Table of Content

26 September 2014, Volume 35 Issue 9

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Paper

The Similarity Research on Underwater Explosion of Directional Warhead

RONG Ji-li， HE Xuan， XIANG Da-lin， BU Xiang-dong

2014, 35(9):  1329-1334.  doi:10.3969/j.issn.1000-1093.2014.09.001

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In order to solve the problem of high expense in the underwater explosion of directional warhead, the similarity is researched by dimensional analysis. The aim is to research the relationship of explosion pressure between original and small scale models. The result of dimensional analysis is verified by the simulation of AUTODYN. As a result, if the mass of TNT in the small scale model is β³ times of that in original model, the peak pressure in original model is as same as that in the small scale at β times distance. It indicates that the small scale model can replace the original model if the similarity rule is used. This research provide the theoretical basis for underwater explosion experiment which uses the small scale model. It has engineering significance to some extent.

Research on Acceleration Slip Regulation of 6×6 Electrically-driven Wheeled Vehicle

YAN Yong-bao, ZHANG Yu-nan, YAN Nan-ming

2014, 35(9):  1335-1343.  doi:10.3969/j.issn.1000-1093.2014.09.002

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A vehicle dynamic model is built for 6×6 electrically-driven skid-steering unmanned ground vehicle with consideration of nonlinear eighteen degree-of-freedom. Based on the accurate controllable characteristics of torque of motor driving wheel, acceleration slip regulation（ASR） control strategies of compound Fuzzy-PID with smooth-switch are developed in order to adjust the slip ratio of driven wheel. The robust dynamic property of the ASR system and its adaptability to uneven road are improved by fuzzy controller, and its stable performance and control precision are enhanced by incremental PID controller. The ASR control strategies are simulated under four different road conditions, i.e. low-u road, high-u-to-low-u joint road, low-u-to-high-u joint road, and u-split road. The simulation results indicate that the proposed ASR control strategies can fast, effectively and smoothly prohibit the driving wheel from transiently slipping.

Dynamic Modeling and Simulation of Gatling Gun with Muzzle Assistant-Rotating and Recoil Absorber

LI Jia-sheng， QIU Ming, LIAO Zhen-qiang, XIAN Dong-peng， SONG Jie

2014, 35(9):  1344-1349.  doi:10.3969/j.issn.1000-1093.2014.09.003

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A gas dynamic model of muzzle assistant-rotating and recoil absorber for internally powered gatling gun is established based on gas dynamic equations, and the assistant-rotating force and brake force of this device are calculated. The changes of assistant-rotating and brake forces with length are analyzed by changing the lougitudinal size of this device along the axial direction of barrel. The dynamics simulations of gatling guns without and with muzzle assistant-rotating and recoil absorber are performed based on the firing dynamic model of internally powered gatling gun. The results show that the properly expanded length of center chamber and nozzle in the axial direction of barrel can effectively increase the assistant-rotating force and brake force. The brake can be used to significantly increase the firing frequency of gatling gun.

Study of Penetration Ability and Aftereffect of MEFP with Scored Liner to Finite Thick Double-layer Steel Target

XIANG Sheng-hai, XU Wen-long, TANG En-ling, LI Ran, ZHANG Jian,

2014, 35(9):  1350-1355.  doi:10.3969/j.issn.1000-1093.2014.09.004

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The penetration ability and aftereffect of multiple explosively formed projectile (MEFP) with scored liner to a finite thick double-layer steel target are analyzed using ANSYS/LS-DYNA. The results show that the length-to-diameter ratio of charge has little effect on projectile shape, and the groove depth has a significant effect on projectile shape. If other conditions remain unchanged, the increase in thickness of liner leads to the reduction in axial speed of projectile, increasing the erosion amount of liner. Therefore the liner has an optimal thickness value in view of penetration depth; the aftereffect of shallow groove depth is better. The simulation results are consistent with the experimental results.

