高汇聚比太阳能聚光特性分析综合实验设计

太阳能模拟器是开展太阳能光热利用实验研究和实验教学的重要平台。该文探讨了采用朗伯靶和CCD相机组合的能流密度间接测量实验,通过多类型组合和调控方式研究其高汇聚比聚光集热特性,结果发现,聚焦光斑能流密度高,呈现中间高、四周低的分布特性。该综合性实验有助于学生深入理解太阳能聚光集热原理和辐射传热等基础理论知识,并可为学生开展创新实践活动提供重要平台支撑,由此提高课程教学成效和学生的综合素养。

多光齐聚来写人――浅谈小学生写人作文的方法

就像树上没有两片完全相同的叶子一样,世界上也没有一模一样的两个人。我们身边的每个人,都有自己的 特点,都是独一无二、不可取代的。可是,为什么面对这些千差万别的人,有些同学一提笔写作文就犯愁,不知 道该怎么写出人物的特点与神韵,让笔下的人物“你是你,他是他”呢?

Energy Spectrum of Two-Component Bose-Einstein Condensates in Optical Lattices

With the method of Green's function, we investigate the energy spectra of two-component ultracold bosonic atoms in optical lattices. We End that there are two energy bands for each component. The critical condition of the superfluid-Mott insulator phase transition is determined by the energy band structure. We also find that the nearest neighboring and on-site interactions fail to change the structure of energy bands, but shift the energy bands only. According to the conditions of the phase transitions, three stable superfluid and Mott insulating phases can be found by adjusting the experiment parameters. We also discuss the possibility of observing these new phases and their transitions in further experiments.

Near-Infrared emission from PbS Quantum Dots in polymer matrix

PbS quantum dots were prepared in the aqueous medium from readily available precursors. The shape of the particles isapproximately spherical, and the average particle size observed from HRTEM image was 7-8 nm. We applied PbS quantumdots and PMMA polymer to fabricate PbS quantum dots-PMMA composites, and investigate the photoluminescence PbSquantum dots in PMMA matrix with different mass ratio. PbS quantum dots in PMMA matrix have broad emission be-tween 900 nm and 1 500 nm and photoluminescence peak at 1 179 nm. Additionally, the photoluminescence intensityincreases with increasing the dopant concentration. PbS quantum dots-PMMA polymer composites can be potentially usedfor polymer optical fiber and electroluminescence (EL) in optical communication.

First Oxidation Product of Vitamin C, the Dehydro-L-Ascorbic Acid Dimer： A Study Based on FTIR-Raman and DFT Calculations

We studied the first oxidation product of vitamin C, the dehydro-L-ascorbic acid dimer and characterized it by infrared and Raman spectroscopies in the solid phase. The Density functional theory was used to study its structure and vibrational properties. These calculations gave us a precise knowledge of the normal modes of vibration taking into account that the molecule comprises a system of five fused rings; non planar γ-lactone and furonose rings are attached to a central dioxan ring in the twisted boat conformation. The calculated harmonic vibrational frequencies are consistent with the experimental vibrational spectra. An assignment of the observed spectral features is proposed. The shift of the band located in the infrared spectrum of the ascorbic acid from 3409 cm^-1 to 3299 cml and the remarkable increase in the band intensity at 1784 cm^-1 evidences the acid decomposition into its first product, the dehydro-L-ascorbic acid. The theoretical vibrational calculations allowed us to obtain a set of scaled force constants. The nature of the different -γ-lactone, furanose and dioxan rings and their topological properties were investigated by means of natural bond orbital and Bader＇s atoms in the molecule theory, respectively.

Side-on Ignition Compared with Ignition by Laser Driven Compression

Recent results for side-on ignition of uncompressed proton-boron （HB 11） fusion that use the Chu-Bobin side-on ignition with petawatt-picosecond laser pulses is extended to the reaction of helium 3-helium 3 （He3）. The HBll reaction resulted in radioactivity is lower values than from burning coal per generated energy. This was based on the very rare experiments with extreme suppression ofpre-pulses in order to suppress relativistic self-focusing. Subsequently, acceleration of highly directed plasma blocks of modest temperature and ultra-high ion current densities above 10H Amps/cm2 were measured in agreement with earlier derived theory. This permits the conditions of the Chu-Bobin for side-on ignition of solid density fusion. Results for similar neutron lean He3 are reported. A detailed comparison with the usual spherical laser compression and ignition of fusion is given for clarifying the basic differences of the ignition process.

The photoluminescence mechanism in carbon dots （graphene quantum dots, carbon nanodots, and polymer dots）： Current state and future perspective

At present, the actual mechanism of the photoluminescence （PL） of fluorescent carbon dots （CDs） is still an open debate among researchers. Because of the variety of CDs, it is highly important to summarize the PL mechanism for these kinds of carbon materials; doing so can guide the development of effective synthesis routes and novel applications. This review will focus on the PL mechanism of CDs. Three types of fluorescent CDs were involved： graphene quantum dots （GQDs）, carbon nanodots （CNDs）, and polymer dots （PDs）. Four reasonable PL mechanisms have been confirmed： the quantum confinement effect or conjugated 7x-domains, which are determined by the carbon core; the surface state, which is determined by hybridization of the carbon backbone and the connected chemical groups; the molecule state, which is determined solely by the fluorescent molecules connected on the surface or interior of the CDs; and the crosslink- enhanced emission （CEE） effect. To give a thorough summary, the category and synthesis routes, as well as the chemical/physical properties for the CDs, are briefly introduced in advance.

Biocompatible organic dots with aggregation-induced emission for in vitro and in vivo fluorescence imaging

Fluorescent probes play a key role in modern biomedical research. As compared to inorganic quantum dots (QDs) composed with heavy metal elements, organic dye-based fluorescent nanoparticles have higher biocompatibility and are richer in variety. However, traditional organic fluorophores tend to quench fluorescence upon aggregation, which is known as aggregation-caused quenching (ACQ) effect that hinders the fabrication of highly emissive fluorescent nanoparticles. In this work, we demonstrate the synthesis of organic fluorescent dots with aggregation-induced emission (AIE) in far-red/near-infrared (FA/NIR) region. A conventional ACQ-characteristic fluorescent dye, 3,4:9,10-tetracarboxylic perylene bisimide (PBI), is converted into an AIE fluorogen through attaching two tetraphenylethylene (TPE) moieties. The fluorescent dots with surface folic acid groups are fabricated from PBI derivative (DTPEPBI), showing specific targeting effect to folate receptor-overexpressed cancer cells. In vivo studies also suggest that the folic acid-functionalized AIE dots preferentially accumulate in the tumor site through enhanced permeability and retention (EPR) effect and folate receptor-mediated active targeting effect. The low cyto-toxicity, good FR/NIR contrast and excellent targeting ability in in vitro/in vivo imaging indicate that the AIE dots have great potentials in advanced bioimaging applications.