Nanohybrid scratch resistant coatings for teeth and bone viscoelasticity manifested in tribology

We cover teeth surfaces with nanohybrid coatings containing an inorganic ceramic and an organic copolymer constituents. We report the first ever values of scratch penetration depth and scratch recovery for bare and coated teeth. We find that uncoated teeth undergo viscoelastic recovery (healing) after microscratching – the first manifestation of bone viscoelasticity in tribology. The coatings fill "valleys" in teeth surfaces. In each case a large improvement in the scratch resistance as compared to uncoated teeth is seen. The extent of the improvement depends on the inorganic/organic component ratios in the nanohybrids. Electronic Publication     

基于虚拟样机技术月球机器人运动仿真

采用“虚拟样机”技术,建立一个集三维实体设计,动力学建模,控制,可视化仿真于一体的虚拟月面计算机仿真环境,对月球机器人的静力学,运动学以及动力学进行仿真研究,为月球机器人结构参数,动力学参数及控制算法的优化提供了设计参数和验证场所。     

定常推力登月飞行器最优软着陆轨道研究

完成了推力幅值恒定的登月飞行器最优软着陆轨道的研究。建立了用于描述软着陆轨道任务的完整系统模型。通过将参数化方法和序列二次规划(SQP)方法应用于归一化处理后的模型,得到了飞行时间最优的轨道。     

月球软着陆的显式制导控制研究

软着陆燃耗最优制导控制的结果提出一种用于月球软着陆动力的过程的显式制导方法,它不饱含制动发动机的参数信息,也不需要迭代计算,测得简单,仅需要一个惯性测量单元。通过一个软着陆实例验证了这种制导的律的最优性和鲁棒性。     

一种月尘颗粒电荷质量比原位监测方法

月尘粒子在月表高真空、高低温交变、强辐射条件下极易带电悬浮,大量带电月尘会聚集在探测器表面造成极大危害。为了能够更好地了解月球尘埃的带电特性,对月尘带电特性进行了分析,提出一种测量方法,设计出一种能够测量带电月尘荷质比的传感器,并设计出地面检测和标定实验方法,为将来探月工程中原位监测月尘带电粒子荷质比提供了很好的技术支持。     

月尘的性质及危害评述

月尘一直以来都是阻碍人类探索月球的一大问题,月尘颗粒锋利、细微和带静电等特性可对各类机械结构、密封结构、功能表面、空间仪器载荷以至宇航员产生巨大危害。文章总结了目前月尘防护技术的研究进展,包括月尘的全流程防护及大空间月尘防护研究;以电磁法为代表的主动防护技术,如电帘、静电场、等离子体束、电喷雾和磁辊等除尘技术;以表面改性技术为主的被动防护技术,如减弱范德瓦耳斯力的低表面能、高粗糙度的纳米尺度涂层和减弱静电力的功函数匹配涂层等。聚焦中国探月工程水冰探测计划的月尘防护,综述了针对采掘、加热和分析三个环节所使用的过滤和密封的防尘手段,包括采掘钻杆使用螺旋槽和间隙密封;加热和分析容器采用金属刀口主密封和O型圈辅助密封;在分析仪器前设置烧结金属过滤器、高效空气过滤器（HEPA）和多级永磁月尘过滤器（LAF-PMS）;在连接管道处设置双层O型圈密封;在外接出口处设置迷宫密封和HEPA等。最后,给出一种“水冰探测仪月尘防护的方案设计”。

     

月尘沉积对太阳电池短路电流影响的试验研究

本文通过地面模拟实验对空载-负载情况下太阳电池短路电流与光线入射角的关系、不同光线入射角下太阳电池短路电流与月尘沉积质量的关系以及不同粒径范围的月尘沉积对太阳电池短路电流影响关系进行研究。研究结果表明,由于角损耗的原因,无论有无月尘沉积的太阳电池其短路电流与光线入射角的关系均不能用余弦函数近似,且随着太阳电池表面月尘沉积量增加,角损耗现象变得更加明显。其次,在任意光线入射角下,太阳电池的短路电流和沉积月尘的质量的关系都可用指数拟合,但过大的光线入射角会导致太阳电池的灵敏度下降严重。最后,相同沉积质量下,月尘粒径越小,则对太阳电池的遮蔽效果越强,这是由于小粒径月尘颗粒的比表面积更大以及颗粒之间的缝隙更小所致。     

