Journal articles on the topic 'Orbit Motor'
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1
Mishev, A., and T. Stehle. "CFD-Analyse zur Leistungssteigerung eines Orbit-Motors*/CFD investigation of the performance of an orbital motor - CFD investigation of the influence of the rotor teeth number and eccentricity on the performance of an orbital motor." wt Werkstattstechnik online 105, no. 06 (2015): 433–39. http://dx.doi.org/10.37544/1436-4980-2015-06-85.
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Vorgestellt wird ein neuer Orbit-Motor mit innovativem Rotor-Design. Der Motor wurde grundlegend mit der Methode „Computational Fluid Dynamics (CFD) Analysis“ (numerische Strömungsmechanik) simulativ untersucht und entwickelt. Sechs volle dreidimensionale transiente CFD-Orbit-Motor-Modelle wurden entwickelt und mit dem CFD-Modell eines Standard-Orbit-Motors verglichen. Dabei weisen die CFD-Simulationsergebnisse für die neuen Orbit-Motoren-Modellvarianten einen deutlichen Anstieg des Motordrehmoments sowie wesentlich geringere Druck- und Gasvolumen-Anteil-Pulsationen gegenüber dem Standard-Orbit-Motor auf. In this paper a new orbital motor with innovative rotor design is presented and fundamentally investigated by means of CFD analysis. Six full 3D transient CFD orbital motor models were designed and compared to a standard orbital motor. The results from the simulation showed a substantial increase of the motor torque and reduction of the pressure ripple and gas volume fraction ripple of all six models. Furthermore the flow rate and the volumetric efficiency of all orbital motor models were predicted.
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RAJA, M., Gaurav ASTHANA, Ajay SINGH, Ashna SINGHAL, and Pallavi LAKRA LAKRA. "Orbit Design and Trajectory Analysis of satellite in Low Earth Orbit." INCAS BULLETIN 13, no. 1 (March 5, 2021): 159–72. http://dx.doi.org/10.13111/2066-8201.2021.13.1.17.
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An Attitude control system for a satellite in low earth orbit is designed in this project. As a reference, CARTOSAT-2 is selected to design the AOCS. CARTOSAT-2 is located in LEO so it suits the needs of the projects. It is mainly used for mapping of urban, rural areas and wetlands in India. To design a basic AOCS, a DC motor based model is considered. Transfer functions of DC motor and satellite dynamics model are calculated using Laplace transformation. Stability of the system is checked by plotting poles and zeroes of the systems. PID controller is used to improve the overall stability of the system by decreasing the errors in the output of the system. The systems are subjected to sine and step inputs and responses are plotted in the form of graphs. The plots are studied using SciLab as the tool to design the block diagram and the control system for the AOCS. Scilab along with FlightGear is used to visualize the response of the system.
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Salmin, V. V., V. V. Volotsuev, and A. V. Nikitin. "Analysis of characteristics of electric propulsion systems intended for carrying out maneuvers of maintenance of low Earth working orbit of small satellites." VESTNIK of Samara University. Aerospace and Mechanical Engineering 20, no. 3 (December 1, 2021): 65–76. http://dx.doi.org/10.18287/2541-7533-2021-20-3-65-76.
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An analysis of the mass of the working fluid and motor operating time of electric propulsion systems applied as a part of small spacecraft to carry out maneuvers of maintenance of the low Earth working orbit is carried out. The analysis is carried out for the small spacecraft with the weight in the range from 300 to 1000 kg functioning in working orbits with the height in the range from 400 to 600 km. When carrying out the analysis the values of the specific impulse of the propulsion system in the range from 800 to 1600 sec were accepted. Procedural guidelines for assessing the value of the required characteristic speed depending on the aerodynamic drag force, as well as for assessing the value of mass of the working fluid with account for the value of the specific impulse and defining the motor operating time of the propulsion system depending on the exhaust speed of the working fluid were used. The results of calculations given in the article show that the mass of the working fluid and the motor operating time vary depending on the height of the orbit and the mass of the small spacecraft and allow making quick preliminary assessment of the main design characteristics of the electric propulsion engines used to carry out maneuvers of maintenance of the low Earth working orbit of small spacecraft with different weight dimension characteristics during the prescribed term of active existence.
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Kamel, O. M., and A. S. Soliman. "Velocity corrections in generalised Hohmann and bi-elliptic transfer orbits." Aeronautical Journal 106, no. 1064 (October 2002): 555–58. http://dx.doi.org/10.1017/s0001924000018170.
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AbstractFor generalised Hohmann and bi-elliptic transfer orbits, we applied small tangential impulses at peri-apse and apo-apse to acquire the precise destination elliptic orbit stemming from an initial orbit. There are four cases for this correctional or improvement process. We take into consideration the first configuration for the time being. We determined the four relationships connecting the increments in major axes and eccentricities with the correctional increments in velocities ΔvA, ΔvB at points A, B for the generalised Hohmann case. We assigned the three relationships - for the bi-elliptic transfer - connecting slight changes in major axes with small increments in velocities at points A, B, C due to motor thrusts.
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Nag, Abhijit, Harish Ramachandran, and Aditya Shriwastava. "Optimization of the interference parameters of an Orbit motor using genetic algorithm." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 234, no. 22 (May 23, 2020): 4478–92. http://dx.doi.org/10.1177/0954406220924700.
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In the present study, the leakage of fluid due to gap generation at the contact points is eliminated by introducing interference between the rotor and the stator of an Orbit motor. Interference is incorporated in the system by modifying the roller radius, the chordal thickness, and the pitch circle radius. In an Orbit motor of interference-fit type, the contact points and the rotor center deviate from their original positions as found in an Orbit motor of perfect-fit type. A corrective technique based on minimization of the potential energy of the system is used to obtain the rotor center of an interference-fit motor. The rotor profile is initially generated around the geometrically obtained center of a perfect-fit motor. It is then shifted in the direction of decreasing potential energy, until the rotor center corresponding to minimum energy is attained. The main drawback of introducing interference is the generation of an unbalanced torque which affects the output torque of the motor. Thus, optimization of interference parameters using genetic algorithm is carried out to determine a system for which no gap is generated at the contacts and simultaneously it is ensured that the unbalanced torque ripple amplitude is minimum.
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Gianferrara, Pierre Giovanni, Shawn Betts, and John Robert Anderson. "Cognitive & motor skill transfer across speeds: A video game study." PLOS ONE 16, no. 10 (October 12, 2021): e0258242. http://dx.doi.org/10.1371/journal.pone.0258242.
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We examined the detailed behavioral characteristics of transfer of skill and the ability of the adaptive control of thought rational (ACT-R) architecture to account for this with its new Controller module. We employed a simple action video game called Auto Orbit and investigated the control tuning of timing skills across speed perturbations of the environment. In Auto Orbit, players needed to learn to alternate turn and shot actions to blow and burst balloons under time constraints imposed by balloon resets and deflations. Cognitive and motor skill transfer was assessed both in terms of game performance and in terms of the details of their motor actions. We found that skill transfer across speeds necessitated the recalibration of action timing skills. In addition, we found that acquiring skill in Auto Orbit involved a progressive decrease in variability of behavior. Finally, we found that players with higher skill levels tended to be less variable in terms of action chunking and action timing. These findings further shed light on the complex cognitive and motor mechanisms of skill transfer across speeds in complex task environments.
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Pham Trong, Hoa. "Analysis effects of oil viscosity and temperature on orbit of ring gear in internal gear motor and pump." Transport and Communication Science Journal 70, no. 3 (November 15, 2019): 153–61. http://dx.doi.org/10.25073/tcsj.70.3.1.
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Effect of oil temperature and viscosity on the ring gear orbit in the internal gear motor and pump is analyzed in this study. The mobility method is used to calculate the ring gear orbit. The mathematical model of oil viscosity and temperature is then integrated into the mobility method. The simulation results point out that the oil temperature and viscosity have great effect on the eccentricity, position angle and minimum oil film thickness. The metal - to - metal contact phenomenon occurs if internal gear motor and pump operates under high values of oil temperature or low values of oil viscosity conditions.
