Fluidic origami with embedded pressure dependent multi-stability: a plant inspired innovation

Inspired by the impulsive movements in plants, this research investigates the physics of a novel fluidic origami concept for its pressure-dependent multi-stability. In this innovation, fluid-filled tubular cells are synthesized by integrating different Miura-Ori sheets into a three-dimensional topological system, where the internal pressures are strategically controlled similar to the motor cells in plants. Fluidic origami incorporates two crucial physiological features observed in nature: one is distributed, pressurized cellular organization, and the other is embedded multi-stability. For a single fluidic origami cell, two stable folding configurations can coexist due to the nonlinear relationships among folding, crease material deformation and internal volume change. When multiple origami cells are integrated, additional multi-stability characteristics could occur via the interactions between pressurized cells. Changes in the fluid pressure can tailor the existence and shapes of these stable folding configurations. As a result, fluidic origami can switch between being mono-stable, bistable and multi-stable with pressure control, and provide a rapid ‘snap-through’ type of shape change based on the similar principles as in plants. The outcomes of this research could lead to the development of new adaptive materials or structures, and provide insights for future plant physiology studies at the cellular level.     

Micrometeoroid impact on ceramic thin components for interplanetary probe

A new advanced ceramic thruster made of monolithic silicon nitride (Si₃N₄) is under development for the next interplanetary probe of PLANET-C Venus exploration mission in Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA). In order for secure operation of a spacecraft with a ceramic component onboard a real mission, the reliability against micrometeoroid impacts on the ceramic component has to be investigated in addition to the quasi-static mechanical and thermal analyses and verifications. First, the risk probability of the micrometeoroid impacts was evaluated by using an interplanetary flux model, and the risk evaluation in terms of impact energy was proposed by combining the velocity distribution with the flux model. The probability of impacts on the ceramic thruster during the mission was estimated with this model. Second, hypervelocity impact tests were performed with a two-stage light-gas gun. Three types of failure were observed: one was only a crater formed on the impact surface. Another type was crater formation on the front-face and spall fracture on the back-face and in the last type a perforation was formed in addition to cratering and spalling. The samples did not either shatter or breakdown for the impact energies tested in this study. The impact failure morphology observed in this study showed dependency on the plate thicknesses and the projectile kinetic energy. The energy-based risk evaluation together with the series of the hypervelocity impact tests indicated that the silicon nitride ceramic thruster onboard the interplanetary probe would have only a local damage and survive during the mission term.     

启明星1#次临界装置热中子能谱区裂变率分布测量

启明星1#是我国专门为开展加速器驱动次临界系统研究而建立的国际上第1个具有快-热耦合结构的次临界反应堆实验装置。采用MCNP程序对堆芯裂变率分布进行指导性计算,并参考计算结果布置探测片,用固体核径迹探测器测量了堆芯热区裂变率分布。测量结果显示:堆芯有反射层一端的裂变率比无反射层一端的高;轴向加装反射层末端的裂变率明显增大。测量结果对确定热区的裂变功率提供了数据。     

启明星1#快热交界面能谱变化对外推临界实验结果影响分析

加速器驱动的次临界系统（ADS）基准装置启明星1#在外推临界实验过程中,快热交界面探测器计数率与其他位置探测器计数率存在较大异常。本工作对该实验装置外推临界实验开展数值模拟,并对快热交界面的中子能谱进行详细计算,根据计算结果对探测器在外推临界实验中的计数率异常现象进行分析。结果表明,快热交界面能谱随燃料装载量的变化是引起探测器计数率异常的主要因素,这为今后快热耦合次临界实验装置开展中子学实验研究提供了理论依据。     

启明星2#反应堆临界运行方式的堆芯物理方案初步研究

本工作提出利用中国先进研究堆乏燃料组件构造既能在加速器驱动下次临界运行,也能临界运行的启明星2#反应堆堆芯方案。采用MVP-BURN蒙特卡罗燃耗程序,对反应堆临界运行方式下的堆芯方案进行了优化选择,给出了优选方案的核特性参数。     

ADS次临界实验装置--启明星1#

文章介绍加速器驱动次临界系统（ADS）中次临界实验装置——启明星1#的设计目的、要求、结构和可开展的工作。启明星1#是由快中子能谱区和热中子能谱区耦合组成的堆芯和由高压倍加器氘-氚反应中子源来驱动的次临界系统。快中子能谱区处在堆芯内部，该区提供快中子谱，还可放大外中子源，以驱动热区；热中子能谱区处在堆芯外部，主要用来能量放大，以维持装置的链式裂变反应。     

‘Carte du Ciel’: Sydney Observatory's Role in the International Project to Photograph the Heavens

One of the most ambitious photographic projects the world has ever seen was announced at the 1887 International Astronomical Conference. Known as the Carte du Ciel’ or ‘Mapping the Stars’ project, its grand aim was to record on photographic plates the stars in the night sky. Worked on by eighteen observatories around the world, it was estimated that it would require 22,154 photographic plates. Although little known today, this project cemented the role of photography as a tool for astronomers and was in particular a major accomplishment for the Sydney Observatory, where it was worked on for over seventy years.     

Metal levels in economically important bivalve species from Turkey

Concentrations of eight heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) were determined in economically important bivalve species: oyster (Ostrea edulis), wedge clam (Donax trunculus), manila clam (Ruditapes philippinarium) and warty clam (Venus verrucosa) from the Marmara and Aegean seas. Samples were collected seasonally between 2008 and 2009. Metal levels of bivalves were found in the following ranges: As 0.02–3.40, Cd 0.02–2.80, Cr 0.19–0.82, Cu 0.82–25.06, Hg?<?LOD–0.12, Ni 0.09–0.73, Pb 0.05–4.16 and Zn 6.85–899?mg?kg^?1. The most abundant elements were Zn?>?Cu?>?As. In addition, the results showed that oysters had the highest concentrations of Zn in all seasons. The next abundant heavy metal detected was Cu in oyster and other clam species. It was concluded that in the future, these metals should be monitored regularly.     

金星表面THz遥感探测

从“金星快车可见光与红外热成像光谱仪（VIRTIS）载荷成功地实现了对金星表面辐射探测”事实出发,利用高分辨率传输分子光谱数据库（HITRAN）,仿真验证了金星大气模型相适应的近红外大气窗口,从而分析并获取了金星 THz 大气窗口。与此相适应,从实现金星地表全天候遥感探测科学目标出发,系统阐述了金星大气 THz窗口下探测的优势,提出多功能金星遥感构想。     

Learning to Recognize Volcanoes on Venus

Dramatic improvements in sensor and image acquisition technology have created a demand for automated tools that can aid in the analysis of large image databases. We describe the development of JARtool, a trainable software system that learns to recognize volcanoes in a large data set of Venusian imagery. A machine learning approach is used because it is much easier for geologists to identify examples of volcanoes in the imagery than it is to specify domain knowledge as a set of pixel-level constraints. This approach can also provide portability to other domains without the need for explicit reprogramming; the user simply supplies the system with a new set of training examples. We show how the development of such a system requires a completely different set of skills than are required for applying machine learning to toy world domains. This paper discusses important aspects of the application process not commonly encountered in the toy world, including obtaining labeled training data, the difficulties of working with pixel data, and the automatic extraction of higher-level features.