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Technologies intergrated , for young kids through COVID-19: Toward long term on the web educating.
Permanent magnet multipoles (PMMs) are widely used in accelerators to either focus particle beams or confine plasma in ion sources. The real magnetic field created by PMMs is calculated by magnetic field simulation software and then used in particle tracking codes by means of a three dimensional magnetic field map. A common alternative is to use the so-called "hard-edge" model, which gives an approximation of the magnetic field inside the PMM assuming a null fringe field. This work proposes an investigation of the PMM fringe field properties. An analytical model of the PMM magnetic field is developed using the Fourier multipole expansion. A general axial potential function with a unique parameter λ, able to reproduce the actual PMM magnetic field (including its two fringe fields) with an explicit dependence on the PMM length, is proposed. An analytical first order model including the axial fringe field is derived. This simple model complies with the Maxwell equations [curl(B) = 0 and div(B) = 0] and can replace advantageously the "hard-edge" model when fast analytical calculations are required. The higher order analytical multiple expansion model quality is assessed by means of χ2 estimators. The general dependence of the potential function parameter λ is given as a function of the PMM geometry for quadrupole, hexapole, and multipole, allowing one to use the developed model in simulation programs where the multipole geometry is an input parameter.Optimal wheel alignment improves fuel efficiency, safety, and driver comfort. An explicit formula for determining kingpin parameters, namely, caster and kingpin inclination angle (KIA), in four-wheel alignment is lacking. Currently, caster and KIA values are estimated by repetitive large-scale computing with a mathematical model aimed at obtaining values infinitely close to real solutions. In this study, a four-wheel aligner calibration device was used to collect large amounts of data for a variety of four-wheel aligner measurements with a short data interval. The data were subjected to the local fractal dimension analysis with fractional dimension-based blanket technology (BT) to optimize the number of measurement points. Dramatic changes in data were attributable to local areas with a large fractional number dimension. Appropriate increase in the number of calibration measuring points in areas with a relatively low fractional number dimension can reduce the overall quantity of measuring points. The results provide a scientific basis for the development of alignment calibration standards and demonstrate that these parameters can be assessed based on a small number of measurements. Our BT-based methodology can facilitate factory inspection and performance testing of four-wheel aligners and may improve the accuracy of wheel positioning parameter assessments.We present a long-working-distance objective lens with numerical apertures NA = 0.4 for single-atom experiments. The objective lens is assembled entirely by the commercial on-catalog Φ1″ singlets. The objective can correct the spherical aberrations due to the standard flat vacuum glass windows with various thicknesses. The typical working distance is 18.2 mm at the design wavelength of 852 nm with a 5-mm thick silica window. In addition, the objective can also be optimized to work at the diffraction limit at a single wavelength in the entire visible and near infrared regions by slightly tuning the distance between the first two lenses. The diffraction limited field of view is 0.61 mm, and the spatial resolution is 1.3 μm at the design wavelength. The performances are simulated by using the commercial ray-tracing software and confirmed by imaging the resolution chart and a 1.18 μm pinhole. The objective can be used for trapping and manipulating single atoms of various species.A home-made vacuum ultraviolet photoionization time-of-flight mass spectrometer has been developed and coupled to an atmospheric simulation chamber operated at atmospheric pressure and to a fast flow tube at low pressure (1-10 Torr). Gas sampling from the simulation chamber is realized directly via a capillary effusive beam, and sampling from the flow tube is via a continuous molecular beam inlet. Zelavespib cost Both devices are connected simultaneously to the ionization chamber of the mass spectrometer and can be switched in-between within minutes to study gas-phase radical reactions of atmospheric interest in a large range of reaction conditions and reaction times (from milliseconds in the flow tube to hours in the simulation chamber). A cage-shaped photoionization source combined with a commercial 10.6 eV krypton lamp has been developed to provide a high ion collection efficiency along the long light path in the cage. This way, a multiplexed detection with high sensitivity down to the sub-parts per billion volume concentration range, e.g., a limit of detection of 0.3 ppbv with an accumulation time of 60 s for benzene and 1.3 ppbv for the methyl radical, is obtained. The performance and suitability of the setup are illustrated by the study of the chlorine-initiated oxidation reaction of toluene in the atmospheric simulation chamber and in the fast flow tube. Stable products and reactive intermediates have been well-determined and their reaction dynamics are discussed.An experimental study of the semi-cylindrical self-magnetic insulated diode with No. 25 transformer oil and methyl silicone oil filled into stainless steel metal foam as anode discharging materials is carried out for the first time. The results show that the lifetime of this type of ion beam diode is about 3000 discharges, significantly higher than that of the conventional solid-film ion beam diode, which is about 400 discharges. Meanwhile, the ion beam current density of transformer oil and methyl silicone oil is higher than the polyethylene film, and the maximum ion beam current density of No. 25 transformer oil and methyl silicone oil is 330 A/cm2 and 250 A/cm2, respectively. In addition, the ion beam current density of No. 25 transformer oil and methyl silicone oil is more stable than that of the polyethylene film.
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