2020, Doi: 10.11908/j.issn.0253-374x.20149
Mobile phone signaling data is used to identify the commuting connection in the Shanghai-Suzhou mega city-region， and the employment centers identified by the nonparametric analysis in the region is used to measure the polycentric structure of the mega city-region. First， the grid-based employment density distribution in the entire region is obtained using the mobile phone signaling data to identify the working place of commuters. Next， an improved nonparametric analysis is used to identify employment centers in the mega city-region. In the first stage， the local weighted regression is used to pick out candidate employment centers. In the second stage， the high employment density grids surrounding the candidate centers are identified， and the range of employment centers are formed. Finally， the Exchange Commuting Index and Criss-cross Commuting Index are used to verify the degree of functional polycentricity of the mega city-region. It is found that from the perspective of commuting connections， there are 20 regionally influential employment centers in the Shanghai-Suzhou Mega City-Region， and a functional polycentric structure has been formed. Using mobile phone signaling data and nonparametric analysis can accurately identify the scope of employment centers with regional influence， which can avoid the influence of administrative units on the results in previous studies， and provide supports for accurately understanding the spatial structure of the Shanghai-Suzhou Mega City-Region.
2020, Doi: 10.11908/j.issn.0253-374x.20069
This paper proposes a novel extension approach of BIM to cyber-physical systems（CPS）. It explores the general framework for extending BIM orienting to CPS， defines and constructs the cyber-physical building information modeling（BIM） entities. This paper can provide efficient and effective support for constructing new kinds of systems such as BIM-based dynamic control and management systems for operating and maintaining civil engineering， and human-machine interacting systems based on augment reality. The experimental results of the BIM based prototype systems show that the proposed approach has the advantages of high modularity， easy understanding， less programming codes， and high development efficiency.
2020, Doi: 10.11908/j.issn.0253-374x.20090
The modeled recycled concrete containing modeled square aggregates in different directions were applied to study the propagation of cracks at compression loading. The strain distribution and development were analyzed using digital image correlation and the finite element method， and the influence of the direction of aggregates on its damage evolution was investigated. The results show that when the modeled aggregate is placed horizontally， the strain concentration first appears in the interface on both sides of the aggregate. When the aggregate is placed in the direction of 22.5°， the strength and secant modulus are higher than the other two cases， and the strain concentration first propagates at the upper and lower vertices of the aggregate and develops into cracks along the interface on both sides of the aggregate. When the aggregate is placed in the direction of 45°， the upper and lower vertices of the aggregate have the highest strain concentration. Before the load reaches 80% of the peak force， the strain concentration of modeled recycled concrete is lighter than that of modeled normal concrete. For three directions of the aggregate， the strain concentration of modeled recycled concrete is 15%， 32%， and 39% smaller than that of modeled normal concrete. Because the elastic modulus of old mortar is in between the natural aggregate and new mortar， the strain concentration of the modeled recycled concrete is reduced. Based on the research on the influence of the direction of recycled aggregate on its damage evolution， it is proven that the methods of removing tips of aggregates and reducing needle flake aggregates can optimize and modify the recycled aggregates.
2020, Doi: 10.11908/j.issn.0253-374x.20126
In order to study the mechanical properties of the bolted joint of bulb flat ribs applied in composite bridge decks， two full-scale composite deck specimens with bolted joint of symmetric splice plates were designed and submitted to fatigue and static tests. Besides， a finite element model was established to analyze the stress state of the bolted joint. The test and finite element analysis results show that the bolted joint has a high fatigue cracking resistance and the bolted connection stays sound after the given fatigue load cycles in this paper. In addition， due to the asymmetric cross-section， the bolted joint features an asymmetric flexural state， which results in a 55% higher stress level of the bottom on mid-section of the splice plate installed on the side of bulb compared to the calculated value based on the plane bending theory. Moreover， the ultimate bending bearing capacity of the cross section in the bolted joint is dominated by concrete crush and shows a large margin after the occurrence of the bolt slip.
2020, Doi: 10.11908/j.issn.0253-374x.20053
Gusset joint is one of the most common joint systems used in single-layer aluminum alloy reticulated shells. In order to meet the modeling requirements of curved shell surface， arched gusset plates formed by stamping are usually adopted. The springback phenomenon is the main defect in the forming process of arched gusset plate， and the accurate prediction of the springback value is the key to ensuring the machining accuracy. In this paper， the stamping forming process of the arched gusset plate was simulated by using the ABAQUS/Explicit & Standard， and the finite element model was validated by the comparison of its springback value with the date of a practical gusset plate. Subsequently， a parametric analysis was conducted to investigate the effects of the material property， the value of stamping camber， the thickness and radius of the gusset plate， as well as the arrangement and total area of the bolt holes on the springback value. Finally， the calculation equation to estimate the springback value was proposed by theoretical deviation， and the coefficients of the equation were obtained by regression analysis. The good agreement between the calculation results and the numerical analysis results indicated that the proposed formula was with sufficient accuracy.
