bluuebunny/crossref_metadata_2025_split huggingface dataset:
Computational Framework Concerning the Formulation of Maximum Work Principle used in Plasticity, Materials Forming and Tribology as a Consequence of a Variational Optimization Problem Defined From the Constructal Law
Authors: Gavrus Adinel 
Published: November 2020

Abstract
This research work proposes a fundamental application of the Constructal Theory developed by Prof. Adrian BEJAN of Duke University (USA) to prove on a mathematical point of view the “Principle” of Maximum Work, used by the theory of plasticity, material forming and tribology, as a consequence of the global solution defining a constrained variational optimization problem. According to the first and second law of thermodynamics, the principal law of Constructal Theory try to complete them with a quantitative prediction of the natural tendency of any finite size system to evolve towards an optimal space-time configuration minimizing the losses and the entropy generation simultaneously with a required maximum of the global entropy. In this sense, regarding a material plastic deformation characterising the forming processes, among all possible and admissible flow undergoing well-specified boundary conditions and loadings, the real one is the one who minimizes the sum of the dissipated power of volume deformation and surfaces friction. Thus, all the mechanical variables defining the real mechanical state (velocities, stresses, strain and strain rate) are those ones which minimize the total dissipated power. A variational minimization problem under a lot of defined constraints is then obtained. Using the Principle of Virtual Powers it can be shown finally that the “Principle” of Maximum Work, used particularly in metals plasticity, is obtained as a consequence of a minimization problem under constraints based on the Constructal Theory. This generalizes its application to any type of continuous media (metals, polymers, fluid, mushy state) and allows proving an equivalent form for the friction stresses occurring on contact interfaces. The convexity properties of both the plastic and the friction potential together with their normal rule properties can be also proven using the proposed mathematical framework. It is concluded that only the rheological and tribological flow laws associated with a potential become to satisfy the second thermodynamics principle completed with the Constructal Law. Analytical computations concerning plane and cylindrical crushing show the feasibility of the proposed minimization problem formulation to define material flow giving accurate approximate solutions. In order to valid the whole presented theory, comparisons are made using classical analyses based on the upper and lower bound theorems (obtained as consequences of the proposed optimization variational problem), the well-known slices method and a finite element modelling (FEM). A second application concerning the anisotropic formulation of a Coulomb friction law from a quadratic convex tribologic potential will be presented to define contact evolution during rectilinear sliding of a circular pion on a plane laminated thick plate surface along different orientations.
Numerical analysis of hydroforming process control using variable blankholder force
Authors: Paunoiu V , Maier C , Iacob I , Marinescu V 
Published: November 2020

Abstract
Hydroforming was developed to provide a cost effective means to produce relatively small quantities of drawn parts or parts with asymmetrical or irregular contours that are difficult to obtain by conventional stamping. This paper presents a study of hydroforming process with variable blankholder force in order to assure the parts quality. The main idea is to decompose the blankholder function of the elementary zone of the part contour corresponding to the linear and curvilinear zone. For each zone different blankholder force is applied in correlation with the hydrostatic pressure. A numerical analysis using finite element modelisation is performed considering different sets of blankholder forces and hydrostatic pressures, as process parameters. An optimum is determined in order to avoid parts defects (thickness reduction, wrinkles, fracture) for such types of parts.
Influence of some process input factors on the main dimensions of the grooves generated during the ball vibroburnishing
Authors: Nagit G , Dodun O , Slatineanu L , Ripanu M , Mihalache A , Hrituc A 
Published: November 2020

Abstract
The ball vibroburnishing is a processing method based on the plastic deformation of the workpiece surface layer, as a result of a vibration movement achieved by the ball pressed with a known force on the workpiece surface. The surface obtained by ball vibroburnishing includes grooves with different directions and partially overlapped. To know better the influence exerted by the ball vibroburnishing conditions on the main dimensional characteristics of the grooves, an experimental research was designed and materialized. As the process input factors, the diameter of the ball, the force, and the workpiece rotation speed were used. The depth and width of the groves generated by the moving balls on the workpiece surface layer were measured. By mathematical processing of the experimental results, empirical mathematical models were determined. These models highlight the intensity of the influence exerted by the ball vibroburnishing process input factors on the main dimensions of the grooves.
Experimental investigation and regression modelling to improve machinability in CNC turning of CALMAX® tool steel rods
Authors: Vaxevanidis N M , Fountas N A , Papantoniou I , Manolakos D E 
Published: November 2020

