bluuebunny/crossref_metadata_2025 huggingface dataset:
Research on Photodegradation of Norfloxacin by Modified Carbon Nitrogen Compounds
Authors: ENZI ZHAI
Published: January 2021

Photocatalysis is an economical and reliable method for degradation of pharmaceutical pollutants. Under mild conditions, the photocatalyst can absorb optical energy and accelerate the photo degradation of pollutants. As a new type of non-metallic semiconductor catalyst, graphite phase carbon nitride(g-C3N4) has many excellent properties such as low band gap, large specific surface area and so on. Norfloxacin (NOR) is a synthetic antibiotic with many good properties such as high antibacterial activity and low toxicity. Because of its wide application in medical treatment and animal breeding, it has caused great pollution to the environment. In this paper, the performance of g-C3N4 and the mechanism of photocatalytic degradation of NOR are analyzed. Several effective modification methods are described, and several problems that need to be solved in current research are put forward.
Nanofibril-mediated fracture resistance of bone
Authors: Tertuliano Ottman A , Edwards Bryce W , Meza Lucas R , Deshpande Vikram S , Greer Julia R
Published: January 2021

Natural hard composites like human bone possess a combination of strength and toughness that exceeds that of their constituents and of many engineered composites. This augmentation is attributed to their complex hierarchical structure, spanning multiple length scales; in bone, characteristic dimensions range from nanoscale fibrils to microscale lamellae to mesoscale osteons and macroscale organs. The mechanical properties of bone have been studied, with the understanding that the isolated microstructure at micro- and nano-scales gives rise to superior strength compared to that of whole tissue, and the tissue possesses an amplified toughness relative to that of its nanoscale constituents. Nanoscale toughening mechanisms of bone are not adequately understood at sample dimensions that allow for isolating salient microstructural features, because of the challenge of performing fracture experiments on small-sized samples. We developed an in situ three-point bend experimental methodology that probes site-specific fracture behavior of micron-sized specimens of hard material. Using this, we quantify crack initiation and growth toughness of human trabecular bone with sharp fatigue pre-cracks and blunt notches. Our findings indicate that bone with fatigue cracks is two times tougher than that with blunt cracks. In situ data-correlated electron microscopy videos reveal this behavior arises from crack-bridging by nanoscale fibril structure. The results reveal a transition between fibril-bridging (∼1 μm) and crack deflection/twist (∼500 μm) as a function of length-scale, and quantitatively demonstrate hierarchy-induced toughening in a complex material. This versatile approach enables quantifying the relationship between toughness and microstructure in various complex material systems and provides direct insight for designing biomimetic composites.
CEST MRI trackable nanoparticle drug delivery systems
Authors: Han Zheng , Liu Guanshu
Published: January 2021

Mounting evidence shows the great promise of nanoparticle drug delivery systems (nano-DDSs) to improve delivery efficiency and reduce off-target adverse effects. By tracking drug delivery and distribution, monitoring nanoparticle degradation and drug release, aiding and optimizing treatment planning, and directing the design of more robust nano-DDSs, image guidance has become a vital component of nanomedicine. Recently, chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) has emerged as an attempting imaging method for achieving image-guided drug delivery. One of the unbeatable advantages of CEST MRI is its ability to detect diamagnetic compounds that cannot be detected using conventional MRI methods, making a broad spectrum of bioorganic agents, natural compounds, even nano-carriers directly MRI detectable in a high-spatial-resolution manner. To date, CEST MRI has become a versatile and powerful imaging technology for non-invasive in vivo tracking of nanoparticles and their loaded drugs. In this review, we will provide a concise overview of different forms of recently developed, CEST MRI trackable nano-DDSs, including liposomes, polymeric nanoparticles, self-assembled drug-based nanoparticles, and carbon dots. The potential applications and future perspectives will also be discussed.
Supermultiplicative relations in models of interacting self-avoiding walks and polygons
Authors: Janse van Rensburg E J
Published: January 2021

Fekete’s lemma shows the existence of limits in subadditive sequences. This lemma, and generalisations of it, also have been used to prove the existence of thermodynamic limits in statistical mechanics. In this paper it is shown that the two variable supermultiplicative relation

p

n

1

(

m

1

)

p

n

2

(

m

2

)

⩽

p

n

1

+

n

2

(

m

1

+

m

2

)

together with mild assumptions, imply the existence of the limit

log

P

#

(

ϵ

)

=

lim

n
→
∞

1

n

log

p

n

(

⌊

ϵ
n

⌋

)

.

