Anti-penetration performance of high entropy alloy–ceramic gradient composites

A high-entropy alloy–ceramic gradient composite of TiC–TiB_2/75vol% Al_(0.3) CoCrFe Ni was successfully prepared by combustion synthesis under an ultra-high gravity field, which is a low-cost method with high efficiency. The ceramic particles were gradient distributed in the Al_(0.3) CoCrFe Ni matrix, and the hardness of the composite material gradually decreased along the thickness direction. The anti-penetration performance of the gradient composites was simulated using the ANSYS/LS-DYNA explicit simulation program. The results demonstrate that the distribution of the ceramic particles strongly affected the mechanical properties and the anti-penetration performance of the composites. With the same total ceramic volume fraction, the gradient composites exhibit better anti-penetration performance than the corresponding ceramic–metal interlayer composites. The more uneven the ceramic distribution, the greater the elastic modulus and yield stress of the surface layer and, thus, the better the anti-penetration performance.

Preparation technology and anti-corrosion performances of black ceramic coatings formed by micro-arc oxidation on aluminum alloys

In order to prepare ornamental and anti-corrosive coating on aluminum alloys, preparation technology of black micro-arc ceramic coatings on Al alloys in silicate based electrolyte was studied. The influence of content of Na2WO4 and combination additive in solution on the performance of black ceramic coatings was studied; the anticorrosion performances of black ceramic coatings were evaluated through whole-immersion test and electrochemical method in 3.5% NaCl solution at different pH value; SEM and XRD were used to analyze the surface morphology and phase constitutes of the black ceramic coatings. Experimental results indicated that, without combination additives, with the increasing of Na2WO4 content in the electrolyte, ceramic coating became darker and thicker, but the color was not black; after adding combination additive, the coating turned to be black; the black ceramic coating was multi-hole form in surface. There was a small quantity of tungsten existing in the black ceramic coating beside α-Al2O3 phase and β-Al2O3 phase. And aluminum alloy with black ceramic coating exhibited excellent anti-corrosion property in acid, basic and neutral 3.5% NaCl solution.

Seismic performance evaluation of an infilled rocking wall frame structure through quasi-static cyclic testing

Earthquake investigations have illustrated that even code-compliant reinforced concrete frames may suffer from soft-story mechanism.This damage mode results in poor ductility and limited energy dissipation.Continuous components offer alternatives that may avoid such failures.A novel infilled rocking wall frame system is proposed that takes advantage of continuous component and rocking characteristics.Previous studies have investigated similar systems that combine a reinforced concrete frame and a wall with rocking behavior used.However,a large-scale experimental study of a reinforced concrete frame combined with a rocking wall has not been reported.In this study,a seismic performance evaluation of the newly proposed infilled rocking wall frame structure was conducted through quasi-static cyclic testing.Critical joints were designed and verified.Numerical models were established and calibrated to estimate frame shear forces.The results evaluation demonstrate that an infilled rocking wall frame can effectively avoid soft-story mechanisms.Capacity and initial stiffness are greatly improved and self-centering behavior is achieved with the help of the infilled rocking wall.Drift distribution becomes more uniform with height.Concrete cracks and damage occurs in desired areas.The infilled rocking wall frame offers a promising approach to achieving seismic resilience.

Anti-Noise Performance of the FT Continuous Zoom Analysis Method for Discrete Spectrum