The Failure Mechanism and Experimental Study of MEMS Fuze TSV Package at High Transient Current

LIU Fang-yi， LOU Wen-zhong， DING Xu-ran， WANG Fu-fu， WANG Ying

2014, 35(9):  1356-1362.  doi:10.3969/j.issn.1000-1093.2014.09.005

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With the development in the miniaturization, intellectualization and dexterity of fuze, the 3D package is the most promising technology to realize fuze miniaturization. Through-silicon via (TSV), the key technology of 3D packages, has the advantages of small package size and low power consumption, and is widely used in microelectronic system integration. A TSV-based 3D package technology for MEMS fuze is presented. The work mode of MEMS fuze requires that the resistance change of TSV in the allowable range at a high transient current when the fuze is detonating. Temperature curve of TSV at a high transient current is calculated using the finite element analysis software. Three groups of TSVs are experimented: 40 V, 330 μF capacitor discharge; 10 V, 330 μF capacitor discharge; and 4 V, 100 μF capacitor discharge. The potential failure modes and transient current carrying capacity of TSV are obtained through the comparison of simulation and experimental results. The result shows that the TSV package can meet the normal working of the MEMS fuze in the conditions of 10 V, 330 μF capacitor discharge and 4 V, 100 μF capacitor discharge.

Single Channel Source Separation and Parameters Estimation of Multi-component PRBC-LFM Signal

ZHU Hang, ZHANG Shu-ning, ZHAO Hui-chang

2014, 35(9):  1363-1374.  doi:10.3969/j.issn.1000-1093.2014.09.006

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A method of single channel source separation and parameters estimation of multi-component PRBC-LFM signal is proposed. The repetition period of each component can be estimated through singular value decomposition. The influence of the pseudo code on parameter extraction is eliminated through a square calculation of signal, and the interference of noise on the component under separation is reduced by cycle accumulating. The modulation rate and the carrier frequency are estimated by using FRFT and searching the discrete points. The initial phase of multi-component signal is determined by calculating the inner product, and then the pseudo random sequence and the signal amplitude are estimated by using the character of that the pseudo random sequence is a real signal. In addition, the proposed method is used to estimate SNR of mixed signal by using eigenvalue decomposition, and SNR can be used to determine the threshold adaptively. In simulation, the method is demonstrated by separating a specific signal. The result shows that the proposed method is effective under the condition of different SNRs.

Application of Ferrite Material in Hot-wire EED for Improving Its Adaptability to Electromagnetic Environment

REN Wei, BAI Ying-wei, CHU En-yi, ZHANG Zhou-mei, LI Ming

2014, 35(9):  1375-1380.  doi:10.3969/j.issn.1000-1093.2014.09.007

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The electromagnetic induction and energy coupling effects of hot-wire electroexplosive device (EED) in electromagnetic environment have the effects on its safety and reliability. In order to effectively attenuate the effect of electromagnetic environment on EED, the ferrite beads are used in EED for continuous electromagnetic environmental hazard protection and adaptive design threough the effect tests and analysis. The test results show that electromagnetically induced current can be effectively attenuated by about 30%, and the use of ferrite beads can not affect the electric-heating performance of EED, which provides a method for the electromagnetic adaptabilitivity design of hot-wire EED.

Study of Nitration Process of Pyridine/Pyrazine Compound with Electron-donating Groups

LI Qin-hua, LU Ming, PAN Ren-ming, WANG Peng-cheng, ZHU Jie

2014, 35(9):  1381-1387.  doi:10.3969/j.issn.1000-1093.2014.09.008

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The nitration process of nitrogen-containing heterocyclic aromatics with electron-donating groups, taking 2,6-diaminopyridine and 2,6-dimethoxypyrazine as substrates, is studied. The effects of nitration systems on the yields of 2,6-diaminopyridine and 2,6-dimethoxypyrazine are investigated, respectively. The best nitration system that is suitable for those pyridine and pyrazine compounds which are difficult to be nitrated is determined. On the base of that, some important factors, such as the amount of nitric acid, reaction temperature, ratio of super acid, are further studied, and the optimized reaction conditions are obtained. Yields of 90% and 65% are reached for 2,6-diaminopyridine and 2,6-dimethoxypyrazine, respectively. Finally, the relationship between the difficulty of nitration and the activity of nitrogen-containing heterocyclic aromatics is analyzed through simulated quantum chemistry calculation in the view of electron cloud density and zero point energy. The results show that, with the increase in nitrogen atom number of aromatic, the electron cloud density of carbon atom displays a decreasing trend, the activity of nitrogen-containing heterocyclic aromatics weakens, and then the nitration reaction is restrained. However, as the introduction of electron-donating group, the electron cloud density of carbon atom increases, promoting the nitration reaction.

