We present and compare two single-panel LCOS projectors using LED lamps. The 0.59" sequential-color LCOS microdisplay with integrated frame buffers can deliver 10.5 lm by a 4W red, green and blue LED. The 0.59" spatial-color LCOS microdisplay with white sub-pixels can deliver 14 lm by a 6W white LED. IntroductionLiquid-crystal-on-silicon (LCOS) microdisplay has been developed for more than 10 years [1,2]. There are three kinds of LCOS microdisplays, arranged in different manners for various applications. The first one was a monochrome and highresolution microdisplay developed in early 1990, and arranged in three-panel architectures for rear projection television (RPTV) applications [3,4]. The second one was a color-sequential microdisplay developed in late 1990, and arranged in single-panel architectures for near-to-eye and RPTV applications [5~7]. The third one was a spatial-color microdisplay developed in early 2000, and arranged in single-panel architectures for near-to-eye and mini-projector applications [8]. These three kinds of LCOS microdisplays and projectors were not designed for use with light emitting diodes (LEDs). But as the fast development of power LEDs, the prospect of using LEDs as light sources for these three LCOS projectors has been greatly increased [9~11].A Corner of 3M applied red, green and blue (RGB) LED lamps to a three-panel LCOS projector, which used three 0.61" SVGA panels, and obtained 267 lm [10]. H Zou of Philips Research replaced the scrolling prism in a single-panel sequential-color projector, which used a 1.3" progressive-scan SXGA panel, by sequential RGB LED lamps and obtained 44 lm [9]. It was expected that the output could be improved to 135 lm if the progressive-scan LCOS panel was replaced by a frame-loading one. H S Lo of ITRI proposed optical designs for very compact mini-projectors using 0.38" color-filter LCOS panels [11]. But the output was low due to the light absorption by RGB color filters.In this paper, we present our works on single-panel spatial-color and sequential-color LCOS projectors using LED lamps. We added white sub-pixels to the color-filter LCOS panel to increase the panel reflectivity from typically 20% to 32%. The output of the spatial-color LCOS projector was correspondingly improved. We integrated frame buffers to the sequential-color LCOS panel to eliminate the frame loading time. As a result, the optical efficiency of the sequential-color LCOS projector was greatly improved. Moreover, the sequential-color LCOS projector had enough time budgets for RGB and white (RGBW) color sequence for more optical output. Spatial-Color LCOS ProjectorThe color-filter LCOS microdisplays were designed to be used with low-cost halogen lamps for low-cost video projectors. Figure 1 shows a palm-size spatial-color LCOS projector using a 50W halogen lamp in a MR11 package. The projector could produce 20 lumen output from a 0.47" VGA panel with a color gamut of 35% NTSC level, which was limited by low color temperature of the halogen lamp. (a) (b) Figure 1 (a) Spatial-co...

This paper describes the testing of wind turbine blades with tubercles in two different ways: outdoor testing and flow visualization. In the outdoor testing, the tubercle pitch was varied for turbine blade lengths of 30 cm, 40 cm, and 50 cm. The pitch-to-length ratio of approximately 1/10 to 1/16 produced the most power output. In flow visualization, both tubercle pitch and amplitude were varied. Vortices created behind the tubercles were shown to increase lift by minimizing flow separation.

The present study explores the numerical simulation of airfoil self-noise using Computational Fluid Dynamics. Direct Noise Computations (DNC) are conducted for a NACA0012 airfoil set at near-zero incidences (𝜶 = 0˚, 𝜶 = 0.5˚) within a low Reynolds number flow (Re = 6.6×10 4 ). The DNC rely on 2D, compressible, wall-resolved Large Eddy Simulations, which allow capturing both the unsteady aerodynamic flow around the airfoil and the subsequent acoustic emission at its trailing edge. The numerical results are favorably compared against experimental data involving a similar configuration (airfoil type, Reynolds number, flow incidence). Results reveal that the primary self-noise tone and its upper harmonics are accurately predicted, for both angles of attack. Some harmonic tones are found to emerge only when the incidence is not nil, being "silenced" when the angle of attack is zero. Special focus is put on the tonal noise generation mechanisms to occur in each flow condition. It is inferred that two distinct mechanisms co-exist, namely, a vortex-shedding and a convective boundary layer instability. The latter is believed to relate to a classical feedback loop phenomenon, whose approximate model is found to match the current results.