2004 Vol. 19, No. 1

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Heteroscedasticity Regression Analysis for Censored Data
HUANG Wei, FU Hui-min
2004, 19(1): 1-6.
Abstract PDF(1208KB) icon1849 icon470
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A heteroscedasticity regression analysis method for censored data is presented,and it extends the traditional regression analysis,which is only suitable to complete and homoscedasticity data,to censored and heteroscedastic data.The heteroscedasticity regression equation is established and the best linear unbiased estimators for the regression parameters,the standard deviation and their covariance are also given.The linear heteroscedasticity regression analysis methods for normal distribution,extreme distribution and Weibull distribution are discussed in detail and the confidence limits of the regression curve and percentiles are given.At present,heteroscedastic data can only be analyzed by group test method that requires large sample.Compared with traditional method,the present method can reach higher precision and a great number of specimens can be saved.
Application of Similar System Reliability Information to Complex System Bayesian Reliability Evaluation
LIU Qi, FENG Jing, ZHOU Jing-lun
2004, 19(1): 7-11.
Abstract PDF(351KB) icon1440 icon451
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How to acquire proper prior distribution is a key problem in complex system Bayesian reliability evaluation.In this paper,the application of similar system reliability information to system reliability evaluation is studied.By weighting factor,similar system's information was converted to the prior information of a new system.The reliability test data based on Weibull and exponential distribution model is analysied,and reliability evaluation formula is presented.Finally an example is given to show this method is simple in computation and usable in application.
Application of The Time-Hardening Creep Law Coupling Damage
SHI Duo-qi, YANG Xiao-guang
2004, 19(1): 12-16.
Abstract PDF(681KB) icon2222 icon424
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Considering the isotropic damage,the principal of strain-equivalence was utilized to constitute the multi-axial creep equations together with the time-hardening creep law.The method of determining material parameters was developed through uni-axial creep test data.Numerical simulations were conducted by implementing them into ABAQUS using a user subroutine UMAT through a self-adaptive forward Euler integrate algorithm.Analysis was carried out for the evolution of creep damage and the influences of temperature and load.
Life Predication of Thermomechanical Fatigue in DS Superalloy DZ125
ZHANG Guo-dong, LIU Shao-lun, HE Yu-huai, ZHOU Bo-zhuo
2004, 19(1): 17-22.
Abstract PDF(342KB) icon1793 icon478
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Manson-Coffin equation,Ostergren method and microcrack propagation model were chosen to predict TMF life in DS Superalloy DZ125.The results of TMF life prediction showed that all of methods chosen were able to give a reasonable life prediction result for DS superalloy DZ125.For in-phase TMF,in-phase with hold time TMF and -135° phase angle TMF,Ostergren model gave a better life prediction result than Manson-Coffin equation and microcrack propagation model did. But for out-of-phase TMF,microcrack propagation model gave better results than Ostergren model and Manson-Coffin equation did.
Expert Systems of Engine Wear Fault Diagnosis Based on Knowledge Rule
CHEN Guo, ZUO Hong-fu
2004, 19(1): 23-29.
Abstract PDF(877KB) icon1519 icon480
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The paper is aimed at engine wear fault diagnosis of certain military aircraft during ground testing.Two common oil analysis methods,namely Ferrography analysis and Spectrometric analysis,as well as engine testing monitoring method,are applied to diagnosing the military engine wear faults using Expert System (ES) method.Firstly,according to expert diagnosis experience,the knowledge rules based on IF-THEN format of each method are obtained.Secondly,by wear criterion values of each method,the original symptoms are transformed into character expressions.Finally,the diagnosis results are achieved through forward chaining method.
Analysis of Radial Dynamic Characteristics of Magnetic Bearing System by Excitation Test
XIE Zhen-yu, XU Long-xiang, LI Ying, QIU Da-mou, YU Lie
2004, 19(1): 30-37.
Abstract PDF(1464KB) icon2110 icon483
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Dynamic characteristics of turbine magnetic bearing system by excitation test are studied in this paper.The method can be useful for prediction of critical speeds,stiffness and damping of the system,before it goes into operation.On the other hand,excitation test shows that adjustment of control parameters has less influence on some critical speeds.
Dynamic Behavior of a Rotor Magnetic Bearing (RMB) System with the Fault of Rub Between Rotor and Stator
LIU Zhan-sheng, LU Jian, LU Wei-jian, CHI Ding-nan
2004, 19(1): 38-45.
