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To solve the environmental problem of iron tailings, the preparation of green binding materials using iron tailings powder (ITP) shows bright prospects. However, the low activity of ITP limits its use as supplementary cementitious materials in large amounts. In this work, the activity of ITP treated for different milling times and at different sintering temperatures was studied, as well as the effects on the properties and microstructure of blended cement. It was found that ITP has a filling effect and provides additional nucleation sites. Additionally, ITP exhibits pozzolanic activity and consumes more hydration products at the later stage, which promotes the formation and deposition of C-S-H. All of these factors are related to the specific surface area (SSA) of the ITP and provide the conditions for cement paste densification, laying a foundation for the strength of cement blended with ITP. In summary, the activity of activated ITP is related to its SSA. It takes a long time for ITP to show pozzolanic activity. Activated ITP undergoes a secondary reaction to form a hydration product. The environmental impact and cost of pure cement pastes were higher than those of the cement–ITP pastes.

Stacking of bulk solids in terminals, ships, trains, and other bulk solids storage yards is always challenging, considering the requirements of optimal utilization of storage areas. In this study, stacking shapes of a variety of bulk solids with different particle sizes were tested, and the curved shapes of the stockpiles were extracted to establish the actual three-dimensional models of the bulk solids accordingly. The three-dimensional curved stockpiles were used to design the bulk solids stacking strategy where the bulk stacking locations, the stacking volume, and the stacking flatness were optimized. A modified golden section method with a self-influenced factor was developed to improve the calculation efficiency of the stacking algorithm for bulk solids stacking flatness. Furthermore, the bulk solids stacking strategy and algorithm were verified by experiments. The results showed that the curved three-dimensional models were very close to the actual shapes of the bulk solids stockpiles, while the improved golden section method was more accurate and efficient than the traditional golden section method in determining the optimal values of the stacking volumes in terms of flatness. For the different bulk solids tested, the experiment results showed that good flat stacking can be achieved by using the developed stacking strategy.

Most previous studies have focused on the addition of nanoparticles of silicon dioxide, calcium carbonate, aluminium oxide, tin(IV) oxide or calcium silicate hydrate to speed up cement hydration. In this research, nano seeds of calcium aluminium silicate hydrate (C–A–S–H) were added to Portland cement systems. It was found that, with the addition of 1%, 3% and 5% C–A–S–H seeds, the hydration process was brought forward by about 2 h, 3 h and 7 h, the initial setting time was reduced by 16.4%, 25.5% and 34.5%, and the final setting time was reduced by 16.8%, 35.1% and 41.1%, respectively. However, the paste fluidity was reduced by 11.6%, 21.6% and 28.9%, respectively, resulting in decreased workability. X-ray diffraction analysis showed that adding C–A–S–H seeds accelerated the formation of calcium monosulfoaluminate hydrate (AFm). Compared with a control sample, the compressive strength of the mortar doped with 1% C–A–S–H seeds was increased by 4.6%, 3.4% and 5.2% at 3, 7 and 28 days, respectively. However, an increase in the content of C–A–S–H seeds to 3% and 5% led to decreases in compressive strength. The total porosity declined with the addition of 1% C–A–S–H seeds, whereas the total porosity with 3% and 5% C–A–S–H seeds was higher than that of the control sample.

Six novel donor–acceptor conjugated polymers were designed and synthesized by the Stille coupling reaction of triarylamine derivatives as donor units with isoindigo derivative or benzothiadiazole as acceptor units. These polymers have good solubility and film-forming properties in common organic solvents. The char yields of polymers in nitrogen atmosphere at 800 °C range from 34 to 60%. In particular, these conjugated polymers exhibit high photoluminescence (PL) quantum efficiency (up to 42.9%). These polymers demonstrate two pairs of redox peaks with low onset voltages (0.51 V vs. Ag/AgCl for P5) and narrow band gaps (Eg = 2.52 ~ 2.95 eV). The colors of all polymer films change significantly with the applied voltage increasing. Moreover, the polymers show high coloring efficiency (up to 163%) and maintain good electrochromic (EC) cycle stability over 500 s. In addition, excellent results in terms of memory storage (ON/OFF = 1.2 × 104), 2,4,6-Trinitrophenol (TNP) detection (Ksv = 45,790 M-1) can meet the requirements of multifunctional materials.

For dielectric energy storage materials, high polarization and high breakdown strengths are a long-standing challenge. A modulating crystalline/amorphous phase structure strategy is proposed by Mn-doping and annealing temperature to enhance the energy storage performance of pure BaTiO3 (BT) films. In this study, lead-free Mn-doped BT films were prepared on Pt/Ti/SiO2/Si substrates via the sol-gel method, and the effects of the crystalline/amorphous phase ratio on polarization and electric properties were analyzed. A small amount of Mn-doping in BT could reduce the annealing temperature and enhance polarization with an Mn content of 8%. In addition, the energy storage properties of BT-8%Mn films achieve the best energy storage performance in terms of energy density and efficiency of 72.4 J/cm3 and 88.5% by changing the annealing temperature to 640 °C. BT-8%Mn energy storage films also possess good stability over a wide temperature range of 20 °C–200 °C, which demonstrates that crystalline/amorphous engineering is a simple and effective way to enhance energy storage applications of dielectric films.

