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1998 Vol. 24, No. 6

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Implicit Schemes for Numerical Simulations of Hypersonic Nonequilibrium Flows
Wu Songping, Lu Ye, Zheng Bo
1998, 24(6): 625-628.
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Two forms of implicit TVD schemes are proposed in this paper for the simulation of nonequilibrium flows past hypersonic re-entry vehicle, which are derived from the diagonal form of an approximate-factorization algorithm and lower-upper scheme applied to the implicit part of Harten-Yee's TVD scheme respectively. Numerical tests are taken for the two-dimensional and three-dimensional chemically nonequilibrium flows, and the results demonstrate that the algorithms in the paper are both efficient with high-resolution and less cost in computation.
Implicit Flux-Vector-Splitting Solution of Three Dimensional Parabolic Navier-Stokes Equations
Liu Yu, Zhang Zhenpeng
1998, 24(6): 629-632.
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By the use of implicit flux-vector-splitting method, three-dimensional dimensionless conservative parabolic navier-stokes equation is solved in general curved coordinates system. The code developed can be used to solve the three-dimensional flow field with comparatively complex boundary such as the flow field that subsonic, transonic and supersonic flows appear in it, the flow field that internal and external flows exist together and their mixing wake flow with multi-blocks. An axisymmetric sub-tran-supersonic internal flow field solution of a nozzle is given here including computational grid, flow vector profile, pressure, temperature and Mach number contour line distribution. An inner and outer flow field solution of a nozzle and its mixing wake flow is also presented inside being compose of computational grid, flow vector profile, dimensionless pressure, density and temperature contour line distribution.
Analytical Solutions of Linearly Elastic Impact of Beams
Xing Yufeng
1998, 24(6): 633-637.
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According to the elastic impact problems of structures are considered as initial value problems of the integrated impact structural systems,and the analytical solutions of a particle and a rod impacting laterally with a simply-supported beam are given. The dynamical responses of the above-mentioned two impact problems are investigated by numerical analysis. The convergence of the impact loads is analyzed in detail. And the effects of elastic contact deflections on convergence and impact responses are discussed,in which the elastic contact deflection is considered to be a spring.
Nonlinear Behavior of Separated Shear Layer of a Blunt Circular Cylinder
Dong Yufei
1998, 24(6): 638-641.
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Dynamical evolution process of separated shear layer of a blunt circular cylinder,and nonlinear interaction between separated shear layer and acoustic forcing have been experimentally investigated. The researches demonstrate, in unexcited state, there exists the subharmonic phenomenon, which implies the evolution of separated shear layer is mainly through vortices merging process. From separation to reattachment, laminar separated shear layer will take 2 times vortices merging processes, and turbulence separated shear layer will experience 5 times vortices merging. From the point of view of nonlinear dynamical system, transition of separated shear layer from order to chaos is through Hopf bifurcation and periodical bifurcation. In addition, response of separated shear layer to acoustic forcing was discussed.
Grid Generation Technique of Complex Configurations and its Applications
Zhang Zhengke, Zhu Ziqiang, Zhuang Fenggan
1998, 24(6): 642-645.
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A multiblock structured grid generation system for complex practical aircraft is presented and applied in the grid generation of a twin-tail fighter. A vectorized polynomial of degree 3 is used to generate grid on the interface of adjacent blocks. The volume grid in each block is generated by solving elliptic partial differential equations with source terms corrected by 3-d Hilgenstock method to control the grid line angle (orthogonality) to boundaries and first-layer grid point spacings off boundaries to expected values. Euler equations are solved in the generated grid of the twin-tail fighter and the computed results of the aerodynamic coefficients of the complete aircraft, the wing surface pressure and the vortical flow field are reasonable.
Investigation into Tensile Mechanical Propertiesof PUR Foam Plastics
Lu Zixing, Kou Changhe, Li Huaixiang
1998, 24(6): 646-649.
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The tensile mechanical properties of PUR foam plastics as well as its strain rate effect and temperature effect were investigated by means of tensile experiments. The experimental results show that the strain rate effect of PUR foam plastics is not obvious, but its temperature effect is quite obvious under tensile loading. At the same time, the PUR foam plastics has some brittle features and its stress-strain curve is obviously nonlinear characteristics when it is deformed. In addition, the theoretical prediction of modulus and strength for PUR foam plastics were given, and the predicted results are basiclly in agreement with experimental ones.
Research on Optimal Pointing Maneuvers of Post Stall Aircraft
Zhang Shuguang, Sun Jinbiao
1998, 24(6): 650-653.
