Table of Content

30 June 2004, Volume 25 Issue 3

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Paper

Optimal Design of System Efficiency Parameters about Terminal-Sensitive Projectiles Based on Neural Network and Genetic Algorithm

1:Huang Kun ;2:Chen Senfa;3: Liu Rongzhong

2004, 25(3):  257-260.  doi:10.3969/j.issn.1000-1093.2004.03.001

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Terminal-sensitive projectile is an advanced new-type of ammunition, having complex struc?ture and a multiplicity of influencing factors, the overall optimal design to the terminal-sensitive projectile system is thus a very difficult work. Neural network and genetic algorithm were used in this paper, because of the highly non-linear reflecting capability of neural network and the overall optimizing ability of genetic algorithm. Working principle of terminal-sensitive projectile was introduced, and a project of optimal design was confirmed. Using theory of neural network and orthogonal experiments, a simulating model of termi?nal-sensitive projectile system efficiency was established. On this basis, using a hybrid genetic algorithm, an optimal design to the neural network simulation model was carried out. From it an optimal arrangement of several main factors affecting the system efficiency was obtained. Validation to the above optimal results was then done, and some conclusions about this optimal design formed, showing that the optimal arrange?ment of those influencing factors are wholly in accordance with the actual state, and that the method can provide scientific foundations for the future efficiency research of terminal-sensitive projectile systems.

A Study on the Stochastic Control of Hydroelectric Active Suspension for Armored Vehicles and Rig Test

Zhang Yuchun, Wang Liangxi, Cong Hua

2004, 25(3):  261-266.  doi:10.3969/j.issn.1000-1093.2004.03.002

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A mathematical model was built up for hydroelectric active suspension in vehicles. Relying on optimal control theory, an optimal controller was designed. Suboptimal control strategy for active suspen?sion was studied in detail using minimized norm. A new method of sensitivity analysis for determining the feedback variable was proposed and used to solve problems in selecting feedback variables for engineering ap?plications. Based on actual vehicle parameters and theoretical studies, the suboptimal controller was de?signed. It was then simulated and tested with rig experiment. Simulation and experimental results shows that the suboptimal control strategy and sensitivity analysis proposed in the paper are feasible. It also shows that the suboptimal and optimal controllers have the same effects on vehicle vibration isolation. Within low?er frequency domains, they can both reduce vehicle body acceleration and tire displacement to some degree and are effective in enhancing the riding comfort and handling stability.

Temperature Field Analysis for Actively Cooled Barrel of Large Caliber Gun

1:Wu Bin,Chen Gang;2: Xia Wei, Tang Yong, Chen Puqing

2004, 25(3):  267-271.  doi:10.3969/j.issn.1000-1093.2004.03.003

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Temperature field of large caliber gun barrel was analyzed using FEA method and the analyti?cal results of naturally cooled monobloc barrels and actively cooled composite barrels were compared with each other. Based on the results of analysis, many key issues were particularly listed, viz. (I) Temperature field can be classified into two stages: tnermal initial regime and regular regime. For naturally cooled monobloc barrel，its thermal condition in regular regime can be evaluated by measuring the outside tempera?ture of two arbitrary rounds; (2) During a sustained firing process, unsteady heat conduction exists in a monobloc barrel，whereas unsteady and quasi steady heat conduction exist with actively cooled composite barrels, meaning that the thermal condition changes from uncontrolled to controlled;3）Different combi?nations of the convective heat transfer coefficient h and thickness of gun barrel δ have much effects on cool?ing the bore temperature. Existence of critical convective heat transfer coefficient hc shows that for natural?ly cooled monobloc barrel (h く hc)，weight and rigidity allowed, increasing δ can decrease the bore tem?perature. As for actively cooled composite barrel (h >hc), large h and small δ is selected when strength and manufacturing processes are considered simultaneously.

A Study on Ammunition Link Design by the Parameters Matching Analysis Method

1:Peng Fengsheng;2:Liang Shirui

2004, 25(3):  272-275.  doi:10.3969/j.issn.1000-1093.2004.03.004

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A method of link design for belt-feeding automatic gun was investigated, scientific and ratio?nal choice of the basis of geometrical constructional parameters for link design was derived. The parameters of automatic mechanism，ammunition and link were studied from the view of an automatic gun system as a whole ? Through analyzying the forces on the round during feeding，the parameters matching basic equations of link design was develped. It is proved that the mechanical performance parameters of the link designed by the method are generally consistent with the test results.