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Pham Trong, Hoa. "Analysis effects of oil viscosity and temperature on orbit of ring gear in internal gear motor and pump." Transport and Communications Science Journal 70, no. 3 (November 15, 2019): 153–61. http://dx.doi.org/10.25073/tcsj.70.3.23.
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Effect of oil temperature and viscosity on the ring gear orbit in the internal gear motor and pump is analyzed in this study. The mobility method is used to calculate the ring gear orbit. The mathematical model of oil viscosity and temperature is then integrated into the mobility method. The simulation results point out that the oil temperature and viscosity have great effect on the eccentricity, position angle and minimum oil film thickness. The metal - to - metal contact phenomenon occurs if internal gear motor and pump operates under high values of oil temperature or low values of oil viscosity conditions.
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IONICA, Ioana, Mircea MODREANU, Alexandru-Mihail MOREGA, and Cristian BOBOC. "STUDII DE TRANSFER DE CĂLDURĂ ÎN MAȘINI ELECTRICE UTILIZATE ÎN CONDIȚII DE FUNCȚIONARE SPECIALE." "ACTUALITĂŢI ŞI PERSPECTIVE ÎN DOMENIUL MAŞINILOR ELECTRICE (ELECTRIC MACHINES, MATERIALS AND DRIVES - PRESENT AND TRENDS)" 2020, no. 1 (February 10, 2021): 1–8. http://dx.doi.org/10.36801/apme.2020.1.11.
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"This paper aims to analyze the heat transfer of a DC limited angle torque motor, in special conditions, of space. Three-dimensional models will be used and two current values will be considered. As a working hypothesis, several variants will be numerically analyzed in which the boundary conditions will take into account different values of the emissivity of the motor surfaces varying in the range 0.2 ÷ 1. Inside the motor subassemblies the heat transfer will be done by conduction and between the motor and the environment by radiation. Using thermal modeling, it will be possible to determine the time in which the winding temperature reaches the maximum value allowed for the DC limited angle torque motor, in space conditions. The approached motor presents specific technical aspects (constructive and functional) and novelty in the field of torque motors with limited angle. These types of motors are recommended for applications where both volume and weight are critical requirements. The applications of DC-LATM are diverse: in the fields of aerospace, military technique, medical etc. For special applications (eg aerospace) a redundant motor solution is required [7]. The motor is designed for applications that require rotation over a certain angular range, (the working domain of this motor is 45 ÷ 135°). The space industry is a field of maximum interest from a scientific, economic and strategic point of view. Compared to other fields, its growth in recent years is extraordinary, as evidenced by the availability of telecommunications services. The requirements of the motor given by the application in which it is used including the environmental conditions in which the motor operates will determine the input data of the heat transfer problem. There are two categories of requirements that are equally important: general (mechanical, thermal, electrical) and environmental (stability to vacuum and radiation, resistance to AO - atomic oxygen) etc. Also, several aspects must be considered, such as: environmental effects (LEO - Low Earth Orbit or GEO - Geostationary Orbit), constraints applicable to materials (temperature, vacuum, thermal cycles, chemical - corrosion, galvanic compatibility, atomic oxygen , moisture absorption / desorption, fluid compatibility), if materials will degrade over time, the system in which the product will be integrated, interfaces [8]. The heat transfer analysis addressed in this paper establishes the DC-LATM behavior from a thermal point of view in space conditions."
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Halsey, Jordan N., Ian C. Hoppe, Mark S. Granick, and Edward S. Lee. "A Single-Center Review of Radiologically Diagnosed Maxillofacial Fractures: Etiology and Distribution." Craniomaxillofacial Trauma & Reconstruction 10, no. 1 (February 2017): 44–47. http://dx.doi.org/10.1055/s-0036-1597582.
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The etiology of fractures of the maxillofacial skeleton varies among studies, with motor vehicle accidents and assaults oftentimes the most common. The number of males outnumbers females throughout most studies. Fractures of the zygoma, orbit, and mandible are usually cited as most common fracture types. This study examines a single center's experience with regards to etiology and distribution of fractures. A retrospective review of all radiologically confirmed facial fractures in a level 1 trauma center in an urban environment was performed for the years 2000 to 2012. Patient demographics, etiology of injury, and location of fractures were collected. During this time period, 2,998 patients were identified as having sustained a fracture of the facial skeleton. The average age was 36.9 years, with a strong male predominance (81.5%). The most common etiologies of injury were assault (44.9%) and motor vehicle accidents (14.9%). Throughout the study period, the number of fractures as a result of assault remained relatively constant, whereas the number as a result of motor vehicle accidents decreased slightly. The most common fracture observed was of the orbit, followed by mandible, nasal bones, zygoma, and frontal sinus. Patients sustaining a fracture as a result of assault were more likely to have a mandible fracture. Patients in motor vehicle accidents were more likely to suffer fractures of the maxilla, orbit, and frontal sinus. Mandible fractures are more common in cases of assault. Motor vehicle accidents convey a large force, which, when directed at the craniofacial skeleton, can cause a variety of fracture patterns. The decreasing number of fractures as a result of motor vehicle accidents may represent improved safety devices such as airbags.
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Geiger, Lena. "Validation of a Testbed as a Screening Tool for Telepresence Systems in Terms of Fine-Motor Performance." Presence: Teleoperators and Virtual Environments 20, no. 2 (April 1, 2011): 162–72. http://dx.doi.org/10.1162/pres_a_00041.
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Telepresence systems have the potential to assume an important role in on-orbit servicing scenarios. Compared to manned missions, these systems offer a safer and less expensive way to operate in outer space. One of the main goals of telepresence research is to determine whether immersive telepresence systems are able to achieve a level of efficiency which is equal to that of astronauts in tasks that require fine motor movement and dexterity. In addressing this question, it is of relevance that astronauts' fine-motor skills are restricted by a range of factors including weightlessness and space suits. In order to compare in future studies the efficiency of a telepresence system and suited astronauts in performing fine-motor tasks, a testbed was developed with typical on-orbit servicing tasks which were designed to guarantee maximum external validity. An experimental study showed that the testbed is a valid measure of fine-motor skills. Two follow-up studies examined the potentially debilitating influence of a range of factors on fine-motor performance in extravehicular activities, such as a restricted field of view, a destabilized body posture, restricted mobility, and reduced haptic feedback. The results of these studies offer a basis for comparisons between the performance of common extravehicular activities and telepresence systems on fine-motor tasks.
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Sibony, Patrick A., Azad K. Anand, P. Arjen Keuskamp, and Allen G. Zippen. "Posttraumatic cerebrospinal fluid cyst of the orbit." Journal of Neurosurgery 62, no. 6 (June 1985): 922–24. http://dx.doi.org/10.3171/jns.1985.62.6.0922.
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✓ A 27-year-old man sustained a fracture of the orbital roof and a basofrontal dural tear in a motor-vehicle accident. One week later, he developed an orbitocranial dural fistula manifested by an orbital cyst, pulsatile proptosis, and serous drainage from the eye. Specific diagnosis was established only after computerized tomography metrizamide cisternography demonstrated direct communication of the orbital cyst with the subarachnoid space. The pertinent literature is reviewed.
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Perryman, M. A. C. "The Hipparcos Astrometry Satellite – Two Years After Launch." Highlights of Astronomy 9 (1992): 383–87. http://dx.doi.org/10.1017/s1539299600009230.
