23,774 research outputs found

    Review of available synchronization and time distribution techniques

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    The methods of synchronizing precision clocks will be reviewed placing particular attention to the simpler techniques, their accuracies, and the approximate cost of equipment. The more exotic methods of synchronization are discussed in lesser detail. The synchronization techniques that will be covered will include satellite dissemination, communication and navigation transmissions via VLF, LF, HF, UHF and microwave as well as commercial and armed forces television. Portable clock trips will also be discussed

    Radial Velocity along the Voyager 1 Trajectory: The Effect of Solar Cycle

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    As Voyager 1 and Voyager 2 are approaching the heliopause (HP)—the boundary between the solar wind (SW) and the local interstellar medium (LISM)—we expect new, unknown features of the heliospheric interface to be revealed. A seeming puzzle reported recently by Krimigis et al. concerns the unusually low, even negative, radial velocity components derived from the energetic ion distribution. Steady-state plasma models of the inner heliosheath (IHS) show that the radial velocity should not be equal to zero even at the surface of the HP. Here we demonstrate that the velocity distributions observed by Voyager 1 are consistent with time-dependent simulations of the SW-LISM interaction. In this Letter, we analyze the results from a numerical model of the large-scale heliosphere that includes solar cycle effects. Our simulations show that prolonged periods of low to negative radial velocity can exist in the IHS at substantial distances from the HP. It is also shown that Voyager 1 was more likely to observe such regions than Voyager 2

    A computational scheme to evaluate Hamaker constants of molecules with practical size and anisotropy

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    We propose a computational scheme to evaluate Hamaker constants, AA, of molecules with practical sizes and anisotropies. Upon the increasing feasibility of diffusion Monte Carlo (DMC) methods to evaluate binding curves for such molecules to extract the constants, we discussed how to treat the averaging over anisotropy and how to correct the bias due to the non-additivity. We have developed a computational procedure for dealing with the anisotropy and reducing statistical errors and biases in DMC valuations, based on possible validations on predicted AA. We applied the scheme to cyclohexasilane molecule, Si6_6H12_{12}, used in 'printed electronics' fabrications, getting A∼105±2A \sim 105 \pm 2 [zJ], being in plausible range supported even by other possible extrapolations. The scheme provided here would open a way to use handy {\it ab initio} evaluations to predict wettabilities as in the form of materials informatics over broader molecules.Comment: The manuscript was revised according to review comment

    Working Group 5: Measurements technology and active experiments

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    Technology issues identified by working groups 5 are listed. (1) New instruments are needed to upgrade the ability to measure plasma properties in space. (2) Facilities should be developed for conducting a broad range of plasma experiments in space. (3) The ability to predict plasma weather within magnetospheres should be improved and a capability to modify plasma weather developed. (4) Methods of control of plasma spacecraft and spacecraft plasma interference should be upgraded. (5) The space station laboratory facilities should be designed with attention to problems of flexibility to allow for future growth. These issues are discussed

    Confirmation of Parity Violation in the Gamma Decay of 180Hfm^{180}Hf^{m}

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    This paper reports measurements using the technique of On Line Nuclear Orientation (OLNO) which reexamine the gamma decay of isomeric 180^{\rm 180}Hfm^{\rm m} and specifically the 501 keV 8−^{\rm -} -- 6+^{\rm +} transition. The irregular admixture of E2 to M2/E3 multipolarity in this transition, deduced from the forward-backward asymmetry of its angular distribution, has for decades stood as the prime evidence for parity mixing in nuclear states. The experiment, based on ion implantation of the newly developed mass-separated 180^{\rm 180}Hfm^{\rm m} beam at ISOLDE, CERN into an iron foil maintained at millikelvin temperatures, produces higher degrees of polarization than were achieved in previous studies of this system. The value found for the E2/M2 mixing ratio, ϵ\epsilon = -0.0324(16)(17), is in close agreement with the previous published average value ϵ\epsilon = - 0.030(2), in full confirmation of the presence of the irregular E2 admixture in the 501 keV transition. The temperature dependence of the forward-backward asymmetry has been measured over a more extended range of nuclear polarization than previously possible, giving further evidence for parity mixing of the 8−^{\rm -} and 8+^{\rm +} levels and the deduced E2/M2 mixing ratio.Comment: 28 pages, 9 figures, accepted for publication in Physical Review
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