纬度对陀螺经纬仪的影响测试分析

理论分析了纬度对陀螺经纬仪的影响规律,纬度越高陀螺指向力矩越小,陀螺仪跟踪周期和不跟踪周期越长,由此引起的陀螺经纬仪测量精度随纬度增高而趋势性变差。利用4台高精度陀螺经纬仪在纬度间隔约5°条件下进行了实地测试实验。结果表明,纬度从18°升高到53°,陀螺经纬仪测量精度变化约在3″左右,实验结果与理论分析结果一致。在考虑随机误差、仪器常数稳定性等其他因素影响的情况下,对中低精度的陀螺经纬仪影响可以接受,而对于高精度陀螺经纬仪不可忽视,可通过适当的测试数据拟合方式对纬度影响进行补偿。     

新型陀螺经纬仪用光电转角检测装置的设计与实现

介绍了基于精密线阵CCD传感器的光电转角检测装置的工作原理、设计方法、软硬件构成及对数据处理的分析,并介绍了系统在宽温工作条件下对温漂的数字校正技术。     

摆式陀螺经纬仪粗寻北的新方法

针对现有摆式陀螺经纬仪粗寻北方法存在的不足,提出利用检测陀螺力矩实现陀螺经纬仪粗寻北的新方法.推导了陀螺力矩对轴承的水平作用力与陀螺主轴方位角之间的数学公式,在地球自转角速度相对陀螺转子角速度非常小的情况下,对公式进行了简化和仿真运算.采用该方法改进了某型号陀螺经纬仪的粗寻北,实验表明在不影响陀螺经纬仪测量精度的前提下,简化了操作程序,缩短了测量时间.     

小型静电陀螺电极划分方式对转子电位及陀螺精度的影响分析

就小型静电陀螺电极划分方式对转子电位的影响进行了理论分析及仿真,并深入研究了转子的非零电位对陀螺精度的影响,为小型静电陀螺电极结构的设计提供了理论依据。     

开关电源噪声对光纤陀螺精度影响的研究

针对光纤陀螺专用开关电源集成化,分析了PWM波形变化以及开关频率引起的噪声对陀螺精度的影响。测试结果表明:对零漂为0.3 ()/h的中精度陀螺,开关电源噪声对陀螺精度没影响。     

三轴台陀螺伺服状态的实现

本文阐述了陀螺伺服状态中陀螺作为敏感元件给系统带来的新问题,即带进了陀螺的时间常数及其他问题,以及对于动力调谐陀螺这些问题的处理.为保护陀螺,在大偏差时加入测速机进行阻尼,当小偏差时死区电路自动切断测速机回路以确保伺服精度.文中还介绍了其他提高伺服精度的措施,如增大带宽及抑制干扰等,并对伺服数据进行了分析,说明陀螺伺服状态设计是正确的,实践上是可行的.     

加速度计的交叉耦合对无陀螺惯性测量组合影响的研究

研究了加速度计的交叉耦合系数的大小对惯性测量组合的影响，推导了存在交叉耦合系数的惯导方程，从方程中可以看出交叉耦合系数对导航精度的影响，最后通过仿真验证了这种影响。该的研究为无陀螺惯性测量组合的实际应用奠定了基础，并对加速度计的选用具有一定的指导意义。     

静电陀螺监控器对航天器定轨精度影响分析

航天测量船与陆基测控站在对航天器进行轨道跟踪测量中存在很大区别,陆基测控站是定点测控,定轨精度完全取决于无线电设备自身精度,而测量船是海基动态测控,定轨精度除受无线电设备自身精度影响,更大程度上受制于惯性导航系统(INS)提供的船姿船位(航向、船摇、位置)数据精度。测量船为提高船姿船位数据精度,使用了静电陀螺监控器(ESGM)与惯性导航设备(INS)、全球卫星导航系统(GNSS)相结合的组合导航系统。结合INS/ESGM/GNSS工作原理和测量船航天器定轨中船姿船位数据源的选择,将船姿船位数据精度对测量船定轨精度的影响进行了仿真,并通过无线电设备实测数据的事后数据处理对仿真结果进行了验证。研究结果表明,ESGM能够在很大程度上提高测量船航天器的定轨精度。     