As a discrete spectrum correction method, the Fourier transform （FT） continuous zoom analysis method is widely used in vibration signal analysis, but little effort had been made on this method＇s anti-noise performance. It is widely believed that the analysis accuracy of the method can be substantially improved by increasing the zoom multiple, however, with the zoom multiple increases, the frequency estimation accuracy may decline sometimes in practices. Aiming at the problems above, this paper analyzes the sources of frequency estimation error when a harmonic signal mixed with and without noise is processed using the FT continuous zoom analysis. According to the characteristics that the local maximum of the zoom spectrum may be wrongly selected when the signal is corrupted with noise, the number of wrongly selected spectrum lines is deduced under different signal-to-noise ratio and local zoom multiple, and then the maximum frequency estimation error is given accordingly. The validity of the presented analysis is confirmed by simulations results. The frequency estimation accuracy of this method will not improve any more under the influence of noise, and there is a best zoom multiple, when the zoom multiple is larger than the best zoom multiple; the maximum frequency estimation error will fluctuate back and forth. The best zoom multiple curves under different signal-to-noise ratios given provide a theoretical basis for the choice of the appropriate zoom multiples of the FT continuous zoom analysis method in engineering applications.

Performance Analysis of RFID Framed Slotted Aloha Anti-Collision Protocol

In this paper, we develop a novel mathematical model to estimate the probability distribution function of the number of tags discovered after a certain number of interrogation rounds. In addition, the pdfs of the number of rounds needed to discover all the tags are also calculated. The estimation of such pdfs will be helpful in estimating the number of interrogation rounds and the optimal parameter configuration of the RFID system which in turn will be helpful in estimating the time needed to discover all tags. Our results show that the proposed model accurately predicts the tags detection probability. We then use the proposed model to optimally configure the reader parameters (i.e. the frame size and the number of interrogation rounds).

Influence of graphene on the anti-corrosion performance of epoxy-based coatings

In this work, graphene-modified epoxy-based anti-corrosion coatings were prepared and the influence of graphene on the anti-corrosion performance of the epoxy-based coatings was investigated with water contact angle test ,chemical solution immersion test, and electrochemical test. The water contact angle and chemical solution resistance of the epoxy-based coatings were improved with an increase in graphene content from 0 to 0.4%. These results prove that addition of graphene can significantly improve the hydrophobicity and impermeability of epoxy- based coatings. However, when the graphene content was increased to 0.5%, the performance of the epoxy-based coatings decreased because of graphene aggregation. Tafel polarization results show that graphene addition can significantly reduce the corrosion current density and corrosion potential of epoxy-based coatings, which enhance their anti-corrosion performance.

Design of Small Stone Asphalt Mixture based on Anti-skidding Performance

Small stone asphalt mixture（SSAM） was designed by Bailey method and coarse aggregate voids-filling method.The optimum asphalt content was determined by Marshal test.Surface texture depth for SSAM with different voidage,and the BPN of SSAM and SMA before after wet track abrasion were measured.The experimental results indicate that the surface texture depth increases with the decreasing of asphalt aggregate ratio.The SSAM with the optimal asphalt content has a good skid resistance.BPN of asphalt mixture decreases with the increasing of wearing time,but the extent of reduction is different.The reduction rate of BPN for SSAM is smaller than that of SMA,indicating that SSAM has a good skid resistance attenuation capacity.Finally,the other properties of SSAM are also evaluated,showing that the splitting strength and modulus and SSAM are higher than those of SMA,and the other properties of SSAM,such as high-temperature performance and water stability can also satisfy the technical requirements.

Effects of Fatigue Characteristics on Static and Dynamic Performance of Eucommia Rubber Isolators

This study aimed to investigate the effect of fatigue characteristics on the static and dynamic performance of Eucommia ulmoides gum isolators, and to explore the performance changes of Eucommia ulmoides gum isolators with different formulations. For this purpose, we used five formulations of Eucommia ulmoides gum isolators and set different fatigue test methods to study the static and dynamic performance changes of Eucommia ulmoides gum isolators with different formulations by changing the amplitude. The experimental results showed that the addition of Eucommia ulmoides gum had an impact on the performance of the isolator, and the number of fatigue cycles would lead to the hardening of the Eucommia ulmoides gum isolator and changes in its static and dynamic performance. In the range of two million vibrations, the performance change of the isolator was significant in the early stage and then tended to be flat, indicating that the impact of fatigue on the performance of the isolator would not continue to persist. It is worth noting that the study found that the addition of 30% Eucommia ulmoides gum had the least impact on the performance of the isolator under fatigue. Therefore, for long-term use of Eucommia ulmoides gum isolators, attention should be paid to their fatigue characteristics to ensure their stability and reliability. Additionally, this study provides a reference for the design and application of Eucommia ulmoides gum isolators. In summary, this study provides important reference value for a deeper understanding of the fatigue characteristics of Eucommia ulmoides gum isolators and for ensuring their stable and reliable performance. .

