Beatriz Martín-García, Anatolii Polovitsyn, Mirko Prato
et al.
Quantum dot - graphene hybrid materials have raised significant interest due to the unique synergy of the optical properties of colloidal quantum dots (QDs) and the transport properties of graphene. This stimulated the development of low-cost and up-scalable solution-processed strategies for hybrid materials with potential application in light harvesting and opto-electronic devices. Here we report a versatile covalent-linking based approach for the functionalization of reduced graphene oxide (rGO), to prepare a variety of QD-rGO hybrid dispersions with QDs of different size and composition (PbS, PbS/CdS and CdSe QDs), and shape (CdSe/CdS dot-in-rods). We achieved a well-controlled QD coverage of the rGO sheets by functionalizing the rGO surface with mercapto-silane linkers. A further spectroscopic investigation of near-infrared PbS QD-rGO materials demonstrates efficient electronic coupling between both materials. The QD photoluminescence emission quenching and exciton lifetime shortening up to 95%, together with subtle graphene Raman G-band shifts upon QD linking, supports electron transfer as the dominant relaxation pathway from the QD to the rGO. The use of core/shell PbS/CdS QDs allows tuning of the transfer efficiency from 94% for a 0.2 nm thin CdS shell, down to 30% for a 1.1 nm thick shell.
The microstructure and thin-walled effect of different samples （double-wall ultra-cooling turbine blades， combined cooling turbine blades， investment casting thin-walled specimen， and round bar specimen） of the third-generation single crystal superalloy DD9 are investigated by optical microscope， field emission scanning electron microscope， and electron probe apparatus. The results show that there are differences in the microstructures of the four specimens. When the section sizes are the same， the as-cast primary dendrite arm spacing， the sizes of γ′ phases， and the dendrite segregation of the as-cast and heat- treated specimens of DD9 single crystal turbine blades are all larger than those of the investment casting thin-walled specimens. After full heat treatment， the sizes of the γ′ phases of single crystal turbine blades with the same cross-sectional size are similar to those of investment casting thin-walled specimens. The as-cast primary dendrite arm spacing， the sizes of γ′ phases， and the dendrite segregation of the as-cast and heat-treated thin-walled specimens of DD9 alloy all decrease with the decrease of the cross-sectional size.
Materials of engineering and construction. Mechanics of materials
In order to improve the operation control performance of high-speed maglev trains, an improved finite-time rotor magnetic Field-Oriented Control method was proposed in this paper. Aiming at the stator current control problem of long-stator linear synchronous motors under parametric perturbation, this paper investigates the double-feeding mode, combines the predefined-time stability theory and designs an improved sliding mode controller to optimise the dynamic characteristics of the inner-loop system. In the outer-loop cruise control, the predefined-time sliding mode control is combined with a finite-time disturbance observer, which effectively solves the problems of inaccurate modelling and parameter ingestion. It was verified through simulation and analysis that the control strategy has significant advantages in improving the dynamic tracking performance and anti-interference ability, with the stator current stabilisation time within 0.1 s, the absolute value of the fluctuation error within 20 A, the outer-loop response time within 0.5 s, the maximum speed error within 0.0005 m/s and the maximum displacement error within 0.0005 m. The control strategy has the advantages of improving the dynamic tracking performance and anti-interference ability.
Materials of engineering and construction. Mechanics of materials, Production of electric energy or power. Powerplants. Central stations
Magnesium potassium phosphate cement (MKPC) is one of chemical bonded ceramic material that has more prominent advantages including fast-setting compared to Ordinary Portland Cement. In recent years, although there have been some studies on MKPC and its admixtures, the effects of individual admixture on MKPC have not been well understood. In this paper, the mechanical properties and microstructure of MKPC with mineral admixtures including fly ash (FA), silica fume (SF) and steel slag (SSP) were investigated and compared. Mechanical properties were analyzed by carrying out flexural strength and compressive strength tests. The hydration products and microstructure of MKPC samples with and without mineral admixtures were investigated using X-ray diffraction, energy dispersive X-ray spectrometry, scanning electron microscopy and adsorption isotherm. Based on the test results, it was shown that the optimum addition of FA, SF and SSP additives were found to be 30 %, 20 % and 5 %, respectively. Compared to MKPC without admixture, the flexural strength of MKPC incorporating FA, SF and SSP can be enhanced by 28 %, 40 % and 17.3 %, respectively, while the compressive strength can be improved by 43.4 %, 52.6 % and 6.7 %, respectively. Hence, it can be concluded that the SF has the largest effects on the compressive strength of MKPC, while the effects of SSP is the smallest.