CO2 technology has been progressively used in the development of shale oil. After injection, CO2 can react with formation water to form carbonic acid, which then reacts with carbonate and silicate minerals, resulting in changes in porosity and permeability. However, there are some debates as to whether the effect of CO2 improves or damages porosity and permeability. So, in this paper, systematic experiments were carried out to clarify the interaction between CO2 and shale in different lithofacies and to draw a pertinent conclusion. The results showed that the shale in Qingshankou Formation could be divided into three main lithofacial types: foliaceous shale, laminated feisic shale and laminated diamictic shale. There were relatively more pores, some natural microfractures and small mineral particles in foliaceous shale, a few micropores and large mineral particles in laminated feisic shale, some biogenic calcium carbonate minerals and hardly any micropores in laminated diamictic shale. Due to the diversity of micromorphology and mineral composition, the effects of CO2 treatment had significant differences. For foliaceous shale, CO2 treatment had both improving and damaging effects on porosity and permeability; for laminated shale, both porosity and permeability improved significantly. So, it is necessary to identify the main lithofacies of target formation before the application of CO2 technology in shale oil reservoirs.

In the present research work, the ternary effects of varying dosages of graphene oxide encapsulated silica fume (GOSF), nano-silica sol (SS), and fly ash (FA) on the rheological properties, compressive strength, the content and crystal size of calcium hydroxide (CH), porosity, water absorption, and microstructure of cement were studied. The results showed that the incorporation of SF improved the dispersion of GO in the cement matrix. GOSF was prepared through electrostatic attraction between the positively charged SF and negatively charged GO. The ternary mixture of GOSF, SS, and FA had a synergistic effect that improved the performance of cement. When the curing age of cement reached 28 days, the compressive strength reached a peak of 86.5 MPa, the minimum values of content and crystal size of CH were 11.55% and 45.69 nm, respectively, and the minimum values of water absorption and porosity were 0.0011 cm/s0.5 and 13.56%, respectively. In terms of microstructure, the denser structure of C-S-H gel and the regular arrangement of CH were noticed.

Graphene oxide (GO) was used as emulsifier to prepare the microencapsulated phase change materials (MePCMs) with high thermal stability and impermeability, the chemical structure, particle size distribution, micro-morphology and thermal performance of the microcapsules were investigated by Fourier transform infrared spectrometer (FTIR), laser particle analyzer, scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The results showed that when GO was used as emulsifier with Span80 and Tween 80, the MePCMs prepared with a higher thermal performance, the particle size are concentrated, the decomposition temperature of the MePCMs are improved, the MePCMs are prepared with a high latent heat with the paraffin content of about 49.9%, the impermeability performance of the MePCMs are obviously improved compared with the samples prepared with other emulsifiers. The gypsum materials that incorporated with different contents of the MePCMs were prepared, the compressive and flexural strength of the gypsum materials are decreased with the increase of the content of the MePCMs, when the content of the MePCMs exceeds 30%, the microcapsules begins to agglomerate in the gypsum, which results in a low compatibility of the MePCMs and gypsum matrix; the incorporation of MePCMs endow the temperature regulation performance of the gypsum building materials, the thermal conductivity of the gypsum materials are decreased as the incorporation of the MePCMs.

Nanodiamond-supported crystalline SnO2 nanoparticles (SnO2/ND) were successfully synthesized from ND-dispersed SnCl4·5H2O aqueous solution via the isothermal hydrolyzing method at 60 °C. The XRD an...

Designing and researching efficient non-precious metal catalysts is of great significance for the development of electrocatalysis in hydrogen evolution reaction (HER). Cobalt nanoparticles ...

Considering the excellent electrical, optical and mechanical properties, ternary boron carbonitride (BCN) have attracted widespread attentions. Herein, we report an effective strategy for synthesis of nanoporous BCN. The morphology, structure and composition, as well as the electrochemical properties were systematically studied. It was found that the nanoporous BCN prepared at 800 °C showed the highest specific capacitance (475 F/g) and excellent cycle stability (97.7%) over 3000 cycles. This is mainly due to the larger specific surface area (506.9 m2/g) of the product, which can provide more contact area and active site between the electrode material and electrolyte. Compared with pseudocapacitor, the electrode material has better cycle stability and potential application in supercapacitor, which is the typical electric double layer capacitor.