Perpendicular Impact Guidance Law Based on Genetic Algorithm

1:Zhang Anmin,Han Chongzhao ;2:Yang Shixing, Li Zhishun

2004, 25(3):  276-279.  doi:10.3969/j.issn.1000-1093.2004.03.005

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guidance law is the core question for a torpedo in fulfilling its precision homing and executing its action. The paper lays emphasis on the question about the genetic algorithm applied in the guidance law of a torpedo. The feasibility and superiority of genetic algorithm in torpedo perpendicular impact guidance law were studied. Gradual change in the angle oi lead in torpedo homing guidance law was proposed on the basis oi the character of genetic algorithm, and corresponding simulation was made. It is shown that the guidance based on genetic algorithm has a rapid response and robustness feature. The question of astringen- cy of guidance law is also solved, so it has a prospective engineering utility.

2-D Maze-Mapping Verification Method for the Counter-Meshing Gears Mechanism

1:Gao Yang, Chen Xun,Su Wei;2: Zhao Xiaolin

2004, 25(3):  280-284.  doi:10.3969/j.issn.1000-1093.2004.03.006

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Counter-meshing gears mechanism is a coding and discrimination mechanism, which can be used for safety and arming surety applications. Based on a reported CMG instance, the structure, working principles and essential concepts of the CMG mechanism were briefly educed. The so called 2 dimensional maze-mapping method for CMG teeth-coding verification was presented. The method is simple, clear and easy for use. Applying the method to the same instance, some critical issues were analyzed in detail, and conclusions were given.

An Investigation on Explosive Deformable Warheads

1:Zeng Xinwu, Wang Zhibing, Zhang Zhenyu, Lu Fangyun;2:Tan Duowang

2004, 25(3):  285-288.  doi:10.3969/j.issn.1000-1093.2004.03.007

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Explosive deformable warhead is the kind of aimable warhead that has the ability to concen?trate its lethal effects on targets at larger distances than normal isotropic blast fragmentation warheads. Re?sults of study on the explosive deformable charge were presented. Two key parameters for the design of ex?plosive deformable warhead were identified, vid： width of the isolated deformation charge, and delaying of initiation time between the deformation charge and the main charge. Several groups of combination of the above parameters were studied both by numerical simulation and experimental research. The distribution density and initial velocity of fragmental were obtained. Based on these results, an optimized explosive de?formable warhead model was obtained. The results demonstrate good concentration of fragmentation on the aimed point providing about ten times as much as compared to the isotropic mode. The initial fragment ve?locity measured has also been increased by about 10 % ?

Influence of Modes of Detonation on the Mechanism of Jetting Projectile Charge

Huang Zhengxiang, Zhang Xianfeng, Chen Huiwu

2004, 25(3):  289-291.  doi:10.3969/j.issn.1000-1093.2004.03.008

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Jetting projectile charges are mainly used against new types of defending armor, armored con?crete, helicopters, large surface vesels etc. They are different from shaped charges and explosion formed projectiles. The head volocity of a jetting projectile charge can attain 3000?4000 m/s. It is not sensitive to standoff. But its depth of penetrated is larger than EFP. In this paper was discussed the influence of modes of detonation on the mechanism of jetting projectile charge and was obtained the relationsmp of head veloci- ty and length-diameter ratio upon different detonation modes through analysis. This has been validated by X-ray investigations.

The Formation of Asymmetric Jet and Slug

Jiang Jiansheng, Hang Yihong, Feng Qijing

2004, 25(3):  292-295.  doi:10.3969/j.issn.1000-1093.2004.03.009

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A moaitied symmetry model to resolve the problem of asymmetric collision was given and the characteristics of the jet and slug were predicted. Analytic solutions of the model were compared with the numerical results and with the other two analytic model?the straight assumption and the circle Hypothesis. Results superior to that obtainable with the straight assumption and circle hypothesis can be arrived at.

