Stochastic resonance induced by a multiplicative periodic signal in a logistic growth model with correlated noises

The stochastic resonance (SR) phenomenon induced by a multiplicative periodic signal in a logistic growth model with correlated noises is studied by using the theory of signal-to-noise ratio (SNR) in the adiabatic limit. The expressions of the SNR are obtained. The effects of multiplicative noise intensity α and additive noise intensity D, and correlated intensity λ on the SNR are discussed respectively. It is found that the existence of a maximum in the SNR is the identifying characteristic of the SR phenomena. In comparison with the SR induced by additive periodic signal, some new features are found: (1) When SNR as a function of λ for fixed ratio of α and D, the varying of α can induce a stochastic multi-resonance, and can induce a re-entrant transition of the peaks in SNR vs λ; (2) There exhibits a doubly critical phenomenon for SNR vs D and λ, i.e., the increasing of D (or λ) can induce the critical phenomenon for SNR with respect to λ (or D); (3) The doubly stochastic resonance effect appears when α and D are simultaneously varying in SNR, i.e., the increment of one noise intensity can help the SR on another noise intensity come forth.      

Simple and universal method in designs of high-efficiency diffractive optical elements for spectrum separation and beam concentration

Diffractive optical elements(DOEs) with spectrum separation and beam concentration(SSBC) functions have important applications in solar cell systems. With the SSBC DOEs, the sunlight radiation is divided into several wave bands so as to be effectively absorbed by photovoltaic materials with different band gaps. A new method is proposed for designing high-efficiency SSBC DOEs, which is physically simple, numerically fast, and universally applicable. The SSBC DOEs are designed by the new design method, and their performances are analyzed by the Fresnel diffraction integral method.The new design method takes two advantages over the previous design method. Firstly, the optical focusing efficiency is heightened by up to 10%. Secondly, focal positions of all the designed wavelengths can be designated arbitrarily and independently. It is believed that the designed SSBC DOEs should have practical applications to solar cell systems.     

Experiments and analysis of infrared quantum cutting luminescence phenomena of Ho/Yb codoped nanophase oxyfluoride vitroceramics

The infrared quantum cutting phenomenon, which is an international hot research field, of Ho³⁺Yb³⁺: oxyfluoride vitroceramics (FOV) was studied in the present paper. It was found from the fluorescence spectroscopy experiments that the excitation spectrum of 973.0 nm fluorescence of Yb³⁺ ion is very similar to the absorption and excitation spectra of Ho³⁺ ion. It suggests that the energy transfer from Ho³⁺ ion to Yb³⁺ ion is very efficient. Then, all the possible important energy transfer passages were analyzed. It was found that the energy transfers {⁵G₄(Ho³⁺)→⁵F₅(Ho³⁺), ²F_7/2(Yb³⁺)→²F_5/2(Yb³⁺)} and {⁵F₅(Ho³⁺)→⁵I₇(Ho³⁺), ²F_7/2(Yb³⁺)→²F_5/2(Yb³⁺)} result in the effective two-photon quantum cutting 973.0 nm fluorescence of Yb³⁺ ion when ⁵G₄ or ³K₇ or the above energy level of Ho³⁺ ion are excited. Finally, the quantum efficiency η_QE,1%Yb=43.0% and η_QE,5%Yb=171.7% of two-photon quantum cutting was calculated for Ho(0.5)Yb(1):FOV and Ho(0.5)Yb(5):FOV respectively. This research would be beneficial for the enhancement of solar cell efficiency.     

中温固体氧化物燃料电池的基本性质测量

介绍了固体氧化物燃料电池的工作原理,测量了中温薄膜固体氧化物燃料电池的开路电压、放电曲线及功率曲线,并分析了电池内阻随电流密度的变化.     

低能N离子注入对蚕豆根尖细胞的诱变效应

为了研究低能N离子束的细胞遗传学效应, 以不同剂量的N离子束对蚕豆种子的种胚进行辐照, 观察分析根尖细胞的微核率、 有丝分裂指数和染色体畸变效应。 研究发现, 离子束的注入抑制了根尖细胞的有丝分裂, 干扰了正常的有丝分裂过程, 引发了染色体的结构、 行为和数目畸变; 随着离子注入剂量的增加, 微核率增加、 有丝分裂指数降低、 染色体畸变率增加。 In order to study the cytogenetic effects of low energy nitrogen ion irradiation, broad bean seed embryo was irradiated by different doses of nitrogen ions. Micronucleus rate, mitotic index and chromosome aberration in root tip cells were analyzed. The results showed that the injection of ions inhibited mitosis of root tip cells, interfered the normal process of mitosis, caused aberrations of chromosome structure, behavior and number. The frequency of micronucleus and chromosomal aberrations increased with the increasing radiation dosage, while mitotic index decreased.     