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A terminal condition is put forward based on nonlinear point-mass aircraft dynamics, under which the given movable target shall be pointed. A numerical procedure on optimization of minimum-time pointing maneuvers is then established, in which the conjugate gradient method is employed to search for the optimal solution, and a punishment function is defined to handle the constraints. Numerical results show that the procedure can help ascertain the "best" maneuvers for different tactic requirements. Also shown is that the capability of rapid deep post-stall entry plays an unusual role in target pointing and shooting in within-visual-range air combat, as well as the capability of swift flight path reorientation which mainly stresses on the maximum lift.
Effects of Stretching Conditions on Forming Quality of Mirror Skins
Wan Min, Zhou Xianbin, Li Xiaoxing, Wu Hui
1998, 24(6): 654-657.
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On the basis of full consideration of the slip band appearing and the shape fixability of forming parts,reasonable conditions in stretch forming of airplane mirror skins have been determined by means of analysis of the effects of stretching velocity, geometrical dimensions of blank, geometrical parameters of dies and lubrication methods on forming quality. The results show that improving the deformation uniformity of sheet materials, delaying the appearance of slip band, and increasing the material deformation degree of the forming region are the main measures of working out the optimum process parameters and improving the forming quality of mirror skins.
Quasi-Quantitative Study on Organizational Decisionand Organizational Structure
Fang Weiguo, Zhou Hong, Zheng Yun
1998, 24(6): 658-661.
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Directed towards the characteristics of uncertain environment the modern organization faces, a general mathematical model of organizational decision-making is established. The organizational structure and its value are investigated in the views of decision-making and information communication. Integrating qualitative and quantitative methods, the quantitative expression of the organizational structure value is derived. The influence of organizational structure on organizational decision-making is analyzed, while some conclusions meaningful to organizational structure design are obtained. The study shows that, in the environment of uncertainty, the more information sharing among decision units enables organization to make the better decision, and the network organization whose communication channels are flexible and open has advantage over the hierarchical organization whose communication channels are rigid and restricted.
Study on Information Sharing Mechanism of Organizational Decision Making
Fang Weiguo, Zhou Hong
1998, 24(6): 662-666.
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By feat of category theory, the impact mechanism of actualization consequences of decision alternatives shared among decision units on improving organizational decision-making was explored. The concept of information-sharing was presented. Then, organizational decision-making was formulated as a category comprised of organizational decision situations, and morphism between decision situations was defined to reflect the information-sharing conjunction. The relationship between decision situation and organizational decision solution set was established through functors. The study argues that information-sharing cause expansion of organizational decision solution set and enable organization to optimize its decision on an expanded solution set, thereby avoid or reduce the possibility of leaving out the better solution due to information imperfection.
Tentative Research for Chaotic Fatigue
Xiong Junjiang, Wu Zhe, Gao Zhentong
1998, 24(6): 667-670.
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The bifurcation and chaos theory of dynamic system is introduced to study the sudden change of fatigue behavior. A micro-model to describe the fatigue damage dynamic system is proposed on the basis of physical mechanics. The local saddle-node, Hopf bifurcations and global bifurcations of this fatigue system are analyzed and discussed. The numerical ranges of the parameters in the fatigue damage dynamic system are presented while Hopf bifurcations occuring by means of the normal form theory and Hopf theorem, and the threshold value of the chaotic fatigue system is given by calculating Melinkov function of the perturbed system according to the unperturbed homoclinic orbits.
Numerical Simulation of Chemical Reacting Flow in H2/O2 Rocket Engine Thrust Chamber
Cai Guobiao, Zhang Huazhao, Zhuang Fenggan
1998, 24(6): 671-675.
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The viscous chemical reacting flow in the hydrogen-oxygen rocket engine chamber and nozzle is simulated by using loosely coupled point-implicit MacCormack scheme. In the numerical simulation the combustion process is modeled by using a 6-specis, 8-step finite-rate chemical reaction model, and the Baldwin-Lomax algebraic turbulent model is adopted. The distributions of flow parameters in the chamber and nozzle are presented. Analysis of the results show that the numerical simulation results are the same as the distributions of flow parameters in the hydrogen-oxygen rocket engine chamber and nozzle, so the result is proved to be reliable. The work of this paper lays a foundation for the numerical simulation of two-phase chemical reacting flow.
Method of State Observer Design and Fault Detection
Wen Xin, Wang Qing, Qian Fang, Zhang Hongyue
1998, 24(6): 676-679.
