Search

The coaxiality and unbalance are the two important indexes to evaluate the assembly quality of an aeroengine. It often needs to be tested and disassembled repeatedly to meet the double-objective requirements at the same time. Therefore, an intelligent assembly method is urgently needed to directly predict the optimal assembly orientations of the rotors at each stage to meet the double-objective requirements simultaneously. In this study, an assembly optimization method for the multistage rotor of an aeroengine is proposed based on the genetic algorithm. Firstly, a spatial location propagation model is developed to accurately predict the spatial position of each rotor after assembly. The alignment process of the assembly screw holes of the adjacent rotors is considered for the first time. Secondly, a new assembly optimization strategy is proposed to select different assembly data for the specific values of the coaxiality and unbalance, respectively. Finally, a double-objective fitness function is constructed based on the coaxiality and unbalance. The simulation and experimental results show that the assembly optimization method proposed in this study can be utilized to achieve synchronous optimization of the coaxiality and unbalance of an aeroengine during preassembly.

Photocatalytic oxidation technique is considered as one of the most prospective approaches to solve the problem of environmental pollution. Herein, the novel ternary nanocomposite UiO-66(Ce)/Ag/BiOBr was fabricated via simple synthetic strategy. The obtained UiO-66(Ce)/Ag/BiOBr exhibited an excellent performance and photocatalytic efficiency of ketoprofen reached 93.5% after 180 min illumination. The ·OH and ·O

The high-efficient photocatalytic material Ag3PO4/g-C3N4 was synthesized through calcination and precipitation methods. The physico-chemical properties of the material were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), ultraviolet–visible (UV–Vis) diffuse reflectance spectroscopy (DRS) photoluminescence spectra (PL) and Brunauer-Emmett-Teller (BET) surface area test. The morphology analysis indicated that Ag3PO4 particles were heterogeneously dispersed on the surface of layered g-C3N4. The Ag3PO4/g-C3N4 nanocomposites were applied in the photodegradation of bisphenol A under the visible light irradiation. The effects of the material proportion, the initial concentration of BPA, and the salinity on the degradation were discussed. The results showed that 92.8% bisphenol A (10 mg/L) can be photodegraded under 3 h irradiation by Ag3PO4/g-C3N4 with 25% Ag3PO4 mass ratio. The photodegradation kinetics and possible photocatalytic mechanism were discussed. The active specie ·O2− was found to play a key role during the photocatalytic reaction. The reaction mechanism was described based on valence band, conduction band energy levels and reduction potentials of oxygen and hydroxyl radicals.

Semiconductor photocatalysis has a great prospect in solving the problems of environmental pollution. Herein, the thickness-dependent BiOIO3 loaded by carbon quantum dots (CQDs/BiOIO3) was first synthesized. The 3 wt% CQDs/BiOIO3 with sheet-like morphology exhibited the highest efficiency of 95.01 % for the photodegradation of bisphenol A after 60 min. The outstanding photocatalytic activity was ascribed to two aspects: the first was the efficient separation of photogenic e−-h+ in thin layered BiOIO3 (50 nm); the second was the acceleration of charge transfer and the extension of light absorption after the CQDs co-catalysis. The h+ and O2− were dominant active species in the degradation process and possible mechanism was deeply studied. The attacked sites of bisphenol A were ascertained by Fukui index and the degradation pathways were proposed through the LC–MS analysis. This work significantly deepens the understanding of layered bismuth-based material and provides ideas for the design of high-performance catalysts.

