Improvement of the sinterability of thermally-treated UO2 powder by horizontal rotary ball milling

Horizontal rotary ball milling has been demonstrated to be a useful method for reducing the particle size of ceramic powder in remote operation in shielded hot cells. Techniques, equipment and operating parameters, such as milling media, media wear and rotor speed were investigated with Al₂O₃ powder to evaluate its performance prior to contamination with nuclear fuel material. The established operating parameters were then verified with UO₂ powder, which had been produced by a thermal process to make fuel pellets. The sintering of the milled UO₂ powder showed the higher sintered densities obtainable by the milling, and the milling process seemed to be an important factor in improving the powder characteristics. This article is based on a presentation made in the “Symposium on Nuclear Materials and Fuel 2000“, held at the Korea Atomic Energy Research Institute (KAERI), Taejon, Korea, August 24–25 under the auspices of the Ministry of Science and Technology (MOST).     

Performance of solid alkaline fuel cells employing anion-exchange membranes

For the performances of solid alkaline fuel cells (SAFCs) using anion-exchange membranes (AEMs), anion-exchange membranes were prepared via chloromethylation and amination of polysulfone and membrane-electrode assemblies (MEAs) were fabricated using the AEMs as an electrolyte, the ionomer binder prepared by the AEMs and Pt/C and Ag/C electrocatalysts as an anode and a cathode, respectively. Anion-exchange membranes were aminated by a mixing amine agent of trimethylamine (TMA) as a monoamine and various diamines such as N,N,N′,N′-tetramethylmethanediamine (TMMDA), N,N,N′,N′-tetramethylethylenediamine (TMEDA), N,N,N′,N′-tetramethyl-1,3-propandiamine (TMPDA), N,N,N′,N′-tetramethyl-1,4-butanediamine (TMBDA) and N,N,N′,N′-tetramethyl-1,6-hexanediamine (TMHDA). Amination using various diamines enabled to investigate the effect of the length of alkyl chain of the diamines on membrane properties such as ion conductivity and thermal characteristics. The AEMs aminated by the amination agent of mixing TMA and TMHDA (with longer alkyl chain) showed better hydroxyl ion conductivity and thermal stability than those aminated by a diamine. The H₂/air SAFC performance of the MEA with 0.5 mg cm⁻² Pt/C at the anode and the cathode, respectively, was comparable to one with 0.5 mg cm⁻² Pt/C at the anode and 2.0 mg cm⁻² Ag/C at the cathode, i.e., approximately 28–30 mW cm⁻² of the peak power density range.     

香港环境辐射监测的公众教育工作

香港天文台于1987年展开了全面的环境辐射监测计划。为了增强工作的透明度,让公众充分了解监测计划的内容,领会监测数据的意义,独立地判断香港的环境辐射水平是否正常,系统的公众教育工作是不可或缺的。天文台采取的教育途径包括利用展览向公众介绍辐射、核能发电及天文台的环境辐射监测,向公众定期发表环境辐射监测计划中测量到的环境辐射水平数据。随着信息技术的发展,天文台在国际互联网上设立了一个网站,向公众介绍天文台的工作及提供有关的资料。     

Evaluation of motion-based interaction for mobile devices: A case study on image browsing

This article evaluates the usability of motion sensing-based interaction on a mobile platform using image browsing as a representative task. Three types of interfaces, a physical button interface, a motion-sensing interface using a high-precision commercial 3D motion tracker, and a motion-sensing interface using an in-house low-cost 3D motion tracker, are compared in terms of task performance and subjective preference. Participants were provided with prolonged training over 20 days, in order to compensate for the participants’ unfamiliarity with the motion-sensing interfaces. Experimental results showed that the participants’ task performance and subjective preference for the two motion-sensing interfaces were initially low, but they rapidly improved with training and soon approached the level of the button interface. Furthermore, a recall test, which was conducted 4 weeks later, demonstrated that the usability gains were well retained in spite of the long time gap between uses. Overall, these findings highlight the potential of motion-based interaction as an intuitive interface for mobile devices.     

Microarray with Micro‐ and Nano‐topographies Enables Identification of the Optimal Topography for Directing the Differentiation of Primary Murine Neural Progenitor Cells

During development and tissue repair, progenitor cells are guided by both biochemical and biophysical cues of their microenvironment, including topographical signals. The topographical cues have been shown to play an important role in controlling the fate of cells. Systematic investigation of topographical structures with different geometries and sizes under the identical experimental conditions on the same chip will enhance the understanding of the role of shape and size in cell–topography interactions. A simple customizable multi‐architecture chip (MARC) array is therefore developed to incorporate, on a single chip, distinct topographies of various architectural complexities, including both isotropic and anisotropic features, in nano‐ to micrometer dimensions, with different aspect ratios and hierarchical structures. Polydimethylsiloxane (PDMS) replicas of MARC are used to investigate the influence of different geometries and sizes in neural differentiation of primary murine neural progenitor cells (mNPCs). Anisotropic gratings (2 μm gratings, 250 nm gratings) and isotropic 1 μm pillars significantly promote differentiation of mNPCs into neurons, as indicated by expression of β‐III‐tubulin (59%, 58%, and 58%, respectively, compared to 30% on the control). In contrast, glial differentiation is enhanced on isotropic 2 μm holes and 1 μm pillars. These results illustrate that anisotropic topographies enhance neuronal differentiation while isotropic topographies enhance glial differentiation on the same chip under the same conditions. MARC enables simultaneous cost‐effective investigation of multiple topographies, allowing efficient optimization of topographical and biochemical cues to modulate cell differentiation.     

