Abstract:Construction of asymmetric load foundation pit adjacent to railway has a great impact on railway operation, and its deformation should be strictly controlled to reduce the impact on railway. Therefore, the design of foundation pit retaining structure is usually "conservative", and there is a possibility of optimization. In order to explore the possibility of retaining structure optimization in asymmetric load foundation pit, based on a project, the deformation and internal force of the equal-length pile retaining structure and the long-length pile retaining structure on both sides of the railway were tested, and the measured results of the two sides of the pile retaining structure were compared and analyzed. The results show that in this project, the deformation of the left and right sides of the foundation pit is small, both within the controllable range, and both the equal-length pile enclosure structure and the long-length pile enclosure structure can ensure the safety of the foundation pit and railway.Compared with the equal-length pile envelope, the maximum horizontal displacement and bending moment of the long and short pile envelope increase with the maximum horizontal displacement increase of 0.25 mm and the maximum bending moment increase of 10.14 kN·m, both of which are small. The long and short pile envelope has a good supporting effect. The horizontal displacement and bending moment of the short and long pile envelope adjacent to the asymmetric load side are larger than those far from the asymmetric load side, but the difference between them is small, and the influence of the asymmetric load on the short and long pile envelope is small.

Abstract:Based on the pre-development general characterization model of track structure deformation and theevolution of interlayer interface state induced by the deformation of high-speed railway foundation, the description function of cosine subgrade settlement was implanted and the Heaviside function was introduced to describethe contact nonlinearity between track and subgrade, so that the deformation equation of each layer of longitudinally connected ballastless track under cosine subgrade settlement was derived. The progressive approximationmethod was used to solve hyperstatic equation with contact nonlinearity, and the influence law of cosine subgrade settlement on the track structure deformation of each layer and the evolution of interlayer interface statewas analyzed. Results indicate that in the cosine subgrade settlement area, the track deforms accordingly with the subgrade settlement. When the subgrade settlement wavelength is constant, the track settlement and heaving increase with the increase of the subgrade settlement amplitude. When the settlement amplitude is constant, the track settlement increases with the increase of the subgrade settlement wavelength, but the track heaving decreases. The void area between track-subgrade and the track force curve are symmetrical, and the track overall stiffness affects the void length and height. When the subgrade settlement wavelength is 10 m, with the increase of the subgrade settlement amplitude, the void height and length increase, and it will also shift away from the settlement area as a whole. When the subgrade settlement amplitude is 10 mm, it is necessary to focus on the uneven settlement with settlement wavelength less than 20 m.

Abstract:The opening rate is an important structural parameter of the shield machine cutter, and its size is directly related to the interaction between the cutter and the excavation surface. By designing a 1∶10 model test, it realizes adjustable opening rate of cutter and real time weighing of residue, thus indirectly realizing the control of soil chamber fullness. The study analysis showed that under the condition that the actual rate of excavation is equal to the theoretical rate of excavation, increasing the rate of cutter opening can reduce the contact surface between the cutter surface and the excavation surface, thus reducing the cutter torque, showing a 10% increase in cutter opening rate and an approximate 5.8% reduction in cutter torque. At the same emergence rate, the opening rate of the cutter has no significant effect on the maximum settlement of the ground surface. The slag soil on the cutter gap can have the support effect on the excavation surface when the soil compartment is nearly full.

Abstract:Based on the foundation pit engineering case of the pit-in-pit of Nanchang Aixihu tunnel，the deformation characteristics in different spatial forms of the pit are studied and analyzed by using the numerical calculation software. The influence rate of foundation pit deformation is proposed, which can be used to comprehensively judge the sensitivity of pit spatial shape parameters to foundation pit deformation. The results show that the influence factors of the spatial form characteristics of the deformation characteristics of the pit in pit are mainly the relative size, relative position of the inner and outer pits and the insertion ratio of the enclosure structure. The specific sensitivity relationship is as follows: relative depth ＞ relative position ＞ insertion ratio of the outer pit enclosure structure ＞ insertion ratio of the inner pit enclosure structure ＞ relative width.

