Gongcheng Kexue Yu Jishu/Advanced Engineering Science

To scientifically and reasonably analyze the bending vibration frequency of the new type composite box girder bridge with corrugated steel webs, taking into account the shear deformation effect of corrugated steel webs and the shear lag effect of box girder, the Galerkin method and the Hamilton principle were used to deduce the free vibration control differential equation and natural boundary conditions of the bridge type. According to the natural boundary conditions, the calculation formula of the bending vibration frequency of the new type composite box girder bridge with corrugated steel webs under the influence of shear deformation effect and shear lag effect was solved. The results were compared with the measured results and ANSYS finite element results, and the influencing factors of the bending vibration frequency were analyzed. The results showed that the calculation results of the bending vibration frequency were in good agreement with the measured results and the ANSYS finite element results, which verified the correctness of the derived frequency calculation formula. The bending vibration frequency increased with the increase of the high-span ratio. When it was less than 0.05, the increase of the bending vibration frequency was relatively gentle. When the height-span ratio was greater than 0.05, the increase of the bending vibration frequency was more significant. The bending vibration frequency increased with the increase of the width-span ratio, but the overall increase was not obvious. The frequency increased with the increase of the thickness of the corrugated steel web, and the higher the order, the more significant the increase. The shear lag effect of the box girder had little effect on the bending vibration frequency, and the maximum error of the first 5 orders was only 6.73%. The shear deformation of the corrugated steel webs had a great influence on the bending vibration frequency, and the maximum error of the first five orders was as high as 51.18%

There are abundant moraine soil sources distributed in the Qinghai–Tibet Plateau of China, with complex historical causes, changeable material structure, and large differences in mechanical properties. Moraine landslide often occurs under the action of rainfall and ice and snow melting. The debris of landslide enters the gully and mixes with water flow, which is very easy to produce the moraine landslide—debris flow—dammed lake disaster chain, which is the key and difficult point of disaster prevention and reduction in the plateau. In recent years, the Sichuan—Tibet railway project and major hydropower development in Tibet have faced a great threat from the moraine landslide—debris flow—dammed lake disaster chain. It is a major national demand to improve the capacity of disaster prevention, reduction and relief. Moraine landslide—debris flow—dammed lake—dam-breaking flood is a chain disaster process of cascade amplification, which involves complex dynamic evolution mechanisms such as landslide initiation, movement behavior transformation, erosion amplification along the process, multi-stage river blocking superposition, and dam break water–sediment coupling. Especially under complex meteorological conditions, there are some problems such as unclear mechanism, inaccurate model, and lack of simulation technology. It is urgent to carry out the research on the complex dynamic mechanism, control theoretical model, and whole process numerical simulation of moraine landslide—debris flow—dammed lake disaster chain process. Combined with the research status at home and abroad, five research contents are further proposed: 1) Evolution of mechanical properties of moraine soil under complex meteorological conditions. 2) Dynamic disaster process and migration model of moraine landslide—debris flow. 3) Formation mechanism and simulation of moraine landslide—debris flow—dammed lake. 4) Mechanism of erosion and outburst of moraine dam and the process of flow channel expansion. 5) Mechanism of water-sediment interaction in the downstream channel and the simulation of flood evolution. Many preliminary explorations and research work have been carried out to preliminarily reveal the migration of moraine landslide debris flow and multi-stage river blocking mechanism, a dam break evolution model that can consider water erosion and intermittent collapse of the broken slope has been built, and the simulation method of moraine landslide—debris flow—dammed lake disaster chain evolution process has been discussed. The results lay a foundation for further understanding of the complex dynamic mechanism of the moraine landslide—debris flow—dammed lake disaster chain process, constructing the control theoretical model and developing the whole process numerical simulation system. And the results are expected to provide a theoretical basis for the mechanism of moraine landslide—debris flow—dammed lake disaster chain and technical support for non-engineering risk reduction and emergency disposal decision-making