太阳能电池陷光结构辐射特性研究

本文分析了不同微结构、电池厚度对太阳能电池光损失的影响,提出了一种新的电池陷光结构。运用时域有限差分法(FDTD)仿真了该类太阳能电池陷光结构中光传输过程,获得了不同波源入射下陷光结构电池的储能特性和光捕获特性,优化设计了最佳陷光结构并分析了其光捕获性能。     

Laser in micro and nanoprocessing of diamond materials

Basic processing operations will be presented. These include diamond polishing and shaping, production of conductive pathways, micro‐ and nanostructures on the diamond surface, such as diffractive optical elements. The possibility to laser produce conductive and hollow structures in the diamond bulk, including curved elements, will be demonstrated. Finally, the techniques of laser assisted diamond CVD, that allow production of smooth or selective‐area grown films will be presented     

Application of high-resolution magic-angle spinning NMR spectroscopy to define the cell uptake of MRI contrast agents

A new method, based on proton high-resolution magic-angle spinning ((1)H HR-MAS) NMR spectroscopy, has been employed to study the cell uptake of magnetic resonance imaging contrast agents (MRI-CAs). The method was tested on human red blood cells (HRBC) and white blood cells (HWBC) by using three gadolinium complexes, widely used in diagnostics, Gd-BOPTA, Gd-DTPA, and Gd-DOTA, and the analogous complexes obtained by replacing Gd(III) with Dy(III), Nd(III), and Tb(III) (i.e., complexes isostructural to the ones of gadolinium but acting as shift agents). The method is based on the evaluation of the magnetic effects, line broadening, or induced lanthanide shift (LIS) caused by these complexes on NMR signals of intra- and extracellular water. Since magnetic effects are directly linked to permeability, this method is direct. In all the tests, these magnetic effects were detected for the extracellular water signal only, providing a direct proof that these complexes are not able to cross the cell membrane. Line broadening effects (i.e., the use of gadolinium complexes) only allow qualitative evaluations. On the contrary, LIS effects can be measured with high precision and they can be related to the concentration of the paramagnetic species in the cellular compartments. This is possible because the HR-MAS technique provides the complete elimination of bulk magnetic susceptibility (BMS) shift and the differentiation of extra- and intracellular water signals. Thus with this method, the rapid quantification of the MRI-CA amount inside and outside the cells is actually feasible.     

Wet-chemical treatment and electronic interface properties of silicon solar cell substrates

On textured n-type silicon substrates for solar cell manufacturing, the relation between light trapping behavior, structural imperfections, energetic distribution of interface state densities and interface recombination losses were investigated by applying surface sensitive techniques. The field-modulated surface photovoltage (SPV), in-situ photoluminescence (PL) measurements, total hemispherical UV-NIR-reflectance measurements and electron microscopy (SEM) were employed to yield detailed information on the influence of wet-chemical treatments on preparation induced micro-roughness and electronic properties of polished and textured silicon substrates. It was shown that isotropic as well as anisotropic etching of light trapping structures result in high surface micro-roughness and density of interface states. Removing damaged surface layers in the nm range by wet-chemical treatments, the density of these states and the related interface recombination loss can be reduced. In-situ PL measurements were applied to optimise HF-treatment times aimed at undamaged, oxide-free and hydrogen-terminated substrate surfaces as starting material for subsequent solar cell preparations.      

X-ray absorption spectroscopy under high pressures in diamond anvil cells

Abstract

Although potentially extremely important for understanding the high-pressure microscopic behaviour of materials, over the years the area of high-pressure EXAFS in particular using diamond anvil cells has proved to be technically difficult. This has significantly hampered its development. The interference of X-ray dimaction from the diamonds in the diamond anvil cell with the absorption signal has proved to be a challenging problem to tackle, restricting the use of high-pressure EXAFS to energies below about 11 key Below 11 keV however the technique is also limited due to absorption of incident X-rays by the diamonds making it virtually impossible to conduct X-ray absorption experiments below about 9keV In this paper we describe in detail the methodology for scanriirig high-pressure EXAFS in diamond anvil cells and examine the origins of the associated problems and ways of dealing with them. We also demonstrate that it is possible to extend the useful range of studied absorption edges from 7keV up to at least 30keV This brings about new opportunities for high pressure EXAFS using diamond anvil cells.