Abstract PDF(405KB) icon1836 icon477
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Rub between rotor and stator is a malfunction in rotor bearing system,and this type of fault can also occur in RMB.A mathematic model of RMB considering the eccentricity of the rotor is established,and the vibrations are analyzed by using bifurcation map,Poincare map and spectrum analysis.The numerical simulation shows that a periodic bifurcation appears in the rotor vibration and the RMB system will become unstable with the increase of the speed and eccentricity.In the spectrum,the order frequencies move from the right to the left near the point of odd multiple frequencies.The study results can be used to control the instability of the RMB system with rub between rotor and stator.And the vibration character of rub can be used to diagnose the fault of rub between rotor and stator of a RMB system.
Strength Analysis of Master Connecting Rod for Stern Motor Radial Engine
ZHANG Hong, GUO Hai-ding
2004, 19(1): 46-49.
Abstract PDF(335KB) icon1797 icon474
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This paper focuses on the fatigue failure problem of the master connecting rod of a stern motor radial aero-engine with nine cylinders.Kinematics and dynamics analyses are combined to obtain the maximum moment on the rod during working cycle.As surface loads on the rod are transferred through motion pairs,the contact element in ANSYS is used to simulate the contact situation between the master connecting rod and crank pin or piston pin.A finite element analysis is conducted for the rod.The results of the finite element analysis show that the fatigue strength reserve of the rod is not sufficient.The coincidence of danger position and failure position gives a good reference for the analysis of rod fatigue failure.
The Bonding Strength and Failure Modes of Thermal Barrier Coatings
GENG Rui, ZHOU Bai-zhuo, QI Hong-yu, YANG Xiao-guang
2004, 19(1): 50-53.
Abstract PDF(237KB) icon1603 icon512
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The bonding strength of the thermal barrier coating including ASP and EB-PVD is studied under different high temperature experiments.The effects of different temperatures,thicknesses of coating and substrate are analyzed.Using the two-direction testing,the normal and tangent bonding strengths under high temperature oxidation are investigated.Tests show that the bonding strength of the same TBCs with different thicknesses is very close.The experiments provided many data and reference for failure modelling and aero-engine parts designing with TBC.
Nonlinear Dynamics of Spiral Bevel Gears and Hypoid Gear Drives
YANG Hong-bin, GAO Jian-ping, DENG Xiao-zhong, ZHOU Yan-wei
2004, 19(1): 54-57.
Abstract PDF(629KB) icon1743 icon496
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By introducing the concept of ideal transmission,the expressing way of meshing force and meshing damping is given,which is a foundation to establish complex dynamic equations of spiral bevel gears and hypoid gear drives.Meanwhile,the torque produced by meshing force and meshing damping is given,which is various in different meshing regions under multiple-teeth meshing.The non-linear dynamic equations of spiral bevel gears and hypoid gear drives are established,which include the input and output rotating inertia,transmission error and time-varying mesh stiffness as well as backlash.The frequency response curves,phase portraits,time histories and dynamic load factor can be obtained by calculating the dynamic equations.
Establishment of a Certain Aero-Engine Starting Mathematical Model in Plateau Regions
WU Li-rong, LI Jian, XIE Shou-sheng, LI Ying-hong
2004, 19(1): 58-60.
Abstract PDF(563KB) icon1667 icon448
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The starting of a certain aero-engine in plateau regions has been very dangerous and complex.In order to establish its mathematical model,this paper presents an improved variable memory length algorithm based on wavelet transform multi-resolution analysis method.This method decomposes data into different frequency segments,in which different memory lengths are used to identify parameters.The starting model can thus be thus formulated,which provides theoretical reference for starting test in plateau regions.
A Study of Turbofan Component Characteristics Based on Back-Propagation Network
CHEN Ce, LI Jun
2004, 19(1): 61-64.
Abstract PDF(663KB) icon1609 icon427
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In jet engine characteristic computing,Back-Propagation network model was established to study and identify the data of engine component characteristics.Consequently,accurate interpolation of characteristic data and speculation on the unknown characteristic data were achieved.The checkout and analysis of network's output results showed that the present model has better practicability and veracity.
An Experimental Investigation of Combining Stealth Device in Air Duct with Turbofan Engine
LI Wen-feng, CHENG Bang-qin, WANG Yong-sheng
2004, 19(1): 65-68.
Abstract PDF(248KB) icon1688 icon472
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The paper introduces the experimental facilities for combining stealth device in air duct with turbofan engine.How the flow deflector affects the flow field of air duct was ascertained.The fan-shaped flow deflector was made of wave absorption material,its stealth principle is analyzed.The distributing of complicated inlet flow field and the analyses of distortion index are investigated.
