3,844 research outputs found
Development of High Speed Gas Gun with a New Trigger System
This paper reports development of a new trigger system for a high speed gas gun and experimental results on muzzle speed ofa spherical ceramic projectile launched by a gas gun equipped with the new trigger system. A new trigger system was designed carefully using numerical simulation of interaction between a trigger system and a projectile, and deformation of the trigger system. Launching pressure levels are precisely adjustable by changing trigger system parameters. Calculated launching pressure agreed well with experimental result. It was concluded that a gas gun equipped with this new trigger system can work out more powerful as compared with a commercial air rifle
Gapless Excitation above a Domain Wall Ground State in a Flat Band Hubbard Model
We construct a set of exact ground states with a localized ferromagnetic
domain wall and with an extended spiral structure in a deformed flat-band
Hubbard model in arbitrary dimensions. We show the uniqueness of the ground
state for the half-filled lowest band in a fixed magnetization subspace. The
ground states with these structures are degenerate with all-spin-up or
all-spin-down states under the open boundary condition. We represent a spin
one-point function in terms of local electron number density, and find the
domain wall structure in our model. We show the existence of gapless
excitations above a domain wall ground state in dimensions higher than one. On
the other hand, under the periodic boundary condition, the ground state is the
all-spin-up or all-spin-down state. We show that the spin-wave excitation above
the all-spin-up or -down state has an energy gap because of the anisotropy.Comment: 26 pages, 1 figure. Typos are fixe
Gravitational level effects o optical properties of electrodeposited ZnO nanowire arrays
The coupling phenomena between the interfacial reaction rate and the microstructural/morphological variation rate must be reasonably well controlled to fabricate nano/meso- structural devices in a large scale. Otherwise, the physical property uniformity inside the device is not guaranteed to lose its superiority in the market. Free standing ZnO nanowire array was successfully synthesized on ITO/FTO substrate by template-free method in Zn(NO3)2 aqueous solutions. Two types of electrode configurations were employed in order to quantitatively examine the effect of gravitational strength on electrodeposited ZnO nanowire array: (a) a horizontal cathode surface facing downward over an anode (C/A) and (b) an anode over a cathode (A/C). The former configuration may simulate the microgravitational environment, because macroscopic natural convection is not induced. PL of ZnO nanowire array was measured. More uniform nanowires are synthesized in C/A configuration than in A/C. Seeding ZnO nanoparticles on ITO/FTO substrate can control the diameter as well as the orientation.
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Análise do complexo pecuário no nordeste paraense.
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