Bibliografías temáticas / Natural frequency

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Literatura académica sobre el tema "Natural frequency"

Autor: Grafiati

Publicado: 4 de junio de 2021

Última modificación: 11 de septiembre de 2023

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Artículos de revistas sobre el tema "Natural frequency"

Lee, Joon-Ho y Hyo-Tae Kim. "Improvement of natural frequency extraction in frequency domain". Electronics Letters 35, n.º 3 (1999): 197. http://dx.doi.org/10.1049/el:19990159.

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Do. "Analysis of Natural Frequency According to Span of Foot-bridges". Journal of Korean Society of Steel Construction 26, n.º 5 (2014): 375. http://dx.doi.org/10.7781/kjoss.2014.26.5.375.

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Rapo, Marja, Jukka Aho y Tero Frondelius. "Natural Frequency Calculations with JuliaFEM". Rakenteiden Mekaniikka 50, n.º 3 (21 de agosto de 2017): 300–303. http://dx.doi.org/10.23998/rm.65040.

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This article presents a simple natural frequency analysis performed with JuliaFEM - an open-source finite element method program. The results are compared with the analysis results pruduced with a commercial software. The comparison shows that the calculation results between the two programs do not differ significantly.

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KAŠŠAY, Peter. "TORSIONAL NATURAL FREQUENCY TUNING BY MEANS OF PNEUMATIC FLEXIBLE SHAFT COUPLINGS". Scientific Journal of Silesian University of Technology. Series Transport 89 (1 de diciembre de 2015): 57–60. http://dx.doi.org/10.20858/sjsutst.2015.89.6.

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Lee, J. H. y S. H. Jeong. "Performance of natural frequency-based target detection in frequency domain". Journal of Electromagnetic Waves and Applications 26, n.º 17-18 (17 de octubre de 2012): 2426–37. http://dx.doi.org/10.1080/09205071.2012.735789.

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YOSHIOKA, Muneyuki. "Natural Frequency of Gaseous Pressure Probes". Transactions of the Society of Instrument and Control Engineers 26, n.º 7 (1990): 836–38. http://dx.doi.org/10.9746/sicetr1965.26.836.

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Poznyak, Elena V., Vladimir P. Radin y Olga V. Novikova. "Time-frequency Analysis of Natural Accelerograms". Vestnik MEI 5 (2019): 135–41. http://dx.doi.org/10.24160/1993-6982-2019-5-135-141.

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Lin, Jian y Robert G. Parker. "NATURAL FREQUENCY VEERING IN PLANETARY GEARS*". Mechanics of Structures and Machines 29, n.º 4 (30 de noviembre de 2001): 411–29. http://dx.doi.org/10.1081/sme-100107620.

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Kubina, Richard M. y Fan-Yu Lin. "Defining frequency: A natural scientific term." Behavior Analyst Today 9, n.º 2 (2008): 125–29. http://dx.doi.org/10.1037/h0100651.

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Wang, P. W. y C. C. Cheng. "Natural Frequency Tuning Using Structural Patches". Journal of Vibration and Acoustics 127, n.º 1 (1 de febrero de 2005): 28–35. http://dx.doi.org/10.1115/1.1855926.

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A novel method for shifting the natural frequencies of a structure to specific values using structural patches is introduced. When a host structure is bonded with multiple structural patches, its natural frequencies can be shifted to the desired values by tuning the patch thickness and the patch location on the host structure. These parameters can be analytically determined using the methodology proposed in this paper. The time consuming process produced using the traditional optimal search method is thereby avoided. The results show that multiple natural frequencies can be changed simultaneously to the desired values. The number of natural frequencies shifted requires using the same number of structural patch pairs. Several examples using this technique are demonstrated and the results are experimentally validated.

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Tesis sobre el tema "Natural frequency"

Kannappan, Laxmikant Aerospace Civil &amp Mechanical Engineering Australian Defence Force Academy UNSW. "Damage detection in structures using natural frequency measurements". Awarded by:University of New South Wales - Australian Defence Force Academy. Aerospace, Civil & Mechanical Engineering, 2009. http://handle.unsw.edu.au/1959.4/44852.

