Editor in chief：朱立光
International standard number：ISSN 1008-1542
Unified domestic issue：CN 13-1225/TS
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2018, 39(2):91-98. DOI: 10.7535/hbkd.2018yx02001
Abstract:Hot stamping of high strength steel is an approach to achieve the lightweight of auto-body and guarantee the security of automobile simultaneously, and it has been widely used in the automobile and steel industry in recent years. Due to the high temperature process, the mechanical behaviors of high strength steel are strongly dependent on the deformation temperature and strain rate, which presents a challenge to evaluate the thermal formability accurately. On the basis of the review of the process characteristics of hot stamping, the experimental and theoretical predicted research on the thermal forming limit diagram (FLD) published by overseas and domestic scholars is analyzed. The deficiencies of FLD are discussed, then the evaluation methods for formability based damage mechanics are introduced, which include the continuum damage mechanics and mesoscopic damage mechanics. The calibration methods for damage parameter are also discussed. Finally, some suggestions are given: to accurately study the damage evolution of high strength steel in hot stamping, the influence of deformation temperature, strain rate and stress state must be fully considered. To achieve this, the method combined experiment, theory and numerical simulation must be adopted based on the technological characteristics of the hot stamping technology. This work can provide a reference for the improvement of damage theory in hot stamping of sheet metal, and the related research results can be used to guide process optimization of actual hot stamping, which can effectively shorten the development cycle of new products.
2018, 39(2):99-106. DOI: 10.7535/hbkd.2018yx02002
Abstract:Circle detection is one of the most basic and important tasks in machine vision. In order to accurately determine the circle location in complex background images, a new joint algorithm that combines the model of support vector regression with the three-point fitting circle detection algorithm is proposed. The different types of circular samples are trained by the support vector regression model in the algorithm. So the hyperplane equation f(x) can be obtained. Taking the f(x) as the center line, one similar circular ring with the width of 2 can be constructed. The points in this interval are considered as the circular boundary points. Then, the center and radius can be calculated based on the three-point fitting circular geometry algorithm, so as to achieve the purpose of identifying the circle. The experimental results show that the circular boundary information can be obtained from the relatively noisy background images by learning the training samples thereby determining the location of the circle, which has some advantages over using only a certain circular recognition algorithm. In the field of machine vision positioning with circles, this joint algorithm has important theoretical research value and practical significance.
2018, 39(2):107-114. DOI: 10.7535/hbkd.2018yx02003
Abstract:In order to optimize practical characterization method of rollover warning indices for truck, the theoretical analysis of correlation and dynamic simulation test validation are carried out for three kinds of rollover indices (lateral acceleration, roll angle, lateral load transfer rate). Based on the simplified roll dynamics model of vehicle, the model about three kinds of rollover index correlation is deduced, and a nonlinear multi-degree-of-freedom dynamic model with the actual parameters of a certain light truck is established in Matlab/Simulink. The two groups of step-steering with setting the vehicle speed and steering angle changing independently, is used to study the quantitative correlation of vehicle rollover indices and practical characterization methods. The linear quantification model between roll angle or lateral load transfer rate and lateral acceleration is obtained by fitting the distribution of the final stability point. It is verified that the practical characterization method of rollover warning indices that uses lateral acceleration to indirectly characterize roll angle and lateral load transfer rate is feasible. The results show that with the increase of the steering wheel angle and the vehicle speed, the roll angle, the lateral load transfer rate and the lateral acceleration can quickly be tend to stable state in the whole simulation process. The vehicle roll angle and lateral load transfer rate calculated by this method provide a good index basis for the design of the following vehicle rollover warning control system.
2018, 39(2):115-124. DOI: 10.7535/hbkd.2018yx02004
Abstract:Line structured light sensor (LSLS) is composed of a laser line projector and a camera. The profile data of the measured object can be obtained by analyzing the perturbed stripe images captured by the camera. The sensors have the advantages of simple construction, low cost, non-contact, high efficiency and flexible application. Thus, they have gained extensive application prospects in research and industry. The measuring technique by use of the LSLSs is reviewed in four aspects as quality control of stripe images and center extraction, sensor calibration, collaborative measurement via multiple sensors, and the integration of the sensor with motion axes. The current problems in the research and the application of this measuring technique are summarized, and the future research trends can be concluded as further improving the measuring accuracy, enhancing the sensor adaptability, and developing the structured light sensor based intelligent measuring system.
