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Journal articles on the topic 'Operational mode shape'
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PARLOO, E., P. VERBOVEN>, P. GUILLAUME, and M. VAN OVERMEIRE. "SENSITIVITY-BASED OPERATIONAL MODE SHAPE NORMALISATION." Mechanical Systems and Signal Processing 16, no. 5 (September 2002): 757–67. http://dx.doi.org/10.1006/mssp.2002.1498.
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De Sitter, Gert, Patrick Guillaume, Steve Vanlanduit, and Christof Devriendt. "Operational Acoustic Modal Analysis: Sensitivity-Based Mode Shape Normalisation." Acta Acustica united with Acustica 94, no. 4 (July 1, 2008): 580–87. http://dx.doi.org/10.3813/aaa.918067.
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Parloo, E., B. Cauberghe, F. Benedettini, R. Alaggio, and P. Guillaume. "Sensitivity-based operational mode shape normalisation: Application to a bridge." Mechanical Systems and Signal Processing 19, no. 1 (January 2005): 43–55. http://dx.doi.org/10.1016/j.ymssp.2004.03.009.
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Brincker, Rune. "Some Elements of Operational Modal Analysis." Shock and Vibration 2014 (2014): 1–11. http://dx.doi.org/10.1155/2014/325839.
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This paper gives an overview of the main components of operational modal analysis (OMA) and can serve as a tutorial for research oriented OMA applications. The paper gives a short introduction to the modeling of random responses and to the transforms often used in OMA such as the Fourier series, the Fourier integral, the Laplace transform, and the Z-transform. Then the paper introduces the spectral density matrix of the random responses and presents the theoretical solutions for correlation function and spectral density matrix under white noise loading. Some important guidelines for testing are mentioned and the most common techniques for signal processing of the operating signals are presented. The algorithms of some of the commonly used time domain and frequency domain identification techniques are presented and finally some issues are discussed such as mode shape scaling, and mode shape expansion. The different techniques are illustrated on the difficult case of identifying the three first closely spaced modes of the Heritage Court Tower building.
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Rahul, R., Rohit Rajpal, Sai Aditya Raman Kuchibhatla, and K. V. Gangadharan. "Sensor Fusion for Operational Mode Shape Analysis of Multi DoF Systems." Materials Today: Proceedings 5, no. 11 (2018): 24871–79. http://dx.doi.org/10.1016/j.matpr.2018.10.286.
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Quintanar-Guzmán, Serket, Somasundar Kannan, Adriana Aguilera-González, Miguel A. Olivares-Mendez, and Holger Voos. "Operational space control of a lightweight robotic arm actuated by shape memory alloy wires: A comparative study." Journal of Intelligent Material Systems and Structures 30, no. 9 (August 25, 2017): 1368–84. http://dx.doi.org/10.1177/1045389x17721050.
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This article presents the design and control of a two-link lightweight robotic arm using shape memory alloy wires as actuators. Both a single-wire actuated system and an antagonistic configuration system are tested in open and closed loops. The mathematical model of the shape memory alloy wire, as well as the kinematics and dynamics of the robotic arm, are presented. The operational space control of the robotic arm is performed using a joint space control in the inner loop and closed-loop inverse kinematics in the outer loop. In order to choose the best joint space control approach, a comparative study of four different control approaches (proportional derivative, sliding mode, adaptive, and adaptive sliding mode control) is carried out for the proposed model. From this comparative analysis, the adaptive controller was chosen to perform operational space control. This control helps us to perform accurate positioning of the end-effector of shape memory alloy wire–based robotic arm. The complete operational space control was successfully tested through simulation studies performing position reference tracking in the end-effector space. Through simulation studies, the proposed control solution is successfully verified to control the hysteretic robotic arm.
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Rovšček, Domen, Janko Slavič, and Miha Boltežar. "Operational mode-shape normalisation with a structural modification for small and light structures." Mechanical Systems and Signal Processing 42, no. 1-2 (January 2014): 1–13. http://dx.doi.org/10.1016/j.ymssp.2013.08.019.
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Tao, C., Y. Daren, and B. Wen. "Distributed parameter control arithmetic for an axisymmetrical dual-mode scramjet." Aeronautical Journal 112, no. 1135 (September 2008): 557–65. http://dx.doi.org/10.1017/s0001924000002517.
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AbstractDual-mode scramjet is one of the candidates for hypersonic flight propulsion system which will be used in wide range of flight Mach numbers from 4 to 12 or higher, wherein dual-mode scramjet should be well designed to be suitable for subsonic/supersonic combustion operation according to the flight conditions. Therefore this system is required to operate in a finite number of operational modes that necessitate robust, stable, and smooth transitions between them by which selective operability of supersonic/subsonic combustion modes and efficient combustor operation in these modes may be realised. A key issue in making mode transition efficient and stable is mode transition control. The major problem in mode transition control is the handling of the various flow and combustion coupling effects of dual-mode scramjet whose physical states are spatially coupled and whose governing equations are partial differential equations. Involving these distributed parameter issues, our basic idea is using the shape control theory to study the control problems of mode transition for dual-mode scramjet with the aim of achieving the desirable design properties and increasing control reliabilities. This specific approach is motivated by the promise of novel techniques in control theory developed in recent years. Concrete control arithmetic of this approach, such as shape control model, sensitivity analysis and gradient-based optimisation procedure, are given in this paper. Simulation results for an axisymmetric, wall-injection dual-mode scramjet show the feasibility and validity of the method.
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Tozkoparan, Ã.-mer Anıl, Osman Taha Sen, and Rajendra Singh. "Case study: Identification of brake squeal source mechanism through experimental and computational approaches." Noise Control Engineering Journal 68, no. 1 (January 20, 2020): 21–37. http://dx.doi.org/10.3397/1/37682.
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In this case study, mechanism leading to squeal noise in an automotive disc brake system is investigated with focus on systematic laboratory experiments and associated computational models. First, experimental modal analyses are conducted on the brake corner assembly components, and the natural frequencies and corresponding mode shapes are obtained. Second, finite element models of same components are developed, updated and validated by comparing predicted modal characteristics with those measured. Third, a controlled laboratory experiment is designed, constructed and operated in a semi-anechoic room. Experiments are conducted at many operational disc speeds and brake line pressures, and acceleration on the caliper and sound pressure are measured. Squeal events at distinct frequencies are successfully identified in the experiments. Fourth, a comprehensive computational model of the brake corner assembly is constructed using validated component models, and squeal investigation is then conducted through complex eigenvalue analyses while mimicking the operational conditions of experiments. The system model yields unstable frequencies at several operational conditions. It is observed that experimentally detected squeal frequencies match well with predicted unstable frequencies. Finally, operational deflection shape measurements on the caliper are also carried out during squeal events, and the predictions are found to be similar to those measured. In conclusion, the squeal generation mechanism of the brake system is understood from the perspective of frictioninduced modal coupling, and an experimentally validated computational model of the brake system is successfully developed that may be used to find solutions to mitigate squeal.
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Mironov, Aleksey, Pavel Doronkin, Aleksander Priklonsky, and Igor Kabashkin. "Condition Monitoring Of Operating Pipelines With Operational Modal Analysis Application." Transport and Telecommunication Journal 16, no. 4 (December 1, 2015): 305–19. http://dx.doi.org/10.1515/ttj-2015-0028.
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Abstract In the petroleum, natural gas and petrochemical industries, great attention is being paid to safety, reliability and maintainability of equipment. There are a number of technologies to monitor, control, and maintain gas, oil, water, and sewer pipelines. The paper focuses on operational modal analysis (OMA) application for condition monitoring of operating pipelines. Special focus is on the topicality of OMA for definition of the dynamic features of the pipeline (frequencies and mode shapes) in operation. The research was conducted using two operating laboratory models imitated a part of the operating pipeline. The results of finite-element modeling, identification of pipe natural modes and its modification under the influence of virtual failure are discussed. The work considers the results of experimental research of dynamic behavior of the operating pipe models using one of OMA techniques and comparing dynamic properties with the modeled data. The study results demonstrate sensitivity of modal shape parameters to modification of operating pipeline technical state. Two strategies of pipeline repair – with continuously condition-based monitoring with proposed technology and without such monitoring, was discussed. Markov chain reliability models for each strategy were analyzed and reliability improvement factor for proposed technology of monitoring in compare with traditional one was evaluated. It is resumed about ability of operating pipeline condition monitoring by measuring dynamic deformations of the operating pipe and OMA techniques application for dynamic properties extraction.
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Tributsch, Alexander, and Christoph Adam. "A Multi-Step Approach for Identification of Structural Modifications Based on Operational Modal Analysis." International Journal of Structural Stability and Dynamics 14, no. 05 (June 2014): 1440004. http://dx.doi.org/10.1142/s0219455414400045.