光纤陀螺标度因数的测试误差分析

为了进一步提高光纤陀螺标度因数的测试精度,对光纤陀螺标度因数测试过程进行理论分析,确定了影响光纤陀螺标度因数测试误差的主要因素,并进行了计算机仿真和实验验证。结果表明:由于安装误差、北向地速分量以及转台速率精度的影响,光纤陀螺测试起始位置和采样时间的选择均会给小速率标度因数不对称性和非线性度的测试带来误差,而大速率标度因数的测试基本不受影响;通过对各输入速率点进行整圈采样,可以有效地降低小速率标度因数的测试误差,使其测试精度提高1个量级以上,实现对光纤陀螺标度因数性能更加准确的测试。     

带有惯性敏感元件的新型陀螺测试转台系统控制器设计

传统原理的陀螺测试转台使用测角元件测量转台的角速率,其精度与所选的角度(或时间)间隔关系极大,即使综合使用各种控制方法也难以达到理想的速率精度和速率平稳性。提出一种新的测速原理,将惯性敏感元件引入转台测试系统测量瞬时角速率,瞬时速率能够很好地反映速率精度和速率平稳性,通过反馈与控制瞬时角速率信息提高转台的速率精度和速率平稳性。探讨了带有惯性敏感元件的新型转台的控制系统组成,进行控制系统设计时,将闭环系统按功能划分成测量回路和稳定回路,并运用数字控制解决控制器综合问题,使用Matlab软件分析系统主要变量响应过程。最后,由控制器设计过程和所得模型分析结果证实,相对传统转台,新型转台的数字控制系统具有较高鲁棒性,响应时间缩短为0.15 s,更适宜于陀螺仪表的动态测试。     

Free v/s forced vibrations of a cylinder at low Re

Free vibrations of a circular cylinder of low non-dimensional mass are investigated at low Reynolds numbers. Computations are carried out for 5% blockage. Lock-in is observed for a range of Re and is accompanied with hysteresis at both lower as well as higher Re ends of the synchronisation/lock-in region. It is well known that the lock-in regime for free vibrations depends on the non-dimensional mass of the oscillator. The results from the present computations are compared with the data for forced vibrations from Koopmann (Journal of Fluid Mechanics, 28, 501–512, 1967) on a Y _max/D vs. f* plot, where Y _max is the maximum oscillation amplitude and f* is the ratio of cylinder vibration frequency to the vortex shedding frequency for a stationary cylinder. Good agreement is observed for the critical amplitude needed for onset of synchronisation between the forced and free vibrations. The results from the free vibrations are compared to the predictions from the linear oscillator model by assuming that the forces on the cylinder are unaffected as a result of vibrations. It is found that, for low mass oscillators, the modification of vortex shedding frequency and lift coefficient due to cylinder oscillations leads to the enhancement of the lock-in regime.     

Nonlinear rossby waves forced by topography

Using a barotropic semi-geostrophic model with topographic forcing the stability and solutions of the nonlinear Rossby waves are discussed. It is found that the effects of the W-E oriented topography and the N-S oriented topography on the stability and phase speed of the waves are quite different. It is also found that the nonlinear Rossby waves forced by the topography can be described by the well-known KdV equation.     

圆筒装置内爆炸压力载荷特性实验研究

为了研究密闭环境压力载荷波形特征和分布规律,开展了长径比2∶1圆筒装置的TNT装药内爆炸实验,获取了圆筒壁面、端盖板表面的压力载荷数据,结合仿真计算结果,研究了圆筒壁面、端盖板上压力载荷波形特征和形成机理,建立了压力载荷峰值的表征模型,并开展了模型验证。结果表明,圆筒壁面与盖板压力载荷波形不完全相同,壁面压力载荷按照爆心距由近到远,从显著的单波峰向多峰值变化,在近场区域压力载荷衰减特性与一定炸高自由地面冲击波类似;盖板上压力载荷呈多波峰特点,中心区域压力载荷最大峰值大于首峰值的3倍,角隅区域大于首峰值6倍;圆筒壁面上的压力载荷最大峰呈现凹型分布规律。该研究结果可为密闭环境内爆载荷的特性分析和结构毁伤评估提供参考。

     

Finite element simulation of steady state and transient forced convection in superfluid helium

In this paper, the solution of transient mass, momentum and energy balances in superfluid helium are discussed by means of a finite element algorithm. A simple linearization procedure is used for the non‐linear pseudo‐diffusion term in the energy balance arising because of the unique counterflow heat transport mechanism in superfluid helium. The linearization algorithm is analyzed for accuracy order and stability. The reliability of the algorithm devised is shown in practical tests, comparing the numerical solutions with experimental data available in the literature. Copyright © 1999 John Wiley & Sons, Ltd.     