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In the last two decades, the emphasis in aircraft maintenance has been on developing online structural health monitoring systems to replace conventional non destructive inspection techniques which require considerable down-time, human effort and cost. Vibration based damage detection is one of the most promising techniques for implementation in Structural Health Monitoring (SHM). In vibration based methods, the presence of damage is detected by monitoring changes in one of the dynamic parameters of the structure, resonant frequencies, modeshapes or damping characteristics. Compared to modeshape based methods, frequency based methods have the advantage that measurements need to be taken only at a single location. Previous developments on frequency based techniques have relied on Finite Element Model updating; analytical techniques have hitherto been restricted to beams due to the complexity in developing equations for cracked two dimensional structures. In this thesis the analytical approach using an energy formulation is extended to plates with through-thickness cracks, where modeshapes from either numerical modelling or experimental measurements can be employed to determine the energy of vibration. It is demonstrated that by using a hybrid approach, incorporating experimentally measured modeshapes along with measured changes in frequencies, the damage parameters can be estimated without resorting to theoretical modelling or numerical analysis. The inverse problem of finding the crack location, size and orientation from measured changes in frequencies is addressed using minimisation techniques. The forward problem and the inverse algorithm is first validated using numerical simulation and experimental testing of beams with edge cracks and centre cracks. The application of the methodology to the two dimensional case is then validated by numerical simulation and experimental modal analysis of plates with through thickness cracks. A statistical procedure is developed for determination of the 90/95 probability of crack detection and the minimum detectable crack size in both cases. It is demonstrated that the measurement of frequency changes can be successfully employed to detect and assess the location and size of cracks in beams and plates, using modeshapes from theory, Finite Element Analysis.

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Shao, Fei. "Natural frequency analysis for osseointegration trans-femoral implant". Thesis, University of Surrey, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.443397.

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Beavers, Timothy Allan. "Fundamental Natural Frequency of Steel Joist Supported Floors". Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/35880.

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Three aspects in determining the first natural frequency of steel joist supported floors were studied. The aspects are: 1) determining which finite element model best predict the behavior of joist-slab tee-beams, 2) investigating the ability of proposed equations to calculate the effective moment of inertia of joist-slab tee-beams, and 3) developing a finite element model to predict the first natural frequency of steel joist supported floors. Several finite element models were tested to determine which one best predicted the experimental results of six joist-slab setups. The model which best predicted the experimental results was used. Next, a study was done to determine the ability of a proposed equation to predict the effective moment of inertia of joist-slab tee-beams. The study modeled and analyzed 130 joist-slab configurations and compared the results to those calculated using the proposed equations. Finally, a finite element modeling technique was developed to predict the first natural frequency of steel joist supported floors. Seven in-situ floors were experimentally tested, and those results were compared to the predicted values given by the models.
Master of Science

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Labib, Amr. "Crack detection in frames using natural frequency degradations". Thesis, Cardiff University, 2016. http://orca.cf.ac.uk/88543/.

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Crack detection at an early stage can prevent catastrophic structural failures. In this thesis, the inverse problem of crack detection in frames is studied. The direct problem of calculating the natural frequencies of beams and frames with multiple cracks is first tackled. A new method for natural frequency calculation is devised. The cracks are modelled as rotational springs. 4 × 4 dynamic stiffness matrices for beams are evaluated in a recursive manner, according to the number of cracks, by applying partial Gaussian eliminations. The resulting transcendental eigenvalue problem is solved using the Wittrick–Williams algorithm to extract the natural frequencies. Additional sign counts resulting from the partial Gaussian eliminations must be accounted for when applying the algorithm. The dynamic stiffness matrix of a frame with multiply cracked members is then assembled. The natural frequency calculation method forms a basis for detecting a single crack in a frame using only natural frequency measurements. Each frame member is discretised into a number of points. Selected natural frequencies are calculated accurately in the uncracked case and when the crack is placed individually at each discretisation point. The variation between the uncracked and cracked frequencies is normalised giving a number of curves corresponding to the selected frequencies. The normalisation is then applied on the measured frequencies. For noise free measurements, point crack locations are obtained. Applying the principles of interval arithmetic, noisy measurements give crack location ranges. Empirical probability distributions are used to graphically represent these ranges and their relative probabilities. Crack severity ranges are then obtained. The detection method is validated experimentally on a frame with scaled down dimensions. The fast Fourier transform is used to convert the time domain vibration signal into the frequency domain. Using higher order natural frequencies, two enhancement procedures for the detection method are devised and applied theoretically.

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Lane, Dewey Hobson III. "Identification of natural frequency components of articulated flexible structures". Thesis, Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/15972.

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Lawrence, Emma Jane. "Identifying natural modifiers of meiotic crossover frequency in Arabidopsis thaliana". Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/289733.

