Single Reflect-Mirror Laser Communication Tracking-Pointing System Load Technology for Micronanosatellite

In order to realize low-orbit microsatellite laser communication, L- and U-frame structures are designed, respectively, for the payload of single-lens reflex (SLR) laser communication tracking and pointing system. According to the characteristics of each load structure, the detailed system design is carried out, and the modal analysis is carried out on the key structural parts of the L- and U-frames to ensure the reliability of each load structure. The pointing accuracy of the two load structures is also calculated and analyzed. Finally, the conclusion is that both of the two load structures can meet the technical and accuracy requirements of low-orbit communication, but obviously, the U-frame structure has higher accuracy, greater pitching angle, and better reliability; eventually, the U-frame structure is adopted in this design. Then, we have completed the manufacture and assembly of the principle prototype and carried out a vibration test experiment on the principle prototype. The results show that the U-type loading structure SLR laser communication tracking and pointing system achieves the expected design purpose and can meet the technical requirements of the low-orbit microsatellite laser communication.

Valuation of construction work on architectural heritage and its influence on project implementation decision

The article deals with the description of the methodology for determining the prices of construction work used most often in the reconstruction of historic buildings. The procedure is based on parametric estimating of buildings and on traditional tools and principles of pricing. The historic building is divided into structural parts and technological units. Structural elements are individually valued at the unit price, which was created on the basis of sub-budget. Very strict rules are set for the financing of cultural monuments and the method of valuation is based on the price systems’ methodology. The research also included an analysis of market prices and a subsequent comparison with indicative prices. Proper estimate of historic buildings’ reconstruction cost is also an important input for the decision-making process regarding the actual implementation of the project, its method of execution and its life cycle cost determination.

The resistance of plants of Juglans nigra varieties to the influence of the low temperature

The results of research on the influence of low temperatures on the structural parts of shoots of three varieties and a hybrid of domestic and foreign selection of black walnut in the conditions of cultivation of the Liso-steppe and Polissya of Ukraine are highlighted. It was found that the core of the shoot, depending on the year of vegetation, and the buds were damaged the most by low temperatures on average during three years of research. The most resistant to low temperatures were the tissues of the bark and cambium, of the varieties — plants The highlight of the garden. This variety can be used for breeding work for winter hardiness to obtain stable forms.

Review of the Book “Historical Memory in Social Media” by Sophia Tikhonova, Denis Artamonov

The subject of review is the book “Historical Memory in Social Media” by Sofya Tikhonova and Denis Artamonov. In the book, the authors focus on the design and specification of the production of images of the past on the Internet and the gaming industry, referring to various materials, from text “fake” messages and memes to computer games. Research is not limited to the description of empirical data. The supporting structure of the research is the author's concept of digital history and digital philosophy of history. Research optics is aimed at determining the status of the digital subject of history, which seems to be an acute anthropological and socio-philosophical problem. The book discusses the issues of modification of the politics of memory, the production of “fakes”, the connotation of historical events, the trend of miniaturization of history and the crisis of great narratives. Considerable attention is paid to the everyday everyday practices of information production, woven into the context of “history making”. The review pays attention to all the main structural parts of the book and reproduces the logical sequence of the key ideas of the text. With references to the original author's text, the reviewer also gives his own interpretations of the conceptual and terminological innovations of the book, and also focuses on some controversial aspects of the research.

Case study on application of digital radiography in cable

Because of the frequent occurrence of power cable fault, rapid and accurate fault diagnosis is an important subject in this field. In this paper, the DR detection cases of cables and related components with different voltage levels are described and analyzed based on the research work of radiographic detection carried out by our research group in the field of cables and their accessories in the recent three years. The results show that the technology can effectively detect and analyze the internal damage of cable outer breaking point, the ablative defect of cable buffer layer, the size and position deviation of cable joint. Due to the large number of cable layers and material types, the paper also gives some solutions to the problem of shielding copper core and some examples of abnormal image identification. Cable ontology, cable joints and other accessories produced by different manufacturers have certain structural differences due to numerous processes and procedures. It is necessary to continue to carry out research on DR testing for cable engineering structural parts of different types, establish relevant standard comparison atlas and provide reference for the application of DR technology in the field of cable testing.

