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Artykuły w czasopismach na temat "One stage rotation"
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Alkadhimi, Aslam. "A novel and simple technique for correcting localised rotations in the early alignment stage". Journal of Orthodontics 47, nr 4 (27.08.2020): 338–44. http://dx.doi.org/10.1177/1465312520949553.
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Correcting severe tooth rotations can be challenging. There are many ways to de-rotate teeth with fixed or removable appliances. Mechanically, the best and most effective way is one that produces a two-force couple system to rotate a tooth around its centre of rotation (longitudinal axis). The aim of this article was to introduce a simple and efficient technique using a closed coil to correct localised tooth rotations in the early alignment stage, utilising a simple two-force couple system. Furthermore, some of the biomechanical principles concerning de-rotation will be revisited.
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Ye, Tingting, i Yangmin Li. "Synthesis of 2-DOF Decoupled Rotation Stage with FEA-Based Neural Network". Processes 11, nr 1 (6.01.2023): 192. http://dx.doi.org/10.3390/pr11010192.
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Transfer printing technology has developed rapidly in the last decades, offering a potential demand for 2-DOF rotation stages. In order to remove decoupling modeling, improve motion accuracy, and simplify the control method, the 2-DOF decoupled rotation stages based on compliant mechanisms present notable merits. Therefore, a novel 2-DOF decoupled rotation stage is synthesized of which the critical components of decoupling are the topological arrangement and a novel decoupled compound joint. To fully consider the undesired deformation of rigid segments, an FEA-based neural network model is utilized to predict the rotation strokes and corresponding coupling ratios, and optimize the structural parameters. Then, FEA simulations are conducted to investigate the static and dynamic performances of the proposed 2-DOF decoupled rotation stage. The results show larger rotation strokes of 4.302 mrad in one-axis actuation with a 1.697% coupling ratio, and 4.184 and 4.151 mrad in two-axis actuation with undesired Rz rotation of 0.014 mrad with fewer actuators than other works. In addition, the first natural frequency of 2151 Hz is also higher, enabling a wider working frequency range.
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Kurokawa, Hiroaki, Shinichi Kosugi, Takuya Fujinuma, Yuya Oishi, Takuma Miyamoto, Akira Taniguchi, Hiroshi Takemura i Yasuhito Tanaka. "Evaluation of Subtalar Joint’s Compensatory Function in Varus Ankle Osteoarthritis Using Globally Optimal Iterative Closest Points (Go-ICP)". Foot & Ankle Orthopaedics 7, nr 2 (kwiecień 2022): 247301142211035. http://dx.doi.org/10.1177/24730114221103584.
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Background: A previous study on 2-dimensional evaluation of the subtalar joint functioning in varus ankle osteoarthritis concluded that varus deformity was compensated for by the subtalar joint during early stages but not in the advanced stages. Although compensatory function is expected both along the axial and coronal planes, compensatory function in all 3 dimensions (3D) remains unevaluated. This study evaluated the 3D-compensatory function of a varus subtalar joint using Globally Optimal Iterative Closest Points (Go-ICP), a 3D-shape registration algorithm, after 3D-bone shape reconstruction using computed tomography. Methods: This study included 22 ankles: 4 stage 2 ankles, 5 stage 3a ankles, 6 stage 3b ankles, and 4 stage 4 ankles, categorized according to the Takakura-Tanaka classification. As the control group, 3 ankles without prior ankle injuries and disorders and 4 stage 2 ankles were included. One control ankle was used as a reference. Relative values compared with the reference ankle were evaluated in each group using Go-ICP. Each axis was set so that dorsiflexion, valgus, and abduction were positive on the X axis, Y axis, and Z axis, respectively. Results: Rotation angles of the talus (Rotation T) and calcaneus (Rotation C) on the Y axis in the control and stage 3b were −7.6, −28, −2.1, and −13 degrees, respectively, indicating significant differences. Value of Rotation T-Rotation C (Rotation T-C) represents compensatory function of the subtalar joint. In all ankles, there was a correlation between Rotation T and Rotation T-C on the Y axis and Z axis ( P < .01, r = 0.84; P < .01, r = −0.84, respectively). There was a correlation between Rotation T values on the on Y and Z axes ( P = .01, r = 0.53). Conclusion: In varus ankle osteoarthritis, the talus had varus deformity with adduction. Compensatory function in the coronal plane persisted, even in the advanced stages; however, it was not sufficiently maintained in stage 3b. Furthermore, compensatory function in the axial plane was relatively sustained. Level of Evidence: Level III, retrospective comparative study.
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Yang, Xue, Junchi Yan, Ziming Feng i Tao He. "R3Det: Refined Single-Stage Detector with Feature Refinement for Rotating Object". Proceedings of the AAAI Conference on Artificial Intelligence 35, nr 4 (18.05.2021): 3163–71. http://dx.doi.org/10.1609/aaai.v35i4.16426.
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Rotation detection is a challenging task due to the difficulties of locating the multi-angle objects and separating them effectively from the background. Though considerable progress has been made, for practical settings, there still exist challenges for rotating objects with large aspect ratio, dense distribution and category extremely imbalance. In this paper, we propose an end-to-end refined single-stage rotation detector for fast and accurate object detection by using a progressive regression approach from coarse to fine granularity. Considering the shortcoming of feature misalignment in existing refined single-stage detector, we design a feature refinement module to improve detection performance by getting more accurate features. The key idea of feature refinement module is to re-encode the position information of the current refined bounding box to the corresponding feature points through pixel-wise feature interpolation to realize feature reconstruction and alignment. For more accurate rotation estimation, an approximate SkewIoU loss is proposed to solve the problem that the calculation of SkewIoU is not derivable. Experiments on three popular remote sensing public datasets DOTA, HRSC2016, UCAS-AOD as well as one scene text dataset ICDAR2015 show the effectiveness of our approach. The source code is available at https://github.com/Thinklab-SJTU/R3Det_Tensorflow and is also integrated in our open source rotation detection benchmark: https://github.com/yangxue0827/RotationDetection.
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D'Alessandro, G., L. Mele, F. Columbro, G. Amico, E. S. Battistelli, P. de Bernardis, A. Coppolecchia i in. "QUBIC VI: Cryogenic half wave plate rotator, design and performance". Journal of Cosmology and Astroparticle Physics 2022, nr 04 (1.04.2022): 039. http://dx.doi.org/10.1088/1475-7516/2022/04/039.
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Abstract Setting an upper limit or detection of B-mode polarization imprinted by gravitational waves from Inflation is one goal of modern large angular scale cosmic microwave background (CMB) experiments around the world. A great effort is being made in the deployment of many ground-based, balloon-borne and satellite experiments, using different methods to separate this faint polarized component from the incoming radiation. QUBIC exploits one of the most widely-used techniques to extract the input Stokes parameters, consisting in a rotating half-wave plate (HWP) and a linear polarizer to separate and modulate polarization components. QUBIC uses a step-by-step rotating HWP, with 15° steps, combined with a 0.4°s-1 azimuth sky scan speed. The rotation is driven by a stepper motor mounted on the cryostat outer shell to avoid heat load at internal cryogenic stages. The design of this optical element is an engineering challenge due to its large 370 mm diameter and the 8 K operation temperature that are unique features of the QUBIC experiment. We present the design for a modulator mechanism for up to 370 mm, and the first optical tests by using the prototype of QUBIC HWP (180 mm diameter). The tests and results presented in this work show that the QUBIC HWP rotator can achieve a precision of 0.15° in position by using the stepper motor and custom-made optical encoder. The rotation induces <5.0 mW (95% C.L) of power load on the 4 K stage, resulting in no thermal issues on this stage during measurements. We measure a temperature settle-down characteristic time of 28 s after a rotation through a 15° step, compatible with the scanning strategy, and we estimate a maximum temperature gradient within the HWP of ≤ 10 mK. This was calculated by setting up finite element thermal simulations that include the temperature profiles measured during the rotator operations. We report polarization modulation measurements performed at 150 GHz, showing a polarization efficiency >99% (68% C.L.) and a median cross-polarization χPol of 0.12%, with 71% of detectors showing a χPol + 2σ upper limit <1%, measured using selected detectors that had the best signal-to-noise ratio.
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Malael, I., i V. Dragan. "Numerical and Experimental Efficiency Evaluation of a Counter-Rotating Vertical Axis Wind Turbine". Engineering, Technology & Applied Science Research 8, nr 4 (18.08.2018): 3282–86. http://dx.doi.org/10.48084/etasr.2231.