The Effects of Reynolds Number on the Stability of Axial compressors
WANG Ying-feng, HU Jun
2004, 19(1): 69-73.
Abstract PDF(176KB) icon1912 icon555
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In this paper,the stability of a multi-stage compressor in an extensive range of Reynolds number is estimated by using the method of estimating the maximum pressure rise potential.The results prove that the stability of compressors deteriorates with the decline of Reynolds number.The method used in this paper can analyse the pressure-rise potential and stability of each stage and the whole compressor as well in an extensive range of Reynolds number.It is envisaged to provide helpful information on the designing of the axial compressors working at low Reynolds number.
Comparision of Inlet Performance with the underfuselage Inlet and Fuselage Side Inlets
ZHANG Zhao-ming, LI Zhi-qiang, DING Ke-wen
2004, 19(1): 74-80.
Abstract PDF(417KB) icon1545 icon500
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This thesis compares the influence of the angles of attack (α) and yaw (β) on the inlet performance with the underfuselage inlet and the fuselage side inlets by means of low and high speed wind tunnel tests.The results show that in supersonic flow the aerodynamic performance of the underfuselage inlet becomes better when the angle of attack changes from 0 to 5°,but that of the fuselage side inlets remains almost unchanging.In subsonic flow when the angle of attack changes from 6° to 12° (high subsonic) or 30° (low speed),the performance of the fuselage side inlets becomes worse obviously,but that of the underfuselage inlet almost does not change with the angle of attack and can be kept the same as α=0°.In high and low speed free stream flow,the performance of two kinds of inlets almost does not change with β.
Effects of Reynolds Number in a Small Multistage Axial Flow Compressor
WEN Quan, LIANG De-wang, LI Feng-chun, CHEN Guo-zhi, TU Meng-pi
2004, 19(1): 81-88.
Abstract PDF(209KB) icon1791 icon523
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The effect of Reynolds number in small multistage axial flow compressors is described and illustrated by experimental data and numerical simulation for a four-stage axial flow compressor,of which total pressure ratio is 60 and polytropy efficiency is 084 at design points.The performance of this compressor is obtained at 100 percent of the rotational speed.The influence of variations in flow Reynolds number has been studied through experimental data at 85 percent of the rotational speed.Using a three-dimension calculation code,the detailed flow-field of this compressor at different Reynolds Numbers has been obtained.The results show that the thickness of boundary layer increases with decreasing Reynolds number,mean while the flow-field structure is changed,and the performance of this compressor will be worse.Combined with experimental data and numerical simulation,the performance of this compressor has been modified using a correlation.Considering the effect of Reynolds number,the performance of this compressor will be that the total pressure ratio is 622 and polytropy efficiency is 085 at design rotational speed.
Flow Analysis of a Single-Stage Axial Flow Compressor with Splitter Rotor
ZHANG Yong-xin, ZHOU Zheng-ping, YAN Ming, CHEN Mao-zhang
2004, 19(1): 89-93.
Abstract PDF(729KB) icon1541 icon465
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To investigate flow in a single-stage axial flow compressor with splitter rotor,numerical simulations were carried out by using a 3-D CFD code.The results show strong unsteady flow phenomena in the rotor passage,although the isentropic efficiency shows small change with respect to time.The analysis shows that differences of mass flow and pressure rise between the two splitter-splitted passages have significant influence on unsteady flow in the compressor stage.The presence of splitter reconstructs the balance of pressure in rotor passage,and controls the flow near rotor blade.
Effects of Geometry Parameters on Incidence Characteristics of Turbine Low Pressure Guide Vane
AN Bai-tao, HAN Wan-jin, WANG Song-tao, WANG Zhong-qi
2004, 19(1): 94-100.
Abstract PDF(390KB) icon1895 icon482
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Experimental measurements were performed in a low speed wind tunnel for both original and modified turbine LGV's which are used in turbofan engines under different operating conditions.Compared with the original design,the modified design changed many geometry parameters,including adopted optimizing meridional endwall profile,positively curved blade,aft-loading airfoil and negative incidence angle at the leading edge,so the incidence characteristics of these two designs differ significantly.The two LGV's were measured at three operating conditions,i.e.positive incidence,design and negative incidence operating conditions.Results show that the modified design not only has smaller energy loss,but also has better incidence angle adjustability,which means that with the change of operating conditions total pressure loss alters smaller in the range of three operating conditions.Exit loss of the original design is sensitive to the incidence angle and varies greatly.
Comparison of Turbine Low Pressure Guide Vane before and After Optimization
AN Bai-tao, HAN Wan-jin, WANG Song-tao, WANG Zhong-qi
2004, 19(1): 101-107.
