Papers by Keyword: Reflectivity

Abstract: In order to develop flexible absorption fabric and study the effects of specifications on absorption properties, two-layer laminated fabrics were designed according to thickness matching and impedance matching. Stainless steel core-spun yarn fabrics were used as first layer which easily realized matching to the free space, Ni-Fe fiber consisted of second layer because its strong dielectric loss and magnetic loss. The reflectivity of fabrics were measured by the means of "arch testing method" in the range from 2~18 GHz. The results showed that the reflectivities of laminated fabrics can below-20 dB and the bandwidth <-10dB can reach 3.88 GHz with the change of fabric specifications.

Abstract: In order to develop flexible absorbing fabric, three kinds of 58.3tex Ni-Fe fiber blended yarn which Ni-Fe fiber content was 8.34%, 11.11% and 13.89% were spun successfully and fabricated to different kinds of fabrics according to mental fiber property and electromagnetic spreading regulation. The reflectivity of fabrics were measured by the means of "arch testing method" in the range of 2-18 GHz with the change of fabric specifications. The results showed that the reflectivity of laminated fabrics were better than designed knitted fabrics and woven fabrics, revealed that the nickel iron fiber content and fabric specifications had significant effects on absorbing property.

Abstract: Because the reflectivity of astaxanthin vary in different bands (mainly 400nm-600nm), so we use the visible-near infrared spectra technique to irradiate the salmon. Because in daily life, people grade the salmon flesh with a color card. In this paper, we first use principal component analysis to reduce the dimensionality of the spectral data of salmon, then use linear discriminant analysis method, least squares support vector machine classification method to distinguish the flesh quality. The correct classification rates are 60%and73.3%. The results show that we can use visible – near infrared spectra to distinguish the quality of the salmon which doesn’t be dissected.

Abstract: This work presents study of both the antireflection coatings on silicon solar cells and surface texture of silicon solar cell, with the aim to prepare high quality Si solar cells. Surface texturing, either in combination with an anti-reflection coating or by itself, can be used to minimize reflection, but the large reflection loss can be reduced significantly via a suitable anti-reflecting coatings. Significant improvement of the short circuit current after anti-reflecting coatings was observed. It is found that the currentvoltage characteristic with a double-layer anti-reflecting coatings is better than that with a single-layer anti-reflecting coatings. Depositing a multilayer on the textured surface reduces the large reflection loss significantly. The short circuit current of silicon solar cells has significant improvement after depositing anti-reflecting coatings on textured surface silicon, and it increases the efficiency of the Si solar cells.

Abstract: Thin-film anti-reflecting coatings can greatly reduce the optical loss by making use of phase changes, and the reflectivity depends on the refractive index of materials. TiO₂ZnS and Si₃N₄ coatings are suitable for using as single layer anti-reflecting coating on bare silicon surface, while the MgF₂/ZnS and SiO₂/TiO₂ double-layer anti-reflecting coating result in a minimum reflectance lower than 0.5% over broad spectral regions, with an average reflectance of approximately 2.25% between 400 and 1100 nm on the non-textured Si substrate. The short circuit current of silicon solar cells has significant improvement after depositing anti-reflecting coatings, and it increases the efficiency of the Si solar cells.

Abstract: Based on transfer matrix method (TMM), the model and calculation of 3-D Photonic Crystal with Face-Centered-Cubic (FCC) Structure are presented. The microsphere size, the crystal stack thickness and the incident angle have an influence on optical properties of 3-D Photonic Crystal. With the microsphere size increasing, the wavelength corresponding to the positions of PBG becomes larger causing structural color changing from blue to red. The reflectivity becomes higher and PBG is narrower when the crystal stack thickness increases. With the incident angle becoming larger, the reflectivity does not change significantly, while the wavelength corresponding to the positions of PBG becomes shorter causing structural color changing from red to blue.

Abstract: Pyramidal surface is commonly used as an antireflection structure. The weighted reflectance averaged by the AM 1.5 G spectrum is about 14%. In the photovoltaic field, lowering the surface reflectivity is an important approach to improve the conversion efficiency. Black silicon surface with low reflectivity is benefit of solar cells. But conversion efficiency of black silicon solar cell is still low due to the severe surface recombination. In this paper, shallower black silicon layer was formed on the pyramidal surface. For the sample etched 1 min, the weighted reflectance is only 13.20%, and the pyramidal one is 14.10%. The layer would not deteriorate the material. Lifetime of the substrates after high temperature phosphorous diffusion is 13.35 μs higher than the pyramidal one. The mean sheet resistance is nearly the same between the pyramidal surface and the etched pyramidal surface.

Abstract: According to the law of light propagation, this thesis analyzed that added reflective particles in the material can improve materials reflectivity properties. Established the model by the optical design software Light Tools to simulate, predicted the law of materials reflectivity properties changing with particle parameters. Chosen TiO₂ as the reflective particles to test, the result shown that when the TiO₂ content reached a certain proportion, the reflectivity and diffuse reflection of diffuse reflection composites can reach 91% and 88% respectively, the illumination uniformity can reach 60%.

Abstract: As a renewable, clear and inexhaustible energy, solar energy receives much more attention and has partly substituted traditional energies in many fields. Multi-crystalline silicon plays an important role for its low cost, abundant reserves and excellent photoelectric conversion in solar cells. Mixed acid etching is an effectively method to texture the morphology on the surface of mc-Si, While stochastic etching between silicon and acids results in irregular texturing and high reflectivity. In this paper, ultrasonic standing wave is introduced into acid solution, which aid wet etching to texture on the surface of mc-Si by controlling distribution of atoms of acids. Scanning electron microscope experiment shows that the morphology on the surface of mc-Si textured by this method is similar to that of mono-crystalline silicon. And the average reflectivity is 8%, much lower than mixed acid etching.

Abstract: The reflectance and transmittance spectra for magnesium aluminates spinel single crystals MgO•nAl2O3 and ceramics in the IR spectral range were measured to investigate the nature of vibration modes of constituent ions and incorporated hydrogen. Besides of the earlier observed bands at 545, 710, and 835 cm-1 we registered also two bands 1440 and 1670 cm-1 in single crystals grown by different methods and in spinel optical ceramics. The existence of these bands was supported by measurements of non-stoichiometric spinel crystals and crystals doped with transition metals. The variation of intensity of registered bands in spinel of stoichiometric and non-stoichiometric compositions and spinel ceramics was interpreted in terms of vibration modes of divalent and trivalent cations in different coordination, particularky, at the spatially correlated anti-site defects.