Relevant bibliographies by topics / Directional impulse response

Contents

  1. Journal articles
  2. Dissertations / Theses
  3. Book chapters
  4. Conference papers

Academic literature on the topic 'Directional impulse response'

Author: Grafiati
Published: 4 June 2021
Last updated: 13 February 2022

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Journal articles on the topic "Directional impulse response"

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Glantz, R. M., C. Wyatt, and H. Mahncke. "Directionally selective motion detection in the sustaining fibers of the crayfish optic nerve: linear and nonlinear mechanisms." Journal of Neurophysiology 74, no. 1 (July 1, 1995): 142–52. http://dx.doi.org/10.1152/jn.1995.74.1.142.

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1. Directional selectivity of crayfish sustaining fibers was examined with drifting sine wave gratings and with intracellular and extracellular recordings. Directionality was measured for variations in stimulus contrast, spatial frequency, and temporal frequency. 2. Sustaining fibers exhibit directional selectivity in the magnitude of the compound postsynaptic potential (PSP), the impulse frequency modulation response, and the mean firing rate. The mean synaptic potential is insensitive to direction. The directionality of the mean impulse rate appears to arise by rectification in the voltage-to-impulse transduction. 3. The preferred directions of three identified sustaining fibers are similar to those of head-down optomotor neurons to which these sustaining fibers project. 4. The modulatory response, elicited by gratings drifting in the preferred direction, increased linearly with contrast until saturation (typically at a contrast of 0.5), where maximum directional selectivity obtains. 5. The magnitude of the directional response is a band-pass function of spatial and temporal frequency and exhibits reversal of directionality (i.e., aliasing) at high spatial and temporal frequencies. The results imply a spatial sampling interval of 4.5 degrees and a temperature-dependent inhibitory delay of 40-90 ms. The PSP modulation response shares several features with that of neighboring tangential (Tan1) neurons. 6. A qualitative model is proposed for the transformation of a phase-sensitive, linear directional response to a phase-insensitive and nonlinear time-averaged response, based on the functional connections from Tan1 neurons to sustaining fibers to optomotor neurons. The model includes a threshold rectification, a synaptic band-pass filter, and differences in temporal phase among converging modulatory signals.
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Dai, Quanqi, Inhyuk Park, and Ryan L. Harne. "Impulsive energy conversion with magnetically coupled nonlinear energy harvesting systems." Journal of Intelligent Material Systems and Structures 29, no. 11 (April 23, 2018): 2374–91. http://dx.doi.org/10.1177/1045389x18770860.

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Magnets have received broad attention for vibration energy harvesting due to noncontact, nonlinear forces that may be leveraged among harvesting system elements. Yet, opportunities to integrate multi-directional coupling among a nonlinear energy harvesting system subjected to impulsive excitations have not been scrutinized, despite widespread prevalence of such excitations. To characterize these potentials, this research investigates an energy harvesting system with magnetically induced nonlinearities and coupling effects under impulsive excitations. A system model is formulated and validated with experimental efforts to reconstruct static and dynamic properties of the system via simulations. Then, the model is harnessed to scrutinize dynamic response of the system when subjected to impulse conditions. This research reveals the clear impulse strength dependence and influence of asymmetries on total electrical energy capture and energy conversion efficiency that are tailored by magnetic force coupling. Asymmetry is found to promote greater impulse-to-electrical energy conversion when compared to the symmetric counterpart system and a benchmark nonlinear energy harvester. The roles of initial conditions exemplify how stored energy in an asymmetric energy harvesting system may be released during nonlinear impulsive response. These results provide insights about opportunities and challenges to incorporate magnetic coupling effects in nonlinear energy harvesting systems subjected to impulses.
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Papadakis, Nikolaos, and Georgios Stavroulakis. "Low Cost Omnidirectional Sound Source Utilizing a Common Directional Loudspeaker for Impulse Response Measurements." Applied Sciences 8, no. 9 (September 19, 2018): 1703. http://dx.doi.org/10.3390/app8091703.

