Volume 6 (2021): Issue 2 (July 2021)

In this paper, the Incomplete Global GMERR algorithm and the Global GMERR algorithm are used to solve the Sylvester equation. The numerical experiment is given to compare the CPU run time and the number of iterations of the two methods.

Based on investigation of existing folding wheelchairs’ usage, this paper analyzed wheelchair size and material in human-machine system model. The importance of new environmentally friendly materials’ application on wheelchair component producing in recent years was also explained. On the basis of strength and stiffness theory and calculation, applied materials were determined and rod mechanical calculation were carried out. The calculated results will have certain theoretical significance for wheelchair research and design.

This study presents the applications of the extended rational sine-cosine/sinh-cosh schemes to the Klein-Gordon-Zakharov equations and the (2+1)-dimensional Maccari system. Various wave solutions such as singular periodic, periodic wave, topological, topological kink-type, dark and singular soliton solutions are successfully revealed. To display the physical features of the reported solutions, we use some appropriate choice of parameters in plotting the 3D, 2D, and contour graphs of some attained solutions.

This paper studies a land primary development project in Pinggu District as an example for analysis since the complete survey data and adequate data analysis are not available on the assessment of social impact from primary development projects of land. In this paper, we carry out regression analysis based on statistical analysis of survey data, explore the attitudes of stakeholders towards development projects, and find out the main factors and risk problems. Finally, the required policy changes based on the analysis are recommended and put forward to provide reference for impact assessment of social stability.

This paper studies the robot arm sorting position control based on robot operation system (ROS), which works depending on the characteristics of the robot arm sorting operation using the top method, to automate the sorting operation and improve the work efficiency of workpiece sorting. Through the ROS MoveIt! module, the sorting pose and movement path of the robotic arm are planned, the inverse kinematics of the sorting robotic arm is solved, and the movement pose characteristics of the sorting robotic arm are analysed. The robot arm model was created using Solidworks software, and the URDF model file of the robot arm was exported through the sw2urdf plugin conversion tool, and the parameters were configured. Based on ROS for 6-degree-of-freedom (DOF) robot motion simulation, random extended tree (RRT) algorithm from open motion planning library (OMPL) is selected. The robot motion planning analysis and sorting manipulator drive UR5 manipulator. The results show that the sorting pose and motion trajectory of the robot arm are determined by controlling the sorting pose of the sorting robot arm, and the maximum radius value of the tool centre point (TCP) rotation of the robot arm and the position of the workpiece are obtained. This method can improve the success rate of industrial sorting robots in grabbing objects. This analysis is of great significance to the research of robots’ autonomous object grabbing.

The simulation of bone remodelling is highly complex due to the high nonlinear coupled relations between the damage and repair behaviours. In this paper, a new bone remodelling model based on the fatigue damage mechanism is proposed. Then the repair process of the human femur is simulated based on the finite element method. The results show that the new damage model can well simulate the bone damage evolution caused by overloadings. This indicates that the new mathematical model suggested in this paper can simulate the effect of external load on the cortical bone density and the related mechanical properties of the cortical bone.

The independent super high-rise building weakens and reduces the cooperation of functional subsystems. Implanting aerial courtyards could improve the aerial environment of that corresponding floor and enable the plane courtyards to be stereoscopic. Constructing multiple aerial courtyard-centred functional clusters of higher floors can optimise the overall space structural relationship. The paper uses the space syntax theory to discuss how to construct holistically linked aerial courtyards in a super high-rise building and applies the Grasshopper-based space syntax arithmetic logical unit to analyse and calculate the aerial courtyard of super high-rise building in different space structure modes, and also proposes design optimisation strategies based on these analyses. The paper points out that by setting aerial courtyard between vertical transportation space and functional space, establishing a direct connection between adjacent aerial courtyards, arranging vertical transportation space dispersedly and so on, it is possible to promote vertical cooperative effect, enhance integration and intelligibility of entire space structure, and provide guidelines and foundation for the construction of vertical cities.

