Abstract:In order to understand the effect of the surface evaporation on thermocapillary convection in an annular pool, a series of numerical simulations on thermocapillary convection of cold water around 4℃ in the pure steam environment were carried out. The results show that the surface evaporation mass flux is mutually coupled with thermocapillary convection. With the increase of the evaporation Biot number, the surface temperature is dropped, and the evaporation mass flux near the hot wall is increased, but it near the cold wall is closely related to the Marangoni number. When the Marangoni number is small, the dimensionless total evaporation mass at the evaporation interface increases with the increase of the evaporation Biot number; while when the Marangoni number is large, the total evaporation mass increases first and then decreases with the increase of the evaporation Biot number. With the increase of the aspect ratio and the radius ratio, the flow strengthens and the total evaporation quality also increases.

Abstract:The effect of different reinforcement quantities and strengthening history on the bending performance of concrete beam was analyzed by pasting CFRP in the tension zone and anglesteel in the compressive zone of 7 reinforced concrete beams. The stress-strain curves and the load deflection curves of the steel and the CFRP were obtained. The results show that the ultimate bearing capacity of test beams reinforced by CFRP and angle steel increases significantly, and external reinforcement material can effectively delay or inhibit the development of cracks. For the loading and unloading reinforcement of reinforced concrete beams, there are varying degrees of strain hysteresis in reinforcement materials.And the utilization rate of the CFRP and the angle steel on the unloading reinforced beams is better than that on the no-unloading reinforcement beam.Calculation results of ultimate bearing capacity obtained by experiment agree well with the test values.

Abstract:Drilling riser system is a critical component of marine oil drilling, and buoyancy module is essential for deep-sea drilling riser system. In this paper, three phase epoxy buoyancy materials filled with carbon fiber reinforced hollow macrospheres and hollow glass microspheres was prepared by vacuum pour molding. Strength analysis has been conducted on the buoyancy modules with different load conditions by using ANSYS. The results show that the density of buoyancy material is 500 kg/m³ and the compressive strength is 60 MPa. The maximum deformation of buoyancy modules occurs in the free end with a value of 4.08 mm. The maximum stress occurs on the structure adjacent to riser with a value of 50.02 MPa, which makes the prepared buoyancy modules meet the drilling requirements of 3 000 m water depth.

Abstract:To solve the problem that the separation and the fault diagnosis of rotating mechanical compound fault signal always difficult to obtain desired results under the condition of single-channel, first, the method of ensemble empirical mode decomposition (EEMD) was applied to build the virtual channels and the method of linear local tangent space alignment (LLTSA) was applied to reduce the dimension, which solved the problem of underdetermined blind source separation well. Then, training the over-complete dictionary and using the method of signal sparse decomposition to extract the sparse characteristics of rotating mechanical compound fault signal. Finally, the support vector machine was employed to evaluate the effect of signal separation and fault diagnosis method. Moreover, the proposed method was applied to the experiment of rolling bearing fault diagnosis, and it's found that the separation and classification of compound fault signal was completed efficiently.

Abstract:As one of the object detection, vehicle detection, which has been a hot research area in recent years, is one of the important application in intelligent transportation system. To figure out the problem that vehicle detection is lack of the ability of vehicle category recognition, we adopted the strategy of integrating the Faster-RCNN(region-based convolutional neural networks)model with 3 different convolutional neural networks (ZF, VGG-16 and ResNet-101)respectively. By comparing the vehicle category recognition results of the 3 integrating strategies on BIT-Vehicle database and CompCars database, the strategy integrating the Faster-RCNN model with ResNet-101 shows the best result among the 3 models and recognition accuracy reaches 91.3% on BIT-Vehicle database. On the migration test CompCars database, 3 strategy models show good generalization ability.

Abstract:Multivariate public key cryptosystem is an important method to guarantee the security of communication after quantum computer appears. There are lots of practical multivariate signature schemes, but only a few multivariate encryption schemes show up. The simple matrix encryption scheme proposed by Tao, et al. is an efficient and secure multivariate encryption scheme in PQCrypto2013. However, the ratio of length of cipher text to plain text is always 2. Cubic AB encryption scheme is a way to fix it. It uses a very wide matrix to replace square matrixes (B and C), and the elements of matrix A are random quadratic polynomials. With this method, the ratio of length of cipher text to plain text could be changed easily. Besides, rank attack cannot be used to attack this scheme. At the same time, the length of cipher text and plain text will be shorter, which could make the process of decryption faster.

