Mesoscale particles are guided and trapped in micron-sized hollow optical fibers using a 1 2 -W nearinfrared diode laser. The optical scattering force calculated using geometrical ray optics is 3 3 10 211 N for a 7-mm polystyrene sphere, and agrees well with velocity measurements of optically guided spheres in water. We have levitated a variety of particles using laser-fiber guidance, and have mixed micronsized glycerin droplets in two-beam laser-fiber traps. [S0031-9007(99)
The steering law is intended to predict the performance of cursor manipulations in user interfaces, but the law has been verified for only a few path shapes and should be verified for more if it is to be generalized. This study extends the steering law to paths with corners. Two experiments compare the movement times of negotiating paths with corners to straight paths with the same width and movement amplitude. The experimental results show a significant effect on the movement times due to the corners, extending far into the legs of the path's corner. Modeling the results using resource theory, a cognitive theory for divided attention, suggests that steering through corners is two simultaneous tasks: steering along the legs of the corner and aiming at the corner.
Laser-induced forces are used to manipulate atoms, clusters, and micron-sized particles in hollow optical fibers. Laser light (400 mW, 800 nm) is guided in a low-order grazing incidence mode in glass capillaries. The optical field in the fiber generates gradient and scattering forces which simultaneously draw particles to the center of the hollow region and push them along the fiber axis. Dielectric, semiconductor, and metal particles in the size range of 9 μm–50 nm have been guided in gas- and liquid-filled fibers. Rb atoms are guided in evacuated fiber for up to 15 cm. Used alone or in conjunction with traditional methods, laser guidance is attractive for direct-write lithography. Arbitrary surface patterns can be created under ambient conditions with potential write speeds exceeding 106 particles/s and placement accuracy approaching 50 nm (assuming a 1 W laser, 100 nm Ge particles, and fiber filled with Ar at 760 Torr). Anisotropic optical forces resulting from particle shape anisotropy act to orient particles in the fiber. In initial experiments NaCl and KI crystals in aerosol suspension have been funneled into a hollow fiber using optical forces. The crystals have been directed onto a glass surface and lines as narrow as 0.5 μm drawn. This linewidth is 30 times smaller than the inner fiber diameter and illustrates the strong focusing produced by optical forces. Atomic force microscopy images show a high degree of alignment between crystals suggesting that anisotropic optical forces act to orient the crystals during deposition.
Experience working in multidisciplinary teams is important both to prepare Computer Science (CS) students for industry and to improve their communication with teammates from disciplines other than their own. This article describes the evolution and results of collaborations among three courses: an undergraduate CS course about user interface design and implementation, an undergraduate Scientific and Technical Communication (STC) course about usability and instructions writing, and a graduate CS/Human Factors course about user-interface evaluation and usability testing. Students from all three courses work with scientists to complete the scientist-sponsored citizen science Android applications (apps). Students from the undergraduate CS and STC courses form multidisciplinary teams to design and implement apps, while the graduate students consult with the teams by evaluating and user-testing the apps. The collaboration's effectiveness was assessed using student surveys, interviews, and evaluations of student work. This article compares the collaboration within the teams and the coordination with the scientists across two years of activities in order to determine the effectiveness of course modifications. The article concludes with recommendations for improving the collaboration within teams and the coordination with clients in multidisciplinary course projects.
The three-phase model provides a framework for ergonomists to evaluate new positioning techniques and can explain their deficiencies. The model provides a means to analyze tasks and enhance interaction during positioning.
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