小子样试验法在月球样品容器密封可靠性评估中的应用

为解决月球样品容器密封可靠性评估的问题,将目前常用的可靠性评估方法引入并应用于对其可靠性的评估。经分析比较,选择所需子样数最少的最大熵试验法作为最终评估方法并详细介绍评估过程。该方法选取容器的密封漏率作为表征密封性能的特征量,通过在临界工况点进行试验和计算来实现可靠性评估。同时,针对密封漏率数值的特殊性提出了其裕度值的计算方法。结果表明,利用最大熵试验法仅通过少量试验即可评估出月球样品容器密封可靠度优于0.9999(置信度0.90),并经计量法评估方法进行复算,结果一致、可信。     

Estimating the background count rate in the energy field from 0.55-2.75 MeV for Chang'E-1 gamma-ray spectrometer

With a large geometrical area, the Gamma-ray spectrometer (GRS) onboard Chang'E-1 was designed to detect gamma rays from the moon. The scientific objective is to study the element information including both type and abundance by distinguishing the energy of gamma ray peak relative to elements and calculating the peak area counts. Regretfully, the cislunar spectrum of GRS was not collected. Nevertheless, we give a method to estimate the background count rate in the energy field from 0.55-2.75 MeV. A natural radioactivity count rate map in 2°×2° grids is shown after reducing the background count rate and the uncertainty of the result is discussed.     

一种适合于月球车的长距离自主导航方法

针对月球车自主导航系统的特殊要求,设计了一种月球车长距离自主导航方法.该方法首先依据惯性导航和天文学的基本原理建立月球环境下惯性导航系统的姿态、速度和位置误差方程,然后针对捷联惯性系统平台失准角较大的问题,引入里程计测量的速度信息与球面天文三角公式,共同构建量测方程,由于建立的系统状态方程和量测方程均为线性方程,所以采用卡尔曼滤波实现月球车位姿信息的最优估计.最后,对这一导航方法进行了仿真研究,仿真结果表明,该方法具有更高的位置和姿态估计精度,同时可有效提高系统的稳定性和可靠性,是解决月球车自主导航问题的一种有效而实用的自主导航方法.     

A novel method for synthesizing nano-crystalline MgTiO<Subscript>3</Subscript> geikielite

We report here for the first time a novel method of preparing nano-crystalline metatitanate, MgTiO₃ geikielite, with crystalline size varying from 20–40 nm. The preparation has been carried out by coprecipitation method involving titanium hydroxide and magnesium nitrate solution. The samples were characterized by using transmission electron microscopic, powder XRD and FT-IR spectroscopic studies. The sample annealed at 900 K for 2 h show ten X-ray diffraction peaks corresponding to the pure geikielite phase. FT-IR spectra of the nano-crystalline geikielite exhibit strong broad vibrational bands near 1000, 650 and 470 cm⁻¹ arising from normal vibrations of the TiO₃ group.     

月球机器人高精度定位模糊神经网络直接自适应控制

针对常规模糊控制的不足,提出一种模糊神经网络直接适应控制,它结合了模型控制、神经网络控制和自适应控制的优点,实现了模糊控制的智能化,并将其应用于月球机器人的定位控制中。仿真证明了该方案的优越性、有效性和可行性。     

深空探测与我国深空探测展望

对人类已经开展的深空探测活动进行了回顾,简介了近期已开展和未来5年内将要开展的深空探测任务,以及未来主要航天国家的深空探测规划,提出了未来我国开展深空探测应掌握和突破的关键技术;介绍了我国深空探测的现状,对绕月探测工程和嫦娥1号进行了简介,重点介绍了探月工程二、三期的思路和二期工程的立项论证情况和初步总体方案,同时简要叙述了正在论证中的中俄联合火星探测、夸父计划、硬X射线天文望远镜和空间太阳望远镜等项目的概况;给出了对我国未来深空探测发展方向的思考和展望。［关键词］ 深空探测;行星际探测;多目标多任务;中国探月工程     

Modelling risk factors for injuries from dog bites in Greece: a case-only design and analysis