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Alternative low-cost sources (e.g., balloons, gun fires) are used for impulse response measurements when a dodecahedron speaker is not available. This study sets to explore the applicability of a method utilizing a common directional loudspeaker as a sound source. For this purpose measurements were performed in three spaces with three different common directional loudspeakers. Different placements of the loudspeakers were performed (twelve positions similar to the twelve positions of the faces of a dodecahedron speaker, different rotations of the loudspeakers for a total sum of twenty six and fourteen positions). The impulse responses obtained were added up creating a single impulse response for each case. Comparisons of the acoustic parameters measured with the proposed method and with a dodecahedron speaker are presented and suggest the expected mean absolute error and standard deviation for similar measurements. Reverberation time measurements show a mean absolute error of less than 0.08 s, as compared with measurements with a dodecahedron speaker. The proposed method can be the primary method for measuring impulse responses when a dodecahedron speaker is not available. Suggested improvements may lead to better omnidirectionality as compared with a dodecahedron loudspeaker, and set the method applicable to be utilized for auralization purposes.
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Spiousas, Ignacio, and Manuel C. Eguia. "Directional impulse response of a large cavity inside a sonic crystal." Journal of the Acoustical Society of America 132, no. 4 (October 2012): 2842–51. http://dx.doi.org/10.1121/1.4744946.

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Esplin, J. James, Brian T. Thornock, and Timothy W. Leishman. "The effects of nonideal microphone directivity patterns on directional impulse response measurements." Journal of the Acoustical Society of America 126, no. 4 (2009): 2287. http://dx.doi.org/10.1121/1.3249376.

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Oldham, D. J., and L. El-Zeky. "A Computer Investigation of the Performance of Virtual Reflectors: Part II — The Effects of Room Conditions." Building Acoustics 7, no. 2 (June 2000): 151–60. http://dx.doi.org/10.1260/1351010001501561.

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In a companion paper [1] a technique for overcoming acoustic problems resulting from the directional nature of human speech in open stage auditoria by means of virtual reflectors has been proposed. In a following paper [2] the system was applied to a computer model of an open stage auditorium in which there was no background noise and the space was relatively dead. In the current paper the action of the virtual reflector has been systematically investigated in more realistic conditions. It is shown to be capable of functioning in conditions which are more reverberant and in conditions in which background noise is present. In all cases investigated the action of a virtual reflector results in conditions to the rear of the primary source (human speaker) being improved such that they become comparable to conditions at equivalent positions to the front. It has been shown that the STI at the rear of a human speaker in an open stage auditorium with the virtual reflector system in operation does not increase significantly with increasing gain [2]. This is due to the Modulation Transfer Function (MTF's) being determined by the convolution of two impulse responses multiplied by a gain factor and added to a third impulse response. The resulting impulse response will therefore consists of many ‘reflections’ and hence the MTF's (and the STI values that they determine) will be adversely affected. An attempt was made to reduce the number of ‘reflections’ in the resultant impulse response by the use of a super directional microphone in order to improve the MTF's and thus the STI values. The actual improvement observed was very small and hence it would appear that the use of a super directional microphone is not particularly effective in this context.
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Lim, Hansol, Muhammad Imran, and Jin Yong Jeon. "A new approach for acoustic visualization using directional impulse response in room acoustics." Building and Environment 98 (March 2016): 150–57. http://dx.doi.org/10.1016/j.buildenv.2016.01.007.

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Zaunschirm, Markus, Franck Zagala, and Franz Zotter. "Auralization of High-Order Directional Sources from First-Order RIR Measurements." Applied Sciences 10, no. 11 (May 28, 2020): 3747. http://dx.doi.org/10.3390/app10113747.

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Can auralization of a highly directional source in a room succeed if it employs a room impulse response (RIR) measurement or simulation relying on a first-order directional source, only? This contribution presents model and evaluation of a source-and-receiver-directional Ambisonics RIR capture and processing approach (SRD ARIR) based on a small set of responses from a first-order source to a first-order receiver. To enhance the directional resolution, we extend the Ambisonic spatial decomposition method (ASDM) to upscale the first-order resolution of both source and receiver to higher orders. To evaluate the method, a listening experiment was conducted based on first-order SRD-ARIR measurements, into which the higher-order directivity of icosahedral loudspeaker’s (IKO) was inserted as directional source of well-studied perceptual effects. The results show how the proposed method performs and compares to alternative rendering methods based on measurements taken in the same acoustic environment, e.g., multiple-orientation binaural room impulse responses (MOBRIRs) from the physical IKO to the KU-100 dummy head, or higher-order SRD ARIRs from IKO to em32 Eigenmike. For optimal externalization, our experiments exploit the benefits of virtual reality, using a highly realistic visualization on head-mounted-display, and a user interface to report localization by placing interactive visual objects in the virtual space.
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Oldham, D. J., and L. El-Zeky. "A Computer Investigation of the Performance of Virtual Reflectors: Part 1 - Development of the Method." Building Acoustics 7, no. 1 (March 2000): 57–74. http://dx.doi.org/10.1260/1351010001501507.