This is a generalisation of Fekete’s lemma. The existence of

log

P

#

(

ϵ

)

is proven for models of adsorbing walks and polygons, and for pulled polygons. In addition, numerical data are presented estimating the general shape of

log

P

#

(

ϵ

)

of models of square lattice self-avoiding walks and polygons.
Experimental characterisation of a flax fibre - epoxy resin composite
Authors: Artimon Flavia , Stochioiu C , Gheorghiu H M , Sima Iuliana
Published: January 2021

In the recent years, the scientific community’s attention has gradually started to focus in finding solutions for pollution control and replacement of non-biodegradable products with natural products. In this matter, composite materials with natural fibres are increasingly interesting for different research studies. The present work regards a flax fibre-epoxy resin composite material, which the response is studied under tensile tests until break and repeated loading/unloading cycles. An independent variable under study has been material fibre direction of 0°, 90° and ± 45°, for both types of tests. Samples were extracted from thermo-compression fabricated plates with dimensions following the ASTM D 3039 standard. The experimental setup included an MTS C45 105 Universal Testing Machine, with variable load cells, an extensometer, as well as digital image correlation equipment. The devices allowed the determination of stressstrain curves as well as material constants and Poison ratio. Results show, for the 90° and ± 45° typical responses for composites with these fibre directions, but a particular evolution, bilinear for the 0°.
Aspects of the wheel-switch contact studied with the CONTACT software
Authors: Tudorache M C , Dinu V M , Oprea R A
Published: January 2021

The rapid variation of the wheel and rail profile influences, on one hand, the grip-pseudo-slip - wear characteristics, and on the other hand, the dynamic behavior of the vehicle, because the pseudo-slip forces are significantly influenced by the contact area and pressures from within this area. It must be borne in mind that, in most cases, the rail-road has deviations from the geometric dimensions, which must not affect traffic safety and the demands of the running gear and the track must be within the permissible limits. Railway switches ensure discontinuities on the railway causing high dynamic loads. In operation, the rail-way devices must ensure three basic requirements: safety against derailment, stability while on the move and passenger comfort. In this context the paper presents aspects of the multipoint wheel-rail-way switch contact using the Contact software. Considering the influence of sliding speeds on the contact phenomena at the intersection of the wheel with the running path, the paper presents an analysis of the kinematic behavior of the axle while passing over a point rail.
Optimal selection of milling cutting tools for machining of triangular pockets
Authors: Belloufi A , Abdelkrim M , Rezgui I , Saci R , Mezoudj M , Amira M T
Published: January 2021

Minimizing machining time is an objective that must be taken into account when choosing the cutting tool. The diameter of the cutting tool is one of the parameters which greatly influences the machining time of different geometric shapes, especially pockets. In this study, a methodology for optimizing the choice of milling cutting tools for machining triangular pockets was proposed. An analytical model expressing the length of cutting tool paths has been optimized using sequential quadratic programming. the study carried out in this work leads to the conclusion that the spiral contour strategy makes it possible to have a minimum length for the machining of triangular shaped pockets.
Application of software solution for solving engineering design optimization problems
Authors: Madic M , Janković P , Trifunović M , Kovacević M
Published: January 2021

Engineering design problems involving a set of continuous, discrete and integer design variables and complex, non-convex objective functions and linear and non-linear constraints represent optimization problems with considerable complexity which are not trivial to solve. In recent years a number of optimization methods, particularly meta-heuristic optimization algorithms, were highlighted as effective optimization tools to deal with this type of engineering design problems. Despite certain advantages, their stochastic nature may be insufficient in dealing with various kinds of variables, constraints and objective functions. This paper discusses the application of developed software solution for solving engineering design optimization problems which is based on deterministic approach, i.e. the use of exhaustive iterative search algorithm. The use of the developed software solution is validated using four standard engineering design problems reported in the referential literature. In all case studies, the determined optimization solutions are equally good or better than those reported from other researchers using algorithms representative of the state-of-the-art in the area.
Analysis and development of a key performance indicators model for the paper industry
Authors: Tieber A , Manolache D , Gheorghe M
Published: January 2021

It is advisable to implement the use of key indicators by each company as a support for its continuous performant activity. Massive potential for optimisation can be found in the whole production industry. A scientific survey study has been designed and addressed to a number of companies from production industry in Europe. In the framework of this survey, the paper industry, as part of production industry, has been more profoundly analysed, in order to find the level of understanding and use of the key performance indicators and KPI systems, as an example. Based on the elements revealed by this analysis, a KPIs - Model for processes, production, financials, quality, supply chain, human resources and innovation is developed. This KPIs - Model can be a basis for the development of further KPIs - Models by any interested company, based on its specific conditions.
Comparative analysis of the reliability of electric locomotives based on semi-Markov models of restorable systems
Authors: Dyshin O A , Sh Pashayeva K , Aslanov C G
Published: January 2021