Research on Application of Energetic Triazole Ionic Salts in Solid Propellant

PEI Qing， ZHAO Feng-qi, GAO Hong-xu, XU Si-yu， HAO Hai-xia, YAO Er-gang, ZHOU Zhi-ming

2014, 35(9):  1388-1392.  doi:10.3969/j.issn.1000-1093.2014.09.009

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DSC thermal analysis method is employed to evaluate the compatibility of four kinds of energetic triazole ionic salts with some solid propellant main components. The effects of four energetic triazole ionic salts on the combustion properties of glycidyl azide polymer （GAP）propellant are investigated. The results indicate that four kinds of energetic triazole ionic salts have good compatibility with GAP, and nitrocellulose (NC), but they are sensitive with cyclotrimethylene trinitramine (RDX) and nitrocellulose/nitroglycerine (NC+NG) except 3,4,5-triamino-1,2,4-triazolium nitrate (2a). GAP propellant containing containing 1,2,4- triazolium nitrate (1a) has higher burining rate in the range of 12～16 MPa. GAP propellant containing 1,2,3-triazolium nitrate (1b) has higher burning rate in the range of 7～10 MPa. The burning rate pressure exponents for the propellants containing 3,4,5-triamino-1,2,4-triazolium nitrate (2a) and 3,4,5-triamino-1,2,4-triazolium dinitramide (2b) are decreased in the range of 10～16 MPa.

Study of Rotary Motion-blurred Image Restoration Algorithm

LUO Yuan-hong, XU Ting-fa， ZHU Zhen-fu

2014, 35(9):  1393-1399.  doi:10.3969/j.issn.1000-1093.2014.09.010

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The imaging sensor, which is set on a rotating plat, rotates with the plat at high speed. As a result, the images is be blurred badly. According to the space-variant of the rotary image, the rotary trails are extracted and the rotary length of each trail is gained. The two-dimensional image restoration is transformed into one-dimensional signal recovery. Two restoration methods are proposed. The first method is based on the Weiner filter, and the second methods is based on the diagonal loading arithmetic. Compared to the previous method, such as the minimum-square method and the logarithmic polar coordinates method, the two methods make better performances with little calculating time.

Matrix Log Cumulant-based Speckle Filtering Method for Polarimetric Synthetic Aperture Radar Data

LIU Kun, MA Wen-ping , LIU Hong-ying, WANG Shuang

2014, 35(9):  1400-1407.  doi:10.3969/j.issn.1000-1093.2014.09.011

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Speckle filtering is a crucial procedure in polarimetric synthetic aperture radar (PolSAR) data processing. MLC is introduced into PolSAR speckle filtering by calculating the filtering coefficient based on the matrix log-cumulant (MLC) and using the non-local method for the first time. In the proposed method, a homogeneous region is selected based on non-local method, then the data are filtered using the MLC-based filter coefficient. The determinant of the coherence matrix is used in the calculation in both two steps. It is more reasonable than using the SPAN data or the principal diagonal elements in the coherence matrix. The comparison experiments illustrate that the proposed method can smooth the homogeneous region effectively. Meanwhile, the structure, texture and detail information of PolSAR image are better retained. And the polarimetric signature of the data is also well maintained.

Damage Effect of Charged Coupled Device with Multiple-pulse Picosecond Laser

SHAO Jun-feng, LIU Yang, WANG Ting-feng, GUO Jin

2014, 35(9):  1408-1413.  doi:10.3969/j.issn.1000-1093.2014.09.012

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The action mechanism of high repetitive ultra-short laser interaction on electro-optic system has been drawn great attention recently. The experimental damage effect and mechanism of single and multiple-pulse picosecond lasers on Wat-902B interline charged coupled device (CCD) are reserched. The experimental setup mainly includes lasers, test subject, and camera. It maintains that the picosecond laser points at the optical entrance puil of camera all the time. The camera is installed on an electric revolving stage to control the time of intersection between a laser and the test subject. The second moment method is employed to obtain the laser diameters on CCD surface and its accuracy is better than 20.3%. The experimental results show that the functional damage threshold of multiple-pulse laser is about 13.6~121.0 mJ/cm², which is severely lower than that of 1.5 ns and 400 ps kilohertz-repetition-rate single-pulse lasers, approximating 263~1 146 mJ/cm². The damage mechanism of single-pulse laser is to lead to short circuit between CCD vertical transfer electrode lines, but the damage mechanism of multiple-pulse laser is obviously different from that of single pulse laser, which is to cause an accumulated damage effect.

