HIGH RESOLUTION REAL-TIME MEDICAL IMAGING BASED ON PARALLEL BEAMFORMING TECHNIQUE

Improvement of frame-rate is very important for high quality ultrasound imaging of fast-moving structures.It is also one of the key technologies of Three-Dimension (3-D) real-time medical imaging.In th...     

Essential oil composition and antimicrobial activity of Sphallerocarpus gracilis seeds against selected food-related bacteria

Sphallerocarpus gracilis from China is a little-investigated edible and medicinal plant. In the present study, the essential oil composition from S. gracilis seeds was investigated by GC and GC–MS. A total of 34 compounds representing 94.69% of the essential oil were tentatively identified. The main constituents were p-cymene (17.42%), γ-terpinene (25.58%) and α-asarone (33.12%). The antimicrobial activity, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) of the essential oil from S. gracilis seeds were evaluated against eight Gram-positive bacteria (Listeria monocytogenes, Staphylococcus aureus, Staphylococcus epidermidis, Micrococcus luteus, Bacillus megaterium, Bacillus cereus, Bacillus coagulans and Bacillus subtilis), four Gram-negative bacteria (Salmonella enteritidis, Salmonella typhimurium, Klebsiella pneumoniae and Escherichia coli) and one fungus (Aspergillus niger). Results revealed that the essential oil from S. gracilis seeds exhibited significant in vitro antimicrobial property. Among all the tested microorganisms, the essential oil showed the strongest inhibitory effect against K. pneumoniae, whereas no inhibitory effect was found against L. monocytogenes and A. niger. Additionally, scanning electron microscopy (SEM) was used to observe morphological changes of bacteria treated with the essential oil from S. gracilis seeds. SEM observations confirmed the physical damage and considerable morphological alteration to the tested microorganisms treated with the essential oil. The data of this study suggests that the essential oil from S. gracilis seeds has great potential for application as a natural antimicrobial agent to preserve food.     

The microstructure and tensile property degradation of a gamma-TiAl alloy during isothermal and cyclic high temperature exposures

The microstructure and tensile property changes of a γTiAl-based alloy, Ti-47Al-2Cr-2Nb-0.15B, during isothermal and cyclic high temperature exposures have been investigated. Microstructure coarsening, including the fracture, dissolution and spheroidization of α₂ lamellae, is considered to be the main cause of the evident tensile property decreases of the alloy after isothermal and cyclic high temperature exposures. Dislocation emission near the broken lamellae is also an important phenomenon in the microstructure degradation during cyclic high temperature exposure, which originated from the thermal mismatch between α₂ and γ phases.     

Material flow and core/multi-shell structures in a friction stir welded aluminum alloy with embedded copper markers

The objective of this study was to reveal the material flow and temperature distribution in a thick aluminum plate during friction stir welding and examine the subsequent microstructural change with particular attention to the reaction between copper marker and aluminum matrix. It is shown that the material adjacent to the threaded pin was transported from the top to bottom non-symmetrically, and then was forced to move upwards at a small distance from the pin due to the constraint of an extrusion-die-like configuration. The interaction between the copper marker and aluminum matrix led to the formation of (i) a unique core/multi-shell microstructure consisting of copper core, inner shell of AlCu and outer shell of Al₂Cu, and (ii) a composite band containing uniformly-distributed Al₂Cu particles with refined grains due to the lower stacking fault energy of copper and the pinning role of Al₂Cu particles.     

网络计划技术在暖通空调工程管理中的应用

结合实际工程,介绍了该应用的具体步骤。通过对工程的分析,绘制了网络图,找到了关键线路,并对工程计划进行了优化。     

THE BOUNDEDNESS OF BILINEAR SINGULAR INTEGRAL OPERATORS ON SIERPINSKI GASKETS

In the paper we give the boundedness estimate of bilinear singular integral operators on Sierpinski gasket inspired from[1].     

PREPARATION OF POLYALKYLCYANOACRYLATE NANOPARTICLES WITH VARIOUS MORPHOLOGIES

The effects of various reaction conditions on the preparation of polyalkylcyanoacrylate(PACA)nanoparticles are studied. The PACA nanoparticles with different crosslinking degrees and morphology arc prepared. Addition of crosslinkers can not only adjust the particle size,but also change the morphology of PACA nanoparticles. Moreover,the loose network structure of the PACA nanoparticles with core/shell-like morphology is investigated by AFM and TEM in detail.     

对外空安全合作的理性审视与战略思考

随着现代科学技术特别是空间技术的发展,外空安全合作的现状令人担忧,主要表现为个别国家谋求外空绝对优势和绝对霸权的威胁加剧,外空武器化和外空军备竞赛的趋势日益明显,外空碎片的自杀伤效应日益严重,外空人为污染导致外空环境安全日益恶化.造成外空安全合作迟滞的主要原因包括:外空安全合作的权力分配结构失衡,抑制外空武器化和外空军备竞赛的强制力不足,外空碎片治理的共同利益基础较为薄弱,保护外空环境安全的共有观念不强.因此,推进外空安全合作要通过协调外空国际安全互动而寻求安全合作,重点抑制外空武器化和外空军备竞赛,促进外空行为规则的制订,广泛倡导新安全观以增进外空环境安全合作.