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During meiosis, homologous chromosomes pair and undergo reciprocal genetic exchange, producing crossovers. This generates genetic diversity and is required for balanced homolog segregation. Despite the critical functions of crossovers, their frequency and distribution varies extensively within and between species. This crossover variation can be caused by trans-modifiers within populations, which encode diffusible molecules that influence crossover formation elsewhere in the genome. This project utilised natural accessions of Arabidopsis thaliana to identify trans-modifying loci underlying crossover variation within the species. I performed Quantitative Trait Loci (QTL) mapping using a fluorescence-based crossover reporter system to measure recombination frequency in a genomic interval on chromosome 3, termed 420. Mapping in a Col-420 × Bur-0 F2 population revealed four major recombination QTLs (rQTLs) that influence crossover frequency. A novel recessive rQTL on chromosome 1 that reduced crossovers within the interval was fine-mapped to a premature stop codon in TATA Binding Protein (TBP)-associated factor 4b (TAF4b) in Bur-0 (taf4b-1). TAF4b is a subunit of the TFIID complex, a multi-protein general transcription factor complex comprising TBP and numerous TAFs that forms a component of the pre-initiation complex that recruits RNA polymerase II to promoters. Transformation-based complementation experiments and the isolation of several independent taf4b alleles provided genetic proof that TAF4b is essential for wild-type levels of crossover within 420. Analysis of the prevalence of the taf4b-1 mutation in the global Arabidopsis accession collection demonstrated its specificity to three accessions in the British Isles. A combination of cytology, genetic analysis using additional fluorescent reporter lines, and sequencing in F2 recombinant populations demonstrated a genome-wide reduction in crossover frequency in taf4b-1. In addition, RNA sequencing identified numerous transcriptional changes in taf4b-1. Both up- and down-regulated gene sets displayed significant enrichment for genes that are predominantly expressed in meiocytes, and several gene ontology terms pertaining to protein modification and meiotic processes. These results further demonstrate the existence of genetic modifiers of crossover frequency in natural populations of A. thaliana, and the characterisation of a novel trans-modifier of recombination, TAF4b. This signifies a novel function for TAF4b in Arabidopsis, and further enhances our understanding of the molecular factors controlling the frequency and distribution of meiotic crossovers in plants.

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Zhao, Shengjie. "Natural frequency based damage identification of beams using piezoelectric materials". ASME 2015 International Mechanical Engineering Congress and Exposition, 2015. http://hdl.handle.net/1993/31652.

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Following the studies of natural frequency based damage detection methods, an advanced technique for damage detection and localization in beam-type structures using a vibration characteristic tuning procedure is developed by an optimal design of piezoelectric materials. Piezoelectric sensors and actuators are mounted on the surface of the host beam to generate excitations for the tuning via a feedback process. The excitations induced by the piezoelectric effect are used to magnify the effect of the damage on the change of the natural frequencies of the damaged structure to realize the high detection sensitivity. Based on the vibration characteristic tuning procedure, a scan-tuning methodology for damage detection and localization is proposed. From analytical simulations, both crack and delamination damage in the beams are detected and located with over 20% change in the natural frequencies. Finite element method (FEM) simulations are conducted to verify the effectiveness of the proposed methodology.
October 2016

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Hall, Julie Maria. "Nature, frequency and natural history of intracranial cavernous malformations in adults". Thesis, University of Edinburgh, 2011. http://hdl.handle.net/1842/9532.

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Scottish Intracranial Vascular Malformation Study was the first prospective, population-based study of the major types of intracranial vascular malformations; arteriovenous, cavernous and venous malformations including dural fistulae and carotid-cavernous fistulae. It was based in Scotland and designed in 1998 by my supervisor Professor Charles Warlow and the first Research Fellow Dr Rustam Al-Shahi supported by the SIVMS steering committee (www.saivms.scot.nhs.uk). Recruitment and follow-up began in January 1999. Recruitment and follow-up of all vascular malformation types was done by Dr Al-Shahi until March 2002 and this role then transferred to me in April 2002 until I left in August 2004. The main duties of the Research Fellow were to collect and review all the clinical material of cases notified to SIVMS and arbitrate with the relevant expertise where there was doubt whether the case met the criteria for inclusion in SIVMS. Apart from my clinical responsibilities in recruitment and follow-up, the post also involved supervision of the part-time study administrator and also weekly meetings with the study programmer. I was also responsible for convening and presenting updates of the study progress weekly to my supervisor Professor Charles Warlow, biannually to the Study steering committee meetings, and annually to my funding body, the Stroke Association. This Research Fellowship also allowed me to gain an appreciation of the efforts needed to sustain collaborators’ interest in a long running study and I made presentations to improve the profile of the study on the national and international stage. For my duration as the SIVMS Research Fellow, I recruited and followed-up all types of newly diagnosed intracranial vascular malformations (IVMs). This thesis, however, is based solely on the incident intracranial cavernous malformations (ICMs) recruited to the study by both Dr Al-Shahi and myself between January 1999 and December 2003. The follow-up data in this thesis were that available to me on August 31st 2004. The data cleaning and the analysis for this thesis has been performed by me alone under the supervision of Professor Warlow. Although the core study design was well-established and tested prior to my involvement with SIVMS, I did divise new studies such as the Sensitivity and Specificity of MRI in the diagnosis of intracranial CMs. This cavernoma imaging study was a separate study designed, executed and analysed by myself, a medical student Sue Liong, the Cavernoma Imaging Study Group [appendix 1] with guidance from Professor Warlow, Dr Al-Shahi, Dr Andrew Farrall (consultant neuroradiologist) and Dr Steff Lewis (Medical Statistician). Computing support was provided by Aidan Hutchison (SIVMS programmer).

