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To investigate the mechanical behavior of the steel plate girder strengthened by the external prestressed tendon, three typical and representative steel plate girders (K2, K3, and K4) are taken as the research background. Based on their structure characteristics and safety assessment, the effective and feasible reinforcement scheme of the steel plate girder is proposed first. And then, a three-dimensional finite element model of the steel plate girder strengthened by the external prestressed tendon is set up in consideration of the prestress loss of the prestressed tendon and the advanced finite element technique (for instance, element birth and death capability). After that, this model is calibrated on the basis of the results from the field test. And finally, a series of numerical simulation analyses are performed with application of the nonlinear finite element method program Abaqus to investigate the mechanical behavior of the steel plate girder. The results show that the reinforcement scheme has great influence on the deflection of steel plate girder and the stress of steel plate girder; whereas it has little relation with the contact stress of the interface between the upper and lower I-beams and the stress of the bolt. The fracture safety factors of K2, K3, and K4 after reinforcement are 3.04, 3.76, and 3.35, respectively. It meets the primary goal of this proposed reinforcement scheme that their fracture safety factors are all greater than 3.00 under the design stress. The reinforcement scheme is good and effective, and the steel plate girder has good and stable working performance after reinforcement. It can completely meet the reinforcement design requirement of the steel plate girder. Therefore, this study can provide the technological support and the theoretical basis for engineering applications.

In this study, to satisfy the base isolation demand of large-scale building structures under different earthquake records, a new bidirectional variable curvature friction pendulum bearing (BD-VCFPB) is proposed. The VCFPB is designed in detail based on the basic principle of a friction pendulum system. Moreover, the sliding interface function, gap between the slider and the sliding interface, and polytetrafluoroethylene (PTFE) plate stress are studied. Finally, a dynamic cyclic test is conducted to study the influence of the slider size, contact pressure on the PTFE plate, and loading frequency on the hysteretic behavior of the VCFPB. The results indicate that the hysteretic curves of the horizontal force and the displacement are regular, symmetrical, stable, and full, and clearly reflect the variable curvature convex and concave characteristics and the excellent behavior of energy dissipation of the BD-VCFPB. The sliding friction coefficient varies significantly with the contact pressure on the PTFE plate and the loading frequency; however, it has little relation with the slider size. A hysteretic model is proposed based on the results of a unidirectional test, and it is in good agreement with the hysteretic curves of the horizontal force and the displacement from a bidirectional test.

The development of cost-effective bifunctional catalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is critical to realize the commercialization of electrocatalytic water splitting. Herein, an effective defect engineering strategy, Ar plasma treatment, was adopted to promote both the HER and OER activity of pre-synthesized Fe-doped Ni3S2 nano-pyramid arrays on nickel foam. The abundant sulfur vacancies endow the Fe-doped Ni3S2 nano-pyramid arrays with a low overpotential of 171 mV at 10 mA cm−2 and a small Tafel slope of 49 mV dec−1 to drive the OER in 1.0 M KOH. Density functional theory (DFT) calculations reveal that sulfur vacancies together with Fe doping can effectively regulate the electronic structure of Ni3S2, resulting in increased electrical conductivity and a reduced energy barrier, as well as enhanced reaction kinetics through weakening the binding strength between active sites and intermediates. Such defect-rich hetero-metal doped catalyst also delivers enhanced HER activity. As a result, a cell assembled using defect-rich Fe-Ni3S2 nano-pyramid arrays as both the anode and cathode needs a low applied voltage of 1.63 V to reach a current density of 10 mA cm−2, and exhibits outstanding long-term stability up to 60 h.

3D flower-like Li0.36V6O13 has been fabricated via a facile solvothermal method using C2H5OH, V2O5, and LiNO3 as raw materials. The microstructure of the sample was characterized by XRD, FESEM, TEM, and XPS. The lithium storage performance of the sample was investigated by CV, EIS, and charge/discharge test. The results demonstrated that the Li0.36V6O13 sample exhibited greatly improved electrochemical performance as compared with the pristine V6O13. For example, when cycled at 0.1 C for 50 cycles, the capacity retention of the Li0.36V6O13 is 97% much higher than that (57%) of the pristine V6O13. The improvement of the cycle performance of Li0.36V6O13 is attributed to its superior structural reversibility, fewer number of phase transitions during the discharge/charge process, improved electrical conductivity, and enhanced Li+ diffusivity.