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In a companion paper [1] a technique for improving acoustic conditions in open stage auditoria by means of virtual reflectors has been proposed. Possible methods of testing the application of a virtual reflector system were discussed and it was concluded that computer simulation was the most appropriate. However, before employing a commercially available package it was necessary to devise suitable procedures. The need for both a directional loudspeaker and a directional microphone is an essential requirement for the virtual reflector system but most computer simulation packages only allow for source directivity. Hence a method of incorporating the effect of microphone directivity using the principle of reciprocity was developed. The basis of establishing the gain factor has been devised and it is proposed that the convolution of echograms rather than the convolution of true impulse responses can be employed to predict system performance. The action of the virtual reflector system has been investigated using a model of an open stage theatre. Both system microphone and system loudspeaker were selected from a catalogue of available modern commercial sound equipment. The resulting STI contours demonstrated that the effect of the virtual reflector over the audience area to the rear of a human speaker was to raise the speech intelligibility to be approximately equal to that to the front of the speaker. It has been shown that the STI at the rear of a speaker with the virtual reflector system in operation does not increase significantly with gain. This is due to the Modulation Transfer Functions which determine the STI value being determined by the convolution of two impulse responses multiplied by a gain factor and added to a third impulse response. The resulting impulse response therefore consists of many ‘reflections’ and hence the MTF's and STI values will be adversely affected if excess gain is applied.
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Handayani, Puji, and Gamantyo Hendrantoro. "A Model of Double-Directional Indoor Channels for Multiterminal Communications." International Journal of Antennas and Propagation 2013 (2013): 1–18. http://dx.doi.org/10.1155/2013/384173.

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We propose a model of double-directional indoor nonline of sight (NLOS) channels for multiterminal communications. We derive a simple channel matrix that describes input-output relationship for such channels. The multiterminal systems may consist of several terminals that act as amplify-and-forward (AF) relays, where source, relays, and destination have arbitrary numbers of antennas. We complete our model by characterizing the parameters of double-directional channel impulse response of such channels through measurements in indoor environment using 3D synthetic array antenna at 2.5 GHz band. To find out the relation between spatial characteristic of channels in each hop, we observe the direction of arrival (DOA) and direction of departure (DOD) of multipath component signals at the terminal that acts as relay. We find that there are several closely matched azimuths of DOAs and azimuths of DODs which follow uniform distribution in the range of −180° to 180° for elevation around the broadside direction of vertical omnidirectional elements of arrays.
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Dissertations / Theses on the topic "Directional impulse response"

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Thornock, Brian Trevor. "Comparison and Development of Methods for Measuring Directional Sound Arrivals in Rooms /." Diss., CLICK HERE for online access, 2009. http://contentdm.lib.byu.edu/ETD/image/etd3183.pdf.

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Book chapters on the topic "Directional impulse response"

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Tamura, Yasutaka, and Takao Akatsuka. "An Echolocation and Imaging Using Transducers of Directionally Distinguishable Impulse Response." In Acoustical Imaging, 73–82. Boston, MA: Springer US, 1991. http://dx.doi.org/10.1007/978-1-4615-3692-5_9.

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Gylych, Jelilov, Abdullahi Ahmad Jibrin, Bilal Celik, and Abdurrahman Isik. "Impact of Oil Price Fluctuation on the Economy of Nigeria, the Core Analysis for Energy Producing Countries." In Energy Management Systems in Process Industries - Current Practice and Challenges in Era of Industry 4.0 [Working Title]. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.94055.

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The study aims to find the short-run empirical analyses of the impact of oil price fluctuation on the monetary instrument (Exchange rate, Inflation, Interest rate) in Nigeria. We explored the frequently used Toda–Yamamoto model (TY) model, by adopting the TY Modified Wald (MWALD) test approach to causality, Forecast Error Variance Decomposition (FEVD) and Impulse Response Functions (IRFs).The study covered the period 1995 to 2018 (monthly basis), and our findings from MWALD test indicated that there is a uni-directional causality of the log of oil price (lnoilpr) to log of the exchange rate (lnexchr) at 10% level of significance, also there is a contemporaneous response of log of consumer price index (lncpi) to log of exchange rate (lnexchr) and log of interest rate (lnintr), and jointly (lnoilpr, lncpi and lnintr) granger cause lncpi. Also at 5% level of significance lnintr responded due to positive change in lnoilpr and lnexchr, and jointly causes lnintr at 5% level of significance. This is complimented with our findings in FEVDs, and IRFs. The empirical analyses shows that oil price is a strong determining factor of exchange rate, cost of borrowing and directly influences inflationary or deflationary tendencies in Nigeria..
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"Data, Preliminary Results, and Discussion 1." In Post-Keynesian Empirical Research and the Debate on Financial Market Development, 158–79. IGI Global, 2014. http://dx.doi.org/10.4018/978-1-4666-6018-2.ch007.

