Influence of the gravitational vertical on geometric visual illusions

The occurrence of geometric orientation illusions and the perception of ambiguous figures were analyzed in 24 subjects during static body tilt relative to gravity on Earth. Results showed that illusions such as the Rock's diamond/square, the Ponzo illusion, and orientation contrast illusions occurred less frequently, and that depth reversal of ambiguous figures took more time when subjects were lying on their side or supine compared to upright, thus suggesting that the gravitational reference plays a significant role in these “visual” illusions. The structure of images, our representation of the environment, and orientation relative to gravity are all integral parts in interpreting visual images. In a weightless environment where no gravitational reference can be used, it is expected that similar alterations in visual perception will occur.     

Critical wake vortex encounter scenarios

A simulation-based method was developed to investigate the severity of Wake Vortex Encounters (WVEs). This paper describes an important part of this method: the determination of worst-case WVE conditions, which is referred to as Worst-Case Search (WCS). The WCS results permit to reduce time and costs of WVE severity related piloted simulator tests and allow the comparison of the hazard that vortices of different generator aircraft exert on a follower aircraft.The WCS is based on a high fidelity, offline simulation of the follower aircraft that includes the interacting wake vortex, a hazard criterion that rates the severity of each WVE, and a pilot model. It can be formulated as an optimisation problem that is solved with the optimisation tool MOPS (Multi Objective Parameter Synthesis). MOPS varies the encounter geometry until the simulation yields maximum values of the WVE hazard criterion.Worst-case encounter conditions for different parameters were investigated and sensitivity studies performed. The influence of the height above ground, the core radius, and the models for the wake vortex velocity profiles on the severity of a WVE was examined. To show the capability of the method, a comparison of the severity of a WVE behind two different heavy transport aircraft for a 20 t aircraft was made. The WCS method demonstrated its applicability and delivered the worst-case encounter geometry.

Zusammenfassung

Zur Untersuchung der Heftigkeit von Wirbelschleppen wurde eine simulationsbasierte Methode entwickelt. Dieser Beitrag beschreibt einen wichtigen Bestandteil dieser Methode: die Bestimmung der ungünstigsten (worst case) Einflugbedingungen in die Wirbelschleppe. Die Kenntnis dieser Bedingungen gestattet eine Zeit- und Kostenreduzierung bei wirbelschleppenbezogenen Simulatorversuchen mit Piloten und ermöglicht gleichzeitig einen Vergleich der vom Wirbel ausgehgehenden Gefährdung für verschiedene Kombinationen voraus- und einfliegender Flugzeuge.Die Worst-Case-Bedingungen werden mit einer Offline-Simulation des Folgeflugzeugs bestimmt, die Modelle für die Wechselwirkung mit der Wirbelschleppe und für das Pilotenverhalten sowie Kriterien für die Gefährdung durch den Wirbel umfasst. Für die Steuerung der Simulation und die Worst-Case-Suche wird die Optimierungssoftware MOPS (Multi Objective Parameter Synthesis) verwendet. MOPS variiert die Geometrie des Wirbelschleppendurchflugs bis die Simulation die maximalen Kriterienwerte für die Gefährdung durch den Wirbel liefert.Die Worst-Case-Bedingungen wurden für unterschiedliche Parameter untersucht. Der Einfluss der Höhe über Grund, des Kernradius' und der unterschiedlichen Modelle für das Wirbelgeschwindigkeitsprofil auf die von den Wirbelschleppen ausgehenden Gefährdung wurde dabei ermittelt. Um die Leistungsfähigkeit der Methode zu demonstrieren, wurde die Gefährdung von Wirbelschleppen zweier generierender Flugzeuge (heavy class) auf ein nachfolgendes 20 t Transportflugzeug verglichen. Die Anwendbarkeit der Methode wurde bestätigt und die ungünstigsten Einflugbedingungen berechnet.     

Predictive fault-tolerant control of an all-thruster satellite in 6-DOF motion via neural network model updating

The problem of controlling an all-thruster spacecraft in the coupled translational-rotational motion in presence of actuators fault and/or failure is investigated in this paper. The nonlinear model predictive control approach is used because of its ability to predict the future behavior of the system. The fault/failure of the thrusters changes the mapping between the commanded forces to the thrusters and actual force/torque generated by the thruster system. Thus, the basic six degree-of-freedom kinetic equations are separated from this mapping and a set of neural networks are trained off-line to learn the kinetic equations. Then, two neural networks are attached to these trained networks in order to learn the thruster commands to force/torque mappings on-line. Different off-nominal conditions are modeled so that neural networks can detect any failure and fault, including scale factor and misalignment of thrusters. A simple model of the spacecraft relative motion is used in MPC to decrease the computational burden. However, a precise model by the means of orbit propagation including different types of perturbation is utilized to evaluate the usefulness of the proposed approach in actual conditions. The numerical simulation shows that this method can successfully control the all-thruster spacecraft with ON-OFF thrusters in different combinations of thruster fault and/or failure.     