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Feng, Gaoyang. "Colour information in natural scenes : frequency of metamerism and colour gamut". Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/colour-information-in-natural-scenesfrequency-of-metamerism-and-colour-gamut(0987f4cf-b0e3-49f9-b6c0-cc79a0b8d1a5).html.

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Colour is an important source of information in the natural world. It can be used for distinguishing and identifying surfaces and objects and separating one region from another. For instance, flowers and grasses in a garden can be distinguished by their colours despite a change in illuminant. Intuitively, the identifiability of surfaces in a scene can be described by their volumes of colour gamuts. But is this approximation of the identifiability accurate? On the other hand, the existence of metamerism in natural scenes shows that colour is sometimes unreliable for surfaces identification. Estimating frequency of metamerism normally requires many comparisons between surface colours to determine their distinguishability under different illuminants. Is there a simpler approach to predict the frequency of metamerism in natural scenes? The aim of this thesis was to address these two questions about the identifiability of surfaces in natural scenes. To answer the first question, the volumes of colour gamuts were estimated over 50 natural scenes under different illuminants. The logarithm of the gamut volume was regressed on the differential entropy of colours. It was found that gamut volume can be an accurate approximation, given a colour difference threshold representing the visual distinguishability within an approximately perceptually uniform colour space. To answer the second question, the frequency of metamerism was estimated over 50 natural scenes with changes in illuminant; and predictive models were constructed based on different combinations of Shannon differential entropies of colours. There was strong dependence of the frequency of metamerism on the combination of the differential entropy and the conditional differential entropy of colours. It means that the frequency of metamerism can be predicted by the informational quantities of the colours in a scene.

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Ng, G. H. T. "Finite element model updating by using natural frequency and mode shape sensitivities". Thesis, Swansea University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.638321.

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Three finite element model updating approaches are considered in this thesis. In the first updating approach, a line search method is used in conjunction with the existing two level Gauss-Newton approach. This two level updating approach was used to tackle the problem of shape function discretization and enabled a coarse finite element model to be updated without discretization bias. The purpose of the line search method is to place the updated estimates, which are obtained at each iteration step of the Newton method, in a superior position for the next Newton iteration. Accordingly, convergence can be achieved with the use of line searching in some non-convergent problems. The effectiveness of this updating technique is illustrated by both simulated and experimental case studies. The second approach is concerned with reduction methods for use in finite element model updating. Particular attention is paid to the performance of dynamic condensation and modal truncation schemes. In both cases, subspace iteration and the efficient computation approaches which incorporate the skyline storage method are used in conjunction with the updating method. Moreover, an efficient method is proposed for the computation of eigenvector sensitivities in principal co-ordinates. Two simulated updating problems containing over one thousand degrees of freedom are examined for a variety of cases using different forms of sensitivity data. Another area of interest in the present thesis is the modelling and updating of adhesive, welded and bolted joints. In the case of the adhesive joint, two modelling approaches, referred to as the simplified 'element strip' model and the complex 'full joint' model are examined. For the updating of the welded joint, careful parameterization is found to be critical. The use of nodal offset dimensions is shown to result in an updated joint with physical meaning. When applied to the non-linear adhesive and bolted joints, model updating will produce equivalent linearized representations. The methods and their effectiveness for mechanical joint model updating are demonstrated by experimental case studies.

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Libros sobre el tema "Natural frequency"

Raynal Villaseñor, Jose A. Frequency Analyses of Natural Extreme Events. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-86390-6.

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Abbassian, F. Selected benchmarks for natural frequency analysis. East Kilbride,Glasgow: NAFEMS, 1987.

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Alberta. Energy Resources Conservation Board. Gas density measurement frequency (orifice meters). Calgary, Alta: Energy Resources Conservation Board, 1993.

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S, Lake Mark y Langley Research Center, eds. Natural frequency of uniform and optimized tetrahedral truss platforms. Hampton, VA: National Aeronautics and Space Administration, Langley Research Center, 1994.

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Nakagawara, Van B. Natural sunlight and its association to aviation accidents: Frequency and prevention. Washington, D.C: Federal Aviation Administration, Office of Aerospace Medicine, 2003.

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United States. National Bureau of Standards., ed. Time-domain system for identification of the natural resonant frequencies of aircraft relevant to electromagnetic compatibility testing. [Washington, D.C.]: U.S. Dept. of Commerce, National Bureau of Standards, 1988.

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United States. National Bureau of Standards, ed. Time-domain system for identificiation of the natural resonant frequencies of aircraft relevant to electromagnetic compatibility testing. [Washington, D.C.]: U.S. Dept. of Commerce, National Bureau of Standards, 1988.

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Asquith, William H. Regional equations for estimation of peak-streamflow frequency for natural basins in Texas. Austin, Tex: U.S. Dept. of the Interior, U.S. Geological Survey, 1997.

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Capítulos de libros sobre el tema "Natural frequency"

Weik, Martin H. "natural frequency". En Computer Science and Communications Dictionary, 1073. Boston, MA: Springer US, 2000. http://dx.doi.org/10.1007/1-4020-0613-6_12106.

