Impact of mixed low-molecular-weight organic acids on uranium accumulation and distribution in a variant of mustard (Brassica juncea var. tumida)

The impact of a mixture of low-molecular-weight organic acids (LMWOAs) composed of CA/MA/OA/LA with a molar ratio of 2.5:2.31:1.15:0.044 on uranium (U) accumulation and distribution in mustard (Brassica juncea var. tumida) was studied in this paper in order to understand the mechanism of rhizosphere-exudation assisted phytoremediation by hydroponic and pot culture experiments. The impact of the mixture of LWMOAs (Mix) on U accumulation showed that in hydroponic conditions Mix could enhance U translocation from root-to-shoot in mustard, but inhibit U uptake in root. In pot experiments, Mix enhanced both root and shoot U accumulation in mustard. The time-dependent kinetics of U uptake in mustard on Mix treatment showed that U content in plant shoots and roots increased with time increasing, and the steady state conditions were obtained at the 8th and 5th day with the U content of 1,528 and 2,300 mg/kg, respectively. Transmission electron microscope and energy dispersive X-ray spectrometry analysis for mustard roots showed that U was mainly observed on cell membrane of mustard roots on Mix treatment. This study would provide new insights for the mixture of LWMOAs-assisted phytoremediation of U-contaminated soil.     

Diode-pumped efficient continuous-wave Yb:Y3Ga5O12 laser at 1035 nm

An efficient diode-pumped Yb:Y3Ga5O12 (Yb:YGG) laser was demonstrated by using a high-quality Yb:YGG crystal grown by the optical floating zone method. Continuous-wave laser power up to 2.65?W had been obtained under an incident pump power of 6.71?W at 970?nm, corresponding to an optical-to-optical efficiency of 39.5% and maximum slope efficiency of 84.5%. A modeling calculation of the Yb:YGG laser was also performed, and the theoretical results were consistent with the experimental results.     

Tunable continuous-wave laser at quasi-three-level with a disordered Nd:LGS crystal

A diode-pumped tunable CW Nd(3+):LGS laser at quasi-three-level has been demonstrated. The output power up to 403 mW at the central wavelength of 904 nm was obtained, corresponding to a slope efficiency of 29.7%. Taking advantage of the broad emission spectrum of the disordered crystal Nd:LGS, we tuned the laser wavelength within the spectral range of 899.8 to 906.6 nm with an etalon inserted into the V-type cavity. To the best of our knowledge, it is the first time to obtain a tunable laser based on the (4)F(3/2)-(4)I(9/2) transition of Nd(3+)-doped crystals.     

稀土铒离子注入多孔硅的发光

稀土离子Ｅｒ注入多孔硅中．在３５０ｋｅＶ能量，１×１０（１２）～１×１０（１５）／ｃｍ２剂量范围内，注入后的多孔硅仍保持明亮的可见光发射．退火后，在近红外区测到１．５４μｍ附近Ｅｒ（３＋）的特征发射．其发射强度比硅单晶对照样品明显增强，实验表明这增强作用来源于多孔硅的表面发光层．电化学制备过程中在表面层中带入的Ｏ、Ｃ、Ｆ等多种杂质可能是Ｅｒ（３＋）发光增强的原因．     

超高温焙烧的Ni/Al2O3对甲烷部分氧化反应的催化活性

考察了超高温焙烧的Ni/Al2O3对甲烷部分氧化反应的催化性能,发现该催化剂经还原后对甲烷部分氧化反应表现出较高的催化活性.X射线衍射结果显示,Ni/Al2O3催化剂在超高温(1200~1400℃)下焙烧后生成了NiAl2O4,且无相转移,进一步经950℃还原后催化剂中绝大部分Ni以单质Ni0形式存在.透射电子显微镜测试结果表明,不同超高温焙烧的催化剂经950℃还原后Ni晶粒的大小无明显差异.这说明超高温焙烧的Ni/Al2O3对甲烷部分氧化反应的高活性可归结为NiAl2O4的可还原性以及还原后Ni0相似的晶粒尺寸.同时还发现,焙烧温度越高,生成的NiAl2O4的还原温度越高.     