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AbstractLaunched in August 1989 into a geostationary transfer orbit, the Hipparcos astrometry satellite failed to reach its intended geostationary orbit through the failure of its apogee boost motor. Present indications are that the possible operational lifetime should nevertheless extend beyond the end of 1992, with extremely high-quality scientific data being returned for some 65 per cent of the time. For an assumed 3-year operational lifetime, the original mission goals (positions, parallaxes, and annual proper motions with an accuracy of about 2 milli-arcsec) should be achievable (the pre-launch expectations of the planned 2.5-year mission would be achievable with a 3.5-year mission in the revised orbit). This paper describes the in-orbit performance of the satellite most relevant to the scientific goals.
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Lee, Geonhui, Woong Choi, Hanjin Jo, Wookhyun Park, and Jaehyo Kim. "Analysis of motor control strategy for frontal and sagittal planes of circular tracking movements using visual feedback noise from velocity change and depth information." PLOS ONE 15, no. 11 (November 11, 2020): e0241138. http://dx.doi.org/10.1371/journal.pone.0241138.
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We aim to investigate a control strategy for the circular tracking movement in a three-dimensional (3D) space based on the accuracy of the visual information. After setting the circular orbits for the frontal and sagittal planes in the 3D virtual space, the subjects track a target moving at a constant velocity. The analysis is applied to two parameters of the polar coordinates, namely, ΔR (the difference in the distance from the center of a circular orbit) and Δω (the difference in the angular velocity). The movement in the sagittal plane provides different depth information depending on the position of the target in orbit, unlike the task of the frontal plane. Therefore, the circular orbit is divided into four quadrants for a statistical analysis of ΔR. In the sagittal plane, the error was two to three times larger in quadrants 1 and 4 than in quadrants 2 and 3 close to the subject. Here, Δω is estimated using a frequency analysis; the lower the accuracy of the visual information, the greater the periodicity. When comparing two different planes, the periodicity in the sagittal plane was approximately 1.7 to 2 times larger than that of the frontal plane. In addition, the average angular velocity of the target and tracer was within 0.6% during a single cycle. We found that if the amount of visual information is reduced, an optimal feedback control strategy can be used to reduce the positional error within a specific area.
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RAJA, M., and O. PRAKASH. "Design of High Pointing Accuracy NPSAT-1 Satellite Attitude Systems of Armature Controlled DC Motor with utilization for PD Controller." INCAS BULLETIN 12, no. 1 (March 1, 2020): 145–56. http://dx.doi.org/10.13111/2066-8201.2020.12.1.14.
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An Attitude control system plays the important role to maintain the satellite to desired attitude orientations. The intended application of NANO satellite in low earth orbits (LEO) helps find transient responses with and without controllers. LEO satellites typically orbit at an altitude ranging between160-2000 km. LEO satellites are widely used for remote sensing, navigation, and military surveillance applications. The Nano NPSAT-1 satellite attitude control systems (ACS) are described in this research work. The high pointing accuracy attitude estimation and feedback control systems are presented. The design specifications have been taken to meet the accuracy requirements (desired value ≤ 0.2 seconds) of Nano satellite attitude control. The feedback signal from on-board sensors compared with reference orbit trajectory and implementation of the Proportional Derivative (PD) controller is constructed. An algorithm of Nano satellite (NPSAT-1) attitude control is implemented using MATLAB Tools. In addition, the closed loop poles help find the gain of the system using Root Locus (RL) methods. The satellite control system is used to improve the transient response like overshoot and settling time of the system. Thus, the design of attitude control to improve the rise time, the settling time, the maximum overshoot, and no steady state error was carried out.
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Inoue, Yoshihiro H., Matthew S. Savoian, Takao Suzuki, Endre Máthé, Masa-Toshi Yamamoto, and David M. Glover. "Mutations in orbit/mast reveal that the central spindle is comprised of two microtubule populations, those that initiate cleavage and those that propagate furrow ingression." Journal of Cell Biology 166, no. 1 (July 5, 2004): 49–60. http://dx.doi.org/10.1083/jcb.200402052.
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We address the relative roles of astral and central spindle microtubules (MTs) in cytokinesis of Drosophila melanogaster primary spermatocytes. Time-lapse imaging studies reveal that the central spindle is comprised of two MT populations, “interior” central spindle MTs found within the spindle envelope and “peripheral” astral MTs that probe the cytoplasm and initiate cleavage furrows where they contact the cortex and form overlapping bundles. The MT-associated protein Orbit/Mast/CLASP concentrates on interior rather than peripheral central spindle MTs. Interior MTs are preferentially affected in hypomorphic orbit mutants, and consequently the interior central spindle fails to form or is unstable. In contrast, peripheral MTs still probe the cortex and form regions of overlap that recruit the Pav-KLP motor and Aurora B kinase. orbit mutants have disorganized or incomplete anillin and actin rings, and although cleavage furrows initiate, they ultimately regress. Our work identifies a new function for Orbit/Mast/CLASP and identifies a novel MT population involved in cleavage furrow initiation.
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Hu, Jianfeng, Tian Shi, Hao duan, and Yong Wang. "Dynamic analysis of the effect of mesh tension on the deployment process of loop antenna." Journal of Physics: Conference Series 2338, no. 1 (September 1, 2022): 012012. http://dx.doi.org/10.1088/1742-6596/2338/1/012012.
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Abstract In orbit deployment and profile maintenance are the most important functional requirements in the development of loop antenna If the antenna cannot be deployed in orbit, it will lose the signal transmission function, and the profile in orbit holding function is related to whether the antenna can stably transmit electromagnetic signals. The mesh tension (main mesh tension, rear mesh tension and tension arrays tension) is the key means to maintain the profile stability in orbit. At the same time, it is also closely related to the rod load and the maximum motor driving force in the process of antenna deployment. Based on the theory of flexible multi-body dynamics, the dynamic modeling of the deployment process of ten meter loop deployable antenna is established in this paper On this basis, the influence of mesh tension on the deployment dynamics of loop antenna is analyzed by using the control variable method, and its related variation law is obtained. This study can provide guidance for the tension adjustment in the profile adjustment stage of the ring antenna, so as to shorten the development cycle, and can also predict the deployment of the antenna in orbit.
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Wang, Pengcheng, Weile Xu, Hao Zhu, Hui Tian, and Guobiao Cai. "An Application of Analytical Target Cascading for a Hierarchical Multidisciplinary System: The Preliminary Design of a Launch Vehicle Powered by Hybrid Rocket Motors." Aerospace 9, no. 12 (December 1, 2022): 778. http://dx.doi.org/10.3390/aerospace9120778.
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Analytical target cascading (ATC) is a method for coordinating hierarchical system design optimization with a decomposition-based framework. Since a launch vehicle (LV) is usually powered by two or more stages of rocket motors, the overall design of the LV clearly has a hierarchical structure, including system level (conducted by the general design department) and subsystem level (conducted by the motor stage design department). In particular, the subsystem level contains stage-divided elements rather than discipline-divided elements. Therefore, ATC is inherently suitable for the overall design of the LV. This paper presents an ATC decomposition framework for LV design according to practical engineering. The feasibility of the multi-island genetic algorithm (MIGA) used in the ATC decomposition is verified by a mathematical programming test, in which non-linear programming with the quadratic Lagrangian (NLPQL) algorithm is set as a comparison. The multi-disciplinary analysis modules of a hybrid rocket motor (HRM) propelled LV, including propulsion, structure, aerodynamics and trajectory, are established. A hierarchical decomposition is proposed for this multi-level design with a multi-disciplinary model. The application and optimization results verify the feasibility of the ATC decomposition framework with MIGA in the preliminary design of the LV and the final orbit accuracy is better than that of the MDF method. In addition, the final design schemes also prove that HRMs can be considered as a feasible choice of propulsion system for a small payload at low earth orbit.
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Zheng, Zhaomingyue, Wei Cheng, Ming Li, Guangyuan Wang, and Limeng Tan. "Analysis and Experimental Study on Dynamic Behavior of Stepper-Actuated Dual-Axis Data Transmission Antenna." International Journal of Aerospace Engineering 2021 (April 15, 2021): 1–18. http://dx.doi.org/10.1155/2021/6624774.