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In this paper, an approach for detecting damage and structural modifications is implemented, based on a combination of several indicators derived from the recorded ambient dynamic structural response. In a multi-step procedure, the normalized cumulative power spectral density (NCPSD) evaluated at several structural nodes and a thereof derived "NCPSD damage index" is proposed to detect a modification of the structure. A subsequent sophisticated superposition of a series of mode shape quantities yields a "mode shape damage index" as a function of the structural coordinates that reveals the specific location of this structural modification. Furthermore, it is discussed how environmental effects from varying temperatures on natural frequencies can be substantially reduced. Therefore, long-term monitoring of the structure is required to define relations that allow translating the proposed damage parameters contaminated by temperature effects into the domain of the structure in a reference state. The efficiency of the proposed method is tested on an old iron railway bridge, subjected to a series of structural modifications, such as stepwise reducing the stiffness of local elements, adding mass and an additional flexible support. From the results of this comprehensive study it can be concluded that this nondestructive approach is a promising tool for reliable structural health monitoring (SHM).
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Herrmann, Guido, Jamaludin Jalani, Muhammad Nasiruddin Mahyuddin, Said G. Khan, and Chris Melhuish. "Robotic hand posture and compliant grasping control using operational space and integral sliding mode control." Robotica 34, no. 10 (December 23, 2014): 2163–85. http://dx.doi.org/10.1017/s0263574714002811.
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SUMMARYThis paper establishes a novel approach of robotic hand posture and grasping control. For this purpose, the control uses the operational space approach. This permits the consideration of the shape of the object to be grasped. Thus, the control is split into a task control and a particular optimizing posture control. The task controller employs Cylindrical and Spherical coordinate systems due to their simplicity and geometric suitability. This is achieved by using an integral sliding mode controller (ISMC) as task controller. The ISMC allows us to introduce a model reference approach where a virtual mass-spring-damper system can be used to design a compliant trajectory tracking controller. The optimizing posture controller together with the task controller creates a simple approach to obtain pre-grasping/object approach hand postures. The experimental results show that target trajectories can be easily followed by the task control despite the presence of friction and stiction. When the object is grasped, the compliant control will automatically adjust to a specific compliance level due to an augmented compliance parameter adjustment algorithm. Once a specific compliance model has been achieved, the fixed compliance controller can be tested for a specific object grasp scenario. The experimental results prove that the Bristol Elumotion robot hand (BERUL) can automatically and successfully attain different compliance levels for a particular object via the ISMC.
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Khoroshilov, V. S., and A. E. Zakrzhevskii. "Dynamics of spacecraft with gyro-gravitational system of stabilization due to elastic ring antenna deployment." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 225, no. 10 (September 30, 2011): 2333–46. http://dx.doi.org/10.1177/0954406211410010.
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This article deals with the study of the dynamics of the spacecraft with the gyro-gravitational system of stabilization. The deployment of a flexible ring antenna is performed after placing the spacecraft into orbit and completion of the preliminary damping by a special jet-propelled system, and after uncaging the gyros. Primarily, the antenna is a pre-stressed tape wound on a special drum. When the drum starts deploying the tape, it takes the shape of an elastic ring of variable diameter. The objective of the study is the mechanical and computational modelling of the spacecraft dynamics. The equations of motion are derived with the use of the Eulerian–Lagrangian formalizm. Numerical simulations of the operational mode of the system are conducted. Numerical results indicate that the system used for attitude stabilization ensures the shape of the deployed design and prescribed accuracy of the orientation. Simulation results are presented for the spacecraft model to show the effectiveness of the spacecraft and deployment process stabilization.
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Tarpø, Marius, Bruna Nabuco, Christos Georgakis, and Rune Brincker. "Expansion of experimental mode shape from operational modal analysis and virtual sensing for fatigue analysis using the modal expansion method." International Journal of Fatigue 130 (January 2020): 105280. http://dx.doi.org/10.1016/j.ijfatigue.2019.105280.
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Griffin, Sarah M., Jason A. Otkin, Christopher M. Rozoff, Justin M. Sieglaff, Lee M. Cronce, and Curtis R. Alexander. "Methods for Comparing Simulated and Observed Satellite Infrared Brightness Temperatures and What Do They Tell Us?" Weather and Forecasting 32, no. 1 (December 19, 2016): 5–25. http://dx.doi.org/10.1175/waf-d-16-0098.1.
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Abstract In this study, the utility of dimensioned, neighborhood-based, and object-based forecast verification metrics for cloud verification is assessed using output from the experimental High Resolution Rapid Refresh (HRRRx) model over a 1-day period containing different modes of convection. This is accomplished by comparing observed and simulated Geostationary Operational Environmental Satellite (GOES) 10.7-μm brightness temperatures (BTs). Traditional dimensioned metrics such as mean absolute error (MAE) and mean bias error (MBE) were used to assess the overall model accuracy. The MBE showed that the HRRRx BTs for forecast hours 0 and 1 are too warm compared with the observations, indicating a lack of cloud cover, but rapidly become too cold in subsequent hours because of the generation of excessive upper-level cloudiness. Neighborhood and object-based statistics were used to investigate the source of the HRRRx cloud cover errors. The neighborhood statistic fractions skill score (FSS) showed that displacement errors between cloud objects identified in the HRRRx and GOES BTs increased with time. Combined with the MBE, the FSS distinguished when changes in MAE were due to differences in the HRRRx BT bias or displacement in cloud features. The Method for Object-Based Diagnostic Evaluation (MODE) analyzed the similarity between HRRRx and GOES cloud features in shape and location. The similarity was summarized using the newly defined MODE composite score (MCS), an area-weighted calculation using the cloud feature match value from MODE. Combined with the FSS, the MCS indicated if HRRRx forecast error is the result of cloud shape, since the MCS is moderately large when forecast and observation objects are similar in size.
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Tatsis, Konstantinos, Vasilis Dertimanis, Yaowen Ou, and Eleni Chatzi. "GP-ARX-Based Structural Damage Detection and Localization under Varying Environmental Conditions." Journal of Sensor and Actuator Networks 9, no. 3 (September 8, 2020): 41. http://dx.doi.org/10.3390/jsan9030041.
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The representation of structural dynamics in the absence of physics-based models, is often accomplished through the identification of parametric models, such as the autoregressive with exogenous inputs, e.g. ARX models. When the structure is amenable to environmental variations, parameter-varying extensions of the original ARX model can be implemented, allowing for tracking of the operational variability. Yet, the latter occurs in sufficiently longer time-scales (days, weeks, months), as compared to system dynamics. For inferring a “global”, long time-scale varying ARX model, data from a full operational cycle has to typically become available. In addition, when the sensor network comprises multiple nodes, the identification of long time-scale varying, vector ARX models grow in complexity. We address these issues by proposing a distributed framework for structural identification, damage detection and localization. Its main features are: (i) the individual estimation of local, single-input-single-output ARX models at every operational point; (ii) the long time-scale representation of each individual ARX coefficient via a Gaussian process regression, which captures dependency on varying Environmental and Operational Conditions (EOCs); (iii) the establishment of a distributed residual generation algorithm for damage detection, which produces time-series of well-defined stationary statistics, with detected discrepancies used for damage diagnosis; and, (iv) exploitation of ARX-inferred mode shape curvatures, obtained via ARX-inferred global state-space models, of the healthy and damaged states, for damage localization. The method is assessed via application on two numerical case studies of different complexity, with the results confirming its efficacy for diagnostics under varying EOCs.
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Chen, Shiyi, Mohammed Shokr, Xinqing Li, Yufang Ye, Zhilun Zhang, Fengming Hui, and Xiao Cheng. "MYI Floes Identification Based on the Texture and Shape Feature from Dual-Polarized Sentinel-1 Imagery." Remote Sensing 12, no. 19 (October 3, 2020): 3221. http://dx.doi.org/10.3390/rs12193221.
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The Northwest Passage (NWP) in the Arctic is usually covered with hazardous multi-year ice (MYI) and seasonal first-year ice (FYI) in winter, with possible thin ice and open-water areas during transition seasons. Ice classification is important for both marine navigation and climate change studies. Satellite-based Synthetic Aperture Radar (SAR) systems have shown advantages of retrieving this information. Operational ice mapping relies on visual analysis of SAR images along with ancillary data. However, these maps estimate ice types and concentrations within large-size polygons of a few tens or hundreds of kilometers, which are subjectively identified and selected by analysts. This study aims at developing an automated algorithm to identify individual MYI floes from SAR images then classify the rest of the image as FYI and other ice types. The algorithm identifies the MYI floes using extended-maximum operator, morphological image processing, and a few geometrical features. Classifying the rest of the image uses texture and neural network model. The input data is a set of Sentinel-1 A/B Extended Wide (EW) mode images, acquired between September and March 2016–2019. Although the overall accuracy (for all type classification) from the new method scored 93.26%, the accuracy from using the texture classifier only was 75.81%. The kappa coefficient from the former was higher than the latter by 0.25. Compared with the operational ice charts from the Canadian Ice Service, ice type maps from the new method show better distribution of MYI at the fine scale of individual floes. Comparison against MYI concentration from two automated algorithms that use a combination of coarse-resolution passive and active microwave data also confirms the advantage of resolving MYI floes from the fine-resolution SAR.