Coordinating signs and eye gaze in the depiction of directions and spatial scenes by fluent and L2 signers of Norwegian Sign Language

The current study investigates the coordination of signs and eye gaze during depictions of directions and spatial scenes by fluent and second language (L2) signers of Norwegian Sign Language. First, findings show that fluent and L2 signers make different choices regarding the perspective they use to depict spatial scenes. Second, there is variation within and across groups in relation to how eye gaze is directed during these depictions. Findings suggest that eye gaze is used to establish a vantage point upon a depicted scene, but L2 learners may not always engage in this type of coordination. This study contributes to our understanding of how visual perspective is depicted in signed languages and has implications for signed language pedagogy.     

一种基于语义信息辅助的无人机视觉/惯性融合定位方法CSCD

视觉传感器在无人机室内定位中发挥着重要作用。传统基于特征点的视觉里程计算法通过底层亮度关系进行描述匹配,抗干扰能力不足,会出现匹配错误甚至失败的情况,导航系统的精度及鲁棒性有待提升。由于室内环境存在丰富的语义信息,提出了一种基于语义信息辅助的无人机视觉/惯性融合定位方法。首先,将室内语义信息进行因子建模,并与传统的视觉里程计方法进行融合;然后,基于惯性预积分方法,在因子图优化中添加惯性约束,以进一步提高无人机在动态复杂环境下的定位精度和鲁棒性;最后,通过无人机室内飞行试验对算法的定位精度进行了分析。试验结果表明,相较于传统的视觉里程计算法,该方法具有更高的精度和鲁棒性。     

Improvement of forebody/inlet integration for hypersonic vehicle

Results of a numerical (CFD) study of the influence of the forebody shape on local flow parameters at a bottom-mounted inlet entrance are presented. The free-stream Mach number is assumed to be 3.5–7.0. Some recommendations on forebody shape optimization are provided. Main characteristics of the air inlet are evaluated.     

United Nations Human Space Technology Initiative (HSTI)

The Human Space Technology Initiative was launched in 2010 within the framework of the United Nations Programme on Space Applications implemented by the Office for Outer Space Affairs of the United Nations. It aims to involve more countries in activities related to human spaceflight and space exploration and to increase the benefits from the outcome of such activities through international cooperation, to make space exploration a truly international effort.     

精神分析视角下的斯佳丽叛逆性格分析

精神分析学中的基本焦虑理论和强迫性重复理论认为早期经历对个体人格形成和性格塑造具有非常重要的影响。幼儿由于父母无法满足其对安全和满足的需求而引发基本焦虑．为了对抗基本焦虑形成特定的心理模式,然后不自觉地在以后的人生中不断重复这些模式,形成强迫性重复。论文通过对《飘》的主人公斯佳丽幼年亲子关系及其早期经历的分析,探讨了斯佳丽的强迫性重复模式形成的原因,以及这些模式对斯佳丽的叛逆性格的形成造成的影响。     

采用新型基准流场的高超声速内收缩进气道性能分析

通过改变中心体形状,设计了新型轴对称基准流场,可显著降低反射激波强度,明显提高压缩效率。基于该基准流场和传统基准流场,分别设计了两个圆形出口内收缩进气道,并对二者的流场及总体性能进行了数值研究。结果表明,新的进气道设计点和接力点肩点附近激波附面层相互作用减弱,流场结构优于传统进气道,压缩效率明显提高,同时进气道起动性能得到改善。     

钛合金六角头螺栓头部成形过程的有限元分析

航空用螺栓的头部多样、形状复杂,通常情况下利用镦锻工艺成形。研究采用塑性成形仿真软件,针对Ti-6Al-4V六角头螺栓的头部成形过程进行了有限元模拟,对成形各阶段的应力、应变、温度变化以及材料流动情况进行了分析,同时对成形过程中的缺陷进行了预测,为工艺设计和改进提供了依据。