2016 volumne 37卷 Issue 05
Li Peilong, Rao Wenyu, Feng Zhengang, Li Jiange
Abstract: The dynamic modulus is one of the important characterization parameters of the viscoelastic dynamic response of asphalt mixture. Three graded asphalt mixtures were selected to carry out performance tests of asphalt mixture under different test conditions. According to the change law of test temperature, the attenuation model of dynamic modulus with test temperature under different loading frequencies was obtained; the influence of loading frequency on the attenuation rate of dynamic modulus was analyzed, and the shift factor of dynamic modulus was discussed, and the The main curve of dynamic modulus. The results show that as the loading frequency increases, the dynamic modulus of asphalt mixture increases gradually, but the higher the temperature, the smaller the increase; the dynamic modulus has an exponential relationship with the increase of temperature Attenuation, the higher the loading frequency, the greater the attenuation rate, and the dynamic modulus of modified asphalt mixture AC-13 has the smallest decay rate with temperature; at higher temperatures (such as 55°C), the dynamic modulus of different loading frequencies The difference is very small. The dynamic modulus master curve and displacement factor can better describe the influence of loading frequency and test temperature on the viscoelastic response of asphalt mixture.
Sun Zengzhi, Tian Junzhuang, Yang Kai, Zhang Lei, Chen Huaxin
Abstract: Based on the pier concrete of Qinghai Dexiang Expressway Bridge, the main soluble salt content along the line was analyzed. Through indoor simulation experiments, 7 kinds of corrosion solutions were prepared, and 4 kinds of mix ratio concrete were designed. The effect of salt on the durability of concrete under the action of dry-wet cycle was studied from the aspects of rate and relative elastic modulus. The results show that under the action of dry-wet cycle, single salts such as Na2S04, MgSO4, and NaCl solution have different damage forms and degrees to concrete. The same; in the compound salt solution, the corrosion damage effect of the compound salt on concrete will be superimposed, and the greater the concentration of the solution, the more serious the corrosion damage of concrete; the addition of cement-based self-healing materials and fly ash can improve the resistance of concrete to salt corrosion. destructive ability.
Wang Luyu1,Zhu Ye2,Gao Liping2,Xu Jiaqiang2
Abstract: Using aluminum isopropoxide, orthophosphoric acid, tetramethylguanidine and lanthanum nitrate as reaction raw materials, AIP04-5 zeolite molecular sieve was successfully prepared by one-step hydrothermal method, and it was doped with rare earth element lanthanum (LaAPO-5) to Obtain good gas-sensing performance. It can be seen from the scanning electron microscope that the obtained La-doped zeolite molecular sieve is a small spherical particle, and is packed into a fluffy cotton floc. The synthesized material is constructed as a sensitive material for a quartz crystal microbalance humidity sensor A resonant humidity sensor, compared with the undoped LaAPO4-5, the doped LaAPO-5 has a higher sensitivity in the detection of the whole humidity range, and has a better linear relationship and a shorter response time. /recovery time, where the recovery time can be as fast as 3 s.
Shi Xiaohua, Yan Shaoge, Zhang Weijie
Abstract: Aiming at the deficiencies in flexibility and heat resistance of epoxy acrylic resin when it is applied to UV photocurable solder resist ink for flexible circuit boards, a kind of epoxy acrylic resin with suitable molecular weight was prepared by different monomer combinations and imidization method. and soluble polyimide with good heat resistance, and used it to modify epoxy acrylic resin. The results show that the best process for preparing the polyimide (PI) is to mix the molar ratio of 1:0.505:0.505 3,4’-ODA, BPDA, ODPA were reacted for 2 hours to synthesize polyamic acid (PAA), and then the polyamic acid was synthesized at 90°C by the chemical imine method of adding catalyst triethylamine and dehydrating agent acetic anhydride. Dehydration for 4 hours to synthesize polyimide. The polyimide synthesized under this condition has a molecular weight of 2.64×104 and a decomposition temperature of 508°C. It is used for modification of epoxy acrylic resin to increase the decomposition temperature of the product from 291°C to 374°C. , the heat resistance has been improved.