Based on the general theory of semi-Markov recovery processes and their application to Markov recovery processes, the applicability of stationary reliability indicators to assessing the reliability of electric locomotives with an asynchronous motor, the functioning of which is considered as a superposition of independent alternating semi-Markov processes, is shown. By calculating the main indicators of system reliability in a steady state, a comparative analysis of the operational reliability of electric locomotives with an asynchronous DC and AC motors, used respectively on the Azerbaijan and Kazakhstan railways, was carried out.
Prospects of introducing alternative sources of energy on Ukrainian railways
Authors: Panchenko V V , Masliy A S , Kharin R O
Published: January 2021

The potential of solar and wind energy was investigated, the existing premises of using the electric power obtained from non-conventional power sources of non-traction consumers for power supply of an electric traction system were analyzed. The influence of solar generation sources connected with the traction substation tires on the stability of non-traction consumers was determined. Possible options of connecting renewable energy sources to the railway power systems were examined. Calculations for determining the number of solar panels for compensating the auxiliary power consumption of the traction substation were made. The modeling of the possibility of implementing alternative energy sources in a traction substation in the PVsyst program was carried out. In Ukraine, the change of conditions for the provision of electricity supply services was caused by the rapid growth and development of renewable energy sources, in connection with which the number of suppliers increased. The question about the possibility of using alternative electricity sources to compensate the auxiliary power consumption of traction substations arises. Therefore, it is relevant to solve the problem of joint work of auxiliary power consumers together with non-traditional energy sources. The auxiliary power consumption of the traction substation include: heating drives and tanks of transformers; cooling down trip coils, relays, control panels, alarm systems, alarm and centralization and blocking devices; heating substation premises, store rooms and shower room. In order to implement alternative energy on the railway, it is necessary to analyze the auxiliary power consumption of the traction substation; to analyze the possibility of placing alternative power sources on the traction substation premises; to investigate how the powering system of the auxiliary power consumption of the traction substation can operate (both directly and in parallel mode).
Scientific approach to fire resistance calculation of reinforced concrete beams and columns
Authors: Fomin S L , Bondarenko Y V , Butenko S V , Koliesnikov S M
Published: January 2021

Problems related to the fire resistance calculation of reinforced concrete beams and columns from a scientific point of view when using new design standards are considered. The first problem is the insufficient development of improved calculation methods, exactly their absence. Only basic principles and requirements are formulated for them. This article presents the principles and sequence of calculation. The second problem is the lack of an accurate mathematical nonlinear compression model of the stress-strain diagram for concrete. The article explains the imperfection of the existing one, the need to create a new model and presents the basic requirements that such a mathematical model must meet. The third problem of the discussed ones is the erroneous values of the relative ultimate deformation of concrete. The principle of formation of values of relative limiting deformation of concrete is specified and proceeding from it the additional requirement for mathematical nonlinear model of compression of the diagram of stress - strain for concrete is specified.
Physicochemical studies of the structure of energy-saving compositions based on slags
Authors: Kostyuk Tetyana , Vinnichenko Varvara , Plugin rii , Borziak Olga , Iefimenko Artem
Published: January 2021

Blast furnace slags are subdivided into granular and dump. Granulated slag is widely used in the construction industry to production of Portland cement, Portland slag cement, slagalkaline cements, and concretes based on these cements. Dump slag is of less use, because it has low activity. The phase composition of granular and waste slag was investigated by methods of physicochemical analysis. The slags contain minerals that are present in Portland cement clinker. Concrete samples were made using granular, waste slag and sand. Unsatisfactory results in compressive and flexural strength were shown by a sample made of only two types of slag. The best strength results were obtained for a composition in which there are three components: granular slag, dump slag (filler) and sodium hydroxide. Electronic images have confirmed the appearance of low-basic calcium silicates, which provide the strength of the cementless composite. The resulting concrete composition is resource-saving, because made from production waste. And it can be called energy-saving, because no energy is expended to obtain components. The ecological feasibility of the production of such concrete is due to the absence of emissions of pollutants into the atmosphere (including carbon dioxide), since the firing of cement clinker is not needed.
Resource-saving steel hopper for loading of railway cars
Authors: Makhinko Anton , Makhinko Nataliia
Published: January 2021

The article is devoted to the study of geometric characteristics of corrugated sheets of railway grain hopper. In particular, the problem of finding the optimal parameters of a corrugated sheet of a given length, such as the height and width of the corrugation shelves, is solved. The optimality condition in this problem is determined by the minimum mass of the corrugated sheet. Because of analytical calculations, it was found that, regardless of the angle of tip of the corrugation wall, there will always be such a value of optimum height at which the corrugation area will be the smallest. For the analysis of this parameter, a series of curves of dependence of the corrugation cross-section area on the height for different angles of tip were constructed. The study also provided concise and engineering-friendly equations to determine the optimum height and width of corrugation shelves for wall angles up to 60º. These expressions can be applied to the case of corrugated sheet with a limited number of erection joints. For other cases of jointing of the corrugated sheets with each other (complete or partial overlapping of the lower part), additional studies should be performed similar to the procedure presented.
Management of the technical condition of hydraulic structures
Authors: Makovetsky B I , Sankov P M , Papirnyk R B , Tkach N O , Trifonov I V
Published: January 2021

