Abstract:

Abstract: The carbon quantum dots ( CQDs) colloid solution was prepared by electrolyzing graphite with pulsecurrent. The shape, size, structure and performance of the carbon quantum dots were characterized by trans-mission electron microscopy, X -ray diffractometer, Fourier transform infrared spectroscopy and fluorescencespectroscopy , etc. The CQDs were quasi-spherical particles with an average particle size of 6.93 nm, and thesurface contained a variety of oxygen-rich functional groups and showed fluorescence characteristics. The cyto-toxicity test showed that the colloid solution could induce the apoptosis of human hepatoma cells ( HepG2cells) , and thus could effectively inhibit the proliferation of the cells, when the concentration of CQDs colloidsolution was above a certain value. Transmission electron microscopy images of HepG2 cells after apoptosis in-duced by CQDs showed that their mitochondria were damaged. There was almost no effects on human lympho-cytes in the same CQDs concentration range. The CQDs colloid solution has the effect of selectively inducingapoptosis of HepG2 cells, which is of great significance for the research of new anti-cancer drugs without sideeffects.

Abstract: ZTA/TiC composite ceramics were prepared by using 3 μm α-Al2O3 particles as main raw material, supplemented by nano-materials such as Al2O3, ZrO2 and TiC, and industrial waste residue (blast furnace slag) used as sintering aid. The effects of raw material composition and sintering temperature on the phase composition, microstructure and mechanical properties of the materials were studied by X-ray fluorescence spectrometry (XRF), X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscope (SEM), three-point bending test and Vickers indentation, respectively. The results showed that addition of 15% nano-Al2O3 and 5% nano-TiC was beneficial to the improvement of the mechanical properties of the composite ceramics. Flexural strength and fracture toughness of such composites sintered at 1 650 ℃ reached 510 MPa and 6.58 MPa·m 1/2, respectively. Existence of intergranular fracture and transgranular fracture led to composite ceramics possessing better comprehensive properties. When the content of blast furnace slag was 4%, the relative density of samples sintered at 1 550 ℃ for 30 min reached 99.5%, and flexural strength and fracture toughness were 555 MPa and 5.20 MPa·m1/2, respectively. Liquid phase produced by blast furnace slag in the sintering process promoted growth of Al2O3 rods and decreased sintering temperature. Furthermore, content of glass phase in the ceramic matrix decreased and ceramic strength increased due to crystallization characteristics of blast furnace slag.

Abstract: SnO2 nanoparticles doped with different amounts of graphene were prepared by precipitation and ultrasonic impregnation methods. Pd1.5%/SnO₂/Gx% composites were obtained by doping Pd using the impregnation method. The CO sensing properties of Pd1.5%/SnO₂/Gx% nanocomposites doped with graphene at different ratio of 0.1%, 0.25%, 0.5% and 0.75% (mass fraction) were studied. The results showed that graphene could improve the sensitivity of Pd1.5%/SnO₂/Gx% to CO by reducing the agglomeration and enhancing the dispersion of SnO₂ nanoparticles. So Pd1.5%/SnO₂/G0.25% had the excellent CO sensing properties. The optimum operating temperature was 75 ℃. When the CO concentration was 115 mg/m3, the gas response could reach 56.2 and response， recovery time was 7 s and 10 s, respectively. The sample Pd1.5%/SnO₂/G0.25% still had gas-sensing performance when the CO concentration was only 5.75 mg/m3.

Abstract: N, S-Co doped microporous carbons (CPCT-X) were prepared by potassium hydroxide activation method at different carbonization temperatures using porous organic polymer (PCT) synthesized by a simple Friedel-Crafts alkylation reaction between melamine and thiophene as carbon precursors. The effect of carbonization temperature on the BET and pore sizes was investigated, and the CO2 capture and electrochemistry properties of CPCT-X with different pore structures and N, S contents were also conducted. The results suggested that CPCT-X had a large specific surface area (1 629 m2·g-1) and high micropore porosity (96.7%), and showed a good CO2 capture performance at the carbonization temperature of 600 ℃ (5.5 mmol/g, 273 K, 0.1 MPa). Meanwhile, the specific capacity could reach 210 F/g at a current density of 0.5 A/g when the carbonization temperature was 700 ℃.