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This paper investigates the concept of a concentric counter-rotating vertical axis wind turbine (VAWT), consisting of a two stage vertical H-type turbine with three blades on each stage. The model has an inner and an outer stage, rotating in opposition to each other. Both numerical and experimental tests have been performed in order to validate this new concept. Numerical analysis is based on the use of 2.5-dimensional, unsteady simulations using a DOF type of analysis which allows for the two stages to self-adjust their rotation speed. Sliding mesh conformal interfaces are defined between these subdomains to minimize numerical artifacts such as artificial relations or entropy changes. Fully turbulent URANS were carried out in Ansys Fluent software. One key outcome was the momentum coefficient for each stage at different tip wind speed values. Another, more qualitative, outcome is the analysis of vortex shedding, impingement and overall interaction between the stages at different positions and scenarios. Ultimately, the numerical results have been validated using a scaled experimental device which was analyzed in the wind tunnel at different free stream speeds.
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Ebus, Tobias, Markus Dietz i Andreas Hupfer. "Experimental and numerical studies on small contra-rotating electrical ducted fan engines". CEAS Aeronautical Journal 12, nr 3 (29.05.2021): 559–71. http://dx.doi.org/10.1007/s13272-021-00517-7.
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AbstractElectrical propulsion has been identified as one of the key fields of future research within the aerospace sector. The Institute of Aeronautical Engineering at the Universität der Bundeswehr München aims to contribute to the ongoing development of small-sized electrical ducted fan engines with a thrust in the range of 100 N. A special emphasis is placed on electrically powered contra-rotating fan stages. When compared to a conventional rotor–stator stage, contra-rotating fan stages allow for a more compact design, considering a given pressure ratio, or an increased pressure ratio at a constant fan diameter. Since numerous new aircraft concepts are presently being developed, a high demand for compact and powerful electrically driven engines arises. Electrically driven contra-rotating fan engines provide a high potential in terms of compactness, emissions and efficiency. Using electric motors offers the ability to overcome common issues, such as design and integration of a contra-rotating stage into a gas turbine. An innovative new engine design featuring such a contra-rotating stage is developed and tested at one of the Institute’s test benches for electrical propulsion. Key components are two brushless motors powering the fan stage, one for each rotor. Various operation points are investigated experimentally during an extensive test campaign. Experimental results are compared to results of numerical simulations computed by ANSYS CFX. Results indicate a good agreement between experiment and simulation. The engine is running very smooth throughout all tested operation points. Yet, intensive heating up of the electric motors and high-temperature zone are found to be an issue at higher rotation speeds.
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Tuszynski, Jack A., i Richard Gordon. "A mean field Ising model for cortical rotation in amphibian one-cell stage embryos". Biosystems 109, nr 3 (wrzesień 2012): 381–89. http://dx.doi.org/10.1016/j.biosystems.2012.05.007.
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Stoneham, E., L. Witt, Q. Paterson, L. Martin i B. Thoma. "P101: The development of entrustable professional activity reference cards to support the implementation of Competence by Design in emergency medicine". CJEM 21, S1 (maj 2019): S100. http://dx.doi.org/10.1017/cem.2019.292.
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Innovation Concept: Competence by Design (CBD) was implemented nationally for Emergency Medicine (EM) residents beginning training in 2018. One challenge is the need to introduce residents to Entrustable Professional Activities (EPAs) that are assessed across numerous clinical rotations. The Royal College's resources detail these requirements, but do not map them to specific rotations or present them in a succinct format. This is problematic as trainees are less likely to succeed when expectations are unclear. We identified a need to create practical resources that residents can use at the bedside. Methods: We followed an intervention mapping framework to design two practical, user-friendly, low-cost, aesthetically pleasing resources that could be used by residents and observers at the bedside to facilitate competency-based assessment. Curriculum, Tool or Material: First, we designed a set of rotation- and stage-specific EPA reference cards for the use of residents and observers at the bedside. These cards list EPAs and clinical presentations likely to be encountered during various stages of training and on certain rotations. Second, we developed a curriculum board to organize the EPA reference cards by stage based upon our program's curriculum map. The curriculum board allows residents to view the program's curriculum map and the EPAs associated with each clinical rotation at a glance. It also contains hooks to hang and store extra cards in an organized manner. Conclusion: We believe that these practical and inexpensive tools facilitated our residency program's transition to competency-based EPA assessments. Anecdotally, the residents are using the cards and completing the suggested rotation-specific EPAs. We hope that the reference cards and curriculum board will be successfully incorporated into other residency programs to facilitate the introduction of their EPA-based CBD assessment system.
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Soni, Krupa M., Urmi Bhatt i Vidhya Solanki. "Patterns of Range of Motion Restriction in Subjects with Adhesive Capsulitis". International Journal of Health Sciences and Research 11, nr 6 (22.06.2021): 337–41. http://dx.doi.org/10.52403/ijhsr.20210650.
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Background: Adhesive capsulitis is one of the most common problems of the arm. It is a painful and disabling condition and the etiology is unclear. Adhesive capsulitis is caused by tightening of the joint capsule and results in stiffness and pain. Adhesive capsulitis occurs in three distinct stages. Freezing stage, Frozen stage & Thawing stage. Till date, adhesive capsulitis remains to be more of a clinical diagnosis rather than radiological. Cyriax’s proposed shoulder capsular pattern was external rotation most limited followed by abduction followed by internal rotation. It remains unclear whether this pattern is exists in all the phases of adhesive capsulitis or not. Aim: To identify pattern of restriction of ROM in subjects with adhesive capsulitis in three phases of adhesive capsulitis. Methodology: The study included 60 subjects with idiopathic adhesive capsulitis. Passive ROM for shoulder Abduction, internal and external rotation was measured with universal Goniometer. Results & Conclusion: Findings suggest that various patterns of restrictions were found in different phase of Adhesive capsulitis. Key words: Adhesive capsulitis, Shoulder passive ROM, Pattern of restriction.
Rozprawy doktorskie na temat "One stage rotation"
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Springfield, James L. "Spectroscopy and Structure of Intermolecular Clusters and Rotational State-To-State Differential Cross-Sections for the HCI-X Collison System". Thesis, Griffith University, 2005. http://hdl.handle.net/10072/365402.
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One Colour-Resonant Two-Photon Ionisation, coupled with a supersonic expansion was used to study the rotationally cold excited electronic states of the water clusters of ortho-, meta- and para-difluorobenzene. Ground state rotational constants obtained through ab-initio calculations allowed rotational band contour simulations of these species to be performed, elucidating structural and spectroscopic features such as rotational band types, directions of transition dipole moments and excited state geometries. Confidence in the calculated ground state geometries, obtained through successful simulation of the rotational band contours, provided strength to the credibility of the vibrational frequencies acquired via these calculations. Analysis of ground state dispersed fluorescence spectroscopy utilising these ab-initio (geometry + frequency) optimisation calculations, allowed assignment of the ground state vibrational modes of each species. Furthermore, comparison of the assigned ground state modes with the excited state spectroscopy, affirmed assignment of the low frequency Van der Waals modes along with the higher frequency aromatic ring modes of these cluster species.
A novel technique that produces pseudo-selective excitation of ground state aromatic-rare gas cluster ions was used to assign the vibrational transitions of the D3[less than]D0 electronic excitation spectrum of para-Difluorobenzene+-Argonn=1,2. This technique works on the principle of providing varying degrees of excess energy to the ground state of the cluster ion, as well as altering the Franck-Condon factors for excitation to the D3 electronic state. Measurement of the redshifts for each pDFB-R (where R= Ar1, Ar2, Kr1, Kr2) cluster, revealed that the addition of a second rare-gas adatom doubled the redshift, and that Krypton ad-atoms produced a stronger redshift than argon as expected. It was also noted that the addition of a positive charge to the complex increased the redshift of the complexes, in accordance with our expectations. Rotational state-resolved differential cross sections (DCS's) for rotationally inelastic collisions of HCl with Ne, Ar, and Kr at ~545, ~538, and ~526 cm-1 of collision energy, respectively, were measured using velocity-mapped ion imaging. For each rotational state, the observed DCS's were found to be qualitatively similar. As collider mass was increased, the differential cross section became increasingly forward scattered. Calculations suggest that much of this difference is due to kinematic effects, but that the potential energy surface should be slightly more anisotropic for heavier colliders.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Science
Full Text
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Bréant, Christian. "Développement de lasers infrarouges accordables de haute pureté spectrale : application à la spectroscopie hyperfine des molécules HF et SF(6)". Paris 13, 1985. http://www.theses.fr/1985PA132010.