In the process of operation of hydraulic structures it is needed to study these structures for their technical condition, which affects the durability and other structures operational properties. Some defects are impossible or difficult to examine. This is due to the lack of open access for visual inspection. Such defects are cavities formed under reinforced concrete slabs, which protect the dam from erosion. Timely detection and elimination of cavities during repairs extends the service life of dams. Scientifically confirmed methods are proposed, by means of which the problem of finding the location and the volume of cavities under reinforced concrete of ground dams, dams and other hydraulic structures is solved. The research proves that with using the natural pulsed electromagnetic field of the Earth geophysical method it is possible to interpret in terms of the cavities which occur during the inspection of the reinforced concrete fastening of the upper slope of the dams. The authors propose to determine the depth of anomalies by the color of the equal level of the natural pulsed electromagnetic field of the Earth, which corresponds to the depth of the cavities obtained by the method of geoelectric tomography.
General model and the mechanics of concrete elements and structures deformation
Authors: Romashko V M
Published: January 2021

The article presents a critical analysis of the model development of reinforced concrete elements and structures resistance by force influences. Their relationship with the defining provisions of the mechanics of reinforced concrete elements deformation was evaluated. The main disadvantages of the models considered are identified. A universal deformation and force model of deformation of reinforced concrete elements and structures is proposed, which is free of most of the disadvantageous characteristic of other models. The main advantage of the deformation-force model of resistance is indicated, due to the expansion of the known system of static, geometric and physical relationships to the level of statically definable. It becomes noticeable when calculating reinforced concrete elements and structures for deflection and crack resistance. This is one of the main features of the deformation-force model, which makes it possible to quite simply “embed” the technical theory of reinforcement to concrete adhesion into the general theory of reinforced concrete deformation. Due to the averaged design cross-section and the averaged materials deformations in the block between cracks, all parameters of cracks formation and propagation in the deformation-force model are directly related to the parameters of reinforcement to concrete adhesion.
Theoretical basis of bearing capacity calculation of the statically indeterminate reinforced concrete beams and its experimental research
Authors: Shkurupiy A A , Mytrofanov P B , Davydenko Yu O , Horb A G
Published: January 2021

New normative documents of Ukraine for the design of reinforced concrete and their elements contain a number of fundamentally new approaches to the calculation of their bearing capacity. Deformation model with an empirical criterion of durability is accepted as a basis of calculations of concrete and reinforced concrete elements on action of bending moments and longitudinal forces. Statically indeterminate reinforced concrete structures, in particular fixed beams, are widely used in various buildings and structures as load-bearing structures. Therefore, the research of their work and the direct calculation of such structures on the basis of the deformation model is a very important issue in the current trend of development of reinforced concrete both in our country and abroad. Theoretical calculations of bearing capacity of reinforced concrete continuous beams on the basis of deformation model with extreme strength criterion with the use of optimization and numerical methods and the limiting equilibrium method are performed. Their experimental studies are carried out. The results of theoretical calculations of such constructions are compared with experimental data obtained by the authors of the article and given in the works of other researchers.
Reinforcement of a deformed structure on the pile foundation
Authors: Vynnykov Yu L , Kharchenko M O , Manzhalii S M
Published: January 2021

The results of geomonitoring of the technical state of a five-storeyed building erected on driven prismatic piles are presented. The cause of excessive deformations of the foundation base is the inability of the pile tip to reach the design depth, which led to a significant reduction in their load-bearing capacity. The constructive technological solution of strengthening of the bases from piles as a part of a tape grid by bringing under existing grids of a monolithic reinforced concrete slab is improved. A new analytical model of the system “deformed building – driven prismatic piles as a part of a tape grid – soil base with a weak underlying layer” before and after supplying the slab under the existing foundation grids. The stress-strain state (SSS) of this system is estimated using the finite element method (FEM). New data of the change in the SSS system after supplying the slab under the existing grids were obtained. The results of the project execution (without resettlement of the residents of the house) and the respective geomonitoring are presented.
Justification of reference table data of dependence of wind effect on critical surface density heat flux for corrugated cardboard
Authors: Borysova A , Nizhnyk V , Ballo Ya , Kyrychenko O
Published: January 2021

To date, there is no statistical base of critical values of surface heat flux density for various substances and materials, in particular those that can be used in the decoration of buildings and technological installations. This article presents conclusions from the analysis of recent studies on this issue, substantiates the reference tabular data of the dependence of wind on the critical surface heat flux density for corrugated cardboard using a full-factor experiment. The authors determined the largest and smallest indicators of significant factors influencing the value of the critical surface heat flux density, namely wind speed (v, m/s) and the set surface heat flux density (q, kW/m2). In the course of the research, a mathematical model was constructed which describes the dependence of wind influence on the critical surface heat flux density for corrugated cardboard. These tables can be used in the future to develop an improved simplified method for predicting the thermal impact of fire on adjacent construction sites, taking into account the impact of wind.
Prediction of the life time of cylindrical tribosystems of a vehicle
Authors: Dykha A , Padgurskas J , Babak O
Published: January 2021