Calibration of Shadowgraphy System and Analysis of Measuring Error

WANG Wei，TANG Zhi-hua，LUO Hong-e, CHEN Ping

2014, 35(9):  1414-1418.  doi:10.3969/j.issn.1000-1093.2014.09.013

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Based on the shadowgraphy system and the calibration of camera intrinsic and extrinsic parameters, the measuring errors associated by image recognition errors are studied, and an error model is built by using Taylor series expansion. Assuming that the image recognition errors are of independent identical distribution (IID), the mathematical expressions of the first moment and the second moment are presented for the measuring errors. Furthermore, the probabilistic properties of the measuring errors are studied according to the hypothesis that the distance between the cameras and the calibration surface are equal. The symbolic analysis and the numerical validation results show that each component of the measuring error is not independent; the recognition errors act as a factor to influence the measuring error; the first moment coefficient of measuring error changes linearly with the distance from object point to calibration surface, but there exists a nonlinear relationship between the auto-covariance coefficient of measuring error and the coordinate of the object point; and both the first moment coefficient and the auto-covariance coefficient are decreased if the object point is close to camera.

Design of Missile Guidance Law Subject to Acceleration Command Constraint

MENG Ke-zi， ZHOU Di

2014, 35(9):  1419-1427.  doi:10.3969/j.issn.1000-1093.2014.09.014

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Based on target-missile relative motion equation in plane, a two-dimensional guidance law subject to acceleration command constraint is designed using command filtered backstepping approach, and the second-order dynamics characteristics of missile autopilot is considered. The guidance system is divided into two sub-systems in the light of stability requirement of the main states. Then the command filtered backstepping approach is used to design the guidance laws for two sub-systems based on the principles of zeroing line-of-sight(LOS) angular rate and letting the relative velocity between missile and target be less than a negative constant, respectively. The command filtered backstepping approach can not only address saturation constraint on acceleration command but also overcome the deficiency of “explosion of terms” in the conventional backstepping method. Finally, the simulations are performed for controlling and non-controlling along LOS in the case of acceleration command saturation and missile autopilot with big lag. The results show that the guidance law has excellent performance for intercepting a highly maneuvering target.

Two-dimensional Numerical Calculation for the Influence of Plasma Jet Ignition on Deflagration-to-detonation Transition

LIN Ling, WENG Chun-sheng

2014, 35(9):  1428-1435.  doi:10.3969/j.issn.1000-1093.2014.09.015

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The multiphase detonation model of plasma jet ignition is calculated by the two-dimensional viscous CE/SE method. The influence of viscosity on the detonation flow field under the condition of the plasma jet is analyzed through N-S equation and Euler equation. The influences of different ignition temperatures and time of the jet and initial droplet radius on the process of deflagration-to-detonation transition (DDT) are analyzed. The calculated results show that the viscosity has a very small effect on the propagation of detonation wave, while has some effects on the detonation parameters. DDT distance can be significantly shortened by improving the initial jet ignition temperature and time. When the plasma jet has fully ignites explosive mixture, a continual increase in jet time has little effect on the decrease in the distance of DDT. When the droplet radius is less than 50 μm，the peak pressure of detonation wave increases with the increase in droplet radius. When the droplet radius is more than 50 μm, the peak pressure of detonation wave decreases with the increase in droplet radius.

