A new way of strengthening and toughening for carbon fiber reinforced polyphenylene sulfide (CF/PPS) composites via matrix modification

The effect of pressure-induced flow(PIF) processing on the mechanical properties of noncontinuous carbon fiber(CF) reinforced polyphenylene sulfide(PPS) composites was investigated. A series of CF/PPS composites under different processing conditions were prepared through PIF-processing. SEM observations showed that the interfaces adhesion between CFs and PPS became stronger and ductile fracture mainly occurred in PPS matrix. This brought to a great increase of both strength and toughness by about 2 folds, when the composites were processed at 240 ℃ and under 263 MPa. The results in differential scanning calorimetry(DSC) and X-ray diffraction(XRD) measurements indicated more regular crystalline structures and orientation of lamellae formed during PIF-processing.     

Effect of fly ash on drying shrinkage of thermal insulation mortar with glazed hollow beads

Drying shrinkage of thermal insulation mortar with glazed hollow beads was measured by a vertical length comparator, and the influences of fly ash with different contents (0, 18%, 36%, and 54% were used) on the long-term drying shrinkage were discussed. The mass loss was measured by the weighting method and the pore structure was characterized using three different methods, including the light microscopy, the mercury intrusion porosimetry (MIP), and the nitrogen adsorption/desorption (NAD) experiments, and the correlations among them were researched. The results show that drying shrinkage process of thermal insulation mortar includes three steps with increasing curing time: the acceleration period (before 7 d), the deceleration period (7-365 d), and the metastable period (after 365 d). Drying shrinkage in the first stage (7 d before) increases quickly owing to the fast water loss, and its development in the last two stages is attributed to the increment of the pore volume of mortar with the radius below 50 nm, especially the increment of the pore volume fraction of the pore radius within the size range between 7.3 nm and 12.3 nm. There is no change in the drying shrinkage development trend of mortar with fly ash addition, and three steps in the service life, but fly ash addition in the mortar restrains its value. There is a linear relationship between the drying shrinkage and fly ash content, which means that drying shrinkage reduces with fly ash addition.     

Growth and characterization of indium doped zinc oxide films sputtered from powder targets

Indium doped Zn O films were grown on quartz glass substrates by radio frequency magnetron sputtering from powder targets. Indium content in the targets varied from 1at% to 9at%. In doping on the structure, optical and electrical properties of Zn O thin films were studied. X-ray diffraction shows that all the films are hexagonal wurtzite with c-axis perpendicular to the substrates. There is a positive strain in the films and it increases with indium content. All the films show a high transmittance of 86% in the visible light region. Undoped Zn O thin film exhibits a high transmittance in the near infrared region. The transmittance of indium doped Zn O thin films decreases sharply in the near infrared region, and a cut-off wavelength can be found. The lowest resistivity of 4.3×10~(-4) Ω·cm and the highest carrier concentration of 1.86×10~(21) cm~(-3) can be obtained from Zn O thin films with an indium content of 5at% in the target.     

充电法和高密度电法在典型岩溶区勘查中的应用分析

查明贵港地区地下岩溶的发育状况,对当地的建设具有重要的意义。在岩溶区勘查中较常用的物探方法有充电法和高密度电法,首先概述了两种方法的工作原理、装置类型和观测方式;然后通过两处实例说明了联合应用充电法和高密度电法可以确定地下岩溶连通管道的位置和流通方向,高密度电法在典型岩溶区能给出第四系厚度、地层分层、岩溶发育情况、岩溶底部埋深深度等,并通过钻孔验证了探测的准确性。结果表明,充电法和高密度电法均具有较简单的观测方式、较高的工作效率和较直观的解译结果,值得在岩溶勘查中广泛应用。     

图案化电极的离子聚合物金属复合物扭转特性研究

以商业膜和自制梯度膜为基膜,采用化学镀的方式得到图案化电极的离子聚合物金属复合物(IPMC),分析其扭转特性。在直流电压驱动下,梯度膜IPMC可实现扭转角度大于商业膜IPMC可实现扭转角度;当直流电压为5V时,梯度膜IPMC扭转角度是商业膜IPMC最大扭转角度的5倍多。在交流电压驱动下,扭转角度随着电压逐渐增大而增大;当交流电压为5V时,梯度膜IPMC最大扭转角度是商业膜IPMC最大扭转角度的2倍多。     

Overall efficiency optimization of controllable mechanical turbo-compounding system for heavy duty diesel engines

A controllable mechanical turbo-compounding (CMTC) system including continuously variable transmission (CVT) and power turbine bypass valve is proposed to recover waste heat from engine exhaust. The combined matching principle considering swallowing capacity of both charging turbine and power turbine, main gear ratio is investigated at first based on the analysis of individual influence. Then the effects and strategies of CVT and power turbine bypass valve are studied for better performance under off-design conditions. At last, the transient response of intake pressure of engine with CMTC system is researched and the fuel saving potential is tested under driving cycle conditions. The results indicate that the overall fuel efficiency elevates at the off-design conditions if CVT is adopted due to the improvement of power turbine operating efficiency by speed modulation. The diversion of exhaust through power turbine bypass valve under the low load condition is necessary. The back pressure of the charging turbine infuences the transient response of intake pressure for a fixed CMTC configuration. A method featured by the assistance of power turbine bypass valve is tested to improve the transient response of the intake pressure. The fuel consumption reduces by 2% and 3.4% under highway fuel economy test (HWFET) and Tianjin 503 (TJ503) driving cycles respectively.     