We conducted a study using a newly developed dataset based on Emergency Departments records of a network of hospitals from Greece on injuries from dog bites. Our goal is three-fold: (a) to investigate if surrogate factors of leisure time are associated with increased risk of injury from bites; (b) to address recently reported contradictory results on putative association of lunar periods and injuries from dog bites; and (c) to offer a general methodology for addressing similar case-only designs with combined factors of which some can exhibit cyclical patterns. To address these goals, we used a case-only design of our dataset, and conducted an analysis where we controlled simultaneously for weekday/weekend effects, season of year (winter, spring/fall, summer), and lunar periods, because any one of these factors can contribute to the degree of exposure to injuries from dog bites. We found that increased risk of injury from bites was associated with weekends versus weekdays (RR=1.19, 95% CI: 1.10-1.29), summer versus winter (RR=1.24, 95% CI: 1.11-1.39), and fall or spring versus winter (RR=1.31, 95% CI: 1.19-1.45). The results support the hypothesis that longer leisure time at these levels of factors does increase the risk of having a bite injury. Moreover, after controlling for these factors, risk of bite injury was not associated with moon periods, thereby also helping settle a longstanding argument.     

Mechanical Analysis and Performance Optimization for the Lunar Rover’s Vane-Telescopic Walking Wheel

It is well-known that optimizing the wheel system of lunar rovers is essential. However, this is a difficult task due to the complex terrain of the moon and limited resources onboard lunar rovers. In this study, an experimental prototype was set up to analyze the existing mechanical design of a lunar rover and improve its performance. First, a new vane-telescopic walking wheel was proposed for the lunar rover with a positive and negative quadrangle suspension, considering the complex terrain of the moon. Next, the performance was optimized under the limitations of preserving the slope passage and minimizing power consumption. This was achieved via analysis of the wheel force during movement. Finally, the effectiveness of the proposed method was demonstrated by several simulation experiments. The newly designed wheel can protrude on demand and reduce energy consumption; it can be used as a reference for lunar rover development engineering in China.     

Electrostatic collection of tribocharged lunar dust simulants

Levitation and consecutive deposition of naturally charged particles on lunar surface were troublesome in previous NASA explorations. Protecting sensitive surfaces from dust deposition in the limiting condition of the lunar atmosphere is imperative for future space exploration. This study reports experimental investigation of the collection efficiency of an electrostatic lunar dust collector (ELDC). A dual-functional remotely controlled particle charger/dropper was designed for tribocharging 20 μm lunar dust simulants, and a system of Faraday cup connected to an electrometer working in the nC range was used to measure the particle charges. Tribochargeability of two lunar dust simulants was studied, and the process was found to be the most effective with the JSC-1A samples. Aluminum was verified to be a more effective plate material than stainless steel. For the tested range of electrostatic field strength (0.66–2.6 kV/m), the mass-based and charge-based collection efficiencies were in the range of 0.25–1% and 0.45–1.45% for the low vacuum (10⁻¹ Torr), and 8–35% and 12–54% for the high vacuum (10⁻⁵ Torr) conditions. The linear relationship between the applied voltage and ELDC collection efficiency predicted by the theoretical model was confirmed, and the collection pattern of the collected particles over the collection plate was consistent with the previously computed charge distribution on the collection plate. Aside from validating the predictability of the theoretical model, this study offers a novel method of particle charging inside a vacuum chamber with a variety of applications for studying chargeability of particles at different temperatures and pressures.     

基于图像叙事的杨家埠木版年画数字文创设计研究

目的 基于图像叙事理论,以国家级非物质文化遗产杨家埠木版年画数字文创为研究内容,探索非遗文创产品设计创新路径,旨在助力非遗项目的活态传承与数字传播。方法 通过挖掘杨家埠木版年画的图像叙事特征,梳理杨家埠木版年画的图像素材与叙事主题,制定提炼叙事主题、设立表述层次、创设叙事场景、产品设计实践4个阶段的设计流程。根据用户移动社交行为与消费偏好,进行年画图像和角色IP的提取、转化及衍生品设计,建议利用数字文创打破非遗文化的传统圈层,拉近年画与年轻消费群体之间的距离。结论 研究杨家埠木版年画在数字媒体时代背景下的文创设计,提出应用场景个性化图像、角色IP延展等创作方式,有利于用户在网络社交过程中自觉融入非遗传播,营造弘扬中华优秀传统文化的良好氛围。     

Optimized trigger for ultra-high-energy cosmic-ray and neutrino observations with the low frequency radio array

When an ultra-high energy neutrino or cosmic-ray strikes the Lunar surface a radio-frequency pulse is emitted. We plan to use the LOFAR radio telescope to detect these pulses. In this work we propose an efficient trigger implementation for LOFAR optimized for the observation of short radio pulses.