We study the spin-dependent electronic and thermoelectric transport through a structure composed of triple quantum dots (TQDs) coupled to two metallic leads in the presence of spin-dependent interdot couplings, which is reliable by applying a static magnetic field on the tunnel junctions between different dots. When the TQDs are serially connected, a 100 % spin-polarized conductance and thermopower emerge even for very small spin-polarization of the interdot coupling as the dots are weakly coupled to each other. Whereas if the TQDs are connected in a ring shape, the Fano antiresonance will result in sharp peaks in the conductance and thermopower. In the presence of spin-dependent interdot couplings, the peaks of the spin-up and spin-down thermopowers will shift to opposite directions in the dot level regime, resulting large either 100 % spin-polarized or pure spin thermopowers. The latter generally arises at low temperatures and is robust against the level detuning, the dot-lead coupling, and the system equilibrium temperature.

Two-dimensional nanosheets and their assembles have attracted considerable attention as high-performance anode materials for Li-ion batteries because of their short transport lengths and robust structures. In this work, Fe3O4 hierarchical structures assembled by porous ultrathin nanosheets are prepared from the topochemical conversion of Fe-glycolate precursor obtained via a facile refluxing process. The flower-like hierarchical nanostructures have a size of ~ 2.5 µm constructed from ultrathin nanosheet building blocks with thickness of ca. 10 nm. When used as an anode electrode, the as-prepared Fe3O4 hierarchical nanostructures demonstrate excellent electrochemical properties with a reversible and stable capacity as high as 964.3 mAh g−1 at 500 mA g−1 after 100 cycles, and superior rate capability of 487 mAh g−1 at a high current density of 8 A g−1.

At present, the comprehensive utilization of crop straws exist the problem of the lower industrial utilization in Jilin Province, China. It’s well-known that the industrial conversion of crop straws are often used as the building wall materials and thermal insulation materials in our country. According to the above two questions, this paper elaborates the domestic research situation of crop straws that serve as building wall materials and thermal insulation materials, and summarizes the fabrication process, mechanical property and thermal performance of the crop straws as building wall materials and thermal insulation materials. Finally, the article puts forward three key problems of crop straws, which are used as the building wall materials and thermal insulation materials. I hope that this paper can provide valuable reference for speeding up the comprehensive utilization of crop straws in Jilin Province.

This paper studies the effect of mixed blowing CO2–O2 gas on the extraction of vanadium and adopts blowing flow and stage blowing, two types of variables, to study the effect of both on the extraction of vanadium from hot iron. The initial blowing temperature of the experiment was set to 1300 °C. The experimental results showed that the whole process is sprayed with 15% CO2, and the optimum blowing flow rate is 1.714 L/(min kg). The stage blowing has better vanadium extraction with carbon retention effect, compared with the whole blowing of 10% CO2, and the end point temperature of the molten pool is decreased by 17 °C. The stage blowing is injecting 10% CO2 in the initial and injecting 15% CO2 in the middle and late period. And it has a higher vanadium oxidation rate than the whole blowing 10% CO2, which can reach 95.14%.

Calcium-ion batteries are promising candidate as alternative to lithium-ion batteries with appealing features of abundant resource and high theoretical specific capacity up to 1337 mAh g−1. However, the development of calcium-ion batteries is primarily hindered by the lack of satisfactory electrode materials due to the large radius and charge density of calcium ion. Herein, we report the reversible calcium ion intercalation in layered potassium vanadate K2V6O16·2.7H2O as stable cathode with impressive electrochemical performance for Ca ion battery. The potassium vanadate nanowires obtained by facile hydrothermal process (typical lengths of 0.5–1.5 μm, widths of 70–100 nm) deliver a high initial capacity of 113.9 mAh g−1 at current density of 20 mA g−1 and high capacity retention of 78.30% at 50 mA g−1 after 100 cycles. In addition, the reversible intercalation of calcium ion in this layered potassium vanadate material with stable crystal structure is verified by ex-situ XPS and XRD techniques, demonstrating that layered K2V6O16·2.7H2O could be a potential cathode material for calcium-ion batteries.