Zhang Yonghui, Liu Chunyan, Liu Huanzhen, Gong Feilong, Li Feng
Abstract: The bonsai-shaped three-dimensional material was prepared for the first time by hydrothermal method. The XRD and thermal analysis test results showed that the prepared material was composed of basic zinc carbonate (Zn4CO3(OH)6·H2O) and ZnO, and the product was calcined at high temperature to obtain good crystallinity and ZnO material with hole-like structure on the side and bottom. The morphology of the material was systematically characterized by FESEM, and it was found that the bonsai-like ZnO was grown symmetrically by self-assembly of nanosheets, and each layer of growth would get a regular hexagonal structure .The material was prepared as a gas sensor and its gas-sensing performance was studied. The results showed that the constructed gas sensor had the highest sensitivity to ethanol gas at 340°C, and also had good response-recovery characteristics and stability. The material could Applied to improve the design and fabrication of ethanol-based sensors.
Zheng Yuanxun1,Yang Peibing1,Kang Haigui2
Abstract: The research status and development trend of the durability of concrete structures under freeze-thaw environment at home and abroad are systematically summarized and summarized, and the future research direction in this field is prospected. Based on the study and analysis of domestic and foreign literature, the freeze-thaw environment The failure mechanism of concrete, freeze-thaw test methods and standards are summarized and sorted out; and the durability research methods of non-prestressed concrete structures and prestressed concrete structures are summarized from the theoretical research and numerical simulation methods, and the enhancement Finally, the research trend of the durability of concrete structures under the freeze-thaw environment is analyzed. The research shows that some research results have been achieved in the study of the durability of concrete structures under the action of freeze-thaw environments, but based on the large-scale prediction The durability research of stress components under the action of freeze-thaw environment has not been reported yet, and it should be taken as the next key research direction.
Lin Shangshun1;Chen Baochun2
Abstract: It has been pointed out in the literature that the moment increase coefficient of reinforced concrete eccentric compression columns is related to the reinforcement ratio, but the calculation of the bending moment increase coefficient in China’s structural design code does not consider the influence of the reinforcement ratio. Therefore, in the collected 33 Based on the data of the root specimen, combined with the finite element analysis carried out, the theoretical analysis was carried out, and the finite element parameter analysis was carried out at the same time. The results show that the curvature influence coefficient in the calculation formula of the bending moment increase coefficient is not only related to the slenderness ratio and eccentricity It is also related to the ratio of ribs; in the case of the same slenderness ratio and eccentricity, the greater the ratio of ribs, the greater the coefficient of bending moment increase. According to the analysis results, a curvature influence coefficient considering the influence of ratio of ribs is proposed The calculation formula was used to verify the calculation accuracy of the formula by using the collected literature samples.
Yan Anzhi1,Tao Tianzeng2,Zhang Zhenhua1
Abstract: Many structures in engineering practice can be simplified as a cantilever beam with concentrated mass at the end. The author established the finite element model of the cantilever beam with concentrated mass at the end by numerical simulation software, and carried out modal analysis. The concentrated mass at the end was studied. The effect of mass change on the natural frequency of the cantilever beam was established, and the model of the cantilever beam with I-type cracks (with lumped mass at the end and without lumped mass at the end) was established, and the position and depth of the crack were changed to study the crack depth. and the crack position on the frequency variation of the cantilever beam. Through comparison, it is found that the closer the crack is to the end, the smaller the impact on the beam frequency, and the concentrated mass has a certain influence on the natural frequency of the cracked cantilever beam.
Ruan Baoyu1,Zhao Wenen2
Abstract: Lycopene was separated from the crude extract of red watermelon pulp by high-speed countercurrent chromatography (HSCCC). Under the action of ultrasonic waves, v petroleum ether: v acetone = 2:1 was used as the extraction solvent to extract lycopene from 400 g of mature watermelon pulp homogenate Crude lycopene, until all the pigments are extracted. Then use a two-phase solvent system composed of vn-n-hexane:v acetonitrile:v dichloromethane=20:12:7 for preparative high-speed countercurrent chromatography separation, from about 223 mg About 30 mg lycopene was obtained from the crude extract. Calculated by the peak area normalization method, the product purity was 98.3%.