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Les développements de deux spéctromètres de saturation à ultra-haute résolution dans le domaine infrarouge, l'un dans la région spectrale 9-12 mu m et l'autre accordable de 2,3 a 3,2 mu m sont exposés en detail. La stabilisation en fréquence d'un laser à CO(2) conventionnel ou guide d'ondes au niveau de la dizaine de hertz ainsi que l'obtention d'une stabilité meilleure que 1 khz pour le laser à centres colores soulignent le role cle de ces oscillateurs dans la chaine de raccordement de fréquence de l'horloge à cesium vers le domaine visible. L'étude des interactions hyperfines est presentée dans le cas des molécules diatomiques héteronucleaires (hf) et des toupies spheriques du groupe ponctuel O(h) (sf(6)). Grace a l'enregistrement de structures hyperfines tres bien resolues, de nombreux effets ont etes mis en evidence et interpretes à l'aide du formalisme tensoriel (dans le groupe (l)o(3) x O(h)) en particulier : l'interaction de spin-vibration (bande upsilon (3) de sf(6)), les mélanges d'états de types de symétrie differents (sf(6)), les corrections ro-vibrationnelles à l'interaction de spin-rotation (hf et sf(6)), les structures superhyperfines (sf(6))
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Hsieh, Hsingchuan, i 謝幸娟. "One-stage Rotation Method For Second-order Factor Analysis". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/12119684686134489819.
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碩士國立中正大學
心理學研究所
100
Traditionally, in second-order factor analysis, the first-order factors are extracted and such factors are subsequently regarded as new observed variables so second- order factors are extracted. Since the second-order factors are determined by the first-order ones, the conventional two-staged method will cause problems if the preselection for the first-order factors is inappropriate. An intuitive way to solve the problem is, when extracting the first-order factors, to evaluate its effect upon the second -order ones. Specifically, we’d like to define a new rotation criterion to assess the performance for both pattern matrices simultaneously. Such estimation process is hence reduced to a one-staged method. To testify the efficiency of such criterion, we analyzed three simulated and one real datasets, then compared the results between the two-staged and one-staged methods. The results showed that the proposed method performed better when the first-order pattern matrix is complex but worse when so is the second-order pattern matrix. The proposed method can also apply to other rotation criteria. Besides, assumption about the correct numbers of first- and second-order factors is not always the case. A future research for determining the numbers of these factors is needed.
Książki na temat "One stage rotation"
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Vallejo Maldonado, Pablo Ramon, i Nikolay Chaynov. Kinematics and dynamics of automobile piston engines. ru: INFRA-M Academic Publishing LLC., 2019. http://dx.doi.org/10.12737/989072.
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The fundamentals of kinematics and dynamics of transport piston internal combustion engines made using different layout schemes are presented. Along with the traditional in-line, V-shaped, including oppositional, arrangement of cylinders, schemes with "staggered" arrangement of cylinders in the block at the displaced connecting rod necks of the crankshaft of the engine are considered. The kinematics of the coaxial crank mechanism is considered in detail. The questions of dynamics with reduction of calculated dependences of forces, moments, a choice of a rational order of work of cylinders in relation to the considered kinematic schemes are in detail stated. Considerable attention is paid to the unevenness of the crankshaft rotation speed and engine balancing. The loads on the main and connecting rod bearings of the crankshaft, the knowledge of which is necessary in determining the bearing capacity of bearing units, are also considered.
Meets the requirements of the Federal state educational standards of higher education of the last generation.
For students of higher educational institutions studying in the direction of training 23.03.03 "Operation of transport and technological machines and complexes" and related areas.
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Bachmann, Hugo, i Walter Ammann. Vibrations in Structures. Zurich, Switzerland: International Association for Bridge and Structural Engineering (IABSE), 1987. http://dx.doi.org/10.2749/sed003e.
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<p>«Vibrations in Structures» concentrates on vibrations in structures as excited by human motion or machine operation. Man-induced vibrations may arise from walking, running, skipping, dancing, etc. They occur mostly in pedestrian structures, office buildings, gymnasia and sports halls, dancing and concert halls, stadia, etc. Existing publications treat by and large some isolated aspects of the problem; the present one attempts, for the first time, a systematic survey of man-induced vibrations. Machine-induced vibrations occur during the operation of all sorts of machinery and tools with rotating, oscillating or thrusting parts. The study concentrates rather on small and medium size machinery placed on floors of industrial buildings and creating a potential source of undesirable vibrations. The associated questions have rarely been tackled to date; they entail probiems similar to those of man-induced vibrations.</p> <p>The book is consciously intended to serve the practising structural engineer and not primarily the dynamic specialist. It should be noted that its aim is not to provide directions on how to perform comprehensive dynamic computations. Instead, it attempts the following:</p> <ol> <li>to show where dynamic problems could occur and where a word of caution is good advice;</li> <li>to further the understanding of the phenomena encountered as well as of the underlying principles;</li> <li>to impart the basic knowledge for assessing the dynamic behaviour of the structures or structural elements;</li> <li>to describe suitable measures, both preventive to be applied in the design stage and remedial in the case of rehabilitation.</li> </ol>
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Pinna, Baingio. On the Pinna Illusion. Oxford University Press, 2017. http://dx.doi.org/10.1093/acprof:oso/9780199794607.003.0074.
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The Pinna illusion is the first case of visual illusion showing a rotating motion phenomenon. Squares, arranged in two concentric rings, show a strong counter-rotation effect. The inner ring of the squares appears to rotate counterclockwise and the outer ring clockwise when the observer’s head is slowly moved toward the figure while the gaze is kept fixed in the center of the stimulus pattern. The direction of rotation is reversed when the observer’s head moves away from the stimulus. The speed of the illusory rotation is proportional to the one of the motion imparted by the observer. While the way each individual check receives a local illusory motion signal can be explained by the response of direction-selective neurons at the earliest cortical stage of visual processing, the whole illusory rotational motion can be thought to be sensed by the higher cortical area, which collates all the signals provided by the local motion checks.
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Henriksen, Niels Engholm, i Flemming Yssing Hansen. Introduction. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198805014.003.0001.
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This introductory chapter considers first the relation between molecular reaction dynamics and the major branches of physical chemistry. The concept of elementary chemical reactions at the quantized state-to-state level is discussed. The theoretical description of these reactions based on the time-dependent Schrödinger equation and the Born–Oppenheimer approximation is introduced and the resulting time-dependent Schrödinger equation describing the nuclear dynamics is discussed. The chapter concludes with a brief discussion of matter at thermal equilibrium, focusing at the Boltzmann distribution. Thus, the Boltzmann distribution for vibrational, rotational, and translational degrees of freedom is discussed and illustrated.
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Kislyuk, V. S. Moon in the Sky… PH “Akademperiodyka”, 2009. http://dx.doi.org/10.15407/akademperiodyka.126.120.
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The book “Moon in the Sky…” consists of two chapters: “The Wonderful World of Selena” and “Return to the Moon.” The first of them tells about the current state of the study of the Moon: its origin, features of rotational motion, nature and internal structure. The second section discusses the problems of further study and development of the Earth's natural satellite with the help of spacecraft and the creation of populated scientific and research-production bases on its surface. The appendices provide basic information about the Moon, a glossary of lunar terms, a chronology of lunar explorations using spacecraft, a map of the visible side of the Moon for observations with binoculars or a school telescope. The book “Moon in the Sky…” is intended for a wide range of readers.
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Martin, Jeffrey T. Sentiment, Reason, and Law. Cornell University Press, 2019. http://dx.doi.org/10.7591/cornell/9781501740046.001.0001.
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What if the job of police was to cultivate the political will of a community to live with itself (rather than enforce law, keep order, or fight crime)? This book describes a world where that is the case. The Republic of China on Taiwan spent nearly four decades as a single-party state under dictatorial rule (1949–1987) before transitioning to liberal democracy. This book describes the social life of a neighborhood police station during the first rotation in executive power following the democratic transition. It shows an apparent paradox of how a strong democratic order was built on a foundation of weak police powers, and demonstrates how that was made possible by the continuity of an illiberal idea of policing. The conclusion from this paradox is that the purpose of the police was to cultivate the political will of the community rather than enforce laws and keep order. As the book shows, the police force in Taiwan exists as an “anthropological fact,” bringing an order of reality that is always, simultaneously and inseparably, meaningful and material. It unveils the power of this fact, demonstrating how the politics of sentiment that took shape under autocratic rule continued to operate in everyday policing in the early phase of the democratic transformation, even as a more democratic mode of public reason and the ultimate power of legal right were becoming more significant.
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Kokkonen, Andrej, Jørgen Møller i Anders Sundell. The Politics of Succession. Oxford University PressOxford, 2022. http://dx.doi.org/10.1093/oso/9780192897510.001.0001.