Research on the Dynamic Model of a Partial Strapdown Platform and the Impact Analysis of Pitching Angle and theStability of Platform

DUAN Xiao-min， LI Jie， LIU Jun

2014, 35(9):  1436-1442.  doi:10.3969/j.issn.1000-1093.2014.09.016

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To solve the problem of that the traditional inertial navigation system can’t be used in the high speed rolling guided projectile, a partial strapdown platform with special structure is introduced. This platform can keep the micro inertial measurement unit (MIMU) stabilize on the roll axis and remain strapdown on the pitch and yaw axes. The principle of compound pendulum is considered in the design of platform. The stability of the platform is related to the restoring torque of the mass eccentricity. A mechanical dynamics model is established by mechanical analysis of projectile and partial strapdown platform. The roll angle and angular velocity of the platform’s inner shell at different pitching angles are obtained by applying the Runge-Kutta method to solve the differential equations of motion. The experiment is done in three-axis flight simulation test platform. The mechanical dynamics model is verified. The results show that the smaller the missile flight pitching is, the smaller the angle and the angular rate of the partial strapdown platform’s inner shell rolling are, and the more stable the partial strapdown platform is.

Design of Predictive Maintenance Platform for INS Based on GO Methodology and RCM

JIANG Xiu-hong， DUAN Fu-hai， CHEN Pu， JIN Xia

2014, 35(9):  1443-1450.  doi:10.3969/j.issn.1000-1093.2014.09.017

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A design method of predictive maintenance platform based on GO methodology and reliability-centered maintenance(RCM) is proposed for the complex structure, reliability analysis and optimal maintenance of inertial navigation system (INS). GO methodology is applied to build the INS reliability analyses model—GO chart. In order to realize the dynamic prediction and evaluation of the residual lives of components and the system reliability, the components reliability are updated continuously based on life distribution functions and time stress samples. For the INS that fails to meet the system reliability index, the maintenance priorities of all components are given quantitatively by adopting the comprehensive evaluation method to balance the affecting factors of components: contribution to system, failure likelihood and detection difficulty. Finally, some simulations are processed under the situations of constant failure rate, variable failure rate and fault isolation of INS components. The results show that the proposed predictive maintenance platform for INS is feasible and effective, and the predicted results can be used as a reference for making scientific maintenance decisions.

Numerical Simulation of Deep Closure of High-speed Water Entry Cavity of Cone-cylinder

MA Qing-peng, WEI Ying-jie, WANG Cong, CAO Wei, CHEN Chao-qian

2014, 35(9):  1451-1457.  doi:10.3969/j.issn.1000-1093.2014.09.018

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Numerical simulation for modeling the cavity formation process of high-speed water entry is performed. Finite volume method is introduced to discretize the Reynolds averaged Navier-Stokes equations. Results on the velocity and trajectory show good agreement with the results obtained by the analytical model. The flowing characteristics and pressure distribution of the deep closure stage are also studied. Results show that the deep closure occurs after surface closure and at a deep penetration depth for high-speed water entry problem, and the cavity collapses very quickly after the deep closure. The cavity closes under the effects of multiphase flow before the cavity wall shrinks completely, which induces high pressure around the deep closure area, and the maximum pressure always act on the separating points until the cavity collapses.

Research on Model and Simulation of Airborne Magnetic Anomaly Detection Sweep Width Based on Magnetic Dipole Model

YANG Ri-jie, XIONG Xiong, GUO Xin-qi, HAN Jian-hui

2014, 35(9):  1458-1465.  doi:10.3969/j.issn.1000-1093.2014.09.019

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The traditional sweep width model can not accurately predicate the impact of target magnetic feature, ambient noise on the airborne magnetic anomaly detection sweep width, the traditional sweep width model is improved by adding the idea of probability distribution, and a new sweep width model is proposed based on signal to noise ratio detection criterion. On the basis of establishing airborne magnetic anomaly detection encounter model based on magnetic dipole model, submarine magnetic signature model, ambient magnetic noise model and signal detection model, the calculation method and corresponding procedure for the new sweep width model are presented. Simulation results show that the improved model is effective and accurate in evaluating the effect of submarine magnetic features, geomagnetic dip angle, ambient magnetic noise and detection platform on sweep width of airborne magnetic anomaly detection. The improved model is more effective and accurate in estimating the sweep width of airborne magnetic anomaly detection compared with traditional sweep width model.

