共查询到20条相似文献,搜索用时 15 毫秒
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Junfei Wu Qing Li Jianping Liu Chao Xue Shanqing Yang Chenggang Shao Liangcheng Tu Zhongkun Hu Jun Luo 《Annalen der Physik》2019,531(5)
The Newtonian gravitational constant G, which is one of the earliest fundamental constants introduced by human beings, plays an important role in cosmology, astrophysics, geophysics, metrology, and so on. In spite of the measurement of G having a relative longer history and more than 200 measurement results having been obtained during the past 200 years, G still remains the least precisely known among all fundamental physical constants up to now. Over the past three decades, many experimental physicists devoted themselves to the G measurement with various methods and resulted in a dozen precise values of G. However, the determined results are still in poor agreement with each other. A brief overview of the significance of the gravitational constant G is given herein, followed by an introduction into the history of G measurement. A summary of the five latest precise measurements performed during the past few years is presented. Finally, an outlook of the future development of G measurement is provided. 相似文献
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Based on a conventional torsion pendulum,we develop a forced oscillation viscometer with ultra-high viscosity sensitivity of 2×10~(-7)Pa·s working at frequencies near the resonance.The viscosity is achieved by exploiting the phase lag for the angle displacement behind the torque,instead of the resonant curve,i.e.,the variation of angle displacement amplitude versus frequency.The general formula for the measurement of the visco-elasticit.y of complex fluids is also presented.With such precision it is easy to measure tiny change in viscosity result from circumstantial influences.Deionized water and two kinds of NaCl aqueous solutions are chosen to demonstrate the performance of our home-made torsion pendulum-based viscometer. 相似文献
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《Journal of Magnetic Resonance, Series A》1995,112(2):139-143
The constant-relaxation-period (CREPE) method for spin-lattice (T1) relaxation measurement presented here offers a significant improvement over other methods currently in use. The CREPE approach involves the measurement of both the initial and the final magnetizations flanking a constant relaxation period; the relaxation rates can be extracted from the data by linear regression without the necessity of additional parameters to correct for off-resonance effects or errors in pulse-width settings. Computer simulations used to compare the accuracy of T1 measurements made by the new method with those by the fast inversion-recovery (FIR) approach (generally considered to be the best general method for T1 measurements) showed that the CREPE method provides about a twofold reduction in errors over a wide range of signal-to-noise in the input data. Experimental data collected by the two approaches showed that the CREPE method provides the same precision in T1 values as the FIR method with one-fourth the data-collection time. 相似文献
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扭摆法是测量物体转动惯量的有效方法,减小误差是该实验的关键问题。本文分析了扭摆法测物体转动惯量时空气阻力引起的误差,并给出了加载重物之后扭转系数的变化及其对测量误差的影响。结果对测量精度的提高、实验方法选择和仪器研制等方面具有重要的实际意义。 相似文献
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We discuss the possible effects of gravitational-wave stochastic background on the performance of a pendulum device such those used in precise measurements of the gravitational constant G. The variation Q of the quality factor Q of the pendulum induced by the stochastic background is evaluated, by using as numerical input the results obtained in gravitational antennas experiments. It is found |q|10–10, completely negligible with respect to a typical value Q105. 相似文献
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Improvement of Test of Solar Neutrino Coherent Scattering with Torsion Pendulum 总被引:2,自引:0,他引:2 下载免费PDF全文
A torsion pendulum containing two sapphire crystals and two lead rings is used to test Weber's theory of enhanced solar neutrino coherent scattering. Our experiment gives a null result for the diurnal force with a noise level of 3.8 × 10^-14 N, which is 526 times smaller than the predicted value of Weber's theory, and directly rules out Weber's theory and the experimental result. This experiment also reveals a test of the weak equivalence principle with η (Al2O3, Pb) (0.8 ± 3.1) × 10^-10 for masses falling toward the Sun. 相似文献