Non-orthogonal multiple access (NOMA) has very high spectral efficiency and system capacity. NOMA has become one of the most competitive access solutions in 5G systems. In this article, the principle of NOMA is discussed first. Then, the NOMA system capacity optimisation problems are studied. Signal to interference plus noise ratio (SINR) is an important factor which affects the system capacity. The SINR of current user n is only related to the power allocated to users n+1 to N with high signal-to-noise ratio (SNR) but not interfered by users with low SNR. Therefore, a tree topology power allocation (TTPA) algorithm is introduced. When users are allocated to each layer of the tree structure, the current power allocation of each layer will not be affected by the previous layer. Through theoretical analysis, TTPA can achieve the same performance as the full search power allocation algorithm; however, its computational complexity is reduced from exponential to constant. It can be seen from the numerical simulation results that the proposed algorithm can achieve higher system capacity and has lower computational complexity.

Entering the new normal of economy symbolises the innovation of growth mode and continuous optimisation and upgradation of economic structure. Using EG index, this paper measures the agglomeration degree of 31 provinces and cities and 31 manufacturing industries in China from 2012 to 2016; the results show that under the new normal, the degree of industrial agglomeration in China's manufacturing industry remains basically stable, but the overall situation is still in a state of moderate agglomeration, the regions with higher degree of concentration continue to present the pattern of ‘one pole, two domains’. To further reveal the relationship between the concentration of Chinese manufacturing industry and regional economic growth, the GMM method of dynamic panel two-stage system was used, and the results showed that industrial agglomeration and economic growth do not have simple linear relationship, but inverted U-type relationship. There was a dynamic continuation effect of regional economic growth, and external factors such as fixed asset investment and government financial expenditure can promote regional industrial economic growth. Finally, the enlightenment of the complete article is given.

During the long-term exploration and development of the oilfield, it is difficult to ensure that all well logging curves are measured by the same type of instrument, the same calibration standard and the same operation mode, For different wells, there must be systematic errors caused by these reasons. Therefore, in addition to environmental correction, it is necessary to standardise logging curves. In XJ oilfield, three logging companies use wireline logging and logging while drilling to complete logging, in multi-well logging interpretation. To eliminate the systematic errors of different measuring tools, to maximise the geological information reflected by logging curves, and to make logging interpretation follow the same standard as much as possible, it is necessary to standardise the logging curve in the whole oilfield. This article takes the standardisation of well 106 in XJ oilfield as an example, the standardisation of different methods was compared, the method of combining frequency histogram and mean variance is better.

The optimal configuration and allocation of a microgrid are one of the key issues to guarantee the economic and reliable working of a microgrid. This is a multi-objective optimisation problem within which the economic index and the load power shortage rate index should be considered when optimising the configuration. In this article, a differential multi-agent multi-objective evolutionary algorithm (DMAMOEA) was designed to optimise the capacity configuration of a microgrid system, which includes three kinds of equipment: wind turbine, photovoltaic equipment and battery. The final optimisation results were compared with the Non-dominated Sorting Genetic Algorithm II (NSGA-II) algorithm. Simulation results showed the effectiveness of the algorithm. At the end of this article, the representative solutions in the calculation results are compared and explained and the environmental benefits are analysed, which show the effectiveness of the implementation of the microgrid system.

The natural environment is vital for the healthy growth of children. The absence of exposure to Nature in cities is an important cause of physical and psychological health problems in children. With the objective of a healthy growth environment for children, this paper states the active role of the urban waterfront space, analyses the relationship between children and urban waterfront space, summarises the characteristics of children’s outdoor activities, proposes the principle and methods of planning and designing a children-friendly urban waterfront space, and provides some improved design strategies.

A reexamination of the health problems of Chinese adolescents based on the concept of physical literacy (PL) was necessary. Through the use of follow-up data collected from the China Education Panel Survey 2014–2015, the main factors affecting the health of adolescents were identified, and possible explanations were investigated after cluster and inductive analyses were conducted. The results showed that (1) the 10 main factors identified as affecting adolescent health promotion are in line with the four main elements of PL (emotional, cognitive, social and physical elements) and (2) the three major categories of influencing factors identified through a cluster analysis were aligned with the three main factors of PL (endogeneity, fundamentality and permeability). These findings suggest that the factors influencing adolescent health promotion are closely associated with PL. The study results can provide empirical evidence for adolescent health promotion research and a reference for the development of evidence-based PL training models.