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Hu, Wei-Hua, Zeng-Mao Xu, Ming-Yue Liu, De-Hui Tang, Wei Lu, Zuo-Hua Li, Jun Teng, Xiao-Hui Han, Samir Said, and Rolf G. Rohrmann. "Estimation of the Lateral Dynamic Displacement of High-Rise Buildings under Wind Load Based on Fusion of a Remote Sensing Vibrometer and an Inclinometer." Remote Sensing 12, no. 7 (April 1, 2020): 1120. http://dx.doi.org/10.3390/rs12071120.
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This paper proposes a novel method to estimate the lateral displacement of high-rise structures under wind loads. The coefficient β(x) is firstly derived, reflecting the relation between the structural lateral dynamic displacement and the inclination angle at the height x of a structure. If the angle is small, it is the ratio between the structural fundamental mode shape and its first-order derivative without influence of external loads. Several dynamic experiments of structures are performed based on a laser remote sensing vibrometer and an inclinometer, which shows that the fundamental mode is dominated in the structural displacement response under different types of excitations. Once the coefficient β(x) is curve-fitted by measuring both the structural lateral dynamic displacement and the inclination angle synchronously, the real-time structural lateral displacement under operational conditions is estimated by multiplying the coefficient β(x) with the inclination angle. The advantage of the proposed method is that the coefficient β(x) can be identified by lateral dynamic displacement measured in high resolution by the remote sensing vibrometer, which is useful to reconstruct the displacement accurately by the inclination angle under operational conditions.
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Castro, J. Cruz, E. Hernández Palafox, I. A. Alarcón Sánchez, Luis H. Hernández-Gómez, Pablo Ruiz-López, and A. Armenta Molina. "Analysis of the Leakage-Flow-Induced Vibration of a Slip Joint in a Jet Pump of a Boiling Water Reactor." Defect and Diffusion Forum 390 (January 2019): 23–31. http://dx.doi.org/10.4028/www.scientific.net/ddf.390.23.
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The purpose of this analysis is to evaluate the structural integrity of the jet pump assembly of a BWR during the performance of its operational and safety functions. The natural frequencies and vibration modes of the jet pump assembly immersed in water were determined. It was observed that the fourth mode shape was torsional, and its associated resonance frequency was 41.82 Hz. Also, the vibration induced by the flow in the leakage of the slip joint was analyzed with an axisymmetric model. The gap of the slip joint was varied from 0.2 mm until 0.65bmm. A gap between 0.6 and 0.64, would cause flow-induced vibration because this excitation frequency matches with the fourth natural frequency of the jet pump assembly. The above was carried out using computational fluid dynamics, as well as the finite element method, with ANSYS Structural and ANSYS Fluent codes.
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Molina-Viedma, Ángel J., Elías López-Alba, Luis Felipe-Sesé, and Francisco A. Díaz. "Operational Deflection Shape Extraction from Broadband Events of an Aircraft Component Using 3D-DIC in Magnified Images." Shock and Vibration 2019 (April 9, 2019): 1–9. http://dx.doi.org/10.1155/2019/4039862.
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Recently, many works have shown the capabilities of noninterferometric optical techniques, such as digital image correlation, to characterise modal behaviour. They provide a global insight into the structure or component behaviour which implies massive spatial information, unaffordable by traditional sensor instrumentation. Moreover, phase-based motion magnification (PMM) is a methodology which, based on a sequence of images, magnifies a periodic motion encoded in phase time-domain signals of the complex steerable pyramid filters employed to decompose the images. It provides a powerful tool to interpret deformation. However, the interpretation is just qualitative and should be avoided if out-plane motion is recorded as only one camera is employed. To overcome this issue, 3D digital image correlation (3D-DIC) has been linked with PMM to provide measurements from stereoscopic sets of images, providing full-field displacement maps to magnified images. In this work, the combination of PMM and 3D-DIC has been employed to evaluate the modal behaviour of an aircraft cabin under random excitation. The study was focused on the passenger window area due to its significance to the structural integrity as a discontinuity of the peel. Operational deflection shapes at different resonances were characterised by magnifying a single resonance in the spectrum and then measuring with 3D-DIC. These measurements were validated with those obtained in forced normal mode tests. Motion and displacement videos improved the understanding of the identified resonance deformation. Actually, a relevant behaviour was noticed in the window’s frame, a quite narrow area where using traditional sensors would not provide such a detailed 3D information.
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Galdia, Marcus. "The Comparative Element in Comparative Legal Linguistics." Comparative Legilinguistics 43, no. 1 (September 1, 2020): 57–76. http://dx.doi.org/10.2478/cl-2020-0008.
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Abstract Fundamental legal-linguistic research includes next to monolingual approaches to the legal language also comparative approaches. Meanwhile, the epistemic value of comparative approaches is unclear in legal linguistics. Therefore, in this article different legal-linguistic comparative approaches will be scrutinized, and their perspectives made operational in legal linguistics. Especially, the traditional analysis of legal terminology gains momentum here in the context of discursive comparative approaches. The multilingual origins and the intertextual mode of existence and development of the legal language are identified as its characteristic features. They also shape processes in which the language of the global law emerges in the contemporary social reality.
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Drygala, Izabela Joanna, and Joanna Maria Dulinska. "Full-Scale Experimental and Numerical Investigations on the Modal Parameters of a Single-Span Steel-Frame Footbridge." Symmetry 11, no. 3 (March 19, 2019): 404. http://dx.doi.org/10.3390/sym11030404.
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In this work, an examination on the modal properties of a single-span steel-frame footbridge is presented. The footbridge is situated in Jawornik (Lesser Poland). The footbridge is symmetrical since its main structure consists of two steel frames of the same shape. The boundary conditions for both frames are the same as well. The study was completed on the basis of numerical as well as experimental investigations. For finite element (FE) analysis, a 3-D model of the single-span steel-frame footbridge was created. For the experimental study, a research scheme for in situ tests was developed. Three kinds of excitation techniques were used during the in situ tests: shock excitation, operational vibration, and slow sine sweep testing. Different functions that estimate natural frequencies, i.e., the power spectral density function (PSD) and the frequency response function (FRF), were applied. The modal assurance criterion (MAC) was used as a mathematical tool for the verification of the mode shapes of natural vibrations obtained in experimental and numerical ways. Good compatibility was recognized between the results obtained for experimental and numerical procedures in terms of both the natural frequency and the mode of vibration. The identified and verified values of the five consecutive natural frequencies of the footbridge were smaller than 5 Hz, but they were recognized as being located outside the frequency range defined as having “maximum risk of resonance". The numerical and experimental modal analysis revealed that all modes corresponding to the natural frequencies from the 0–5 Hz range have both a symmetrical and an anti-symmetrical nature. In particular, the first vertical mode, which can play a central role from the serviceability of the footbridge point of view has a symmetrical shape. The results of the research might be applicable to the dynamic study of the structure type considered in the analysis, i.e., for the dynamic assessment of a single-span steel-frame footbridge with a relatively large mass as well as stiffness. The investigation proved that ambient vibration modal experiments are enough for the experimental investigation of the modal properties of the structure.
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Fusco, T., R. Bacon, S. Kamann, S. Conseil, B. Neichel, C. Correia, O. Beltramo-Martin, J. Vernet, J. Kolb, and P. Y. Madec. "Reconstruction of the ground-layer adaptive-optics point spread function for MUSE wide field mode observations." Astronomy & Astrophysics 635 (March 2020): A208. http://dx.doi.org/10.1051/0004-6361/202037595.
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Context. Here we describe a simple, efficient, and most importantly fully operational point-spread-function (PSF)-reconstruction approach for laser-assisted ground layer adaptive optics (GLAO) in the frame of the Multi Unit Spectroscopic Explorer (MUSE) wide field mode. Aims. Based on clear astrophysical requirements derived by the MUSE team and using the functionality of the current ESO Adaptive Optics Facility we aim to develop an operational PSF-reconstruction (PSFR) algorithm and test it both in simulations and using on-sky data. Methods. The PSFR approach is based on a Fourier description of the GLAO correction to which the specific instrumental effects of MUSE wide field mode (pixel size, internal aberrations, etc.) have been added. It was first thoroughly validated with full end-to-end simulations. Sensitivity to the main atmospheric and AO system parameters was analysed and the code was re-optimised to account for the sensitivity found. Finally, the optimised algorithm was tested and commissioned using more than one year of on-sky MUSE data. Results. We demonstrate with an on-sky data analysis that our algorithm meets all the requirements imposed by the MUSE scientists, namely an accuracy better than a few percent on the critical PSF parameters including full width at half maximum and global PSF shape through the kurtosis parameter of a Moffat function. Conclusions. The PSFR algorithm is publicly available and is used routinely to assess the MUSE image quality for each observation. It can be included in any post-processing activity which requires knowledge of the PSF.
