität der Lösungsansätze zu beurteilen und die betroffenen MitarbeiterInnen am Transformationsprozess teilhaben zu lassen. Als finales Projektergebnis wurden zwei spezifizierte Montagearbeitsplätze zur prozessintegrierten robotergestützten Qualitätskontrolle und zur hybriden Getriebemontageassistenz aufgebaut und innerhalb der existierenden Produktionsstätten einem Praxistest unterzogen.
On the Jordan–Moore–Gibson–Thompson Wave Equation in Hereditary Fluids with Quadratic Gradient Nonlinearity
Authors: Nikolić Vanja , Said-Houari Belkacem
Published: November 2020

We prove global solvability of the third-order in time Jordan–More–Gibson–Thompson acoustic wave equation with memory in $${\mathbb {R}}^n$$

R

n

, where $$n \ge 3$$

n
≥
3

. This wave equation models ultrasonic propagation in relaxing hereditary fluids and incorporates both local and cumulative nonlinear effects. The proof of global existence is based on a sequence of high-order energy bounds that are uniform in time, and derived under the assumption of an exponentially decaying memory kernel and sufficiently small and regular initial data.
A homogeneous approach to testing for Granger non-causality in heterogeneous panels
Authors: Juodis Artūras , Karavias Yiannis , Sarafidis Vasilis
Published: November 2020

This paper develops a new method for testing for Granger non-causality in panel data models with large cross-sectional (N) and time series (T) dimensions. The method is valid in models with homogeneous or heterogeneous coefficients. The novelty of the proposed approach lies in the fact that under the null hypothesis, the Granger-causation parameters are all equal to zero, and thus they are homogeneous. Therefore, we put forward a pooled least-squares (fixed effects type) estimator for these parameters only. Pooling over cross sections guarantees that the estimator has a $$\sqrt{NT}$$

NT

convergence rate. In order to account for the well-known “Nickell bias”, the approach makes use of the well-known Split Panel Jackknife method. Subsequently, a Wald test is proposed, which is based on the bias-corrected estimator. Finite-sample evidence shows that the resulting approach performs well in a variety of settings and outperforms existing procedures. Using a panel data set of 350 U.S. banks observed during 56 quarters, we test for Granger non-causality between banks’ profitability and cost efficiency.
Latest Carboniferous to early Permian volcano-stratigraphic evolution in Central Europe: U–Pb CA–ID–TIMS ages of volcanic rocks in the Thuringian Forest Basin (Germany)
Authors: Lützner Harald , Tichomirowa Marion , Käßner Alexandra , Gaupp Reinhard
Published: November 2020

Mainly acidic Stephanian to early Permian volcanic rocks and intercalated sediments accumulated in the Thuringian Forest Basin (TFB) in central Germany to a total thickness of ca. 2000 m. This basin offers a wide range of biostratigraphic information. New high-precision U–Pb CA–ID–TIMS (chemical abrasion–isotope dilution–thermal ionization mass spectrometry) zircon data are obtained from volcanic rocks for the first time in the TFB. Pre-treatment of the zircons by chemical abrasion was important to get rid of severe Pb loss. The zircon ages of the investigated formations indicate that the total duration of the volcanic activity in the TFB was considerably shorter [ca. 4 Myr: from 300 Ma for the oldest formation (Möhrenbach) until ca. 296 Ma for the youngest volcanic-rock-bearing formation (Rotterode)] than suggested in previous studies (ca. 20 Myr; 295 Ma to 275 Ma). Consequently, the well-documented gap of the sedimentary record from the early Permian volcanic rocks up to the Illawarra geomagnetic reversal has to be extended to ca. 25 Myr from the previously proposed 5 Myr. The zircon ages of the investigated volcanic rocks allow the constraining of some intercalated fossiliferous horizons crucial for biostratigraphic correlation of latest Carboniferous–early Permian (Rotliegend) sections. The high-precision age data require a new interpretation of the evolution of the TFB but also offer the chance to obtain a more reliable comparison of the timing of the main magmatic activity across intramontane basins as well as to obtain links to the Standard Global Stratigraphic Scale.