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The satellite-borne data transmission antenna is the main disturbing source of low-frequency microvibration of spacecraft, which immensely affects the image quality of remote sensing satellite. In this paper, the dynamic characteristics of flexible load driven by stepping motor on flexible boundary are studied. The dynamic equation of the stepping motor driven by current subdivision is simplified by linearization method. The dynamic model of flexible load driven by stepping motors on flexible boundary is established by using the Dynamic Substructure Method, and the analytical expression of microvibration of the data transmission antenna is given. The coupling relationship between the stepping motors and the flexible structure is analyzed by modal coordinate transformation. The microvibration model is verified by simulation and experiment, and the main causes and coupling factors of microvibration are explained. The results show that the model can accurately predict the microvibration of the satellite antenna and can be applied to the microvibration prediction in orbit. The reasonable selection of the working velocity of the stepping motors can effectively reduce the microvibration, which provides the basis for the design of the antenna control system.
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Cheng, Wenjie, Zhikai Deng, Ling Xiao, Bin Zhong, and Wenbo Duan. "Rotor dynamic experimental investigation of an ultra-high-speed permanent magnet synchronous motor supported on a three-pad bidirectional gas foil bearing." Advances in Mechanical Engineering 11, no. 9 (September 2019): 168781401987536. http://dx.doi.org/10.1177/1687814019875368.
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With a 10-kW, 120,000-r/min, ultra-high-speed permanent magnet synchronous motor taken as a prototype, experimental research is conducted on the rotor dynamic behaviours of a three-pad bidirectional gas foil bearing high-speed motor rotor system. Load-carrying properties of the three-pad bidirectional gas foil bearing are analysed, and natural frequencies of conical and parallel whirling modes of the elastically supported rotor are calculated based on an appropriate simplification to the stiffness and damping coefficients of the gas foil bearings. The prototype passes through a 90,000-r/min coast-down experiment. Experiments show that there are violent subsynchronous whirling motions that are evoked by the gas foil bearing–rotor system itself. The cause of shaft orbit drift is analysed, and the corresponding solution is put forward. The theoretical analysis and experimental results can offer a useful reference to the bearing–rotor system design of ultra-high-speed permanent magnet motors and its subsequent dynamic analysis.
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Kulber, David A., David Aframian, Martin L. Hopp, and Jonathan R. Hiatt. "Orbital Impalement by a Gearshift Knob: Case Report." Ear, Nose & Throat Journal 71, no. 11 (November 1992): 596–98. http://dx.doi.org/10.1177/014556139207101113.
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Penetrating trauma to the orbit may cause complex injuries involving the bone, globe, and brain. Successful treatment requires a strategic scheme for preoperative assessment and management and a multidisciplinary surgical approach. These principles are demonstrated by report of a motor vehicle accident in which the driver sustained orbital impalement by a gearshift knob.
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Zhu, Hao, Pengcheng Wang, Weile Xu, Yuanjun Zhang, Hui Tian, and Guobiao Cai. "Design Optimization and Parameter Analysis of a Hybrid Rocket Motor-Powered Small LEO Launch Vehicle." International Journal of Aerospace Engineering 2021 (April 29, 2021): 1–20. http://dx.doi.org/10.1155/2021/5574436.
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In this paper, the effects of different grain shapes of a hybrid rocket motor (HRM) and different payload mass/orbit heights on the design of small launch vehicles (SLVs) are systematically discussed. An integrated overall design model for the hybrid rocket motor-powered small launch vehicle (HPSLV) is established, and two groups of three-stage SLVs capable of sending small payloads to the low earth orbit (LEO) are designed and optimized. In the first group, the SLVs with different grain shapes and different numbers of chambers in HRMs at the 1st and the 2nd stages are optimized and analyzed. In the second group, the SLVs capable of sending different payload mass to different orbit heights are optimized and analyzed. Pareto graphs of the design results show that the design of HRM at the 1st stage has the greatest impact on the take-off mass, total velocity increment, and maximum axial overload of the SLV. Self-organizing maps show that the take-off mass, maximum diameter, overall length, and velocity increment of the SLVs have the same variation tendency. For the 1-chamber HRM at the 1st stage, the wheel-shaped grain is better than circle-shaped and star-shaped grains in terms of reducing the total mass and length of the SLV, and the 4-chamber parallel HRM has more advantages over all 1-chamber designs for the same reason. The theoretical velocity increments are calculated by the Tsiolkovsky formula, and the actual velocity increments are obtained based on the trajectory simulation data. The results indicate that the HPSLV has a regular distribution in terms of the ratio of theoretical (actual) velocity increments at three different stages, and the estimated distribution ratio is around 1 : 1.55 : 1.69 (1 : 1.9 : 2.39), which can provide some reference for future development of HPSLV.
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Shengtong, ZHOU, ZHU Jingwei, XIAO Qian, GUO Weinian, and ZHOU Xinjian. "Initial Static Eccentricity and Gravity Load on Rotor Orbit of EMU Traction Motor." Journal of Mechanical Engineering 56, no. 17 (2020): 145. http://dx.doi.org/10.3901/jme.2020.17.145.
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Perryman, M. A. C. "In-Orbit Status of the Hipparcos Astrometry Mission." Symposium - International Astronomical Union 141 (1990): 297–305. http://dx.doi.org/10.1017/s0074180900086976.
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The Hipparcos satellite was successfully launched by Ariane 4 flight 33, from French Guyana, on 8 August 1989. However, the apogee boost motor, designed to place the satellite into its intended geostationary orbit, failed to function, and the satellite was left in a highly elliptical transfer orbit. After a perigee raising manoeuvre, using the hydrazine propulsion system, the orbital parameters are approximately: apogee 35900 km, perigee 526 km, eccentricity 0.72, inclination 6.8°, orbital period 10h 40m.Operational procedures have had to be revised during the first weeks of satellite operations, due to the non-nominal orbit. Commissioning and calibrations have taken longer than foreseen because of the operational difficulties and observational overheads, but routine observations commenced on 27 November. The essential differences between the nominal and the present missions are that observations can only be conducted for about 30-40 per cent of real time in the present mission, and the fact that the actual lifetime of the mission is still rather uncertain, and possibly somewhat shorter than anticipated. This paper gives a summary of the present satellite status, measurement results obtained so far, and in indication of the scientific goals that may be achievable with the present mission.
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Dasgupta, K., A. Mukherjee, and R. Maiti. "Estimation of Critical System Parameters That Affect Orbit Motor Performance—Combining Simulation and Experiments." Journal of Manufacturing Science and Engineering 121, no. 2 (May 1, 1999): 300–306. http://dx.doi.org/10.1115/1.2831220.
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In this paper the authors have presented an integrated study of an orbital rotor Low Speed High Torque (LSHT) hydrostatic unit in a Hydrostatic Transmission (HST) System and an attempt has been made to estimate some critical parameters of such class of geometrically complex machine. Owing to the close tolerance in between the rotor-stator interface of the motor leakage takes place from the high pressure to the low pressure chamber and is difficult to estimate during operation. Based on the simulation and experimental investigations, a semi-empirical approach is proposed here to estimate its interchamber leakage resistance and for that the machine need not be disassembled. Using the actual parametric values, the overall dynamic model of the plant has been validated experimentally.
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Huang, Jianzhe, and Xingzhong Xiong. "Nonlinear behavior for periodically excited brushless motor." COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 38, no. 2 (March 4, 2019): 522–35. http://dx.doi.org/10.1108/compel-07-2018-0295.