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Rawer, Karl. "Natural (low frequency) emissions". En Wave Propagation in the Ionosphere, 377–86. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-017-3665-7_23.

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Jackson, Lionel E. "Frequency and Magnitude of Events". En Encyclopedia of Natural Hazards, 359–63. Dordrecht: Springer Netherlands, 2013. http://dx.doi.org/10.1007/978-1-4020-4399-4_147.

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Liu, Xue, Qing Shao, Tao Xu y Guikai Guo. "Natural Frequency Modification Using Frequency-Shift Combined Approximations Algorithm". En Recent Developments in Intelligent Systems and Interactive Applications, 86–91. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-49568-2_13.

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Radzi, M. R., M. H. Zawawi, W. N. Yusairah, A. Z. A. Mazlan, Aizat Abas y M. R. R. M. A. Zainol. "Natural Frequency Analysis for Hydropower Structure". En Water Resources Development and Management, 511–19. Singapore: Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-15-1971-0_51.

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Geisler, C. Daniel y Phillip J. Rossman. "Comparisons Between Actual and Simulated Responses of Auditory Nerve Fibers Excited by Natural Stop Consonant-Vowel Syllables". En Auditory Frequency Selectivity, 273–80. Boston, MA: Springer US, 1986. http://dx.doi.org/10.1007/978-1-4613-2247-4_30.

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Surkov, Vadim y Masashi Hayakawa. "Electromagnetic Effects Resulted from Natural Disasters". En Ultra and Extremely Low Frequency Electromagnetic Fields, 373–427. Tokyo: Springer Japan, 2014. http://dx.doi.org/10.1007/978-4-431-54367-1_10.

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Argamann, Vera y Neal J. Pearlmutter. "Lexical semantics as a basis for argument structure frequency biases". En Natural Language Processing, 303–24. Amsterdam: John Benjamins Publishing Company, 2002. http://dx.doi.org/10.1075/nlp.4.16arg.

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Copeland, G. J. M. "Low Frequency Ambient Noise – Generalised Spectra". En Natural Physical Sources of Underwater Sound, 17–30. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-1626-8_2.

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Carey, William M. y James W. Fitzgerald. "Low Frequency Noise from Breaking Waves". En Natural Physical Sources of Underwater Sound, 277–304. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-1626-8_22.

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Actas de conferencias sobre el tema "Natural frequency"

Tjandra, Sugih S. y S. R. Pudjaprasetya. "Natural frequency of regular basins". En 4TH INTERNATIONAL CONFERENCE ON MATHEMATICS AND NATURAL SCIENCES (ICMNS 2012): Science for Health, Food and Sustainable Energy. AIP Publishing LLC, 2014. http://dx.doi.org/10.1063/1.4868844.

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Zhao, Yue y Shao-feng Huang. "Analysis on natural main frequency". En 2011 IEEE International Conference on Advanced Power System Automation and Protection (APAP). IEEE, 2011. http://dx.doi.org/10.1109/apap.2011.6180771.

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Saijo, O. y H. Eto. "Natural Frequency Analysis of Elastic Plate". En ASME 1997 Turbo Asia Conference. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/97-aa-099.

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Large scale floating structures, such as floating airport and amusement park having two dimensional expanse in horizontal direction, which structural concept can be considered as plate-type structural system. This structural system has a great deal of potential to be applied to oceanic structures like a artificial ground. This practical fabrication will be done by a combination of units. The hydroelastic interaction problem and structural design have attracted the attention of researchers and structural engineers. This paper presents consideration and conclusion through the numerical calculation results of the natural frequency studied under the various supporting conditions by developed computer program. The theoretical development is obtained by a way of combination of finite element method (FEM) and boundary integral equation method (BIEM). As to natural frequency analysis of oceanic structures based on the fluid-structure interaction, in general, there is an assumption to make it possible by estimating properly the added mass of the structure surrounding by water. The added mass of floating plate obtained by BIEM is modified and transformed into mass matrix of plate in FEM analysis. Herein, FEM analysis is based on the bending vibration assumption.

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Grant, K. B. y A. Saigal. "Natural Frequency Response of Intraaortic Balloons". En ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-11455.

