As an important part of social travel, college students have long become the main users of the online car-hailing industry. It is highly necessary to explore the perceived behavior of college students waiting for the arrival time of online car-hailing to promote the new standardized development of online car-hailing industry. Firstly, an online questionnaire was conducted among 492 college students about their waiting behavior and perceived state. Second, Cronbach's $ \alpha $ and confirmatory factor analysis were used to test the reliability and validity of the questionnaire. Finally, the perceived time is divided into three categories, and a discriminant model of the perceived waiting time of ride-hailing vehicles is established based on the discriminant analysis method. Classification results and influencing factors of the discriminant analysis are empirically analyzed. It is found that these 35 variables contained in the four factors of personal characteristics, environmental factors, waiting behavior and mobile devices will affect the perceived waiting time. In the same group of classification functions, waiting behavior has the greatest impact on perceived waiting time, followed by environmental factors, and the lowest is mobile devices. The research results provide effective support for exploring the specific factors and potential psychology affecting college students' perceived waiting time, and provide certain theoretical value and practical guidance for effectively improving the service level and attraction of online car-hailing.

For the insufficient generalization ability of lightweight facial expression recognition algorithms, a facial expression recognition method based on multi-feature fusion and attention mechanism is proposed. LBP is used to reduce the interference of meaningless information of original face image, the dual-branch neural network extracts the features of original face image and LBP image respectively, merges the middle-level and high-level feature information extracted by these two networks and strengthens important features through attention mechanism for facial expression recognition, which can generate a large amount of discriminative features by multi-feature fusion to improve the recognition performance with a small number of parameters. The experimental results show that the recognition rate of this method has reached 70.21% on Fer2013 dataset and 95.59% on CK+ dataset respectively, which effectively improves the performance of lightweight expression recognition algorithm.

A deep neural network (DNN) prediction model based on multi-stage clustering is proposed for multi-step PM_2.5 concentration prediction. The proposed model includes decomposition, clustering and prediction. In the part of clustering, the first stage uses HDBscan density clustering to eliminate the noise, and then carries on the second stage clustering. In the second stage, Kmeans, AHClomerative, Gaussian mixture and birch clustering algorithms are used. In the prediction part, the deep neural network (DNN) is used as the predictor, and the hourly data of 11 air quality monitoring stations in Shenzhen are selected to verify the effectiveness of the model. The experimental results show that the prediction model based on multi-stage clustering is suitable for multi-step high-precision prediction of PM concentration, and its performance is better than DNN model and single-stage clustering prediction model.

In view of the information asymmetry and opacity of the existing system for centralizing the regulation of grain reserves, which reduces the reliability of data, and at the same time, the independence of various business links of grain reserve supervision, which brings information islands, a modular, pluggable and configurable model of grain multi-chain reserve management is proposed based on the characteristics of blockchain technology. The model adds channel technology in Hyperledger Fabric to isolate public traceability data and private data. An authorization mechanism for enterprise users is set up. An intelligent contract for authorization information is designed to check and judge the data format in order to secure the chain and so on. Through the construction of the supervision model and the experimental test results, it is shown that the system can well guarantee the data upload, query and safe storage under the condition of complete functions. It also realizes the supervision of the whole process of the data on the chain, the efficient processing and traceability of the problem events. It can enhance the credibility of grain reserve supervision data and ensure the safety of grain reserves.

The opacity of stochastic discrete event system is studied for stochastic system models. Firstly, the notions of stochastic infinite-step opacity and stochastic K-step opacity are formalized. By constructing a validator based on a two-way observer, a necessary and sufficient condition is obtained to verify the stochastic infinite-step opacity and stochastic K-step opacity of systems by using the validator of two-way observer. Finally, the verification algorithm for stochastic infinite-step opacity and stochastic K-step opacity based on two-way observer is proposed.

The multi-factor evolutionary algorithm (MFEA) is mainly studied and improved. The mixed probability distribution of the offspring population optimized by the maximum mean difference method (MMD) is used as the metric criterion of the algorithm. MFEA-MMD is improved on the basis of the Random Mating Probability matrix (RMP) of MFEA-II algorithm to avoid the influence of negative transfer most common in multi-factor evolutionary algorithms to the greatest extent. The convergence rate of the MFEA-MMD is faster than that of MFEA-II. The operation speed of the algorithm is 29% higher than that of MFEA-II, and the degree of knowledge transfer between tasks is 35% higher than that of MFEA-II.

The heat storage performance of heat storage device is directly affected by its’ thermal insulation structure. The application of Al-Si alloy in phase change energy storage is limited by the heat loss caused by its high working temperature. Aiming at the thermal insulation problem of high temperature phase change heat storage device, four different insulation structures such as glass wool, aerogel, composite aerogel and vacuum sandwich composite aerogel, used in the Aluminum-silicon alloy phase change heat storage device with the working temperature as high as 600 ℃, are put forward. A series of heat storage, thermal insulation and thermal release experiments are carried out, the thermal insulation performance compared including the shell temperature, the dissipated power and the thermal efficiency, and the influence of thermal insulation materials and vacuum interlayer on thermal insulation performance analyzed and studied. The results show that when the heat storage temperature is 600 ℃, the shell temperatures of glass wool, aerogel, composite aerogel and vacuum sandwich composite aerogel are, respectively, 91 ℃, 54 ℃, 51 ℃ and 41 ℃, the dissipated power is 589 W, 364 W, 325 W and 151 W, and the thermal efficiency is 0.64, 0.85, 0.88 and 0.94, respectively. The thermal insulation performance of vacuum sandwich composite aerogel is the best.