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Purpose Due to the coupling between the direct-axis current, quadrature-axis current and rotor speed, the dynamic response could be strongly nonlinear. Besides, if the working condition is severe, the loading is no longer constant and multiple harmonics could be introduced. In this paper, the periodic motions for brushless motor will be solved, and accurate analytic solution will be obtained through the proposed method. The purpose of this study is to provide accurate analytic solution of periodic motions for brushless motor with fluctuated loading, which is a dynamic system with strong nonlinearity. Design/methodology/approach A newly developed semi-analytic algorithm called discrete implicit maps is used to give analytic solutions for both stable and unstable motions for such a motor. Findings The accurate analytic expressions for stable and unstable periodic motions have been obtained. For unstable motion, it can stay on the unstable orbit for many periods without any controller. Through bifurcation analysis, the parameter sensitivity has been obtained which can be a suggestion for design and operation. Originality/value This paper provides all possible analytical solutions for period-1 motion as well as the unstable motions in a range of system parameters. It offers a chance to control the unstable motion for such a motor.
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Iqbal, Syed Shahin, Mohammad Ariful Islam, Md Abu Bakar Siddique, Afroza E. Alam, Md Masud Rana, and Md Hasanuzzaman. "Management of Vascular Malformation of Orbit in a Tertiary Eye Hospital." Central Medical College Journal 5, no. 1 (June 12, 2022): 20–24. http://dx.doi.org/10.3329/cemecj.v5i1.60200.
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Background: Orbit, having a volume of 30cc, contains neurosensory, vascular, motor and secretary structures; is surrounded by facial structures. Visual impairment and restricted ocular motility may be caused by diseases of these structures. Inflammation, neoplasia, structural abnormalities, vascular lesion, and degeneration and deposition can occur within or around the orbit.
Objective: To evaluate the outcome of the management of vascular lesions of orbit and ocular adnexa attending at a tertiary eye hospital.
Method: A prospective interventional study was conducted in a tertiary eye hospital, during the period of July, 2008 to June, 2010. A total of 60 patients with proptosis/lid growth irrespective of age and sex were selected for this study according to selection criteria. Method of medical and surgical treatment were recorded and postoperative details examination including visual acuity, amount of proptosis, cosmetic outcome had been done. Patients were followed after first day, first week, six weeks and six months of postoperative period.
Result: In vascular lesion of the orbit, 53.33 % patients were cavernous haemangioma, 26.67 % patients were capillary haemangioma, 8.33%patients were orbital varices, 6.67 % patients were lymphangioma and 5 % were haemangiopericytoma. Only 10 (16.67%) cases managed by medical treatment and bulk of the patients about 50 (83.33%) patients surgically managed. 10 (62.5%) patients of capillary haemangioma were managed by medically. Among the surgical complications stitch granuloma was higher (10) followed by recurrence (6). There were no complications occurred in 30 (50%) cases.
Conclusion: Cavernous haemangioma was higher among vascular lesions of orbit and adnexa treated surgically.
Central Medical College Journal Vol 5 No 1 Jan 2021 PP 20-24
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Jay, M. F., and D. L. Sparks. "Sensorimotor integration in the primate superior colliculus. II. Coordinates of auditory signals." Journal of Neurophysiology 57, no. 1 (January 1, 1987): 35–55. http://dx.doi.org/10.1152/jn.1987.57.1.35.
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Based on the findings of the preceding paper, it is known that auditory and visual signals have been translated into common coordinates at the level of the superior colliculus (SC) and share a motor circuit involved in the generation of saccadic eye movements. It is not known, however, whether the translation of sensory signals into motor coordinates occurs prior to or within the SC. Nor is it known in what coordinates auditory signals observed in the SC are encoded. The present experiment tested two alternative hypotheses concerning the frame of reference of auditory signals found in the deeper layers of the SC. The hypothesis that auditory signals are encoded in head coordinates predicts that, with the head stationary, the response of auditory neurons will not be affected by variations in eye position but will be determined by the location of the sound source. The hypothesis that auditory responses encode the trajectory of the eye movement required to look to the target (motor error) predicts that the response of auditory cells will depend on both the position of the sound source and the position of the eyes in the orbit. Extracellular single-unit recordings were obtained from neurons in the SC while monkeys made delayed saccades to auditory or visual targets in a darkened room. The coordinates of auditory signals were studied by plotting auditory receptive fields while the animal fixated one of three targets placed 24 degrees apart along the horizontal plane. For 99 of 121 SC cells, the spatial location of the auditory receptive field was significantly altered by the position of the eyes in the orbit. In contrast, the responses of five sound-sensitive cells isolated in the inferior colliculus were not affected by variations in eye position. The possibility that systematic variations in the position of the pinnae associated with different fixation positions could account for these findings was controlled for by plotting auditory receptive fields while the pinnae were mechanically restrained. Under these conditions, the position of the eyes in the orbit still had a significant effect on the responsiveness of collicular neurons to auditory stimuli. The average magnitude of the shift of the auditory receptive field with changes in eye position (12.9 degrees) did not correspond to the magnitude of the shift in eye position (24 degrees). Alternative explanations for this finding were considered. One possibility is that, within the SC, there is a gradual transition from auditory signals in head coordinates to signals in motor error coordinates.(ABSTRACT TRUNCATED AT 400 WORDS)
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Chavarette, Fábio Roverto. "On an Optimal Linear Control of a Chaotic Non-Ideal Duffing System." Applied Mechanics and Materials 138-139 (November 2011): 50–55. http://dx.doi.org/10.4028/www.scientific.net/amm.138-139.50.
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In this work, we use a nonlinear control based on Optimal Linear Control. We used as mathematical model a Duffing equation to model a supporting structure for an unbalanced rotating machine with limited power (non-ideal motor). Numerical simulations are performed for a set control parameter (depending on the voltage of the motor, that is, in the static and dynamic characteristic of the motor) The interaction of the non-ideal excitation with the structure may lead to the occurrence of interesting phenomena during the forward passage through the several resonance states of the system. Chaotic behavior is obtained for values of the parameters. Then, the proposed control strategy is applied in order to regulate the chaotic behavior, in order to obtain a periodic orbit and to decrease its amplitude. Both methodologies were used in complete agreement between them. The purpose of the paper is to give suggestions and recommendations to designers and engineers on how to drive this kind of system through resonance.
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Turliuc, Dana Mihaela, A. I. Cucu, Gabriela Florenta Dumitrescu, Anca Sava, and Claudia Florida Costea. "Orbitocranial penetrating injury by a metallic foreign body. Case report and anatomical considerations." Romanian Neurosurgery 31, no. 4 (December 20, 2017): 437–43. http://dx.doi.org/10.1515/romneu-2017-0070.
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Abstract Orbitocranial penetrating injuries (OPI) represent a rare type of head injuries encountered in clinical practice. These appear after falls or motor vehicle accidents and are more frequent among children. We present the case of a male patient with OPI, associated with large frontal hemorrhagic contusion, with minimal periorbital trauma findings related to brain injury. Knowing and understanding the clinical anatomy of the orbit and the patterns of injuries in OPI are mandatory, since failure in detecting intracranial complications may lead to the increase of the neurological morbidity, visual loss and death.
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Patel, Radhika, and Sangeetha Madhavan. "Comparison of Transcranial Direct Current Stimulation Electrode Montages for the Lower Limb Motor Cortex." Brain Sciences 9, no. 8 (August 6, 2019): 189. http://dx.doi.org/10.3390/brainsci9080189.
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Transcranial direct current stimulation (tDCS) has been widely explored as a neuromodulatory adjunct to modulate corticomotor excitability and improve motor behavior. However, issues with the effectiveness of tDCS have led to the exploration of empirical and experimental alternate electrode placements to enhance neuromodulatory effects. Here, we conducted a preliminary study to compare a novel electrode montage (which involved placing 13 cm2 electrodes anterior and posterior to the target location) to the traditionally used electrode montage (13 cm2 stimulating electrode over the target area and the 35 cm2 reference electrode over the contralateral orbit). We examined the effects of tDCS of the lower limb motor area (M1) by measuring the corticomotor excitability (CME) of the tibialis anterior muscle using transcranial magnetic stimulation in twenty healthy participants. We examined behavioral effects using a skilled motor control task performed with the ankle. We did not find one electrode montage to be superior to the other for changes in the CME or motor control. When the group was dichotomized into responders and non-responders (based on upregulation in CME), we found that the responders showed significant upregulation from baseline after tDCS for both montages. However, only the responders in the traditional montage group showed significant changes in motor control after tDCS. These results do not support the superiority of the new anterior–posterior montage over the traditional montage. Further work with a larger cohort and multiple cumulative sessions may be necessary to confirm our results.