Based on the theory of entrepreneurial cognition, we examined the relationship between entrepreneurial passion and opportunity identification, and the moderating roles of environmental complexity and mediating role of entrepreneurial contextual knowledge in this relationship. Results from 246 entrepreneurs supported the hypothesis that both their entrepreneurial passion and their entrepreneurial contextual knowledge would be positively related to opportunity identification, and these relationships would be moderated by environmental complexity. Further, environmental complexity enhanced the relationship between entrepreneurial passion and opportunity identification, and also amplified the relationship between contextual knowledge and opportunity identification. The results suggest that the effect of entrepreneurs’ passion on opportunity identification depends on the level of the individual's contextual knowledge and environmental complexity.

The sports characteristics of E-bikes increase the conflict between traffic participants. In this paper, the criteria of E-bike traffic conflict are given according to time distance. Based on the rough set theory, the redundant rule reduction method is developed, and the following conclusions are drawn: 1. Signal lights and video monitoring points have little effect on alleviating the traffic conflict between e-vehicles and motor vehicles; 2. Setting isolation facilities, non-motor vehicle lanes and traffic police can effectively reduce the traffic conflict. The results show that this method can effectively analyse the main influencing factors of traffic conflict.

To solve the difficulties in practice caused by the subjectivity, relativity and evidence combination focus element explosion during the process of solving the uncertain problems of fault diagnosis with evidence theory, this paper proposes a fault diagnosis inference strategy by integrating rough sets with evidence theory along with the theories of information fusion and mete-synthesis. By using rough sets, redundancy of characteristic data is removed and the unrelated essential characteristics are extracted, the objective way of basic probability assignment is proposed, and an evidence synthetic method is put forward to solve high conflict evidence. The method put forward in this paper can improve the accuracy rate of fault diagnosis with the redundant and complementary information of various faults by synthesizing all evidences with the rule of the composition of evidence theory. Besides, this paper proves the feasibility and validity of experiments and the efficiency in improving fault diagnosis.

Aiming to address the shortage of experimental resources, the high cost of large-scale deployment of hardware experimental environment and the difficulty for students to get started in the software-defined network (SDN) course, this article proposes an SDN experimental teaching scheme based on the virtualised environment, and gives a specific experimental scheme design. The scheme utilises virtualisation technology to build a SDN experimental environment quickly, uses a lightweight network simulation platform – that goes by the name of Mininet – to build the SDN network and uses open-source controller Floodlight for centralised control of the SDN network. The scheme is mainly divided into three phases: basic, improvement and synthesis. In the basic phase, experimental projects mainly include the study of SDN basic concepts and the use of relevant tools; in the improvement phase, experimental projects mainly include the use of SDN flow table, group table, etc; in the synthetic phase, we design two innovative experimental projects that use computational intelligence technology to achieve efficient load balancing and accurate malicious attack detection. The difficulty of each phase is increasing. The constantly evolving levels of difficulty allow the individual needs of students with different levels to be met, thereby improving the effect of SDN experimental teaching and cultivating innovative SDN talents.

By utilising data from official sources, a statistical analysis was made on the elevator accidents that occurred in China during the period 2002 to 2019 on five aspects namely elevator type, occurrence stage, casualty’s identity, accident type and accident causes. The main purpose is to use the frequency and correlation among related factors to evaluate crucial causes, and to prevent similar accidents among technicians and users. Based on the statistical results and discussion, some proposals were put forward to the management of the responsible authorities for accident investigation and prevention of similar elevator accidents in the future.

The goal of promoting Information and Communication Technology of continuing education in colleges and universities is to standardise the process of teaching and scientific research, make the process more scientific and refined, so as to facilitate and improve the quality of teaching and scientific research, as well as professional disciplines. Rheumatoid arthritis is a disease with chronic, symmetrical and non-specific inflammation of the synovium of the joints (subcutaneous nodules, pericarditis, pleurisy, pneumonia, peripheral neuritis etc.) as the main clinical manifestations. The analysis of pharmacological big data information helps to understand its aetiology and pathological mechanism, which is complex and involves various pathogenic factors.