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单摆当摆角0<5°时,其振动周期T=2π,其中g为摆所在位置地球表面附近处的重力加速度,因为对地球而言,表面各处重力加速度值变化不大可近似为常量即g=9.8m/s2,故常说单摆的周期只取决于单摆自身的性质,但是应当指出的是,只有当单摆的悬挂点相对地球静止时,上述结论才是正确的.如果出现较为复杂的情形,则上式中的g就不再是重力加速度g,而应理解为"表观重力加速度 相似文献
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Durmu??A.?Demir 《Foundations of Physics》2009,39(12):1407-1425
We develop a geometro-dynamical approach to the cosmological constant problem (CCP) by invoking a geometry induced by the
energy-momentum tensor of vacuum, matter and radiation. The construction, which utilizes the dual role of the metric tensor
that it structures both the spacetime manifold and energy-momentum tensor of the vacuum, gives rise to a framework in which
the vacuum energy induced by matter and radiation, instead of gravitating, facilitates the generation of the gravitational
constant. The non-vacuum sources comprising matter and radiation gravitate normally. At the level of classical gravitation,
the mechanism deadens the CCP yet quantum gravitational effects, if strong, can keep it existent. 相似文献
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Ragab M. Gad 《International Journal of Theoretical Physics》2014,53(1):307-319
In this paper, we find the teleparallel version of the cylindrically symmetric stiff fluid space-time. The expressions for torsion vector and torsion axial-vector are obtained. We show that the value of torsion axial-vector depends on the choice of tetrad fields. Furthermore, we calculate the energy and momentum densities and show that these values do not depend on the choice of tetrad fields. Finally, we find the equation determining trajectory and spin precession of a Dirac equation in the space-time under consideration and show that the corresponding Hamiltonian depends on the choice of tetrad fields. 相似文献
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扭摆法测物体转动惯量的不确定度分析 总被引:1,自引:0,他引:1
扭摆法是测量物体转动惯量的有效方法,其不确定度分析是关键.本文推导了扭摆法测物体转动惯量准确的不确定度传递公式,得到各直接测量量及其不确定度对转动惯量不确定度的影响.并进行了算例分析.结果表明,扭摆法比三线摆测得物体的转动惯量的误差以及不确定度要小很多.这对实验方法的选择和仪器的研制具有重要的实际意义. 相似文献
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In this paper we investigate the holographic dark energy scenario in higher derivative gravity with a varying gravitational constant. We introduce a kind of energy density from higher derivative gravity which has role of the same as holographic dark energy. We obtain the exact differential equation , which determine the evolution of the dark energy density based on varying gravitational constant G. We also find out a cosmological application of our work by evaluating a relation for the equation of state of dark energy for low redshifts containing varying G correction. 相似文献
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The density inhomogeneity of a glass pendulum is determined by an optical interference method. The relative variations of the densities over a volume with sizes of 5 × 5×5 mm^3 are (0.64 ± 0.97) × 10^-5 and (0.99 ± 0.92) × 10^-5 for the K9 glass and silica glass pendulum, respectively. These variations of densities contributing to the relative uncertainties of the Newtonian gravitational constant G are 0.20 ppm and 0.21 ppm in our experiment on measurement of G. 相似文献
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Using the linearization of Einstein's equations for weak gravitational fields, a specific model of gravito-magnetofluid is elaborated. The study of wave formation and propagation in such a medium is necessarily connected to the existence of the cosmological constant. 相似文献
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Csaba Csáki Joshua Erlich Christophe Grojean 《General Relativity and Gravitation》2001,33(11):1921-1927
Brane worlds are theories with extra spatial dimensions in which ordinary matter is localized on a (3+1) dimensional submanifold. Such theories could have interesting consequences for particle physics and gravitational physics. In this essay we concentrate on the cosmological constant (CC) problem in the context of brane worlds. We show how extra-dimensional scenarios may violate Lorentz invariance in the gravity sector of the effective 4D theory, while particle physics remains unaffected. In such theories the usual no-go theorems for adjustment of the CC do not apply, and we indicate a possible explanation of the smallness of the CC. Lorentz violating effects would manifest themselves in gravitational waves travelling with a speed different from light, which can be searched for in gravitational wave experiments. 相似文献