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O'Keefe, L. P., and M. A. Berkley. "Binocular immobilization induced by paralysis of the extraocular muscles of one eye: evidence for an interocular proprioceptive mechanism." Journal of Neurophysiology 66, no. 6 (December 1, 1991): 2022–33. http://dx.doi.org/10.1152/jn.1991.66.6.2022.
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1. Spontaneous changes in the positions of both eyes were measured in anesthetized cats before and after infusion of paralytic or anesthetic agents directly into the extraocular muscle capsule behind one eye. 2. Before retrobulbar injection, large changes in eye position were observed in both eyes. The position changes of each eye were independent of each other and often in opposite directions. 3. Application of a paralytic agent into the orbit of one eye reduced the spontaneous position changes in that eye to a very low level. Unexpectedly, the changes in the position of the other, untreated eye were also greatly reduced. 4. Control experiments demonstrated that the binocular immobilization observed after monocular paralysis was not due to 1) leakage of the paralytic agent from the orbit of the treated eye to the orbit of the untreated eye or 2) systemic vascular transport of the paralytic agent. 5. Passive movement of the paralyzed eye did not induce movement of the untreated eye. 6. Application of a local anesthetic agent rather than a paralytic agent to one eye resulted in reversible reduction of movement only in the treated eye, but not in the untreated eye. 7. The results suggest that the reduction of movement in one eye produced by application of a paralytic agent to the other eye is mediated by an afferent neural signal derived from extraocular muscle proprioceptors possibly gated by a central motor control signal.
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Roy, Debanshu, Rathindranath Maiti, and Prasanta Kumar Das. "Mechanics and FEM estimation of gaps generated in star-ring active contacts of ORBIT motor during operation." International Journal of Mechanics and Materials in Design 16, no. 1 (April 8, 2019): 69–89. http://dx.doi.org/10.1007/s10999-019-09455-z.
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Apaydin, Nihal, Simel Kendir, and Suleyman Tuna Karahan. "The Anatomical Relationships of the Ocular Motor Nerves with an Emphasis on Surgical Anatomy of the Orbit." Anatomical Record 302, no. 4 (April 27, 2018): 568–74. http://dx.doi.org/10.1002/ar.23820.
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Elzinga, Jason L., and Herman Bami. "Emergency lateral canthotomy and cantholysis to relieve intraocular pressure following severe motor vehicle collision." University of Western Ontario Medical Journal 86, no. 1 (August 29, 2017): 49–51. http://dx.doi.org/10.5206/uwomj.v86i1.2180.
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A young woman displayed a dilated and fixed pupil following a motor vehicle collision with blunt force trauma to face. This was associated with drastically elevated intraocular pressure and proptosis. It was believed that a retrobulbar bleed was causing ocular compartment syndrome, an ischemic condition whereby elevated pressure within the orbit occludes blood flow to the retina and ocular nerves. This is a rare ocular emergency, and must be promptly treated to prevent permanent damage. Ophthalmology was consulted by telephone to confirm the diagnosis and direct treatment. A lateral canthotomy and cantholysis was performed under guidance from Ophthalmology and free open access medical education resources. The trauma team managed to save the eye, with visual acuity remaining near normal. In this report, the mechanism of orbital compartment syndrome is explained, and the lateral canthotomy and cantholysis procedure is outlined. This case highlights the importance of telephone consultation and easily accessible medical education resources in the acute care of rare conditions that may arise following trauma.
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Dommanget, J., and P. Lampens. "How Double Star Astronomy May Develop After HIPPARCOS." International Astronomical Union Colloquium 135 (1992): 435–38. http://dx.doi.org/10.1017/s0252921100006928.
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AbstractNow that the HIPPARCOS satellite safely revolves on its “degraded” orbit — after the exploit of the ESA technicians to rescue it from the faulty ignition of its apogeum boost motor — and regularly provides the information expected for reaching the initial aim of the project, one may turn to examine the possible exploitation of the final HIPPARCOS Catalogue.In the present paper, we describe how double and multiple stars have been introduced in the Input Catalogue and what may be expected from their observation. We also try to evaluate how much the final HIPPARCOS data may influence future researches on these celestial bodies and what kind of ground–based observation programmes should be conducted in order to support the space results.
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Anshakov, G. P., A. V. Krestina, and I. S. Tkachenko. "Analysis of the effectiveness of the de-orbiting devices for small satellite." Spacecrafts & Technologies 4, no. 2 (2020): 72–84. http://dx.doi.org/10.26732/j.st.2020.2.02.
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At present, the use of various methods is proposed for the de-orbit of small satellite, and the most feasible and promising of them are analyzed. The task of evaluating the effectiveness of the de-orbiting system for small satellite is set, in the framework of which a criterion and basic performance indicators are formed taking into account design features. As a methodological basis for evaluating the effectiveness, the method of relative integral assessment was used. Using the developed algorithm for calculating the coefficients of the integral relative assessment for each de-orbiting method, the most effective option for constructing the system isdetermined for given priority coefficients and taking into account the imposed design restrictions. For the analysis of efficiency, fuel-free de-orbiting devices and three types of propulsion systems were chosen – electric propulsion engine, solid rocket motor and liquid engine. Efficiency analysis was carried out for devices with various mass and target characteristics, the result is the choice of the type of de-orbiting system and the calculation of its parameters. The dependence of the de-orbiting device on the purpose of the spacecraft, the altitude and inclination of the orbit of its functioning, as well as on the requirements for mass, cost and other design parameters is shown.
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McCluskey, Meaghan K., and Kathleen E. Cullen. "Eye, Head, and Body Coordination During Large Gaze Shifts in Rhesus Monkeys: Movement Kinematics and the Influence of Posture." Journal of Neurophysiology 97, no. 4 (April 2007): 2976–91. http://dx.doi.org/10.1152/jn.00822.2006.
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Coordinated movements of the eye, head, and body are used to redirect the axis of gaze between objects of interest. However, previous studies of eye-head gaze shifts in head-unrestrained primates generally assumed the contribution of body movement to be negligible. Here we characterized eye-head-body coordination during horizontal gaze shifts made by trained rhesus monkeys to visual targets while they sat upright in a standard primate chair and assumed a more natural sitting posture in a custom-designed chair. In both postures, gaze shifts were characterized by the sequential onset of eye, head, and body movements, which could be described by predictable relationships. Body motion made a small but significant contribution to gaze shifts that were ≥40° in amplitude. Furthermore, as gaze shift amplitude increased (40–120°), body contribution and velocity increased systematically. In contrast, peak eye and head velocities plateaued at velocities of ∼250–300°/s, and the rotation of the eye-in-orbit and head-on-body remained well within the physical limits of ocular and neck motility during large gaze shifts, saturating at ∼35 and 60°, respectively. Gaze shifts initiated with the eye more contralateral in the orbit were accompanied by smaller body as well as head movement amplitudes and velocities were greater when monkeys were seated in the more natural body posture. Taken together, our findings show that body movement makes a predictable contribution to gaze shifts that is systematically influenced by factors such as orbital position and posture. We conclude that body movements are part of a coordinated series of motor events that are used to voluntarily reorient gaze and that these movements can be significant even in a typical laboratory setting. Our results emphasize the need for caution in the interpretation of data from neurophysiological studies of the control of saccadic eye movements and/or eye-head gaze shifts because single neurons can code motor commands to move the body as well as the head and eyes.