Abstract:This paper proposes a novel object tracking approach via graph-based manifold ranking to handle the model drift problem in the tracking-by-detection framework. The proposed approach can suppress the effects of background information caused by object deformation, scale variation and occlusion in object tracking. First, we partition the target bounding box into non-overlapping image patches, and take these image patches as graph nodes to construct k-regular graph, in which the edge weight between two neighbor nodes are measured by the distance of their low-level features. Second, we assign each patch with a weight describing the importance in representing the object, and compute it in a semi-supervised way. In particular, we initialize some patches as object patches with the weights 1, and remaining patches with the weights 0. The graph-based manifold ranking is then performed to obtain the weights of all patches. Moreover, we propose to determine the optimal scale based on multi-scale feature pyramid to address scale adaptation while improving the quality of initial patches in object tracking. Finally, we concatenate all weighted patch descriptors into a vector to represent the bounding box feature, and then integrate it into structure output (Struck) algorithm to carry out object tracking. Experimental results on several public video sequences suggest that the proposed method significantly outperforms other tracking methods.

Abstract:The cyber security of the IEC 61850-based smart substations has become an inevitable issue since they rely heavily on information and communication technologies. This paper analyzed the current security situation of smart substation from two aspects:cyber security vulnerability of smart substation and limitation of traditional cyber security evaluation methods. It proposed a security analysis and estimation method for information system and automation system, which estimated the security levels of any devices or equipment in substation separately by detecting known or unknown vulnerabilities. The method managed to assess the daily management by using static assessment tool. Through the practical test in the experimental environment for smart substation, several system vulnerabilities were detected towards information system and automation system, where the effectiveness of the cyber security analysis and estimation method for smart substation was verified. By applying this method, vulnerabilities of substation information system and automation system can be controlled, and the overall security of smart substation thereby can be enhanced.

Abstract:The establishment of the fuzzy control rule library determines the performance of the fuzzy control system. And in the fields of energy production and robot control, higher and higher control-accuracy requirements make the establishment method of conventional fuzzy control rule library sometimes no longer applicable. Therefore, we proposed an improved bacterial foraging optimization (IBFO) algorithm on the basis of swarm intelligence algorithm to improve the establishment of rule library. Firstly, the imperfectness of fuzzy rule library based on artificial experience induction was analyzed. Secondly, the improved fuzzy control system was described. Finally, the Gaussian membership function parameters of the improved TSK fuzzy system (C-ATSKFS,constant-ameliorative TSK fuzzy system) rule library were optimized. Compared with the existing method, the improved algorithm can effectively increase the recognition accuracy of the fuzzy control system. MATLAB simulation results show that the proposed novel foraging algorithm has a high practical value for the establishment of fuzzy control rule library.

Abstract:In contrast to narrow band phased array antenna, spatial dispersion and time dispersion are two dominant issues faced by the large aperture wideband phased array antennas. In this paper, the integral structure design of the subarray and digital delay filter was adopted. Firstly, the large aperture array was divided into a number of smaller size subarrays, and each of them was considered as a traditional narrow band phased array. Then, the beam forming between the subarrays was realized through digital time delay filter. After subarray partition, delay filter design in time domain was described and analyzed. Simulation results of time delay filter validate the correctness of the proposed filter design. Furthermore, system simulations prove that the hybrid structure with subarray and delay filter is able to overcome the spatial dispersion and time dispersion problems.

Abstract:In order to distinguish and analyze the vibration signals of similar working states effectively, in this paper, the method of differential bispectrum based on time series was proposed to amplify the difference of similar signals. Milling machine vibration signals which obey a stationary random process were set to the research object and their bispectra were highly similar and difficult to distinguish. In this paper, the comparative analysis result of bispectra and bispectral diagonal slices after multiple differential demonstrates that the spectra which have a high degree of similarity before differentiated become different after differentiated, and some of these differences increase with the differential times. So the analysis indicates that the differential method is an effective feature extraction method, and with this method the vibration signals of highly similarity can be distinguished and analyzed. The coupling components in signals can be enhanced. Because in various machining systems, many parameters such as speed, material and roughness are relative to bispectral features, so the parameters can be adjusted according to the analysis results to achieve the purpose of improving system functionality.

Abstract:Building module with synthetic biology to change the genetic background of E.coli and produce the 4(5),11(12)-Taxadiene that originally comes for Taxus chinensis as a secondary metabolite. First, MEP2(2-C-methyl-D-erythritol-4-phosphate) module is built and it includes four inherent enzymes, i.e. ispC, ispE, ispH and ispG. The four genes all belong to the MEP upstream pathway. Then, the MEP2 module is transferred into E.coli which contains the upstream MEP1 and downstream TC by electroporation. Finally, these gene expresses are induced with using IPTG and the products are detected by GC-MS. The MEP2 gene module is built successfully and MEP2 is convinced to enhance the production of taxadiene through several combination experiments continually. E.coli can be rebuilt to produce the botanical drug taxol precursor taxadiene and other intermediates by genic engineering.