In this study, the Z-scheme heterojunction photocatalysts Ag/NH2-MIL-125(Ti)/CdS (AMC-5, AMC-10 and AMC-20) were first successfully obtained by stepwise deposition of Ag and CdS. The morphology, crystallinity and photochemical properties of the materials were investigated. The N2 adsorption–desorption isotherm showed that AMC-10 had a large specific surface area (363.41 m2/g). Cyclic tests proved that the heterojunction exhibited good stability. In comparison, AMC-10 exhibited a significantly higher photocatalytic activity. Results suggested that 94.2% ketoprofen (10 mg/L) can be photocatalytically degraded to intermediates and small molecules after 180 min of simulated sunlight illumination. AMC-10 had a large degradation rate constant 0.0168 min−1, which is 3.15 and 2.50 times higher than that of CdS and NH2-MIL-125(Ti), respectively. The total organic carbon removal percentage of ketoprofen was 57.5%. Free radical trapping experiments indicated that ·O2− and h+ were the main active species, which can also be verified by the detection of electron paramagnetic resonance. Possible degradation pathways and reaction mechanisms were proposed by band potential calculations and liquid chromatography-mass spectrometry. The results of Vibrio qinghaiensis sp.-Q67 culture demonstrated that the biotoxicity of ketoprofen increased first and then decreased with time. It can be concluded that the Z-scheme heterojunction of Ag/NH2-MIL-125(Ti)/CdS was beneficial for the separation of photo-generated electrons and holes and the noble metal Ag nanoparticles play the important role in the photocatalytic degradation with the surface plasmonic resonance effect and Schottky junction.

Novel magnetic CoFe2O4-embedded MIL-101(Cr) with tetramethylammonium hydroxide (CoFe2O4/MIL-101T) was prepared through the facile hydrothermal method. Tetramethylammonium hydroxide acts as a template molecule and avoids the recrystallisation of terephthalic acid. The material was applied as the adsorbent in the magnetic solid-phase extraction (MSPE) process coupled with high-performance liquid chromatography to detect the five flame retardants in environmental water samples. Several parameters affecting MSPE efficiency were systematically investigated, such as MIL-101T content, material amount, desorption solvents, adsorption time, solution pH, theoretical maximum enrichment factor (EFmax) and the reusability. Under optimised conditions, good linearities were achieved for five flame retardants with correlation coefficients R2 > 0.9961. The limits of detections for analytes at the signal-to-noise ratio of three were 0.013–0.071 μg·L−1. This method was applied to the analysis of tap, pond, lake and river waters. The recoveries were in the range of 81.5 ± 3.2–107.0 ± 2.3% with the relative standard deviations ranging from 0.11% to 8.66% in four real water samples. The adsorption mechanism was the hydrophobic interaction between the material and the analytes besides pore adsorption action of the material.

The novel HNO3-modifitied biochar (NBC) was synthesized from walnut shell. The NBC was characterized from scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectrum. The NBC was then used in the adsorption of sulfadiazine, sulfamethazine and sulfachloropyridazine from aqueous solution. The material surface has carbon/oxygen-contained groups, which is benefit for the adsorption. The results showed the adsorption ability of NBC on three sulfonamides were 32, 46, and 40 mg g−1, respectively. The kinetic was found to follow the Elovich model and the isotherm conformed Freundlich. Adsorption was more favorable at weak acidic solution. The interactions mainly include π - π EDA, electrostatic interaction, Lewis acid-base interaction, hydrophobic interaction and H-bond.

In this study, chlorella was first used as the carbon source of Carbon dots (CDs) and further modified the BiOCl. Then, a novel photocatalyst Carbon dots/BiOCl (CBOC) was successfully synthesized. The morphology, crystal structure, chemical states and optical properties of the material were characterized by different techniques. Meanwhile, the energy band structure and density of states of CBOC2 composite were calculated based on density functional theory. In order to investigate the photocatalytic performance of the materials, the photodegradation of tetracycline was carried out under the simulated sunlight. The conditions of different materials, materials dosage and sample concentration were compared. About 99.5% tetracycline (10 mg/L) can be photodegraded by 15 mg CBOC2 in 75 min illumination with 52.2% mineralization rate. The material can be reused with high stability. The ·O2− is the main reactive species. The possible degradation pathways and mechanism of photocatalysis was discussed in detail. The CDs originated from chlorella has the large contribution in the photocatalysis. The work creates a new road of the application of chlorella in photocatalysis.

