Abstract:The goal of this presented study was to determine the optimum parameters of secondary optical elements (SOEs) for concentrated photovoltaic (CPV) units with flat Fresnel lenses. Three types of SOEs are under consideration in the design process, including kaleidoscope with equal optical path design (KOD), kaleidoscope with flat top surface (KFTS), and open-truncated tetrahedral pyramid with specular walls (SP). The function of using a SOE with a Fresnel lens in a CPV unit is to achieve high optical efficiency, low sensitivity to the sun tracking error, and improved uniformity of irradiance distribution on the solar cell. Ray tracing technique was developed to simulate the optical characteristics of the CPV unit with various design parameters of each type of SOE. Finally, an optimum KOD-type SOE was determined by parametric design process. The resulting optical performance of the CPV unit with the optimum SOE was evaluated in both single-wavelength and broadband simulation of solar spectrum.
In this paper, we demonstrate virtual channels defined by "walls" of magnetic fields, which can be used to construct a dynamically reconfigurable network of flowing magnetic beads. Magnetized by an external magnet, nickel structures generate magnetic fields that can 'hold' and, therefore, guide/trap magnetic particles. In this study, we exhibit S-and Y-shaped virtual channels which steer magnetic beads smoothly. Comparison on the relation of the bead's speed versus magnetic flux density between channels with different radii of bending curvature or with different widths is also shown. Lastly, a switchable channel implemented with a bistable mechanism is used to demonstrate the passing and blocking of a bead, proving the feasibility of a dynamically reconfigurable network.
The development of Micro-Electro-Mechanical Systems (MEMS) advances the success of microfabricated devices, and microfabricated devices offer many specific platforms that can integrate a laboratory on a chip and manage micro biochemical reaction analysis. Nevertheless, most microfabricated devices, especially in biochip design, are depending on semi-conductor or LIGA process so that the configuration of devices is complex and money-consumed. Furthermore, miniaturization in nano-scale isn't always sig nificant in bio-medical reactions.
This work demonstrates the feasibility of a novel microfluidic system with virtual channels formed by 'walls' of magnetic fields, including collecting channels, transporting channels and function channels. The channels are defined by the nickel patterns. With its own ferromagnetism, nickel can be magnetized using an external magnetic field; the nickel structures then generate magnetic fields that can either guide or trap magnetic beads. A glass substrate is sandwiched between the liquid containing magnetic beads and the chip with nickel structures, preventing the liquid from directly contacting the nickel. In this work, collecting channels, transporting channels and function channels are displayed sequentially. In the collecting channel portion, channels with different shapes are compared. Next, in the transporting channel portion we demonstrate I-, S-and Y-shaped channels can steer magnetic beads smoothly. Finally, in the function channel portion, a switchable trapping channel implemented with a bistable mechanism performs the passing and blocking of a magnetic bead.
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