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Kollias, Pavlos, Mark A. Miller, Edward P. Luke, Karen L. Johnson, Eugene E. Clothiaux, Kenneth P. Moran, Kevin B. Widener, and Bruce A. Albrecht. "The Atmospheric Radiation Measurement Program Cloud Profiling Radars: Second-Generation Sampling Strategies, Processing, and Cloud Data Products." Journal of Atmospheric and Oceanic Technology 24, no. 7 (July 1, 2007): 1199–214. http://dx.doi.org/10.1175/jtech2033.1.
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Abstract The U.S. Department of Energy Atmospheric Radiation Measurement (ARM) Program operates millimeter-wavelength cloud radars in several climatologically distinct regions. The digital signal processors for these radars were recently upgraded and allow for enhancements in the operational parameters running on them. Recent evaluations of millimeter-wavelength cloud radar signal processing performance relative to the range of cloud dynamical and microphysical conditions encountered at the ARM Program sites have indicated that improvements are necessary, including significant improvement in temporal resolution (i.e., less than 1 s for dwell and 2 s for dwell and processing), wider Nyquist velocities, operational dealiasing of the recorded spectra, removal of pulse compression while sampling the boundary layer, and continuous recording of Doppler spectra. A new set of millimeter-wavelength cloud radar operational modes that incorporate these enhancements is presented. A significant change in radar sampling is the introduction of an uneven mode sequence with 50% of the sampling time dedicated to the lower atmosphere, allowing for detailed characterization of boundary layer clouds. The changes in the operational modes have a substantial impact on the postprocessing algorithms that are used to extract cloud information from the radar data. New methods for postprocessing of recorded Doppler spectra are presented that result in more accurate identification of radar clutter (e.g., insects) and extraction of turbulence and microphysical information. Results of recent studies on the error characteristics of derived Doppler moments are included so that uncertainty estimates are now included with the moments. The microscale data product based on the increased temporal resolution of the millimeter-wavelength cloud radars is described. It contains the number of local maxima in each Doppler spectrum, the Doppler moments of the primary peak, uncertainty estimates for the Doppler moments of the primary peak, Doppler moment shape parameters (e.g., skewness and kurtosis), and clear-air clutter flags.
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Lam, Heung Fai, Jun Hu, and Mujib Olamide Adeagbo. "Bayesian model updating of a 20-story office building utilizing operational modal analysis results." Advances in Structural Engineering 22, no. 16 (January 23, 2019): 3385–94. http://dx.doi.org/10.1177/1369433218825043.
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Most existing buildings are not equipped with long-term monitoring system. For the structural model updating and damage detection of this type of structures, ambient vibration test is popular as artificial excitation is not required. This article presents in detail the full-scale ambient vibration test, operational modal analysis, and model updating of a tall building. To capture the dynamic properties of the target 20-story building with limited number of sensors, a 15-setup ambient vibration test was designed to cover at least three measurement points (each consists of a vertical and two orthogonal horizontal measured degrees of freedom) for each selected floor. The modal parameters of each setup were extracted from the measured acceleration signals using a frequency domain decomposition method and were combined to form the global mode shape through the least-squares method. Due to the regularity of the building, a simple class of shear building models was employed to capture the dynamic characteristics of the building under lateral vibration. The identified modal parameters of the building were employed for the model updating of the shear building model to identify the distribution of inter-story stiffness. Since the “amount” of the measured information is small when compared to the “amount” of required information for identifying the uncertain parameters, the model updating problem is unidentifiable. To handle this problem, the Markov chain Monte Carlo–based Bayesian model updating method is employed in this study. The identified modal parameters revealed interesting features about the dynamic properties of the building. The well-matched results between model-predicted and identified modal parameters show the validity of the shear building model in this case study. This study provides valuable experience in the area of structural model updating and structural health monitoring.
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Iamamura, Bruno, Mathieu Rossi, Michel Hecquet, Vincent Lanfranchi, Sylvain Recorbet, and Florence Tridon. "Vibration and acoustic noise of industrial inductors associated to converters in the railway domain." COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 35, no. 6 (November 7, 2016): 1900–1909. http://dx.doi.org/10.1108/compel-03-2016-0098.
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Purpose The purpose of this paper is to present an original study of industrial inductors with different air-gap materials in order to reduce the vibration and noise of inductors. Acoustic comfort is an increasingly important factor at the design stage of industrial inductors associated to converters. In addition, power converters in the railway domain are more and more compact and powerful. Design/methodology/approach Experiments, simulations and test devices were used to determine the main physical phenomena that generate the undesirable audible noise. Electric and vibratory measurements (modal and operational analysis) were compared with the numerical calculations. PWM and sinusoidal supply were taken into account and different prototypes with different materials in the air-gap were built. Findings This study analyzes and details the origin of the electromagnetic noise due to the vertical mode, in order to reduce the vibration and noise of inductors. A detailed analysis using finite element simulation and experimental measurements of free-free mode or forced mode under electrical excitation was conducted to interpret the vibrations of the structure. In addition, in order to observe trends and the impact of magnetostriction effect, the authors propose a simplified model. Practical implications Electric and vibratory measurements (modal and operational analysis) are compared with the numerical calculations. Originality/value This paper gives a response about the origin of the noise with different experimental measurements. Changing the air-gap material is beneficial for the deflection of the inductor. However, it has been presented that, following the shape of the inductor, it is beneficial to reduce or increase the stiffness of the material depending on the column height. For a fixed Young’s modulus air-gap, a ratio Column height/air-gap thickness exists, which makes it possible to cancel the deflection.
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Wang, Zhongkui, Yui Makiyama, and Shinichi Hirai. "A Soft Needle Gripper Capable of Grasping and Piercing for Handling Food Materials." Journal of Robotics and Mechatronics 33, no. 4 (August 20, 2021): 935–43. http://dx.doi.org/10.20965/jrm.2021.p0935.
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Automation in the food industry is not as developed as in the automotive industry because of difficulties in handling food products with large variations in shape, size, and mechanical properties. In this paper, a pneumatic-driven soft needle gripper is proposed for handling food materials. It was constructed using a soft membrane and multiple rigid needle-like fingers. It can work under two operational modes: grasping and piercing. The grasping mode can be used to grasp shredded and chopped food materials. The piercing mode is for handling food products when only the top surface of the food product is available for handling. The needle gripper is fabricated using a multi-material 3D printer. Experimental tests on various food materials are conducted to validate grasping and piercing operations. The results of grasping tests suggest that the needle gripper can successfully grasp shredded and chopped food materials. A quantitative analysis shows that the relative standard deviation of the grasped food weight was within 20%. Although the results of piercing tests validate that the needle gripper can successfully handle various food materials, releasing the food materials involves certain difficulties.
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Brincker, Rune, Peter Olsen, Sandro Amador, Martin Juul, Abdollah Malekjafarian, and Mohammad Ashory. "Modal participation in multiple input Ibrahim time domain identification." Mathematics and Mechanics of Solids 24, no. 1 (October 14, 2017): 168–80. http://dx.doi.org/10.1177/1081286517733034.
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The Ibrahim time domain (ITD) identification technique was one of the first techniques formulated for multiple output modal analysis based on impulse response functions or general free decays. However, the technique has not been used much in recent decades due to the fact that the technique was originally formulated for single input systems that suffer from well-known problems in case of closely spaced modes. In this paper, a known, but more modern formulation of the ITD technique is discussed. In this formulation the technique becomes multiple input by adding some Toeplitz matrices over a set of free decays. It is shown that a special participation matrix can be defined that cancels out whenever the system matrix is estimated. The participation matrix becomes rank deficient if a mode is missing in the responses, but if any mode is present in one of the considered free decays, the participation matrix has full rank. This secures that all modes will be contained in the estimated system matrix. Finally, it is discussed how correlation functions estimated from the operational responses of structures can be used as free decays for the multiple-input ITD formulation, and the estimation errors of the identification technique are investigated in a simulation study with closely spaced modes. The simulation study shows that the multiple-input formulation provides estimates with significantly smaller errors on both mode shape and natural frequency estimates.
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Cui, Hongyu, Weiqiang Peng, Xin Xu, and Ming Hong. "A damage identification method for a thin plate structure based on PVDF sensors and strain mode." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 233, no. 14 (March 21, 2019): 4881–95. http://dx.doi.org/10.1177/0954406219838579.
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Damage identification methods for engineering structures based on vibration parameters have the advantages of easy detection and high precision; however, structural strain information is more sensitive to structural damage than displacement information. Traditional resistance strain sensors have low accuracy and poor stability when measuring structural strains. Therefore, this paper uses a highly sensitive polyvinylidene fluoride dynamic strain sensor to identify structural damage in a thin plate. The polyvinylidene fluoride sensor is used to obtain structural strain response information, and structural modal parameters are identified using operational modal identification methods based on the natural excitation technique and the eigensystem realization algorithm. This paper uses a damage index based on mode shape and flexibility. A new damage index based on the LU decomposition of the flexibility matrix is used to identify the damage of the thin plate structure. The effectiveness of the modal identification methods and the new damage index is validated via an elastic thin plate experiment. The results show that the modal identification method and the new damage index proposed in this paper can identify damage in a thin plate structure. Sensor comparison experiments also show that compared with a resistance strain sensor, the polyvinylidene fluoride sensor has higher damage sensitivity, better damage recognition and the ability to recognize farther from the sensor.