The behaviours of the pig are often closely related to their health. Pig recognition is very important for pig behaviour analysis and digital breeding. Currently, the early signs and abnormal behaviours of sick pigs in breeding farms are mainly completed by human observation. However, visual inspection is labour intensive and time-consuming, and it suffers from the problems of individual experiences and varying environments. An improved ResNet model was proposed and applied to detect individual pigs in this study based on deep learning knowledge. The developed model captured the features of pigs applying across layer connections, and the ability of feature expression was improved by adding a new residual module. The number of layers was reduced to minimise the net complexity. Generally, the ResNet frame was developed by reducing the number of convolution layers, constructing different types of the residual module and adding the number of convolution kernels. The training accuracy and testing accuracy reached 98.2% and 96.4%, respectively, when using the improved model. The experiment results showed that the method proposed in this paper for checking living situations and disease prevention of commercial pigs in pig farms is potential.

Industrial tourism is an important way for reuse of industrial wasteland. However, in China, reuse of industrial wasteland remain is in the exploratory practice stage, with problems such as lack of systematic planning, homogeneous strategies and inaccurate positioning of target customers. In this paper, we propose a method to reuse industrial wasteland by the combination of experience economy and recommendation algorithm. The industrial tourism product development direction is defined in the planning and design stage. The most relevant tourist-related features are extracted by establishing user profiles and experience economy-based questionnaires. The user-profile-based recommendation system generates a list of recommended tourist attractions. Finally, the recommendation-user-tag-project (R-UTP) algorithm is proposed and experimentally compared with UserkNN and ItemkNN algorithms. The R-UPT algorithm exhibits higher accuracy and has obvious advantages on recall ratio and novelty.

The data filling, mathematical calculations and statistical operations for property management are realised by a system development tool that adopts the browser/server (B/S) architecture, Java, as the development language and a framework that adopts Spring MVC mode; additionally, the MySQL database is used, the source code and database interaction process use the Mybatis framework and the front-end display uses the VUE.js framework.. Functional modules include the following elements: owner information, real estate information, engineering equipment, personnel management and lease management. The system has passed the functional test, if it has been in trial operation for 1 year in multiple residential communities and has the characteristics of simple operation, stable operation and strong scalability, among others.

With the rapid development of quantitative trading business in the field of investment, quantitative trading platform is becoming an important tool for numerous investing users to participate in quantitative trading. In using the platform, return time of backtesting historical data is a key factor that influences user experience. In the aspect of optimising data access time, cache management is a critical link. Research work on cache management has achieved many referential results. However, quantitative trading platform has its special demands. (1) Data access of users has overlapping characteristics for time-series data. (2) This platform uses a wide variety of caching devices with heterogeneous performance. To address the above problems, a cache management approach adapting quantitative trading platform is proposed. It not only merges the overlapping data in the cache to save space but also places data into multi-level caching devices driven by user experience. Our extensive experiments demonstrate that the proposed approach could improve user experience up to >50% compared with the benchmark algorithms.

From the perspective of Activity Theory (AT), this paper analyses the author's task-based teaching practice of English journal and newspaper reading and adopts a qualitative study approach to examine the influence of task design on students’ reading competence development. The tasks are designed mainly in the form of group work, highlighting the students as the subject and the regulating role of mediating artefacts, community, rules and division of labour. The data of students’ reflection journals, reading reports and group work records show that after the training of a series of tasks for eight units, students’ ability in reading English newspapers has been greatly developed, and they are also more confident in speaking and writing.

In order to determine the importance of influencing factors of energy consumption in oilfield water injection systems, the distribution of energy loss in the water injection system was analyzed, the factors affecting the energy consumption of the water injection system were determined, and an evaluation index system for the energy consumption of the water injection system was established. This indicator system covers all links and all energy loss nodes of the energy loss of the water injection system, thereby an evaluation model for influencing factors of energy consumption in water injection system based on entropy weight - grey correlation method was built. Use the entropy weight method to get the ranking of the importance of energy consumption indicators; use the gray correlation method to determine the correlation between each water injection system and energy consumption factors. The application results show that the entropy weight-grey correlation method proposed in this paper can effectively obtain the importance of the energy consumption factors of the oilfield water injection system, and provide scientific guidance for the daily management and targeted optimization of the water injection system.