Abstract: To obtain the influence of process parameters (static pressure, scanning speed and feed) of ultrasonic nanocrystal surface modification (UNSM) technology on the surface performance indexes (microhardness, surface roughness and depth of hardening layer) of LA106 magnesium-lithium (Mg-Li) alloy, the microhardness tester and the three-dimensional surface topography measurement system were utilized to test the microhardness and surface roughness of LA106 Mg-Li alloy after UNSM treatments. Combined with the saliency method, the orthogonal experimental results were analyzed, and the multi-objective optimization design method was used to study the comprehensive enhancement effect under the different UNSM process parameters. The results showed that the order of UNSM process on the comprehensive enhancement effect of LA106 Mg-Li alloy was as follows: static pressure, feed, and scanning speed. After multi-objective optimization design, the optimal combination of UNSM process parameters of LA106 Mg-Li alloy was obtained through intuitive analysis: static pressure of 0.3 MPa, scanning speed of 1 500 mm/min and feed of 0.05 mm. Therefore, the effect of static pressure should be mainly considered when UNSM technology was utilized to strengthen LA106 Mg-Li alloy.

Abstract: Fe/Cu nanocomposites prepared from sweet potato leaves were investigated for the removal of Rhodamine B(RhB) from aqueous solution. The effects of various parameters such as adsorption time, adsorbent dosage and pH were optimized by response surface methodology (RSM). The adsorption equilibrium data were well fitted with Sips model, and the thermodynamic study indicated that the adsorption process was a spontaneous endothermic process. The pseudo-second order kinetics model could describe well the adsorption process of RhB onto Fe/Cu nanocomposites. At 298 K, the maximum adsorption capacity of Fe/Cu nanocomposites for RhB was 484.18 mg/g, indicating that Fe/Cu nanocomposites had a good application in RhB waste water treatment.

Abstract: To solve the multi-objective heliostat field layout optimization in solar power tower system, multi-objective evolutionary algorithm based on decomposition (MOEA/D) was introduced into the domain of heliostat field layout, and a heliostat field layout optimization algorithm based on an improved MOEA/D (MOEA/D-HFL) was proposed in this paper. In this method, firstly an elliptical heliostat field model was set up aimed at optimizing annual-averaged overall optical efficiency and the land area occupied. Secondly, initial population generation strategy based on good-point set and opposition-based learning, stable normalization of objectives and dynamic genetic crossover distribution index were applied into MOEA/D to solve this problem. Pareto front of heliostat field layout problem was obtained and optimal compromise solution was got through fuzzy set theory. To validate the performance of the proposed algorithm, MOEA/D-HFL was compared with NSGA-II and original MOEA/D algorithms, and the simulation results confirmed the effectiveness and accuracy of the proposed method.

Abstract: In order to improve the short-term wind power prediction accuracy and enhance the representativeness and adaptability of the prediction model to specific weather conditions, a data processing method was proposed based on discrete Fréchet distance and kernel entropy component analysis (KECA).Using Fréchet distance, this paper established a mathematical model matching similar days, extracted samples similar to the prediction date, and then used KECA to extract suitable nonlinear principal elements from various meteorological elements as input of support vector machine (SVM) model. The simulation verification showed that the proposed method could significantly improve the prediction’s accuracy and has certain applicability.