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In this chapter, various data sources used are combined into one common database for this study. Methods of adjustments and generating suitable data frequency are discussed. The chapter also presents an overview of quantitative measures of indicators of financial development and other macroeconomic variables. The chapter in particular offers direction on key sector-wide indicators inducing definitions and measurements of these variables. As the pre-requisite of vector autoregression model and impulse response analysis, integer order of integration of all variables are checked. Cointegration is examined in the model, and causality, among variables, is verified later in the chapter.
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Özbay, Ferhat, and Ceren Pehlivan. "Relationship Between the Use of Renewable Energy, Carbon Dioxide Emission, and Economic Growth." In Advances in Environmental Engineering and Green Technologies, 339–55. IGI Global, 2021. http://dx.doi.org/10.4018/978-1-7998-8335-7.ch020.

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The study aims to examine the relationship between the use of renewable energy, CO2, and GDP per capita. In this study that has been carried out on Turkey for the period 1990-2018, time series analysis is used. The long-term relationship between variables is revealed by the cointegration test. The periodic changes of the variables are examined by the variance decomposition and impulse-response function. Finally, with the causality test, the relationship between variables and the direction of this relationship are revealed. Findings show that there is a cointegrated relationship between the variables.. According to variance decomposition in the period of 10 lags, the renewable energy variance is 96% due to itself, 2.74% to CO2, and 0.50% to shocks in per capita GDP. As for impact-response functions, while the response of renewable energy to the GDP per capita variable is negative in the first two periods, it increase slightly in the following period, and after the sixth period, the effect of the shock diminished.
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Çavuşoğlu, Tarkan, and Debi Konukçu Önal. "A Panel VAR Analysis of the Shadow Economy in Europe and MENA." In Handbook of Research on Public Finance in Europe and the MENA Region, 201–20. IGI Global, 2016. http://dx.doi.org/10.4018/978-1-5225-0053-7.ch010.

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The objective of this chapter is to analyze empirically the potential dynamics of the relationship among the size of the shadow economy, fiscal burden and the official economy. The empirical analysis is based on the size estimates of the shadow economy in 17 developed and 11 transition economies of Europe for the period 1999-2013 and in 16 economies of Middle East and North Africa for the period 1999-2007. Direction of causal relations among shadow and official economies and the fiscal burden is investigated by exploiting the panel vector auto-regression approach and the associated impulse response analysis, which directly account for the potential endogeneity of the variables of interest. Findings mostly confirm the view that shadow and official economies are substitutes, and the dynamic effects of fiscal burden on the shadow economy are not as strong and clear as expected in the regions in question.
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Venkatesan, Srinivasan. "An Overview of Mindfulness and Its Implications for Children and Adolescents." In Handbook of Research on Clinical Applications of Meditation and Mindfulness-Based Interventions in Mental Health, 15–34. IGI Global, 2022. http://dx.doi.org/10.4018/978-1-7998-8682-2.ch002.

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Mindfulness is focusing on the present moment while calmly acknowledging and accepting one's thoughts, feelings, and body sensations as they are. The use of mindfulness practices on children and adolescents is burgeoning. This chapter covers the meaning and elements of mindfulness, their measurement, the various techniques, and exercises exclusive for children. Such techniques are typically individualized, tailor-made, personalized, contextualized, play-based, activity-oriented, reward-oriented, and maintained at the child's developmental level. Mindfulness parenting is vital. A mindful parent is aware of one's thoughts and feelings; is responsive to the child's needs, thoughts, and feelings; is better at regulating own emotions; is less critical of oneself or the child; is better at standing back from situations and avoiding an impulsive reaction. Issues related to professionalism, formal institutions for training mindfulness, and ongoing research on this theme, their achievements, and setbacks are listed before providing future directions for work in this area.
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Milic, Ljiljana. "Lth-Band Digital Filters." In Multirate Filtering for Digital Signal Processing, 206–41. IGI Global, 2009. http://dx.doi.org/10.4018/978-1-60566-178-0.ch007.