In this paper, two iron salts, ferrous chloride (FeCl₂) and ferric chloride (FeCl₃), are directly added into an aeration tank for phosphorus removal, and their effects on the biochemical system are studied; the water quality parameters such as pH and alkalinity are also investigated. The extent of influence of the added iron salts on the pH and alkalinity of aerated solutions is demonstrated to be FeCl₃ > FeCl₂. When the dosage of iron ions is 20 mg/L, the decrease in pH and alkalinity caused by FeCl₃ is 0.5 and 65 mg/L, which is higher than FeCl₂ by 2% and 26%. The initial phosphorus removal effect of FeCl₂ is worse than that of FeCl₃, but after continued aeration and oxidation, the phosphorus removal effect of FeCl₂ can be improved; however, the final phosphorus removal effect is basically the same as that of FeCl₃ added directly. The results show that FeCl₂ is preferred when iron salt is added directly into the aeration tank to remove phosphorus. The proposed scheme can reduce the effect of iron salts on the alkalinity of the biochemical system on the premise of ensuring the phosphorus removal effect of the system, and is conducive to ensuring the stable operation of the biochemical system.

As the simulation data of the Simufact Additive software was inconvenient to process, QT and structured query language (MySQL) database were used to develop the database to solve the processing of the simulation data. The GUI interface that has the functions of processing and saving the simulation data was designed. The interface developed by QT was used to start the Simufact Additive software, connect to the MySQL database and save the simulation data. The results showed that using MySQL as the management of simulation data has achieved better results in the post-processing of simulation data.

The layered composite rock was subjected to triaxial compression tests under constant confining pressure and the stress–strain curves under different confining pressures were obtained. Based on the continuous damage theory and statistical strength theory, it is assumed that the strength of rock microelements obeys Weibull distribution by taking the defects such as random micro-cracks in the rock into account. The statistical constitutive model of layered composite rock with damage correction is established by taking the axial strain of rock as a random distribution variable of microelement strength. The model parameters were determined by the curve fitting method and referring to some test parameters. By comparing the experimental data and the constitutive model curve, the rationality and feasibility of the model are verified.

We analyse the influence of financial constraints on the peer effect of dividend decision in China by employing the Carhart four-factor model to construct instrument variables of peer influence. We find that (1) the decision of whether to pay cash dividends (DIV) is significantly influenced by peers, and the estimated marginal effect is 0.53%, but the question of whether to pay catering dividends and the extent of such dividends to be paid are not significantly affected by peers. (2) Under the semi-mandatory dividend policy in China, financial constraints will significantly reduce peer influence on the dividend level. (3) Peer influence on DIV is more pronounced among companies that face high financial constraints.

With the gradual ageing of China's population and the single-child family system becoming the backbone of society, the traditional pension way of relying on children at home not only does not guarantee the quality of life of the elderly, but also brings great pressure to the work and life of young people. The way of relying on pension institutions to provide for the aged is becoming gradually accepted by society. In elderly care institutions, safety supervision systems provide an important link to protect the safety of the elderly, thereby ensuring accurate analysis and supervision of the elderly persons’ activity routes and activity rules, and thus allowing an early warning to be given in a dangerous situation. The system realises the real-time positioning and monitoring of the elderly activity track, and can give early warning and timely rescue to the elderly who enter into any dangerous area. The system includes a server monitoring program and mobile APP; ASP.NET Technology to develop the monitoring program; SQL Server 2012 for data storage; and model view controller (MVC) architecture for the APP to improve the efficiency of program development. The supervision program comprises the functions of personnel information management, fence management, positioning service, activity track record, danger warning and rapid rescue. The APP deploys the location-based service (LBS) technology of Android, uses Baidu map API to obtain location information and draw activity track, and stores the information in the mobile phone SQLite database. The APP is installed on mobile phones, bracelets and other devices carried by the elderly and staff, which can record the current position of the person in real-time and simultaneously transmit it to the computer. When the elderly enter into a dangerous area, the system can quickly select the nearest staff and inform them for rescue, so as to ensure the safety of the elderly. After simulation test, the system has now reached the preset function.