Abstract: In DG, such as wind power generation or photovoltaic power generation being connected to the grid, the intermittence and instability of power generation and the periodicity and seasonality of the electric load would aggravate the power fluctuation of the distribution network, which could consequently destroy the power stability of the main power grid. In order to reduce DG power fluctuations on the distribution network, a capacity determination method of ESS was examined. The EMD method was used to decompose the distribution network which contained the DG power output samples. Based on the results, considering the ESS charge-discharge efficiency and the state of charge (SOC) constraints, the minimum ESS energy capacity was determined. Numerical outcomes proved that the capacity determination method of ESS could reduce the power volatility of the distribution network containing DG significantly. The example showed that the ESS which was configured as curve 3 could reduce the power volatility from 53.46% to 24.67% in 30 minutes, while keeping the system stable. Moreover, it had some peak load shifting effect which could lower the pressure of peak shaving of the electric power system.

Abstract: Only the randomness of variables was considered in the traditional reliability analysis for crack resistance of earth-rock dam. By introducing fuzzy set theory, the randomness and fuzziness of soil strain parameters and the fuzziness of failure criterion were considered comprehensively to establish the risk assessment model of cracking failure of earth-rock dam. Furthermore, the Monte Carlo simulation method was used to solve the upper and lower limits of fuzzy risk probability based on the interval numbers which were transferred from the fuzzy parameters by the level cut set. The model was applied to the cracking risk analysis of Maojianshan reservoir dam. When the level cut set α=0.5, the fuzzy risk intervals of cracking failure for 5 and 39.5 years of dam operation were [5.23%, 7.91%] and [28.91%, 32.49%], respectively. Compared with the conclusions based on the traditional risk determination, the result showed that the conclusions based on the fuzzy risk interval were closed to the actual situation of dam cracking, which could provide reference and basis for dam structure safety assessment and management.

Abstract: To explore the long-term exploitation of deep confined water in urban water sources in China, the concept and delineation method of rational water level for confined water were proposed. Taking the newly-built water source in Xiping County of Henan Province as the target area, the numerical model of groundwater was established according to the actual conditions of the study area. The groundwater level change under different scenarios was determined by groundwater numerical simulation method, and land subsidence of the study area was calculated by using the empirical formula. The amount of land subsidence under different scenarios, combined with the boundary of the designated water source protection area, delineated the rational water level of the confined water in the urban water source area of the study area. The results showed that while mining confined water, in order to prevent serious ground subsidence caused by the exploitation of confined water, the groundwater exploitation intensity of the newly-built water source in Xiping County should be controlled at 18 200-33 400 m3/d. Taking the G06 observation well as an example, the normal mining water level was 27.58 m, the restricted mining water level was 24.12 m, the prohibited mining water level was 20.34 m， and the threshold level of rational water level of confined water was 20.34-27.58 m.

Abstract: Foundation pit excavation could lead to additional deformation of adjacent underground pipelines. Based on the finite element analysis method, a three-dimensional numerical model of foundation pit and adjacent pipelines was established by relying on actual engineering; and the law of displacement changes was analyzed and the safety was evaluated in adjacent pipelines during deep foundation pit excavation. Based on the evaluation results, the reinforcement measures and effects of grouting method, micro-pile method and their combined methods were proposed and compared. The results showed that the maximum horizontal displacement and vertical displacement of the pipeline were also increased with the deepening of the excavation depth, which appeared in the middle of the pipeline. The size of the pipeline had a good inhibitory effect on the horizontal displacement of the pipeline, and had little effect on the vertical displacement of the pipeline when grouting reinforcement increased the width of the grouting zone. The micro-pile method has a good inhibitory effect on the vertical displacement of the pipeline, and had no effect on the horizontal displacement of the pipeline. The combined method could control the horizontal and vertical deformation of the pipeline well, which was a more effective method.