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An Intraaortic Balloon (IAB) is a cardiac assist device that consists of a catheter (lumen) and a balloon at the catheter’s distal end. A balloon pump, or IABP, and a transducer are connected to the hub of the catheter that remains outside of the body. Connecting the inner lumen to the balloon pump through the hub of the catheter is typically used to monitor pressures within the human body and can be characterized as a catheter-transducer system. The three main components of this system and their functions are as follows: the IAB gives access to the blood pressure system through the inner lumen; a transducer converts a mechanical impulse of a pressure wave into an electrical signal; the IABP records the electrical signals for the pump operator’s and pump’s interpretation. The pump analyzes the incoming electrical signal and, in turn, triggers the appropriate IAB inflate and deflate times. Catheter-transducer systems can be modeled as underdamped, second-order dynamic systems. Each system has both a characteristic frequency and a damping coefficient, where damping refers to the accuracy of the monitoring set-up to reproduce pressure waveform characteristics. To achieve an accurate pressure reading, optimal damping must be achieved. If the system is underdamped, very little damping in the system, the pressure readings tend to overestimate the systolic blood pressure and underestimate the diastolic blood pressure, and vice versa. The ability for the pressure monitoring system to detect changes quickly is called the frequency response. Catheter-transducer systems are characterized as underdamped because the addition of damping causes the response of the system to decrease. In order to counteract this, the system must have a high natural or undamped frequency — the frequency that would occur in the absence of frictional forces or damping. A high natural frequency will reduce the effects of damping such that underdamped or overdamped waveforms are unlikely to appear. This study compares the natural frequency and damping coefficients of four different IABs: Datascope Fidelity, Arrow Nitinol, Arrow Stainless Steel and Arrow Polyimide. Each of these IABs had a natural frequency greater than the minimum specified value of 20 Hz. The Arrow Polymide inner lumen had the lowest natural frequency response. This is due to the flexibility of the Polyimide, which absorbs some of the pressure wave’s energy, and thus distorts the pressure wave output. Likewise, the Arrow Nitinol, with the stiffest inner lumen, had the highest natural frequency. The damping coefficients for these IABs varied from 0.16 to 0.38. None of the four IABs achieved an average damping coefficient near the optimal range of 0.60 to 0.75 and thus all of them can be characterized as underdamped systems.

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Kusters, J. A. y G. S. Kaitz. "Characteristics of Natural, Swept Natural, and Cultured X- and Z-Growth Quartz Material in High Temperature, High Stress Applications". En 39th Annual Symposium on Frequency Control. IEEE, 1985. http://dx.doi.org/10.1109/freq.1985.200848.

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Jeong, So-Hee y Joon-Ho Lee. "Natural frequency based recursive radar detection in frequency domain". En 2019 International Conference on Information and Communication Technology Convergence (ICTC). IEEE, 2019. http://dx.doi.org/10.1109/ictc46691.2019.8939823.

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Amini, Rouzbeh, Grant Warner y Hamid Nayeb-Hashemi. "Natural Frequency Analysis of Liquid-Filled Tanks". En ASME 2005 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/detc2005-84856.

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Traditionally, the cantilever modal shape of liquid-filled tanks has been considered as the most critical mode. However, recent research has demonstrated that natural frequencies associated with some circumferential modes might be close to the frequency of earthquake excitation. This can lead to a resonance phenomenon, and consequently failure of the tanks. In this paper, we perform Natural Frequency Analysis of fluid-filled tanks, using finite element analysis. Modeling and solution employ ADINA potential-based flow elements, which require the assumption of inviscid, irrotational and incompressible flow. The problem is solved for different geometries and water levels of tanks; the results are compared with the current results in the literature and the difference is demonstrated.

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Hobatho, M. C., R. Darmana, J. J. Barrau, S. Laroze y J. P. Morucci. "Natural frequency analysis of a human tibia". En Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE, 1988. http://dx.doi.org/10.1109/iembs.1988.94933.

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Fish, Garron, Mike Dempsey, Juan Gabriel Delgado y Neil Roberts. "Natural frequency analysis of Modelica powertrain models". En 9th International MODELICA Conference, Munich, Germany. Linköping University Electronic Press, 2012. http://dx.doi.org/10.3384/ecp12076697.

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Petro, Samer H., Don Reynolds, Shen EnChen y Hota V. S. GangaRao. "Measurement of axial forces via natural frequency". En Non-Destructive Evaluation Techniques for Aging Infrastructure & Manufacturing, editado por Ronald D. Medlock y David C. Laffrey. SPIE, 1998. http://dx.doi.org/10.1117/12.300128.

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Informes sobre el tema "Natural frequency"

Brooks, Dusty, Austin Glover y Brian Ehrhart. Compressed Natural Gas Component Leak Frequency Estimation. Office of Scientific and Technical Information (OSTI), octubre de 2022. http://dx.doi.org/10.2172/1892133.

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Stephen, Ralph A. High Frequency Bottom Interaction Acoustics in the Atlantic Natural Laboratory. Fort Belvoir, VA: Defense Technical Information Center, septiembre de 1997. http://dx.doi.org/10.21236/ada628683.

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Levin, Todd. Prices in Frequency Regulation Markets: Impacts of Natural Gas Prices and Variable Renewable Energy. Office of Scientific and Technical Information (OSTI), mayo de 2018. http://dx.doi.org/10.2172/1988752.

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Hall, Zanker y Kelner. PR-343-06605-R02 USM Recalibration Frequency. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), agosto de 2009. http://dx.doi.org/10.55274/r0010155.

