共查询到20条相似文献，搜索用时 406 毫秒
1.
Peng Guangzheng Chen Ping Zhao Tong 《北京理工大学学报》1999,19(3):71
Aim To present a new kind of
pneumatic position control system based on the analysis of the disadvantages of
conventional pneumatic position control systems. Methods The new kind of pneumatic
position control system used a new kind of actuator-cylinder with a built-in brake and a
displacement sensor. And PWM control method and fuzzy control algorithm were utilized in
the system to control the position of the cylinder, and the brake was used to fix the
cylinder to its target position after it reached the position.Results The stiffness of the system was
experimentally proved to be greatly improved and the position precision to be within
0.15mm. In addition, the system is free of great shock and wear. Conclusions The new kind of pneumatic
position control system is free of the disadvantages of conventional systems, and is of
practical value. 相似文献
2.
Ma
Siyu 《北京师范大学学报(自然科学版)》2000,36(2):209-212
The optical
nonlinear coefficient of nonlinear glasses is studied by transmission coefficient in a
nonabsorption region or when absorption can be ignored. Numerical relations between
nonlinear coefficient and transmission coefficient are presented. As nonlinear coefficient
increases, the transmission coefficient decreases. The results can be used to analyze the
nonlinearity of glasses embedded with semiconductor quantum dots. 相似文献
3.
The isothermal oxidation behavior
of two kinds of alloying Ti-Al alloyTi-48Al-2Cr-2Nb and Ti-47Al-1Cr-1V-2.5Nb at 800℃ and 900℃
is investigated.Their high temperature
oxidation character and the influence of the alloying element upon the oxida－tion behavior are discussed.The
study shows that the oxidation resistance of two alloying Ti-Al alloy at 800℃ is poorer than that of
48Al.However,their oxidation properties at 900℃ are considerably improved,and the oxidation speed is much
lower than that of 48 Alalloy.At the two oxidation temperatures,Ti-48Al-2Cr-2Nb alloy
shows better oxidation resistance than that of Ti-47Al-1Cr-1V- 相似文献
4.
Yang Shuchang Wei Ping 《北京理工大学学报》1999,19(3)
Aim To study a real-time traffic flow
measurement system providing necessary statistics of traffic flow parameters for traffic
departments through measuring vehicle number, velocity and other traffic parameters.Methods
The real-time traffic flow measurement was processed through image difference method.
Because of its capability for data processing at high speed, the RISC (reduced instruction
set computer) was used to carry out real-time and practical research on the whole system. Results
Experiment devices of real-time traffic flow measurement was developed and the practical
algorithm of image processing was designed and debugged. Conclusion In
practical traffic flow measurement, the precision of measuring vehicle number is over 95%.
The system work robustly under various conditions, it can automatically cope with the
gradual and sudden changes of the environment light. 相似文献
5.
According to observed Gamma-ray
fit spectrum,Gamma-ray emission mechanism is analyzed.The upper limit of electron energy
that causes Gamma-ray emission is determined.The electrons obtain energy from synchrotron
absorption acceleration.Theconclusion is that high energy Gamma-ray is the result of
inverse-Compton scattering,and Gamma-rays with different energies radiate from different
regions in the crab nebula. 相似文献
6.
Based on the previous works of
the second author,a kind of finite difference scheme with third-order accuracy for the
homogeneous diffusion equation on non-uniform grid is presented.The proposed scheme is
unconditionally stable. 相似文献
7.
A generalized
formulation of dynamical real-space renormalization-group is suggested. The new version
replaces the single-spin flipping Glauber dynamics with the single-spin transition
dynamics so that it suits for arbitrary spin systems. 相似文献
8.
Aim To research the interpolation
algorithm of parallel connected machine tool based on stewart mechanism.Methods
The common idea of time-discrete interpolation algorithm and the inverse kinematics model
of parallel connected machine tool were used to evaluate the relation between tool motion
path and six telescopic legs and to derive one kind of interpolation algorithm.Object
oriented program design method was adopted to work out the simulation software and the
availability of the interpolation algorithm was testified by computer simulation.Results
and Conclusion Simulation results of machining process of sphere parts and
one-sheet-hyperboloid parts show that the interpolation algorithm proposed is correct and
practical, providing a new and feasible interpolation algorithm for parallel connected
machine tool. 相似文献
9.