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Shen, Yue, Heping Zhu, Hui Liu, Yu Chen, and Erdal Ozkan. "Development of a Laser-Guided, Embedded-Computer-Controlled, Air-Assisted Precision Sprayer." Transactions of the ASABE 60, no. 6 (2017): 1827–38. http://dx.doi.org/10.13031/trans.12455.
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Abstract. An embedded computer-controlled, laser-guided, air-assisted, variable-rate precision sprayer was developed to automatically adjust spray outputs on both sides of the sprayer to match the presence, size, shape, and foliage density of tree crops in real time. The sprayer was the integration of an embedded computer, a touch screen, a 270° radial-range laser sensor, a travel speed sensor, a unique algorithm, a custom-designed automatic flow rate control unit, and 40 pulse-width-modulated (PWM) nozzles. The accuracy of the sprayer to detect different-sized trees and control the spray outputs of individual nozzles based on tree structures was tested in a commercial nursery. Spray deposition qualities between variable-rate and constant-rate operational modes of the sprayer were also compared. Test results demonstrated the capability of the sprayer to measure different trees accurately and then control the spray outputs of nozzles independently to match tree structure. The outline profile similarity of paired images taken with a digital camera and with the laser sensor for three trees ranged from 0.81 to 0.89. To spray trees of different sizes and shapes, the sprayer in variable-rate mode (VRM) consumed 12.1% to 43.3% of the spray volume that was used in constant-rate mode (CRM) with an application rate of 468 L ha-1. Moreover, the sprayer had 30% and 55% greater coverage areas per amount of spray deposits in VRM than in CRM. This innovative sprayer should have significant potential to reduce pesticide waste, provide sustainable crop protection to growers, and safeguard the environment. Keywords: Automation, Nursery, Orchard, Precision agriculture, Variable-rate sprayer.
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Vlacic, Ljubo, Toshio Fukuda, Yasuhisa Hasegawa, and Michel Parent. "Special Issue on Cybernetic City Transport Systems and Technologies." Journal of Robotics and Mechatronics 22, no. 6 (December 20, 2010): 683–84. http://dx.doi.org/10.20965/jrm.2010.p0683.
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The publication of this issue was driven by the vision that, in the not too distant future, Cybernetic Transport Systems (CTS) will be seen on city roads and dedicated infrastructures. TheWorld Council for Sustainability has projected that CTS will be seen in cities in as early as 2030 (Mobility 2030: Meeting the Challenges to Sustainability; World Business Council for Sustainable Mobility, July 2004). CTS are based on fully automated driverless urban road vehicles (CyberCars). They can also be based on Dual-Mode Vehicles (DMV) - conventional vehicles with Advanced Driver Assistance Technology (ADAT) and capable of driverless driving, on request by a driver. ADAT covers electronic and software products that assist drivers in driving. DMV assumes that a driver is not in control of the vehicle at all times but is fully responsible for vehicle operation throughout. Both CyberCars and DMVs co-operate through vehicle-to-vehicle and vehicle-to-infrastructure communication links thus enabling cybernetic transport to achieve higher traffic flows and improve network efficiency. Main CTS building blocks are CyberCars and/or Dual Mode Vehicles, Road Infrastructure Elements and CTS Traffic Management & Control Centre. These four blocks are interconnected, integrated and made interoperable through Communication Architecture and Protocols, and Operational Safety & Reliability Certification Procedures. A variety of CTS concepts have been prototyped and evaluated within the scope of projects such as: (i) Toyota’s Intelligent Multimode Transportation System (http://www.expo2005.or.jp/en/technology/imts.html); (ii) the CyberCars (http://www.cybercars.org); CyberMove (http://www.cybermove.org); (iii) CityMobil (http://www.citymobil-project.eu/); (iv) Safespot (http://www.safespot-eu.org/); (v) CVIS (http://www.cvisproject.org); (vi) Group Rapid Transit (http://www.2getthere.eu/Group Transit). The figure above shows a CTS prototyped by the CyberCars-2 Project Consortium. An extensive infield, i.e., on-road testing of operational performance of co-operative cybernetic transport solutions was conducted at several road tracks, the last being held at La Rochelle, France, in September 2008. This issue addresses a broad spectrum of theoretical and implementational topics related to CTS development and deployment including: • Cooperative Cybernetic Transport System Architecture • Real-time Decision Making by driverless vehicles • On-road testing of operational performance of CTS • Road-Crossing Landmarks Detection algorithm • Landmark Shape Detection algorithm • Road Shape Estimation algorithm, and • Vehicle-to-road infrastructure (traffic lights) communication solutions. In addition, this issue presents papers that deal with ADAT and analyses: • Acceptability and Usability of a Parking Assistance System for Elderly Drivers • Relationships between Car Accidents and a Driver’s Physiology and Psychology • 2D Localization in Urban Environment, and • Sustainability and Reusability aspects of Common Robotic Technology components. We hope you enjoy the issue!
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Reitter, S., K. Fröhlich, A. Seifert, S. Crewell, and M. Mech. "Evaluation of ice and snow content in the global numerical weather prediction model GME with CloudSat." Geoscientific Model Development 4, no. 3 (July 6, 2011): 579–89. http://dx.doi.org/10.5194/gmd-4-579-2011.
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Abstract. The present study evaluates the global numerical weather prediction model GME with respect to the grid-scale parameterization of frozen particles, both ice and snow, focusing on the performance of a diagnostic versus a prognostic precipitation scheme. As a reference, CloudSat Cloud Profiling Radar observations are utilized – the so far only near-globally available data set which vertically resolves clouds. Both the observation-to-model and the model-to-observation approach are applied and compared to each other. For the latter, the radar simulator QuickBeam is utilized. Criteria are applied to further improve the comparability between model and observations. The two model versions are statistically evaluated for a four-month period. The comparison reveals that the prognostic scheme reproduces the shape of the CloudSat frequency distributions for both ice water content (IWC) and reflectivity factor well, while the diagnostic scheme produces no large IWCs or reflectivity factors because snow falls out instantaneously. However, the prognostic scheme overestimates the occurrence of high ice water paths (IWP), especially in the mid-latitudes. Sensitivity tests show that an increased fall speed of snow successfully reduces IWP. Both evaluation approaches capture the general features, but for details, the two together deliver the largest informational content. In case of limited resources, the model-to-observation approach is recommended. Finally, the results indicate that the lack of IWC in most global circulation models might be attributed to the use of diagnostic precipitation schemes, i.e., the lack of snow aloft. Based on its good performance the prognostic scheme went into operational mode in February 2010. The adjusted snow fall speed went operational in December 2010. However, continual improvements of the ice microphysics are necessary, which can be assessed by the proposed evaluation technique.
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Eikenberg, S., K. Fröhlich, A. Seifert, S. Crewell, and M. Mech. "Evaluation of ice and snow content in the global numerical weather prediction model GME with CloudSat." Geoscientific Model Development Discussions 4, no. 1 (February 25, 2011): 419–43. http://dx.doi.org/10.5194/gmdd-4-419-2011.
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Abstract. The present study evaluates the global numerical weather prediction model GME with respect to frozen particles, both ice and snow, focusing on the performance of a diagnostic versus a prognostic precipitation scheme. As a reference, CloudSat Cloud Profiling Radar observations are utilized – the so far only near-globally available data set which vertically resolves clouds. Both the observation-to-model and the model-to-observation approach are applied and compared to each other. For the latter, the radar simulator QuickBeam is utilized. Criteria are applied to further improve the comparability between model and observations. The two model versions are statistically evaluated for a four-month period. The comparison reveals that the prognostic scheme reproduces the shape of the CloudSat frequency distributions for both ice water content (IWC) and reflectivity factor well, while the diagnostic scheme produces no large IWCs or reflectivity factors because snow falls out instantaneously. However, the prognostic scheme overestimates the occurrence of high ice water paths (IWP), especially in the mid-latitudes. Sensitivity tests show that an increased fall speed of snow successfully reduces IWP. Both approaches capture the general features, but for details, the two together deliver the largest informational content. In case of limited resources, the model-to-observation approach is preferred. Finally, the results indicate that the lack of IWC in most global circulation models might be attributed to the use of diagnostic precipitation schemes, i.e., the lack of snow aloft. Based on its good performance the prognostic scheme went into operational mode in February 2010. The adjusted snow fall speed went operational in December 2010. However, continual improvements of the ice microphysics are necessary, which can be assessed by the proposed evaluation technique.
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Jergensen, G. Eli, Amy McGovern, Ryan Lagerquist, and Travis Smith. "Classifying Convective Storms Using Machine Learning." Weather and Forecasting 35, no. 2 (April 1, 2019): 537–59. http://dx.doi.org/10.1175/waf-d-19-0170.1.