Carbon-encapsulated Ni nanoparticles (the average diameter of the particles is 7–8 nm) in B matrix were successfully in situ synthesized by chemical vapor deposition (CVD) in order to solve the agglomeration of nanoparticles by traditional mixing method. The influences of CVD technique on the carbon yield, morphology and structure were well investigated based on model system, and the (MgB 2 ) 0.96 Ni 0.04 bulks containing 3.8, 8.2 and 8.5 wt% carbon were prepared at 750 °C. The X-ray diffraction patterns showed no substitution of Ni for Mg and less substitution of C for B during the synthesis process, whereas the TEM analysis suggested such decorated insertions with core-shell structure were stable within the MgB 2 matrix and hopefully acted as pinning center due to the small size. In our experiment, although the advantage of nanoparticles was suppressed by the large amount of MgO impurities during the deposition process, a small enhancement of J c was observed in the low field range, which indicated improved grain connectivity because of the refinement of MgB 2 grains by inducing homogeneous nanoparticles. In view of this, a desirable J c performance at high field could be further obtained under the control of MgO content.

It is a central issue to improve the separation efficiency of photogenerated charge carriers and the utilization of visible light in the field of photocatalysis. Herein, taking MIL-125(Ti) as a host material, the Pt/MIL-125(Ti) was first prepared by solvothermal method to build the interface of Schottky junction. Ag was then introduced onto the surface of Pt/MIL-125(Ti) to form the interface with the surface plasmon resonance effect. These double interfaces in the composite play a synergistic role on the photodagradation. The morphology, crystallinity and photochemical properties of the material were tested. By comparison, Pt/MIL-125(Ti)/Ag (4 wt% Ag) exhibited the best performance in the photodegradation of ketoprofen (KP, 10 mg/L) and the degradation process conformed to the pseudo-first-order kinetics. The photodegradation rate is 0.0253 min−1, which was higher than MIL-125(Ti) (0.0009 min−1). The TOC removal efficiency of KP reached approximately 51.5%. The electron paramagnetic resonance (EPR) and free radical capture tests verified that h+ and ·OH played the prominent roles during the reaction system. The degradation process, possible pathways and reaction mechanism were proposed. The design of the double interfaces between semiconductor and noble metals is a novel strategy to enhance the photocatalytic performance.

A previously developed and validated 6-year-old (6YO) Finite Element (FE) human head model was used to evaluate the biomechanical performance of a new bicycle helmet design for children. The cushion structure of the new helmet design is made of honeycomb paperboard and corrugated paperboard instead of Expanded Polystyrene (EPS) foam. Simulation results showed that the EPS foam helmet can effectively resist external shocks in a short period. However, based on biomechanical responses of the 6YO head model, honeycomb and corrugated paperboard helmets also had a promising cushioning performance. From the drop test of the head-helmet model simulations, the effects of paperboard thickness and material parameters on the helmet protection efficiency were further investigated. It was concluded that the EPS foam helmet can be replaced with honeycomb/corrugated paperboard helmets which are made of more environmental friendly manufacturing materials.

Nanoscale zero-valent iron (NZVI) was first assembled on magnetic carbon/Fe

Cobalt doped TiO 2 nanoparticle prepared by ultrasonic-assisted hydrothermal method was used as the photocatalyst in the degradation of chlorophenols (CPs) and bromophenols (BPs). The doping content of cobalt in this catalyst was optimized as 0.5 wt%. The degradation rates of 2,4,6-trichlorophenol (2,4,6-TCP), 2,4-dichlorophenol (2,4-DCP), 2,6-dichlorophenol (2,6-DCP), 2-chlorophenol (2-CP), 4-chlorophenol (4-CP), 2,4,6-tribromophenol (2,4,6-TBP), 2,4-dibromophenol (2,4-DBP), 2,6-dibromophenol (2,6-DBP), 2-bromophenol (2-BP) and 4-bromophenol (4-BP) were estimated based on the quantitative determination of the degradation products. It was found that the degradation of CPs and BPs underwent dehalogenation process with pseudo-first-order kinetics. Moreover, the photodegradation kinetics was compared between CPs and BPs. The degradation rate of BPs was more quickly than CPs due to the difference in bond energy of carbon–halogen, and the degradation rates of BPs and CPs were mainly dependent on the number and the position of substituting halogen atom respectively. In addition, 2,4,6-TCP and 2,4,6-TBP can be effectively degraded by more than 95.1% and 93.5%, respectively, within 240 and 30 min. Tri-substituted phenols were firstly photodegraded to corresponding di-substituted ones, then to mono-substituted ones, and finally to phenol by TiO 2 /Co nano catalyst, although there were some differences in selectivity, rate and yield in the dehalogenation pathway of 2,4,6-TCP and 2,4,6-TBP.

