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9 Feb 2004

Volume 84, Issue 6, pp. 837-1024

Issue Cover Spotlight Figure

Appl. Phys. Lett. 84, 975 (2004); http://dx.doi.org/10.1063/1.1646453 (3 pages)

Xiang Yang Kong and Zhong Lin Wang
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Effect of thermal variations on the Knudsen forces in the transitional regime

A. L. Lereu, A. Passian, R. J. Warmack, T. L. Ferrell, and T. Thundat

Appl. Phys. Lett. 84, 1013 (2004); http://dx.doi.org/10.1063/1.1644916 (3 pages) | Cited 7 times

Online Publication Date: 4 February 2004

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When objects are maintained at different temperatures and separated by distances of the order of the mean free path of the surrounding host gas molecules, gas kinetic forces called Knudsen forces may be involved. The understanding of this effect may result in some improvements in microelectromechanical devices and measurement systems. We present the thermal dependence of these forces in the transitional regime for different gases. In this mode, the Knudsen effect can be significant and, therefore, become a problem in microscale devices. For this study, a silicon microcantilever, mounted close to a substrate, is used and changes in temperature are observed by measuring bending of the microcantilever. © 2004 American Institute of Physics.
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47.45.Dt Free molecular flows
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices

Simulation of rapid startup in microwave magnetrons with azimuthally varying axial magnetic fields

M. C. Jones, V. B. Neculaes, W. White, Y. Y. Lau, and R. M. Gilgenbach

Appl. Phys. Lett. 84, 1016 (2004); http://dx.doi.org/10.1063/1.1646225 (3 pages) | Cited 18 times

Online Publication Date: 4 February 2004

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A method is proposed whereby the startup of a magnetron may be hastened. For a N-cavity magnetron operating in the pi mode, the formation of the N/2 electron spokes is much more rapid when an azimuthally varying axial magnetic field of N/2 periodicity is employed. Electromagnetic particle-in-cell code simulations are presented that show electron prebunching by the azimuthally varying axial magnetic field, long before the pi mode is excited. © 2004 American Institute of Physics.
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84.40.Fe Microwave tubes (e.g., klystrons, magnetrons, traveling-wave, backward-wave tubes, etc.)

Reversing granular flow on a vibratory conveyor

R. Grochowski, P. Walzel, M. Rouijaa, C. A. Kruelle, and I. Rehberg

Appl. Phys. Lett. 84, 1019 (2004); http://dx.doi.org/10.1063/1.1646219 (3 pages) | Cited 9 times

Online Publication Date: 4 February 2004

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Experimental results are presented for the transport properties of granular materials on a vibratory conveyor. For circular oscillations of the shaking trough nonmonotonous dependence of the transport velocity on the normalized acceleration Γ is observed. Two maxima are separated by a regime where the granular flow is much slower and, in a certain driving range, even reverses its direction. Similar behavior is found for a single solid body with a low coefficient of restitution, whereas an individual glass bead of 1 mm diameter is propagated in the same direction for all accelerations. © 2004 American Institute of Physics.
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45.70.Mg Granular flow: mixing, segregation and stratification
81.05.Rm Porous materials; granular materials
46.40.-f Vibrations and mechanical waves

Carbon nanotube field emitter arrays having an electron beam focusing structure

Jun Hee Choi, Andrei R. Zoulkarneev, Yong Wan Jin, Young Jun Park, Deuk Seok Chung, Byung Kwon Song, In Taek Han, Hang Woo Lee, Sang Hyun Park, Ho Suk Kang, Ha Jong Kim, Jung Woo Kim, Jae Eun Jung, Jong Min Kim, Hong Gu Baek, et al.

Appl. Phys. Lett. 84, 1022 (2004); http://dx.doi.org/10.1063/1.1645315 (3 pages) | Cited 20 times

Online Publication Date: 4 February 2004

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An electron beam focusing structure was incorporated into the gated field emitter arrays where the emitters were screen-printed carbon nanotubes. The focusing structure was comprised of 8-μm-thick bulky SiOx focus gate insulator and Cr focus gate, and exhibited negligible leakage between the gate and the focus gate. In current–voltage measurements, it is found that the anode current strongly depends on both the focus gate and the anode bias voltages. Electron beams were focused well at the anode with a slight overfocusing effect, which is due to the wide electron beam divergence from carbon nanotubes. A new focusing structure based on the simulation is proposed to overcome the overfocusing. © 2004 American Institute of Physics.
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85.45.Db Field emitters and arrays, cold electron emitters
78.67.Ch Nanotubes
41.85.Lc Particle beam focusing and bending magnets, wiggler magnets, and quadrupoles
85.35.Kt Nanotube devices
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