2018, 39(2):125-134. DOI: 10.7535/hbkd.2018yx02005
Abstract:In order to study the influence of input time delay on the stability of Timoshenko beam system and stabilize the Timoshenko beam system with input delay and load, by using the Backstepping method, a new controller is designed to compensate for the input delay, and then a stable closed-loop system is obtained. At first, a delay-free system is given, which is equivalent to the original time-delay system. Then, a bounded linear transformation is constructed, and it is proved that the linear transformation is bounded and invertible. Finally, the delay-free system is transformed into a stable target system by the linear transformation, and the corresponding controller is given, which implies that the delay-free system is equivalent to the target system. Therefore, the original time-delay system can be stabilized by the feedback control law. The negative effect of input delay on elastic system is solved by this method, which enriches the controller design method and stability theory of distributed parameter control system, and has a certain theoretical significance in engineering practice.
2018, 39(2):135-141. DOI: 10.7535/hbkd.2018yx02006
Abstract:In order to enrich the stability and bifurcation theory of the three dimensional chaotic systems, taking a quadratic truncate unfolding system with the triple singularity equilibrium as the research subject, the existence of the equilibrium, the stability and the bifurcation of the system near the equilibrium under different parametric conditions are studied. Using the method of mathematical analysis, the existence of the real roots of the corresponding characteristic equation under the different parametric conditions is analyzed, and the local manifolds of the equilibrium are gotten, then the possible bifurcations are guessed. The parametric conditions under which the equilibrium is saddle-focus are analyzed carefully by the Cardan formula. Moreover, the conditions of codimension-one Hopf bifucation and the prerequisites of the supercritical and subcritical Hopf bifurcation are found by computation. The results show that the system has abundant stability and bifurcation, and can also supply theorical support for the proof of the existence of the homoclinic or heteroclinic loop connecting saddle-focus and the Silnikov's chaos. This method can be extended to study the other higher nonlinear systems.
2018, 39(2):142-148. DOI: 10.7535/hbkd.2018yx02007
Abstract:To improve the efficiency for large-scale nonsmooth optimization problems and overcome the large storage requirements and complex computation of other algorithms, a modified HS conjugate gradient algorithm for nonsmooth optimization problems is proposed. A new search direction based on the classical HS conjugate gradient method is given, then the Moreau-Yosida regularization technique and the Armijo-type line search technique are used to design the algorithm. The sufficient descent condition and the trust region are satisfied for this algorithm. Under suitable conditions, the global convergence of the new algorithm is proved. The preliminary numerical experiments show that the new algorithm is more efficient than the LMBM method for nonsmooth unconstrained optimization problems. The presented algorithm is efficiently for solving nonsmooth optimization problems since it has good convergence property and good numerical performance.
2018, 39(2):149-153. DOI: 10.7535/hbkd.2018yx02008
Abstract:Perylenetetracarboxylic diimides (PDI) and their derivatives have been paid more attention due to their special photophysical and electrochemical properties. The modification on molecular structure of PDI aimed at changing the photophysical properties is one of an important means to obtain functional materials of PDI. An asymmetric PDI containing polypeptide chain at one imide nitrogen is synthesized by stepwise aminolysis reaction of 3,4,9,10-perylenetetracarboxylic dianhydride. The influence of reactions on yield is then inquired. The optimal reaction condition are determined as follows: molar ratio of PDI to cyclohexylamine, 1∶6; the solvent volume ratio of ethanol to water, 4∶1; reaction temprature and time, 70 ℃ and 6 h, the intermediate N-cyclohexyl-3,4,9,10-perylenetetracarboxylic-3,4-anhydride-9,10-imide. In the presence of the catalyst DMAP, this intermediate undergoing aminolysis reaction with L-Ala-D-Leu-(N-Me)-Ala-D-Leu-Ally affords polypeptides with asymmetric PDI in imidazole for 4 h at 120 ℃, and the tatal yield is above 32.6%. The product structure is characterized by ESI-MS and 1H-NHR. The process is simple and mild conditions, which provides a convenient synthetic route for the preparation of asymmetric PDI compounds.
2018, 39(2):154-158. DOI: 10.7535/hbkd.2018yx02009
Abstract:In order to overcome the difficulty to separate and purify the intermediate, solve the problem of quaternary ammonium salt removal，the synthesis of (2S,4S)-N-tert-butoxycarbonyl-4-fluoroproline which is a key intermediate of polypeptides and peptidomimetic drug is studied. The target compound is synthesized from (2S,4R)-4-hydroxyproline via esterification, amino protection, and hydroxyl activation-fluorination-hydrolysis tandem reaction. Hydroxyl activation, SN2 fluorine substitution and ester hydrolysis reaction are completed as a tandem reaction. After the hydrolysis reaction, the product is precipitated from the aqueous solution during the process of adjusting the pH, and the target compound can be directly obtained through filtration. The reaction factors and parameters are optimized, The optimized conditions are as follows: in esterification reaction, n(SOCl2)∶n(substrate)=1.2∶1.0; in amino protection reaction, n((Boc)2O)∶n(compound 1)=1.2∶1.0; in trifluoromethyl sulfonylation reaction, n((Tf)2O)∶n(compound 2)=1.1∶1.0,n(pyridine)∶n(compound 2)=1.2∶ 1.0. The total yield rate is 57.9% after optimization, and the purity is 98.3%. The structure of target compound is confirmed by 1H-NMR and 13C-NMR. This protocol has advantages of mild reaction conditions and simple operation, and is suitable for industrial production.