The novel semiconductor heterojunction of MIL-53(Fe)/BiOCl composite was first prepared through the solvothermal reaction. The prepared materials were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Brunner-Emmet-Teller (BET) and ultraviolet-visible diffuse reflectance spectroscopy (DRS). MIL-53(Fe)/BiOCl heterojunction is a kind of photoexcited materials and it accelerates the photoreactivity of BiOCl under the visible light irradiation. It was used to remove Rhodamine B (RhB) with the existence of persulfate (PS). The UV–vis spectrophotometer and the TOC detector show that the degradation rate and TOC removal efficiency of RhB (20 mg/L) are 99.5% and 69.4%within 30 min visible-light irradiation, respectively. Due to the proper band gap of material and the presence of electron acceptor, PS, the survival time of active radicals are increased. The active species h+, ·SO4− and ·OH are found to play the important roles during the reaction system. The possible mechanism for the RhB degradation of MIL-53(Fe)/BiOCl/PS is also proposed. Furthermore, the results of the material reusability for the degradation of RhB indicate that the MIL-53(Fe)/BiOCl has a good stability and can be used in the environmental water sample treatment.

With its advantages of good torque and speed characteristics, high-speed dynamic response, the brushless DC motor is gradually becoming the first choice for electric vehicles. In order to effectively solve the brushless DC motor control problems caused by the non-linear characteristics, so that this type of motor can be preferably applied in electric vehicles. In this study, according to the nonlinear characteristics of brushless DC motor, the mathematical model is established. Rotating speed and current dual-loop control is selected as the control strategy, The control system is analyzed and simulated, the simulation model of the drive motor is established in the MATLAB/Simulink. And dynamic driving characteristics of the motor are analyzed. The simulation results show that mathematical model is accurate. In this design, no static speed difference can be realized and the motor can be quickly started and broke. The study has great significance in improving the electric vehicle dynamic performance and battery efficiency, as well as increasing the driving range.

Brain tissue mechanical properties are of importance to investigate child head injury using finite element (FE) method. However, these properties used in child head FE model normally vary in a large range in published literatures because of the insufficient child cadaver experiments. In this work, a head FE model with detailed anatomical structures is developed from the computed tomography (CT) data of a 6-year-old healthy child head. The effects of brain tissue mechanical properties on traumatic brain response are also analyzed by reconstruction of a head impact on engine hood according to Euro-NCAP testing regulation using FE method. The result showed that the variations of brain tissue mechanical parameters in linear viscoelastic constitutive model had different influences on the intracranial response. Furthermore, the opposite trend was obtained in the predicted shear stress and shear strain of brain tissues caused by the variations of mentioned parameters.