Platinum matrix composite is a new type of functional pottery material, which has excellent mechanical, electrical and optical properties. Due to the complexity of the synthesis method and the expensive equipment, the development of cermet material is extremely slow, so that the method to solve the problem is urgently needed. In view of the excellent performance of the Pt-C compounds, by hydrothermal method and high temperature roasting method, a new synthesis method for the composite is proposed using melamine and four platinum chloride at 60 °C by the polymerization reaction with a molar ratio of 20:1. The synthetic of Pt-C compounds provides a new synthesis method and new ideas and at the same time the Pt-C compounds has excellent performance, showing the excellent applications in machining.

Graphene, whose structure is composed of a single-atom-thick sheet of sp2-hybridized carbon atom, provides large specific surface area, excellent mechanical and chemical properties. In this paper, reduced graphene oxide/carbon nanotube (rGO/CNT) composite, which had superior electrochemical performance, was synthesized via a facile, handy and cheap method. Electrochemical tests showed that rGO/CNT composite that the weight ratio of graphene oxide (GO) to CNTs is 7.5 to 1 exhibited the specific capacitance was 346.84 F/g at the current density of 2 A/g in 1 M H2SO4. The good performance of rGO/CNT composite was ascribed to huge surface area of rGO and homogeneous distribution of CNT, which prevented the aggregation of rGO sheets, increased the path of electron circulation and speeded up the electrolyte penetrating into the materials. Therefore, rGO/CNT composite had great potential on supercapacitors.

Ultra-lightweight foamed geopolymer (UFG) based on fly ash-metakaolin blends with its density of between 150 kg/m3 and 300 kg/m3 was successfully prepared by the mixed foaming method of chemical foaming. In the present study, the properties and characteristics of UFG were investigated by designing and optimizing the components of fly ash, metakaolin, alkaline activator, foam stabilizer and foaming agent (H2O2), as well as the curing temperature. The results showed that foamed geopolymer with curing age of 7 days presented its dry density between 150 kg/m3 and 300 kg/m3, the mean pore size between 0.57 mm and 1.13 mm, the porosity between 71.8% and 84.5%, the thermal conductivity between 0.0622 W/(m·K) and 0.0852 W/(m·K) and the compressive strength between 0.68 MPa and 2.23 MPa, showing better mechanical properties than the traditional portland cement foamed concrete with the same density. It is also found that curing temperature at 55 °C for 12 h seemed to substantially improve the compressive strength of UFG which is 1.91 MPa compared to curing at 25 °C for the same period of time.

C(-A)-S-H (CaO(-Al2O3)-SiO2-H2O) gel is the main product and source of strength in alkali-activated slag systems. Previous studies on C-A-S-H have focused mostly on the characterization of the structure and composition of the products. In this study, synthetic C-A-S-H particles with a similar composition as gels produced by alkali-activated slag were prepared by a hydrothermal method and were added to the alkali-activated slag systems, and the synthetic can be regarded as a chemical intensifiers of hardening (CIH). The effects of the synthetic C-A-S-H on the hydration process, the early-stage mechanical properties, and the microstructure of the alkali-activated slag were investigated by hydration heat tests, scanning electron microscopy (SEM), mercury intrusion porosimetry tests (MIP), and other methods. The results showed that the synthetic C-A-S-H shortened the setting time, promoted the formation of an acceleration period at an early stage, and increased the hydration heat released during the acceleration period. The synthetic C-A-S-H improved the flexural and compressive strength of the alkali-activated slag to a certain extent and the improvements in the flexural strength were more significant than the improvements in the compressive strength; the flexural strength of the sample with the added 3% synthetic C-A-S-H with 3-d curing increased by 16.25%. Microstructure analysis indicated the synthetic C-A-S-H also reduced the porosity of the alkali-activated slag-hardened paste and optimized the pore size distribution. This study of the early-stage performance provides a new approach and predictions for the late-stage performance and in-depth modification mechanisms of alkali-activated slag systems.

In this paper, the influence of calcium sulfate type (α-hemihydrate, anhydrite and dihydrate) and amount (0%, 2%, 4% and 6%) on the performances of calcium aluminate cement-based self-leveling mortar (SLM) were investigated. The influence of calcium sulfate on fluidity and mechanical properties was investigated. Moreover, the impact of calcium sulfate on the hydration products, morphology and heat evolution of pastes hydrated up to 3 days were determined by using X-ray diffraction (XRD), Scanning electron microscope (SEM) and isothermal heat-conduction calorimeter. Test results revealed that SLM prepared with anhydrite exhibited the highest initial flow value (∼160 mm) and setting time and the lowest fluidity loss due to the slow dissolution rate of anhydrite compared to other calcium sulfate. In comparison to control formulation, the enhancement in flexural and compressive strength for T4 (dihydrate) was the highest and was found to be 485.71% and 437.5% respectively and hence it can be concluded that dihydrate is favorable to the early strength of SLM as compared to other SLM formulations containing α-hemihydrate and anhydrite respectively. The shrinkage compensating effect became more obvious with the increase in the amount of C$ in SLM samples. Due to the fast dissolution rate, mortar containing α-hemihydrate exhibited more expansion as compared to other calcium sulfate. SLM prepared with dihydrate showed the highest early strength due to the lowest influence on C3S hydration while the influence of α-hemihydrate was more obvious. Hence, the hydration of PC in the ternary system can be limited by increasing calcium sulfate due to the formation of ettringite. Finally, the type of calcium sulfate has an important influence on the quantity and morphology of ettringite.