Development and research of methods for calculating the life of friction parts of a vehicle is an actual problem. Ball joints of a car suspension are one of the most responsible for reliability and safety friction unit of transport vehicles. In this paper the approaches to the computational and experimental assessment of the wear and reliability of the ball joint of a vehicle are proposed. The calculation of wear will be carried out based on the solution of the wear contact problem. The equilibrium condition, the wear law, and the geometric condition in the contact are taken as the basic equations. As a result, design formulas for wear and contact pressures have been proposed. A method for calculating the reliability function with determining the coefficients of variation of the wear parameters of ball joints is proposed. To assess the effectiveness of lubricants, a method for calculating wear parameters based on solving the inverse wear-contact problem is considered.
Influence of the flow area of distribution systems on changing the operating parameters of planetary hydraulic motors
Authors: Kiurchev S , Luzan P , Zasiadko A , Radionov H , Boltianska N
Published: January 2021

Predicting changes in the operating parameters of a planetary hydraulic motor is an urgent direction for improving its design. The physical and mathematical models of the planetary hydraulic motor have been developed, which make it possible to simulate the processes occurring under operating conditions. A design scheme and a mathematical apparatus have been developed for determining the pressure and leaks of the pressure fluid in the gap formed by the end surfaces of the distributors, which make it possible to study the change in the operating parameters of the hydraulic motor. By studying the features of the distribution system of a serial hydraulic motor, it was found that insignificant fluctuations in the flow area (up to 3%) cause rather large (up to 71%) pressure fluctuations. That causes the loss of fluid passing through the hydraulic motor up to 10% and fluctuations in the angular velocity of the output shaft – up to 11%. The absence of pressure fluctuations in the discharge line of the distribution system of the modernized hydraulic motor ensures the stability of its operating parameters. The results of the studies carried out make it possible to predict changes in the operating parameters of planetary hydraulic motors operating as part of a hydraulic drive at the design stage.
Conceptual Resource-Saving Design of Real-Time Socio-Technical Systems
Authors: Kosolapov Anatolii , Ivin Pavlo
Published: January 2021

The article discusses the methodological resource-saving approach to the System design of socio-technical systems for real-time managing (STS RTM). The definition of STS RTM from the point of view of computer systems architecture is introduced. This approach made it possible to classify the main paradigms of using computer systems, including the modern stage, corresponding to STS RTM. For such complex systems, it is important to ensure their energy efficiency, which is ensured by the use of resource-saving models and methods for optimizing structural solutions. This is ensured by minimizing the total length of communications at the enterprise, saving computing and financial resources during system migration from a centralized structure to a functionally distributed hierarchical multi-microcontroller system. STS is a human a real-time machine system, therefore, the system’s response time to the processing of requests related to the issuance of messages to the system’s operating personnel is determined. The complex of formulated tasks and their solution on a common information and analytical base is extremely difficult without a unified system design methodology and automation tools for solving problems. Such a Framework is described in this article.
Qualitative potentials of surface textures and coatings in the performance of fluid-film bearings: a critical review
Authors: Sharma Nitin , Verma Rajeev , Sharma Sumit , Kango Saurabh
Published: January 2021

The purpose of this article is to present the physical insights behind the successful implementation of surface textures and coatings in fluid film bearing systems for improving the tribological performance. The article is a systematic review of previously published articles implementing textures and coatings to know tribology behind it. The fluid rheology is also equally important for improving the performance of the bearing systems. The main focus is to know the reasons that have been quoted in numerous research studies for fruitfulness of texturing and coatings. It has come into the notice that a number of experimental studies incorporating textures were reported by the researchers; however, a huge amount of numerical/theoretical studies have been presented. The evolution in lubricants research appreciably used for improving the tribological performance by the reduction of friction and wear. The combination of textures and lubricants has proven the unambiguous enhancement in the rate of performance. The collection of information regarding physical causes behind the benefits of surface texture and coatings is the real worth of this article. The work on coatings of bearings have also becoming the interest of researchers and have profound effects in enhancing the tribological performance of slider bearings.
Microstructure, surface characteristics and properties of Ni–W composite coatings reinforced by nanoparticles fabricated by electrodeposition route
Authors: Zhang Weiwei , Fu Qiang , Shi Zhongquan , Ji Cuicui , Li Baosong , Chu Hongqiang
Published: January 2021

