Calculation of the Shaping of a Space Umbrella Antenna During Strong Bending of Radial Rods Connected Along Parallels by Tensile Cables

Abstract— A cyclically symmetric umbrella antenna is considered, the frame of which consists of flexible inextensible radial rods connected in nodes along parallels by tensile cables. In the initial transport position, the multilink rods are packed in packages oriented in the direction of the system axis. After the packing ties are removed, the rods are deployed in radial planes under the action of elastic springs connecting the links, and are fixed in rectilinear positions at a given angle with respect to the axis, at which all cables connecting the same type of rod nodes take the form of regular polygons, while remaining loose. Further, under the action of the force of a damping hydraulic cylinder with pre-compressed springs, the root parts of all rods are slowly turned to the stops. In the final position, the radial rods, connected at the nodes by tensioned cables, take a curved shape. The tensile stiffnesses of the cables are determined so that the radial and axial coordinates of the nodes of the curved rods coincide with the coordinates of the points of the given surface of revolution. A model of strong bending of a flexible inextensible rod is constructed taking into account the unknown radial reactions of tensioned cables acting on it at the nodes. The links of the rod are considered as “cantilever” elements connected in series at the nodes in local coordinate systems, which can make large displacements and turns. The bending of each element is described by two specified functions, the shrinkage of the element due to bending is taken into account in a quadratic approximation. The obtained nonlinear deformation equations of the system, taking into account the geometric connections at the nodes, are solved by the method of successive approximations with respect to the unknown reactions of the cables. The obtained values of the reactions are then used to determine the required tensile stiffness of the cables at the given coordinates of the nodes. As an example of the calculation, a parabolic antenna is considered for various numbers of radial rods and components of links. The estimates of the accuracy of the proposed computational model of the antenna shaping are carried out.

ACE2, the Counter-Regulatory Renin–Angiotensin System Axis and COVID-19 Severity

Angiotensin (ANG)-converting enzyme (ACE2) is an entry receptor of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that causes coronavirus disease 2019 (COVID-19). ACE2 also contributes to a deviation of the lung renin–angiotensin system (RAS) towards its counter-regulatory axis, thus transforming harmful ANG II to protective ANG (1–7). Based on this purported ACE2 double function, it has been put forward that the benefit from ACE2 upregulation with renin–angiotensin–aldosterone system inhibitors (RAASi) counterbalances COVID-19 risks due to counter-regulatory RAS axis amplification. In this manuscript we discuss the relationship between ACE2 expression and function in the lungs and other organs and COVID-19 severity. Recent data suggested that the involvement of ACE2 in the lung counter-regulatory RAS axis is limited. In this setting, an augmentation of ACE2 expression and/or a dissociation of ACE2 from the ANG (1–7)/Mas pathways that leaves unopposed the ACE2 function, the SARS-CoV-2 entry receptor, predisposes to more severe disease and it appears to often occur in the relevant risk factors. Further, the effect of RAASi on ACE2 expression and on COVID-19 severity and the overall clinical implications are discussed.

APPLICATION OF AN OPTIMAL CONTROL ALGORITHM FOR A GYROSCOPE SYSTEM OF A HOMING AIR-TO-AIR MISSILE

Missile homing precision depends mainly on the correct determination of the current angle between the Gyroscope System Axis (GSA) and the target line-of-sight (LOS). A gyroscope automatic control system shall ensure spontaneous levelling of this angle, hence, constant homing of the gyroscope system axis in on the LOS, i.e. tracking the target by the head. The available literature on the subject lacks a description of how to use the controlled gyro system in the process of guiding the missile onto the target. In this paper, the authors present the original development of an optimal control algorithm for a gyro system with a square quality indicator in conditions of interference and kinematic influence of the missile deck. A comparative analysis of the LQR with the PD regulator was made. PD regulator parameters are also selected optimally, using the Golubencev method, so that the transition process of the homing system fades over a minimal time, while simultaneously ensuring the overlapping of the gyroscope axis with the target line-of-sight. The computer simulation results have been obtained in a Matlab-Simulink environment and are presented in a graphic form.

PERANCANGAN MESIN GERGAJI KAYU UNTUK PERAJIN PALLET KAYU

Technology at all times continues to grow along with the progress of the times, not least in the furniture industry. In the development of timber techniques demands a quality product, it needs an effective and efficient process. This is also the underlying work of cutting timber. Initially the cutting of the wood was done manually by utilizing manpower and then changed using a whipsaw. The rapid development of technology makes hand saws rarely used and switches using sawing machines and saw tables. From the results of the design process of wood sawing machine summed up some things as follows: Dimensions of wood cutting machine 1500 × 1000 × 800 mm, saws used in circular or cyrcle wood cutting machine with a circular motion saw blade, The rotation is passed from the motor to the saw blade is not in the fox and using the same pulleys of 74 mm diameter, wood cutting machine using 2Hp power, the level of safety on the wood cutting machine after theoretical calculations ranging from the transmission system, axis, and frame that is 9.524 m / sec belt speed is said to be good because ≤ 30 m / sec. The axle is said to be safe because the shear stresses that occur in the shaft are smaller than the allowable shear stress of , and on the framework of the wood cutting machine the yield of the voltage is less than the yield strength material of 7,888 Mpa ≤ 207 MPa with deflection 0,096 mm, In transmission belt V used is V type A42 belt, Image modification work of wood cutting machine used for machine making process contained in attachment.

AXIS—An Autonomous Expendable Instrument System

Expendable bathythermographs (XBT) to profile upper-ocean temperatures from vessels in motion have been in use for some 50 years now. Developed originally for navy use, they were soon adapted by oceanographers to map out upper-ocean thermal structure and its space–-time variability from both research vessels and merchant marine vessels in regular traffic. These activities continue today. This paper describes a new technology—the Autonomous Expendable Instrument System (AXIS)—that has been developed to provide the capability to deploy XBT probes on a predefined schedule, or adaptively in response to specific events without the presence of an observer on board. AXIS is a completely self-contained system that can hold up to 12 expendable probes [XBTs, XCTDs, expendable sound velocimeter (XSV)] in any combination. A single-board Linux computer keeps track of what probes are available, takes commands from ashore via Iridium satellite on what deployment schedule to follow, and records and forwards the probe data immediately with a time stamp and the GPS position. This paper provides a brief overview of its operation, capabilities, and some examples of how it is improving coverage along two lines in the Atlantic.