Social media has drawn scientists' attention due to their potential values for health and marketing, among other activities. To effectively exploit such huge online resources by using incomplete user profiles, which are very common on social media sites and can be caused by user privacy settings, it is meaningful to explore user profile identification methods. In this paper, we focus on gender identification using reposting behaviors on social networks. Whereas most existing works rely on pure statistical methods, we propose a scheme that is underpinned by homophily and four intuitive methods based on it by combining knowledge of statistics and sociology. For our data set, which was obtained from Sina Weibo and contained 1039 test samples and 528k user profiles, our methods perform with 86.7% accuracy. We explore the sensitivity of our methods on the scale of the data set and find surprisingly competitive results surpassing the binary classification baseline. Finally, we further suggest possible extensions to our methods.

In this paper, C-A-S-H with different Li contents have been synthesized by hydrothermal method at 95℃. Incorporation of Li decreases mean interlayer distance, increases crystallinity and polymerization degree of C-A-S-H. The specific surface area of C-(Li)-A-S-H decreases sharply with the addition of LiOH. What’s more, katoite forms on the surface of C-(Li)-A-S-H and results in the change of pore structure at high LiOH concentrations. The results show that Ca/Li ratio is the key parameter for Li incorporation into C-A-S-H.

Gossamer space structures technology have gained widely applications in space missions. However, the vibration problem is a great challenge which makes the technology complicated. The overall motivation of this work is to develop a vibration control system for gossamer space structures. In this study, a space membrane structure with piezoelectric stack actuators bracketed on its support frame is considered. First, the description of the smart space membrane structure and its dynamic model are presented. Then, a decentralized adaptive fuzzy control method is developed to control the structure vibration. Finally, experimental system is built up, and two vibration control experiment cases are carried out to verify the proposed control method. Experimental results demonstrate that the proposed control method is more effective than the fuzzy control method.

Mohite-type ternary sulfide Cu2SnS3, which has been intensively studied in the photovoltaic field, has recently attracted much attention as an outstanding p-type eco-friendly thermoelectric material. In the present work, significant synergistic effects of d-orbital-unfilled transition metal (Co) doping on the crystal structure and electrical/thermal properties of Cu2SnS3 are reported. Crystal structure evolution with Co doping, involving not only monoclinic to cubic and tetragonal transitions but also the formation of a hierarchical architecture (Cu–S nano-precipitates, metal and S vacancies, and even nano-scaled stacking faults), is related to bond softening and intensified phonon scattering. Thus, an ultralow lattice thermal conductivity of 0.90 W m−1 K−1 at 323 K to 0.33 W m−1 K−1 at 723 K was obtained. Moreover, an increased effective mass is derived from the contribution of the Co 3d states to the inherent Cu 3d and S 3p states in the valence band, leading to a remarkable power factor (0.94 mW m−1 K−2, x = 0.20 at 723 K) with optimal doping. As a result, the high ZT of ∼0.85 at 723 K elevates the modified Cu2SnS3 to the level of state-of-the-art mid-temperature eco-friendly sulfide thermoelectric materials.

In this study, zinc oxide/carbon nanotubes/reduced graphene oxide (ZnO/CNTs/rGO) composites were synthesized using a simple and facile magnetic stirring method at room temperature. The photocatalytic activity of the composites under UV-vis light irradiation was studied using Rhodamine B (RhB) as the model compound. RhB solution was almost completely degraded in 30 min for ternary composite, and a ca. 200% improvement in the degradation efficiency by ZnO/CNTs/rGO was found when the rate constant k of the pseudo-first-order reaction was compared with that using ZnO only. This finding demonstrated the positive effects of CNTs and rGO on reducing electron-hole pair recombination and extending the light adsorption range. We furthermore determined the optimum stoichiometric amount of each component. Overall, this work provided a method of enhancing photocatalytic performance by combining the ZnO and CNTs/rGO.

Graphene oxide (GO) has received great attention as a nanosized reinforcing agent in cement-based materials. However, GO easily aggregates in an alkaline cement matrix and suffers from poor dispersibility, which reduces the beneficial effect on the final properties of cement composites. In this study, GO-polycarboxylic acid superplasticizer (GPC) was synthesized by free-radical copolymerization of GO with methyl allyl polyoxyethylene ether (TPEG), sodium styrene sulfonate (SSS) and acrylic acid (AA). The chemical structure of the GPC was characterized by X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). To understand the influence of GO on the cement hydration process, we analyzed hydration heat, phase composition, and TG/DSC behavior. The pore structure and micromorphology of the cement composites were investigated by mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). The results showed that the GO layer spacing increased after copolymerization, and the GO surface was covalently grafted with PC macromolecules. The addition of GPC to cement yields uniform dispersion of GO and reduces the adverse effects of GO on the fluidity of the cement slurry. GPC can accelerate cement hydration, promote crystallization of calcium hydroxide (CH) in the cement slurry, refine grain size, and enhance mechanical properties of the cement-based materials.