1,1‐Dilithioethylene: Toward Spectroscopic Identification of the Definitive Singlet Ground Electronic State of a Peculiar Structure

1,1‐Dilithioethylene is a prototypical carbon–lithium compound that is not known experimentally. All low‐lying singlet and triplet structures of interest were investigated by using high‐level theoretical methods with correlation‐consistent basis sets up to pentuple ζ. The coupled cluster methods adopted included up to full triple excitations and perturbative quadruples. In contrast to earlier studies that predicted the twisted C_2v triplet to be the ground state, we found a peculiar planar C_s singlet ground state in the present research. The lowest excited electronic state of 1,1‐dilithioethylene, the twisted C_s triplet, was found to lie 9.0 kcal mol^?1 above the ground state by using energy extrapolation to the complete basis set limit. For the planar C_s singlet and twisted C_s triplet states of 1,1‐dilithioethylene, anharmonic vibrational frequencies were reported on the basis of second‐order vibrational perturbation theory. The remarkably low (2050 cm^?1) C?H stretching fundamental (the C?H bond near the bridging lithium) of the singlet state was found to have very strong infrared intensity. These highly reliable theoretical findings may assist in the long‐sought experimental identification of 1,1‐dilithioethylene. Using natural bond orbital analysis, we found that lithium bridging structures were strongly influenced by electrostatic effects. All carbon–carbon linkages corresponded to conventional double bonds.     

孔板消减气流脉动的数值模拟及实验研究

添加孔板是一种消减压缩机管道系统内气流脉动有效而简便的方法,尽管在工业生产中已被广泛应用,但是其设计和制作所需的各个参数尚处于靠经验取值的阶段.针对这种情况,首先阐述了孔板消减管道内气流脉动的机理;然后使用流体仿真计算软件Fluent建立了管道内气体的二维非稳定流动模型,计算了孔板对管道内气流的压力脉动的影响;并在数值模拟的基础上,搭建了往复式压缩机管道系统实验平台,在进气管线研究了孔板对气流脉动的消减作用.通过数值模拟和实验研究分析了孔板孔径比对气流脉动的影响,并指出选用恰当孔径比的孔板不仅能有效降低主管线和缓冲器至孔板段管线的压力脉动幅度而且对压缩机进口段管线内压力脉动同样具有良好的消减效果.     

Vector valley Hall edge solitons in the photonic lattice with type-II Dirac cones

Topological edge solitons represent a significant research topic in the nonlinear topological photonics. They maintain their profiles during propagation, due to the joint action of lattice potential and nonlinearity, and at the same time are immune to defects or disorders, thanks to the topological protection. In the past few years topological edge solitons were reported in systems composed of helical waveguide arrays, in which the time-reversal symmetry is effectively broken. Very recently, topological valley Hall edge solitons have been demonstrated in straight waveguide arrays with the time-reversal symmetry preserved. However, these were scalar solitary structures. Here, for the first time, we report vector valley Hall edge solitons in straight waveguide arrays arranged according to the photonic lattice with innate type-II Dirac cones, which is different from the traditional photonic lattices with type-I Dirac cones such as honeycomb lattice. This comes about because the valley Hall edge state can possess both negative and positive dispersions, which allows the mixing of two different edge states into a vector soliton. Our results not only provide a novel avenue for manipulating topological edge states in the nonlinear regime, but also enlighten relevant research based on the lattices with type-II Dirac cones.     

S波段四腔相对论速调管放大器的整管性能

在速调管放大器中,中间谐振腔一方面可以提高器件的放大增益,另一方面也容易产生杂频振荡,影响器件正常工作。针对这种杂频振荡的影响,在三腔相对论速调管的基础上发展了四腔相对论速调管。采用PIC粒子模拟软件从整管上对四腔强流相对论速调管放大器的冷腔结构、束波互作用、微波提取等方面进行研究。为得到输出功率和效率的最优值,结构上采用低互作用输入腔,设计了阶梯状结构漂移管,通过对输出腔作用间歇进行优化处理抑制电子回流。模拟结果表明整管微波模拟输出功率达了3.7 GW,效率22%,增益56 dB,1 dB带宽74 MHz,并实现了对杂频振荡的抑制。     

A fast solver for integral equations with convolution-type Kernel

This paper studies the data redundancy of the coefficient matrix of the corresponding discrete system which forms a basis for fast algorithms of solving the integral equation whose kernel includes a convolution function factor. We develop lossless matrix compression strategies, which reduce the cost of integral evaluations and the storage to linear complexity, i.e., the same order of the approximation space dimensions. We establish that this algorithm preserves the convergence order of the approximate solution. We also propose a hardware-aware parallel algorithm for these strategies.