Materials of engineering and construction. Mechanics of materials
The ramp-reversal memory (RRM) effect in metal-insulator transition metal oxides (TMOs), a non-volatile resistance change induced by repeated temperature cycling, has attracted considerable interest in neuromorphic computing and non-volatile memory devices. Our previously introduced defect motion model successfully explained RRM in vanadium dioxide (VO$_2$), capturing observed critical temperature shifts and memory accumulation throughout the sample. However, this approach lacked interactions between metallic and insulating domains, whereas the RRM only appears when TMOs are brought into the metal-insulator coexistence regime. Here, we extend our model by combining the Random Field Ising Model with defect diffusion-segregation, thereby enabling accurate hysteresis modeling while predicting the relationship between RRM and domain interactions. Our simulations demonstrate that maximum RRM occurs when the turnaround temperature approaches the warming branch inflection point, consistent with experimental observations on VO$_2$. Most significantly, we find that increasing nearest-neighbor interactions enhances the maximum memory effect, thus providing a clear mechanism for optimizing RRM performance. Since our model employs minimal assumptions, we predict that RRM should be a widespread phenomenon in materials exhibiting patterned phase coexistence of electronic domains. This work not only advances fundamental understanding of memory behavior in TMOs but also establishes a much-needed theoretical framework for optimizing device applications.
The magnetoelectric (ME) effect is a fundamental concept in modern condensed matter physics and represents the electrical control of magnetic polarisations or vice versa. Two-dimensional (2D) van-der-Waals (vdW) magnets have emerged as a new class of materials and exhibit novel ME effects with diverse manifestations. This review emphasizes some important recent discoveries unique to vdW magnets: multiferroicity on two dimensions, spin-charge correlation, atomic ME effect and current-induced intrinsic spin-orbit torque, and electrical gating control and magnetic control of their electronic properties. We also highlight the promising route of utilizing quantum magnetic hetero- or homo-structures to engineer the ME effect and corresponding spintronic and optoelectronic device applications. Due to the intrinsic two-dimensionality, vdW magnets with those ME effects are expected to form a new, exciting research direction.
The current strategy of co-delivering copper ions and disulfiram (DSF) to generate cytotoxic CuET faces limitations in achieving rapid and substantial CuET production, specifically in tumor lesions. To overcome this challenge, we introduce a novel burst-release cascade reactor composed of phase change materials (PCMs) encapsulating ultrasmall Cu2-xSe nanoparticles (NPs) and DSF (DSF/Cu2-xSe@PCM). Once triggered by second near-infrared (NIR-II) light irradiation, the reactor swiftly releases Cu2-xSe NPs and DSF, enabling catalytic reactions that lead to the rapid and massive production of Cu2-xSe-ET complexes, thereby achieving in situ chemotherapy. The mechanism of the burst reaction is due to the unique properties of ultrasmall Cu2-xSe NPs, including their small size, multiple defects, and high surface activity. These characteristics allow DSF to be directly reduced and chelated on the surface defect sites of Cu2-xSe, forming Cu2-xSe-ET complexes without the need for copper ion release. Additionally, Cu2-xSe-ET has demonstrated a similar (to CuET) anti-tumor activity through increased autophagy, but with even greater potency due to its unique two-dimensional-like structure. The light-triggered cascade of interlocking reactions, coupled with in situ explosive generation of tumor-suppressive substances mediated by the size and valence of Cu2-xSe, presents a promising approach for the development of innovative nanoplatforms in the field of precise tumor chemotherapy.