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This program is intended to improve the understanding of the stability over time of gas multi-path ultrasonic flow meters (USMs). Within the Natural Gas Industry, there are currently on universal standards requiring periodic recalibration of USMs. Removing these flow meters from serviced for recalibration is costly and inconvenient. However, the primary reason that a recalibration standard does not exist is the lack of definitive data regarding the long-term stability of installed USMs. In order to address this situation, collection and analysis of data was performed to help formulate a recalibration guideline. Specific tasks include: (1) review and utilization of existing published technical papers, (2) working with certified flow calibration facilities to obtain data, (3) obtaining data from USM manufactures on changing of electronics and/or transducers, (4) obtaining historical recalibration data, and (5) participation in selected recalibrations by PRCI member companies.

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Alden, Caroline y Gregory Rieker. Emission Inventories from Natural Gas Storage Facilities using Regional Frequency Comb Laser Monitoring and Aircraft Flyovers (Final Report). Office of Scientific and Technical Information (OSTI), marzo de 2021. http://dx.doi.org/10.2172/1771938.

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Kuchler, Fred, Megan Sweitzer y Carolyn Chelius. prevalence of the "natural" claim on food product packaging. Washington, D.C.: USDA Economic Research Service, mayo de 2023. http://dx.doi.org/10.32747/2023.8023700.ers.

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U.S. food suppliers make claims about their production processes on food packaging that highlight attributes some consumers want while charging a higher price than for unlabeled products. Some labels use such claims as "USDA Organic" and "raised without antibiotics," which require different and more expensive production techniques than conventional agriculture. However, food suppliers can use the label that claims the food is "natural" at a relatively low cost because regulatory agencies treat the claim as meaning nothing artificial was added and the product was minimally processed. Numerous consumer food choice studies concluded that consumers equate the natural label on food with healthier food choices and more costly production practices that signify environmental stewardship. Informed by these previous studies' findings, the authors of this report estimate the frequency with which food suppliers make the natural claim on food packaging labels. Estimates are based on scanner data and comprehensive label data. Across all foods in 2018, 16.3 percent of retail food expenditures and 16.9 percent of all items purchased (unit sales) were for foods labeled natural, whereas 11.0 percent of Universal Product Codes (UPC) in stores were labeled natural on the packaging. Expenditures for food labeled natural were larger than expenditures for foods labeled USDA Organic. Natural labels were found predominately on processed products. For example, 95.6 percent of expenditures for vitamins and meal supplements were for products labeled natural, compared with 0.5 percent of expenditures for potatoes

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George y Hawley. PR-015-12600-R01 Ability of Ultrasonic Meters to Measure Accurately in Compressor-Induced Pulsating Flows. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), noviembre de 2013. http://dx.doi.org/10.55274/r0010808.

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Transmission and storage operations frequently move natural gas using reciprocating compressors that may generate flow pulsations. Most measurement systems cannot accurately measure the flow rate of a pulsating gas stream, and the resulting errors can cause inaccurate gas volumes and accounting imbalances. Recent advances in ultrasonic meters may provide the ability to function without measurement error in pulsating gas streams. Tests were performed to examine the relationship between ultrasonic meter transducer sampling rates, the frequency and amplitude of pulsations from reciprocating compressors, and meter accuracy as a possible basis for using ultrasonic meters in gas pipelines with varying pulsations. Two ultrasonic natural gas meters of current design were tested at SwRI in flows that simulated reciprocating compressor pulsations. Diagnostics and flow data were collected from the meters and analyzed to identify pulsation conditions in which the meters read accurately, or in which meter data could be used to correct measurement errors.

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Young, Craig. Problematic plant monitoring in Pea Ridge National Military Park: 2006–2021. Editado por Tani Hubbard. National Park Service, junio de 2022. http://dx.doi.org/10.36967/nrr-2293656.

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Managers are challenged with the impact of problematic plants, including exotic, invasive, and pest plant species. Information on the cover and frequency of these plant species is essential for developing risk-based approaches to managing them. Based on surveys conducted in 2006, 2013, 2018, and 2021, Heartland Inventory and Monitoring Network staff and contractors identified a cumulative total of 38 potentially problematic plant species in Pea Ridge National Military Park. Of the 35 species found in 2021, we characterized 13 as very low frequency, 9 as low frequency, 9 as medium frequency, and 4 as high frequency. Of these 35 species, midpoint cover estimates of 4 medium frequency and all 4 high frequency species exceeded the 10-acre threshold. The 10-acre threshold represents a limit beyond which eradication of a problematic plant species is likely not possible. Clearing of eastern redcedar (Juniperus virginiana) continues to be evident in our observations, and sericea lespedeza (Lespedeza cuneata) appears to have increased as clearing progressed. The rapid increase in Japanese stiltgrass (Microstegium vimineum) appears to be parkwide. Because of the number, extent, and cover of problematic plants in the park, control efforts should focus on early detection treatments and strategic treatment of high priority, widespread species to protect features of the park’s natural and cultural landscapes. High priority species may include plant species capable of rapid spread, species at low population levels, and species that can be effectively controlled.