PREDICTION OF RIME ICE ACCRETION AND RESULTING EFFECT ON AIRFOIL PERFORMANCE

The roughness effect based on the wall function method is introduced into the numerical simulation of the rime ice accretion and the resulting effect on the aerodynamic performance of the airfoil. Incorporating the two-phase model of air/super-cooled droplets in the Eulerian coordinate system, this paper presents the simulation of the rime ice accretion on the NACA 0012 airfoil. The predicted rime ice shape is compared with those results of measurements and simulations by other icing codes. Also the resulting effects of rime ice on airfoil aerodynamic performance are discussed. Results indicate that the rime ice accretion leads to the loss of the maximum lift coefficient by 26%, the decrease of the stall angle by about 3° and the considerable increase of the drag coefficient.

Adsorption Performance of Activated Carbon Prepared from Corn Stalks

[Objective] This study aimed to study the adsorption performance of activated carbon prepared from corn stalks. [Methed] With granular activated carbon prepared from corn stalks as research object, adsorption performance simulation test equipment was set up to investigate the adsorption performance of the prepared activated carbon for methanol by static weight method. In addition, the effects of adsorption bed structure, activated carbon particle size in adsorption bed, addition amount of graphite powder in activated carbon and modified activated carbon on systematic adsorption performance were studied. [Result] Under conditions of same activated carbon and same adsorption temperature, the adsorption performance of new adsorption bed A （installed with finned diaphragm adsorbate tubes） was signifi- cantly better than that of unmodified adsorption bed B. Compared with adsorption bed B, adsorption bed A took 5 min shorter to reach the adsorption amount of 0.22 g/g. Under the same adsorption temperature, the adsorption performance of bed loaded with different-particle size activated carbon was significantly better than that loaded with same-particle size activated carbon. The bed loaded with different-particle size activated carbon took 16 min shorter to reach the adsorption capacity of 0.22 g/g compared with the bed loaded with same-particle size activated carbon. Adding proper amount of graphite powder in activated carbon could enhance the thermal conductivity and strengthen the adsorption properties. The optimum addition amount of graphite powder was 20% of the total amount of activated carbon. Com- pared with that of the control, the adsorption performance of activated carbon soaked by weak acidic solution was significantly improved. It took 3 min shorter to reach 87.1% of the equilibrium adsorption amount. [Conclusion] This study will provide reference for optimizing structural design of adsorption bed and adsorption refrigeration system.

Cyclic test and numerical study of seismic performance of precast segmental concrete double-columns

The comparative research on the seismic performance of grouted sleeve connected pier(GS)and prestressed precast segmental concrete pier(PC)is mostly carried out by numerical simulation.In this study,the GS pier and the PC pier of the new railway project from Hetian to Ruoqiang are taken into consideration.Two kinds of 1/5-scale assembled double-column specimens are made,and the quasi-static tests are carried out.The overall seismic performance of the two spliced piers is studied,and compared in terms of failure mechanism,bearing capacity,ductility,stiffness and energy dissipation capacity.The results show that the failure modes of both GS pier and PC pier are characterized by bending.However,the specific failure location and form are different.The GS pier presents a complete hysteretic curve,large equivalent stiffness and strong energy dissipation capacity.The hysteretic area of the PC pier is small.However,it has good self-reset ability and quasi-static residual displacement.Finite element models are set up using DispBeamColumn fiber elements and ZeroLength elements.The models that are calibrated with the test data can effectively simulate the damage development under monotonic loading.The load−displacement curves are in good agreement with the backbone curves of the test results.