Abstract PDF(413KB) icon1573 icon500
Abstract:
Detailed flow field measurements were conducted in a low speed wind tunnel for both original and modified LGV's which are used in turbofan engines.Optimizing approaches are introduced for the modified design.Considering the geometry feature of the transit duct before the LGV inlet that it has a large meridional diffusing angle,equal velocity gradient profile is employed in the modified design in order to control the separate flow.Moreover,the modified design employs positively curved blade,rear-loaded airfoil and other approaches to reduce the increase in energy loss.The results shoTw that the aerodynamic performance of the modified design is improved significantly:the total pressure loss decreased by 147%;the exit flow angle along the blade height becomes more uniform than that of the original design.The methods which can reduce energy loss are reasonably conjugated.
Numerical Prediction of Multi-Stage Axial Flow Compressor off-Design Performances
LIU Qian-zhi
2004, 19(1): 108-112.
Abstract PDF(289KB) icon1625 icon496
Abstract:
The paper presents numerical predictions of design and off-design performance for multistage axial compressors.A time marching,implicit,finite-difference scheme was used to solve three-dimensional Reynolds-averaged Navier-Stokes equations.The shocks in transonic flow field are captured with a high resolution procedure.The turbulent viscosity is calculated using the two-layer Baldwin-Lomax algebraic turbulence model.Detailed computations were carried out for a five stage high-pressure compressor configuration for design and off-design conditions at 100%,90% and 80% corrected speeds.The mass flow rate convergences were obtained (smaller than 1%) at all these computations.The predicted results of stage and multistage performances at design operating point show a good agreement with the design.The surge margin at design operating point was estimated by the numerical results.The Maximum difference of stator blade inlet flow angles between design and off-design operating points is larger than 15 degrees at design speed.
Numerical Investigation of Total-Pressure Recovery Coefficient of Cascade in Unsteady Environment
YAN Zhao, JI Lu-cheng, YU Hai-li, XU Jian-zhong
2004, 19(1): 113-117.
Abstract PDF(678KB) icon1321 icon486
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A numerical method based on Ni and implicit dual-time steps scheme for solving the 2-D unsteady N-S equations is applied to investigating the influence of unsteadiness on the total-pressure recovery coefficient of turbine cascade,results of which are compared with that of the steady model and quasi-steady model introduced in this paper.Calculated results show that the unsteadiness of flow can increase the total-pressure recovery coefficient of cascade,when compared with quasi-steady flow.The unsteady flow tends to decrease the total-pressure recovery coefficient when compared with steady flow.
Experimental Investigation of Energy Loss in Straight and Bowed cascades with Aft-Loaded Profiles
ZHOU Xun, HAN Wan-jin, LU Zhi-qiang
2004, 19(1): 118-125.
Abstract PDF(451KB) icon1738 icon472
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The experimental investigation was conducted in a low speed annular wind tunnel.The energy loss evolution from the upstream to the downstream in the blade cascade channel with aft-loaded profiles was measured in detail.The results of the present study showed that energy loss occurs mainly in the places near the leading and the trailing edges.Therefore,the measures to be taken are to choose the leading edge diameter,to match the portion of adverse pressure gradient zone with its value and to improve the static pressure distribution along span height.
Numerical Study of Flows in the Curved-Blade Stage and Its Redesign for a Steam Turbine
YANG Ai-ling, YAO Zheng, WU Qi-lin, ZHONG Gang-yun
2004, 19(1): 126-130.
Abstract PDF(399KB) icon1813 icon488
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The numerical simulation of three dimensional flows in a steam turbine stage with four different curved stators is completed using commercially available CFD code NUMECA in this paper.The characteristics of the flow and the variation of the parameters are analyzed according to the numerical solvers.The efficiency of the stage with four different stators is presented.The results show that the curved stators used in this paper are not to improve the stage efficiency.Lastly,the influence of the curved blade on the horseshoe vortex appearing inside the stator is analyzed.
Application of Auto-Adaptive Cartesian Grid Approach to Numerical Simulation of Convection
SUN Ji-jing, TAO Zhi, XU Guo-qiang, DING Shui-ting
2004, 19(1): 131-136.
Abstract PDF(906KB) icon1637 icon488
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It is difficult to deal with complex geometric regions for numerical simulation of convections.The auto-adaptive Cartesian grid approach is able to tackle the problem easily.But,up to now,it is mainly applied to solving compressible outer flows of Euler equations and Navier-Stokes equations.This paper simulated two convection cases of incompressible inner flow.The two cases were also simulated by STAR-CD,a commercial CFD code.The simulation results by auto-adaptive Cartesian grid approach and STAR-CD were compared and consistencies were shown.So the auto-adaptive Cartesian grid approach is suitable to be applied to simulating convection problems.
