Editor in chief：朱立光
International standard number：ISSN 1008-1542
Unified domestic issue：CN 13-1225/TS
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2016, 37(2):109-117. DOI: 10.7535/hbkd.2016yx02001
Abstract:Bladed disk assemblies are very important parts in auto engine and gas turbine, and is widely used in practical engineering. The mistuning existing commonly in the bladed disk assemblies can destroy the vibration characteristics of the bladed disk assemblies, which is one of the reasons for the high cycle fatigue failure of bladed disk assemblies, so it is necessary to research how to reduce the vibration of the bladed disk assemblies. On the basis of the review of relevant research at home and abroad, the mistuning vibration mechanism of the bladed disk assemblies is introduced, and the main technical methods of the vibration damping of bladed disk assemblies are reviewed, such as artificially active mistuning, collision damping, friction damping and optimization of the blade position. Some future research directions are presented.
2016, 37(2):118-123. DOI: 10.7535/hbkd.2016yx02002
Abstract:As the proportion of the elderly in China increases, the need for robotic assist walking is growing. The assisted-as-needed (AAN) property of a wearable walking assist robot matches a user’s biological need and improves the flexibility, appetency and friendliness of a mechanical system. To realize AAN walking and aiming at realizing master/slave flexible assist, a new hybrid control method consisting of hip joint control based on central pattern generators and knee joint impedance structured control is proposed. The adaptation of a robot's master/slave motion mode to a user's physical function, the continuous switching method for knee joint impedance structured control and its stability, and the AAN effect of the Hybrid control theory are studied, which provides a new thought for the development of wearable walking assist robots.
2016, 37(2):124-129. DOI: 10.7535/hbkd.2016yx02003
Abstract:In order to improve the milling efficiency of microchannels, the micro milling cutter is proposed to fabricate the microchannel array structures on the aluminum alloy sheet. The processing parameters such as back engagement, feed speed and spindle speed are varied to study their influence on the geometry size of microchannels. The result shows that when using the milling cutter with diameter of 0.4 mm, the width of microchannels increases with the increasing of back engagement and feed speed, especially for the back engagement. When the cutting speed is in the range of 6 000~21 000 r/min, the width size of microchannels barely changes with the increasing of spindle speed. So microchannel array structures can be fabricated through selecting optimized processing parameters.
2016, 37(2):130-138. DOI: 10.7535/hbkd.2016yx02004
Abstract:Aiming at the key technical problems encountered by domestic and foreign scholars in building the real-time monitoring system for the micro leak of three-dimensional pipe networks, the paper classifies the problems into three aspects: 1) in the extraction of fault signal frequency, how to avoid the effect of the mixed echo stack and improve the delay estimation accuracy of the correlation; 2) in network bifurcation structure, how to discern the signal propagation path, and how to locate the leak source; 3) under the uncertainly delay in transmitting and receiving information data, how to ensure the time synchronization accuracy of the real-time monitoring system for the three-dimensional pipe network leakage. Through the comparison of the monitoring technologies for the pipe network leakage at home and abroad, it shows that the acoustic emission sensor network based three-dimensional pipeline leak real-time monitoring has great advantages in detecting the weak leakage of flammable and explosive gas/liquid transportation pipelines.
2016, 37(2):139-145. DOI: 10.7535/hbkd.2016yx02005
Abstract:At present, most of the engine fault diagnosis is specific to a particular type of failure, and the mapping relationship between the analysis object features and the faults is not clear, so that the extracted features have poor universality, resulting in slow development of engine fault diagnosis, and there is no a mature diagnosis system can be used in practical application. Vibration based engine fault diagnosis research trends are analyzed both at home and abroad. The generalized force at C.G.(the center of gravity of engine) is proposed to be the analysis object for engine fault diagnosis, and clear mapping relationship between the analysis object features and the faults is achieved. It is significant for developing new engine fault diagnosis methods.
2016, 37(2):146-153. DOI: 10.7535/hbkd.2016yx02006
Abstract:A planar point set X is called a k-distance set if there are exactly k distances between two distinct points in X. Let d(x,y) be the distance of any two distinct points x,y. Let diameter D=D(X) be the longest distance of X. The diameter graph DG(XD) is composed of all diameters in X, where XD is the set of its endpoints. In this paper, the configuration of the diameter graph DG(XD) is discussed when X is a 7-distantce set. It is proved that the endpoint set XD is the endpoint set of the regular 11-sided polygon when the diameter graph has 11 cycles based on the characteristics of DG(XD) containing at most one and only odd cycle and the diameter specialty.
2016, 37(2):154-159. DOI: 10.7535/hbkd.2016yx02007
Abstract:The topological structure is one of the most important contents in the complex network research. Therein the node degree and the degree distribution are the most basic characteristic quantities to describe topological structure. In order to calculate the degree distribution, first of all, the node degree is considered as a continuous variable. Then, according to the Markov Property of growing network, the cumulative distribution function's evolution equation with time can be obtained. Finally, the partial differential equation (PDE) model can be established through distortion processing. Taking the growing network with preferential and random attachment mechanism as an example, the PDE model is obtained. The analytic expression of degree distribution is obtained when this model is solved. Besides, the degree function over time is the same as the characteristic line of PDE. At last, the model is simulated. This PDE method of changing the degree distribution calculation into problem of solving PDE makes the structure analysis more accurate.
2016, 37(2):160-166. DOI: 10.7535/hbkd.2016yx02008
Abstract:Network study combined with the generating function and percolation theory is used to study the outbreak of infectious disease with multiple infected stages among people, so the network topology is made more clear and convenient. The infected period is divided into n stages: I1, I2,…,In. The calculation of the disease outbreak threshold, the scale of outbreaks,the mean degree of infected nodes, and the mean degree of uninfected nodes in the spreading epidemic caused by one infected individual are obtained.