The influence of bottom blowing a CO2–O2 mixture on the bath temperature of a vanadium extraction converter was studied by using the characteristics of CO2 with weak oxidizing. It was studied in two aspects: oxygen content and temperature. The experiments showed, when the ratio of the mixture of CO2–O2 was 2:8 at 1300 °C, the bottom blowing of the converter inhibited the heating up of the hot metal, thus keeping the temperature below the carbon vanadium transition temperature. At 1360 °C, the sensible heat absorption by CO2 was 1.44 times that absorbed by O2 per mole. Meanwhile, at 1300 °C, 20% CO2 released the chemical heat of 13.58 kJ. So with the increase of the CO2 ratio, the bath temperature was reduced. The research showed that the bottom blowing of a CO2–O2 mixture had an advantageous effect by decreasing the temperature of the vanadium extraction converter.

The aim of this experimental study is to improve gray cast iron fatigue wear resistance through laser cladding carbon – a proposed process referred as “laser carburizing”. Optimization of laser carburizing processing conditions is achieved by studying the effects of input energy density on sample fatigue wear resistance. Following laser deposition, details of treated regions are experimentally investigated and compared. Fatigue wear tests are separately executed in an air atmosphere. Results demonstrate that laser carburizing is a more effective means of improving fatigue wear resistance than laser remelting and that the improvement is significantly affected by increase in energy density during treatment. Examinations of worn surface reveal the mechanisms of improvement: the unit not only removes the source of crack initiation, but also eliminates the bridging of cracks throughout the material. To further understand the mechanisms of fatigue wear resistance improvement, contact stresses distributions on sample surfaces are predicted using Finite Element Analysis.

To improve the fatigue wear resistance of gray cast iron (GCI), GCI samples were modified by a laser to imitate the unique structure of some soil animals alternating between soft and hard phases; the hard phase resists the deformation and the soft phase releases the deformation. Using the self-controlled fatigue wear test method, the fatigue wear behaviors of treated and untreated samples were investigated and compared experimentally. The results show that the bionic non-smooth surface obtains a beneficial effect on improving the fatigue wear resistance of a sample, and the fatigue wear resistance of the bionic sample assembled with reticulate units (60°+0°), whose mass loss was reduced by 62%, was superior to the others. Meanwhile, a finite element (FE) was used to simulate the compression and the distributions of strain and stress on the non-smooth surface was inferred. From these results, we understood that the functions of the bionic unit such as reducing strain and stress, and also obstructing the closure and propagation of cracks were the main reasons for improving the fatigue wear property of GCI.

In order to study the dynamic response characteristics and damage effect of reinforced concrete beams in an adjacent physical field of explosion, in this study, three groups of nine 1:6 scale models of reinforced concrete beams are subjected to blast loads. All factors, such as the weight of explosive charge, distance from the model to the explosion center (including the contact explosion), and position of explosive charge are all considered. Thereafter, the pressures, displacements, accelerations, and strains are introduced at certain typically measured points to investigate the dynamic response characteristics as well as the local state of these models that have been subjected to the blast. And then, a monotonic loading test is conducted to assess the damage of these models. Finally, a series of numerical simulation analyses are conducted on the reinforced concrete beams that have been subjected to blast load. Results show that the damage index increases as the scaled distance decreases, and moreover, the models that have been subjected to the blasts from larger amount of explosive charges suffer extensive destruction; the models that have been exposed to the blasts from smaller amounts of explosive charges experience severe local damage. As the explosive charge is moved away from the mid-span to the beam column joints, the damage index in the reinforced concrete beam gradually decreases. The influence of different parameters (compressive strength of concrete, section size, longitudinal reinforcement ratio, and transverse reinforcement ratio) on the damage change law of reinforced concrete beams is different, and the failure mode of reinforced concrete beam is severely effected by the section sizes, particularly in the height of the beam. The results prove that the blast resistance of reinforced concrete beam is greatly affected by the column. Accordingly, the results of this study can be used as technological support and theoretical basis for engineering applications.

We report experimental investigation on photoacoustic emission from air plasma created as a result of interaction of a focused 50 fs intense laser-pulse in air. Emphasis is to study the dependence of acoustic emissions on laser energy, radial distance and laser polarization direction. Experimental results indicate quadratic dependence on laser energy, reciprocal dependence on radial distance and independence on laser polarization direction of photoacoustic emissions from strong femtosecond-laser-induced air plasma.

