The identification and estimation of space non-cooperative targets are prerequisites for space rendezvous and docking, and in-orbit capture missions. In this paper, a method for six-degree-of-freedom attitude estimation of spatial noncooperative target based on conformal geometric algebra(CGA) framework was be proposed. Firstly, we use a construction method of straight lines in CGA to fit straight lines to the points on the outer contour of the single-frame point cloud of the noncooperative target. Secondly, we fit the points on the straight line to a circle by spherical inversion in CGA. Finally, the transformation relationship between the point cloud sequences is solved by constructing a minimization distance objective function to obtain real-time six-degree-of-freedom attitude information of the noncooperative target. Both numerical simulation experiments and semi-physical experiments demonstrate the effectiveness of our proposed method, with the estimation error of the attitude angle less than 1.8° and the translation error less than 0.1m.
Estimation of (in)efficiency became a popular practice that witnessed applications in virtually any sector of the economy over the last few decades. Many different models were deployed for such endeavors, with Stochastic Frontier Analysis (SFA) models dominating the econometric literature. Among the most popular variants of SFA are Aigner, Lovell, and Schmidt (1977), which launched the literature, and Kumbhakar, Ghosh, and McGuckin (1991), which pioneered the branch taking account of the (in)efficiency term via the so-called environmental variables or determinants of inefficiency. Focusing on these two prominent approaches in SFA, the goal of this chapter is to try to understand the production inefficiency of public hospitals in Queensland. While doing so, a recognized yet often overlooked phenomenon emerges where possible dramatic differences (and consequently very different policy implications) can be derived from different models, even within one paradigm of SFA models. This emphasizes the importance of exploring many alternative models, and scrutinizing their assumptions, before drawing policy implications, especially when such implications may substantially affect people's lives, as is the case in the hospital sector.
In the calculation of process dimensions in the machining of porous parts, the traditional method is complicated in the establishment of the dimensional chain, it is easy to make mistakes in the judgment of increasing and decreasing loops, and there is difficulty in the calculation process; thus, this paper puts forward a method that combines the process path with the design path to analyze the hole system dimensions in response to these problems. First of all, the combination of the process path and design path is used to establish a system of vector equations and, according to the system of vector equations, to establish a matrix model to calculate the process dimensions based on the system of vector equations to construct the process dimensional chain and the dimensional chain function; then, the principle of differentiation is used to carry out a tolerance analysis of the process dimensions, which avoids the drawing of dimensional chain diagrams and the judgement of the incremental/decremental loops. Finally, the development of a process dimension analysis tool for hole system dimensions is completed based on CATIA CAA. In order to verify the effectiveness of the proposed method, the analysis tool was used to solve the three labeling methods of the hole system dimensions of porous parts and compared with the results calculated using the traditional method, and it was found that some of the tolerance results obtained by the proposed method were enlarged by about 50%, which is more in line with the actual production situation. Finally, in order to verify the accuracy of the tool’s calculation results, three porous parts were machined according to the process dimensions and tolerances calculated by the tool, and the center distance of each hole was measured by a coordinate meter. These measurements were compared and analyzed with the design dimensions specified in the engineering drawings, and it was found that the center distances of the holes were in full compliance with the design requirements.
In flexible solar arrays, stranded hybrid-metal conductors and micro-foil interconnectors are preferred materials for energy transmission due to their high conductivity, flexibility and lightweight. However, achieving high-quality joints in parallel gap resistance welding (PGRW) between the stranded conductor and interconnector is challenging due to the complex microstructure formation at multiple interfaces. This study aims to clarify the correlation between interfacial microstructures and joint properties while elucidating the formation mechanisms of the interfacial microstructures. A shift in the bonding mechanism at interfaces from solid-state diffusion to brazing was found as the welding voltage reached a critical value of 1.5 V. The brazing-based bonding eliminated micro gaps while building nano-scale interlocking structures, resulting in substantial improvement in the mechanical properties of joints. Increasing the welding voltage from 1.2 V to 1.4 V was beneficial for the improvement in electrical conductivity due to the enlarged bonding area at interfaces. However, high welding voltage (1.6 V) led to degradation in the electrical conductivity of joints due to excessive Ag-Cu solid solution formed at interfaces. The key to fabricating high-strength and high-conductivity joints lies in achieving appropriate interfacial melting while reducing alloying by controlling peak temperature and shortening the duration above the Ag-Cu eutectic point.
Cet article offre un nouveau point de vue sur l’enseignement de la littérature en didactique du FLE, notamment avec les apprenants sinophones. Il s’agit d’introduire une perspective cognitive dans la lecture littéraire. L’objectif est d’une part, d’établir une interaction et une intercompréhension entre les systèmes langagiers de la langue en cours d’apprentissage et de la langue maîtrisée par les apprenants sinophones, et d’autre part, de construire le sens du texte littéraire, en recourant à la fois aux pensées de l’auteur et au vécu du lecteur. Dans cette optique, les textes littéraires sont considérés comme un support pédagogique où beaucoup de possibilités linguistiques, interculturelles et motivationnelles s’inscrivent. Et pour les apprenants sinophones, ils deviennent aussi un étayage pour surmonter les décalages linguistiques et culturels entre la France et la Chine.
For the study of alumina ceramic micro turning machining performance, using (IPGPhotonis) fiber laser heating assisted cutting. Due to the high strength and hardness of the alumina ceramics, using cubic boron nitride (CBN) tool for turning experiment. The effects of different processing parameters such as laser power, spindle speed and feed rate on the surface roughness and tool wear were studied. Compared with the experimental results obtained by laser heating and non-laser heating, we found that the surface quality is improved by laser heating, and the service life of the cutter is prolonged.
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