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Abstract We demonstrate that machine learning (ML) can skillfully classify thunderstorms into three categories: supercell, part of a quasi-linear convective system, or disorganized. These classifications are based on radar data and environmental information obtained through a proximity sounding. We compare the performance of five ML algorithms: logistic regression with the elastic-net penalty, random forests, gradient-boosted forests, and support-vector machines with both a linear and nonlinear kernel. The gradient-boosted forest performs best, with an accuracy of 0.77 ± 0.02 and a Peirce score of 0.58 ± 0.04. The linear support-vector machine performs second best, with values of 0.70 ± 0.02 and 0.55 ± 0.05, respectively. We use two interpretation methods, permutation importance and sequential forward selection, to determine the most important predictors for the ML models. We also use partial-dependence plots to determine how these predictors influence the outcome. A main conclusion is that shape predictors, based on the outline of the storm, appear to be highly important across ML models. The training data, a storm-centered radar scan and modeled proximity sounding, are similar to real-time data. Thus, the models could be used operationally to aid human decision-making by reducing the cognitive load involved in manual storm-mode identification. Also, they could be run on historical data to perform climatological analyses, which could be valuable to both the research and operational communities.
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Khoroshilov, V. S., and A. E. Zakrzhevskii. "Modelling of Spacecraft Dynamics at Deployment of Large Elastic Structure." Modelling and Simulation in Engineering 2012 (2012): 1–13. http://dx.doi.org/10.1155/2012/497916.
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In this paper, a new approach to the modelling of the deployment dynamics of a flexible multi-body system with the time dependent configurations is demonstrated in the frame of the study the dynamics of a spacecraft with the gyro-gravitational system of stabilization. Primarily the gravitational stabilizer that is made as a pantograph structure is in a compact form. The deployment of a flexible pantograph structure is performed after placing the spacecraft into orbit and completion of the preliminary damping by a special jet-propelled system, and after uncaging the gyros. After its deployment, the pantograph turns into an elongated structure that serves as a gravitational stabilizer and carrier of solar batteries. The objective of the study is the creation of the generalized mathematical model and the conducting of the computational modelling of the spacecraft dynamics. The equations of motion are derived with the use of the Eulerian-LaGrangian formalism and symbolic computing. Numerical simulations of the typical operational mode of the system are conducted taking into account various control profiles for the deployment. Numerical results indicate that the system used for attitude stabilization ensures the shape of the deployed design and prescribed accuracy of the orientation.
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Miller, Paul, Andrew W. Ellis, and Stephen Keighton. "A Preliminary Assessment of Using Spatiotemporal Lightning Patterns for a Binary Classification of Thunderstorm Mode." Weather and Forecasting 30, no. 1 (February 1, 2015): 38–56. http://dx.doi.org/10.1175/waf-d-14-00024.1.
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Abstract This study provides a preliminary, regional assessment of the viability of using spatiotemporal lightning patterns to classify storms into single- versus multi- and supercell storm modes. Total lightning flashes (intracloud and cloud-to-ground flashes) occurring during the afternoon and evening of the period May–August 2012 within an area of the central Appalachian Mountains region were grouped based on their spatial and temporal characteristics using single-linkage clustering. The resulting discrete thunderstorm clusters were characterized in terms of duration, motion, areal extent, and shape. These values were used to formulate four individual attribute scores representing the similarity to the expected values for a typical single-cell thunderstorm. The four scores were then combined into a storm index (SI) using relative weights determined through the analytic hierarchy process (AHP) performed on input from operational forecasters. Of the study days, 89 (72.4%) possessed appreciable lightning, of which 36 (40%) possessed a defined minimum amount of lightning activity required for further analysis. These 36 storm days were divided into two tiers according to the distribution of median daily SI values. The tier containing the 24 storm days (66.7%) with the largest median SI values possessed statistically significant smaller values of 0–6-km wind shear [13.8 knots (kt; 1 kt = 0.51 m s−1)] versus the 12 days in the lower tier of SI values (26.5 kt). This consistency between the total lightning-based classification scheme and increased vertical wind shear associated with lightning-defined multi- and supercells, also evident in synoptic atmospheric composites, lends credibility to the procedure.
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Nicoletti, Rodrigo, and Ilmar Ferreira Santos. "Frequency Response Analysis of an Actively Lubricated Rotor/Tilting-Pad Bearing System." Journal of Engineering for Gas Turbines and Power 127, no. 3 (June 24, 2005): 638–45. http://dx.doi.org/10.1115/1.1850940.
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In the present paper, the dynamic response of a rotor supported by an active lubricated tilting-pad bearing is investigated in the frequency domain. The theoretical part of the investigation is based on a mathematical model obtained by means of rigid body dynamics. The oil film forces are inserted into the model by using two different approaches: (a) linearized active oil film forces and the assumption that the hydrodynamic forces and the active hydraulic forces can be decoupled, and (b) equivalent dynamic coefficients of the active oil film and the solution of the modified Reynolds equation for the active lubrication. The second approach, based on the equivalent dynamic coefficients, leads to more accurate results because it includes the frequency dependence of the active hydraulic forces. Theoretical and experimental results reveal the feasibility of reducing resonance peaks by using the active lubricated tilting-pad bearing. By applying a simple proportional controller, it is possible to reach 30% reduction of the resonance peak associated with the first rigid body mode shape of the system. One of the most important consequences of such a vibration reduction in rotating machines is the feasibility of increasing their operational range by attenuating resonance peaks and reducing vibration problems.
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Gonçalves, José Teixeira, Stanimir Valtchev, and Rui Melicio. "Current Interactions Mitigation in 3-Phase PFC Modular Rectifier through Differential-Mode Choke Filter Boost Converter." Applied Sciences 11, no. 4 (February 13, 2021): 1684. http://dx.doi.org/10.3390/app11041684.
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In this paper, a new way to mitigate the current interactions is proposed. The problem of current interactions arises when a modular three-phase (3-phase) rectifier (three single-phase modules) with boost converter for power factor correction (PFC) is used. A new differential-mode choke filter is implemented in the developed boost converter. The choke here is a specially made differential inductor in the input of the boost converter that eliminates the known current interactions. To prove the new concept, a study of the level of mitigation of the current interactions is presented. The control is operated in continuous driving mode (CCM), and the popular UC3854B circuit was used for this. The rectifier proposal is validated through a set of simulations performed on the PSIM 12.0 platform, as well as the construction of a prototype. With the results obtained, it is confirmed that the differential-mode choke filter eliminates the current interactions. It is observed that at the input of the rectifier, a sinusoidal alternating current with a low level of harmonic distortion is consumed from the grid. The sinusoidal shape of the phase current proves that a better power factor capable of meeting the international standards is obtained, and that the circuit in its initial version is operational. This proven result promises a good PFC operation, to guarantee the better quality of the electrical energy, being able to be applied in systems that require a high PFC, e.g., in battery charging, wind systems, or in aeronautics and spacecrafts.
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Wang, Zhengjian, Xichun Luo, Haitao Liu, Fei Ding, Wenlong Chang, Liang Yang, Jianguo Zhang, and Andrew Cox. "A high-frequency non-resonant elliptical vibration-assisted cutting device for diamond turning microstructured surfaces." International Journal of Advanced Manufacturing Technology 112, no. 11-12 (January 15, 2021): 3247–61. http://dx.doi.org/10.1007/s00170-021-06608-3.
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AbstractIn recent years, research has begun to focus on the development of non-resonant elliptical vibration-assisted cutting (EVC) devices, because this technique offers good flexibility in manufacturing a wide range of periodic microstructures with different wavelengths and heights. However, existing non-resonant EVC devices for diamond turning can only operate at relatively low frequencies, which limits their machining efficiencies and attainable microstructures. This paper concerns the design and performance analysis of a non-resonant EVC device to overcome the challenge of low operational frequency. The structural design of the non-resonant EVC device was proposed, adopting the leaf spring flexure hinge (LSFH) and notch hinge prismatic joint (NHPJ) to mitigate the cross-axis coupling of the reciprocating displacements of the diamond tool and to combine them into an elliptical trajectory. Finite element analysis (FEA) using the mapped meshing method was performed to assist the determination of the key dimensional parameters of the flexure hinges in achieving high operational frequency while considering the cross-axis coupling and modal characteristics. The impact of the thickness of the LSFH on the sequence of the vibrational mode shape for the non-resonant EVC device was also quantitatively revealed in this study. Moreover, a reduction in the thickness of the LSFH can reduce the natural frequency of the non-resonant EVC device, thereby influencing the upper limit of its operational frequency. It was also found that a decrease in the neck thickness of the NHPJ can reduce the coupling ratio. Experimental tests were conducted to systematically evaluate the heat generation, cross-axis coupling, modal characteristics and diamond tool’s elliptical trajectory of a prototype of the designed device. The test results showed that it could operate at a high frequency of up to 5 kHz. The cross-axis coupling ratio and heat generation of the prototype are both at an acceptable level. The machining flexibility and accuracy of the device in generating microstructures of different wavelengths and heights through tuning operational frequency and input voltage have also been demonstrated via manufacturing the micro-dimple arrays and two-tier microstructured surfaces. High-precision microstructures were obtained with 1.26% and 10.67% machining errors in wavelength and height, respectively.