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Radial Gaussian function networks based fuzzy systems with adaptive capability,are applied to the state estimation and fault detection of nonlinear time-varying systems .In order to extract fuzzy IF-THEN rules from input and output sample data through learning,the Gaussian function is employed to represent the membership functions of the premise part of fuzzy rules ,and then a hierarchically structural self-organizing learning method is given.Based on this method of state estimation and fault detect for nonliear systems is proposed .The structure and characteristics of the observer are discussed. The results of simulation show that the proposed nonliear state observer can observe real system state and detect system fault satisfactorily.
Theoretical Model for Dissipation-Rate Budgets in Near-WallRegion of a Turbulent Boundary Layer
Lu Lipeng, Chen Maozhang
1998, 24(6): 680-683.
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Based on the linear hydrodynamic stability theory, a 3-D theoretical model is proposed for the turbulent fluctuations in near-wall region of a turbulent boundary layer. In accordance with the theoretical model, budgets of the the dissipation-rate of turbulent kinetic energy are calculated and its production rate, dissipation and transport are evaluated. Good agreements between the theoretical results and those of DNS are obtained.Especially in the region of y<10 ,the theoretical model is obviously superior to some coventional ones in predicting ability. It is not only beneficial to understanding the physics of turbulence but also, probably, opening a new way for developing turbulence modeling.
Decentralized Fuzzy Variable-Structure Control for Manipulators
Wang Qing, Wen Xin, Zhang Minglian
1998, 24(6): 684-687.
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A decentralized fuzzy variable-structure control is presented for trajectory tracking of robot manipulators. Considering the overall system as a set of linear subsystems with nonlinear uncertainties and interconnections, the tracking problem is tackled by decentralized control method. The proposed control approach enables the system states to track desired trajectories with high precision. Moreover, by using fuzzy control concept in variable-structure system, the chattering problem which exists in most variable-structure systems is subdued, and the system robustness to unmodelled uncertainties and external disturbances is improved. The approach is simple for real-time implementation. Simulation results are presented to validate the conclusions.
Prediction of Simulant Formability by Computer
Wang Lidong, Hu Shiguang
1998, 24(6): 688-691.
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The relationship between the fundamental formability (tension, plane-strain, etc) and the simulant formability (deep-drawing, cupping, hole-expansion, fuki's cup) was studied by means of artificial neural network. Based on a lot of experimental data and the back-propagation algorithm, a B-P neural network model on the relationship was established. The variables of simulant formability of the sheet metal with known parameters of fundamental formability were predicted by computer. The predicted results are in good agreement with the experimental results. It is shown that artificial neural network is effective to study the simulant formability of the sheet metal.
Research on the Characteristic of Optimal FlightRoute in the Terminal Area
Xue Lilin, Wang Weihong, Gao Jinyuan
1998, 24(6): 692-694.
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A method named multi-times optimization is presented to solve the multi-specification optimization problem,which is difficult to solve using the variational optimal theory.In the method several demands are reduced to some sub-tasks.In every subtask a demand that can not be transformed into bound condition is taken as performance specification for optimazation,and the other demands are taken as bound conditions.By means of the method,the arrival time,number of turn,turn angle of the aircraft in the terminal area are selected as performance specification separately,and the general character of optimal flight route in the terminal area is given.
All Digital DSP Based Closed-Loop Fiber Optic Gyroscope
Zhang Chunxi, Song Ningfang, Du Xinzheng, Zhang Weixu
1998, 24(6): 695-698.
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An all digital closed-loop fiber optic gyroscope (FOG) using digital signal processor (DSP) technique is presented.A multifunction integrated optic circuit (MIOC) is used, with square wave for biasing modulation and digital phase ramp for feed back. The design of signal detector,digital demodulator,preamplifier and digital filter is discussed, and theoretical analysis and experimental test on the performance and parameters of the closed-loop fiber optic gyroscope are performed.A trade-off between the system precision and response time using DSP is also discussed. Test results show that the bias of FOG is less than 0.3°/h, and the scale factor nonlinearity of FOG is less than 100×106.
Virtual Enterprise and Information Sharing Management in Virtual Enterprise
Yan Kaitao, Deng Jiati
1998, 24(6): 699-703.
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The concept and characteristics of virtual enterprise are discussed and an integrated framework is proposed as well. The emphasis is on the analysis of requirement and the presentation of a general approach for information sharing management in virtual enterprise. This approach consists of sharing management coordinator and application management coordinator which provides a method for communication among CAx systems that use the STEP (Standard for the Exchange of Product Data) product model as global conceptual view of data. Since the dynamic modeling and binding techniques are used for description and operation, this approach has flexibility and can manage information transmission and treatment efficiently.