Effect of the Ca content on the microstructural evolution of Ca containing AZ31 cast alloys

Microstructural changes with varying amounts of Ca in cast AZ31-xCa (x: 0.7 wt.%, 2.0 wt.%, 5.0 wt.%) alloys were investigated. According to transmission electron microscopy (TEM) analyses, it was experimentally confirmed that the C36-(Mg,Al)₂Ca phase with a di-hexagonal structure formed at interdendritic regions in as-cast AZ31 alloys with no more than 2 wt.% Ca. On the other hand, as the Ca content exceeded 2 wt.%, the lamellar structure consisting of the α-Mg phase and the Mg₂Ca phase with a C14 structure formed at interdendritic regions instead of C36 phase. Plate-like Al₂Ca precipitates with a C15 structure also formed on the basal plane inside the α-Mg grains.     

Design and Analysis of a Gyroscopically Controlled Micro Air Vehicle

Micro air vehicles have emerged as a popular option for diverse robotic and teleoperated applications in both open terrain and urban environments because of their inherent stealth and portability. To perform many of the tasks envisioned for micro air vehicles, agility is essential. To date, research efforts to improve agility have focused primarily on constructing complex controllers to enable existing vertical-take-off- and-landing vehicles, such as remote-controlled helicopters and quadrotors, to perform aerobatic maneuvers autonomously. In this work, we adopt a system-level perspective and analyze a new design for a rotary-wing micro air vehicle that utilizes gyroscopic dynamics for attitude control. Unlike traditional vehicles where attitude control moments are generated by aerodynamic control surfaces, the proposed vehicle will leverage the existing angular momentum of its counter rotating components. This paradigm has the potential to yield significant increases in agility when compared to state-of-the-art micro vertical take-off and landing vehicles. The proposed design reduces mechanical complexity by precluding the use of complex mechanisms, such as the swashplate. The capacity to rapidly generate large gyroscopic control moments, coupled with the precision gained from eliminating the need for complex and restrictive aerodynamic models, improves both agility and adaptability. We present the development of a gyroscopically controlled micro air vehicle including comprehensive models of the dynamics and the aerodynamics with an emphasis on the design and analysis of such systems. A dynamics simulator that incorporates these models and mechanical hardware solutions to challenges that arose during prototyping will also be presented.     

A Review of Pinealectomy-Induced Melatonin-Deficient Animal Models for the Study of Etiopathogenesis of Adolescent Idiopathic Scoliosis

Adolescent idiopathic scoliosis (AIS) is a common orthopedic disorder of unknown etiology and pathogenesis. Melatonin and melatonin pathway dysfunction has been widely suspected to play an important role in the pathogenesis. Many different types of animal models have been developed to induce experimental scoliosis mimicking the pathoanatomical features of idiopathic scoliosis in human. The scoliosis deformity was believed to be induced by pinealectomy and mediated through the resulting melatonin-deficiency. However, the lack of upright mechanical spinal loading and inherent rotational instability of the curvature render the similarity of these models to the human counterparts questionable. Different concerns have been raised challenging the scientific validity and limitations of each model. The objectives of this review follow the logical need to re-examine and compare the relevance and appropriateness of each of the animal models that have been used for studying the etiopathogenesis of adolescent idiopathic scoliosis in human in the past 15 to 20 years.     

Membrane Profiling by Free Flow Electrophoresis and SWATH-MS to Characterize Subcellular Compartment Proteomes in Mesembryanthemum crystallinum

The study of subcellular membrane structure and function facilitates investigations into how biological processes are divided within the cell. However, work in this area has been hampered by the limited techniques available to fractionate the different membranes. Free Flow Electrophoresis (FFE) allows for the fractionation of membranes based on their different surface charges, a property made up primarily of their varied lipid and protein compositions. In this study, high-resolution plant membrane fractionation by FFE, combined with mass spectrometry-based proteomics, allowed the simultaneous profiling of multiple cellular membranes from the leaf tissue of the plant Mesembryanthemum crystallinum. Comparisons of the fractionated membranes’ protein profile to that of known markers for specific cellular compartments sheds light on the functions of proteins, as well as provides new evidence for multiple subcellular localization of several proteins, including those involved in lipid metabolism.