In the design of a large deployable mesh reflector, high surface accuracy is one of ultimate goals since it directly determines overall performance of the reflector. Therefore, evaluation of surface accuracy is needed in many cases of design and analysis of large deployable mesh reflectors. The surface accuracy is usually specified as root-mean-square error, which measures deviation of a mesh geometry from a desired working surface. In this paper, methods of root-mean-square error calculation for large deployable mesh reflectors are reviewed. Concept of reflector gain, which describes reflector performance, and its relationship with the root-mean-square error is presented. Approaches to prediction or estimation of root-mean-square error in preliminary design of a large deployable mesh reflector are shown. Three methods of root-mean-square error calculation for large deployable mesh reflectors, namely, the nodal deviation root-mean-square error, the best-fit surface root-mean-square error, and the direct root-mean-square error, are presented. Concept of effective region is introduced. An adjusted calculation of root-mean-square error is suggested when the concept of effective region is involved. Finally, these reviewed methods of root-mean-square error calculation are applied to surface accuracy evaluation of a two-facet mesh geometry, a center-feed mesh reflector, and an offset-feed mesh reflector for demonstration and comparison.

Pressure vessels are subjected to deterioration and damage, which can significantly reduce their strength and loading capabilities. Among several procedures nowadays available to repair damaged steel pipelines, composite-repairing systems have become popular over the past few years to restore the loading capacity of damaged pipelines. This study reports a numerical-experimental investigation performed for a composite-repaired pipeline made of API 5L X60 steel. An experimental burst test was carried out on a 4 m long pipe section, closed by two lateral caps, and tested up to failure by means of high-pressure water. In parallel, the test was numerically replicated through a FEM model of the composite-repaired steel tank, allowing for a cross-comparison of results. It was found that the composite repairing system has almost eliminated both the noteworthy thickness reduction of 80% and the related stress concentrations in the pipe body. These outcomes allow for a better understanding of these repairing procedures in order to drive their subsequent optimization.

In recent years, the utilization of 3D modeling for various robotic systems has gained significant traction, serving educational, research, and diverse applications. Presently, there are a multitude of 3D modeling tools tailored to different facets of robotic research, each possessing distinct advantages and limitations. This paper presents the development of novel algorithms and software aimed at constructing 3D representations of robotic arms that have enabled the visualization of the manipulator and its links’ motion. These algorithms allow for the depiction of forward kinematic outcomes through spatial 3D graphs. Consequently, these graphical representations provide a tangible means to observe the changes in module components and parameter orientations as the manipulator assumes different spatial configurations. Within the Maple environment, a comprehensive 3D model of robotic arms was constructed, and the forward kinematic problem was solved for a manipulator that had five degrees of freedom (DoF). This endeavor was achieved by implementing the Denavit-Hartenberg method to elucidate kinematic characteristics and the Newton-Euler method to ascertain the velocity and acceleration of the robot manipulator’s links. The newly created algorithms and software are expected to be widely used in 3D modeling of robotic manipulators as scientific research in industries and other complex mechanical systems.

Large deployable mesh reflectors (DMRs) play a vital role in spaceborne communication and observation systems because of their low mass and compact stowage capability. Nevertheless, maintaining stringent surface accuracy while mitigating pronounced thermal influences in the orbital environment remains a persistent engineering challenge. This study develops a spatially discretized thermal modeling framework that incorporates direct solar radiation, Earth albedo, a prescribed equivalent Earth‐infrared heat input, section‐dependent solar‐exposure factors, structural self‐shadowing, and reflector emission to space. The proposed method is implemented to modeling of an 817‐node center‐feed reflector and an 849‐node offset‐feed reflector. Each reflector is discretized into one to 10 spatial sections and analyzed over four idealized geostationary‐orbit eclipse‐season cycles. Temperature distributions are evaluated at representative spatial nodes, and the influence of spatial discretization is quantified using normalized absolute temperature differences referenced to the 10‐section model. For the center‐feed reflector, the section‐dependent temperature field is further converted into thermal strains and thermally modified stress‐free cable lengths, and the resulting shape distortion of its reflecting surface is evaluated using the direct root‐mean‐square surface error.