With the increasing dynamics of the environment, the organisational innovation of high-end equipment manufacturing (HEM) enterprises has attracted more attention. This paper introduces a radial basis function (RBF) neural network to establish a model of the effect of organisational innovation on organisational performance (OP). Organisational innovation includes five dimensions: strategic innovation, structural innovation, cultural innovation, institutional innovation and process innovation. Through the modelling results, we know that all dimensions of organisational innovation have an effect on performance. According to the degree of impact, they are strategic innovation, structural innovation, process innovation, cultural innovation and institutional innovation.

An iterative method (AIM) is one of the numerical method, which is easy to apply and very time convenient for solving nonlinear differential equations. However, if we want to work in a large interval, sometimes it may be difficult to apply AIM. Therefore, a multistage AIM named Multistage Modified Iterative Method (MMIM) is introduced in this article to work in a large computational interval. The applicability of MMIM for increasing the solution domain of the given problems is construed in this article. Some problems are solved numerically using MMIM, which provides a better result in the extended interval as compared to AIM. Comparison tables and some graphs are included to demonstrate the results.

In this article, the three-dimensional Magnetohydrodynamics flow of a nanofluid over a horizontal non-linearly stretching sheet in bilateral directions under boundary layer approximation is addressed. A two-phase model has been used for the nanofluid. The influences of thermophoresis, Brownian motion and thermal radiation on heat and mass transfers are considered. Two different cases for the heat and mass transfers are studied. In the first case, uniform wall temperature and zero nanoparticles flux due to thermophoresis are considered. In the second case, prescribed heat and mass fluxes at the boundary are considered. By using the appropriate transformations, a system of non-linear partial differential equations along with the boundary conditions is transformed into coupled non-linear ordinary differential equations. Numerical solutions of the self-similar equations are obtained using a Runge–Kutta method with a shooting technique. Our results for special cases are compared with the available results in the literature, and the results are found to be in good agreement. It is observed that the pertaining parameters have significant effects on the characteristics of flow, heat and mass transfer. The results are presented and discussed in detail through illustrations.

The aim of the present study is to obtain different types of hyperbolic type solutions of the (2+1)-Ablowitz-Kaup-Newell-Segur (AKNS) equation. In order to construction exact solutions of AKNS equation, (1/G′)-expansion method is successfully applied. At the end of this application, singular soliton wave with considerable importance for the shock wave structure and asymptotic behavior employees have emerged. By giving arbitrary values to the constants in the solutions obtained, 3D, 2D and contour graphics are presented. The method used in this article can be used in other nonlinear differential equations (NPDEs) as it is reliable, easy and effective. Ready package programs are used to solve complex and difficult processes in this study.

The concept of inequalities in time scales has attracted the attention of mathematicians for a quarter century. And these studies have inspired the solution of many problems in the branches of physics, biology, mechanics and economics etc. In this article, new principles of non-linear integral inequalities are presented in time scales via diamond-α dynamic integral and the nabla integral.

The r-band of the Sloan Digital Sky Survey (SDSS) for 17,924 brightest cluster galaxies (BCGs) in clusters and groups within 0.02 ⩽ z ⩽ 0.20 are used to study possible environmental relations affecting the nature of these galaxies. We find a correlation between BCGs physical properties (the effective radius (R_e), absolute magnitude and central velocity dispersion (σ₀)) and their host groups and clusters velocity dispersion (σ_cl). This type of relations suggests that the most massive groups or clusters host larger central galaxies. On the other hand, the σ₀/σ_cl ratio as a function of σ_cl is consistent with [10].