Analysis of Axial-Flow Compressors Stall in Uniform and Distorted Inlet Flow
Zhang Mingchuan, Zhang Jin, Tang Diyi
1998, 24(6): 704-706.
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Using a row-to-row two-dimension nonlinear model,rotating stall parameters in a single rotor compressor are simulated, and compared well with the experimental data. The effects of inlet circumferential static distortion on the rotating stall in an one-stage compressor are investigated. Results show that there are no dramatic differences in stall parameters, whether the inlet flow is uniform or distorted. However, due to the interactions of inlet distortion, when stall occurs, the compressor displays not only a circumferential disturbance mode (stall wave), but also an axial disturbance mode (surge wave). Their coupling is an important factor for compressors' instability.
Singularly Perturbed Midcoursr Guidance Law for Quickly Ascending Air-to-Ground Missiles
Fu Li, Fan Yaozu
1998, 24(6): 707-710.
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Based on optimal control theory and singularly perturbed theory,a singularly perturbed midcourse guidance law that guarantees air-to-ground missiles to ascent quickly is proposed.This new guidance law is a composite control law consisting of three parts:optimal climbing control using variable weighting factor method,minimum energy cruising phase control and minimum energy switching phase control.Moreover,a new control logic is designed in order to remove influence of climbing control on switching phase.Simulation results of a certain type of air-to-ground missile are presents.It is shown that,with simple control algorithm and feasible onboard implementation,this law not only guarantees air-to-ground missiles to ascent quickly,but also satisfies the requirements of midcourse phases.The studies have important theoretical meaning and great value of engineering application.
Study on Transient of Automata System for Liquid Rocket Engine
Zhang Lihui, Zhang Zhenpeng, В.Н.Гладкова
1998, 24(6): 711-713.
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A physical model of the automatic control system of a pump-fed Liquid Rocket Engine (LRE) is constructed, for which a nonlinear mathematical model is built. Considering the interfering modalities probably happening and input with step form, the dynamic characteristic in each interfering status is simulated by using the small deviation calculating method. Comparison between the computed results and the test data shows that: when the interfering signals are varied within small bound, the mathematical model is relatively accurate and the calculating method can meet the simulating requirement. This work has signifcance for optimizing control parameters and reasonably adopting control system.
Approach to Dependability Modelling for Effectiveness Analysis of Ground Vehicle System
Wang Wuhong, Yang Weimin
1998, 24(6): 714-717.
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The dependability analysis of every mission period within every mission profile for repairable system is essential for the quantitative evaluation of system effectiveness and for designing effective system. In this paper, the mission succession probability is chosen as measurement of dependability while both Mission Mileage Between Critical Failure(MMBCF) and Mission Time To Restore Function(MTTRF) are constant. On the basis of various repairable situations, the dependability matrix for effectiveness analysis is established with analytical solutions of mission reliability and mission maintainability. Finally, the establishment of dependability matrix for effective analysis of ground vehicle is given as an engineering application example.The results give helpful and practicable basis for effective analysis of complex engineering systems such as flying vehicles,ground vehicles,automobiles.etc.
ENO Finite Volume Method For Unstructured Triangular Mesh
Song Songhe, Chen Maozhang
1998, 24(6): 718-721.
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A third order ENO finite volume method for hyperbolic conservation laws on unstructured triangular mesh is introduced.In order to obtain the third order accuracy on spatial discretization,a weighted quadratic interpolation is constructed on every triangular mesh.Two point Gauss quadrature formula is also used on each edge of every triangular mesh and the third order TVD Runge-Kutta method is used for time discretization.The numerical order of convergence and the numerical result of a mesh 3 wind tunnel with one step are given.The numerical results show that the numerical order of new method approachs to 3.
New Modified Adaptive Extended Kalman Filterof DR System for Land Vehicle Navigation
Fang Jiancheng, Shen Gongxun, Wan Dejun
1998, 24(6): 722-725.
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A new observation equation of the dead reckoning (DR) system for land vehicle navigation is presented, and a modified adaptive extended Kalman filter and its filtering algorithm for the DR system are proposed. By consideration of Markov process component in the random drift of rate gyros, and application of a current statistical model and adaptive algorithm for estimating maneuvering vehicles, the accuracy of the DR system model is greatly improved.Furthermore, in order to enhance the robustness and dynamatic performance of the extended kalman filter, a new adaptive filtering algorithm is researched.Computer simulation results show that the positioning accuracy and possiblility of the DR system can be greatly improved by this filter and adaptive algorithm.