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Sandford, Caroline, Anthony Illingworth, and Robert Thompson. "The Potential Use of the Linear Depolarization Ratio to Distinguish between Convective and Stratiform Rainfall to Improve Radar Rain-Rate Estimates." Journal of Applied Meteorology and Climatology 56, no. 11 (November 2017): 2927–40. http://dx.doi.org/10.1175/jamc-d-17-0014.1.
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AbstractA major source of errors in radar-derived quantitative precipitation estimates is the inhomogeneous nature of the vertical reflectivity profile (VPR). Operational radars generally scan in azimuth at constant elevation (PPI mode) and provide limited VPR information, so predetermined VPR shapes with limited degrees of freedom are needed to correct for the VPR in real time. Typical stratiform VPRs have a sharp peak below the 0° isotherm, known as the “bright band,” caused by the presence of large melting snowflakes, but this feature is not present in convective cores where the melting ice is in the form of graupel or compact ice. Inappropriate correction assuming a brightband VPR can lead to underestimation of rain rates, with particular impacts in intense convective storms. This paper proposes the use of high values of linear depolarization ratio (LDR) measurements to confirm the presence of large melting snowflakes and lower values for melting graupel or high-density ice as a prerequisite to selecting a suitable profile shape for VPR correction. Using a climatologically representative dataset of short-range, high-resolution C-band vertical profiles, the peak value of the LDR in the melting layer is shown to have robust skill in identifying VPRs without bright band, with the “best” performance at a threshold of −20 dB. Further work is proposed to apply this result to improving corrections for VPR at longer range, where the limited effect of beam broadening on LDR peaks could provide advantages over other available methods.
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Козлов, Вячеслав, Vyacheslav Kozlov, Алексей Скрыпников, Aleksey Skrypnikov, Елена Микова, Elena Mikova, Роман Могутнов, Roman Mogutnov, Евгений Чирков, and E. Chirkov. "FORMATION OF THE MODEL OF DESIGNING THE SYSTEM "ROAD CONDITIONS - TRANSPORT FLOWS" AND WAYS OF ITS IMPLEMENTATION." Forestry Engineering Journal 8, no. 1 (March 19, 2018): 104–11. http://dx.doi.org/10.12737/article_5ab0dfbe6ece23.91630316.
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A model for managing the system "road conditions - traffic flows" is proposed that allows to ensure the functioning of the complex "driver - car - road - environment" in any weather and climate conditions. The analysis of the proposed model and target functional shows that optimization of the "road conditions - traffic flow" system can proceed in many directions, the main of which are: optimal development and placement of the network of forest roads, improving their technical level and level of maintenance, road engineering equipment , efficient traffic management, excluding the rational distribution of forest traffic on the network of forest roads and the management modes on individual logging roads and sections of forest roads. The developed model makes it possible to carry out a theoretical analysis and experimental verification of the interaction between «driver-car-road-environment" system in order to identify the reserves of increasing efficiency of its operation and purposeful management of this process. Transport-operational characteristics of logging roads are the main factors that shape the conditions of timber transport on the road, mode, convenience and safety of traffic and determine the efficiency of road transport, and connections of many characteristics of roads with the traffic modes have deterministic, corrective character. These patterns are the basis for the development of technical requirements for logging roads. The proposed model for integrated creation and management of the functioning of a forest road may already be implemented. However, the design of roads is expedient to provide complex control engineering and organizational measures to ensure the estimated traffic conditions during the whole period of operation of the road, regardless of the time of year and weather and climate conditions. Evaluation of the effectiveness of taken decisions should be made with mandatory consideration for ensuring the required performance of logging road in adverse periods of the year and in difficult weather conditions
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Klyuchareva, S. V., I. V. Ponomarev, S. B. Topchiy, and A. E. Pushkareva. "Treatment of rhinophyma using a copper vapor laser." Vestnik dermatologii i venerologii 94, no. 5 (February 12, 2019): 50–58. http://dx.doi.org/10.25208/0042-4609-2018-94-5-50-58.
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Background.Rhinophyma is considered to be the most severe stage of rosacea, associated with the proliferation of the nose skin epithelium, hyperproduction of the sebaceous glands and telangiectasia.The treatment of rhinophyma remains a difficult task. One of the problems associated with rhinophyma is thickened and lumpy skin, penetrated with telangiectasias. The use of laser radiation in the treatment of rhinophyma seems to be promising, since this method allows blood vessels to be selectively heated.For the first time, we describe the treatment of rhinophyma using a copper vapour laser (CVL) equipped with a computerized scanner.Patient description.A 63-year-old male with Fitzpatrick skin type II was treated using an CVL (‘Yakhroma-med' model, RaS P. N. Lebedev Physical Institute). The clinical manifestations of the disease were typical of the phymatous or hypertrophic rhinophyma type, including significant thickening of the tissues and an uneven roughness of the skin surface. The treatment was carried out using a radiation wavelength of 578 nm, exposure duration of 0.2 s and energy exposure (fluence) of 15-30 J/cm2. Operational parameters used for the CVL in the scanner mode were the average power of 0.6-1.2 W and the focusing size of the light spot on the skin of 0.6 mm. The hexagonal mode of the scanning head was used with a maximum size of 12 mm and 1 mm distance between the centres of the laser spots. The treatment resulted in the restoration of the natural nose shape without redness. No side effects were noted.Conclusion:CVL radiation provided a selective photodisruption of the vessels with increased diameter.Due to the remodelling of the vasculature, the described method showed excellent results in the treatment of rhinophyma without side effects.
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Dillon-Gibbons, Craig, Cameron Galtry, Nicholas Boustead, Nicholas D'Arcy-Evans, Phillip Kurts, Eric Jal, Andrew Kilner, and Daniel Washington. "Development of Oil Spill Response Decision Support Tool for Aerial Spraying of Dispersants." International Oil Spill Conference Proceedings 2017, no. 1 (May 2017): 2017–280. http://dx.doi.org/10.7901/2169-3358-2017.1.2017-280.
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2017-280 Abstract This paper describes the development of a Decision Support Tool (DST) for response planning associated with aerial operations for offshore oil spills. The research program was formulated to include characterization of dispersant spray drift through numerical modeling to generate a database of drift response for a range of airframes and environmental conditions. The drift of aerial dispersants is dependent on a number of different influences including airframe shape and aerodynamics, environmental effects, flight conditions and aerial dispersant make up. As with agricultural spraying, oil spill response spraying has the potential of spray drift to impact upon ecologically sensitive regions and/or areas occupied by people or marine mammals surfacing in the spill area. The development of the DST included an evaluation of existing regulatory models, investigating their application to the offshore environment. It was found that, due to inherent limitations and simplifications, particularly for the larger airframes considered, the existing models were under conservative in comparison with Computational Fluid Dynamics (CFD) models in the near field wake regions for offshore spraying purposes. To address these issues, a combination of scaling factors and the use of inviscid vortex transport and particle dispersion models were adopted for inclusion in the DST. It is envisaged that, once validated further, the DST will become an invaluable tool for Oil Spill Response Operators (OSROs) and decision planners in both the operational mode of providing information to aid in establishing setback distances and in the planning mode to assist with the identification of windows of opportunity conducive to spraying operations.
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Dillon-Gibbons, Craig, Cameron Galtry, Nicholas Boustead, Nicholas D’Arcy-Evans, Phillip Kurts, Eric Jal, Andrew Kilner, and Daniel Washington. "Development of Oil Spill Response Decision Support Tool for Aerial Spraying of Dispersants." International Oil Spill Conference Proceedings 2017, no. 1 (May 1, 2017): 725–44. http://dx.doi.org/10.7901/2169-3358-2017.1.725.
Full textAbstract:
2017-280 Abstract This paper describes the development of a Decision Support Tool (DST) for response planning associated with aerial operations for offshore oil spills. The research program was formulated to include characterization of dispersant spray drift through numerical modeling to generate a database of drift response for a range of airframes and environmental conditions. The drift of aerial dispersants is dependent on a number of different influences including airframe shape and aerodynamics, environmental effects, flight conditions and aerial dispersant make up. As with agricultural spraying, oil spill response spraying has the potential of spray drift to impact upon ecologically sensitive regions and/or areas occupied by people or marine mammals surfacing in the spill area. The development of the DST included an evaluation of existing regulatory models, investigating their application to the offshore environment. It was found that, due to inherent limitations and simplifications, particularly for the larger airframes considered, the existing models were under conservative in comparison with Computational Fluid Dynamics (CFD) models in the near field wake regions for offshore spraying purposes. To address these issues, a combination of scaling factors and the use of inviscid vortex transport and particle dispersion models were adopted for inclusion in the DST. It is envisaged that, once validated further, the DST will become an invaluable tool for Oil Spill Response Operators (OSROs) and decision planners in both the operational mode of providing information to aid in establishing setback distances and in the planning mode to assist with the identification of windows of opportunity conducive to spraying operations.