Abstract:To study the stress and deformation of ballastless track CWR on rigid frame bridge, based on the principle of beam-slab-rail interaction, the models of CRTSⅢ slab track and CRTSⅠ bi-block track jointless track on rigid frame bridge were established respectively. The longitudinal forces and displacements of each structure under the conditions of expansion, deflection, braking and rail breaking were calculated, and the static characteristics of two kinds of ballastless track structures were compared and analyzed, so as to provide consultation for the track structural design of CWR on rigid frame bridge. The results show that under temperature load and train load conditions the rail longitudinal force of CRTSI bi-block track CWR on rigid frame bridge is smaller, but the relative displacement of rail and track slab increases significantly, which may lead to potential safety hazards; Under the train braking load condition, the longitudinal stress of the rail and the relative displacement of the rail slab of CRTSⅢ slab track CWR on the rigid frame bridge are smaller; Under the broken track condition, the broken joint value of CRTSI bi-block track CWR on rigid frame bridge exceeds the allowable limit of the specification. Accordingly, CRTSIII slab track is recommended for rigid frame bridge.

Abstract:The waterproofing of shield tail sealing system is an important factor affecting the safety of shield construction. A laboratory test of the shield tail sealing system was designed, and a corresponding simulation model was established based on the computational fluid dynamics to analyze the characteristics of waterproofing failure. The changes of volume distribution, pressure field and velocity field of two-phase fluid in the process of external hydraulic intrusion were analyzed, and the influence of shield tail structure parameters, tail brush parameters and grease parameters on seal performance was studied. The results show that: increasing the number of shield tail brushes can effectively improve the waterproofing ability；in the process of waterproof failure, the peak point of flow velocity appears at the tail brush of shield, and the expansion distribution of flow velocity is consistent with the volume distribution of water；the permeability of shield tail brush and the viscosity of grease are the sensitive factors affecting the initial leakage time； by reducing the permeability of shield tail brush and increasing the viscosity of grease, the initial leakage time can be delayed, and the waterproof ability can be effectively improved.

Abstract:In order to study the environmental vibration caused by high -speed trains passing through elevated tracks, an experimental test site was selected, corresponding to a stretch of the railway connection between Shanghai and Kunming. Field measurement and finite element method were used to obtain the ground vibration characteristics. Comparing the calculated value with the measured value, the results show that the ground lateral vibration acceleration caused by the high-speed train passing through the bridge is slightly larger than the vertical vibration acceleration, and the main peak frequency point of the frequency spectrum curve could be regarded as the resonance frequency induced by the periodic load. The excellent frequency distribution range of lateral and vertical acceleration is 10~80 Hz, and the acceleration amplitude of each single frequency in the frequency band tends to fluctuate and decay with increasing distance. When the vibration peaks of different frequencies meet, the vibration superposition at the meeting point shows amplification. The frequency band corresponding to the maximum vibration level of lateral and vertical acceleration shows mainly at 3.15 Hz of the range of 25~63 Hz; The numerical results of ground vibrations show an acceptable agreement with the real measurements in amplitude and changing trend, and the maximum error of acceleration Z vibration level is 1.4 dB. Hence the finite el ement model meets the accuracy requirement, which proves that this method can be used to predict the environmental vibration response.

Abstract:Temporal logic involves the logic characteristics of the system whose state changes with time. It is widely used in software and hardware verification and is the basis of model checking. Based on the different descriptions of time models and in order to deal with more complex computational characteristics, different kinds of temporal logics are derived, which have different expressive power. It is particularly important for the formal specification of system models to correctly understand their expressive power. Firstly, this paper introduces the discrete-time model LTL, CTL and CTL*, the continuous time model ITL and PTL, and the expressive power and the differences between them are elaborated in details. Then, various temporal logic proposed to describe random, real-time, hybrid and open-system complex behaviors are summarized, and their characteristics and application scopes are presented. Finally, the future research direction of temporal logic is discussed.

Abstract:Severe convective weather is one of the important factors affecting aircraft flight. In order to reduce the economic waste of diverting aircrafts and the probability of encountering hazards, it is necessary to accurately delineate and predict the restricted areas. The first step is to extract the data on the thunderstorm points that affect aircraft flight. The initial polygon of the static flight restricted area is delineated using Graham algorithm. The change in geometry of the flight restricted area is predicted using the distance-mean method. Markov theory is introduced to predict the change of the center point position of the flight restricted area through the class state transfer matrix. The angular increment method is proposed to predict the angular change of the center point of the flight restricted area. The results show that the prediction accuracy is high and the deviation is low for radar weather data with low temporal resolution, and the prediction area can be updated in real time. The dynamic prediction is achieved on the basis of the static flight restriction zone, which makes the prediction results closer to the actual change.