Numerical Analysis on Thermal Characteristics of Underwater Stream Turbine in Non-Design Condition

ZHANG Fang-fang， ZHANG Zhen-shan, LIANG Wei-ge，WANG Zheng-li

2014, 35(9):  1466-1472.  doi:10.3969/j.issn.1000-1093.2014.09.020

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To study thermal-power conversion law of underwater stream turbine in non-design condition, a calculation model of nozzle， turbine cascade and energy loss in turbine stage is established by considering adiabatic exponent variation along with temperature and heating effect of fluid friction and vortex losse. A thermal process simulation of an underwater stream turbine in the variation of temperature at nozzle entrance and pressure ratio is realized by use of the calculation program based on the established model. Results show that the simulation curves consist with thermal-power conversion law in non-design condition well, which validates the efficienceness of the model and simulation. For the studied engine, under changing pressure ratio, the velocity factor of nozzle determines the variation of inner efficiency of turbine engine and its wheel power, and the speed of nozzle exit working substance determines the variation of effective power of turbine engine and its wheel work. The proposed model can be seen as foundation for optimization design and control study of underwater turbine engine.

Posterior Probability Constraint Matched Field Processing with Environmental Uncertainty

WANG Qi， WANG Ying-min， GOU Yan-ni

2014, 35(9):  1473-1480.  doi:10.3969/j.issn.1000-1093.2014.09.021

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In an uncertain ocean environment, the environmental model used by matched field processing (MFP) is different from the real world. As a result of the environmental mismatch, the performance of MFP deceases largely. In order to improve its robustness to the environmental mismatch, a posterior probability constraint matched field processing (MFP-PPC) is proposed. The algorithm derives the posterior probability density (PPD) of the source locations from Bayesian criterion, then the main lobe of AMFP is protected by PPD, so MFP-PPC has not only the merit of high resolution as AMFP, but also the advantage of robustness. To evaluate the algorithm, the simulated and experimental data in an uncertain shallow ocean environment are used. The results show that MFP-PPC is robust not only to the moored source in the uncertain ocean environment, but also to the moving source. The tracking curve is consistent with the trajectory of the moving source.

Preparation of Ni-coated W Powder by Electroless Plating

ZHANG Hong-yan， WANG Ying-chun， LIU Jin-xu， ZHAO Zi-ying， GUO Wen-qi， LI Shu-kui

2014, 35(9):  1481-1487.  doi:10.3969/j.issn.1000-1093.2014.09.022

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The effects of W powder particle size, complexing agent, W powder loading on the electroless Ni plating on the surface of W powder are analyzed, and the morphology of coated particle, utilization rate of Ni and deposition rate are investigated. The controllable electroless Ni plating process parameters are optimized. The Ni-coated W powders are mixed with Cu powders, and then the mixed powders are sintered to prepare 67W-25Cu-8Ni alloy by using spark plasma sintering (SPS) technique. 67W-25Cu-8Ni alloy is analyzed by scanning electric microscope (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). Results show that, when W powder particle size is in range from 4 μm to 6 μm, the complexing agent of sodium pyrophosphate is 60 g/L, triethanolamine is 100 g/L, and trisodium citrate is 8 g/L. The Ni layer is uniform and complete, and the weight percent of Ni in W-Ni powder can be controlled by adjusting the W powder loading. Metallurgical bonding is achieved at the W/Ni/Cu interface. Compared with W-Cu alloy, the sintering density of 67W-25Cu-8Ni alloy prepared by SPS is greatly increased, reaching to 97%.

Reliability Model of Multi-state Repairable Systems with Different Repair Effects

DI Peng, LI Fang, CHEN Tong

2014, 35(9):  1488-1494.  doi:10.3969/j.issn.1000-1093.2014.09.023

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Three repair effects, namely repairing some system and making it as same as the original, imperfect and perfect, are proposed to research the reliability model of multi-state repairable systems with the different repair effects. The operating state is divided into two classes: good and general; the operation and repair times of system are assumed to submit to continuous phase-type distribution. An infinitesimal generator matrix for the Markov transfer among system states is established, and the stationary probability vector is achieved. The proposed model provides the analytic expressions of the stationary availability and failure rate. Finally, the numerical examples are given to illustrate the effectiveness and applicability of model.