Abstract
This paper studies the effect of cutting conditions (spindle speed - rpm; feed rate - mm/rev and depth of cut - mm) on main cutting force and surface roughness during CNC turning of the commercial tool steel CALMAX® by Uddeholm (Sweden). Experiments have been designed using the Central composite design (CCD) approach. The experimental design involved twenty base runs with eight cube points, four center points in the cube, six axial points and two center points in axial direction. Statistical analysis to examine the effect of cutting conditions on the responses of main cutting force and surface roughness included ANOVA under the scope of generating a full quadratic model for predicting the responses. Finally, a feed-forward back-propagation neural network was applied to predict the responses of cutting force and surface roughness. It was found that regression models corresponding to the responses as well as the neural network developed can efficiently explain much of the variation in terms of main cutting force and surface roughness and thereby they may be implemented to practical applications either for predicting actual machinability parameter values or for setting up objective functions to be evaluated by intelligent algorithms for process optimization.
Influence of aluminium alloys relative positioning on dissimilar friction stir lap welds properties
Authors: Sabari S , Galvão I , Leitão C , Rodrigues D M 
Published: November 2020

Abstract
Very thin sheets of heat treatable (AA6082-T6) and non-heat treatable (AA5754-H22) aluminium alloys were used to produce dissimilar joints by friction stir lap welding. Joint strength and mechanical heterogeneity were assessed by performing lap tensile-shear and microhardness testing, respectively. Optical microscopy was used to analyse the weld morphology. Welding machine outputs, such as torque and axial force, were analysed in order to capture differences in the alloys strength during dissimilar welding. From the process outputs analysis, it was concluded that higher Z-Forces were necessary while positioning the AA5754 alloy at the top of lap configuration, indicating that this alloy offered higher resistance to the tool stirring than the AA6082 alloy. These results were associated with the flow softening of the AA6082 alloy during welding, which was explained using finite element analysis to illustrate the welding thermal cycles and the precipitation behaviour of this alloy. The lap welds defect formation was also related to the base materials plastic properties at high temperatures, which was inferred from process outputs data analysis. Based on the results it was shown that the lap welds defects might be supressed by a proper positioning the dissimilar base materials in the lap joint.
Using open source software CNC controllers and modular multi-axis mechanical structure as integrated teaching environment for CAD/CAM/CAE training
Authors: Breaz R E , Racz S G , Girjob C E , Tera M , Biriş C 
Published: November 2020

Abstract
Open source CNC controllers, such as Linux CNC are used more and more because they are open source projects and consequently are available for free. Moreover, these controllers are highly customizable, and their capabilities are close to the commercial solutions. The paper presents how using Linux CNC controller and a modular structure of a multi-axis CNC machine-tools, built by a commercial company, an integrated environment for training students in implementing CAM techniques was developed. Aside the CNC controller and the machine-tool, a CAM software package was used for programming complex machining operations. The kinematic model of the machine was built, for the user to be able to simulate, in a realistic way the multi-axes machining operations. The integrated teaching environment enable the users to be trained in CNC programming for three to five axes machining operations. Advanced programming strategies, such as tool center point management (TCPM) can also be tested.
Tribological Performance of Graphene and Graphene Oxide Films as Solid Lubricant Layers on Tool Steel Surfaces
Authors: Píška M , Sedlácek J , Foksová V , Sliwková P 
Published: November 2020

Abstract
Some high productive processes induce a use of effective cooling and lubricating for forming and cutting tools today. Apart of various fluids, foams, oils and emulsions with EP (extreme pressures) additives some very effective means based on graphene or graphene oxide show excellent performance in their solid phase. In this study, a very effective way to enhance the tribological performance of graphene layers on tool steel surfaces is studied. The solid lubricants based on graphene and graphene oxide flakes showed a very good thermal stability, low coefficient of friction and high wear resistance. However, some technological conditions and topographies of surfaces for their successful applications should be made in advance as prerequisites. The research work deals with a high productive forming of metals and improving the mechanical and functional properties of special products. It contributes to finding the optimal internal varnishes, testing their resistance to stress and chemical resistance to the components, understanding all relevant mechanical properties especially of graphene (friction properties, adhesion and abrasion resistance). This research and development is concerned with a production of thin walled products, which will provide future customers with a more durable and safe products and also would have better properties compared to similar products already available on the market.
A Python and Java software approach for 2.5 axes, self-adaptive stretch forming process and IoT solution
Authors: Grigoras C C , Chirita B , Brabie G 
Published: November 2020