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Digital Lth-band FIR and IIR filters are the special classes of digital filters, which are of particular interest both in single-rate and multirate signal processing. The common characteristic of Lth-band lowpass filters is that the 6 dB (or 3 dB) cutoff angular frequency is located at p/L, and the transition band is approximately symmetric around this frequency. In time domain, the impulse response of an Lth-band digital filter has zero valued samples at the multiples of L samples counted away from the central sample to the right and left directions. Actually, an Lth-band filter has the zero crossings at the regular distance of L samples thus satisfying the so-called zero intersymbol interference property. Sometimes the Lthband filters are called the Nyquist filters. The important benefit in applying Lth band FIR and IIR filters is the efficient implementation, particularly in the case L = 2 when every second coefficient in the transfer function is zero valued. Due to the zero intersymbol interference property, the Lth-band filters are very important for digital communication transmission systems. Another application is the construction of Hilbert transformers, which are used to generate the analytical signals. The Lth-band filters are also used as prototypes in constructing critically sampled multichannel filter banks. They are very popular in the sampling rate alteration systems as well, where they are used as decimation and interpolation filters in single-stage and multistage systems. This chapter starts with the linear-phase Lth-band FIR filters. We introduce the main definitions and present by means of examples the efficient polyphase implementation of the Lth-band FIR filters. We discuss the properties of the separable (factorizable) linear-phase FIR filter transfer function, and construct the minimum-phase and the maximum-phase FIR transfer functions. In sequel, we present the design and efficient implementation of the halfband FIR filters (L = 2). The class of IIR Lth-band and halfband filters is presented next. Particular attention is addressed to the design and implementation of IIR halfband filters. Chapter concludes with several MATLAB exercises for self study.
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Conference papers on the topic "Directional impulse response"

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Banerjee, Arnab, Avishek Chanda, and Raj Das. "A Simplified Exact Compliance Normal-Directional Contact Model." In ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-66492.

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Contact is the most abundant phenomena in the field of multi-body dynamics, experienced when two or more bodies come in close vicinity to each other. During contact, one body virtually penetrates within other and therefore is subjected to a large impulsive force due to the deformation; this is the essence of the compliance based models. Subsequently, different compliance models were proposed, each having a different formulation for the impulsive force variation, which is always a function of time and deformation. A novel multi-linear compliance model, calculated on the basis of the Poisson’s law, is introduced in this work. The responses of all the available compliance models have been critically reviewed in previous studies and using the same study and the observed significant models, a comparative study is presented in this work for establishing the proposed model. A few significant models were selected according to the minimum amount of error induced by each while estimating the coefficient of restitution, impulse, and dissipating energy. The contact force-penetration relationship in the compression phase and restitution phase are assumed to be linear with a sharp jump at their transition. The slope of the compression phase of the force-displacement diagram of the non-dimensional system is exactly as desired (1+coefficient of restitution) and moreover, the slope of the restitution phase is equal to the coefficient of restitution helping in retrieving the exact coefficient of restitution pertaining in the pre-impact condition. Also, the post-impact coefficient of restitution, impulse, and dissipating energy are exactly accurate, having 0% error, in accordance with that of the stereo-mechanical model, for the full range of the co-efficient of restitution.
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Foltz, Heinrich, Obadiah Kegege, and Serhat Altunc. "Direction finding using an antenna with direction dependent impulse response." In 2016 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting. IEEE, 2016. http://dx.doi.org/10.1109/aps.2016.7696635.

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Çağlayan Akay, Ebru, Raziya Abdiyeva, and Zamira Oskonbaeva. "The Causal Relationship between Renewable Energy Consumption, Economic Growth and Carbon Dioxide Emissions: Evidence from Middle East and North Africa." In International Conference on Eurasian Economies. Eurasian Economists Association, 2015. http://dx.doi.org/10.36880/c06.01284.

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Renewable energy plays a crucial role in increasing economic growth while reducing carbon dioxide emissions. The aim of this study is to examine the interaction between renewable energy consumption, economic growth and carbon dioxide emissions for selected Middle East and North Africa countries. For this aim, panel vector autoregression approach are used in the study. The annual data used in this study cover the period from 1988 to 2010 for Middle East and North Africa countries. Firstly, second generation unit root test are used to investigate stationarity properties of the variables and second generation panel cointegration test is applied to the data under consideration because of the cross-sectional dependence. Then a panel causality approach is proposed to examine the causal relationship between the variables. Finally, panel vector autoregression model, impulse-response and variance decomposition analysis are applied using generalized moment methods. The finding of this study shows that there is a bi-directional causality between growth and renewable energy consumption, which is consistent with the feedback hypothesis in terms of the energy consumption-growth nexus. It is found the evidence of unidirectional causality from carbon dioxide emissions to renewable energy consumption and from growth to carbon dioxide emissions. It is also found that the responses of growth to a shock of energy consumption are positive and the impact of renewable energy consumption on carbon dioxide emissions is negative.
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Gölles, Lukas, and Franz Zotter. "Directional enhancement of first-order ambisonic room impulse responses by the 2+2 directional signal estimator." In AM'20: Audio Mostly 2020. New York, NY, USA: ACM, 2020. http://dx.doi.org/10.1145/3411109.3411131.