In order to meet the high-speed working requirements of the fifth-generation mobile communication, a high gain antenna for 5G millimeter wave based on SIW is proposed. Through the coupling between the rectangular patch and the resonant cavity, and arranging parasitic units on both sides of the main unit, the working bandwidth of the antenna (S₁₁≤−10 dB) reaches 10.7% (3.36~3.74 GHz) . The maximum gain in the working range reaches 7.78 dBi. Compared with other similar antenna, the proposed antenna can reduce 2/3 of the phase shifter and it uses Fr-4 material,which is of greater cost advantage.

Aiming at the problems of unstable structure, oversized and low productivity of C-stator, and low slot fullness and torque density of U-stator and E-stator in the disk transverse flux motor for high-torque and low -speed, a new multi-layer winding disk transverse flux motor topology with windings wound at both ends of the U-stator is proposed. The structure and principle of the motor are introduced, and a reluctance-based motor 3-D equivalent magnetic network model established. The relations between the no-load flux linkage, back-EMF and the main dimensions are calculated and derived for the main magnetic flux considering the spatial leakage of the permanent magnets. The superiority and effectiveness of the proposed motor structure is analyzed through a comparative study with the 3D finite element results of cogging torque, torque density and power factor of a double-wound disk transverse flux motor. A prototype machine is piloted and tested for the back-EMF, and the accuracy of the modeling and analysis method is verified by comparing the results of simulation and experiment.

When finite control set model predictive control (FCS-MPC) is applied in the flux-weakening control of permanent magnet synchronous machine (PMSM), the system suffers from poor parameter robustness. To solve this problem, a proportional-integral-derivative (PID) -type cost function of FCS-MPC in the flux-weakening control of PMSM is proposed. In the proposed strategy, the PID-type cost function consists of three components: the proportional error cost of tracking the current, the integral error cost of weakening the steady-state control error, and the differential error cost of reducing the ripple error. The prediction model is established by the mathematical model of PMSM, and the implementation process of FCS-MPC with PID-type cost function in the flux-weakening control of PMSM is described in detail. Meanwhile, the delay compensation strategy is applied to the system to ensure the accuracy of the prediction. The simulation results prove that when the parameters of the PMSM are mismatched in the flux-weakening control, the FCS-MPC base on the PID-type cost function can not only improve the robustness of the control system to motor parameters and load torque perturbations, but also retain the good dynamic performance of FCS-MPC.

1,2,3-Tris (2-cyanoethoxy) propane (TPPN) as a new electrolyte additive has been investigated in 4.55 V high voltage lithium cobaltate (LiCoO₂) /graphite pouch cells. By comparing the cycle performance of cells without and with TPPN, it is found that the addition of TPPN can improve the performance, and the optimal weight proportion is 2%. At 3.00-4.55 V and 1C/1C, the cells with 2%TPPN has a capacity retention rate of 86.4% at 25℃ for 900 cycles compared with the capacity retention rate of 8.7% that without 2%TPPN. According to the theoretical calculation and linear sweep voltammetry, the decomposition of TPPN is preferred to that of the electrolyte solvent. It can be seen from N 1s spectra from X-ray photoelectron spectroscopy on LiCoO₂ surface that TPPN forms an interfacial film on the LiCoO₂ surface. It can be seen from the impedance data that the interface film formed by TPPN has low impedance and high stability. From theoretical calculation, scanning, transmission electron microscopy, X-ray diffraction on LiCoO₂ surface and Co 2p spectra from X-ray photoelectron spectroscopy on graphite surface, it is revealed that the interface film formed by TPPN can effectively suppress the decomposition of electrolyte and the dissolution of cobalt ions, confirming the high stability of the interface film formed by TPPN.

In order to explore the joint remediation technology of eutrophic water bodies and jointly solve the problems of sediment pollution, plant waste and excessive phosphorus in water bodies, preparation of modified biochar by co-pyrolysis of sediment and plant waste to adsorb phosphorus in water was studied. The effects of preparation conditions such as the ratio of biochar raw material, pyrolysis time and temperature, modifier and its ratio on the adsorption of phosphorus were studied. The effects of pH and co-existing ions on the adsorption of phosphorus by Fe modified biochar were investigated. The results show that the adsorption capacity of Fe modified biochar 20:10:3-ZnBC450-3Fe on low concentration phosphorus (1 mg/L) was 2.76 mg/g, and the removal rate was 68.96%. Under neutral conditions, Fe modified biochar adsorbed phosphorus well. Na⁺, K⁺ and Cl⁻ promoted the adsorption of phosphorus, but Al³⁺, $\mathrm{CO}_3^{2-} $ and $\mathrm{SO}_4^{2-} $ inhibited the adsorption of phosphorus. The adsorption of phosphorus by Fe modified biochar conformed to the quasi-second-order kinetics and Freundlich adsorption isotherm model. SEM-EDS test proves the effectiveness of phosphorus adsorption by iron-modified biochar. The preparation of biochar by co-pyrolysis of sediment and plant waste to adsorb phosphorus in water is a comprehensive restoration technology combining physical, chemical and biological means for river and lake garden ecosystem, which has good application prospect.