This study finds that the slip-hardening parameter (β) increases with the increasing of PE (Polyethylene) fiber inclination for UHS-UHDCC (ultra-high strength and ultra-high ductility cementitious composites), the slip-hardening increasing coefficient (ω) is introduced to correct the β of ECC model. Therefore, the single PE fiber pullout micro-mechanical model is proposed, and this study defines the debonding behavior of PE fiber as the ‘physical debonding’. The pullout load–displacement curve of the single PE fiber and the single crack stress-opening curve verify the correctness of proposed micro-mechanical model for UHS-UHDCC. The first-crack stress ( σ fc , 5.78 MPa) and the fiber bridging complementary energy ( J b ' , 352.1 J/m2) satisfy the strength and the energy criteria, this ensures the realization of the tensile strain-hardening behavior. This study provides a theory basis for realizing the multi-cracking strain hardening behavior of UHS-UHDCC.

The influence of boron addition on oxidation behaviors of high-Nb-containing TiAl alloys was investigated using isothermal oxidation tests at 900 °C in air. The results indicated that boron addition refined the lamellar colony structure and significantly improved the high-temperature oxidation resistance. Fine lamellar colonies were conducive to reducing thermal stress during oxidation, which delayed the cracking of the oxide scale. Furthermore, the generated oxide implants intensified the adhesive strength between the oxide scale and substrate, further enhancing the oxide-scale spallation resistance. In summary, the superior adhesion of the oxide scale resulted in a better oxidation resistance of the boron-containing alloy.

The ternary effects of nanosilica/polycarboxylate ether superplasticizer nanocomposite (NS@PCE), graphene oxide (GO) and fly ash (FA) with different dosages on workability, fly ash hydration, water sorptivity, compressive strength and microstructure development of cement paste were investigated. The results revealed that the NS@PCE addition improves the workability of cement paste significantly. The single addition of NS@PCE or GO have favorable effect on hydration of FA particle, whereas the hybrid of both in cement cause a bit loss of the FA hydration degree (FA HD). 1% of NS@PCE addition and 0.01% of GO dosages in FA-blended cement are sufficient for compensate its early strength loss caused by the FA incorporation. Microstructure investigation verified the formation of new polyhedron-like crystals, with an average length of 1.25 µm and Ca/Si ratio of 12.99, in cement of 28 days.

This paper investigates the viability of using waste glycerin (WG), industry lignin (IL) and cane molasses (CM) used as grinding aids in blended cement, performance of the blended cement with single and composite grinding aids were researched. The structure characterization of the grinding aids was carried out by Fourier transform infrared spectroscopy (FT-IR); the particle size distribution, Blaine specific surface area, setting times, water requirement of normal consistency, flexural and compressive strengths at 3 and 28 days of the blended cement were researched, the experiments results indicate that the addition of grinding aids results in an improvement of the fineness and strength of the blended cement. Compared with the cement mixture without grinding aids, waste glycerin has a better optimization effect on the particle size distribution, industry lignin and cane molasses perform a better retarding effect, and enhancement effect of cane molasses on the strength of blended cement is more significant. For the blended cement with composite grinding aids (0.0065% WG, 0.0095% IL, 0.024% CM), the compressive strength at 3 days and 28 days are 2.6 MPa and 10 MPa higher than those of the control cement respectively. The hydration products and microstructure of blended cement with composite grinding aids were analyzed by X-ray diffraction (XRD), thermo-gravimetric and differential scanning calorimetry (TG-DSC) analysis and scanning electron microscopy (SEM), the research shows that for the blended cement, the addition of grinding aids can accelerate the hydration reaction degree and improve the compactness and uniformity of the products structure.

This paper experimentally investigates the fatigue performance of stainless steel bolts in tension and shear under constant-amplitude loading. The static behaviour of normal bolts and Hollo-bolts subjected to monotonic loading was initially reported aiming to obtain the ultimate strength. Periodic loading tests were thereafter performed to acquire tensile and shear fatigue life under various stress ranges in which failure modes and cycles were recorded. From test results, S-N curves were summarised through regression analysis, followed by numerical modelling which was used to investigate the stress distribution. Finally, different design codes were selected to estimate the fatigue limit of bolts in tension and shear. It was found that both coupon tests and monotonic loading tests are required to determine the material property of stainless steel bolts. Regions adjacent to bolt nuts are the most vulnerable parts in terms of fatigue in tension, and the maximum principal stress dominates the fatigue life of fasteners with threads in shear plane. The fatigue strength of Hollo-bolts is slightly higher than that of normal bolts. Moreover, although current design codes can conservatively estimate the fatigue behaviour, provisions for shear fatigue are recommended to be modified for higher accuracy and better application.