Basic Operations in the Language Processing
Guo Honglei, Li Wei
1998, 24(6): 726-729.
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The basic operations in the language processing are classified from viewpoint of the entity and the attribute respectively, and two sets of basic operations , i.e., Attribute-derived operation set and Entity alternation operation set, are defined systematically . The attribute-derived operation set consists of Single-Phase operation, Aggregate operation, Disaggregate operation and Split operation.The entity alternation operation set includes Create operation and Fill operation. These operations are the basis of designing the architecture of the language processing model and the language processing function component. They are also beneficial for building a more economic knowledge processing scheme and universal information description mechanism.
Study on the Hydromechanical Behavior of Rubber Particles in Vibrated Fluidized Bed
Wang Xiaoxin Yuan Xiugan
1998, 24(6): 730-733.
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For the sake of investigating hydromechanical behavior of particles in vibrated fluidized bed, this paper studies the effects of vibration intensity, height of bed and gas velocity on pressure drop through a model vibrated fluidized bed equipment with rubber particles as sample materials. The variations of minimum fluidization velocity along with height of bed and vibration intensity are also analyzed. A helpful conclusion is obtained by comparing experimental results of rubber particles to those of nylon-1010. The research work of hydromechanical behavior of rubber particles in vibrated fluidized bed can present reasonable advice on cryogenic heat transfer between low temperature gas flow and rubber particles in cryogenic comminution.
Effects of the Microstructure of γ-TiAl Alloys on the Creep Behavior
Lin Jianguo, Zhang Yonggang, Chen Changqi
1998, 24(6): 734-737.
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The relationship between microstructure and creep behavior of γ-TiAl alloys was analyzed and discussed, and the effect of the orientation of lamellar boundaries with respect to loading axis on the creep behavior of TiAl alloy with fully lamellar structure was studied by using TiAl PST crystals. It is indicated that the primary microstructure parameters which have important influences on the creep behavior are lamellar orientations with respect to loading axis, volume faction of γ grains, lamellar grain size, lamellar width and grain boundary morphology. The way to get high creep resistance by microstructure control has been suggested.
Applying DSG Method to Part Model Decomposition
Yu Yong, Tang Rongxi
1998, 24(6): 738-741.
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Part machining can be imagined as a modeling procedure within which only a series of Boolean subtracting between father body and child body happen. To obtain such a series of subtracting body, Destructive Solid Geometry(DSG) theory is applied to orderly decompose the part design model into corresponding manufacturing model. Facing the prevalent featured-part of rotational model and that of prismatic model, two key algorithms based on the feature tree description that records the procedure of feature modeling are presented: width-first searching & depth-first searching,respectively implementing manufacturing planning of feature machining in the space span & time span. Finally, an expatiatory example goes further into the relative concepts and algorithm thread.
D-K Iteration Algorithm Based on Graphical User Interface
He Yufen, Xiong Zhang, Liu Xudong
1998, 24(6): 742-746.
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Based on the μ synthesis of the pitch axis controller of a fighter, the standard D-K iteration algorithm is presented. The command-line driven D-K iteration algorithm is not manipulated easily by control designers due to the complexity of the algorithm. In order to keep the algorithm well informed and popularized among control designers,a D-K iteration algorithm based on graphical user interface is introduced, which includes the D-K iteration algorithm in a menu oriented interface and has the feature of graphical objects.
Study of Fatigue Strength Condition for Non-Symmetrical Circulation
Yun Chao, Zong Guanghua, Jin Shuda
1998, 24(6): 747-749.
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The fatigue strength condition of component parts under non-symmetrical circulation is analysed for the tranditional design of mechanism in order to infer an expression about the fatigue strength condition. In terms of material mechanics, the working safe coefficient of components under the same circle feature is found by two points on the same projecting line in the endurance limit figure. Because the combined influence coefficient of components has only an effect on the stain amplitude (the vertical coordinate),the endurance limits of materials and components can't be located on the same projecting line. In view of this,the tranditional fatigue strength condition under non-symmetrical circulation is incorrect. Through the analysis of the figure of the endurance limit of components, a correct expression about the working safe coefficient of components is obtained.And further, the error between the expressions of two strength conditions is analysed. The conclusion shows that the design according to the original fatigue strength condition would cause greater losses.

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