RESUMO
We introduce a genetic-type tree search (GTTS) algorithm combined with unsupervised clustering for the automatic inverse design of high-performance metasurfaces. With the proposed method, we realize highly directive beam-steering metasurfaces via the cooptimization of the amplitude and phase. In comparison with previous topology optimization approaches, the developed GTTS algorithm optimizes the organization of subwavelength nanoantennas and, thus, is applicable to the design of both passive and active metasurfaces. The optimized beam-steering metasurface specifically exhibits a nearly constant directivity when the steering angle varies from 5° to 30°. Furthermore, the optimized nonintuitive reflectance and phase profiles assist in achieving highly directive beam steering when the phase modulation range is <180°, which was previously challenging. Our approach can diminish the requirements of scattering light properties with substantially enhanced angular resolution of beam-steering metasurfaces, which enables the realization of high-performance metasurfaces that will be promising for a wide range of advanced nanophotonic applications.
Assuntos
ÁrvoresRESUMO
This study experimentally and numerically examines the correlated color temperature (CCT) stability issue for hybrid warm white high-voltage light-emitting diodes (HV-LEDs) by using a current compensation method. This method could efficiently maintain the CCT stability factor at approximately 1.0 and yield greater color uniformity with Δu'v' values ranging from 0.017 to 0.003 in CIE 1976 chromaticity coordinates. The simulation results show that the red chip intensity drop is the primary cause of CCT instability in the hybrid warm white system when the temperature increases. Therefore, Furthermore, results indicate that the relative lumen drop improves from 21% to 15% by using a current compensation method.
RESUMO
The high luminous efficiency and superior uniformity of angular-dependent correlated color temperature (CCT) white light-emitting diodes have been investigated by ZrO2 nano-particles in a remote phosphor structure. By adding ZrO2 nano-particles with silicone onto the surface of the phosphor layer, the capability of light scattering could be enhanced. In particular, the intensity of blue light at large angles was increased and the CCT deviations could be reduced. Besides, the luminous flux was improved due to the ZrO2 nano-particles with silicone providing a suitable refractive index between air and phosphor layers. This novel structure reduces angular-dependent CCT deviations from 1000 to 420 K in the range of -70° to 70°. Moreover, the enhancement of lumen flux was increased by 2.25% at a driving current 120 mA, compared to a conventional remote phosphor structure without ZrO2 nano-particles. Consequently, the ZrO2 nano-particles in a remote phosphor structure could not only improve the uniformity of lighting but also increase the light output.
RESUMO
Adhesions are unavoidable consequences of surgery and other trauma. How to prevent the adhesions remains a big issue in healthcare system. The objective of this study is to test the efficacy of polycaprolactone (PCL) films as physical barriers in reducing postoperative intra-abdominal adhesions in the rat cecum-abdominal wall model. PCL is quite cheap compared with the agents recently used in the market. The fabrication method is also very easy to perform. Scanning electron microscope (SEM) showed multiple pores over upper and bottom surfaces but too small to permit cells to migrate from one surface onto another surface. Those pores were proven to be not interconnected. The PCL film did not show any evidence of cytotoxic effects as it did not induce any significant increase in cytoplasmic lactate dehydrogenase release from the NIH3T3 cells that it came in contact with. In animal studies, the PCL films led to fewer adhesions than Seprafilm in rat adhesion model. PCL films were efficacious in reducing postoperative intra-abdominal adhesion formation in rat cecum-abdominal wall models.