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Wilcox y White. PO-316-10207-R01 Design Guideline for Small Diameter Branch Connections. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), marzo de 2011. http://dx.doi.org/10.55274/r0010738.

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In all industrial applications, vibration of piping components is a concern that is often addressed during the piping design phase. Effort is made to predict and avoid the mechanical natural frequency of large piping in order to prevent fatigue failures. However, small diameter branch connections are often overlooked. These connections are just as susceptible to fatigue failures due to high vibration as large piping is; therefore, the design of the small piping must also be considered. Current piping standards only place high level requirements on the design of small diameter branch connections and do not provide many recommendations related to the design of the connections. This guideline was developed in order to reduce the effort required to properly design small diameter branch connections. The guideline provides recommendations on the weight placed on the branch and the length of the connection in order to minimize the possibility of fatigue failure. The geometries provided in the guideline were based on natural frequency avoidance and consider the machine the branch is operating near, where the branch is placed in reference to the machine, frequency of excitation (operating speed of machine), and the geometry of the branch. The guideline does not attempt to predict actual vibration amplitudes on the branches. This guideline can be applied for any branch connection that has a nominal diameter less than two inches and a branch pipe to main pipe ratio of less than 25%.

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Hudgens, Bian, Jene Michaud, Megan Ross, Pamela Scheffler, Anne Brasher, Megan Donahue, Alan Friedlander et al. Natural resource condition assessment: Puʻuhonua o Hōnaunau National Historical Park. National Park Service, septiembre de 2022. http://dx.doi.org/10.36967/2293943.

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Natural Resource Condition Assessments (NRCAs) evaluate current conditions of natural resources and resource indicators in national park units (parks). NRCAs are meant to complement—not replace—traditional issue- and threat-based resource assessments. NRCAs employ a multi-disciplinary, hierarchical framework within which reference conditions for natural resource indicators are developed for comparison against current conditions. NRCAs do not set management targets for study indicators, and reference conditions are not necessarily ideal or target conditions. The goal of a NRCA is to deliver science-based information that will assist park managers in their efforts to describe and quantify a park’s desired resource conditions and management targets, and inform management practices related to natural resource stewardship. The resources and indicators emphasized in a given NRCA depend on the park’s resource setting, status of resource stewardship planning and science in identifying high-priority indicators, and availability of data and expertise to assess current conditions for a variety of potential study resources and indicators. Puʻuhonua o Hōnaunau National Historical Park (hereafter Puʻuhonua o Hōnaunau NHP) encompasses 1.7 km2 (0.7 mi2) at the base of the Mauna Loa Volcano on the Kona coast of the island of Hawaiʻi. The Kona coast of Hawaiʻi Island is characterized by calm winds that increase in the late morning to evening hours, especially in the summer when there is also a high frequency of late afternoon or early evening showers. The climate is mild, with mean high temperature of 26.2° C (79.2° F) and a mean low temperature of 16.6° C (61.9° F) and receiving on average 66 cm (26 in) of rainfall per year. The Kona coast is the only region in Hawaiʻi where more precipitation falls in the summer than in the winter. There is limited surface water runoff or stream development at Puʻuhonua o Hōnaunau NHP due to the relatively recent lava flows (less than 1,500 years old) overlaying much of the park. Kiʻilae Stream is the only watercourse within the park. Kiʻilae Stream is ephemeral, with occasional flows and a poorly characterized channel within the park. A stream gauge was located uphill from the park, but no measurements have been taken since 1982. Floods in Kiʻilae Stream do occur, resulting in transport of fluvial sediment to the ocean, but there are no data documenting this phenomenon. There are a small number of naturally occurring anchialine pools occupying cracks and small depressions in the lava flows, including the Royal Fishponds; an anchialine pool modified for the purpose of holding fish. Although the park’s legal boundaries end at the high tide mark, the sense of place, story, and visitor experience would be completely different without the marine waters adjacent to the park. Six resource elements were chosen for evaluation: air and night sky, water-related processes, terrestrial vegetation, vertebrates, anchialine pools, and marine resources. Resource conditions were determined through reviewing existing literature, meta-analysis, and where appropriate, analysis of unpublished short- and long-term datasets. However, in a number of cases, data were unavailable or insufficient to either establish a quantitative reference condition or conduct a formal statistical comparison of the status of a resource within the park to a quantitative reference condition. In those cases, data gaps are noted, and comparisons were made based on qualitative descriptions. Overall, the condition of natural resources within Puʻuhonua o Hōnaunau NHP reflects the surrounding landscape. The coastal lands immediately surrounding Puʻuhonua o Hōnaunau NHP are zoned for conservation, while adjacent lands away from the coast are agricultural. The condition of most natural resources at Puʻuhonua o Hōnaunau NHP reflect the overall condition of ecological communities on the west Hawai‘i coast. Although little of the park’s vegetation...

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