Studies on the Decrease of Impurity Contents in HNIW Prepared form TADBIW

Liu Jinquan, Ou Yuxiang, Chen Boren

2004, 25(3):  296-299.  doi:10.3969/j.issn.1000-1093.2004.03.010

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γ-HNIW was prepared from TADBIW with a yield of 90 % and purity of more than 98 % . It has been proved that PNMAIW was the predominant impurity in the obtained HNIW. According to the re?sults of thin-layer chromatography (TLC) and high performance liquid chromatography (HPLC)，the de?pendence of yield of HNIW and PNMAIW contents in HNIW on the nitrolysis conditions was summarized and discussed.

Mechanism of Optical Birefringence Effect on a Thin Film Magnetic Fluid Situated in a Magnetic Field

Wang Zhengliang

2004, 25(3):  300-303.  doi:10.3969/j.issn.1000-1093.2004.03.011

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This paper analyses the mechanism how a thin film magnetic fiuia shows optical bireiringence in a magnetic field. A magnetic fluia is found to be a directional colloid with weak f locculation, i.e. a fluid in a critical state from the colloidal state to that of flocculation. Once in a magnetic field a magnetic fluid with weak flocculation has its own particular direction, where the colloid system does not lose its stability. Thus the thin film magnetic fluid shows optical birefringence in a magnetic field revealing the mechanism that directional weak flocculation of the magnetic fluid causes optical birefringence in a magnetic field. This will provide design foundations for further research of optical instruments based on magnetic fluid.

A Study on the Dynamic Characteristics of Accelerometers Working on Gyro Free Micro Inertial Measurement Units

1:Chi Xiaozhu, Wang Jinsong,Wang Daming;2:Jin Hongzhang

2004, 25(3):  304-307.  doi:10.3969/j.issn.1000-1093.2004.03.012

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The dynamic characteristics of accelerometers working on gyro free micro inertial measure?ment units was discussed, with a piezoresistive accelerometer as an example. A model of gyro free micro in?ertial measurement units with nine accelerometers was first set up and used to calculate the navigational e- quations and to improve on it based on the dynamic characteristics of accelerometers, and simulation valida?tion was finally processed. For the same accelerometer, the stronger the dynamic characteristics of input signal, the larger the error ot inertial unit will appears as the result of simulation. So the selection of ac?celerometers having the best dynamic characteristics helps to improve the features of gyro free micro inertial measurement units. A theoretical basis was established for the practicability of gyro free micro inertial mea?surement unit.

Response Analysis on Structures with Steel-Net Damper

1:Wang Ke;2:Zhang Fuxiang

2004, 25(3):  308-311.  doi:10.3969/j.issn.1000-1093.2004.03.013

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Based on tne features of a steel-net damper, an unsymmetrical parameter model was estab?lished and identification of related parameters achieved through conducting single degree of freedom forced vibration test. In this process, problems of reducing the noise of the displacement signal and spotting pre?cisely its peak point were solved; and nonlinear parameter identification was changed into piecewise linear i- dentification of parameters. Based on the steel-net damper model, a method for calculating the dynamic re?sponse of the complex structure was deduced, involving nonlinear steel-net dampers. With the test structure as a sample, the response characteristics of the complex structure were calculated. Its result matches well with the experiment. This study lays a theoretical foundation for the application of the nonlinear damper in engineering.

Calculation of Aerodynamic Characteristics with Exisence oi the Bomb-Wing-Body Configuration Disturbance

Wei Jingbiao, Xue Xiaozhong, Mi Zhihao, Shu Jingrong

2004, 25(3):  312-314.  doi:10.3969/j.issn.1000-1093.2004.03.014

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The panel method brought forward by Woodward was improved. Taking the bomb under the wing of the plane as an example，lots of panels were plotted on the external surface of the bomb-wing-body configuration. Based on the improved panel method, aerodynamic parameters of the bomb were calculated with the existence of the bomb-wing-body configuration disturbance and compared with the experimental values and values free of disturbance. A brief analysis is executed. The result indicates that the disturbance is mainly from the wing. Witn the dropping of the bomb and the increase of the distance between the bomb and the wing, aerodynamic parameters swiftly approach values free of disturbance.