In view of the problem that it is difficult or even impossible to obtain the class labels of new working condition samples under actual variable working conditions, which leads to the low fault diagnosis accuracy, a novel fault diagnosis method based on inter-class repulsive slack discriminant transfer learning (IRSDTL) is proposed. In the proposed IRSDTL, a nonnegative extended slack matrix is constructed to transform the strict binary label matrix into an extended slack label matrix for increasing the distance between different class label vectors in source domain and making the common subspace dimension no longer limited to the number of class labels. As a result, the classification error in source domain is reduced, and the generalization ability of IRSDTL is improved. Moreover, the joint distribution difference is introduced to reduce the difference between auxiliary and target domains, which can better realize the cross-domain transfer learning between two domains; the inter-class repulsive force term is constructed to promote the discriminative learning effect by increasing the distance between one class subdomain samples and the other class subdomains in the two domains. Finally, the whole framework of IRSDTL is optimized by the alternating direction multiplier (ADM) method to easily obtain the optimal parameter values of IRSDTL. The labeled samples under historical working conditions can be used by IRFDTL to perform high-precision class discrimination on the testing samples under new working conditions when there are no class labels of testing samples. Thus, precise fault diagnosis of the testing samples under new working conditions can be achieved by the proposed IRSDTL-based fault diagnosis method. The experimental results of rolling bearing fault diagnosis show that the diagnosis accuracy of the proposed method is higher than that of the other four transfer learning-based methods, and its misdiagnosis rates of misdiagnosing the three types of faults as normal state and the normal state as three types of faults are low, and the effectiveness and practicability of the proposed method are verified

In order to solve the problem of low audit efficiency due to the use of power exponent, bilinear mapping, point hash mapping and other expensive operations in the existing certificateless cloud auditing scheme, an efficient certificateless cloud auditing scheme was designed in this paper. In the key generation stage, combined with the certificateless signature technology, the user’s public and private keys were generated by the key generating center (KGC) in cooperation with the user, so that the strong dependence of auditing system security on KGC security was avoided. Consequently, the shortcomings of complex public key certificate management under the public key infrastructure (PKI) system and the inherent key escrow issues under the identity-based cloud audit scheme were solved. In the data preprocessing stage, the data was encrypted and divided into blocks. Therefore, the data content privacy was protected and the calculation and communication overhead of the scheme was reduced. In the data dynamic update stage, the virtual index data structure was used to realize the insertion, deletion and modification of data blocks. As a result, the extra computational overhead caused by label recalculation was avoided. In the data auditing stage, the task of users to verify the integrity evidence was replaced by a third party auditor (TPA), which reduces the user’s computational burden. In the section of security analysis, it was proved that the substitution attack from the cloud was resisted, the privacy protection was achieved, and the forgery attacks by two types of adversaries were resisted. In the performance analysis part, numerical analysis and comparison of the proposed scheme with the existing schemes were carried out on the JPBC library. The experiments show that the proposed scheme significantly reduces the computational cost.

When a water-rich karst cavity exists in front of the tunnel face, the thickness of the anti-inrushing rock mass between the tunnel face and the water-rich karst cavity will gradually decrease as the excavation of the tunnel progresses. Once the thickness of the anti-inrushing rock mass reaches the limit, the water inrush disaster will occur. An accurate prediction of the minimum safe thickness of the anti-inrushing structure can effectively avoid the occurrence of water inrush disaster in karst area. For the shear failure and bending failure modes of the anti-inrushing structure caused by water pressure, the corresponding mechanical models of anti-inrushing structure are established. The minimum safe thicknesses of anti-inrushing structure for the two models are calculated by using the shear strength criteria, the bending strength criteria, and the elastic thin-plate theory. The results calculated by present models are in good agreement with those calculated on the basis of the bending theory of fixed beam, the shear theory of rock column, and catastrophe theory. The results of parameter sensitivity analysis show that: 1) The water-insulating rock mass of deep-buried tunnel is prone to the bending failure, and the water-insulating rock mass of shallow tunnel is prone to the shear failure. 2) The minimum safe thickness of anti-inrushing structure is positively correlated with tunnel excavation radius, karst water pressure and Poisson’s ratio, and the order of influence degree from large to small is tunnel excavation radius, karst water pressure and Poisson’s ratio of surrounding rock. 3) The boundary conditions of the model will affect the minimum safe thickness of the anti-inrushing structure. When the excavation radius R<6 m and the karst water pressure Pw<0.35 MPa, the minimum safe thickness can be calculated based on the boundary simply supported condition. When R≥6 m and Pw≥0.35 MPa, the minimum safe thickness need to be calculated based on the fixed boundary conditions. This method provides a new way for the calculation of water gushing of circular tunnel in water-rich karst area. Finally, combined with a karst tunnel with water inrush, the corresponding parameters are substituted into the bending type Ⅰ expression, and the minimum safe thickness is generally consistent with the thickness reserved in the project, which shows that the analytical solution of the minimum safe thickness in this paper is reasonable.