Materials of engineering and construction. Mechanics of materials, Biology (General)
Melamine-coated medium density fibreboard (MDF-LAM) is widely used in the construction industry, furniture industry and other structural applications due to its easy processing, low cost, high strength and high dimensional stability. In this study, the effects of MDF on the environment throughout its life cycle were determined by the Life Cycle Assessment (LCA) method. For this purpose, it presents the results of a research conducted to evaluate the environmental impacts and identify hot spots of MDF-LAM production in Türkiye using the LCA method, considering a cradle-to-gate system. The MDF-LAM production process is studied in four subsystems: fibre preparation, board forming, finishing and lamination (LAM). In the analysis of the environmental effects of MDF-LAM, detailed data were obtained from a company producing in Türkiye. In this study, the functional unit is “1 m3 MDF-LAM production in Türkiye”. The environmental impacts of MDF-LAM were estimated in SimaPro 9.1 software using the Ecoinvent database v3.5 with CML-IA impact assessment and Cumulative Energy Demand (CED) methods. Various impact categories were considered in the analysis, such as global warming, acidification, eutrophication, water use, fossil fuels, human toxicity and cumulative energy demand. The analysis results show that the fiber preparation stage is the main hotspot in terms of environmental impacts and emissions. And shows that this is followed by the lamination step. It has been determined that urea formaldehyde (UF) resin, which is used as a synthetic adhesive, has the largest share in the environmental effects of MDF-LAM production. In this study, CED was evaluated as another impact category. This evaluation result showed that the fiber preparation subsystem had a higher CED than the other stages. In addition, it was determined that renewable biomass and non-renewable fossil were the most affected categories, while UF resin use and electricity consumption were the most important hot spots in terms of non-renewable and renewable resources.
Materials of engineering and construction. Mechanics of materials
Mbanwei Divine Kobbi, Njimboh Henry Alombah, Ngwa Martin Ngwabie
Electric vehicles have advantages such as reduced maintenance and fuel costs compared to internal combustion engines. However, their limited driving range still hinders their widespread adoption compared to internal combustion engines. Harvesting wasted energies through vibrations in electric vehicles is a good approach to complement the energy of their batteries. Space constraints in electric vehicles require devices with high power output per unit volume. This study aimed to design a novel vibration energy harvesting using the geometrical model for electric vehicles. Different configurations and their performance in maximum flux linkage, electromagnetic coupling coefficient, induced voltage, and generated power were investigated. The modeling, excitement, and analysis were conducted using ANSYS Maxwell software with four configurations under similar conditions. These were the Halbach array with three magnets, one coil, and flat back shield; the Halbach array with three magnets and one coil with a stepped back shield; the double magnet array with two magnets, one coil, and flat back shield; and the fourth one was a double magnet array with two magnets, one coil and stepped back shield. The MATLAB Simulink software was used to obtain further results and power output analysis. The results of the analysis show that the Halbach array with three magnets, one coil, and a stepped-back shield is the best configuration for harvesting energy from vibrations, producing an electromagnetic coupling coefficient of up to 110 Wb/m, a voltage of up to 36 V, and generated power density of 0.13 W/cm. A reasonable increase in output using less volume was obtained compared to the other studies. The energy harvested will be applied in future studies to extend the range of agricultural electric vehicles, reducing farmers’ income spent on fuel and maintenance.
Materials of engineering and construction. Mechanics of materials, Mechanical engineering and machinery
The traditional von Neumann architecture is gradually failing to meet the urgent need for highly parallel computing, high-efficiency, and ultra-low power consumption for the current explosion of data. Brain-inspired neuromorphic computing can break the inherent limitations of traditional computers. Neuromorphic devices are the key hardware units of neuromorphic chips to implement the intelligent computing. In recent years, the development of optogenetics and photosensitive materials has provided new avenues for the research of neuromorphic devices. The emerging optoelectronic neuromorphic devices have received a lot of attentions because they have shown great potential in the field of visual bionics. In this paper, we summarize the latest visual bionic applications of optoelectronic synaptic memristors and transistors based on different photosensitive materials. The basic principle of bio-vision formation is first introduced. Then the device structures and operating mechanisms of optoelectronic memristors and transistors are discussed. Most importantly, the recent progresses of optoelectronic synaptic devices based on various photosensitive materials in the fields of visual perception are described. Finally, the problems and challenges of optoelectronic neuromorphic devices are summarized, and the future development of visual bionics is also proposed.