Load identification in one dimensional structure based on hybrid finite element method

The new hybrid elements are proposed by combing modified Hermitian wavelet elements with ANASYS elements. Then hybrid elements are substituted into finite element formulations to solve the load identification. Transfer matrix can be constructed by using the inverse Newmark algorithm and hybrid finite element method. Loads can obtain through the responses and the transfer matrix. Load identification law was studied under different excitation cases in rod and Timoshenko beam. Regularization method is adopted to solve ill-posed inverse problem of load identification. Compared with ANSYS results, hybrid elements and HCSWI elements can accurately identify the applied load. Numerical results show that the algorithm of hybrid elements is effective. The accuracy of hybrid elements and HCSWI elements can be verified by comparing the load identification result of ANASYS elements with the experiment data. Hermitian wavelet finite element methods have high accuracy advantage but it is difficult to apply the engineering practice. In practical engineering, complex structure can be analyzed by using the hybrid finite element methods which can be obtained the high accuracy in the crucial component.     

Adaptive fuzzy sliding mode control for coordinated longitudinal and lateral motions of multiple autonomous vehicles in a platoon

In this paper, the platoon control problem of autonomous vehicles in highway is studied. Since the autonomous vehicles have the characteristics of nonlinearities, external disturbances and strong coupling, a novel adaptive fuzzy sliding coordinated control system is constructed to supervise the longitudinal and lateral motions of autonomous vehicles, in which the fuzzy system is employed to approximate the unknown nonlinear functions. Due to the low sensitivity to disturbances and plant parameter variations, the proposed control approach is an efficient way to handle with the complex dynamic plants operating under un-certainty conditions. The asymptotic stability of adaptive coordinated platoon close-loop control system is verified based on the Lyapunov stability theory. The results indicate that the presented adaptive coordinated platoon control approach can accurately achieve the tracking performance and ensures the stability and riding comfort of autonomous vehicles in a platoon. Finally, simulation test is exploited to demonstrate the effectiveness of the proposed control approach.     

Indoor and outdoor particle concentration distributions of a typical meeting room during haze and clear-sky days

Air quality has increasingly been a great concern all over the world, and the good command of indoor and outdoor air qualities is of benefit to the air pollution alleviation by various measures. In this work, the indoor and outdoor particle concentration distributions of a typical meeting room during the haze and clear-sky days were measured. The results show that the mass concentrations of the indoor and outdoor PM₁, PM_2.5, PM10 in heavy haze days are 114±1.8, 135.5±3.2, 161.7±12.8 μg/m³ and 146.4±8.4, 192.3±10.2, 431.4±34.8 μg/m³ respectively, corresponding to 39.3±1.5, 58.5±2.5, 127.9±10.5 μg/m³ and 54.5±4.0, 77.8±6.0, 173.4±21.6 μg/m³ in clear-sky days. Both in the haze and clear-sky days, the number distribution of particles reaches its peak value at the diameter of 0.25 μm, but the particle number concentration in the haze day is two times greater than the clear-sky day. The indoor particle concentration is not uniform with the peak value at the corner, which can be effectively alleviated by the air cleaner. The in-situ measurements of particle concentrations in a meeting room are helpful for the indoor air quality control.     

Optimization of uncertain acoustic metamaterial with Helmholtz resonators based on interval model

Uncertainties existing in the acoustic metamaterial may strongly affect its unusual properties. Aiming at this actuality, the interval model is introduced to treat with uncertainties existing in the acoustic metamaterial with Helmholtz resonators. Frequency intervals in which the sound intensity transmission coefficients are certainly less than the required value and the effective bulk moduli are certainly negative are defined as conservative approximations. Frequency intervals in which the sound intensity transmission coefficients may be less than the required value and the effective bulk moduli may be negative are defined as unsafe approximations. The proportion of the conservative approximation and the unsafe approximation is defined as an approximate precision. Based on the quantification of uncertainties of the sound intensity transmission coefficients and the negative effective bulk moduli, an optimization model for the interval acoustic metamaterial with Helmholtz resonators is constructed. Numerical results showed that even suffering from effects of interval parameters, unusual properties of the optimized acoustic metamaterial (such as the bandgap of the sound transmission and the negative effective bulk modulus) could be improved.