Abstract
Stretch forming is a metal forming process that implies bending and stretching a sheet of metal over a die, with the sheet being plastically deformed into the desired shape. The purpose is to obtain large parts. One of the main aspects is that the metal sheet is locked into position by gripping jaws. A hydraulic ram is raised into the metal sheet, therefore increasing the tensile forces. This process is used to draw intro shape materials like aluminium, magnesium, titanium alloys, stainless steel, Inconel. These materials have in common the fact that they have poor formability or the elastic spring-back has unacceptable values. Taking this into consideration, the nature of the materials along with the fact that the metal sheet can crack, due to excessive strain, we propose a self-adaptive stretch forming process. Underlining this process is the stress-strain curve, that has three inputs: force, sample section area and strain. For each of these factors, our method uses a particular approach, as in a Python-based software and Android-based IoT solution, that uses stress and strain data. Furthermore, it controls, in real-time the hydraulic press to the point at which the material is stretch close to its ultimate yield strength.
Aging mechanism and surface properties of Silica fluoropolymer coating and its application
Authors: Huang Hongpu , Guo Hong , Qu Jia , Feng Yefeng 
Published: November 2020

Abstract
The hydrothermal aging cycles experiment was carried out on synthetic Silica fluoropolymer coating (SiO2-FP). The hydrothermal aging mechanism, surface properties and protective efficacy on sandstones was studied. For comparison, the same study was conducted for commercial protective material acrylic resin Paraloid B72 (PB72). The hydrothermal aging mechanism was studied by Fourier infrared spectroscopy attenuated total reflection technique (ATR-FTIR) and x-ray photoelectron spectroscopy (XPS) technology. The surface properties were characterized by field emission scanning electron microscope (SEM), the CR-400 color difference meter, static contact angle and GMT6503 Electronic universal Tensile machine. The capillary water absorption, water absorption by complete immersion (CI) and water vapor permeability were measured to evaluate the protective efficacy on sandstones after treatment. The results of ATR-FTIR and XPS indicated that part of the ester groups in PB72 was hydrolysed and the chemical structure of SiO2-FP was not changed but only microphase separation occurred after 360 h of aging. After 360 h of aging, the PB72 film had obvious change and the SiO2-FP film only shown a minor change; the color change of PB72 film was very obvious and the color change of SiO2-FP film was within the acceptable range; the PB72 film changed from hydrophobic to hydrophilic and the SiO2-FP film still retained high hydrophobicity (119.3°); the SiO2-FP had a higher adhesive strength than PB72 at the end of aging. Compared with PB72, the SiO2-FP can obviously reduce the capillary water absorption and had a higher protective efficiency (97.25%), much lower soakage capacity (0.60%), higher water vapor permeability (267.0 ± 2) and less influence on the water vapor permeability. All the results demonstrated that the SiO2-FP has much better anti-aging ability and longer durability under hydrothermal condition. The SiO2-FP can provide adequate protection for sandstones. The SiO2-FP can be used as a suitable protective coating on sandstones.
One-Loop order effects from one extra universal dimension on λϕ
4 theory
Authors: López-Osorio M A , Martínez-Pascual E , Nápoles-Cañedo G I , Toscano J J 
Published: November 2020

Abstract
The self-interacting λ
ϕ
4 scalar field theory is the prototype in the study of basic renormalisation issues in quantum field theories. In this paper we explore the one-loop order divergent impact to this theory from one universal extra dimension,

S

1

/

Z

2

, to the self-energy, four point vertex and the beta function. Such effects come as an infinite number of UV divergences corresponding to an infinite superposition of excited KK particles around the loop. We show that dimensional regularisation is adequate enough to control all of them in terms of the product of the one dimensional inhomogeneous Epstein zeta function times the gamma function. From the analytical properties of these functions, the UV divergences are extracted and the counterterms defined; the latter turn out to be of canonical dimension four at the Lagrangian level. We use both, the MS-scheme and a mass-dependent subtraction scheme to remove divergences. Only the latter manifestly satisfy the decoupling theorem.
Differential effects of land use on nutrient concentrations in streams of Pennsylvania
Authors: Clune John W , Crawford J Kent , Chappell William T , Boyer Elizabeth W 
Published: November 2020