An Analysis on the Critical Speed Marking the Occurance of Hydroplaning for Wheeled Vehicles

Kong Jiangsheng, Lü Haitao, Zhu Tianjun

2004, 25(3):  315-317.  doi:10.3969/j.issn.1000-1093.2004.03.015

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Speed Control of a Remote Towing Vehicle for Moving Targets

1:Liu Li, Geng Cong;2: Chen Huiyan ,Yang Donglai

2004, 25(3):  318-321.  doi:10.3969/j.issn.1000-1093.2004.03.016

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Structure and the worKmg process of a remote control vehicle for target towing were present?ed. Methods of control in automatic gear shifting and engine speed modulation were described. Techniques of automatic control for venicle driving are applied in developing this remote control vehicle, which is e- quipped with actuators to control the clutch, gear shitting mechanism and actuators of throttling. Sensors reflecting conditions of vehicle driving and actuators are introduced. Digital controls that are characterized using single - chip computers, realize the flexible strategies for vehicle speed control. Practical applications show the high performance of this vehicle speed control. Demands on speed accuracy in remotely controlled targel venicles are satisfied.

Low-Pressure Casting of Large Sized Filling with Electromagnetic PumpsComplex Aluminum Castings

1:Hou Jibo, Cheng Jun,Peng Yougen ，Dang Jingzhi;2:Huo Lixing

2004, 25(3):  322-325.  doi:10.3969/j.issn.1000-1093.2004.03.017

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With experimental comparison between the imitated dual electromagnetic pumps and the sin?gle pump, parameters such as the structure of magnets, flux, and other data were collected for the design of the large flow-rate electromagnetic pump. One such unit was designed and made for the low-pressure cast?ing system with the electromagnetic pump casting large sized for complex aluminum castings in vehicles. Ensurance of nearly equal parameters of the two single pumps is the effective measure to enhance the effi?ciency of working of the dual electromagnetic pumps.

A Study on Radial Online Liquid Equilibrator for the Grinding Wheel

1:Li Xiaodong;2:Wang Liwei, Ji Qingfa

2004, 25(3):  326-329.  doi:10.3969/j.issn.1000-1093.2004.03.018

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A radial online equilibrator for grinding wheels was proposed in this paper. The device solves the problem of balancing of grinding wheels online, and overcomes the shortcomings of devices now in use. The principle and method for the calibration of amount of unbalance were proposed.

A Sort of Iterative Learning Control Algorithm for Tracking of Robot Trajectory

Yao Zhongshu, Wang Hongfei, Yang Chengwu

2004, 25(3):  330-334.  doi:10.3969/j.issn.1000-1093.2004.03.019

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An iterative learning control with forgetting factors for the tracking of robot trajectories was proposed, and conditions were presented to guarantee convergence of the iterative algorithm. The conver?gence of error can be improved without modifying the structure of the controller by utilizing previous experi?ence in tracking different desired trajectories to select an initial control input for a new desired trajectory tracking. The output of the system can track the desired trajectory better. A simulation shows the fast con?vergence of the proposed algorithm.

Tribological Behavior of M0S2 Base Composite Cbatings Deposited by NCUPP Process

Han Chengming, Zhou Lanying, Jia Qinglian, Lang Ping

2004, 25(3):  335-339.  doi:10.3969/j.issn.1000-1093.2004.03.020

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A method of depositing solid lubricating coatings (TiN-MoS2/ Ti) , named NCUPP (Nano- Composite Unbalanced Plasma Plating)，has been developed. The microstructures and chemical composition of the coating was studied by scanning electron microscopy (SEM)，X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The TiN-MoS2/ Ti composite coating deposited by NCUPP process possesses good tribological behaviors, such as lower friction coefficient, higher wear-life and higher ability of humidity-oxidation resistance.

Short Papers

Numerical Simulation of Ballistic Penetration of Laminated Composite Panels

Chen Xiao, Zhou Hong, Wang Xiting

2004, 25(3):  340-344.  doi:10.3969/j.issn.1000-1093.2004.03.021

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The paper focuses on the optimization of material properties, lamination sequence, layer num?bers and processing to further improve the ballistic resistance capability of military ballistic helmets and mili?tary body armors currently in use. Associated with v50 ballistic experiments and analyses on penetrated form and broken fibre picture, nonlinear dynamic explicit finite element analysis software ANSYS/LS-DYNA version 5.6.1 was used to simulate the penetration of several kinds of bulletproof composite panels by stan?dard 1.1g fragment simulating projectiles. Upon simulation of the history of damage of the panels were ob?tained ，and the failure and energy absorption mode of the composite panels was discussed on the basis of nu?merical simulation and ballistic experiments. Bulletproof panels with three thickness segments of non-homo?geneous structures and material processing are suggested.