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Ngoune, Chantal. "Cavernous sinus thrombophlebitis caused by a dental infection: A case report." International Journal of Clinical Case Reports and Reviews 7, no. 04 (July 17, 2021): 01–04. http://dx.doi.org/10.31579/2690-4861/126.
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Septic cavernous sinus thrombosis (CST) is a rare, life-threatening complication of infections of any of the tissues drained by the cavernous sinus such as the mid-face, orbit and sinuses. With the introduction of antibiotics, the mortality and morbidity rates have significantly reduced although they remain high. The necessity of an early diagnosis and appropriate treatment is therefore of great importance. Clinical presentation includes proptosis, chemosis, ocular motor nerve palsy, and sensitive disorders. Imaging investigations, such as contrast enhanced computed tomography (CT) and magnetic resonance imaging (MRI) have had a significant impact on the diagnosis. This condition is rare and after literature review, we found very few case series and some cases reports. We herein share a case of cavernous sinus thrombophlebitis caused by a dental infection.
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Chang, Xia, Li Song, Chun Wang, and Ai Zhang. "A Control and Simulation Method for Space-based Opto-mechanical Structures Using Uniform Scanning." Journal of Physics: Conference Series 2395, no. 1 (December 1, 2022): 012046. http://dx.doi.org/10.1088/1742-6596/2395/1/012046.
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Abstract To achieve high-precision imaging in the calibration area of a sub-satellite point, this paper proposes a method for assessing the scanning accuracy and how it affects the agility of the maneuvering process. In addition, simulations and experimental validation are also conducted using a position-velocity dual-loop control algorithm. The design is based on the control theory and the operating characteristics of the actual flexible scanning mechanism, the control law is designed using the control method based on the permanent magnet synchronous motor model, and the interference is simulated and analyzed. The results show that the design can combine the control performance indexes of practical applications and meet the requirements of in-orbit high-precision scanning, which can provide a reference for the subsequent development of space high-precision scanning control.
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Harding, Shannon M., Neeraj J. Singh, and Kerry D. Walton. "A Sensitive Period for the Development of Motor Function in Rats: A Microgravity Study." Gravitational and Space Research 5, no. 2 (July 21, 2020): 57–79. http://dx.doi.org/10.2478/gsr-2017-0011.
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AbstractSpaceflight studies offer a unique opportunity to examine the impact of gravity on developing motor skills. Previously, we reported that young rats experiencing microgravity in low Earth orbit (LEO) beginning on postnatal day (P)14 showed impaired swimming, walking, and surface righting after returning to 1 g, with immature motor skills persisting until adulthood. Here, we report on post-flight surface righting and swimming of rats experiencing spaceflight from P7 or P8. Litters with dams were flown aboard a space shuttle Space Transportation System (STS) 9-day (NIH-R3, STS-72) or 16-day mission (Neurolab, STS-90). Flight rats from both missions showed significantly fewer mature, age-appropriate righting tactics after landing compared to ground controls. Flight rats also had a steeper body angle while floating in the water before swimming, started swimming sooner, and swam faster. The effects on surface righting persisted for the duration of behavior tests (6 days [9-day mission] or 23 days [16-day mission]), after landing. Differences in pre-swimming behavior resolved by return day (R)2, and differences in swimming speed and posture resolved by R10. These data suggest that exposure to microgravity at a young age prevents the normal development of surface righting and that the normal development of swimming can recover if animals return from LEO by P16 or P24. These findings lend additional support to the existence of a critical period of development for motor function. However, studies are needed with improved housing during spaceflight to ensure that maternal offspring behavior is not disrupted, as was observed during the Neurolab mission.
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Ewert, Pawel, Czeslaw T. Kowalski, and Michal Jaworski. "Comparison of the Effectiveness of Selected Vibration Signal Analysis Methods in the Rotor Unbalance Detection of PMSM Drive System." Electronics 11, no. 11 (May 31, 2022): 1748. http://dx.doi.org/10.3390/electronics11111748.
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Mechanical unbalance is a phenomenon that concerns rotating elements, including rotors in electrical machines. An unbalanced rotor generates vibration, which is transferred to the machine body. The vibration contributes to reducing drive system reliability and, as a consequence, leads to frequent downtime. Therefore, from an economic point of view, monitoring the unbalance of rotating elements is justified. In this paper, the rotor unbalance of a drive system with a permanent magnet synchronous motor (PMSM) was physically modelled using a specially developed shield, with five test masses fixed at the motor shaft. The analysed diagnostic signal was mechanical vibration. Unbalance was detected using selected signal analysis methods, such as frequency-domain methods (classical spectrum analysis FFT and a higher-order bispectrum method) and two methods applied in technical diagnostics (order analysis and orbit method). The efficiency of unbalance symptom detection using these four methods was compared for the frequency controlled PMSM. The properties of the analysed diagnostic methods were assessed and compared in terms of their usefulness in rotor unbalance diagnosis, and the basic features characterizing the usefulness of these methods were determined depending on the operating conditions of the drive. This work could have a significant impact on the process of designing diagnostic systems for PMSM drives.
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Casalino, Lorenzo, Filippo Masseni, and Dario Pastrone. "Optimal Design of Electrically Fed Hybrid Mars Ascent Vehicle." Aerospace 8, no. 7 (July 6, 2021): 181. http://dx.doi.org/10.3390/aerospace8070181.
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The optimal design of the propulsion system for a potential Mars Ascent Vehicle is analyzed, in the context of the Mars Sample Return Mission. The Mars Ascent Vehicle has to perform an initial ascent phase from the surface and then circularize into a 170 km orbit. A two-stage launcher is taken into account: the same hybrid rocket engine is considered for both stages in order to limit the development costs. A cluster of two, three or four engines is employed in the first stage, whereas a single engine is always used in the second stage. Concerning the feeding system, three alternatives are taken into consideration, namely a blow down, a regulated and an electric turbo-pump feed system. The latter employs an electric motor to drive the oxidizer turbopump, whereas the power is supplied to the motor by lithium batteries. All the design options resulted in viable Mars Ascent Vehicle configurations (payloads are in the range of 70–100 kg), making the hybrid alternative worth considering for the sample return mission. The use of an electric turbo-pump feed system determines the highest vehicle performance with an estimated 10–25% payload gain with respect to gas-pressure feed systems.
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Le, Luc Tien. "PASSIVITY BASED ON ENERGY TANK FOR CARTESIAN IMPEDANCE CONTROL OF DLR SPACE ROBOTS WITH FLOATING BASE AND ELASTIC JOINTS." Journal of Computer Science and Cybernetics 34, no. 1 (August 8, 2018): 49–62. http://dx.doi.org/10.15625/1813-9663/34/1/11027.
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This paper presents a control structure for orbital servicing mission of CEASAR robotic arm developed by German Aerospace Center (DLR). In order to reduce mass the CEASAR arm is equipped with Harmonic-Drives with high ratio which unfortunately lead to high joint elasticity and high motor friction and have to be considered in controller design for successful manipulator in-orbit operations. Therefore, in this control structure, for high tracking control a cascaded position controller based on state feedback control structure with observer-based friction compensation and for safe interaction control with the environment a Cartesian impedance controller is used. The proposed control methods are very efficient and practicable. Furthermore, they are very robust with dynamic parameter uncertainties, coupling dynamics, and can simultaneously provide good results in term of the position accuracy and dynamic behavior. Simulation results validate practical efficiency of the controllers.
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Yu, Jisong, Yongliang Guan, Daowei Zhang, Shanbo Chen, Chunjuan Zhao, and Lei Zhang. "Simulation and Experimental Research on the Disturbance Behavior of a Sun-Tracking Solar Array Driven by a Stepping Motor." Applied Sciences 11, no. 19 (September 29, 2021): 9076. http://dx.doi.org/10.3390/app11199076.