Experimental and numerical study on hysteretic performance of SMA spring-friction bearings

This paper presents an experimental and numerical study to investigate the hysteretic performance of a new type of isolator consisting of shape memory alloy springs and friction bearing called an SMA spring-friction bearing （SFB）. The SFB is a sliding-type isolator with SMA devices used for the seismic protection of engineering structures. The principle of operation of the isolation bearing is introduced. In order to explore the possibility of applying SMA elements in passive seismic control devices, large diameter superelastic tension/compression NiTi SMA helical springs used in the SFB isolator were developed. Mechanical experiments of the SMA helical spring were carried out to understand its superelastic characteristics. After that, a series of quasi-static tests on a single SFB isolator prototype were conducted to measure its force-displacement relationships for different loading conditions and study the corresponding variation law of its mechanical performance. The experimental results demonstrate that the SFB exhibits full hysteretic curves, excellent energy dissipation capacity, and moderate recentering ability. Finally, a theoretical model capable of emulating the hysteretic behavior of the SMA-based isolator was then established and implemented in MATLAB software. The comparison of the numerical results with the experimental results shows the efficacy of the proposed model for simulating the response of the SFB.

Seismic performance evaluation procedure of asymmetric plan structures

Plan asymmetry leads to lateral-rotational coupled effects on structural response characteristics.This investigation deals with a simplified method for performance estimation of structures with asymmetric plan.By taking the eccentric characteristics of structures into account,an equivalent triple-degree of freedom (ETDOF) system,which is constructed by eccentric mass,rigid links and springs,is proposed.The modal pushover analysis (MPA) method for asymmetric plan structures is proposed.The target displacement is determined by constant strength spectrum.The applicability of proposed method is discussed.A generic mass eccentric 4-story steel frame is analyzed by the proposed MPA procedure and nonlinear time history analysis (NTHA).The results show that the maximum deformation obtained from MPA has a good agreement with the NTHA results.The proposed MPA procedure is reliable and effective for evaluating the performance of asymmetric plan structures.

Preparation of High Performance Non-dispersible Concrete

A new-type underwater non-dispersible concrete admixture NDA was prepared,its function mechanism was analyzed,and C40 high performance non-dispersible underwater concrete was manufactured by applying NDA.The results indicate that NDA has a suitable workability,low strength loss,and excellent anti-dispersion;the fresh non-dispersible underwater concrete with NDA has high anti-dispersion,excellent workability such as self-compacting and not bleeding;hardened non-dispersible underwater concrete with NDA has a high strength,high durability such as high anti-abrasion,impermeability and anticorrosion.

A simplified methd of evaluating the seismic performance of buildings

This paper presents a simplified method of evaluating the seismic performance of buildings. The proposed method is based on the transformation of a multiple degree of freedom (MDOF) system to an equivalent single degree of freedom (SDOF) system using a simple and intuitive process. The proposed method is intended for evaluating the seismic performance of the buildings at the intermediate stages in design, while a rigorous method would be applied to the final design. The performance of the method is evaluated using a series of buildings which are assumed to be located in Victoria in western Canada, and designed based on the upcoming version of the National Building Code of Canada which is due to be published in 2005. To resist lateral loads, some of these buildings contain reinforced concrete moment resisting frames, while others contain reinforced concrete shear walls. Each building model has been subjected to a set of site-specific seismic spectrum compatible ground motion records, and the response has been determined using the proposed method and the general method for MDOF systems. The results from the study indicate that the proposed method can serve as a useful tool for evaluation of seismic performance of buildings, and carrying out performance based design.