2020, Doi: 10.11908/j.issn.0253-374x.20056
In this paper， the tensile tests of 703 aluminum alloys were completed， and their mechanical properties and constitutive relations were obtained. Then， the tests of 24 domestic 703 high-strength axial pressure angle aluminum alloy members were performed， and the ultimate bearing capacity and failure mode of these members was analyzed. Next， a numerical analysis model was established and compared with the test data to verify the correctness of the numerical model. After that， a large number of numerical analyses were completed and the numerical model was used to comprehensively analyze the influence of slenderness ratio， section size， and other factors on the bearing capacity of the component. Finally， the stability coefficient calculated from the existing code formulas and the experimentally measured stability coefficient were compared. The results show that the Chinese "Aluminum Structure Design Code" can effectively calculate the overall stability bearing capacity of the 703 high-strength axial pressure angle aluminum alloy member.
2020, Doi: 10.11908/j.issn.0253-374x.19502
A finite element model for the analysis of grouted connections is established， and the effects of radial stiffness， ratio of length to diameter， and height-to-space ratio of shear keys on the ultimate axial bearing capacity are studied. Besides， the distribution of contact pressure between steel tube and grout material is also analyzed. The results show that the increase in radial stiffness can enhance the restraint effect on the grout and improve the axial ultimate bearing capacity of grouted connections. The ratio of length to diameter can significantly improve the ultimate bearing capacity， but at the same time， the interface transfer strength and ductility of grouted connections decrease continuously. The height-to-space ratio of shear keys mainly affects the number of shear keys in grouted connections， thus affecting the ultimate bearing capacity of grouted connection. The increase in the height-to-distance ratio can improve the ultimate bearing capacity of grouted connection.
2020, Doi: 10.11908/j.issn.0253-374x.19406
This paper proposed a batch rescheduling method based on improved variable neighborhood search algorithm for two types of events which were molding machine failure and early delivery， and the orders were batch-divided based on the minimum batching principle and non-equal batching principle. Then， a rescheduling mathematical model was established considering the process stability and punctuality. After that， an improved variable neighborhood search algorithm was designed， which had a faster convergence speed and a stronger global optimization ability by constructing transition neighborhood and superposition neighborhood. Finally， a magnetic material molding workshop is taken as an example to verify the results. The results show that the proposed rescheduling method can ensure on-time delivery of order， raise the utilization rate of molding machine， and provide a reference for the production decision of factory.
2020, Doi: 10.11908/j.issn.0253-374x.20003
An integrated multi-objective optimization method is proposed based on topology optimization and the implicit parameterized model to solve the problem that multiple types of section and plate variables should be considered when optimizing the aluminum alloy frame body of an electric vehicle. In order to obtain the frame body structure with a reasonable material distribution and load transfer as a reference for subsequent multi-objective optimization， the topology optimization design of the original body is conducted in the conceptual design stage. Then， the implicit parametric model of the vehicle body is built based on the topology optimization results and a response surface approximation model is established by using the parametric model to realize the automatic process of multi-objective optimization of aluminum alloy frame body. The results show that the all-aluminum frame body reduces weight by 11.9% while maintaining various performances within the target range. Therefore， the integrated multi-objective optimization method proposed based on topology optimization and the implicit parametric model can effectively improve the efficiency and accuracy of lightweight optimization of aluminum alloy frame body.
2020, Doi: 10.11908/j.issn.0253-374x.20071
To solve a class of implicit complementarity problems， the accelerated modulus-based matrix splitting iteration methods are presented and analyzed. The convergence theory is established when the system matrix is an
2020, Doi: 10.11908/j.issn.0253-374x.20188
The pricing problem of Switch Corridor variance swap， a new variance product based on two underlying assets， is studied in this paper. This product was first launched for hedging cross-market volatility risk by Credit Suisse in 2012 and has gradually become one of the most popular new product series in the structured financial derivative market. The control variate Monte Carlo method is used to solve the problem in double Heston stochastic volatility models. Based on the affine structure theory， the closed-form solution in an auxiliary process was obtained， which constructs an efficient control variate. Further， three different kinds of volatilities of the auxiliary were adopted. By means of numerical experiments， the solution in the process with dynamic volatility is proved to have an extraordinary effect on acceleration. The algorithm can also be used to solve the calculation problem of other high-dimensional variance products in various stochastic volatility models.