Abstract:In order to find out the wheel -rail rolling contact behavior of the train under traction and brakingconditions, so as to provide a theoretical basis for the research on wheel-rail damage mechanism in the future,taking CRH2-300 EMU wheel-rail as the research object, the wheel-rail contact mechanical behavior based ontraction and braking performance adhesion coefficient model is studied by finite element simulation. The resultsshow that the friction coefficient based on empirical model is significantly greater than that based on traction andbraking model and Shinkansen model. The friction coefficient of Shinkansen model is close to that based ontraction braking performance model. Under the traction condition, the tangential force image shows the form oftwo-point contact, and the point-contact tangential force at the front end along the running direction is significantly greater than that at the rear end of the running direction. Under the braking condition, the tangential forceis of single point contact at the beginning and then a two -point contact. At the wheel rail contact point, theshear stress of the wheel S23 is in a circular arc shape, and the circular arc trend is consistent with the direction of the wheel angular velocity. The circular arc trend of the shear stress of the rail and the wheel S23 is symmetrical.

Abstract:A series of PDAAM-co-PNIPAM-co-Mu copolymers were synthesized by RAFT polymerization from diacetone acrylamide (DAAM)，N-isopropylacrylamide (NIPAM) and ureidopyrimidinone-containing monomer (M_u). Smart hydrogels crosslinked with acylhydrazone dynamic covalent bonds were obtained by the reaction between PDAAM-co-PNIPAM-co-Mu and adipic dihydrazide(ADH). The structure, mechanical properties and intelligent properties of intelligent hydrogel were investigated by scanning electron microscope (SEM)，rheometer and universal testing machine. Due to the introduction of ureidopyrimidinone(UPy) hydrogen-bonding units into the network, the mechanical properties of the hydrogels were reinforced, and the compression strength of the hydrogel was increased by 4 times. Meanwhile, the hydrogels exhibited pH and temperature dual-responsive and self-healing properties, and the compression strength was increased by 30 times after heating.

Abstract:The inconsistencies between the monomers of the power battery pack will occur due to the factors such as production process and service environment, which will affect the service life and driving safety of the battery. To meet the requirement of abnormal monomer diagnosis under inconsistent fault of power battery pack, based on data of vehicle network platform, a method of power battery monomer identification and early warning is proposed based on isolated forest method. The fault threshold T=0.75 is determined by counting the scores of normal and abnormal samples. At the same time, the data flowing into the diagnosis model is updated in real time by combining the sliding window to realize the recognition and warning of inconsistent monomers. The results show that the method can effectively identify inconsistent monomers, with the recall and accuracy of 0.91 and 0.95 respectively. When the size of sliding window is 15, the warning effect of real-time fault is the best. The research obtained in this paper is beneficial to reduce or avoid electric vehicle fire and explosion accidents caused by inconsistent power batteries, and is of great significance to promote the further popularization of electric vehicles.

Abstract:The existence of nontrivial solutions for fractional Schrödinger-Poisson equations in a bounded domain is discussed. Under different assumptions of nonlinearities, existence and multiplicity by variational methods and symmetric Mountain Pass theorem are obtained.

Abstract:In a typical optomechanical system, the decay rate of an optical cavity must be smaller than the frequency of a mechanical oscillator(resolved sideband regime) in order to generate strong mechanical squeezing generally. This is difficult to implement in experiments. A scheme is proposed to generate strong mechanical squeezing and steady state entanglement in a hybrid atom-optomechanical system in the highly unresolved sideband regime (the decay rate of the optical cavity is much larger than the frequency of the mechanical oscillator). Two two-level atomic ensembles and two lasers with different amplitudes can be used to control the optomechanical system and the resolved sideband limit can be relaxed. Our results are as follows: if two atomic ensembles are put into the optomechanical system, the strong mechanical squeezing beyond 3 dB is achieved even in the highly unresolved sideband regime; the steady state entanglement between the cavity and mechanical resonator can also be obtained.

Abstract:In recent years, MOFs derived carbon-based materials have been widely used as green sorbents and efficient persulfate catalysts. This paper introduces the preparation process of MOFs materials and analyzes their advantages and disadvantages. The mechanism of activated persulfate degradation of organic wastewater by MOFs derived carbon materials was reviewed in details, including MOFs derived metal compounds, MOFs derived metal-free carbon materials and MOF derived transition metal/carbon composites. Finally, the application of MOFsderived carbon material adsorption removal and adsorption/oxidation coupling treatment of polluted organic wastewater were summarized.