Wang Guanglong 《北京理工大学学报》1999,19(3):12
Aim To study attitude measurement
method of flight body and attitude measurement principle of the earth magnetic field
sensor. To set up the attitude detecting maths model of the earth magnetic field sensor,
and propose the flight body attitude calculating method.Methods According
to Faraday electromagnetism induction law, i.e. when a wire loop incises the magnetic
force line of the earth magnetic field, it will bring about the induction electromotive
force, an attitude measurement system was designed based on the earth magnetic field
sensor. Results An earth magnetic field sensor and attitude measuring
system were designed, and experiment data were analyzed and processed. It was proved that
the rotating speed measurement error is 0.05r/s. Conclusion This earth
magnetic field sensor can be used to detect attitude of high-load rotating flight body. 相似文献
10.
黑洞熵公式的简单推导 总被引：4，自引：3，他引：1
Black hole is
treated as 2-D membrane. Starting from the usual state equation of thermal radiation, the
black hole entropy is technically computed, and the result that is proportional to the
area of horizon is briefly obtained. 相似文献
11.
为了研究引力不稳定性在巨分子云形成中的作用,通过计算机模拟技术建立了星系中分子云的较差自转模型.在演化中除了分子云之间的碰撞外,模型还考虑了分子云在恒星盘的背景引力场中所受的引力和分子云之间的相互自引力.其中分别考虑分子云之间的短程力(随机碰撞模型)和长程力(引力不稳定性模型).通过对计算机模拟的结果进行详细的分析和讨论,得到了以下结果:对于较差自转模型,引力不稳定性在巨分子云的聚合形成中起了关键的积极作用,它能够加速和加大分子云的成团. 相似文献
12.
首次论证了在随机引力场中，其能量─—动量张量ｔｉｋ不会变零．因此，它能够具有随机的定域值．虽然，在确定性的引力场中ｔｉｋ通常被认为是不可定域的． 相似文献
13.
通过计算机模拟技术,对短程力步长在星系中的分子云和恒星的演化中的作用做了详细的研究。结果表明：短程力步长的不同选取对于分子云和恒星的演化基本没有影响。 相似文献
14.
从尘埃等离子体的基本方程出发，采用非平衡态动力学方法，研究了尘埃粒子的引力（重力）对尘埃等离子体宏观动力学的影响，具体分析了产生凝聚效应的条件及其相关性质。结果表明，尘埃等离子体中存在一种由引力非稳定性产生的凝聚效应，从而导致局域密度增大。这种效应可能与星际介质分子云及原始恒星的形成有关，也同样会影响在实验室中等离子体加工的质量。 相似文献
15.
《科学通报(英文版)》1996,41(16):1373-1373
Classical T Tauri stars (hereinafter CTTS) are protostars formed by collapse of molecular clouds. As they evolve towards the main sequence, CCTS accrete from the circumstellar matter and contract due to self-gravitation. Mass accretion and gravitational contraction can accelerate the spin velocities of CTTS up to break-up (～300—400km·s) within 相似文献
16.
RFID中基于二分叠加的二进制防碰撞算法 总被引：2，自引：0，他引：2
提出了基于二分叠加的二进制搜索树防碰撞算法.对标签生成随机数的过程进行优化,标签每次生成随机数(O,1)的概率都相同,经过二次叠加后分布的概率就不完全相同,可从源头上降低碰撞概率,提高信道利用率.仿真结果表明,基于二分叠加的一进制搜索树防碰撞算法能减少碰撞次数,提高信道利用率. 相似文献
17.
范新民 《青海师范大学学报(自然科学版)》2006,(3):25-26,29
理想气体分子在重力场中按动量（或速度）的分布和按空间位置的分布同时受到两种对立作用的影响．热运动的无规性及分子间的碰撞是系统达到平衡态建立确定的统计分布的物理基础．通过论证可以得到以下结论;在平衡态,气体分子按速度的分布不受重力影响．重力场只引起分子数在不同高度的差异,分子速度分布的规律与重力场的存在与否无关． 相似文献
18.
王文福 《西南石油大学学报(自然科学版)》1988,10(4):160-166
本文得到了 近似下的诱生引力宇宙波函数,当诱生引力耦合常数取牛顿引力常数时,等效标度因子α的数量级为普朗克长度。在U(α、x)<0的Lorentz区,宇宙演化为Desitter宇宙。 相似文献
19.
20.
讨论了核子的“直接ＵＲＣＡ”过程发生的条件，发现在ＵＶ１４＋ＵＶⅡ态式描述的中子星物质中，核子的“直接ＵＲＣＡ”过程发生的条件是质子数分数必须超过０．１４；强调在中子昨丙“标准冷却”机制和“非标准冷却”机械可能同时存在；对几个没质量中子星的冷却过程的计算结果表明，引力 质量小于约１．６Ｍ的中子星核内应发生“标准冷却”过程，而在引力质量大于约１．６Ｍ的中子星核内可能存在２种冷却机制。 相似文献