In this study, the polysaccharide was extracted by hot water extraction from Dendrobium officinale. The polysaccharide extraction rate was used as an indicator. The ratio of extraction material to liquid, the extraction temperature, extraction times and the extraction time were the influencing factors. A single factor experiment was designed. A better extraction process was obtained through orthogonal experiments. The extraction rate of polysaccharides was 12.45%, and the optimal extraction conditions were: extraction time is 60 min, material-liquid ratio is 1: 20, extraction times are 2 times, and extraction temperature is 60 ℃. The effects of polysaccharides on cell viability, tyrosinase activity and melanin content were determined by B16 cells experiment. By establishing a dry injury model in HaCaT cells, HaCaT cells dry injury model was established, and the cell viability of polysaccharides on cells in dry injury was determined. Different concentrations of polysaccharides (10, 62.5, 125, 250, 500 μg/mL) can inhibit melanin production, in the polysaccharide concentration of 500 μg/mL, the tyrosinase activity was 69.30% and the melanin content was 66.20%. Different concentrations of polysaccharides (10, 62.5, 125, 250, 500 μg/mL) can reduce cell desiccation damage, and in the polysaccharide concentration of 125 μg/mL, the survival rate of cell desiccation damage increases by 15.51% to 86.58%. Dendrobium officinale polysaccharide can reduce the melanin content by inhibiting tyrosinase activity, and can increase the survival rate of cells in desiccation damage and reduce the death of cells caused by desiccation damage. With the establishment of the HaCaT cells desiccation damage model, polysaccharides can improve the survival rate of cells in desiccation damage and reduce the death of cells caused by desiccation damage.

Due to factors such as loss of coherence between repeated SAR acquisitions, the interferograms are often very noisy. The quadtree filter can remove such discrete noise in unwrapped interferograms and obtain clean deformation results. A mining area in Yunnan is investigated, discussing how the minimum division window and the gross error threshold affect the performance of quadtree filtering. The surface deformation time series of the mining area is obtained using Sentinel-1 satellite data from 2019 to 2021. The results show that the mining area has significant surface deformation during our monitoring period, focusing mainly on three regions with both uplift and subsidence. The deformation time series present wave-like variations in the time domain. The maximum incremental subsidence and uplift are up to 67.3 and 79.4 mm in 12 days, respectively. The difference is $ \pm 10.9\;\mathrm{m}\mathrm{m} $ between InSAR and 41 repeated observations from 32 ground-based total stations.

By introducing the concept of generalized order and type, and using Newton polygon, a study is conducted on the random Dirichlet series in the right half plane whose coefficients are $\varphi $ mixing random variables and satisfying the ${({\rm{MZ}}) ^*}$ condition and obtain the relationship between the maximum modulus and the error term in approximating.

With the substantial increase of traffic flow in high-density cities, particulate matter pollution has been a serious problem in urban blocks. As an important composition of urban landscape, its plant morphological parameters have an important impact on air quality of street. Taking a block in Guangzhou as the research subject while using field monitoring data, the accuracy of ENVI-met software in dealing with block scale PM_2.5 simulation characteristics is verified. Then, the combination of various morphological parameters of plants on both sides of the street in the case area is modeled and numerically simulated. The result of ENVI-met shows that the model is suitable for simulating the traffic source PM_2.5 of high-density urban blocks. The simulation results of several groups of plant morphology show that the height of street trees is recommended to be about 10 m, which can effectively reduce the PM_2.5 of traffic source concentration. In combination with relevant specifications, it is recommended to set the trunk height as 3~5 m and the crown width as 5~7 m.

In response to the "Water Pollution Prevention and Control Action Plan" promulgated by the State Council and to achieve the goal of direct drinking of municipal tap water in 2035, the secondary water supply net- work of an old community in Shanghai is simulated. According to the current pipeline network layout, three other different pipeline network layout schemes are proposed, which are simulated to compare the water age, pressure, flow rate and other hydraulic conditions at each point. Choosing a more appropriate transformation plan and comparing the current situation and planned one, the water level of the pool and the diameter of the pipe network are respectively optimized. The simulation results show that the water level optimization and pipe diameter optimization of the pool can significantly shorten the water age, and the pressure and flow velocity are in a more appropriate range. According to the simulation results, the multi-dimensional comparison and selection are finally selected based on the current situation of the optimization of the water level of the pool and the pipe diameter. After testing, all water quality indicators are up to standard after the renovation, and the residual chlorine attenuation coefficient is reduced by 53.3%.