Deng Wanyu; Li Li; Niu Huijuan
Abstract: With the rapid expansion of data scale, the serial neural network structure based on a single machine is facing huge computing challenges, and it is difficult to meet the expansion requirements in real applications. Based on the extreme learning machine (extreme learning machine, ELM), based on the Spark parallel framework A parallel extremely fast neural network learning method is proposed, which is encapsulated with the unique RDD efficient data set management mechanism of the Spark platform, and the high-complexity matrix calculation in large-scale data is parallelized to achieve ELM accelerated solution. A set of Map and Reduce operations can complete the training of the algorithm. The experimental results on a large number of real data sets show that the parallel ELM algorithm based on Spark has achieved significant performance improvement compared with the serial ELM.
Lu Yanhui1,Li Zhaoping2,Han Shujun1,Yang Shouyi1
Abstract: In order to guarantee the different service requirements of users, implementing differentiated services for different services and realizing spectrum switching management is one of the main problems that need to be solved urgently in communication systems. The traditional method to study switching problems is Markov modeling, and the Markov model has the characteristics of no memory, and The problem of state space explosion is easy to occur, which makes the research on spectrum switching strategies mostly stay in single-service OFDMA systems. Applying colored Petri nets (colored petri nets, CPN) to develop spectrum switching strategies suitable for multi-service OFDMA systems, established four kinds of The CPN model of the spectrum switching strategy for switching users and the transmission performance of new users. The simulation results show that CPN can overcome the limitations of the Markov model and facilitate the analysis of complex systems, especially the spectrum switching strategies of multi-service systems whose arrival law obeys multiple mathematical distributions .
Gao Jinfeng1,Yu Ya1,Zhang Xuhui2,Si Chengkun3
Abstract: In the fixed-frequency PWM (pulse width modulation) control mode, the current spectrum energy of the transmitting/receiving coil is concentrated, resulting in a high level of external electromagnetic interference. The chaotic carrier frequency modulation technology is applied to the high-frequency inverter of the electric vehicle wireless charging system. This This modulation technique can broaden the current spectrum of the transmitting/receiving coil, distribute the same transmission energy on different frequency lines similarly randomly, thereby improving the frequency spectrum of the space electromagnetic field and reducing the external electromagnetic interference level of the wireless charging system. Computer simulation and The experimental results have proved the effectiveness of the method.
Cheng Xian1;Wang Haiyan2;Yan Guangchao2;Jiao Lianyao3
Abstract: The electric field distribution of the gas chamber of the gas-insulated metal-enclosed switchgear is a key issue to be considered in its structural design. The electric field distribution in the gas chamber should be as uniform as possible to avoid flashover and discharge at the place where the field intensity is concentrated. Direct use of SF6/N2 mixed Gas instead of pure SF6 gas as the insulation medium of 35 kV voltage level GIS gas chamber cannot meet its insulation requirements. To solve this problem, the author conducts electric field analysis and structural optimization research on GIS gas chamber. Using Solidworks software to establish a three-dimensional model of GIS gas chamber structure and conduct limited Meta-analysis; Based on the electrostatic field theory, the electric field numerical calculation of the gas chamber model is carried out. The calculation results show that the electric field strength at the isolation fracture, grounding fracture, and insulating tie rods in the gas chamber is too high. The structure of these parts is optimized, and the optimized The gas chamber model is verified and calculated. The calculation results prove that the electric field intensity in the optimized GIS gas chamber is significantly lower than before, and the maximum value of the electric field strength is lower than the insulation strength of the alternative gas, and the alternative gas can meet the insulation requirements of the optimized air chamber.