Materials of engineering and construction. Mechanics of materials, Biotechnology
Yeong-Min Kim, Phat Tien Nguyen, Tam Minh Phan
et al.
The objective of this study was to identify the most effective chip seal design method and chip sizes by conducting a modified Hamburg wheel tracking test and sweep test. Three chip seal design methods, including Austroads, McLeod, and Vietnam methods, were evaluated to design several chip seal mixtures with varying aggregate sizes (e.g., 12.5, 9.5, 4.75, and 2.36 mm) and binder types. To assess the performance of the chip seal mixtures, aggregate loss and bleeding susceptibility were measured. The sweep test was utilized to determine the amount of aggregate loss caused by the sweeping effect, while the modified Hamburg wheel tracking (HWT) test was developed to estimate the aggregate loss caused by the braking effect using a fixed pneumatic rubber tire. Additionally, a modified Hamburg wheel tracking test with a rolling pneumatic rubber tire was used to assess bleeding susceptibility, and the bleeding area was quantified using an image analysis process. The results indicated that the Austroads design method exhibited the lowest aggregate loss compared to the McLeod and Vietnam methods. Moreover, the consistent findings from both the sweep test and modified HWT test demonstrated the feasibility of using the modified HWT test to simulate aggregate loss caused by the braking effect. The bleeding percentage was found to be affected not only by the binder application rate but also by the aggregate size and the number of layers applied. The Austroads and McLeod chip seal mixtures exhibited an approximately 20 % lower bleeding percentage than that of the Vietnam mixtures. Finally, for a single chip seal, a 9.5 mm chip aggregate was determined to be the optimal size, while for a double chip seal, 4.75 mm and 2.36 mm chips were recommended.
Materials of engineering and construction. Mechanics of materials
NIMS-OS (NIMS Orchestration System) is a Python library created to realize a closed loop of robotic experiments and artificial intelligence (AI) without human intervention for automated materials exploration. It uses various combinations of modules to operate autonomously. Each module acts as an AI for materials exploration or a controller for a robotic experiments. As AI techniques, Bayesian optimization (PHYSBO), boundless objective-free exploration (BLOX), phase diagram construction (PDC), and random exploration (RE) methods can be used. Moreover, a system called NIMS automated robotic electrochemical experiments (NAREE) is available as a set of robotic experimental equipment. Visualization tools for the results are also included, which allows users to check the optimization results in real time. Newly created modules for AI and robotic experiments can be added easily to extend the functionality of the system. In addition, we developed a GUI application to control NIMS-OS.To demonstrate the operation of NIMS-OS, we consider an automated exploration for new electrolytes. NIMS-OS is available at https://github.com/nimsos-dev/nimsos.
The need for faster and more miniaturised electronics is challenging scientists to develop novel forms of electronics based on quantum degrees of freedom different from electron charge. In this fast-developing field, often referred to as quantum electronics, the metal-oxide perovskite SrRuO3 can play an important role thanks to its diverse physical properties, which have been intensively investigated, mostly for conventional electronics. In addition to being chemically stable, easy to fabricate with high quality and to grow epitaxially onto many oxides - these are all desirable properties also for conventional electronics - SrRuO3 has interesting properties for quantum electronics like itinerant ferromagnetism and metallic behaviour, strong correlation between magnetic anisotropy and spin-orbit coupling, strain-tuneable magnetisation, anomalous Hall and Berry effects. In this Research Update, after describing the main phenomena emerging from the interplay between spin, orbital, lattice and topological quantum degrees of freedom in SrRuO3, we discuss the challenges still open to achieve control over these phenomena. We then provide our perspectives on the most promising applications of SrRuO3 for devices for conventional and quantum electronics. We suggest new device configurations and discuss the materials challenges for their realisation. For conventional electronics, we single out applications where SrRuO3 devices can bring competitive advantages over existing ones. For quantum electronics, we propose devices that can help gain a deeper understanding of quantum effects in SrRuO3 to exploit them for quantum technologies. We finally give an outlook about properties of SrRuO3 still waiting for discovery and applications that may stem from them.