Research Notes

Design and Experiment of Load Simulation System for Servo Mechanism of Rocket Engine Nozzle

ZHANG Peng, FU Yong-ling, GUO Yan-qing

2014, 35(9):  1495-1502.  doi:10.3969/j.issn.1000-1093.2014.09.024

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A new electro-hydraulic torque load simulator is proposed for the semi-physical simulation of the servo mechanism in launch vehicle, which could simulate the inertia load, friction and elastic torques, and servo mechanism mounting rigidity. On the basis of load characteristics of servo mechanism, the inertia , friction, and servo mechanism mounting rigidity are simulated for the mechanical structures, and the elastic load is simulated for the servomotor. The complete mathematical models of the motor loading system and the servo mechanism system are constructed. A control system of the servo mechanism is designed based on speed compensation and torque feed-forward. Some field tests of load simulation device were made. The test results show that the various loads meet accuracy requirements. The proposed design is reasonable and practicable, and the control system is effective.

Non-uniform Norm Constraint Estimation Algorithm for Underwater Acoustic Channels at the Presence of Varying Sparsity

WU Fei-yun, ZHOU Yue-hai, TONG Feng, FANG Shi-liang

2014, 35(9):  1503-1509.  doi:10.3969/j.issn.1000-1093.2014.09.025

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For the typical underwater acoustic channels with time-frequency double extension characteristics, the channel estimation performance can be improved by introducing a norm constraint into the channel estimation algorithm based on the sparse distribution feature of the channels. However, at the presence of varying multipath structure caused by change of depth or velocity gradient, the classic l₀ or l₁ norm constraint methods are subject to performance degradation due to lack of adaptability to sparsity. A previously derived non-uniform norm constraint LMS (NNCLMS) algorithm is introduced, and then a convergence analysis is made on it. In the form of non-uniform norm, the NNCLMS algorithm is used to accommodate the different sparsities caused by different multipath structures. Numerical simulation and sea experimental results show that the estimation performance of the proposed method is superior to that of the classic l₀ or l₁ norm constraint algorithm.

Research on the Law of Development of Outlet Cavity During the Launch of Submarine Launched Missile

QIU Hai-qiang， YUAN Xu-long， WANG Ya-dong， LIU Chuan-long

2014, 35(9):  1510-1514.  doi:10.3969/j.issn.1000-1093.2014.09.026

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During the launch of submarine launched missile with a gas-steam ejection system, an outlet cavity is formed because of a strong interaction between water and gas. The development of cavity has an effect on the motion of missile. Dynamic mesh and MIXTURE model are used to simulate the law of development of cavity: expansion, contraction and disruption. Pressures at different locations and the transmission process of pressure are also discussed. The shape of cavity is proved to have a negative correlation with the cavity pressure. The simulation result can be used for engineering prediction.

Study of Frictional and Viscosity-temperature Characteristics of a Space Lubricating Oil No.4129 in Rolling/sliding Contact

WANG Yan-shuang, CAO Jia-wei, LI Hang, LI Pu

2014, 35(9):  1515-1520.  doi:10.3969/j.issn.1000-1093.2014.09.027

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The frictional characteristics of a space lubricating oil No.4129 are tested by using the self-made friction test rig which can simulate the frictional characteristics of aerospace bearing. The viscosity of this oil is measured by the kinematical viscometer at the high and low temperatures. The effects of the temperature, rolling speed and sliding speed on the friction coefficient are analyzed. A viscosity-temperature model and a frictional characteristic model are established. The results show that its viscosity varies considerably when the temperature is below 0 ℃, and its viscosity varies slowly when the temperature is above 30 ℃. When the sliding speed is less than 0.3 m/s, the friction coefficient of this oil varies linearly with the sliding speed. When the sliding speed surpasses 0.3 m/s, the friction coefficient varies non-linearly with the sliding speed. When the sliding speed surpasses 1 m/s, the friction coefficient remains about the same with the increase in sliding speed. The friction coefficient decreases with the increase in temperture. When the rolling speed increases from 1 m/s to 3 m/s, the friction coefficient decreases quickly. Then the friction coefficient decreases slowly until it reaches the minimum value and keeps unchanged with the increase in rolling speed.