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Abstract The problem of leadership succession is perennial; the death of the ruler poses a significant threat to the stability of any polity. Arranging for a peaceful and orderly succession has been a formidable challenge in most historical societies, and it continues to be a test that modern authoritarian regimes regularly face and often fail. There is in practice no optimal solution to the problem of who should succeed the ruler, at least not when power is vested in one person. The absence of a successor causes uncertainty and plotting; the existence of one creates another centre of power, with dangerous implications. This book documents how successions have historically been moments of violence and insecurity: The succession wars known from European history are simply the tip of the iceberg. But the book also shows that the development and spread of primogeniture—the eldest-son-taking-the-throne—mitigated the problem of succession in Europe in the period after AD 1000. Primogeniture presented a reasonable compromise that in ‘normal’ circumstances allowed for an orderly transfer of power while minimizing threats to the incumbent ruler. In a long-term historical perspective, father-to-son successions—in the context of hereditary monarchy—therefore created political stability and facilitated state-formation. Today, representative democracy does the same, but in a very different way where frequent rotations in power and guarantees against the misuse of power are used to lessen the stakes of leadership succession.
Części książek na temat "One stage rotation"
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Belkin, Ilya, Alexander Rezanov i Dmitry Yudin. "Center3dAugNet: Effect of Rotation Representation on One-Stage Joint Car Detection and 6D-Pose Estimation". W Studies in Computational Intelligence, 330–42. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-19032-2_35.
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Cortada, Laura. "Technologies for integrated nematode management in smallholder farming systems: no one-size-fits-all." W Integrated nematode management: state-of-the-art and visions for the future, 457–62. Wallingford: CABI, 2021. http://dx.doi.org/10.1079/9781789247541.0063.
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Abstract In this chapter, the need to take a more critical look at the highly precarious and vulnerable situation of smallholder farming systems, the predominant type of the agricultural output worldwide, is emphasized. These farmers represent 98% of the farmers in the world that sustain the local production of staple crops such as rice, maize, cassava, groundnut and millet. Although there is some disparity in the figures, recent data estimates that there are between 380 and 500 million smallholder farming households globally. The productivity of the smallholders' farms depends on soil health and quality, agroecological conditions (irrigated versus rainfed), access to agricultural inputs and new technologies. These last two also critically influence smallholders' ability to manage pests and diseases, including plant parasitic nematodes (PPN). This chapter discusses the epidemiological perspective, diagnostics and surveillance, alternate host and in-field spread of PPN. Breeding programmes for PPN resistance, seed delivery system, importance of clean planting material, influence of land availability to smallholders' ability to practice fallow and rotation for nematode management are described. The use of trap crops, cover crops, nematicides and biological control agents for nematode suppression are also discussed. Future developments aimed at promoting the progress of smallholder farming systems are also mentioned.
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Aderinoye-Abdulwahab, S. A., i T. A. Abdulbaki. "Climate Change Adaptation Strategies Among Cereal Farmers in Kwara State, Nigeria". W African Handbook of Climate Change Adaptation, 509–22. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-45106-6_228.
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AbstractAgriculture is the art and science of food production which spans soil cultivation, crop growing, and livestock rearing. Over the years, it has served as a means of employment and accounts for more than one-third of total gross domestic product. Cereals, which include rice, maize, and sorghum, are the major dietary energy suppliers and they provide significant amounts of protein, minerals (potassium and calcium), and vitamins (vitamin A and C). The growth and good yield of cereal crop can be greatly influenced by elements of weather and climate such as temperature, sunlight, and relative humidity. While climate determines the choice of what plant to cultivate and how to cultivate, it has been undoubtedly identified as one of the fundamental factors that determine both crop cultivation and livestock keeping. The chapter, though theoretical, adopted Kwara State, Nigeria, as the focus due to favorable weather conditions that support grains production. It was observed that the effect of climate change on cereal production includes: drastic reduction in grains production, reduction in farmers’ profit level, increment in cost during production, diversification to nonfarming activities, and discouragement of youth from participating in agricultural activities. Also, the adopted coping strategies employed by farmers in the focus site were early planting, planting of improved variety, irrigation activities, alternates crop rotation, and cultivation of more agricultural areas. The chapter thus concluded that climate change has negative impact on cereals production and recommends that government should provide communal irrigation facilities that will cushion the effect of low rains on farmers’ productivity, while early planting and cultivation of drought-resistant cultivars should be encouraged.
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Eliseev, Alexander A., Tatiana A. Kalashnikova, Andrey V. Filippov i Evgeny A. Kolubaev. "Material Transfer by Friction Stir Processing". W Springer Tracts in Mechanical Engineering, 169–88. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-60124-9_8.
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AbstractMechanical surface hardening processes have long been of interest to science and technology. Today, surface modification technologies have reached a new level. One of them is friction stir processing that refines the grain structure of the material to a submicrocrystalline state. Previously, the severe plastic deformation occurring during processing was mainly described from the standpoint of temperature and deformation, because the process is primarily thermomechanical. Modeling of friction stir welding and processing predicted well the heat generation in a quasi-liquid medium. However, the friction stir process takes place in the solid phase, and therefore the mass transfer issues remained unresolved. The present work develops the concept of adhesive-cohesive mass transfer during which the rotating tool entrains the material due to adhesion, builds up a transfer layer due to cohesion, and then leaves it behind. Thus, the transfer layer thickness is a clear criterion for the mass transfer effectiveness. Here we investigate the effect of the load on the transfer layer and analyze it from the viewpoint of the friction coefficient and heat generation. It is shown that the transfer layer thickness increases with increasing load, reaches a maximum, and then decreases. In so doing, the average moment on the tool and the temperature constantly grow, while the friction coefficient decreases. This means that the mass transfer cannot be fully described in terms of temperature and strain. The given load dependence of the transfer layer thickness is explained by an increase in the cohesion forces with increasing load, and then by a decrease in cohesion due to material overheating. The maximum transfer layer thickness is equal to the feed to rotation rate ratio and is observed at the axial load that causes a stress close to the yield point of the material. Additional plasticization of the material resulting from the acoustoplastic effect induced by ultrasonic treatment slightly reduces the transfer layer thickness, but has almost no effect on the moment, friction coefficient, and temperature. The surface roughness of the processed material is found to have a similar load dependence.
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Neagoe, Mircea, Codruta Jaliu, Radu Saulescu i Petru A. Simionescu. "Steady-State Response of a Dual-Rotor Wind Turbine with Counter-Rotating Electric Generator and Planetary Gear Increaser". W Proceedings of the 2020 USCToMM Symposium on Mechanical Systems and Robotics, 106–15. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-43929-3_10.
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Neagoe, Mircea, Radu Saulescu, Codruta Jaliu i Nadia Cretescu. "Steady-State Modeling and Simulation of a 1-DOF Dual-Input and Dual-Output Planetary Speed Increaser for Counter-Rotating Wind Turbines". W Proceedings of the 2022 USCToMM Symposium on Mechanical Systems and Robotics, 20–31. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-99826-4_3.
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Mareš, Martin, Otakar Horejš i Pravoslav Nykodym. "An Indicative Model Considering Part of the Thermo-Mechanical Behaviour of a Large Grinding Machine". W Lecture Notes in Production Engineering, 54–66. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-34486-2_5.
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AbstractMachine tool (MT) thermal errors are an important element in ma-chined workpiece inaccuracies. In the past few decades, thermal errors associated mainly with one particular source (e.g. spindle or environment), have been successfully reduced by SW compensation techniques such as multiple linear re-gression analysis, finite element method, neural network, transfer function (TF) within similar calibration and verification conditions. An approach based on TFs is used for thermal error modelling in this research. This method respects basic heat transfer mechanisms in the MT and requires a minimum of additional gauges. The approach provides insight into the share of each source in the total machine thermal error through a combination of linear parametric models. The aim of this research is to develop an indicative model for a large grinding machine with predictive functionality focused on part of the thermo-mechanical behaviour within different configurations of the headstock, tailstock and workpiece. Unlike a compensation model, an indicative model has no connection to the MT feed drives and can only provide the machine operator with information regarding the actual direction and relative magnitude along with prediction of the time constant and steady state of the non-stationary thermal error. The second aim is to compare the difficulty of measuring at the stator and rotating machine part levels, the thermal behaviour linearity at both levels and the possibility of upgrading the indicative model to a compensation model to extend industrial applicability.
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Borom, Marcus P. "Role of Earth-Moon rotational dynamics in the shaping of the surface of our planet". W In the Footsteps of Warren B. Hamilton: New Ideas in Earth Science. Geological Society of America, 2022. http://dx.doi.org/10.1130/2021.2553(22).