Chalcogenide phase-change materials (PCMs) are widely applied in electronic and photonic applications, such as non-volatile memory and neuro-inspired computing. Doped Sb$_2$Te alloys are now gaining increasing attention for on-chip photonic applications, due to their growth-driven crystallization features. However, it remains unknown whether Sb$_2$Te also forms a metastable crystalline phase upon nanoseconds crystallization in devices, similar to the case of nucleation-driven Ge-Sb-Te alloys. Here, we carry out ab initio simulations to understand the changes in optical properties of amorphous Sb$_2$Te upon crystallization and post annealing. During the continuous transformation process, changes in the dielectric function are highly wavelength-dependent from the visible-light range towards the telecommunication band. Our finite-difference time-domain simulations based on the ab initio input reveal key differences in device output for color display and photonic memory applications upon tellurium ordering. Our work serves as an example of how multiscale simulations of materials can guide practical photonic phase-change applications.
Discovering relationships between materials' microstructures and mechanical properties is a key goal of materials science. Here, we outline a strategy exploiting Bayesian optimization to efficiently search the multidimensional space of microstructures, defined here by the size distribution of precipitates (fixed impurities or inclusions acting as obstacles for dislocation motion) within a simple two-dimensional discrete dislocation dynamics model. The aim is to design a microstructure optimizing a given mechanical property, e.g., maximizing the expected value of shear stress for a given strain. The problem of finding the optimal discretized shape for a distribution involves a norm constraint, and we find that sampling the space of possible solutions should be done in a specific way in order to avoid convergence problems. To this end, we propose a general mathematical approach that can be used to generate trial solutions uniformly at random while enforcing an Euclidean norm constraint. Both equality and inequality constraints are considered. A simple technique can then be used to convert between Euclidean and other Lebesgue $p$-norm (the 1-norm in particular) constrained representations. Considering different dislocation-precipitate interaction potentials, we demonstrate the convergence of the algorithm to the optimal solution and discuss its possible extensions to the more complex and realistic case of three-dimensional dislocation systems where also the optimization of precipitate shapes could be considered.
Many topological band crossings (BCs) have been predicted efficiently utilizing the symmetry properties of wave-functions at high-symmetry points. Among various BCs, the so-called hourglass BCs (with the low-energy excitations dubbed as hourglass fermions) are fascinating since they can be guaranteed to exist under specific symmetry conditions even without realistic calculations. Such novel property renders the theoretical prediction on magnetic topological metals with hourglass BC (being Weyl point, Dirac point, lying in nodal loop, and so on) independent on the calculation methods and only determined by the symmetry of crystal and magnetic structure, namely, the magnetic space group (MSG). To date, there have no magnetic material verified with hourglass fermions. Here we first list all symmetry conditions that allow hourglass BCs in the 1651 MSGs and 528 magnetic layer groups (MLGs) with spin-orbital coupling (SOC): Only 331 MSGs and 53 MLGs can host hourglass BCs. Among these results, the essential hourglass BCs are highlighted, whose MSGs are then applied to predict hundreds of magnetic materials from the MAGNDATA magnetic materials database and first-principles calculations in the frame of LDA+SOC+U verify the hourglass BCs for different values of $U$. We take CsMn$_2$F$_6$, synthesized recently with a distorted pyrochlore structure to illustrate the hourglass band structure in detail which is very clear around the Fermi level and the topologically protected surface drumhead states of (100) surface are found to spread over more than one half surface Brillouin zone and only appear in a narrow energy window ($\sim 30$ meV), which could induce intriguing stability by prominent electronic correlation.
З 19 по 20 травня у Київському національному університеті будівництва і архітектури проведено VII міжнародну науково-практичну конференцію «Transfer of Innovative Technologies 2021». На ній були представлені креативні ідеї, інноваційні проекти й практичні розробки в галузях будівництва, архітектури, розв’язання нагальних проблем інженерії й проектування об’єктів, захисту навколишнього середовища, сучасні тенденції в інформаційних технологіях та ін. На конференції, яка відбувалась в режимі відеоконференцзв’язку, прийняли участь вітчизняні науковці, викладачі та студенти навчальних закладів, представники виробництв, відомі фахівці країн світу. Усього подано 128 заявок від півтори сотні учасників, у тому числі 15 іноземних з Австралії, Польщі, Словаччини, США, Казахстану, Німеччини, Китаю.