The effects of ZrO2, TiN, BN and Si3N4 nanoparticles on the microstructural, surface characteristics and properties of Ni-W composite coating have been comparatively studied in this paper. Their morphology, microstructure and characteristics were evaluated. Results illustrated that nanoparticles have been distributed in Ni-W composite coating, which could reinforce their properties. The surface topography was affected by the operating parameters. The formation of nodular protrusions could be attributed to the preferential discharge of the metal ions at the raised sites. The incorporation of nanoparticles could refine grains. The crystallite size of ZrO2, TiN, BN, and Si3N4 reinforced Ni-W composite coating were 13 ± 1, 13 ± 2, 12 ± 1 and 18 ± 1 nm, respectively. The roughness values (R
a) of ZrO2, TiN, BN and Si3N4 strengthened Ni-W composite coating is about 50 ± 2, 70 ± 4, 89 ± 11 and 25 ± 1 nm, respectively. The corrosion-resistant and anti-wear capability have been enhanced by incorporating nanoparticles into the Ni-W alloy matrix. The strengthening mechanisms of the nanocomposite coating were proposed. These nanocomposite coating exhibit potential application advantages as protective coating with high performance in harsh conditions.
Misalignment instability in magic-angle twisted bilayer graphene on hexagonal boron nitride
Authors: Lin Xianqing , Su Kelu , Ni Jun
Published: January 2021

We study the stability and electronic structure of magic-angle twisted bilayer graphene on the hexagonal boron nitride (TBG/BN). Structural relaxation has been performed for commensurate supercells of the heterostructures with different twist angles (

θ

′

) and stackings between TBG and BN. We find that the slightly misaligned configuration with

θ

′

=

0.54
∘

and the AA/AA stacking has the globally lowest total energy due to the constructive interference of the moiré interlayer potentials and thus the greatly enhanced relaxation in its 1 × 1 commensurate supercell. Gaps are opened at the Fermi level (E

F
) for small supercells with the stackings that enable strong breaking of the C
2 symmetry in the atomic structure of TBG. For large supercells with

θ

′

close to those of the 1 × 1 supercells, the broadened flat bands can still be resolved from the spectral functions. The

θ

′

=

0.54
∘

is also identified as a critical angle for the evolution of the electronic structure with

θ

′

, at which the energy range of the mini-bands around E

F
begins to become narrower with increasing

θ

′

and their gaps from the dispersive bands become wider. The discovered stablest TBG/BN with a finite

θ

′

of about 0.54∘ and its gapped flat bands agree with recent experimental observations.
Graphene Roadmap Briefs (No. 1): innovation interfaces of the Graphene Flagship
Authors: Döscher Henning , Reiss Thomas
Published: January 2021

Graphene and related materials (GRMs) promise ample impact on future industries. In the frame of the Graphene Flagship project, its technology and innovation roadmap (TIR) process explores pathways towards GRM industrialization. The initial issue of Graphene Roadmap Briefs outlines scope and goals of the novel format in the context the history, present status, and projected future of the TIR process. It particularly focusses the novel innovation interface investigation (3I) approach designed to explore the impact of GRM on the formation and transformation of potential future value chains. Context specific innovation spheres and their interrelations through innovation interfaces constitute the underlying key concepts of the 3I approach and serve as essential building blocks of prospective supply chains. The practical implementation of 3I studies bases on an extensive stakeholder consultation strategy to aggregate all relevant perspectives from key experts along a specific innovation chain. Each study culminates in an interactive 3I focus workshop to consolidate consensus expectations. An explorative innovation roadmap summarizes the joint vision for the innovation under investigation and outlines a realistic pathway for its implementation. We conclude with a coarse overview on earlier TIR results, on recent focus topics, and on the selection process that shape the current status and the future trajectory of the TIR process within and beyond the Graphene Flagship.

About: Graphene Roadmap Briefs

Graphene Roadmap Briefs highlight key innovation areas impacted by graphene and related 2D materials (GRMs) as well as overarching aspects of GRM innovation status and prospects. The series bases on the evolving technology and innovation roadmap process initiated by the European Graphene Flagship. It covers crucial innovation trends beyond fundamental scientific discovery and applied research on GRM utilization opportunities.
Graphene Roadmap Briefs (No. 2): industrialization status and prospects 2020
Authors: Döscher Henning , Schmaltz Thomas , Neef Christoph , Thielmann Axel , Reiss Thomas
Published: January 2021

The remarkable properties of graphene and related materials (GRMs) promise substantial benefits for a wide range of technologies. Their industrial utilization, however, critically depends on the availability of suitable GRM supply in terms of both quality and quantity at a competitive price. All factors remain highly specific to the each application scenario, while the emerging GRM supply industry still struggles to engage prospective clients in active development of GRM-enhanced products. The present issue of Graphene Roadmap Briefs compiles results on the status and prospects of GRM industrialization gathered by several innovation interface investigations (3I) that we conducted throughout the past 3 years. Each 3I study focussed a unique prospective value chain that GRM innovation promises to enable or advance in the future. While individual roadmaps mainly cover the peculiarities of the specific GRM supply chain under investigation, we combine all results regarding the primary material supply sector and it is rapidly evolving innovation context in Europe and beyond here. We introduce both the initial 2018 graphene industrialization roadmap and its thorough 2020 revision and extension. Our conclusions cover both crucial factors hampering the diffusion GRM today and opportunities to overcome these bottlenecks in the future.

