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Atmospheric pollution can affect human production life and physical and mental health to a great extent. In this paper, the hourly pollutant monitoring data from five state-controlled automatic atmospheric monitoring stations in Daqing City from 2017 to 2021 are collected to analyze the temporal and spatial variation patterns of CO, SO2, NO2, PM2.5, PM10, O3. And to assess the health risks of atmospheric particulate matter. The HYSPLIT model is applied to analyze air pollutants' transport pathways and the potential source areas of atmospheric particulate matter with the PSCF model. The results show that the concentrations of SO2 and NO2 are higher in the north of Daqing and the concentrations of pollutants generally show a decreasing trend with time. The hazard quotient (HQ) for atmospheric particulate matter, which is slightly above the safe range set by the EPA, is higher in winter and spring. After principal component analysis, CO, NO2, and PM10 are the main factors affecting PM2.5. In the summer, the main urban area's air pollution is mostly influenced by the southwest pollution trajectory. In other seasons, the northwest route predominantly regulates the regional transfer of contaminants. The key regions that could be the sources of atmospheric particulate matter include North China, Inner Mongolia, Mongolia, and Russia.

Outdoor thermal comfort in urban environmental settings is often investigated at a small scale, e.g., in street canyons. Yet, pedestrian thermal comfort in a district is scarcely assessed, especially in terms of the comprehensive overhead environments such as sky openness, green coverage, and sun exposure. This study provides a systematic methodology to quantify the district-scale pedestrian thermal comfort performance considering overhead environments. Mobile transects were designed for data collection during peak hot hours within a medium-scale district. A portable weather station was used to measure outdoor thermal environments and a fisheye lens was to capture hemispherical images of overhead environments. A universal thermal comfort index, Physiological Equivalent Temperature (PET), was subsequently calculated with the collected thermal environment data. Meanwhile, hemispherical images were segmented into areas of visible sky, overhead greenery, and sun, which were further weighed into corresponding view factors. Eventually, a multiple regression model was developed between PET and view factors together with meteorological variables. The results showed that a decrease in the sky view factor of 0.17 or an increase in the green view factor of 0.21 could reduce PET by 0.5°C. The findings scientifically support resilient urban planning in greening and cooling urban dense spaces for comfortable and liveable environments.

High-risk societies are uncertain, ambiguous and unpredictable. Risk fluctuations are prone to the intertwining and overlapping of various accident hazards and safety risks. China is prone to the interweaving and overlapping of various accident hazards and safety risks, which leads to an increase in the number of factors affecting public safety as well [1]. Therefore, this paper will quantify specific ranking indicators in terms of frequency of hazards, degree of hazards and vulnerability to different hazards. The ranking is based on the quantified results in red, yellow and green and the hazard risk level is calculated according to the risk formula. This study will take the Chengdu-Chongqing region as an example and optimise the storage of materials in the emergency logistics base in order to maximise the precise and rapid supply of materials to the main demand points. The efficiency of emergency material deployment will be further improved and emergency materials will be well secured.

Based on the control principle and flow distribution characteristics of the electro-hydraulic proportional load-sensitive multiway valve in an excavator, a system simulation model is established in AMEsim. After proving the accuracy of this model by comparing simulation results with theoretical results for various flow distribution characteristics under saturated and unsaturated conditions, this model is used to study the effect of three-way valve preload on the multiway valve system to prove that the simulation method can evaluate the influence of design parameters on the multiway valve system and then guide the design of multiway valves.

From the aspect of bibliometrics and social network analysis, this paper studies the content characteristics and network evolution of service quality in China, form visual analysis charts and summarizes the research hotspots and development trends. Taking CNKI database as the data source, data mining and association analysis of sample data were carried out by means of manual judgment, keyword co-occurrence, bibliometric software BICOMB and Pajek. 872 related literatures were retrieved from 1999 to 2019, and the tendency of the number of published papers in each year was close to the inverted U type. This study expands the application fields of bibliometrics and social network software, and analyzes the development trend of service quality. The theoretical and practical research on service quality has achieved rapid development in the past 20 years. The library service quality and service quality satisfaction have always gotten a high level of attention, and the characteristics of network platforms for service quality have gradually become apparent because of the development of the Internet and computer technology.