A Data-driven Minimum Stiffness Prediction Method for Machining Regions of Aircraft Structural Parts

Large thin-walled structural parts have been widely used in aircrafts for the purpose of weight reduction. These parts usually contain various thin-walled complex structures with weak local stiffness, which are easy to deform during machining if improper cutting parameters are selected. Thus, local stiffness has to be seriously considered during the machining parameter planning. Existing stiffness calculation methods mainly include mechanics calculation methods, empirical formula methods, finite element methods, and surrogate-based methods. However, due to the structural complexity, these methods are either inaccurate or time consuming. To address this issue, this paper proposes a data-driven method for stiffness prediction of aircraft structural parts. First, machining regions of aircraft structural part finishing are classified into bottom, sidewall, rib and corner to further define the minimum stiffness of machining regions. Then, by representing the part geometry with attribute graph as the input feature, while computing the minimum stiffness using FEM as the output label, stiffness prediction is turned to a graph learning task. Thus, a graph neural network (GNN) is designed and trained to map the attribute graph of a machining region to its minimum stiffness. In the case study, a dataset of aircraft structural parts is used to train four GNN models to predict the minimum stiffness of the defined four types of machining regions. Compared with FEM results, the average percentage errors on the test set are 6.717%, 7.367%, 7.432% and 5.962% respectively. In addition, the data driven model once trained, can greatly reduce the time in predicting the stiffness of a new part compared with FEM, which indicates that the proposed method can meet the engineering requirements in both accuracy and computational efficiency.

Development of a Novel Hybrid Thermoplastic Material and Holistic Assessment of Its Application Potential

Τhe development of a novel hybrid thermoplastic prepreg material enabling the fabrication of next-generation recyclable composite aerostructures produced by affordable, automated technologies is presented in the present work. The new hybrid material is produced using automated equipment designed and developed for this reason. A preliminary assessment of the application of the new material is made to obtain material properties related to its processability as well as to its strength. A typical aeronautical flat skin panel has been identified and produced using an autoclave-based process in order to assess the potential of the new material for producing aircraft structural parts. Moreover, a newly developed holistic index is implemented to enable a more holistic comparison of the suitability of the materials used for the panel production. The aspects considered for the material comparison are the quality, the environmental footprint, and the cost. The results of the study pointed out that the hybrid thermoplastic material that has been developed represents a viable manufacturing option from an industrial point of view and that its implementation in structural component manufacturing leads to clear cost and environmental advantages.

An Approach to Variation Simulation of Final Aircraft Assembly with Presence of Sealant

The article discusses the process of aeronautical structure assembly in the presence of a sealant between the parts to be joined. An attempt to estimate the influence of sealant on assembly quality in terms of variation analysis is presented. The sealant is considered as a highly viscous liquid that is applied to the surfaces of the assembled parts before the start of final assembly. The modeling approach is based on simulation of two-way coupled fluid-structure interaction between fluid sealant and compliant structural parts. Reynolds lubrication approximation is used in the fluid dynamics problem and variational formulation of contact problem combined with static condensation is used in the structural one. The joining of two aircraft panels is used as a numerical test for demonstration of developed approach. Various phenomena connected with the presence of sealant are demonstrated. In particular, the difference in the fastener loosening due to sealant flow between different types of fasteners is investigated. Results of variation simulation show that presence of sealant should be considered among determining factors in the analysis of assembly quality.

Dynamically Balanced Pointing System for CubeSats: Study and 3D Printing Manufacturing

The increasing presence of additive manufacturing (AM) in the space sector prompted us to investigate the feasibility of a single degree of freedom (DoF) pointing system (PS) made by means of a compound planetary gear train system (C-PGTS) integrating a dynamic balancing system (DBS) and entirely realized in AM. We analyzed in detail the dynamics of the system dealing with the design and the realization of the prototype. Of fundamental importance for this paper is the careful selection of materials for AM suitable for the prohibitive conditions of space. The results, deriving from the comparison between the experimental part and the simulations, underline the correct dimensioning of the PS and the fundamental importance of DBS in maintaining the satellite attitude. The results also confirm the capabilities of AM in the production of complex mechanical systems, allowing high precision, combined with interesting mechanical properties and low weight.This suggests the potential of AM in the space domain, both for structural parts and active components, such as those listed in this work.