About: Graphene Roadmap Briefs

Graphene Roadmap Briefs highlight key innovation areas impacted by graphene and related 2D materials (GRMs) as well as overarching aspects of GRM innovation status and prospects. The series bases on the evolving technology and innovation roadmap process initiated by the European Graphene Flagship. It covers crucial innovation trends beyond fundamental scientific discovery and applied research on GRM utilization opportunities.
Luminescent polyurethane composite with real-time thermal response via visible signal
Authors: Jin Yang , Shi Muyang , Zhu Yanan , Pang Zengyuan , Li Xiaoqiang , Ge Mingqiao
Published: January 2021

Visible signals are vital to human communication. Thermal signals are often difficult to observe unless they are in physical contact with the subject or an infrared thermal imaging system is used. In this study, we prepared a luminescent polyurethane composite (LPC), which can intelligently alter its colour and luminescence based on temperature. The LPC is fabricated from rare-earth luminescent materials (Sr2ZnSi2O7: Eu2+, Dy3+ and Y2O2S: Eu3+, Mg2+, Ti4+), a heat-sensitive rose-red TF-R1 thermochromic pigment (TP), polyurethane (PU), and polyester fabric. Microstructure and crystal structure analyses were carried out to determine the basic material properties of the LPC. The reflectivity and K S−1 value under different temperatures indicate that blue and green light were absorbed by LPC at 25 °C and the absorption decreased at 45 °C. This results in the LPC turning white. The emission spectra demonstrate that the quinoid structure of TP blocked the light of Sr2ZnSi2O7: Eu2+, Dy3+. Meanwhile, the lactone structure of TP allowed the light emission of Sr2ZnSi2O7: Eu2+, Dy3+ and Y2O2S: Eu3+, Mg2+, Ti4+. As a result, LPC emits red light at low temperatures and blue light at high temperatures. The advantage of the fabricated LPC is that the output can be easily manipulated into patterns. The uncured PU could form various graphics to cooperate with visible signals. Therefore, the LPC has significant potential as a functional material in smart clothing, flexible electronics, and wearable devices.
Improving flexural properties of polymethyl methacrylate denture filled by carbon nanofibers under low filling content
Authors: Dai Xinyu , Xu Zhimin , Li Zhengqiang , Sun Yidan , Zhang Shichen , Han Bing
Published: January 2021

In this article, we chose carbon nanofibers (CNFs) with high aspect ratio and excellent mechanical strength to investigate the evolution of the assemble behavior belong to the nanofillers and its effect on mechnaical properties of CNFs enhanced polymethyl methacrylate (PMMA) base denture resins. Test specimens were manufactured by mixing 0.5%, 1% and 3% content of CNFs with PMMA powder and the flexural properties of the specimens were tested by three-points testing. Comparing with the low flexural strength of pure PMMA base denture resins, Statistical evaluation results revealed that CNFs fillers highly improved the flexural strength of the composite resins to 66.44 ± 1.40 MPa, 68.75 ± 6.82 MPa and 89.26 ± 1.97 MPa at content reached 0.5%, 1% and 3%, respectively. Flexural modulus of neat PMMA was 2.79 ± 0.48 GPa, and the flexural modulus of the sample contains 0.5%, 1% and 3% reached 6.42 ± 0.75 GPa, 5.95 ± 0.29 GPa and 6.27 ± 0.14 GPa, respectively. Scanning electron microscopy revealed the aggregation of CNFs fillers, which is considered a stereoscopic framework that played the role of a special enhancing reinforcement under low filler content, and this strategy is considered to be expanded and developed to a common strategy that guiding our design in composite denture resins.
Enhanced mechanical strength of Cu–Sn alloy by Mg addition
Authors: Wu Tao , Yuan Dawei , Huang Hao , Wang Wenjing , Xiao Xiangpeng , Li Mingmao , Yang Bin
Published: January 2021