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A sun-tracking solar array is an effective solution to the increasing energy demand of spacecrafts. However, the driving torque fluctuation of the solar array driving assembly (SADA) and its oscillatory motion lead to the micro-vibration problem of the spacecraft. In this article, a disturbance torque model of the sun-tracking solar array, which takes its friction and flexibility into consideration, is established. Furthermore, a test platform was built to measure the disturbance force/torque, and a solar array simulator (SAS) was designed to replace the solar array in the ground experiments. Finally, the disturbance torque of the SADA-driven SAS is simulated, and the model is validated by comparing the simulation results with the experimental results. These results show that the frequency error of the model is less than 0.648%, and the amplitude error of the corresponding frequency is less than 22.33%, which indicates that the proposed model can effectively predict the disturbance torque generated by the sun-tracking solar array in orbit. The research provides theoretical guidance for the system optimization design and micro-vibration suppression of spacecrafts.
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Sarego, Giulia, Lorenzo Olivieri, Andrea Valmorbida, Alice Brunello, Enrico C. Lorenzini, Lorenzo Tarabini Castellani, Eduardo Urgoiti, Asier Ortega, Gabriel Borderes-Motta, and Gonzalo Sánchez-Arriaga. "Deployment requirements for deorbiting electrodynamic tether technology." CEAS Space Journal 13, no. 4 (February 15, 2021): 567–81. http://dx.doi.org/10.1007/s12567-021-00349-5.
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AbstractIn the last decades, green deorbiting technologies have begun to be investigated and have raised a great interest in the space community. Among the others, electrodynamic tethers appear to be a promising option. By interacting with the surrounding ionosphere, electrodynamic tethers generate a drag Lorentz force to decrease the orbit altitude of the satellite, causing its re-entry in the atmosphere without using propellant. In this work, the requirements that drive the design of the deployment mechanism proposed for the H2020 Project E.T.PACK—Electrodynamic Tether Technology for Passive Consumable-less Deorbit Kit—are presented and discussed. Additionally, this work presents the synthesis of the reference profiles used by the motor of the deployer to make the tethered system reach the desired final conditions. The result is a strategy for deploying electrodynamic tape-shaped tethers used for deorbiting satellites at the end of their operational life.
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Shim, Yoonsik, and Phil Husbands. "Chaotic Exploration and Learning of Locomotion Behaviors." Neural Computation 24, no. 8 (August 2012): 2185–222. http://dx.doi.org/10.1162/neco_a_00313.
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We present a general and fully dynamic neural system, which exploits intrinsic chaotic dynamics, for the real-time goal-directed exploration and learning of the possible locomotion patterns of an articulated robot of an arbitrary morphology in an unknown environment. The controller is modeled as a network of neural oscillators that are initially coupled only through physical embodiment, and goal-directed exploration of coordinated motor patterns is achieved by chaotic search using adaptive bifurcation. The phase space of the indirectly coupled neural-body-environment system contains multiple transient or permanent self-organized dynamics, each of which is a candidate for a locomotion behavior. The adaptive bifurcation enables the system orbit to wander through various phase-coordinated states, using its intrinsic chaotic dynamics as a driving force, and stabilizes on to one of the states matching the given goal criteria. In order to improve the sustainability of useful transient patterns, sensory homeostasis has been introduced, which results in an increased diversity of motor outputs, thus achieving multiscale exploration. A rhythmic pattern discovered by this process is memorized and sustained by changing the wiring between initially disconnected oscillators using an adaptive synchronization method. Our results show that the novel neurorobotic system is able to create and learn multiple locomotion behaviors for a wide range of body configurations and physical environments and can readapt in realtime after sustaining damage.
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Islam, Md Rafiqul, Hasan Zahidur Rahman, Akm Anwar Ullah, Md Amir Hossain, and Md Ziauddin. "Tolosa-Hunt Syndrome: A Case Report and Review of the Literature." Bangladesh Journal of Neuroscience 29, no. 2 (July 31, 2013): 130–33. http://dx.doi.org/10.3329/bjn.v29i2.56182.
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Tolosa-Hunt Syndrome is a painful ophthalmoplegia which is characterized by periorbital or hemicranial pain, with ipsilateral ocular motor nerve palsies, oculosympathetic paralysis, sensory loss in the distribution of the ophthalmic and occasionally the maxillary division of the trigeminal nerve. Various combinations of these cranial nerve palsies may occur, localising the pathological process to the region of the cavernous sinus/superior orbital fissure. We report the case of a patient presented with severe pain in the right side of face which was periorbital with ipsilateral 3rd,4th, 6th cranial nerve palsies along with ophthalmic and maxillary division of trigeminal nerve involvement. MRI of orbit showed hypo-intense lesion in right cavernous sinus extending to right superior orbital fissure (suggestive of granulomatous infiltration). After taking oral steroid her pain was relieved quickly and cranial nerve palsies reversed within one week. Azathioprin was added and she was completely cured of within next three months.
Bangladesh Journal of Neuroscience 2013; Vol. 29 (2) : 130-133
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Lachanas, V. A., G. T. Karatzias, I. Tsitiridis, I. Panaras, and V. G. Sandris. "Tolosa–Hunt syndrome misdiagnosed as sinusitis complication." Journal of Laryngology & Otology 122, no. 1 (January 2008): 97–99. http://dx.doi.org/10.1017/s0022215106005317.
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AbstractObjective:Tolosa–Hunt syndrome is a rare condition of painful ophthalmoplegia combined with ipsilateral ocular motor nerve palsies, caused by non-specific granulomatous inflammation in the cavernous sinus, superior orbital fissure or orbit. A case of Tolosa–Hunt syndrome misdiagnosed as sinusitis orbital complication is reported.Case report:A patient suffering from left periorbital pain, upper eyelid oedema and ptosis, and horizontal diplopia, diagnosed as sinusitis orbital complication, was referred to our department. Clinical evaluation revealed only a left VIth nerve paresis. Haematological studies, cerebrospinal fluid tests and computed tomography scanning were negative. A magnetic resonance imaging (MRI) scan showed enhancement of the left cavernous sinus. Corticosteroid therapy was commenced, and within three days all symptoms disappeared. A diagnosis of Tolosa–Hunt syndrome was made. Follow-up MRI studies were normal.Conclusion:Tolosa–Hunt syndrome, although rare, is a nosological entity that otolaryngologists must bear in mind. Magnetic resonance imaging studies are essential in the diagnosis and follow up of these patients, in order to avoid a mistaken Tolosa–Hunt syndrome diagnosis.
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Abdulrazeq, Hael, Konrad Walek, Shailen Sampath, Elias Shaaya, Dardan Beqiri, Albert Woo, and Prakash Sampath. "Development of posttraumatic frontal brain abscess in association with an orbital roof fracture and odontogenic abscess: A case report." Surgical Neurology International 13 (November 18, 2022): 539. http://dx.doi.org/10.25259/sni_813_2022.
Full textAbstract:
Background: Brain abscess is a potentially fatal condition. Orbital fractures caused by penetrating injury may be associated with intracranial infection. Such complication associated with blunt trauma, orbital roof fractures, and odontogenic abscesses is exceedingly rare. Case Description: We report the case of a 40-year-old transgender female with a frontal abscess presenting several weeks following a motor vehicle crash from which she suffered multiple facial fractures and an odontogenic abscess. On computed tomography scan, the patient had multiple right-sided facial fractures, including a medial orbital wall fracture and a right sphenoid fracture extending into the superior orbital roof. There was hemorrhage notable in the right frontal lobe. Communication with the ethmoid sinuses likely provided a conduit for bacterial spread through the orbit and into the intracranial and subdural spaces. Conclusion: Skull base fractures that communicate with a sinus, whether it be frontal, ethmoid, or sphenoid may increase the risk of brain abscess, especially in patients who develop an odontogenic abscess. Surgical repair of the defect is essential, and treating patients prophylactically with antibiotics may be beneficial.