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ABSTRACT The age of the Moon (1.55–1.78 b.y. old) as calculated from its regression as a function of geological time is much younger than the currently accepted age (ca. 4.52 Ga) determined by radiometric dating of lunar samples collected by Apollo astronauts. This discrepancy has posed a serious challenge for planetary scientists to account satisfactorily for the formation and subsequent breakup of Pangea. Conventional orbital models of the Earth-Moon system cannot explain why Pangea formed on only one hemisphere of Earth, whereas this study’s proposed two-stage rotation model can provide a plausible explanation. Calculations and a plot of the Earth-Moon separation distance against geologic age suggest that, during their first ~3.0 b.y., Earth and the Moon were mutually tidally locked, rotating as an integrated unit about a barycenter (designated as stage I rotation). Beginning 1.55 Ga, however, Earth disengaged from its tidal lock with the Moon and entered its current orbital mode (designated as stage II rotation). The dynamics associated with the two rotational modes of the Earth-Moon system throughout Earth’s history are hypothesized to constitute the driving forces for the migration and coalescence of landmasses during stage I rotation to create Pangea, and its ultimate breakup and drifting during stage II rotation.
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Toma Bane Karash, Emad, i Mohammad Takey Elias Kassim. "The Microstructure and Mechanical Properties of the Aluminum Alloy (AA 6061 T6) Under the Effect of Friction Stirs Processing". W Recent Advancements in Aluminum Alloys [Working Title]. IntechOpen, 2023. http://dx.doi.org/10.5772/intechopen.109590.
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The following chapter study the friction stir processes (FSP) is used to improve the surface characteristics of the alloy AA6061-T6 on the surface topography, hardness, tension mechanical characteristics, and microstructures of aluminum alloy, the impacts of friction stir process tool travel and rotation speeds were investigated. All friction stir processes (FSW) in this investigation used a cylindrical tool without a pin that had a 20 mm diameter, rotated at different rotating speeds 800, 1000, 1250, and 1600 rpm, and at different travel speeds 32, 63, and 80 mm per minute. The examination of the current study’s data and the test results showed that in stir friction processes, hardness rises with cutting depth. The study of the crystal structure showed that the hardness increased by twice as much for two stages as it did for one stage. Additionally, it was observed that as cutting depth increased, the size of the granules representing engineering defects grew smaller. Additionally, in the case of two stages, the ratio of granule size to friction was twice as high as in the case of one step. According to the results, using a single-stage friction stir process increased yield strength by 18% and tensile strength by 9.5%, while using a two-stage friction stir process increased yield strength by 20.4% and tensile strength by 11.5% when compared to metal basis.
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Blow, David. "Crystals and symmetry". W Outline of Crystallography for Biologists. Oxford University Press, 2002. http://dx.doi.org/10.1093/oso/9780198510512.003.0006.
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One of the fascinations of crystallography is the beautiful external appearance of crystals (Fig. 2.1), and the corresponding beauty of the atomic arrangements within them. At an early stage of studying a crystal, a crystallographer needs to analyse its underlying symmetry. This must be done because the crystallographic results must satisfy this symmetry and are constrained by it. It is needed to decide on the appropriate strategy for observation of X-ray scattering by the crystal. It is also essential to know the precise symmetry when interpreting the scattering data to obtain the crystal structure. The analysis of many crystal structures has been delayed because of mistakes in the symmetry assignment, and some have been incorrectly analysed. This chapter sets out to give an overview of crystal symmetry. It does not provide an exhaustive presentation. In particular, we shall concentrate on the symmetrical arrangements of chiral objects, in which mirror symmetry is forbidden. Much more detail about crystal symmetry can be found in many textbooks of crystallography, and a complete reference guide is provided in International Tables for Crystallography, Volume A (see Further Reading at the end of this chapter). An object is symmetrical if, after some operation has been carried out, the result is indistinguishable from the original object. Consider, for example, an equilateral triangle. If the triangle is rotated 120° about its centre, the resulting triangle is, in all respects, identical to the original triangle. This means that a second 120° rotation, producing a total rotation of 240°, also makes no change to the object. A third 120° rotation makes, of course, a 360° rotation, bringing the triangle back to its original orientation. So these rotations are called 3-fold rotation operations, and the equilateral triangle is said to possess 3-fold symmetry. The meaning of 3-fold symmetry is that the object may be rotated repeatedly by 360°/3 120° about its symmetry axis without changing it. Similarly 2-fold symmetry refers to rotation by 360°/2 180° and 6-fold symmetry refers to rotation by 60°. A left hand has no symmetry. Reflect it in a mirror and what you see looks like a right hand.
Streszczenia konferencji na temat "One stage rotation"
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Dittmann, M., K. Dullenkopf i S. Wittig. "Direct-Transfer Preswirl System: A One Dimensional Modular Characterization of the Flow". W ASME Turbo Expo 2003, collocated with the 2003 International Joint Power Generation Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/gt2003-38312.
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In high-efficiency gas turbine engines, the cooling air for the high pressure turbine stage is expanded through stationary preswirl nozzles, transferred through the preswirl chamber and delivered to the blade feed holes of the rotor. By accelerating the cooling air in the direction of rotation, the total temperature relative to the rotor disk and the pressure losses occurring at the receiver hole inlet can be reduced. The discharge behavior of a direct-transfer preswirl system has been investigated experimentally for different number of receiver holes and different inlet geometries, varying axial gap widths between stator and rotor and for rotational Reynolds numbers up to Reφ = 2:3 × 106. The discharge coefficients of the preswirl nozzles are given in the absolute frame of reference while the definition of the discharge coefficients of the receiver holes is applied to the rotating system in order to consider the work done by the rotor. A momentum balance is used to evaluate the deflection of the preswirled air entering the receiver holes. The flow in the preswirl chamber is characterized by introducing an effective velocity of the cooling air upstream of the rotor disk. The influences of geometrical parameters and operating points are reported and discussed in this paper.
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Ventosa-Molina, Jordi, Björn Koppe, Martin Lange, Ronald Mailach i Jochen Fröhlich. "Effects of Rotation on the Flow Structure in a Compressor Cascade". W ASME Turbo Expo 2021: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/gt2021-58793.
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Abstract In turbomachines, rotors and stators differ by the rotation of the former. Hence, half of each stage is directly influenced by rotation effects. The influence of rotation on the flow structure and its impact on the performance is studied through Wall-Resolving Large Eddy Simulations of a rotor with large relative tip gap size. The simulations are performed in a rotating frame with rotation accounted for through a Coriolis force term. In a first step experimental results are used to provide validation. The main part of the study is the comparison of the results from two simulations, one representing the rotating configuration, one with the Coriolis force removed, without any other change. This setup allows very clean assessment of the influence of rotation. The turbulence-resolving approach ensures that the turbulent flow features are well represented. The results show a significant impact of rotation on the secondary flow. In the tip region the Tip Leakage Vortex is enlarged and destabilised. Inside the tip gap the flow is altered as well, with uniformization in the rotating case. At the blade midspan, no significant effects are observed on the suction side, while an earlier transition to turbulence is found on the pressure side. Near the hub, rotation effects are shown to reduce the corner separation significantly.
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Ooten, Michael K., Richard J. Anthony, Andrew T. Lethander i John P. Clark. "Unsteady Aerodynamic Interaction in a Closely-Coupled Turbine Consistent With Contra-Rotation". W ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/gt2015-42416.
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The focus of the study presented here was to investigate the interaction between the blade and downstream vane of the stage-and-one-half transonic turbine via CFD analysis and experimental data. A Reynolds-Averaged Navier-Stokes (RANS) flow solver with the two-equation Wilcox 1998 k-ω turbulence model was used as the numerical analysis tool for comparison for all of the experiments conducted. The rigor and fidelity of both the experimental tests and numerical analysis methods were built through two- and three-dimensional steady-state comparisons, leading to three-dimensional time-accurate comparisons. This was accomplished by first testing the midspan and quarter-tip two-dimensional geometries of the blade in a linear transonic cascade. The effects of varying the incidence angle and pressure ratio on the pressure distribution were captured both numerically and experimentally. This was used during the stage-and-one-half post-test analysis to confirm that the target corrected speed and pressure ratio were achieved. Then, in a full annulus facility, the first vane itself was tested in order to characterize the flowfield exiting the vane that would be provided to the blade row during the rotating experiments. Finally, the full stage-and-one-half transonic turbine was tested in the full annulus cascade with a data resolution not seen in any studies to date. A rigorous convergence study was conducted in order to sufficiently model the flow physics of the transonic turbine. The surface pressure traces and the Discrete Fourier Transforms thereof were compared to the numerical analysis. Shock trajectories were tracked through the use of two-point space-time correlation coefficients. Very good agreement was seen when comparing the numerical analysis to the experimental data. The unsteady interaction between the blade and downstream vane was well captured in the numerical analysis.