Conjugated laminar forced convection in ducts with periodic variation of inlet temperature

Conjugated laminar forced convection with parabolic velocity is studied for flow inside both parallel-plate and circular ducts subjected to a periodically varying inlet temperature. The analysis of this classs of problems lead to a Sturm-Liouville type complex eigenvalue problem for which no known solution is available. In this work, a new methodology is presented for a direct solution of such complex eigenvalue problems in the complex domain using the shooting method along with the Runge-Kutta method. The methodology is applicable for solving both laminar and turbulent flow problems; here we consider only the laminar flow with a parabolic velocity profile. The results clearly show that the slug-flow assumption overestimates the phase lag and the Nusselt number. Some benchmark results are also presented for the eigenquantities in tabular form.     

Chaotic dynamics of periodically forced spheroids in simple shear flow with potential application to particle separation

In this paper, we consider the technologically important problem of periodically forced spheroids in simple shear flow and demonstrate the existence of chaotic parametric regimes. The approach used by Strand (1989) (for the Strong Brownian limit) is inappropriate in the chaotic regimes corresponding to the weak Brownian limit. Our results also indicate a strong dependence of the solutions obtained on the aspect ratio of the spheroids. This strong dependence on the aspect ratio may be utilized to separate particles from a suspension of particles having different shapes but similar sizes.     

Radiation and laminar forced convection of non-Newtonian fluid in a circular tube

Interaction of radiation with thermally developing laminar forced convection of power-law, non-Newtonian, absorbing, emitting, isotropically scattering, gray fluid through an isothermal circular tube with a black boundary is investigated. The energy equation is solved by an implicit finite-difference scheme, while the radiation part of the problem is solved by the collocation method. Results are presented for the effects of conduction-to-radiation parameter, single scattering albedo, optical thickness and the inlet temperature on the local Nusselt number along the tube for the case of power-law index n=1/3, 1 and 3, where the case n=1 corresponds to the Newtonian fluid.     

Reciprocal theorem method for the forced vibration of elastic thick rectangular plates

I.IntroductionTheproblelllsofthefol.cedvibrationofelasticthickrectallgularplatestobesolvedareofgreattheoreticalsignificanceandpractical\7altle.Asthevibratinggoverningequationofthethickplateismorecomplicatedthallthatofthinplate.itisdil'ficulttoso]\'einmathematics.Manyscholarshat,eresearchedintotheseproblemsalldadvancedvariousspecialapproximations.Suchassuperpositionmethod.initialfLinctiollnletllod.thecombinedseriesot'theeigenftlnctionsofdeepbeamabouttilecorrespondillgboulldarycollditions.eller…     

Experimental investigation on forced convective heat transfer and pressure drop of ethylene glycol in tubes with three-dimensional internally extended surface

A new type of tube is introduced that has a three-dimensional internally extended surface used to enhance convective heat transfer inside the tube. Results are presented from experimental investigations into heat transfer performance in seven copper tubes of about 13.5 mm I.D. with three-dimensional internally extended surfaces (3-DIESTs) varying in axial pitch, circumferential pitch, height, width, and fin arrangement. The heat transfer and pressure drop characteristics of ethylene glycol flowing in the 3-DIESTs were tested in the Re range 250–7000 and Pr range 60–90. The average Stanton number in the most superior 3-DIEST can be increased by about 2.8-fold in laminar flow and 4.5-fold in transitional and turbulent flow compared with that in the smooth tube. The corresponding friction factor is 1.7-fold as high in laminar flow and fourfold in transitional and turbulent flow inside the 3-DIEST compared to that inside a smooth tube. The correlations of heat transfer and friction factor are obtained separately in the different flow regions that can be used in practical design.     

双层石墨烯系统稳态受迫振动问题中的辛方法

针对悬臂石墨烯系统提出一种求解其稳态受迫振动问题的辛解析方法。基于Eringen非局部理论,将石墨烯层板受迫振动问题导入哈密顿体系。采用边界条件分解技术,将问题化为三种边界条件的子问题。通过辛解析方法,得到由辛本征值和辛本征解表示的双层石墨烯系统受迫振动问题的解析解表达式。数值结果表明,辛本征解级数具有很好的收敛性和精度,并与文献结果吻合;在一定的外载激励下可发生同向振动模式和反向振动模式;在一定的参数下,得到一些新的现象和结论。