浅析晚清岭南园林植物景观

通过对岭南四大名园的植物进行调查、分析,使我们对传统岭南园林植物景观有更全面的了解,对发扬传统岭南植物景观特色,创造富有地方特色和文化韵味的植物景观起到一定的借鉴作用。     

宽频超声衰减法测量河流泥沙粒径分布

为了研究宽频超声波通过河流泥沙悬浊液的声衰减谱中包含泥沙的颗粒粒度信息,采用超声耦合相模型和散射模型的叠加描述河流泥沙悬浊液中超声衰减行为,宽频超声换能器测量得到2～7.5MHz间泥沙悬浊液声衰减谱,结合独立模式的最优正则化反演算法,获得了相同体积浓度、不同粒径分布下和相同粒径分布、不同体积浓度下泥沙的颗粒粒径分布。结果表明,宽频超声衰减法能较好地区分3种不同粒径分布的泥沙,并且在体积浓为3.8%～8.5%范围间,测量得到的平均粒径受浓度变化影响较小。将超声法测量结果与显微镜图像法测量结果相比较,两种方法得到的粒径分布趋势较为一致,平均粒径较为吻合。     

Electrospinning of hydroxyapatite fibrous mats

Polyvinyl alcohol (PVA) with an average molecular weight between 40,500 and 155,000 g/mol was electrospun with a calcium phosphate based sol. The sol was prepared by reacting triethyl phosphite and calcium nitrate and was directly added to an aqueous solution of PVA. This mixture was electrospun at a voltage of 20 kV. The results indicate that the sol was distributed uniformly in the PVA fibers, whose diameter was on the order of 2 μm. This electrospun structure was calcined at 600 °C for 6 h to obtain a residual inorganic, fibrous network, with fiber diameters between 200 and 800 nm. The fibrous structure consists predominantly of hydroxyapatite with an average crystal size of almost 10 to 30 nm. A variety of structures including non-woven mats of solid or micro-porous hydroxyapatite fibers and highly porous scaffolds could be obtained by varying the polymer molecular weight and the sol volume fraction. These structures can have many potential uses in the repair and treatment of bone defects, drug delivery and tissue engineering.     

Enhanced performance of FeOOH/ZnIn2S4/Au nanosheet arrays for visible light water splitting

Journal of Materials Science: Materials in Electronics - Carrier separation, charge transport, and visible light absorption are the main factors affecting the solar water splitting performance of a...     

Properties of porous Si3N4 ceramic electromagnetic wave transparent materials prepared by technique combining freeze drying and oxidation sintering

A simple and low-cost technique combining freeze drying and oxidation sintering is explored to prepare Si₃N₄ ceramics with high porosity and complex shape. The effects of sintering temperature and time on the phase composition, microstructure, porosity, pore size and dielectric constant of the porous Si₃N₄ ceramics are studied. Due to the variations of phase composition and microstructure, the porous Si₃N₄ ceramics sintered at different temperature possess characteristic in flexural strength. The porous Si₃N₄ ceramics sintered at 1,300 °C for 2–3 h have the highest flexural strength of 71–74 MPa. The changes of porosity and composition have much effect on the dielectric constant of porous Si₃N₄ ceramics. Because of the high porosity and SiO₂ volume fraction, the porous Si₃N₄ ceramics sintered at 1,300 °C for 2–3 h possess low dielectric constant of 3.4–3.6 and small pore size of 0.9 μm. The porous Si₃N₄ ceramics are good structural/functional and promising electromagnetic wave transparent material.     

Backprojection by Multiorientation Simultaneous Computation Scheme for CT Image Reconstruction

1IntroductionIncommercialComputerizedTomographic(CT)imagingsystems,thefilteredorconvolvedbackprojectionalgorithm['J--['tiscurrentlyusedforimagereconstruction.Itingeniouslyseparatesthereconstructionprocedureintotwosteps:theprojectiondataarelinearlyconvolve…     

大气湍流畸变波前斜率的稀疏分解

利用压缩感知技术对大气湍流波前探测数据进行压缩,可使测量数据量大幅度减少,能有效降低数据的传输与存储压力,有利于湍流波前的实时测量;但压缩条件要求波前信号是稀疏的或在某个变换域内能够稀疏表示。本文对大气湍流波前斜率信号的稀疏性进行了初步研究,基于大气湍流的统计特性,在频域内对湍流功率谱作黄金分割采样(GS),建立符合大气湍流斜率物理特征的稀疏基,明确了湍流波前斜率的稀疏性。利用该GS稀疏基对波前斜率进行稀疏分解,并通过仿真实验对比了不同稀疏基对波前斜率的稀疏分解效果。在此基础上,以GS基作为训练基的初始化字典,进行K奇异值分解字典训练(KSVD),得到训练基(KSVD-GS),分析了该训练基对波前斜率信号的稀疏表示性能。本文验证了波前斜率能够稀疏分解,建立了一个较好的稀疏基,为压缩感知的应用提供了前提基础。

     

Gelatin manipulation of latent macropores formation in brushite cement

Macroporous brushite cement was prepared from a mixture of -tricalcium phosphate (-TCP) and monocalcium phosphate monohydrate (MCPM) using gelatin powder as a latent templates. In a setting reaction coexisting with gelatin, closed packed, open-pore structure with 100–200 m macropores are obtained after immersion of the set cement into PBS buffer (pH 7.4) at 37 °C for 1–4 weeks. The macroporous brushite cement has compressive strength of 15 MPa originally, which reducing to 5.5 MPa with macropore formation gradually in comparison to that of cancellous bone (5–10 MPa).     

全离子注入双极硅微波晶体管E-B结低、软特性浅析

通过全离子注入双极硅微波晶体管研究中出现的E-B结特性软、低击穿和β变小等现象,从理论上给以浅析,同时,指出了设计和工艺上改进的措施。