Nanomaterial engineering and property studies in a transmission electron microscope

Modern methods of in situ transmission electron microscopy (TEM) allow one to not only manipulate with a nanoscale object at the nanometer-range precision but also to get deep insights into its physical and chemical statuses. Dedicated TEM holders combining the capabilities of a conventional high-resolution TEM instrument and atomic force -, and/or scanning tunneling microscopy probes become the powerful tools in nanomaterials analysis. This progress report highlights the past, present and future of these exciting methods based on the extensive authors endeavors over the last five years. The objects of interest are diverse. They include carbon, boron nitride and other inorganic one- and two-dimensional nanoscale materials, e.g., nanotubes, nanowires and nanosheets. The key point of all experiments discussed is that the mechanical and electrical transport data are acquired on an individual nanostructure level under ultimately high spatial, temporal and energy resolution achievable in TEM, and thus can directly be linked to morphological, structural and chemical peculiarities of a given nanomaterial.     

The thinning of SpangoldTM for transmission electron microscopy studies

Abstracts are not published in this journal     

输电杆塔阵风响应实测与准静态设计研究

为分析输电塔的动力特性和阵风响应因子的变化规律,在现场风荷载条件下,对作用于新建输电塔的脉动风速及其各部位加速度和基底动应变响应进行了同步实测。采用模态识别法和有限元法对输电塔的动力特性进行了对比分析;采用实测数据直接分析法和不同的准静态法分别计算了基于塔顶位移和基底弯矩的阵风响应因子。结果表明,实测数据的模态识别法与有限元法得到的输电塔动力特性相吻合,有限元数值分析正确有效;实测数据分析法与准静态法得到的阵风响应因子的变化规律相同,且与脉动风速的均值和湍流强度相关;基于弯矩的阵风响应因子吻合较好,各种方法的计算值相差在5%以内;基于实测位移的阵风响应因子与准静态法差异较大,其原因有待于进一步试验研究的检验与识别。     

Multiplexed holographic transmission gratings recorded in holographic polymer-dispersed liquid crystals: static and dynamic studies

The optimization of the experimental parameters of two multiplexed holographic transmission gratings recorded in holographic polymer-dispersed liquid crystals is investigated. Two methods are used to record the holograms: simultaneous and sequential multiplexing. These two processes are optimized to produce two multiplexed Bragg gratings that have the same and the highest possible diffraction efficiencies in the first order. The two methods show similar results when suitable recording parameters are used. The parameters of the recorded gratings (mainly the refractive-index modulation) are retrieved by use of an extension of the rigorous coupled-wave theory to multiplexed gratings. Finally, the response of the holograms to an electric field is studied. We demonstrate few coupling effects between the behavior of both gratings, and we expect a possibility of switching from one grating to the other.     

Nonlinear and magneto-optical transmission studies on magnetic nanofluids of non-interacting metallic nickel nanoparticles

Oxide free stable metallic nanofluids have the potential for various applications such as in thermal management and inkjet printing apart from being a candidate system for fundamental studies. A stable suspension of nickel nanoparticles of ～ 5 nm size has been realized by a modified two-step synthesis route. Structural characterization by x-ray diffraction and transmission electron microscopy shows that the nanoparticles are metallic and are phase pure. The nanoparticles exhibited superparamagnetic properties. The magneto-optical transmission properties of the nickel nanofluid (Ni-F) were investigated by linear optical dichroism measurements. The magnetic field dependent light transmission studies exhibited a polarization dependent optical absorption, known as optical dichroism, indicating that the nanoparticles suspended in the fluid are non-interacting and superparamagnetic in nature. The nonlinear optical limiting properties of Ni-F under high input optical fluence were then analyzed by an open aperture z-scan technique. The Ni-F exhibits a saturable absorption at moderate laser intensities while effective two-photon absorption is evident at higher intensities. The Ni-F appears to be a unique material for various optical devices such as field modulated gratings and optical switches which can be controlled by an external magnetic field.     

欧洲的Keymark认证

为了鼓励对新能源的利用和对使用新能源设备的研发,欧洲很多国家相应出台一系列鼓励措施.比如:欧洲许多政府颁发法规给购买具备Keymark标志的太阳能产品(如集热器、整个太阳能热水器系统等)的消费者补贴,有的国家最高补贴达产品售价的50%.     

欧洲设计之旅

2010年12月5日至12月15日,在《包装＆设计》杂志社与广州美院张海文教授的共同组织下,欧洲设计考察团历经法、德、奥,对当地的顶尖设计公司和设计院校进行设计交流考察,在体验冬日雪景和圣诞气氛的同时感受到了不同文化与设计的魅力。     

Free-electron Lasers in Europe

The principles of a free-electron laser are outlined, and a brief history of its development is given. The main experimental results obtained to date are described with emphasis on results obtained by European workers.