An Umbrella Shaped Laser-Fiber Coupler

Song Guicai,Ning Guobin, Yan Xiaoyuan, Ren Zhong, Liang Zhu;2:Quan Wei

2004, 25(3):  345-348.  doi:10.3969/j.issn.1000-1093.2004.03.022

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The coupling of a high-power，high-energy and narrow pulse laser unit with the optical fiber is important and of unique value in laser applications. Existence of the damage threshold in the fiber end face makes it very difficult to realize the coupling through lenses. In this paper was designed an umbrella shaped laser-fiber coupler by analyzing the mechanism of damage of an optical fiber and realized a coupling of a high-power (10MW) , high-energy (20mJ), narrow pulse (20ns) and high frequency electrooptical Q- switched Nd: YAG laser with a multimode optical fiber. Ihe coupling efficiency is over 80% .

Detection and Imaging of Slowly Moving Target of Airborne Synthetic Aperture Radar Based on the GMCWD-Hoi^h Transform

Wang Ling, Tao Ran, Zhou Siyong

2004, 25(3):  349-353.  doi:10.3969/j.issn.1000-1093.2004.03.023

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Features of airborne SAR moving target echoes were analysed and the generalized-marginal Choi -Williams distribution-Hough transform ((_tMCWD-HT) was introduced. According to the echo model of airborne SAR，a new method based on the generalized-marginal Choi-Williams distribution-Hough trans?form for detection ana imaging the slowly moving targets of airborne SAR was proposed. Based on the joint time-frequency processing method, the new approach using the accurately estimated parameters of the slow?ly moving target can be realized to perform detection and imaging of the target of airborne SAR in the low signal to clutter ratio. Its detecting performance is better than the common method based on Wigner-Ville distribution. Computer simulation results prove the validity of the approach.

Comprehensive Reviews

Researche and Development of HNIW Synthesis

Zhao Xinqi, Fang Tao, Sun Chenghui

2004, 25(3):  354-358.  doi:10.3969/j.issn.1000-1093.2004.03.024

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Hexanitmhexaazaisowurtzitane( HNIW)，is a compound of high energy density having a vari- ety of applications in prospect. The routes of synthesis in its preparation were reviewed. Three nitrolysable precursors to HNIW， including tetraacetyldibenzylhexaazaisowurtzitane(TADB )，tetraacetyld- iformyllhexaazaisowurtzi-tane( TADF) and tetraacetylhexaazaisowurtzitane(TAIW) were discussed empnat- ically in terms oi their prpcess safety, product purity and costs of production.

Experimental Techniques and Analysis

Mecro-Damage Study of Hollow Steel Projectiles Impacting Steel Plates

Wang Fuchi, Wang Lin, Li Shukui, Wang Lu

2004, 25(3):  359-362.  doi:10.3969/j.issn.1000-1093.2004.03.025

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A study with the main objective to investigate the mecro-damage mechanisms occurring in hol?low projectiles made of three different steels after penetrating 45 # steel plates was presented. After the ballistic impact tests, the mode and distribution of mecro-damages were examined using optical, scanning and transmission electron microscopies. It is found that void and adiabatic shear band were two main mecro- damage mechanisms. When projectiles impact steel plates at relatively low velocities and keep intact after penetration, void is the controlling mecro damage mechanism. When projectiles impact the targets at high velocities and larger deformation and fracture take place, located at the ogival head of projectile or at transi?tion region from head to body, adiabatic shear band (ASB) is the mecro-damage counterpart. Adiabatic shear banding sensitivity can be taken as the main mecro-damage consideration when the deformation be?havior and penetration performance of hollow projectiles are assessed. Transmission electron microscopy ob?servations show that shear bands were of transformed type and dynamic recrystallization occured inside the bands.

Experimental Investigation of Gumey Flaps on the Aerodynamic Characteristics of Highly Swept-Back Plane-Delta Wing

Zhan Jingxia, Wang Jinjun ,Li Yachen

2004, 25(3):  363-367.  doi:10.3969/j.issn.1000-1093.2004.03.026

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The effects of Gumey flaps on the aerodynamic characteristics of plane-delta wing with a sweep angle of seventy degrees have been investigated through wind-tunnel experiment at a chord Reynolds number of 3.16 X IO5. The experimental results indicate that Gumey flap can apparently increase the lift coefficient as well as the drag coefficient of the plane-delta wing, making the lift-drag ratio increase when the lift coefficient is large enougn. Gurney flaps with dimensionless height of 2.0 and 2.5% increase the lift-drag ratio of the delta wing much more than others tested in the experiment. Increments up to 40 per?cent can be attained in comparison with the lift-drag ratio oi delta wings without the Gurney flap.