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Huang, Chao-Min, i Hai-Jun Su. "Design of a Compliant XY Positioning Stage With Large Workspace". W ASME 2015 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/detc2015-47271.
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Flexure mechanisms become more and more popular because of their better performance, easy maintenance, wear-free properties and predictability of kinematic variables changes. Comparing to traditional ball bearings or linear slides, however, range of motion limits flexure mechanisms applications in existing market. This paper presents the design of a novel planar XY stage synthesizing the benefits of parallel and serial kinematic constraint. By parallel connecting two mechanisms: the vertical and horizontal subsystems, which both have degrees of freedom (DOFs) in primary moving direction but different degrees of constraints (DOCs) in rotation, this system is able to reduce three parasitic rotation angles (pitch, roll and yaw) less than one micro radium and also have motion range up to 40mm × 40mm. Analytical model and finite element analysis (FEA) are present to validate the performance of this stage and also determine appropriate operation parameters.
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Nie, Chaoqun, Jingyi Chen, Xingmin Gui, Qing Yu i Tongqing Wang. "Unsteady Transition Characteristics of Rotating Stall in a Single-Stage Transonic Axial Compressor". W ASME 1999 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/99-gt-432.
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The unsteady transition characteristics of rotating stall have been studied experimentally in a single-stage transonic axial compressor. Three tested conditions in the near design and below design speed range, at tip relative Mach numbers from 1.26 to 1.0, were performed. The characteristics of rotating stall were studied by its dynamic behavior on the scale of compressor circumference and also by the flow field details in the blade passage. The dynamic behavior was analyzed by the technique of successive frequency spectrum and the flow field details were studied through internal transient pressure patterns in the blade passage plotted by the dynamic pressure data measured on the compressor shroud. It has been shown that intermittent pre-stall perturbations are evident for all the tested speeds and distinct by the different time and length scale of their existence. These are also interpreted by the difference of pressure loading and shock structure visualized in the pressure plots in the blade passage during stall inception. The pre-stall perturbations, with rather scattered frequency spectra, grow into fully developed stall abruptly. Nevertheless, the frequency spectrum of rotating stall falls into constant fraction of the frequency of compressor rotation for all the tested conditions. The increasing trend of the amplitude of pressure oscillation of rotating stall while gathering at its frequency spectrum could be detected in the stage of stall inception. Based on these two observations, there is a possibility of warning the stall precursors even for the high speed transonic compressor like the one tested in this paper.
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Drewczynski, Marcin, Marek Solinski i Romuald Rzadkowski. "A Comparison of Two Load Transferring Methods in an Unsteady One-Way Fluid-Structure Interaction Analysis". W ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gt2012-69543.
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A full two-way aeroelasticity coupling analysis of rotating machinery and their main components requires considerable computational analysis and CPU time. This is why the most common methodology for this type of problem is a one-way coupling between fluid and structure. In this case, forces acting on rotor blades that result from a flow are introduced into a structural model of a blade as a local spot load in the centre of gravity or a series of local spot points deployed along the blade length. However, this method does not take into account how the forces change in a chordwise direction (along chord). An alternative way is to use the method of directly transferring the pressure field as a surface load from the CFD analysis to a structural model of a blade. In this case various interpolation methods are needed to transfer the results from the CFD mesh on to the structural mesh nodes. In this paper the authors compare how both methods of load transfer affect rotor blade stress and displacement levels during one period of rotation. Calculations were carried out for the first stage compressor blade of an aircraft engine. Ansys 12.1 was used to calculate the entire structure. Unsteady CFD calculations were carried out using Fluent for a 1.5 stage axial compressor model. For the numerical calculations a non-viscous flow was used. The unsteady forces were calculated on 10 control cross-sections of a rotor blade. The transient results obtained from the CFD calculations were transferred onto a structural rotor blade model using APDL language script. For both methods of load transference, transient displacements and transient stresses for the rotor blade were calculated. The harmonic analysis results were compared. Mesh sensivity analysis was also carried out for the structural model.
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Liu, Wei, Yunbo Yuan, Tao He i Donghua Wang. "Free Vibration Analysis of Two-Stage Planetary Gear With Friction". W ASME 2018 Noise Control and Acoustics Division Session presented at INTERNOISE 2018. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/ncad2018-6133.
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Considering the effect of teeth surface sliding friction, free vibration of two-stage planetary gears (TPG) is studied theoretically for the first time. The lateral-torsional coupling dynamic model and equation are established with three degrees of freedom: two translations and one rotation. The change rule of natural frequency is discussed with the case of first stage planetary gear’s number 4 and second stage planetary gear’s number 3, 4 and 5. Afterwards three vibration modes are summarized by calculating the free vibration. In order to understand the behavior of friction, the effect of friction on natural frequencies is analyzed for the case of considering friction and not considering friction. Furthermore, the ‘self-coupling’ phenomenon is obtained from the vibration of center component of TPG Meanwhile, the ‘mutual coupling’ is obtained between the first-stage planetary gear (FPG) and the second-stage planetary gear (SPG).
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Fortin, J., i W. C. Moffatt. "Inlet Flow Distortion Effects on Rotating Stall". W ASME 1990 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1990. http://dx.doi.org/10.1115/90-gt-215.
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For many years there has been a significant effort to better understand rotating stall/surge phenomena in axial compressors, as well as the effects of inlet flow distortions. Most experimental investigations to date, whether on laboratory compressors or on full scale jet engines, have tended to focus separately on the effects of these two flow disturbances on compressor performance. The purpose of the present study was to experimentally assess the influence of inlet flow distortions on the inception and nature of rotating stall in a full scale engine compressor. This paper reports results obtained for the first stage rotor of a 10-stage compressor subjected to screen-induced inlet pressure distortions. Previous investigations had shown that during part-speed operation, the front stages operated in rotating stall, and hot-film probe measurements made during the present study showed that the presence of the distortion screens did not affect the speed of the rotating stall pattern, but in some instances changed the number of cells present. However, low frequency flow fluctuations characteristic of surge were much more prevalent when the screens were in place. Also, the further the sensing probe was displaced tangentially in the rotor rotation direction from the screens, the more intense the fluctuations, leading one to conclude that the screens had a localized damping effect on the surge cycle.
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Günther, André, Wieland Uffrecht, Stefan Odenbach i Volker Caspary. "First Results of a New Test Rig for the Research on the Internal Air System of an Industrial Gas Turbine". W ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gt2012-68198.
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Improvement of the internal air system has great impact on the efficiency and power of gas turbines. This paper describes a new two-stage test rig for research on the cooling air supply of industrial gas turbines. The design is modeled on a simplified geometry of the internal cavities of the high pressure turbine with receiver holes simulating the restriction imposed by internal blade cooling flow circuits. The test rig consists of a rotor-stator cavity and a full rotating cavity. The Stage One supply and the Stage Two supply are separated inside the rotorstator cavity. The intended aim of the research is the branched cooling air supply. The rim seal flow, which effect on cavity flows is known to be non-trivial, is outside the scope of this area of interest. This paper concentrates on the flow path supplying the Stage Two. Variations of the axial gap size and the radial location of the connecting holes respectively the outlets of the rotor-stator cavity are described here. The air enters axially without pre-swirl at the outer radius of the stator and leaves the rotor-stator cavity through three rotating, axially directed connecting holes at a radius depending on the investigated case, which causes axial throughflow in Case 1 and radial inflow in Case 2. The experimental results show that the net cavity mass flow, presented in terms of a reduced mass flow parameter, increases with increasing pressure ratio, rotational Reynolds number and gap size. The increase due to a larger gap size depends on the rotation and is less prominent at higher rotational Reynolds numbers. An axial throughflow at the outer radius results in higher values of the reduced mass flow parameter, as compared to the case with radial inflow. The difference between the two cases increases with increasing rotational Reynolds number. Measured static pressure fluctuations inside the rotor-stator cavity due to the rotating nozzles can be raised up to ± 4% of the mean in the case with the small gap and the outlet at outer radius. The Pitot probe measurements show a low swirl ratio, radial outflow near the rotor and radial inflow close to the stator, which is consistent with Batchelor-type flow.
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Ashour, Mohammed, Mustafa Shalabi i S. G. Rengasamy. "Centrifugal Compressor Seal and Bearing Rubbing Due to a Destructive Repeatable Reverse Rotation". W ADIPEC. SPE, 2022. http://dx.doi.org/10.2118/211232-ms.