Abstract
Nutrient pollution of surface waters is a widespread problem, calling for regional assessments of water quality conditions. In this study, we quantified long-term median nutrient concentrations of total nitrogen (TN) and total phosphorus (TP) in streams and rivers of Pennsylvania and explored relationships between stream nutrient concentrations and the land use of their watersheds. Our analysis is based on a synthesis of monitoring data from multiple agencies that included records of nutrient concentrations observed between 2000–2019. Across the state, stream nutrient concentrations observed in predominantly undeveloped areas (e.g., forests, shrubs, and grasslands) have median concentration values of 0.42 mg l−1 for TN and 0.011 mg l−1 for TP, reflecting background concentrations for minimally impacted watersheds. Median stream concentrations of TN in agricultural areas are about eleven times higher than in undeveloped areas; and are about five times higher in developed areas than in undeveloped areas. Median stream concentrations of TP in developed areas have about eight times higher concentrations than undeveloped areas; and are about four times higher in agricultural areas than in undeveloped areas. Concentrations of TN and TP increased substantially as the combined percentage of agricultural and developed land use increased. Fragmented data storage practices (e.g. incomplete metadata, ambiguous site names, and missing coordinates) and inconsistencies in monitoring protocols (e.g., differences in constituents measured, parameter names, and measurement methods) made leveraging the secondary use of multiple sources of data challenging. Nonetheless, our integrated dataset is robust, represents the best data available, and provides a new window into the nutrient status of Pennsylvania’s surface waters. The long-term median nutrient concentrations reveal the magnitude of variability in TN and TP concentrations across the state’s diverse environmental settings of land use, physiography, and geology. This information is useful for interpreting additional monitoring data, informing evaluation of water quality conditions, and guiding watershed management.
Extended connectivity interaction features: improving binding affinity prediction through chemical description
Authors: Sánchez-Cruz Norberto , Medina-Franco José L , Mestres Jordi , Barril Xavier 
Published: November 2020

AbstractMotivationMachine-learning scoring functions (SFs) have been found to outperform standard SFs for binding affinity prediction of protein–ligand complexes. A plethora of reports focus on the implementation of increasingly complex algorithms, while the chemical description of the system has not been fully exploited.ResultsHerein, we introduce Extended Connectivity Interaction Features (ECIF) to describe protein–ligand complexes and build machine-learning SFs with improved predictions of binding affinity. ECIF are a set of protein−ligand atom-type pair counts that take into account each atom’s connectivity to describe it and thus define the pair types. ECIF were used to build different machine-learning models to predict protein–ligand affinities (pKd/pKi). The models were evaluated in terms of ‘scoring power’ on the Comparative Assessment of Scoring Functions 2016. The best models built on ECIF achieved Pearson correlation coefficients of 0.857 when used on its own, and 0.866 when used in combination with ligand descriptors, demonstrating ECIF descriptive power.Availability and implementationData and code to reproduce all the results are freely available at https://github.com/DIFACQUIM/ECIF.Supplementary informationSupplementary data are available at Bioinformatics online.
The Carceral City: Confinement and Order in Hong Kong’s Forbidden Enclave
Authors: Fraser Alistair , Schliehe Anna 
Published: November 2020

Abstract
Once feted, Hong Kong has recently become a centre of civil unrest. In this paper, we situate these emergent politics through a case study of corruption and everyday life in Kowloon Walled City, a mainland Chinese enclave in British Hong Kong, which developed notoriety as a freestanding grey economy. Drawing from oral testimonies of police officers, triad members and local residents, we excavate the lived experience of confinement within this contested space. These accounts reconstruct the Walled City as a ‘quasi-carceral’ site of enclosure, a zone of colonial exceptionalism and a hybrid cultural space. Through this case study, we historicize current debates in carceral geography, humanize recent interventions in urban scholarship and analyse the shifting politics at the frontier of Chinese expansionism.
Social Workers during COVID-19: Do Coping Strategies Differentially Mediate the Relationship between Job Demand and Psychological Distress?
Authors: Ben-Ezra Menachem , Hamama-Raz Yaira 
Published: November 2020

Abstract
The consequences of the coronavirus disease of 2019 (COVID-19) pandemic have raised many challenges in the social services workforce. The current study aimed to examine the associations between job demands, coping strategies (i.e. emotion-focused coping and problem-focused coping) and psychological distress exhibited by social workers during the COVID-19 pandemic. In addition, the mediating role of different coping strategies was investigated for the associations revealed. The participants were 615 social workers, working in various organisations and with diverse populations in Israel. Each completed a validated self-report questionnaire. Results revealed that job demands were significantly associated with higher psychological distress, and that coping strategies, especially emotion-focused coping was associated with higher psychological distress and with job demands. In addition, emotion-focused coping strategies were found to mediate the association between job demands and psychological distress, especially ventilation of emotion beyond other strategies, which relate to emotion-focused coping. These findings are discussed with relation to a stress and coping theory, suggesting that in social work practice there is a need for intervention measures to improve social workers’ coping strategies during crises such as the COVID-19 pandemic.