An Intelligent Fatigue Test System for Crankshaft

Yu Xiaoli, Zkou Xun ,Liu Zhentao, Shen Yuming，Qi Fang

2004, 25(3):  368-371.  doi:10.3969/j.issn.1000-1093.2004.03.027

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In order to improve the accuracy and efficiency of crankshaft fatigue testing machine generally in use, a new crankshaft fatigue testing system with intelligent control has been developed. The core of control of the system consists of a PLC (programmable logic controller) and a PC. The PLC can run steadi?ly for a long period of time and protects the system from power-off, greatly improves the reliability of the test system; and the PC, with its specially programmed software, processes the calibration data and the test data quickly and precisely, and provides a friendly interface between the system and the operators. This system achieves full test automation including calibration, running, failure diagnosis and data processing, establishing it as an intelligent test system. A detailed description of the principle, constitution, functions, and work flow of the system were given in the paper.

An Experimental Study on the Reduction of Nox in Turbocharged Diesels by Exhaust Gas Recirculation

Ji Changwei, Han Aimin, Zhao Yong, Ma Hui

2004, 25(3):  372-375.  doi:10.3969/j.issn.1000-1093.2004.03.028

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The effect of exhaust gas recirculation(EGR) on NOx emissions from turbocharged diesels was studied. Natural EGR was carried out by inducing the cooled low pressure exhaust gas after the turbocharg?er to the low pressure intake air directly before the compressor. Natural EGR is unable to reduce NOx suffi?ciently under all specified operating conditions. Pressurized EGR was accomplished through compressing the cooled low pressure exhaust gas after the turbocharger into the high pressure intake air after the intercooler. Pressurized EGR can decrease NOx to the specified degree under specified operating conditions. Engine tests show that NOx are decreased by approximately 6% ?18% by natural EGR and 22% ?53% by pressurized EGR.

Research Notes

Optimization Design for the Ballistics of Simply ijruided Bombs

Xue Xiaozhong, Sun Chuanjie

2004, 25(3):  376-378.  doi:10.3969/j.issn.1000-1093.2004.03.029

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Based on the guidance for a simply guided bomb, chief factors having impact on the range and accuracy of the bomb were analyzed. The ballistic equation adopted in the ballistic project design was de?rived. A mathematical model of ballistic project in accordance with restrictions of accuracy of control, veloc?ity, normal overload and angle of yaw of the rudder etc, was established. In this model abrupt change of pitch angle ti,t2 depending on the control device are set as the design variables, and the range is set at the target function. Numerical simulation was performed. The results of numerical simulation of the model in?dicate that the maximum range is achieved and the accuracy of the bomb is satisfactory.

A New Method of Estimating Signal Parameter via Rotational Invariance Techniqu eBased on Fourth-Order Cumulants

Xu Yougen, Liu Zhiwen

2004, 25(3):  379-381.  doi:10.3969/j.issn.1000-1093.2004.03.030

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Based on the interpretation for the use of fourth order cumulants, a new KSPRIT-like method was presented. The method can be used to estimate the direction of arrival(DOA) directly from the eigen?values of a lower-dimension DOA matrix constructed by the virtual rotational invariance matrix pencil, and gain a higher array aperture utilization than the conventional ESPRIT methoddoes. simulation results show that the proposed method is effective.

Exploration on a Kind of Measurement Scheme for the Dispersion of Fiber Gratings

Fang Juanni, Wang Shengkun

2004, 25(3):  382-384.  doi:10.3969/j.issn.1000-1093.2004.03.031

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The quality of fiber grating dispersion and reflection was analysed based on tne coupled wave equation of uniform cycling Bragg fiber gratings. Conservation of electronic and magnetic quantities and Hamiltonian system were made use of to get the relationship between the dispersion and reflection coeffi?cients. A simple measurement scheme for fiber grating dispersion was thus obtained by first measuring fiber grating reflective spectrum with a spectrometer, and then obtaining the dispersion coefiicient of fiber grat?ing through calculations.