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Abstract This case study is focused on the diagnostics of an abnormal event observed during each compressor train shutdown and led to a seal failure later through a detailed analysis of historical transient data collected using an online vibration online monitoring software during shutdown mode to identify the root cause of this abnormal behavior. The unit consists of a centrifugal gas compressor (12440 RPM) driven by an induction electrical motor (3100 KW and 1790 RPM) through an increasing single stage double helical gearbox. Machine train was running smoothly during steady state condition. Compressor bearings showed high vibration levels during each shutdown event close to alarm setpoints during last year, however no one took care as it was happening only during shutdown. The unit was compressing a hazardous gas, and any failure or leak could lead to a major safety incident. Steady state data review showed good compressor rotor dynamics with acceptable vibration levels well below alarm set points, however during shutdown showed high vibration levels reaching alarm setpoints during shutdown. Review of the vibration and speed data through the online condition monitoring software showed symptoms of reverse rotation event repeating each shutdown after reaching zero speed. After 3 month of operation and several shutdown events encountered, a gas leak took place from the compressor. During the internal inspection, severe rubbing marks found in the compressor seals and the rotor found damaged at these areas. Also, the compressor inboard bearing found totally damaged. Major overhaul took place changing the rotor and overhauling the compressor parts. The non-return valve installed on the discharge was dismantled and overhauled. Compressor started up later and during the next shutdown the compressor bearings showed normal vibration behavior, and no reverse rotation events observed.
Raporty organizacyjne na temat "One stage rotation"
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Seginer, Ido, Louis D. Albright i Robert W. Langhans. On-line Fault Detection and Diagnosis for Greenhouse Environmental Control. United States Department of Agriculture, luty 2001. http://dx.doi.org/10.32747/2001.7575271.bard.
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Background Early detection and identification of faulty greenhouse operation is essential, if losses are to be minimized by taking immediate corrective actions. Automatic detection and identification would also free the greenhouse manager to tend to his other business. Original objectives The general objective was to develop a method, or methods, for the detection, identification and accommodation of faults in the greenhouse. More specific objectives were as follows: 1. Develop accurate systems models, which will enable the detection of small deviations from normal behavior (of sensors, control, structure and crop). 2. Using these models, develop algorithms for an early detection of deviations from the normal. 3. Develop identifying procedures for the most important faults. 4. Develop accommodation procedures while awaiting a repair. The Technion team focused on the shoot environment and the Cornell University team focused on the root environment. Achievements Models: Accurate models were developed for both shoot and root environment in the greenhouse, utilizing neural networks, sometimes combined with robust physical models (hybrid models). Suitable adaptation methods were also successfully developed. The accuracy was sufficient to allow detection of frequently occurring sensor and equipment faults from common measurements. A large data base, covering a wide range of weather conditions, is required for best results. This data base can be created from in-situ routine measurements. Detection and isolation: A robust detection and isolation (formerly referred to as 'identification') method has been developed, which is capable of separating the effect of faults from model inaccuracies and disturbance effects. Sensor and equipment faults: Good detection capabilities have been demonstrated for sensor and equipment failures in both the shoot and root environment. Water stress detection: An excitation method of the shoot environment has been developed, which successfully detected water stress, as soon as the transpiration rate dropped from its normal level. Due to unavailability of suitable monitoring equipment for the root environment, crop faults could not be detected from measurements in the root zone. Dust: The effect of screen clogging by dust has been quantified. Implications Sensor and equipment fault detection and isolation is at a stage where it could be introduced into well equipped and maintained commercial greenhouses on a trial basis. Detection of crop problems requires further work. Dr. Peleg was primarily responsible for developing and implementing the innovative data analysis tools. The cooperation was particularly enhanced by Dr. Peleg's three summer sabbaticals at the ARS, Northem Plains Agricultural Research Laboratory, in Sidney, Montana. Switching from multi-band to hyperspectral remote sensing technology during the last 2 years of the project was advantageous by expanding the scope of detected plant growth attributes e.g. Yield, Leaf Nitrate, Biomass and Sugar Content of sugar beets. However, it disrupted the continuity of the project which was originally planned on a 2 year crop rotation cycle of sugar beets and multiple crops (com and wheat), as commonly planted in eastern Montana. Consequently, at the end of the second year we submitted a continuation BARD proposal which was turned down for funding. This severely hampered our ability to validate our findings as originally planned in a 4-year crop rotation cycle. Thankfully, BARD consented to our request for a one year extension of the project without additional funding. This enabled us to develop most of the methodology for implementing and running the hyperspectral remote sensing system and develop the new analytical tools for solving the non-repeatability problem and analyzing the huge hyperspectral image cube datasets. However, without validation of these tools over a ful14-year crop rotation cycle this project shall remain essentially unfinished. Should the findings of this report prompt the BARD management to encourage us to resubmit our continuation research proposal, we shall be happy to do so.
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Perkins, Dustin. Invasive exotic plant monitoring in Capitol Reef National Park: 2020 and 2021 field seasons. National Park Service, sierpień 2022. http://dx.doi.org/10.36967/2294094.
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Invasive exotic plant (IEP) species are a significant threat to natural ecosystem integrity and biodiversity. Controlling them is a high priority for the National Park Service. The Northern Colorado Plateau Network (NCPN) selected the early detection of IEPs as one of 11 moni-toring protocols to be implemented as part of its long-term monitoring program. From June 5 to July 29, 2020, and May 30 to June 2, 2021, network staff conducted surveys for priority IEP species along the Oak Creek, Pleasant Creek, and State Route 24 monitoring routes at Capitol Reef National Park. We detected 834 patches of 11 priority IEP species along 67.9 kilometers (42.2 miles) of three monitoring routes. There were more patches of tamarisk along State Route 24, and a higher percentage of large patches, than in previous years. This indicates that previously identified IEP patches have expanded and grown. Field bindweed (Convolvulus arvensis) and Russian olive (Elaeagnus angustifolia) along State Route 24 have both increased in prevalence since monitoring began. Tamarisk (Tamarix sp.) was the most prevalent prior-ity IEP species on all three routes. On Oak and Pleasant creeks, there were fewer than three patches of all other IEPs. On State Route 24, there were 30 or more patches of Russian olive, quackgrass (Elymus repens), field bindweed, and blue mustard (Chorispora tenella). IEP prior-ity species were found on 71%, 47%, and 62% of transects along Oak Creek, Pleasant Creek, and State Route 24, respectively. Yellow sweet-clover (Melilotus officinalis) was the most fre-quently observed IEP on Oak Creek and Pleasant Creek. Percent cover was highest for yellow sweet-clover, Russian thistle (Salsola sp.), and tamarisk on Oak Creek, Pleasant Creek, and State Route 24, respectively. The NCPN plans to return to Capitol Reef in 2023 to continue the fourth rotation of invasive plant monitoring.
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Weissinger, Rebecca. Trends in water quality at Bryce Canyon National Park, water years 2006–2021. Redaktor Alice Wondrak Biel. National Park Service, listopad 2022. http://dx.doi.org/10.36967/2294946.
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The National Park Service collects water-quality samples on a rotating basis at three fixed water-quality stations in Bryce Canyon National Park (NP): Sheep Creek, Yellow Creek, and Mossy Cave Spring. Data collection began at Sheep Creek and Yellow Creek in November 2005 and at Mossy Cave in July 2008. Data on in-situ parameters, fecal-coliform samples, major ions, and nutrients are collected monthly, while trace elements are sampled quarterly. This report analyzes data from the beginning of the period of record for each station through water year 2021 to test for trends over time. Concentrations are also compared to relevant water-quality standards for the State of Utah. Overall, water quality at the park’s monitoring stations continues to be excellent, and park managers have been successful in their goal of maintaining these systems in unimpaired condition. Infrequent but continued Escherichia coli exceedances from trespass livestock at Sheep and Yellow creeks support the need for regular fence maintenance along the park boundary. High-quality conditions may qualify all three sites as Category 1 waters, the highest level of anti-degradation protection provided by the State of Utah. Minimum and maximum air temperatures at the park have increased, while precipitation remains highly variable. Increasing air temperatures have led to increasing water temperatures in Sheep and Yellow creeks. Sheep Creek also had a decrease in flow across several quantiles from 2006 to 2021, while higher flows decreased at Yellow Creek in the same period. Surface flows in these two creeks are likely to be increasingly affected by higher evapotranspiration due to warming air temperatures and possibly decreasing snowmelt runoff as the climate changes. The influx of ancient groundwater in both creek drainages helps sustain base flows at the sites. Mossy Cave Spring, which is sampled close to the spring emergence point, showed less of a climate signal than Sheep and Yellow creeks. In our record, the spring shows a modest increase in discharge, including higher flows at higher air temperatures. An uptick in visitation to Water Canyon and the Mossy Cave Trail has so far not been reflected by changes in water quality. There are additional statistical trends in water-quality parameters at all three sites. However, most of these trends are quite small and are likely ecologically negligible. Some statistical trends may be the result of instrument changes and improvements in quality assurance and quality control over time in both the field sampling effort and the laboratory analyses. Long-term monitoring of water-quality stations at Bryce Canyon NP suggests relatively stable aquatic systems that benefit from protection within the park. To maintain these unimpaired conditions into the future, park managers could consider: Regular fence checks and maintenance along active grazing allotments at the park boundary to protect riparian areas and aquatic systems from trespass livestock. Developing a springs-monitoring program to track changes in springflow at spring emergences to better understand bedrock-aquifer water supplies. These data would also help quantify springflow for use in water-rights hearings. Supporting hydrogeologic investigations to map the extent and flow paths of groundwater aquifers. Working with the State of Utah to develop groundwater-protection zones to protect groundwater aquifers from developments that would affect springs in the park. Prioritizing watershed management with proactive fire risk-reduction practices. Explicitly including watershed protection as a goal in plans for fire management and suppression. Using additional data and analyses to better understand the drivers of trends in water quality and their ecological significance. These could include higher-frequency data to better understand relationships between groundwater, precipitation, and surface flows at the sites. These could also include watershed metrics...