Mimicking natural structures has been highly pursued recently in composite structure design to break the bottlenecks in the mechanical properties of the traditional structures. Bone has a remarkable comprehensive performance of strength, stiffness and toughness, due to the intricate hierarchical microstructures and the sacrificial bonds within the organic components. Inspired by the strengthening and toughening mechanisms of cortical bone, a new biomimetic composite structure, with a designed progressive breakable internal construction mimicking the sacrificial bond, is proposed in this paper. Combining the bio-composite staggered plate structure with the sacrificial bond-mimicking construction, our new structure can realize tunable stiffness and superior toughness. We established the constitutive model of the representative unit cell of our new structure, and investigated its mechanical properties through theoretical analysis, as well as finite element modeling (FEM) and simulation. Two theoretical relations, respectively describing the elastic modulus decline ratio and the unit cell toughness promotion, are derived as functions of the geometrical parameters and the material parameters, and validated by simulation. We hope that this work can lay the foundation for the stiffness tunable and high toughness biomimetic composite structure design, and provide new ideas for the development of sacrificial bond-mimicking strategies in bio-inspired composite structures.

K-A-S-H (K2O-Al2O3-SiO2-H2O) gel is a key phase that forms in most alkali-activated binders (eco-friendly binders which utilize a substantial amount of industrial by-product). An in-depth understanding of the microstructure and performance of this nano-sized key phase facilitates better application to alkali-activated binders. However, such studies remain little and undetailed. Therefore, our research aims to provide insights into the microstructure of K-A-S-H particles synthesized with accurate stoichiometric control by the hydrothermal method through thermogravimetric analysis (TG), Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and BET surface area. The results show that for materials prepared at the curing temperature lower than 80 &deg, C, the K-A-S-H products were completely amorphous. With increased curing temperature and time, the K-A-S-H products were transformed from the amorphous phase to the crystalline zeolite phase structure, with a reduction in the specific surface area. The TG results indicate that the crystalline phase contains more non-evaporated water or zeolite water for structural rearrangement. The degree of tetrahedral polymerization slightly decreased with an increase of the K2O/SiO2 ratio as the amount of non-bridged oxygen atoms increased, whereas it gradually increased with an increase of curing temperature and time, as suggested by the FTIR and NMR results. Various K2O/SiO2 ratios resulted in the formation of zeolite K-H and K-G zeolite, both of which exhibited highly polymerized three-dimensional network structures. However, there was no significant effect of the SiO2/Al2O3 ratio on the structure of K-A-S-H products. Overall, these results provide insight into understanding the chemical stability of K-A-S-H.

AgNbO3 cubes with an exposed high-energy (001) facet were prepared by hydrothermal treatment of Ag2O–Nb2O5–NH4HF2 aqueous suspension. The crystal phase, surface microstructure, and optical properties of the samples were characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, and UV–vis diffuse reflectance spectroscopy. The energy band structure and charge carrier separation efficiency were investigated by photoelectrochemical measurements. In comparison with AgNbO3 powder, whose surface was dominated by a low-energy (114) facet, the AgNbO3 cubes had superior visible-light-driven photocatalytic activity for degradation of tetracycline because of the greater redox ability and more efficient separation of photogenerated electrons and holes. The surface F− ions had no influence on the photocatalytic reactions. Radical trapping experiments demonstrated that the superoxide radical played a decisive role in the photodegradation of tetracycline.

Boron carbonitrides (BCN) have attracted great interest in superhard or energy storage materials. In this work, thin BCN sheets were synthesized at 250 °C by a facile and green solvothermal method. The structure and morphology were characterized by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Based on the results of electrochemical experiments, the thin BCN sheet exhibited excellent capacitance performance (343.1 F/g at a current density of 0.5 A/g) and cycling stability (90%), which showed high potential applications in supercapacitors.

In this study, the effects of graphene oxide (GO) on the microstructure of cement mortars were studied using scanning electron microscopy (SEM), thermogravimetric (TG), and X-ray diffraction (XRD) techniques. Cement mortar samples with different proportions of GO (0.02, 0.04, 0.06, and 0.08 wt % based on the weight of cement) were prepared. The test results showed that GO affected the crystallization of cement hydration products, C–S–H (calcium silicate hydrate is the main hydrate product) and CH (calcium hydroxide). The morphology of hydration products changed with the increase of GO content. Furthermore, the results of XRD analyses showed that the diffraction peak intensity and the crystal grain size of CH (001), (100), (101), and (102) for GO samples increased considerably compared with the control sample. Based on the results, it can be understood that GO can modify the crystal surface of CH, leading to the formation of larger crystals.