In recent years, the commercially available Cu–Sn alloy has attracted great interest within the new energy vehicles and industrial robots industries because of its relatively excellent comprehensive performance as compared to those of Cu–Ag and Cu–Mg alloys. In this work, we study the possibility of improving the tensile strength of Cu–Sn alloy via Mg addition. Our results show that, the addition of Mg could significantly improve the strength of the Cu–Sn alloy, the tensile strength of the Cu–Sn alloy was increased from 399MPa to 427MPa by 0.02 wt.% Mg addition after 80% cold-rolled reduction. This can be ascribed to the combined effect of the acceleration of the grain refinement and the promotion of the sub-structures formation by Mg addition during cold rolling process. Larger number density and more uniformly distributed sub–structures with an average size of 120 nm were formed in Mg-contained alloy than that in Mg-free alloy after 80% reduction. However, the Mg addition slightly decreased the electrical conductivity (EC) of the alloy (1.5%IACS), because of the lattice distortion caused by Mg atoms.
Investigation of the dynamic behaviour ceramic matrix composites obtained by additive technologies
Authors: Promakhov Vladimir , Vorozhtsov Alexander , Korobenkov Maxim , Schults Nikita , Bakhmat Vladislav , Dronov Filipp
Published: January 2021

Additive technologies open up new possibilities for creating materials with controlled structural features including ceramic composites. Such composites have good strength properties, fracture toughness and toughness. But not all properties are studied well. In order to predict the mechanical behavior of transformation-hardened ceramic composites with a controlled structure under dynamic loads, it is convenient to use methods of numerical analysis.The aim of this work was to investigate the influence of loading speed on microstructure evolution of ZTA nanocomposites obtained by additive tecnology of fused deposition modeling. Within the framework of the study physical and mathematical model that is used in computational mechanics of materials is developed. In the paper is shown the influence of the loading rate on the strain rate in the region of the shock transition for materials based on Al2O3 - 20%ZrO2 system. The research shows nonlinear effects under intense dynamic loads in the shown composite materials are bound up with either the processes of self-organisation of deformation modes at the mesoscopic level or the occurrence of martensitic phase transformations in matrix volumes adjacent to the strengthening particles.
Numerical simulation of laser-induced plasma in background gas considering multiple interaction processes
Authors: WANG Junxiao , ZHANG Lei , WANG Shuqing , SU Maogen , SUN Duixiong , HAN Jianghua , XIA Guofu , DONG Chenzhong , MIN Qi , MA Weiguang , DONG Lei , YIN Wangbao , XIAO Liantuan , JIA Suotang
Published: January 2021

Laser-induced plasma is often produced in the presence of background gas, which causes some new physical processes. In this work, a two-dimensional axisymmetric radiation fluid dynamics model is used to numerically simulate the expansion process of plasma under different pressures and gases, in which the multiple interaction processes of diffusion, viscosity and heat conduction between the laser ablated target vapor and the background gas are further considered, and the spatio-temporal evolutions of plasma parameters (species number density, expansion velocity, size and electron temperature) as well as the emission spectra are obtained. The consistency between the actual and simulated spectra of aluminum plasma in 1 atm argon verifies the correctness of the model and the numerical simulation, thus providing a refinement analysis method for the basic research of plasma expansion in gases and the application of laser-induced breakdown spectroscopy.
Recombinant major ampullate spidroin-particles as biotemplates for manganese carbonate mineralization
Authors: Neubauer Vanessa J , Kellner Christine , Gruen Viktoria , Schenk Anna S , Scheibel Thomas
Published: January 2021

Mineral deposition in biological systems is often templated by organic matrices including proteins directing the nucleation and growth of bioceramics by interacting with early stage species of the mineralization process or coordinating specific facets of the forming crystal. Structurally, charged surface patches are a characteristic motif of biomineralization-associated proteins, which are able to accumulate and bind ions from the surrounding media and, therefore, initiate, promote or inhibit mineralization. Controlled protein engineering enables the manipulation and control of bioinspired in vitro precipitation systems, and thus not only opens prospects for the design of environmentally benign synthetic strategies towards hierarchically structured functional materials, but also enhances the understanding of fundamental interaction mechanisms in biomineralization processes. Here, two recombinant variants of the spider silk protein ADF4 were engineered with oppositely charged peptide tags. Both were processed into micrometer-sized particles and investigated for their influence on manganese carbonate mineralization. Micro- and nano-structured manganese carbonate represents an attractive material for diverse applications including catalysis and wastewater treatment. While both types of spider silk particles were incorporated into the mineral structure, the positively tagged proteins appeared to interact more strongly with the formed manganese carbonate crystals than their negatively charged counterparts. Combination of the spider silk particles and poly(acrylic acid) (PAA), a water-soluble structure-directing agent associated with the stabilization of amorphous precursor phases in carbonates, resulted in the formation of film-like non-equilibrium structures of MnCO3 entrapping the spider silk particles. With the aim to gain mechanistic insights and to elucidate the interaction between the different components involved in the mineralization process, we studied the interplay between PAA, positively or negatively tagged spider silk particles, and Mn(II) ions by time-resolved dynamic light scattering. The here used set-up affords the possibility to identify control strategies for the template-mediated mineralization of manganese carbonate.