Abstract: In order to investigate phosphorus removal performance during the recovery process of residual sludge, an anaerobic-aerobic alternating sequencing batch reactor (SBR) was used for domestication, and the changes of specific phosphorus release (uptake) amount, specific phosphorus release (uptake) rate, MLSS and the ratio of phosphorus uptake to phosphorus release (uptake-release) were investigated. It was found that when the sludge retention time was controlled at 12.5 d, specific phosphorus release amount and specific phosphorus uptake amount were increased synchronously, the correlation coefficient was 0.927. Phosphorus removal performance began to recover when the activated sludge was regenerated by 16.7%, and improved obviously after 45.8%. At this time, the ratio of uptake-release was stable at 1.5～2. When activated sludge was regenerated by 58.3%, phosphorus removal performance almost recovered completely. The decrease of pH during anaerobic stage could indirectly indicate the performance of phosphorus release. The correlation coefficient between the variation of pH after the nitrate knee and the phosphorus release amount was 0.675, while the oxidation and reduction potential (ORP) could not indicate phosphorus removal performance either in the anaerobic stage or aerobic stage. A stable structure of activated sludge was the prerequisite for biological phosphorus removal. When the sludge concentration was stable during domestication process, the phosphorus removal performance began to improve significantly.

Abstract: The vibration of the ground caused by engineering trucks on urban roads was explored. Firstly, the function of road roughness was introduced, and the vehicle’s seven-degree-of-freedom equation of motion was established, then the FlexPDE software was used to solve the wheel excitation applied to the soil finite element model. On this basis, the propagation law of ground vibration caused by engineering trucks was studied, and the influence of vehicle’s velocity, load and road characteristics on vibration around the ground was discussed. The results showed that the ground vertical and transverse vibration attenuation rate in the near vibration source range were significantly higher than that in the far vibration source area. The increase of velocity and load had a significant impact on the ground vibration; as the uneven surface wavelength increased, the ground vibration response tended to decrease.

Abstract: It was not comprehensive to extract the vibration signal of rotating machinery from single channel signal. In order to extract the weak fault features of rolling bearing accurately from the strong background noise, a fault diagnosis algorithm of rolling bearing based on full vector frequency band entropy(FV-FBE) was proposed in this paper. The short time Fourier transform was used to calculate the frequency band entropy(FBE). And according to the FBE minimum principle, the bandwidth and center frequency of the dual channel signal band-pass filter were designed adaptively. The filtered dual channel signal was demodulated by the full vector Hilbert envelope, and the full vector envelope spectrum was obtained for fault diagnosis of rolling bearing. The experimental results showed that the FV-FBE algorithm could extract the fault features of rolling bearing comprehensively and accurately, which was better than the full vector envelope spectrum obtained by spectral kurtosis algorithm and had strong anti-interference ability.

Abstract: Aimed to solve the problems of optimization design of constrained layer damping (CLD) structures under stationary random excitation, the vibration response of CLD structures under stationary random excitation was analyzed by using pseudo excitation method (PEM). The topology optimization model of CLD structures was established by minimizing the root mean square value of the displacement response of the CLD structures under stationary random excitation and taking the volume of the CLD materials as the constraint condition. To circumvent the computational expensive of the sensitivity analysis, an efficient optimization procedure integrating the complex modal superposition method and the adjoint method was proposed. The topology optimization model was solved by method of moving asymptotes (MMA). The numerical examples demonstrated that the proposed optimization procedure of CLD structures under stationary random excitation was of validity and effectiveness.

Abstract: Aimed to improved at the traditional intelligent fault diagnosis system, which required a large amount of prior knowledge, and had the complexity of its model and the information loss caused by the incompleteness of single-channel signal, a full-vector deep convolutional neural network diagnosis model of rolling bearing was proposed. The full-vector technique was used to fuse the acquired two-channel signals to obtain the fused main vibration vector data, which contained more complete information than the single-channel data. Combining the main vibration vector and deep learning algorithm to construct the full vector depth convolutional neural network, the model could adaptively extract the fault features and use the back propagation algorithm to adjust the model parameters. The experimental results showed that the method could extract more complete fault information, and the model had higher accuracy and better stability.