Liu Benxue, Lin Chaoyun, Guo Peidong, Li Liangyu
Abstract: In order to demonstrate the superiority of the active suspension in improving the ride comfort of the vehicle, on the basis of establishing the 1/4 active suspension model of the vehicle and the stochastic road excitation model, the linear optimal control is used as the control strategy of the active suspension, and the design The linear optimal controller is used to establish the active suspension simulation model in the frequency domain and time domain by using MATLAB, and the active suspension is simulated in the frequency domain and time domain respectively on the random road excitation and compared with the passive suspension. The results show that : The active suspension can effectively reduce the body acceleration, tire dynamic load and suspension deflection, thereby significantly improving the ride comfort and handling stability of the car. The model establishment, optimal design and simulation analysis of this design are the further development of the active suspension. It provides a useful reference for research and practical application.
Lei Zhengbao, Liu Zhuchun, Liao Zhuo
Abstract: Since there are as many as nine vehicle collision conditions and the collision forces of different conditions vary greatly, the final overall topology configuration will be more inclined to the conditions with large collision forces when performing multi-condition parallel topology optimization on the car body, and the front, Due to the different collision forces in the passenger area and the rear of the vehicle, the optimal optimal mass ratio is also different, so the multi-condition crashworthiness topology optimization of the entire body cannot be carried out at the same time. In order to obtain a vehicle configuration with a reasonable and effective material distribution, the same The model conducts a comparative analysis of the overall topology optimization and sub-area topology optimization, and proposes a topology optimization of the seating area first, and then optimizes the topology of the front and rear of the vehicle when the structure of the seating area is known, and finally assembles the topology of the entire vehicle. Topology optimization design method for crashworthiness of body-in-white based on optimization model.
Zhu Qiang1,Du Peng1,Wang Jianjun2,Qin Dongchen1
Abstract: Using ANSYS to establish an axisymmetric model of the casing joint, focusing on the analysis of the sealing performance of a special threaded casing joint cylindrical/spherical sealing structure, respectively for the three working conditions (machine-tight, machine-tight+tension, machine-tight+internal) The distribution law of the contact pressure and equivalent stress of the sealing end is obtained, and the contact pressure and equivalent stress of the sealing end under different working conditions are compared and analyzed, revealing that the tensile load and the internal pressure of the casing have an impact on the structure. The impact of sealing performance. The results show that the contact pressure and equivalent stress of the cylindrical/spherical sealing structure meet the sealing requirements, which provides theoretical guidance for the further optimization design of special threaded casing joints.
Xie Jinfa, Zhang Jinglong
Abstract: Based on the non-smooth surface of bionics, the non-smooth surface formed by the pit-type non-smooth units arranged in rectangular arrangement, diamond arrangement and equidifferential arrangement was respectively arranged on the top of the MIRA straight-back car model, and the influence of different arrangements on the aerodynamic drag of the car was analyzed. .By applying the CFD method, the finite element analysis software ANSYS is used for numerical simulation. The simulation results show that the pit-shaped non-smooth surface arranged in a rectangle can obtain the best aerodynamic drag reduction effect, and the total drag reduction rate can reach 6.52%. Further The analysis found that the reason is that the concave-shaped non-smooth unit body arranged in a rectangle can better reduce the pressure difference resistance and surface friction resistance of the model, and finally reduce the aerodynamic resistance of the model.
Zhao Shujun, Duan Shaoli, Zhang Xiaofang, Li Lei, Liu Xiaomin
Abstract: The calibration method of the zoom camera is studied. The self-calibration method based on the two vanishing points is used to calibrate the general parameters of the zoom camera under two fixed focal lengths. By comparing with Zhang Zhengyou’s calibration method and the results of the machine vision software Halcon calibration, the results are verified. The feasibility and robustness of this method are verified. In order to better reflect the zoom characteristics of the zoom camera, a thick lens model that can more accurately describe the zoom camera is established. The author performs SIFT feature matching on the zoom image, and according to the matching point pair The linear equations are established, and the least square method is used to estimate the zoom center of the zoom image. In addition, the optical center displacement between different focal lengths is also calculated. The experimental results show that there is an obvious gap between the optical center displacement and the focal length, which shows that The thick lens model is more suitable for describing the zoom lens of the camera.
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