2020, Doi: 10.11908/j.issn.0253-374x.20082
Since the Black-Scholes model was proposed， many option pricing models have been proposed， which has become a hotspot in financial engineering. For the past few years， option pricing models based on Lévy process such as FMLS， CGMY and KoBol have drawn great attention because of their capability to represent the dynamic characteristics of underlying asset. Solving these models would eventually come down to solving a class of fractional partial differential equations. In this paper， a numerical scheme is proposed for the class of FPDE and the stable condition of the scheme is given. The numerical experiments prove the feasibility and effectiveness of the proposed numerical scheme. Based on the practical data of SSE 50ETF and CSI 300ETF index option， the option price and volatility curve are calculated to verify the effectiveness of KoBol model in real market.
2020, Doi: 10.11908/j.issn.0253-374x.20075
In this paper， the idea of fuzzy sets was embedded into a structural model of bond pricing， in which government implicit guarantee was regarded as a parameter. A closed-form formula for bond pricing was obtain by using the PDE（partial differential equations） methods. With the formula in hand， an empirical analysis was implemented to estimate the probability of government implicit guarantee by using different types of corporate bonds data. The fraction of the firm’s value lost in bankruptcy was first estimated by combing the historical data of bonds issued by private enterprises using the least square method. The function of government implicit guarantee was then analyzed by using the data of bonds issued by local and central state-owned enterprises. Three results were obtained. First， the probability of government implicit guarantee is higher for bonds issued by central state-owned enterprises than those issued by local state-owned enterprises. Next， as the credit rating increases， the probability of government implicitly guarantee increases. Finally， the probability of government implicit guarantee in developed regions is higher than that in undeveloped regions.
2020, Doi: 10.11908/j.issn.0253-374x.20102
This paper aims to construct the evaluation framework of securities companies， analyze the comprehensive competitiveness of listed securities companies in China， and provide reference for the ratings of securities companies. Therefore， a comprehensive competitiveness evaluation model for securities companies is proposed based on cloud model and grey relation analysis-technique for order preference by similarity to an ideal solution（GRA-TOPSIS） method. Besides， the cloud model is used to reflect the fuzziness and randomness of decision-makers’ evaluation information. The GRA-TOPSIS method is conducive to determining the weights of evaluation criteria of securities companies and the ranking of the candidate securities companies by combining the advantages of GRA and TOPSIS. Moreover， 30 securities companies listed in China are utilized to verify the validity of the model. Furthermore， some suggestions are proposed for securities companies to improve their competence.
2020, Doi: 10.11908/j.issn.0253-374x.20084
In the early stage of large-scale complex airport projects， there are usually many complicated tasks and time-consuming progress management problems. In order to solve these problems， this paper first proposed the management idea of preliminary work， and determined the key processes by identifying the starting path and establishing the conceptual model of preliminary work to sort out the contents of the preliminary work， based on which the idea of activity overlap is introduced， and the construction period calculation model based on design structure matrix（DSM） is established by using ternary parameter sets. The key processes are imported into the model， and the logical relationship is determined through the algorithm and the work cycle in the early stage of the project is shortened. Taking a certain airport project as an example， the DSM matrix is effectively applied in the early schedule control of the project to provide reference and guidance for the schedule management of large airport projects.
2020, Doi: 10.11908/j.issn.0253-374x.20096
Pressure injury is the focus of nursing， and an important index to evaluate the quality of nursing. Designing reasonable assessment scale and scientific prediction is the key measure to prevent it. Based on the 12 factors， three new risk factors are added in this paper， thus a more comprehensive scale is designed and patients are surveyed. The chi-square test is used to find the factors that have significant impact on pressure injury. Patients are divided into two categories， PIOA （pressure injury on admission） and HAPI （hospital acquired pressure injury）. Then， the characteristics of patients， the locations， and departments are analyzed. Three machine learning methods， support vector machine， probabilistic neural network， and general regression neural network are applied to construct the prediction model. The Gaussian kernel function is used in the SVM model， and the genetic algorithm is adopted to optimize the parameters. The prediction accuracy of the three models are compared in four scenarios. The SVM model， which has optimized parameters， has the highest accuracy of 84.68% while the accuracy of PNN and GRNN are equal to 82.78% and lower than SVM.