THE STATIC PERFORMANOE AND PARAMETER STUDY OF FLOATING-RING HYDRODYNAMIC THRUST BEARINGS

In this paper, floating--ring thrust bearings are investigated. A mathematical model is established to analyze the static performance of this kind of bearings, such as the load capacity, frictional power loss, temperature rise as well as the angular speed ratio between the floating ring and runner.Meanwhile, a parameter study is also conducted on the characteristics of floating-ring thrust bearings.Finally, the theoretical calculation results are verified by experiments.

Preparation and Application of Anionic and Cationic Waterborne Polyurethanes and Graphene-Cellulose Nanocrystal as an Antistatic Agent for Cashmere

The main purpose of this research work is to improve anti-static properties of Cashmere fabric by introducing application comprising anti-static agent by foaming which was made with cationic waterborne polyurethane and graphene-CNC. Cashmere fabric was cut into 10 pieces of sample cloth of 5 cm * 5 cm size, washed with acetone solution, and then dried in an oven at 60℃. Three forms of waterborne polyurethanes such as two forms of Cationic waterborne polyurethane (CWPU) and a form of Anionic waterborne polyurethane (AWPU) were synthesized. Cellulose nanocrystalline (CNC)/graphite powder solution with the ratio of 0.5/1, 1/1, 2/1 was prepared by ultrasonic probe stripping method, and the concentration of graphite powder was ensured to be 1 mg/ml. The fabric was treated with anionic and cationic WPUs foaming solution until the weight gain reached 2.5 - 3.5 wt%. After drying, the elastic cloth was foamed with graphene solution until the graphite content of the cloth was close to 10%, 20%, 40%, 60% respectively, and then dried for reserving. Characterization properties of pure graphite powder, pure CNC and graphene solution with different proportions of three components were tested by Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD), Thermalgravitimetric analysis (TGA) and scanning electron microscopy (SEM). Take the original cloth, only WPU treated cloth and four clothes with different graphite content for the fabric performance test.

Fuzzy Comprehensive Analysis of Static Mixers Used for Selective Catalytic Reduction in Diesel Engines

The proper selection of a relevant mixer generally requires an effective assessment of several models against theapplication requirements. This is a complex task, as traditional evaluation methods generally focus only on a single aspect of performance, such as pressure loss, mixing characteristics, or heat transfer. This study assesses aurea-based selective catalytic reduction (SCR) system installed on a ship, where the installation space is limitedand the distance between the urea aqueous solution injection position and the reactor is low;therefore, the staticmixer installed in this pipeline has special performance requirements. In particular, four evaluation indices areused in this study: The B value, C value, pressure loss correction factor (Z′), and the ratio of the required distanceto the equivalent diameter of the pipe (LV/D) when the velocity field after the mixer attains uniformity. Six typesof static mixers were simulated with varying concentrations, flow speeds, and positions. A fuzzy comprehensiveevaluation method was introduced to evaluate and compare the related advantages and disadvantages. The resultsshowed that 1) mixing performance was related to the shape of the mixer and had no direct relationship with flowvelocity. 2) For the same mixer position, the lower the urea concentration, the greater the difficulty of evenly mixing the solution. 3) At a constant urea concentration, the mixing performance improved when the mixer was closer to the injection inlet. 4) The installation of a GK mixer in the SCR system of a 9L20C diesel engine was best.

Lubricating Performance of Rapeseed Oil Under Electromagnetic Field

Considering electromagnetic effect when investigating tribological properties of rapeseed oil is benefical not only to the improvement of green lubrication, but also to the development of tribology theories and practices. In the present paper, the tribological properties of rapeseed oil under different intensity of electromagnetic field and normal loads were evaluated on a modified tribo-tester. The results indicated that the electromagnetic field could improve the anti-wear and friction-reducing property of the rapeseed oil. Furthermore, the influencing mechanisms were discussed from the perspective of electromagnetism according to the analytical results of SEM, EDS and XPS techniques.