Under the new normal of China’s economy, the competition among the port enterprises is not only the competition of the core competence of the port, the port industry chain or the port supply chain, but also the competition of the port service ecosystem. In this paper, the concept and characteristics of the port service ecosystem is discussed, a hierarchical model of the port service ecosystem is constructed. As an extended logistic model, Lotka-Volterra model is applied to study the competitive co-evolution and mutually beneficial co-evolution of enterprises in the port service ecosystem. This paper simulates the co-evolution of enterprises in the port service ecosystem by using MATLAB programming. The simulation results show that the breadth of the niche of the enterprises is changing with the change of the competition coefficient and the coefficient of mutual benefit in the port service ecosystem. Based on that, some proposals are put forward to ensure the healthy and orderly development of the port service ecosystem.
The main goal of this paper is to show that international peer review can work in China’s context with satisfactory outcomes. Moreover, this paper also provides a reference for the practice of science and technology management.
This paper starts with a discussion of two critical questions about the significance and design of international peer review. A case study of international peer review of CAS Centers for Excellence is further analyzed.
International peer review may provide a solution to address the problem of quantitative oriented research evaluation in China. The case study of research evaluation of CAS Centers for Excellence shows that it is possible and feasible to conduct an international peer review in China’s context. When applying this approach to other scenarios, there are still many issues to consider including individualized design of international peer review combined with practical demands, and further improvement of theories and methods of international peer review.
1) Only the case of international peer review of CAS Centers for Excellence is analyzed; 2) A relatively small number of respondents were surveyed in the questionnaire.
The work presented in this study can be used as a reference for future studies.
Currently, there are no similarly detailed studies exploring the significance and methodology of international peer review in China.
In order to discuss the simulation model of the ship transmission line and the state of the transmission line, an early fault model is built according to the evolution principle of the short circuit fault of the transmission line and combining with the fault characteristics of the early fault. A small distributed ship transmission line system is built in MATLAB/ Simulink. Then, combined with the constructed fault module, the original short circuit module, and the load module, the various states (normal state, early fault state, severe early fault state, short circuit state) of the ship transmission line are stimulated, and the features of voltage signal in each state is analysed. It is concluded that, due to the normal operation of the ship transmission line system, the variation characteristics of the flow signal and voltage signal caused by the sudden load mutation, that is, the sudden load and the sudden increase load, are very similar to the changes caused by the early fault. Therefore, in order to find a more accurate early fault detection method, the state is divided into normal state, sudden load state, sudden increase and sudden decrease load state.
Inspired by ant foraging, as well as modeling of the feature map and measurements as random finite sets, a novel formulation in an ant colony framework is proposed to jointly estimate the map and the vehicle trajectory so as to solve a feature-based simultaneous localization and mapping (SLAM) problem. This so-called ant-PHD-SLAM algorithm allows decomposing the recursion for the joint map-trajectory posterior density into a jointly propagated posterior density of the vehicle trajectory and the posterior density of the feature map conditioned on the vehicle trajectory. More specifically, an ant-PHD filter is proposed to jointly estimate the number of map features and their locations, namely, using the powerful search ability and collective cooperation of ants to complete the PHD-SLAM filter time prediction and data update process. Meanwhile, a novel fast moving ant estimator (F-MAE) is utilized to estimate the maneuvering vehicle trajectory. Evaluation and comparison using several numerical examples show a performance improvement over recently reported approaches. Moreover, the experimental results based on the robot operation system (ROS) platform validate the consistency with the results obtained from numerical simulations.
A Method for the Estimation of the Square Size in the Chessboard Image using Gray-level Co-occurrence Matrix
The paper proposes a new simple procedure for measuring the square size employing the gray-level co-occurrence matrix of a chessboard image. As the size of the square structure in a chessboard image provides the geometric constraint information among the corners, it is available to improve the precision of extracting corners and serve the camera calibration. The co-occurrence matrix of a chessboard image is constructed to obtain the statistic information of the grayscale distribution. The 2D offset of the matrix is parameterized to calculate the correlation which is regarded as the implication of the repetition probability of the similar textures. A descending tendency is observed in the experiments because the similarity decreases with the greater offset. However, minimum and maximum are captured in the correlation curve, which represents that the square texture reappears with the periods of one and two square size, separately. The size of the square is tested by applying the first minimum of the correlation. The experiments are performed on the horizontal and vertical directions which are corresponding to the length and the width of the square, respectively. The experiments prove that the described method has the potential to measure square size of the chessboard.