Vibration control problem of solar panel structure is an ultra-important problem which was studied by a lot of researchers. This research is devoted to design an “intelligent” control algorithm for this problem, which can learn autonomously without supervision or a priori training data. Based on this idea, an online learning-based fuzzy control method is proposed in this article. The online learning-based fuzzy control is composed of reinforce learning algorithm and fuzzy inference system. The learning algorithm learns the fuzzy rule base by interaction with the plant and changes rule base generated by policy via evaluative reward signal to realize the learning goal. In order to verify the presented control method, vibration control of a typical single-panel smart solar panel structure bonded with piezoelectric actuators is considered in this article. First, the dynamic model of the smart solar panel structure is established using finite element method. Then, the state-space equation of the control system is presented. After that, technique details of the online learning-based fuzzy control method are described. Finally, experimental validation is conducted. The experimental results show that the online learning-based fuzzy control method presented in this article can suppress the vibration of the smart solar panel effectively and faster than fuzzy control method.

An accurate dynamic mechanical model plays a vital role in the engineering application of rubber-like materials. Though many researchers have done work on these models, it is still difficult to fit the model's parameters via dynamic mechanical thermal analysis (DMTA) data, especially for Havriliak–Negami (HN) model. A methodology is proposed to determine the parameters in HN model. The DMTA data of carbon black filled rubber (CBFR) NR100N550 is utilized to verify the methodology in this paper. The time–temperature superposition principle (TTSP) is applied to investigating the viscoelastic properties of CBFR NR100N550 at wide frequency range. The experimental results show that the proposed methodology could be applied to obtaining parameters in HN model. HN model is able to model the dynamic mechanical properties of carbon black filled rubbers at wide frequency range, which are correlated with the chemical structure of the polymers.

Filled rubber-like materials show a significant dependence on predeformation, frequency and amplitude when they are loaded with static predeformations superimposed by harmonic deformations. In order to investigate this predeformation-, frequency- and amplitude-dependent material behavior, a recently developed constitutive model of finite viscoelasticity is proposed based on the models of Lion and Kardelky (2004) and Hofer and Lion (2009). The constitutive equations are geometrically linearized in the neighborhood of predeformation and then formulated for incompressible materials. Finally, the process of parameter identification and some numerical aspects are shown. Additionally, the experimental verification and some numerical simulations will also be supplied. The results show that our model cannot only be used for loading cases with small strains but also with large strains. It may have some meanings for practical engineering applications.

C-A-S-H (CaO-Al2O3-SiO2-H2O) and N-A-S-H (Na2O-Al2O3-SiO2-H2O) have a wide range of chemical compositions and structures and are difficult to separate from alkali-activated materials. Therefore, it is difficult to analyze their microscopic properties directly. This paper reports research on the synthesis of C-A-S-H and N-A-S-H particles with an average particle size smaller than 300 nm by applying the hydrothermal method. The composition and microstructure of the products with different CaO(Na2O)/SiO2 ratios and curing conditions were characterized using XRD, the RIR method, FTIR, SEM, TEM, and laser particle size analysis. The results showed that the C-A-S-H system products with a low CaO/SiO2 ratio were mainly amorphous C-A-S-H gels. With an increase in the CaO/SiO2 ratio, an excess of Ca(OH)2 was observed at room temperature, while in a high-temperature reaction system, katoite, C4AcH11, and other crystallized products were observed. The katoite content was related to the curing temperature and the content of Ca(OH)2 and it tended to form at a high-temperature and high-calcium environment, and an increase in the temperature renders the C-A-S-H gels more compact. The main products of the N-A-S-H system at room temperature were amorphous N-A-S-H gels and a small amount of sodalite. An increase in the curing temperature promoted the formation of the crystalline products faujasite and zeolite-P. The crystallization products consisted of only zeolite-P in the high-temperature N-A-S-H system and its content were stable above 70%. An increase in the Na2O/SiO2 ratio resulted in more non-bridging oxygen and the TO4 was more isolated in the N-A-S-H structure. The composition and microstructure of the C-A-S-H and N-A-S-H system products synthesized by the hydrothermal method were closely related to the ratio of the raw materials and the curing conditions. The results of this study increase our understanding of the hydration products of alkali-activated materials.

Energy piles—A fairly new renewable energy concept—Use a ground heat exchanger (GHE) in the foundation piles to supply heating and cooling loads to the supported building. Applying phase change materials (PCMs) to piles can help in maintaining a stable temperature within the piles and can then influence the axial load acting on the piles. In this study, two kinds of carbon-based composite PCMs (expanded graphite-based PCM and graphite nanoplatelet-based PCM) were prepared by vacuum impregnation for potential application in energy piles. Thereafter, a systematic study was performed and different characterization tests were carried out on two composite PCMs. The composite PCMs retained up to 93.1% of paraffin and were chemically compatible, thermally stable and reliable. The latent heat of the composite PCM was up to 152.8 J/g while the compressive strength of cement paste containing 10 wt % GNP-PCM was found to be 37 MPa. Hence, the developed composite PCM has potential for thermal energy storage applications.