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Huang, Lifan, Bin Luo, Mingmin Ding, Chunshui Zhang, and Yangjie Ruan. "A Cumulative Expansion Force-Finding Method for Suspension-Cable Truss Composite Structure." Advances in Civil Engineering 2020 (December 28, 2020): 1–13. http://dx.doi.org/10.1155/2020/8828658.
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Suspension-cable truss composite structure is a new type of cable-strut structure which combines the conventional cable structure with the rigid truss. By laying rigid roofing slabs, this composite structure offsets most effect of the wind suction, reduces the axial force of the stable cables, and reduces the large vertical displacement effectively when compared with conventional cable trusses. For this new structure, the deformation relevance between adjacent substructures results in a nonindependent and stable union. To effectively and precisely find the cable forces of a suspension-cable truss composite structure for the construction completion state, a proper optimization order and a suitable selection of the substructures are necessary. In this paper, the structural mechanical characteristics of the suspension-cable truss composite structure are introduced at first, to reveal the force transmission path between adjacent substructures. Secondly, the cumulative expansion force-finding method (CEFM) is proposed to obtain the optimal mode of the cable force distribution with a suitable operational efficiency. A numerical example is introduced and analyzed to verify the accuracy and feasibility of this method afterwards. The results show that CEFM could find out the optimal cable force distribution of the suspension-cable truss composite structure, with a geometry shape of whole structure and a rational stress level of all the components.
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Chiriatti, Giorgia, Giacomo Palmieri, Cecilia Scoccia, Matteo Claudio Palpacelli, and Massimo Callegari. "Adaptive Obstacle Avoidance for a Class of Collaborative Robots." Machines 9, no. 6 (June 3, 2021): 113. http://dx.doi.org/10.3390/machines9060113.
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In a human–robot collaboration scenario, operator safety is the main problem and must be guaranteed under all conditions. Collision avoidance control techniques are essential to improve operator safety and robot flexibility by preventing impacts that can occur between the robot and humans or with objects inadvertently left within the operational workspace. On this basis, collision avoidance algorithms for moving obstacles are presented in this paper: inspired by algorithms already developed by the authors for planar manipulators, algorithms are adapted for the 6-DOF collaborative manipulators by Universal Robots, and some new contributions are introduced. First, in this work, the safety region wrapping each link of the manipulator assumes a cylindrical shape whose radius varies according to the speed of the colliding obstacle, so that dynamical obstacles are avoided with increased safety regions in order to reduce the risk, whereas fixed obstacles allow us to use smaller safety regions, facilitating the motion of the robot. In addition, three different modalities for the collision avoidance control law are proposed, which differ in the type of motion admitted for the perturbation of the end-effector: the general mode allows for a 6-DOF perturbation, but restrictions can be imposed on the orientation part of the avoidance motion using 4-DOF or 3-DOF modes. In order to demonstrate the effectiveness of the control strategy, simulations with dynamic and fixed obstacles are presented and discussed. Simulations are also used to estimate the required computational effort in order to verify the transferability to a real system.
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Asadov, Kh G., and Sh N. Dzhakhidzade. "Complex multi-range aggregate spectral measurements for environmental objects: optimization and synthesis of measurement procedures." Radio industry (Russia) 29, no. 4 (December 1, 2019): 18–25. http://dx.doi.org/10.21778/2413-9599-2019-29-4-18-25.
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The research aims at a synthesis of new complex procedures for multi-range aggregate spectral measurements of environmental objects, for which both the absorption spectrum and reflectivity spectrum are typical. As a basic research methodology, we have applied the vibrational optimization to calculate an optimal shape of introduced interconnections between main operational parameters of the measurement experiment. Authors have shown that, in considerations of absorption spectrum for the objects in question, we can estimate results of aggregate multispectral measurements with the new indicator of reliability, expressed by the signal-to-noise ratio at outputs of spectral channels in the multispectral meter. Having summed up the indicator values for each measuring spectral channel and replacing the objects that we are exploring with the hohlraum model described with the Planck function, we obtain the formula to find the best relationship between the standard means-square deviation of noises and model function. Based on the mentioned best relationship, we have found the best dependence of the standard means-square deviation of noises on the wavelength and absolute temperature. Authors have shown that in terms of the best mode and with certain values of the wavelength, the standard means-square deviation of noises might have the highest value, i. e., reliability of the measurement result will be the lowest in case of this wavelength. With regard to environmental objects that have the reflectivity spectrum, authors gave the general characteristics of aggregate two-wave measurements for chlorophyll of plants, described with mutually inverse spectral parameters. There is the estimate of the higher signal-to-noise ratio in terms of the mentioned type of aggregate two-wave measurements compared to single-wave ones. The authors have stated and solved the problem of the best choice of weight coefficients in terms of essential attenuations in measuring channels.
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Dimino, Ignazio, Federico Gallorini, Massimiliano Palmieri, and Giulio Pispola. "Electromechanical Actuation for Morphing Winglets." Actuators 8, no. 2 (May 15, 2019): 42. http://dx.doi.org/10.3390/act8020042.
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As a key enabler for future aviation technology, the use of servo electromechanical actuation offers new opportunities to transition innovative structural concepts, such as biomimicry morphing structures, from basic research to new commercial aircraft applications. In this paper, the authors address actuator integration aspects of a wing shape-changing flight surface capable of adaptively enhancing aircraft aerodynamic performance and reducing critical wing structural loads. The research was collocated within the Clean Sky 2 Regional Aircraft Demonstration Platform (IADP) and aimed at developing an adaptive winglet concept for green regional aircraft. Finite Element-based tools were employed for the structural design of the adaptive device characterized by two independent movable tabs completely integrated with a linear direct-drive actuation. The structural design process was addressed in compliance with the airworthiness needs posed by the implementation of regional airplanes. Such a load control system requires very demanding actuation performance and sufficient operational reliability to operate on the applicable flight load envelope. These requirements were met by a very compact direct-drive actuator design in which the ball recirculation device was integrated within the screw shaft. Focus was also given to the power-off electric brake necessary to block the structure in a certain position and dynamically brake the moveable surface to follow a certain command position during operation. Both the winglet layout static and dynamic robustness were verified by means of linear stress computations at the most critical conditions and normal mode analyses, respectively, with and without including the integrated actuator system.
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Gold, David A., and John W. Nielsen-Gammon. "Potential Vorticity Diagnosis of the Severe Convective Regime. Part I: Methodology." Monthly Weather Review 136, no. 5 (May 1, 2008): 1565–81. http://dx.doi.org/10.1175/2007mwr2090.1.
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Abstract Observational and modeling studies have shown that shear and instability are powerful predictors of the likelihood of severe weather and tornadoes. To the extent that upper-tropospheric forecast errors can be described as potential vorticity (PV) anomalies on the forecasted PV field, knowing (and being able to quantify) the effects of such errors on shear and instability would allow forecasters to anticipate the effects of those errors on the likely mode of severe weather. To test the sensitivity of the severe convective environment to PV fluctuations, a PV inversion framework is adopted that utilizes nonlinear balance. The observed PV field is modified in a way that mimics realistic perturbations of trough intensity, location, or shape. Soundings, including moisture profiles, are reconstructed from the balanced geopotential height field assuming that air parcels conserve mixing ratio while their isentropic surfaces are displaced upward or downward by the addition of anomalous PV. Unperturbed balanced soundings agree reasonably well with full, unbalanced soundings, and differences are attributable to departures from nonlinear balance in areas of strong vorticity or acceleration. Balanced vertical wind profiles do not include the effects of friction, so the vertical shear of the balanced wind departs unacceptably from total shear within the lowest 1 km of the troposphere. The balanced wind perturbations are added to the total analyzed shear profile to estimate the effect of PV perturbations on shear and storm-relative helicity. By this process, the importance of typical or hypothesized upper-tropospheric forecast errors may be addressed in an idealized, case-study, or operational context.
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Bazhenov, Viktor, Olga Krivenko, and Andrii Kozak. "Modal analysis of a complex shell structure under operational loads." Strength of Materials and Theory of Structures, no. 106 (May 24, 2021): 5–13. http://dx.doi.org/10.32347/2410-2547.2021.106.5-13.
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The results of calculation of a complex shell structure under the action of operational loads are presented. A three-section cooling tower, called a three-petal cooling tower, is regarded as a complex-shaped structure. Three variants of loads on the shell are considered: wind pressure, heating and load combination. The design model of a shell of a complex shape is based on the developed universal spatial finite element. The universal spatial finite element allows one to take into account the geometric features of structural elements for a thin shell (constant or varying thickness, knees, ribs, cover plates, holes, cavities, channels, inserts, facets) and multilayer structure of the material. According to the method, thin and medium thickness shells of various shapes and structures are considered. The shells are under the action of static mechanical and temperature loads. The finite element method is based on the unified positions of the three-dimensional geometrically nonlinear theory of thermoelasticity and the moment finite element scheme. The method for determining the natural vibrations of thin-walled shell structures is based on an integrated approach. Modal analysis is carried out taking into account the prestressed and deformed states of the shell at each step of thermomechanical loading. Thus, the problem of determining the natural frequencies and vibration modes of the shell is solved by the step method in two stages.