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MOMENT-ROTATION MODEL OF EXTERNAL COVER PLATE JOINTS BETWEEN STEEL BEAMS AND CONCRETE-FILLED SQUARE STEEL TUBULAR COLUMNS WITH INNER I-SHAPED CFRP PROFILE. The Hong Kong Institute of Steel Construction, czerwiec 2023. http://dx.doi.org/10.18057/ijasc.2023.19.2.5.
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As a new type of beam-column joint, external cover plate joints can be used in concrete-filled square steel tubular (CFSST) structures. To accurately analyze the mechanical characteristics of this novel joint during structural design, it is necessary to investigate the moment-rotation relationships. Based on the analysis of the force-transferring mechanism, the formulas to decide the initial rotation stiffness and ultimate bending moment are founded by using the component analysis method, while the finite element analysis results are also utilized to verify these formulas. Considering the advantages and disadvantages of the existing typical moment-rotation models, a new representation for calculating the moment-rotation curve of the external cover plate joints is proposed using the ultimate bending moment and initial rotation stiffness as two basic parameters. The research reveals that the moment-rotation model proposed in this paper is able to take all loading stages of this joint into account, which facilitates the analysis of yield and ultimate loads. In addition, this model is smooth and continuous at the piecewise points to avoid numerical problems that may be caused in the calculation. Comparing the moment-rotation curves obtained by the calculation model and finite element simulation, the results show good consistency, demonstrating that the moment-rotation model presented in this paper is applicable to the analysis and design of the external cover plate joints.
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COMPLETE SET ROTATION-LIFTING CONSTRUCTION TECHNOLOGY FOR FREE-FORM SURFACE ROOF STRUCTURES WITH LARGE ELEVATION DIFFERENCE. The Hong Kong Institute of Steel Construction, sierpień 2022. http://dx.doi.org/10.18057/icass2020.p.618.
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A complete set rotation-lifting construction technology for free-form surface roof structures with large elevation difference is in this paper. Six principles for this construction technology are proposed. Based on optimization theory, a digital analysis method is developed for calculating the exact solution of lying posture and rotation axis. Theoretical algorithm of multi-lifting point synchronous lifting control technology with different lifting speed and the same lifting ratio is proposed, and a control program is developed. Structural configuration of key construction stage is inspected and monitored by applying the digital system. The system compares computational analysis results with the real-time structure configuration, and the result is provided for construction control. The construction technology has been successfully applied in the Hangzhou West Railway Station project, which has good economic and social benefits.
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Coastal Lidar And Radar Imaging System (CLARIS) mobile terrestrial lidar survey along the Outer Banks, North Carolina in Currituck and Dare counties. Coastal and Hydraulics Laboratory (U.S.), styczeń 2020. http://dx.doi.org/10.21079/11681/39419.
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The Coastal Observation and Analysis Branch (COAB) located at the Field Research Facility (FRF) conducts quarterly surveys and post-storm surveys along up to 60 kilometers of coastline within the vicinity of the FRF to assess, evaluate, and provide updated observations of the morphology of the foreshore and dune system. The surveys are conducted using a mobile terrestrial LiDAR scanner coupled with an Inertial Navigation System (INS). Traditionally the surveys coincide with a low tide, exposing the widest swath of visible sediment to the scanner as well as enough wind-sea swell or texture to induce wave breaking upon the interior sandbars. The wave field is measured with X-Band radar which records a spatial time series of wave direction and speed. Data for the survey region was collected using the VZ-2000's mobile, 3D scanning mode where the scanner continuously rotates the line scan 360 degrees as the vehicle progresses forward. Elevation measurements are acquired on all sides of the vehicle except for the topography directly underneath the vehicle. As the vehicle moves forward, the next rotation will capture the previous position's occluded data area. Laser data is acquired in mobile 3D radar mode with a pulse repetition rate of 300kHz, theta resolution of 0.19 degrees and phi resolution of 0.625 degrees. Horizontal Datum NAD83(2011), Projection North Carolina State Plane (3200) meters; Vertical Datum NAVD88, meters with geoid09 applied.
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Coastal Lidar And Radar Imaging System (CLARIS) mobile terrestrial lidar survey along the Outer Banks, North Carolina in Currituck and Dare counties. Coastal and Hydraulics Laboratory (U.S.), styczeń 2020. http://dx.doi.org/10.21079/11681/39419.
Pełny tekst źródłaStreszczenie:
The Coastal Observation and Analysis Branch (COAB) located at the Field Research Facility (FRF) conducts quarterly surveys and post-storm surveys along up to 60 kilometers of coastline within the vicinity of the FRF to assess, evaluate, and provide updated observations of the morphology of the foreshore and dune system. The surveys are conducted using a mobile terrestrial LiDAR scanner coupled with an Inertial Navigation System (INS). Traditionally the surveys coincide with a low tide, exposing the widest swath of visible sediment to the scanner as well as enough wind-sea swell or texture to induce wave breaking upon the interior sandbars. The wave field is measured with X-Band radar which records a spatial time series of wave direction and speed. Data for the survey region was collected using the VZ-2000's mobile, 3D scanning mode where the scanner continuously rotates the line scan 360 degrees as the vehicle progresses forward. Elevation measurements are acquired on all sides of the vehicle except for the topography directly underneath the vehicle. As the vehicle moves forward, the next rotation will capture the previous position's occluded data area. Laser data is acquired in mobile 3D radar mode with a pulse repetition rate of 300kHz, theta resolution of 0.19 degrees and phi resolution of 0.625 degrees. Horizontal Datum NAD83(2011), Projection North Carolina State Plane (3200) meters; Vertical Datum NAVD88, meters with geoid09 applied.
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Tire Experimental Characterization Using Contactless Measurement Methods. SAE International, sierpień 2021. http://dx.doi.org/10.4271/2021-01-1114.
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In the frame of automotive Noise Vibration and Harshness (NVH) evaluation, inner cabin noise is among the most important indicators. The main noise contributors can be identified in engine, suspensions, tires, powertrain, brake system, etc. With the advent of E-vehicles and the consequent absence of the Internal Combustion Engine (ICE), tire/road noise has gained more importance, particularly at mid-speed driving and in the spectrum up to 300 Hz. At the state of the art, the identification and characterization of Noise and Vibration sources rely on pointwise sensors (microphones, accelerometers, strain gauges). Optical methods such as Digital Image Correlation (DIC) and Laser Doppler Vibrometer (LDV) have recently received special attention in the NVH field because they can be used to obtain full-field measurements. Moreover, these same techniques could also allow to characterize the tire behavior in operating conditions, which would be practically impossible to derive with standard techniques. In this paper we will demonstrate how non-contact full-field measurement techniques can be used to reliably and robustly characterize the tire behavior up to 300 Hz, focusing on static conditions. Experimental modal analysis will extract the modal characteristic of the tire in both free-free and statically preloaded boundary conditions, using both DIC and LDV. The extracted natural frequencies, damping ratios and full-field mode shapes will be used on one side to improve the accuracy of tire models (either by deriving FRF based models or updating FE ones) but also as a reference for future investigation on the tire behavior characterization in rotating conditions.