Trajectory tracking control of space robots in task space is of great importance to space missions, which require on-orbit manipulations. This paper focuses on position and attitude tracking control of a free-floating space robot in task space. Since neither the nonlinear terms and parametric uncertainties of the dynamic model, nor the external disturbances are known, an adaptive radial basis function network based nonsingular terminal sliding mode (RBF-NTSM) control method is presented. The proposed algorithm combines the nonlinear sliding manifold with the radial basis function to improve control performance. Moreover, in order to account for actuator physical constraints, a constrained adaptive RBF-NTSM, which employs a RBF network to compensate for the limited input is developed. The adaptive updating laws acquired by Lyapunov approach guarantee the global stability of the control system and suppress chattering problems. Two examples are provided using a six-link free-floating space robot. Simulation results clearly demonstrate that the proposed constrained adaptive RBF-NTSM control method performs high precision task based on incomplete dynamic model of the space robots. In addition, the control errors converge faster and the chattering is eliminated comparing to traditional sliding mode control.

Based on the higher order shear deformation theory and the Hamilton principle, this article derives the equations to govern the displacement and electric potential of smart functionally graded (FG) circular cylindrical panels with surface embedded on actuator and sensor layers. The analytical solution considering simply supported boundary conditions is based on the Navier solution procedure. Negative velocity feedback control is used. Numerical results show the influence of (a) different volume fractions of FG material layer, (b) different temperature change of inner surface, (c) different central angle of circular cylindrical panels, (d) different piezoelectric material (PZT-4, BaTiO3, PZT-5A), on the vibration characteristics of smart FG circular cylindrical panels in thermal environmental.

A novel calcium phosphate cement was developed by adding different amount of SrO to tetracalcium phosphate during the fabrication process. The experimental results show that compressive strength of cements based on tetracalcium phosphate doped with SrO significantly increases with the increase of SrO content, approximately 60 MPa, whilst the mechanical behavior of CPC slightly decreases if 0.7wt% SrO is added. X-ray diffraction measurement confirms the setting reaction of doped cements is similar to that of pure calcium phosphate cement (CPC). Low crystalline hydroxyapatite (HA) is found to be the main constituent of set cement. A mechanical reinforcement effect is resulted from the substitution of Sr ion to Ca2+ in tetracalcium phosphate (TTCP), accelerating HA crystal formation and a more cross-linked cement structure. In vitro bioactivity tests showed that CPC added with 0.5wt% SrO had a more rapid degradation compared with pure CPC.

Flywheels are widely used on-board spacecraft for attitude control or energy storage. However, micro-vibrations generated by flywheels will influence the performance of high-sensitivity instruments on-board the spacecraft. This study addresses the dynamic modeling and analysis of the micro-vibration isolation of flywheel assemblies. Firstly, an analytical model was developed to describe the coupled multiple flywheel system (MFS) and multi-axis isolation system, with equations in state-space form presented for control purposes. This analytical model properly reflects the mass and inertia properties, the gyroscopic effects and the flexible modes of the coupled system, which can be generalized for isolation applications when multiple flywheels are mounted together. Secondly, the analytical model was validated using the MSC.NASTRAN software based on finite element techniques. Finally, using the proposed model, we investigated the coupled dynamics of the MFS and the isolation system. The results show that the mass and inertial properties and the gyroscopic effects of the MFS will induce couplings between the structural modes. The gyroscopic effects of one flywheel interact with or counteract the effects of the others, which will produce complex vibrational modes and affect the isolation performance accordingly. Thus, the coupled dynamics within the system should receive attention during isolation design for the MFS.

Large split-blanket solar arrays are semi-rigid structures. It is difficult for this kind of structure to achieve vibration suppression. In order to solve this problem effectively, firstly, we use the finite element method to construct a dynamic model of a solar array with piezoelectric smart structure, and then we propose a new control method, namely the autonomous decentralized intelligent control to address the vibration control problem. Based on the concept of autonomous decentralized control presented in this paper, the control system can be divided into multiple autonomous subsystems. Each subsystem performs several control functions without external intervention. Numerical simulations are carried out to verify the proposed control strategy. The results indicate that this method is effective. Compared with the traditional positive position feedback control method, the attenuation time of the structural bending vibration can be reduced by half with the proposed method. Furthermore, the control system can perform well even under severe subsystem failure without external intervention.

Diamond-like B-C-N compounds have the excellent potential properties like diamond or cubic boron nitride. In this paper, diamond-like B2(CN)3compound has been studied by first principle calculations. After geometry optimization, hexagonal and monoclinic B2(CN)3models were obtained. According to the band structure and density of state calculated, they are conducting. The relative stability was proved using elastic constants calculated by Born criterion. The monoclinic B2(CN)3is one of hard material with theoretical Vickers hardness 38 GPa.