The complicated relationship of the high order static indeterminate structure will lead to a lot of calculation work. The strength analysis of the structure is very difficult. In aircraft design phase, a structural simplified method should be used to model the load characteristics of the structure. In the paper, the buckling analysis of airframe jointed panel is investigated under combined loading and the effect of jointed position to buckling load is also presented. For the buckling analysis of special joined structure, one new method which is better than traditional methods is described.
An active-vision process is presented by the affine invariability of the ratio of triangle areas to reconstruct the 3D object. Firstly, a plate with the triangle array is designed in the same plane of the planar laser. The image of the plate is rectified from the projection space to the affine space by the image of the line at infinity. Then the laser point and the centroids of the triangles constitute a new triangle that bridges the affine space and the original Euclidean space. The object coordinates are solved by the invariant of the triangle area ratio before and after the affine transformation. Finally, the reconstruction accuracy under various measurement conditions is verified by experiments. The influence analyses of the number of line pairs and the accuracy of the extracted point pixels are provided in the experimental results. The average reconstruction errors are 1.54, 1.79, 1.90, and 2.46 mm for the test distance of 550, 600, 650, and 700 mm, which demonstrates the application potential of the approach in the 3D measurement.
This study presented a self-designed prompt gamma neutron activation analysis (PGNAA) model and used Fluka simulation to simulate the heavy metals (Mn, Cu, Hg, Ni, Cr, Pb) in soil samples. The relationship between the prompt γ -ray yield of each heavy metal and soil thickness, content of heavy metals in the soil, and source distance was obtained. Simulation results show that the prompt γ -ray yield of each heavy metal increases with the increase in soil thickness and reaches saturation at 18 cm. The greater the proportion of heavy metals in the soil, the greater the prompt γ -ray yield. The highest content is approximately 3%, and the change in distance between the neutron source and soil sample does not affect the prompt γ -ray yield of heavy metals.
The electrohydrodynamic (EHD) flow induced by the corona discharge was experimentally investigated in an electrostatic precipitator (ESP). The ESP was a narrow horizontal Plexiglas box (1300 mm×60 mm×60 mm). The electrode set consisted of a single wire discharge electrode and two collecting aluminum plate electrodes. Particle Image Velocimetry (PIV) method was used to visualize the EHD flow characteristics inside the ESP seeded with fine oil droplets. The influence of applied voltage (from 8 kV to 10 kV) and primary gas flow (0.15 m/s, 0.2 m/s, 0.4 m/s) on the EHD flow transition was elucidated through experimental analysis. The formation and transition of typical EHD flows from onset to the fully developed were described and explained. Experimental results showed that the EHD flow patterns change depends on the gas velocity and applied voltage. EHD flow starts with flow streamlines near collecting plates bending towards the wire electrode, forming two void regions. An oscillating jet forming the downstream appeared and moved towards the wire electrode as voltage increased. For higher velocities (≥0.2 m/s), the EHD transition became near wire phenomenon with a jet-like flow structure near the wire, forming a void region behind the wire and expanding as voltage increased. Fully developed EHD secondary flow in the form of counter-rotating vortices appeared upstream with high applied voltage.
The dissolution of corn stover in alkaline solvent system composed of NaOH-H2O2 was reported and the separation of its ingredients combined with acid precipitation, ethanol extraction was proposed. It is proven that the residual after alkali solvent was cellulose, the filtrate by the acid precipitation of the liquor was lignin, the solid by the ethanol extraction of the liquor was hemicellulose. The optimum dissolution conditions were determined by single-factor experiment as follows: the concentration of H2O2 5.0%, pH 11.5, dissolution temperature 60°C, dissolution time 3.0 h, the ratio of liquid to solid 30 mL/g. And chemical analysis were employed to determine the purity of the components separated. The structure of the components separated were identifi ed by FT-IR, SEM, XRD and NMR. The cellulose recovery yield can achieve to 84.2% and lignin recovery yield is 86.6%, the hemicellulose recovery yield is 96.7%. After recycling the solvent 3 times, the recovery yield of cellulose, lignin and hemicellulose were 82.7, 87.6 and 97.4%, and the purity of cellulose, lignin and hemicellulose were 98.0, 96.5 and 98.7%, respectively.