2018, 39(2):159-165. DOI: 10.7535/hbkd.2018yx02010
Abstract:The traditional fuzzy clustering algorithm uses Euclidean distance as the similarity criterion, which is disadvantageous to the multidimensional data processing. In order to solve this situation, Mahalanobis distance is used instead of the traditional Euclidean distance, and the optimization of fuzzy clustering algorithm based on Mahalanobis distance is studied to enhance the clustering effect and ability. With making the initialization means by Heuristic search algorithm combined with k-means algorithm, and in terms of the validity function which could automatically adjust the optimal clustering number, an optimization algorithm KM-FCM is proposed. The new algorithm is compared with FCM algorithm, FCM-M algorithm and M-FCM algorithm in three standard data sets. The experimental results show that the KM-FCM algorithm is effective. It has higher clustering accuracy than FCM, FCM-M and M-FCM, recognizing high-dimensional data clustering well. It has global optimization effect, and the clustering number has no need for setting in advance. The new algorithm provides a reference for the optimization of fuzzy clustering algorithm based on Mahalanobis distance.
2018, 39(2):166-175. DOI: 10.7535/hbkd.2018yx02011
Abstract:With the gradual opening of the low-altitude airspace and the rapid development of Unmanned Aerial Vehicle(UAV) industry, the users of UAV are increasing continuously and the conflicts could occur at any time. It is necessary to develop a reliable UAV conflict resolution algorithm to avoid the danger. This paper proposes an UAV conflict resolution algorithm based on the improved ant colony algorithm with two advantages. Firstly, the algorithm adopts adaptive parameters adjustment strategy, which adjusts the parameters value dynamically according to the quality of the solution, prevents the algorithm premature convergence and improves the accuracy. In addition, the disturbance factors is introduced to the state transition rules of random selected path in order to accelerate the initial convergence. The simulation results have shown that the improved algorithm displays obvious superiority in convergence precision, helping the two UAVs avoiding dangers in time. The algorithm described in this paper could be applied to target identification, path planning and other issues as a general optimized algorithm, which is of great significance and wide application.
2018, 39(2):176-182. DOI: 10.7535/hbkd.2018yx02012
Abstract:Ecological risk assessment of pollutants has been a focus of attention at home and abroad in recent years. Domestic and foreign scholars have put forward various methods and models for ecological risk assessment. The purpose is to evaluate the ecological risk of pollutants in environmental media by establishing different indicators, hoping to predict their adverse ecological impacts, as well as assess the potential for ecological changes caused by a certain factor in the past. This paper reviews the development of ecological risk assessment, summarizes the ecological risk assessment models and methods about pollutants in water, sediment and soil, summarizes the Risk Quotient (RQ), AQUATOX model, Species Sensitivity Distribution (SSD), Index of Geoaccumulation (Igeo), Hakanson potential ecological risk index to determine the level of ecological risk. According to the types and concentrations of pollutants in different environmental media, the appropriate method should be selected for ecological risk assessment. In the future, more research should be conducted on the ecological risk assessment method for the coexistence of multiple pollutants under different environmental media, riching ecological risk assessment method system, and providing a more appropriate assessment method for the ecological risk of various pollutants.
2018, 39(2):183-190. DOI: 10.7535/hbkd.2018yx02013
Abstract:In order to study the optimal operating condition of the sewage treatment material PVFM(polyvinyl formal), the mechanical blowing method and the chemical foaming method are adopted. Single-factor experiments and orthogonal experiments are conducted to study the factors including the amount of raw materials, reaction time and reaction temperature influencing the preparation of the material PVFM. The material is characterized by SEM. The properties of the material are explored through the contrastive experiments of sewage treatment. The results show that when PVA mass concentration is 9% (50 mL), cellulose content is 0.4 g, sulfuric acid content is 6 mL, formaldehyde content is 6 mL, SDS content is 0.4 g, carbonate calcium content is 0.8 g, reaction temperature is 30 ℃, the dripping time of sulfuric acid is 9 minutes, the dripping time of formaldehyde is 4 minutes, and the curing time is 8 hours, the material has good physical and chemical property, and the results of the contrastive experiments of sewage treatment show that PVFM has good removal effects on both COD and NH4+-N in simulated sewage. The sewage treatment material PVFM with good properties can be obtained by the mechanical blowing method and the chemical foaming method.