Numerical Simulation of Rime Ice Accretion Process on Airfoil
ZHANG Da-lin, CHEN Wei-Jian
2004, 19(1): 137-141.
Abstract PDF(762KB) icon1854 icon495
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To simulate the ice accretion on airfoil,a boundary moving technique is proposed to deal with the distortion of airfoil surface due to ice accretion on the leading edge.Incorporating the two-phase model of air-supercooled droplets in the Eulerian coordinates,this technique was applied to simulating the process of the rime ice accretion (the droplets freeze at the instant impinging on the airfoil) on the NACA 0012 airfoil,and the ice profile after ice accretion was achieved successfully.And the brief comparison between the results of this paper and the experiments indicates that the current method is applicable and effective.
Combustor Dome Design with Three Swirlers for Widening the Operation Stability Range
YUAN Yi-xiang, LIN Yu-zhen, LIU Gao-en
2004, 19(1): 142-147.
Abstract PDF(799KB) icon1788 icon596
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Combustor dome design with three swirlers was experimentally investigated in order taken to widen the operation stability range.The effects of different fuel-air ratio in dome and different injectors were taken into account.Experiment results exhibited that the increasing of fuel air ratio in dome had a good effect on fuel-air ratio at lean blowout,and showed that the design was promising with low fuel air ratio at lean blowout and acceptable smoke number.But at any rate some measures would still be needed to improve the performance of smoke number of the design.
Numerical Investigation of Flow Fields in the Channel with Ejection through the Holes on the Wall
CAI Wei-jun, SONG Xiao-wei, LIU Song-ling, LIU Gao-wen
2004, 19(1): 148-152.
Abstract PDF(783KB) icon1530 icon455
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The commercial software (Fluent 6.0) has been used to simulate the flow behaviors in the cooling channel of turbine blade. Particular attention has been paid to the upstream and downstream regions of the holes.Important aspects of the study include:flow undergoes a strong acceleration and a subsequent rapid deceleration during passing hole.The presence of the holes will reduce mass flux of the channel and even cause a low speed region.The present results show good consistent with the experimental data,so the mature commercial software can be employed to study such complex physical phenomena.
Augmented LQR Method for Aeroengine Control Systems
YANG Gang, SUN Jian-guo, LI Qiu-hong
2004, 19(1): 153-158.
Abstract PDF(780KB) icon1821 icon534
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This paper introduces an augmented LQR method.This method uses the derivatives of the original system states and command tracking errors as augmented states.By virtue of this,the augmented LQR method results in a robust multivariable system which can eliminate steady state errors,keeping as good robustness as LQR.When all system states are not measurable,a reduced order state observer is introduced,which is designated as near optimal LQR method.The resulted control system has superior performance compared to LQG,and is able to meet the requirements for aeroengine control system.Finally,simulation results attests to the properties of these methods.
A Study of Propulsion Optimization Control Modes
YUAN Chun-fei, SUN Jian-guo, XIONG Zhi, LI Song-lin
2004, 19(1): 159-163.
Abstract PDF(741KB) icon1641 icon455
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Propulsion optimization control modes compute a set of trim commands to the Digital Electronic Engine Controller by Linear Programming,this approach results in significant performance improvements of aero-engine.Adaptive engine model is applied in order to accommodate the off-nominal effects and engine-to-engine variations.The structure of the optimization control system is designed and control algorithm is developed.Digital simulations are conducted with two optimization modes:maximum thrust mode and minimum fuel consumption mode.Simulation results presented here demonstrate that during accelerating flight at constant altitude thrust increases up to approximately 10 percent in the maximum thrust mode,and at subsonic cruise specific fuel consumption decreases up to 2 percent in the minimum fuel consumption mode.
Sensor Failure Diagnosis for Turbofan Engine Control System
XU Xiu-ling, GUO Ying-qing, WANG Yong-gen, GOU Lin-feng
2004, 19(1): 164-168.
Abstract PDF(702KB) icon1788 icon505
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According to Kalman filter and multiple-failure-hypothesis based testing,the sensor failures are detected,isolated and accommodated in turbofan engine control system.Principles and algorithms of sensor failure detection,isolation and accommodation are given.Sensor failure diagnosis process for some typical sensor failures is simulated.Simulation results illustrate that this method can immediately and effectively detect,isolate and accommodate sensor failures,no mistake and failure reports were found.

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