The micro-interface formed inside and on the surface of the catalytic particle is the place where the catalytic reaction proceeds. The micro-interface temperature is one of the important factors determining the reaction efficiency. Numerical simulation was used to investigate the fluid-solid coupled heat transfer law of micro-interface under the regulation of spherical particles’ self-rotation. The results show it takes up to 4.78 s that the average surface temperature of non-rotating particle with a diameter of 3 mm decreases from 300 ℃ to 150 ℃, which is the lowest temperature required for high-efficiency selective catalytic reduction reaction of NOx with NH3, while self-rotation can reduce the cooling rate of particles. When the direction of particle self-rotation is perpendicular to gas velocity, as the self-rotation speed increases, the high-temperature area of the particle surface diffuses more fully to the latitude direction. Significant effect can be made as the self-rotation speed reaches 5 rad/s, the uniformity of the surface temperature can be increased by 27.1 % ~ 37.7 % compared with non-rotating particle, and the uniformity can be increased by a maximum of 49.5 % at a self-rotation speed of 500 rad/s.

Wire arc additive manufacturing (WAAM) technique has revealed the potential of replacing existing aerospace industry parts manufactured by traditional manufacturing routes. The reduced mechanical properties compared to wrought products, the porosity formation, and solidification cracking are the prime constraints that are restricting wide-spread applications of WAAM products using aluminium alloys. An interpass temperature is less studied in robotic WAAM and is the vital aspect affecting the properties of a formed product. This paper highlights the effects of change in interpass temperature on porosity content and mechanical properties of WAAM parts prepared using DC pulsed GMAW process, with 5356 aluminium consumable wire. The samples prepared with different interpass temperatures were studied for the distribution of pores with the help of computed tomography radiography (CT radiography) technique. A WAAM sample produced with higher interpass temperature revealed 10.41% less porosity than the sample prepared with lower interpass temperature. The pores with size less than 0.15mm3 were contributing over 95% of the overall porosity content. Additionally, on a volumetric scale, small pores (

Aiming at the motion track controlling of the semi-active magnetorheological damper based above-knee prosthesis (MRAKP), according to the LaSalle’s invariant set theorem, a kind of nonlinear compute torque (NCT) control law for the track controlling of the AKMR, is proposed to promote the robustness and performance of the intelligent above-knee prosthesis. The proposed NCT controller includes the feedforward control and the feedback control. The former one is used to compensate the nonlinear terms in the dynamic model of the MRAKP, such as the Coriolis force, the centripetal force, and the gravity. The feedback control, utilizing a nonlinear PD controller, adaptively adjusts the control gain coefficients and reduces the system error. On these bases, numerical simulations on the MRAKPare carried out to analyze the performance of the proposed NCT controller in ADAMS and simulink. For comparing, the track controlling performance of the PD controller and the CT+PD controller are also presented in the paper. Simulation results indicate that the proposed NCT controller for the MRAKP is able to adaptively adjust the control gain coefficients with lower track error and higher robustness than the conventional PD controller and the CT+PD controller.

Aerial ladder fire truck is a kind of fire-fighting truck which is used for rescue of people and goods from high altitude locations. The aerial ladders of the fire truck are typically nested U-shaped truss structures manufactured with thin-walled steel by welding. Compared with close-shaped truss structures, their stiffnesses are relatively low. This means that they are quite slender structures, and they will deflect quite significantly due to their own weight and the working loads applied. If the original design of the ladder is straight, then the ladder will deform to a ‘fishing-rod’ shape in the air. The consequent ‘bent-down’ shape of the deformed ladder causes significant inconvenience during rescuing operations. To deal with this issue, a practical solution to the problem is that the ladder is manufactured with an appropriate uptilted curved shape, and it could deform to an approximately straight ladder when it is under certain desired working condition. In this paper, the effectiveness of the curved ladder design proposed in this paper has been validated by both finite element analysis and experimental results.

This article has been withdrawn by the authors. Request approved by the editors and the publisher on July 2, 2018.

This paper takes the 5T loader boom as the research object. Firstly, the static analysis of the boom loader is carried out under the typical working conditions. The weak part of the welding seam is found, and then the welding deformation of the boom is analyzed for the weak welding part. Further, the deformation trends of the welding arm are studied. It is found that the weak part of the welding seam is at the welding arc of the boom plate and the beam. Besides, the deformation of the arm plate is about 30mm inward in the welding process due to the welding stress, and the residual stress of the boom. This work can provide theoretical and data support for the processing and deformation correction of the boom.