The Bi0.5Na0.02Sb1.48−x In x Te3 alloys (x = 0.02–0.20) were synthesized by vacuum melting and hot pressing methods at 753 K, 60 MPa for 30 min. Effects of Na and In dual partial substitutions for Sb on the thermoelectric properties were investigated from 300 to 500 K. Substituting Sb with Na and In can enhance the Seebeck coefficient effectively near room temperature. The electrical resistivity of the Na and In dual-doping samples is higher within the whole test temperature range. The Bi0.5Na0.02Sb1.48−x In x Te3 samples (x = 0.02, 0.06) play a great role in optimizing the thermal conductivity. As for the Bi0.5 Na0.02Sb1.46In0.02Te3 alloy, the minimum value of thermal conductivity reaches 0.53 W·m−1·K−1 at 320 K. The thermoelectric performance of the Na and In dual-doped samples is greatly improved, and a figure of merit ZT of 1.26 is achieved at 300 K for the Bi0.5Na0.02Sb1.42In0.06Te3, representing 26 % enhancement with respect to ZT = 1.0 of the undoped sample.

The Shear capacities of fourteen coupling beams are analyzed in this research by the finite element numerical simulation method. The coupling beams are designed with small span-to-depth ratios and arranged high strength steel. The results show that the shear capacities of coupling beams accord with the compression strut model. The shear capacities improve obviously through enhancing the diagonal steel bars, but they do not show significant influence through changing the strength of transverse and longitudinal bars. Comparing the results calculated by the formulas shown in the Code for Design of Concrete Structures (GB50010-2010), the results calculated by the finite element method show the gap, and it will be the key issue for further study.

Nano-Fe3O4 powders were prepared by chemical co-precipitation method. The granularity, morphology and absorbing properties of the magnetite nanoparticles were characterized by XRD, SEM, TEM and complex permeability. The effects of organic additives to the granularity, morphology and microwave absorption property of nanosized magnetic Fe3O4 were studied. The results show that the organic additives have great influence on the morphology of nano-Fe3O4 particles. Spherical nano-Fe3O4 is prepared by oxalic acid. And the absorption property of nano-Fe3O4 is better.

A new HTc rf SQUID working at around 1.3GHz has been developed to avoid electromagnetic interference such as growing mobile communication jamming. This new system works in a frequency range from 1.23 to 1.42GHz (centred at 1.3GHz), which is not occupied by commercial communication. The sensor used in the 1.3GHz rf SQUID is made of a HTc coplanar superconducting resonator and a large-area HTc superconducting film concentrator. We have achieved in the 1.3GHz HTc rf SQUID system a minimal flux noise of 2.5×10−5Φ0/(Hz)1/2 and a magnetic field sensitivity of 38fT/(Hz)1/2 in white noise range, respectively. The effective area of the concentrator fabricated on a 15×15mm2 substrate is 1.35mm2. It is shown that the 1.3GHz rf SQUID system has a high field sensitivity. Design and implementation of 1.3GHz HTc rf SQUID offers a promising direction of rf SQUID development for higher working frequency ranges.

It is well known that the terrestrial temperature varies with the period of 24 hours mainly due to the rotation of the earth in the field of the solar radiation. However, we observed the phenomenon that the semidiurnal (12 hour) temperature oscillation is dominant in our underground laboratory. By the spectrum analysis, the close correlation between the variations of temperature and atmospheric pressure was discovered, and the result of phase analysis showed that the phase of semidiurnal pressure lags behind that of the semidiurnal temperature. A model of heat conduction between air and rock is presented to explain the semidiurnal temperature oscillation observed in the underground laboratory.

The Gd-Co films reported here were prepared by radio frequency sputtering and have been proved to have uniaxial anisotropy perpendicular to the film plane. Electron diffraction results show that these films are amorphous. Also, electron probe analyses show that these films are of uniform composition. Magnetic domains have been observed and hysteresis loops measured, using Kerr's apparatus. It was found that with suitable sputtering conditions, at remanence such films exhibit stripe domains, which, when acted on by a suitable external field perpendicular to the film plane, can transform into bubble domains.