Конкурсна комісія визначила кращі роботи в номінаціях: Презентація, Інноваційний проект, Публікація, відзначила Дипломами преможців 2021 року. Учасники отримали Сертифікати, а найактивніші − Подяки за проведену роботу, міжнародні наукові зв’язки та організаційну підтримку форуму. В Збірнику матеріалів конференції (онлайн) та в журналі «Transfer of Innovative Technologies», Vol.4, No.1 опубліковано препринт статті, а презентації учасників – на сайті конференції. Кращі роботи рекомендовано до публікації в міжнародних наукових журналах Transfer of Innovative Technologies, Підводні технології: промислова та цивільна інженерія. Прийнято рішення щодо підготовки й проведення наступного форуму в 2022 році, залучення до інноваційної діяльності креативних учасників та нових установ, подальшої інтеграції у світовий науковий простір. Оргкомітет дякує всім за представлені матеріали та впровадження інноваційних технологій у життя!
The hybrid structure composed of aluminum alloy and carbon fiber reinforced plastics could combine their advantages. In order to investigate the weldability of these two lightweight materials, the hybrid joints of 5052 aluminum alloy (AA5052) and carbon fiber reinforced polyether ether ketone composites (CF-PEEK) were fabricated by friction stir spot welding. The variance analysis revealed that the dwell time and plunge speed were the most significant factors. By optimizing the welding parameters, the ultimate tensile shear load reached 2690±64 N (the dwell time: 8 s, the plunge speed: 10 mm/min). The interface could be divided into pin-affected zone, shoulder-affected zone, resin adhesive zone and resin concentrated zone. Since resin concentrated zone could not provide interfacial bonding due to delamination, the shoulder-affected zone and pin-affected zone were decisive regions for mechanical properties. The bonding mechanism included three parts: adhesive bonding provided by re-solidified resin, macro-mechanical interlocking of aluminum alloy that entered CF-PEEK, and micro-mechanical interlocking of resin that was tightly trapped at surface slits as well as the carbon fibers beset into AA5052. This work clarifies the interfacial characteristics of AA5052/CF-PEEK hybrid joints and provides an approach to improve the mechanical properties.
Materials of engineering and construction. Mechanics of materials
Abstract Objective Esophageal squamous cell carcinoma (ESCC) is featured by early metastasis and late diagnosis. MicroRNA-301 (miR-301) is known to participate in diverse cancers. Nevertheless, effects of miR-301 on ESCC remain unexplored. Thus, we aim to explore the role of miR-301 in ESCC progression. Methods Expression of miR-301 and phosphatase and tensin homologue (PTEN) in ESCC tissues and cell lines was assessed. Next, the screened cells were treated with altered miR-301 or PTEN oligonucleotide and plasmid, and then, the colony formation ability, cell viability, migration, invasion, cell cycle distribution and apoptosis of ESCC cells were assessed. Moreover, tumor growth and microvessel density (MVD) were also assessed, and the targeting relationship between miR-301 and PTEN was affirmed. Results MiR-301 was upregulated, and PTEN was downregulated in ESCC tissues and cells. KYSE30 cells and Eca109 cells were selected for functional assays. In KYSE30 cells, inhibited miR-301 or overexpressed PTEN suppressed cell malignant behaviors, and silenced PTEN eliminated the impact of miR-301 inhibition on ESCC progression. In Eca109 cells, miR-301 overexpression or PTEN inhibition promoted cell malignant behaviors, and PTEN overexpression reversed the effects of miR-301 elevation on ESCC progression. The in vivo assay revealed that miR-301 inhibition or PTEN overexpression repressed ESCC tumor growth and MVD, and miR-301 elevation or PTEN reduction had contrary effects. Moreover, PTEN was targeted by miR-301. Conclusion Taken together, results in our study revealed that miR-301 affected cell growth, metastasis and angiogenesis via regulating PTEN expression in ESCC.
Materials of engineering and construction. Mechanics of materials