Skull stiffness of children is of great significance to protect brain tissues during traffic accidents. In this paper, the effects of skull stiffness on traumatic brain injury (TBI) are investigated by using a validated 6-year-old child head finite element (FE) model according to Chinese standard GB/T 24550-2009 Results showed that the HIC value, intracranial pressure, Von Mises stress and shear strain of brain tissue increased with the decrease of skull stiffness during the impact of FE model with engine hood. Therefore, the injury risk of the child head decreases with the increase of skull stiffness. And the skull with higher stiffness can provide a better protection for brain tissues during traffic accidents. Introduction Recently, finite element (FE) method has become the effective way to investigate the head injury mechanism and evaluate the injury risk of head [1]. Many child head FE models have been developed and validated by reconstructing the traffic accidents or cadaver experiments of children [2]. To a certain extent the effectiveness of evaluating the traumatic brain injury (TBI) by using the FE models depends on the proper selection of mechanical properties of head materials. However, mechanical properties of head materials vary constantly in the process of child growth. For example, the skull stiffness of child head increases with the growth of children [3]. The role of the skull is to protect the head tissue during the impact. The aim of this paper is to investigate the effects of skull stiffness on the intracranial responses of child head by using a validated 6-year-old child head FE model according to Chinese standard GB/T 24550-2009 [4]. Materials and Methods 6-year-old child FE model description Based on Ruan’s validated FE model [5], intracerebral soft brain tissues were further divided, and hard tissues such as mandibular bones and facial bone were created based on the 6-year-old head CT data using the FE developing method in literature [3]. Mesh Qualities of the FE model were also optimized in this study. The detailed 6-year-old head FE model was shown in Fig 1, the brain soft tissues include cerebrum, corpus callosum, cerebellum, brainstem, ventricle, diencephalon, sinus, flax, CSF, and dura matter. The whole FE head model with 103,716 nodes mainly consisted of 17,346 shells (falx, dura matter and tentorium) and 96,128 bricks (other brain structures). The meshes among brain tissues, CSF and skull were connected with common nodes. The FE model has been validated in the literature [6]. Load and boundary setup of impact simulation experiments The impact between child head model and engine hood was reconstructed according to Chinese standard GB/T 24550-2009 [4]. Engine hood surface at Location A where injurious structure of shock absorber exists (Fig 2a) is selected from child head form test zones as impact location [7]. Fig 2b shows the forehead of FE model impacts location A of the engine hood surface in the simulations, which were conducted by using PAM-CRASH code. The velocity of the center of mass of FE head is set at 35 km/h and the engine hood is stationary. Velocity direction of FE head was 50 degree with the 4th International Conference on Computer, Mechatronics, Control and Electronic Engineering (ICCMCEE 2015) © 2015. The authors Published by Atlantis Press 963 horizontal plane, and impact direction was downward and rightward related to front structure on vehicle longitudinal vertical plane. Fig.1 The FE model of a 6-year-old child head with detailed head anatomical structures (a) Impact location beneath the hood (b) Simulation of impact between FE head model and hood Fig.2 Load and boundary setup of impact simulation In order to investigate the effects of skull stiffness variation on intracranial responses of the child head, a parametric study was conducted. The skull stiffness was divided into five levels, among which Young's modulus of cortical bone of skull varied at five levels of 98.7 (E1), 987 (E2), 9870 (E3), 98700 (E4) and 9870000 (E5) MPa respectively and that of spongy bone of skull varied at the five levels of 36.9 (E1), 369 (E2), 3690 (E3), 36900 (E4) and 3690000 (E5) MPa respectively. The middle level (E3) was adopted as the baseline experiment in the simulation. Results and Discussion Acceleration and HIC value Head injury criterion (HIC) calculated from the resultant acceleration history of head is adopted to evaluate head injury in the Chinese standard GB/T 24550-2009.The peak resultant acceleration (58 g) and HIC15 (601) in E5 experiment is smaller than that in other experiments (Table 1). The peak acceleration and HIC value decreased with the increase of skull stiffness. During the impact between hood and child head, the hood will have a large deformation and absorb more impact energy if the stiffness of skull is high. However, the skull with lower stiffness will have a large deformation and absorb more energy if the stiffness of skull is lower than hood, which leads to higher peak acceleration and HIC value. Therefore, the skull with higher stiffness could lower the risk of head injury during the impact. Intracranial pressure The intracranial pressure curves of the child head in E1, E2, E3, E4 and E5 experiments were shown in Fig 3. During the impact, the skull with higher stiffness could decrease the deformation of skull and brain tissue, hence the coup pressure and contrecoup pressure decrease with the increase of skull stiffness. Data in Table 1 reveals that mechanical properties variation of skull has a certain influence on intracranial pressure of the child head. Von Mises stress of brain tissue Fig.4 showed the Von Mises stress distributions of brain tissue with different skull stiffness. Roth thought that the Von Mises stress of brain tissue was a good predictor for moderate neurological windshield

Polychlorinated biphenyls (PCBs) congeners with various degrees of chlorination and substitution patterns are among the most widespread and persistent man-made organic pollutants. They are toxic, lipophilic and tend to be bioaccumulated. The knowledge of the physico-chemical properties is very useful to explain the environmental behavior of PCBs and to perform an exposure assessment. In this paper, we have used a new molecular representation, the molecular hologram, to generate quantitative structure-property relationship models to predict the physico-chemical properties of biphenyl and all of its chlorinated congeners. The investigated properties include 1-octanol/water partition coefficient (logK(ow)), aqueous solubility (-logS(w)), aqueous activity coefficient (-logY(w)), Total molecular surface area, Henry's law constant (logH). The results show that this new quantitative structure-activity relationship approach presents highly predictive models for important physico-chemical properties of PCBs.