In the classical Lotka-Volterra population models, the interacting species affect each other's growth rate. We propose an alternative model, in which the species affect each other through the limitation coefficients, rather then through the growth rates. This appears to be more realistic: the presence of foxes is not likely to diminish the fertility of rabbits, but will contribute to limiting rabbit's population. Both the cases of predation and of competition are considered, as well as competition in case of periodic coefficients. Our model becomes linear when one switches to the reciprocals of the variables. In another direction we use a similar idea to derive a multiplicity result for a class of periodic equations.

A single-cylinder test engine model was built by GT-Power software, and the effects of internal exhaust gas recirculation (i-EGR), external EGR (e-EGR), i-EGR/e-EGR coupling and the crank angle degree at which 50% of total heat loss has taken place (CA50) on combustion and emission characteristics of gasoline compression ignition at low-load condition were analysed. The results show that the ignition delay period with e-EGR was extended slightly with the increased EGR ratio, while that with i-EGR strategy first shortened and then extended, and that the optimised indicated thermal efficiency could be achieved using a small amount of i-EGR. With the same EGR ratio, nitrogen oxide (NO_X) emission is more likely to be suppressed by i-EGR, while soot emission was more deteriorated, and the superior trade-off relationship between carbon monoxide (CO)/hydrocarbon (HC) emissions and NO_X emission was attained by the combination of lower i-EGR ratios and CA50 closed to top dead centre. When using i-EGR/e-EGR coupling with total EGR ratio being fixed, the indicated thermal efficiency was decreased by increasing i-EGR ratio, while the lower NO_X, CO and HC emissions could be realised, but only with the consequence that soot emission increased.

With greater energy pressure and stricter emission standards, increasing power output and reducing emissions of engines are simultaneously required. To achieve this, considerable researches are motivated. In recent years, key and representative developments in the field of high-efficiency and clean engines have been carried out. Among them, a low temperature combustion concept called gasoline compression ignition (GCI) is widely considered by universities and research institutions around the world, since it has the potential to achieve ultra-low NO_X and soot emissions while maintaining high thermal efficiency. However, GCI combustion mode has certain issues to be solved, such as combustion instability under low-load conditions. Therefore, this paper reviews the experimental, computational and optical studies on the combustion stability control of GCI combustion mode during low loads and describes the recent progress to improve combustion stability as well as points out the future work finally.

Complete forestry infrastructure is the material basis for the realization of forestry production, ecology, and social functions. In order to clarify the scope of duties of forest infrastructure suppliers, this paper analyzes the characteristics of forestry infrastructure from the perspective of main suppliers, and summarizes forestry infrastructure as a material engineering facility that provides public services for forestry production, forestry economics, and social and ecological functions. The classical quartering method of goods was used to classify forestry infrastructure, which is divided into four categories: private goods, crowded public goods, club goods, and pure public goods.

A simple algorithm for calculating Christoffel symbols, a covariant projection of the result of the Laplace operator's action on the vector, vector curl and other similar operations in an arbitrary oblique base are proposed. For an arbitrary base with ortho e_i is found the expressions of vector projections (ΔA)_i and (rotA)_i, where A is a counter variant vector. Examples of orthonormal bases are considered and general expressions for (ΔA)_i and (rotA)_i for the bases are also given. As a demonstration of the working capacity of the common formulas obtained, detailed calculations of (ΔA)_i and (rotA)_i as an example are made in cases of spherical and cylindrical coordinate systems.

In 2015, Shijun Liao introduced a new method of directly defining the inverse mapping (MDDiM) to approximate analytically a nonlinear differential equation. This method, based on the Homotopy Analysis Method (HAM) was proposed to reduce the time it takes in solving a nonlinear equation. Very recently, Dewasurendra, Baxter and Vajravelu (Applied Mathematics and Computation 339 (2018) 758–767) extended the method to a system of two nonlinear differential equations. In this paper, we extend it further to obtain the solution to a system of three nonlinear differential equations describing the HIV infection of CD4+ T-cells. In addition, we analyzed the advantages of MDDiM over HAM, in obtaining the numerical results. From these results, we noticed that the infected CD4+ T-cell density increases with the number of virions N; but decreases with the blanket death rate μ_I.