2016, 37(2):167-172. DOI: 10.7535/hbkd.2016yx02009
Abstract:Protein secondary structure is closely related to protein tertiary structure and function, and became a hot topic in bioinformatics. The probability graph model HMM (Hidden Markov model) is an important tool in this field. In practice, there exist problems such as: HMM training underflow, significant result differences derived from different training set, and hard process of parameter optimization. In this paper, aiming at HMM training underflow problem when predicting protein secondary structure, we put forward a method for solving the underflow problem; propose an 8-state HMM model to predict protein secondary structure for the first time; and modify parameter to be a three-dimensional parameter containing the state transition information. In order to improve the method drilling the optimal HMM, we train the initial HMM model with each sample, and get a series of new models; then average the parameters of the new models, and the obtained average parameter values are used to construct the optimal HMM model. The improved method increases the accuracy of protein secondary structure prediction, hence it is a good foundation for further improvement of HMM.
2016, 37(2):173-179. DOI: 10.7535/hbkd.2016yx02010
Abstract:PVC/Ag3PO4 composites are prepared by solution-dipping method, and the as-prepared composites are heat-treated to release HCl from PVC molecules to obtain conjugated derivative of PVC/Ag3PO4(CDPVC/Ag3PO4) composites. The CDPVC/Ag3PO4 composites are characterized by XRD, SEM, UV-vis DRS, PL and XPS. The effects of preparation conditions on the visible-light photocatalytic performances of CDPVC/Ag3PO4 composites are investigated by evaluating the decomposition of methyl orange under visible light irradiation. The results reveal that the modification of CDPVC is beneficial to the dispersion of Ag3PO4 particles, and it can obviously improve the absorbance of the CDPVC/Ag3PO4 composites in the range of visible light and the charge separation efficiency. The CDPVC/Ag3PO4 composites exhibit excellent visible-light photocatalytic acitivity and stability when the mass percentage of PVC to Ag3PO4, heat-treatment temperature and time are 0.03%, 130 ℃, and 2 h, respectively.
2016, 37(2):180-184. DOI: 10.7535/hbkd.2016yx02011
Abstract:ZnO and Fe-doped ZnO thin films are prepared on glass substrate by sol-gel method, and the surface morphology, structure and optical property are analyzed by scanning electron microscope (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD) and UV-Vis-NIR spectrophotometer. The results show that both films have a smooth surface and a hexagonal wurtzite structure with orienting along the (101) plane. Compared with the ZnO film, the surface of Fe-doped ZnO film becomes smoother, and its grain size decreases from 58.512 nm of the ZnO film to 36.460 nm. Moreover, after Fe doping, the orientation degree of (101) plane is weakened, and the optical band gap energy increases from 3.1 eV of the ZnO film to 3.4 eV.
2016, 37(2):185-191. DOI: 10.7535/hbkd.2016yx02012
Abstract:Conductive polyaniline and polyester composite fabric(PANI/PET) is prepared by in-situ polymerization, and after it is activated by hyperbranched polyamidomine/Ag+, Cu is uniformly deposited on its surface by electroless copper plating, finally Cu/PANI/PET composite fabric is obtained. Scanning electron microscope, X-ray diffraction and electromagnetic shielding effectiveness are used to analyze the samples. The results show that using PANI as the middle layer can reduce the average grain size apparently and improve the thermal stability and the friction resistance, and the electromagnetic shielding effectiveness of Cu/PANI/PET can reach 130 dB in the frequency range of 300 kHz~3 GHz.
2016, 37(2):192-197. DOI: 10.7535/hbkd.2016yx02013
Abstract:Warp-knitted spacer fabric which is commonly used in impact protection is selected as test materials to study the relationship between viscoelasticity and the performance of shock isolation. A damping test platform is built to test different specifications of warp-knitted spacer fabric including compression elastic modulus, damping ratio and the residual impact load under different impact speed. Experimental results show that there is no clear correlation between the shock isolation performance and the viscidity or the elasticity. Accordingly, viscosity-to-elasticity ratio is proposed to characterize the relationship between viscoelasticity and shock isolation performance, and it is found that appropriate viscosity-to-elasticity ratio within a certain range can help to achieve better shock isolation performance.
2016, 37(2):198-204. DOI: 10.7535/hbkd.2016yx02014
Abstract:In the process of installing inner support, the force loaded on the steel sheet pile is continuous, that is, the installation of inner support always happens after the accumulative deformation caused by inside and outside pressure difference of the steel sheet pile cofferdam. Taking the steel sheet pile cofferdam construction of a specially long span bridge as example, the paper puts forwards a spatial model of steel sheet pile cofferdam considering the construction “path” based on ANSYS. The model calculation result and the actual measurement result are compared. The results show that the model based on considering the “path” effects has a more similar calculating result with the measured value.
2016, 37(2):205-212. DOI: 10.7535/hbkd.2016yx02015
Abstract:Aiming at a class of discrete-time stochastic systems with Markov jump features, the state-feedback predictive control problem under probabilistic constraints of input variables is researched. On the basis of the concept and method of the multi-layer probabilistic sets, the predictive controller design algorithm with the soft constraints of different probabilities is presented. Under the control of the multi-step feedback laws, the system state moves to different ellipses with specified probabilities. The stability of the system is guaranteed, the feasible region of the control problem is enlarged, and the system performance is improved. Finally, a simulation example is given to prove the effectiveness of the proposed method.