Based on a questionnaire survey combining the stimulus-organism-response (S-O-R) theory with the cues theory, this paper establishes hypotheses and uses partial least squares structural equation modelling (PLS-SEM) to study and analyse the impact of web page house listing cues on Internet rental from the perspective of users. The results indicate that: (1) the relevant cues of Internet renting platforms are effective and worthy of attention, (2) the subjective arousal of the tenants triggers their behavioural changes to a large extent, and (3) the sensitivity of the tenants’ behavioural approaches to their feelings is greater than their purchasing intentions. In the context of the rapid development of the online market, understanding the user's response to target information is essential to promote the optimisation of the Internet rental platform, to improve the efficiency of online housing selection, and to encourage healthy development of the rental housing market.

Although the economy of a county that is linked to surrounding towns and rural areas constitutes a multiple basic economic unit within China's national economy, it usually exhibits independent characteristics and functions. Consequently, a county's economy plays a critical role in the overall economic development of a country's national economy. We created an evaluation index system based on entropy Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) to carry out a comprehensive evaluation of county economy across the entire Beijing-Tianjin-Hebei region. We found serious imbalances in the development of these counties, with county economies within Beijing and Tianjin being more advanced than those in Hebei Province. Furthermore, there were marked differences between county economies within prefecture-level cities of Hebei Province. The developmental level of counties in cities like Langfang, Tangshan and Chengde was relatively high. Conversely, the level of development of counties in Hengshui, Baoding, Xingtai and Handan was lower. Moreover, there were imbalances among cities in relation to county economic development, especially in Langfang, with smaller differences being found in Hengshui and Qinhuangdao. We analysed and identified the factors influencing differences between counties before providing recommendations.

GPS has a sharp performance decline in terms of accuracy indoors due to the complex building structure. A combined algorithm, targeting at received signal strength indication (RSSI) calibration optimisation, depending on deep neural network training via input vector Γ and the target output vector Ψ, termed reference signal optimisation algorithm (RSOA) is proposed to improve the positioning accuracy in the indoor Bluetooth positioning networks. Experimental results show that the relative error of the proposed RSOA between the estimated results and the measured ones can reach as low as 0.2%, and the absolute errors can be reduced to 0.13 m at most within 10 m.

Mathematics is a prerequisite for the development of blockchain technology. The deeply penetrated mathematical ideas support the establishment of the trust mechanism of the whole blockchain system, which makes the blockchain technology autonomous, decentralised, not so easy to tamper, open, anonymous and also possesses other characteristics. Due to these characteristics, the introduction of blockchain will greatly solve a series of problems faced by the quality and acquisition of big data in cities, and release more data vitality. Based on the perspective of chain blocks and big data fusion, this paper puts forward that data are the foundation of modern urban governance. Data management has become the key to modern urban governance. It puts forward that the building of a big data management system based on blockchain will strengthen the construction of the intelligent city and modernisation of urban governance capabilities.

Marxism is a scientific theoretical system about the understanding of the regularity of nature, society and human thinking. Marxism mainly includes Marxist philosophy (i.e. dialectical materialism and historical materialism), political economy and scientific socialism, among which Marxist philosophy is the theoretical basis, political economy is the main content and scientific socialism is the core and highest goal of Marxism. When analysis is made of the histories of mathematics, philosophy and economics, we are led to the inference that philosophy, economics and mathematics have a natural internal connection. This paper mainly discusses the relationship between philosophy and mathematics and Marx's evaluation of and research on mathematics, and then tries to express some basic and important principles of Marxist philosophy and political economy with the tools and ways of mathematics (formulas), in order to understand the profundities of Marxism much more easily.

Based on the H-M model, the compensation incentive model is constructed under the inter-task cost function. The best compensation incentive contract is constructed by solving the incentive model, and the incentive characteristics are analysed. The results show that the best incentive intensity decreases as the subject service selectivity increases. The higher incentive intensity of university managers for specific tasks, the lower efforts of subject librarians for another specific task. Moreover, when the tasks are substituted for each other, the profit-sharing ratios corresponding to different tasks are complementary. Finally, we establish the econometric empirical models to test these results.