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Rafaely, Boaz. "Spherical microphone array with multiple nulls for analysis of directional room impulse responses." In ICASSP 2008 - 2008 IEEE International Conference on Acoustics, Speech and Signal Processing. IEEE, 2008. http://dx.doi.org/10.1109/icassp.2008.4517601.

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Pereira, Paulo, Tainá G. Rodovalho, Leandro B. Ambiel, Rafael H. Garcia, Rodrigo J. Leão, and Auteliano A. dos Santos. "Comparison of Signal Filtering Techniques for Ultrasonic Waves Used in Inspection of Composite Materials." In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-62601.

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The use of composite materials is growing worldwide as the number of its applications. Regarding the quality of components made from composites especially in fields that require high safety standards, such as aerospace, reliable inspection techniques must be used. Nondestructive inspection techniques using ultrasonic waves are largely employed in metals for fault detection, characterization, and stress measurement and they are also being applied in composites. However, composites are heterogeneous in nature and thus the signals acquired from ultrasonic transducers in these materials exhibit high noise, leading to inaccurate measurements. The objective of this work is to evaluate digital filtering techniques for signals from ultrasonic longitudinal bulk waves and longitudinal critically refracted (LCR) waves propagating in a carbon fiber-epoxy prepreg. Samples of unidirectional composites were manufactured to study the signals of waves propagating at different angles in relation to the carbon fibers direction. For bulk waves, we acquired signals at 0, 15, 30, 45, 60, 75 and 90° from the fiber directions; for LCR waves, the signals were measured at 0 and 90°. We compared the techniques based on digital filters IIR (Infinite Impulse Response), FIR (Finite Impulse Response) and Discrete Wavelet Transform (DWT). The results show that the filters FIR and IIR have the best signal-to-noise ratio (SNR) for most propagation directions, both for bulk and LCR waves.
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Ferreira, Marcos Donato, Mauro Costa de Oliveira, Rafaella Cristina Carvalho, and Sergio Hamilton Sphaier. "Asymmetric FPSO Roll Response due to the Influence of Lines Arrangement." In ASME 2012 31st International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/omae2012-83097.

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In the development of the mooring design of FPSOs in spread mooring system (SMS) configuration, it was observed that the utilization of asymmetric riser arrangement in deep waters might lead to an asymmetrical roll response of the FPSO. In particular, concentrating all riser connections on the portside, it could be observed that roll and heave coupling under the influence of the riser dynamics might lead to a much lower roll response associated with waves coming from portside than from the starboard direction. Simulations were carried using an in-house time domain simulator, where the ship hydrodynamic behavior was represented through the use of impulse response functions and the lines dynamic through the use of non-linear finite element method, using an explicit integration scheme and a lumped mass approach. Non-linear viscous effects could be easily associated to the ship and line velocities. Measured motion responses of an actual FPSO in operation in Campos Basin are compared with the computations.
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Badhurshah, R., and A. Samad. "Efficiency Enhancement of Bidirectional Impulse Turbine Using Artificial Neural Network." In ASME 2014 12th Biennial Conference on Engineering Systems Design and Analysis. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/esda2014-20305.

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The work represents a systematic numerical optimization methodology using artificial neural network and hybrid genetic algorithm for a bi-directional axial impulse turbine used in wave energy harvesting system. Reynolds-averaged Navier-Stokes equations with k-ε turbulence model were discretized and solved for unstructured tetrahedral grid elements for flow analyses. Efficiency enhancement of the turbine was chosen as an objective. The design variables chosen were numbers of stator and rotor blades. The responses obtained from CFD analysis were used to train the neural network. The optimal point search from the network by hybrid genetic algorithm produced 13% increase in turbine efficiency. Detailed description of the methodology and analysis of the results has been presented in this paper.
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Ecker, Horst, Josiah D. Knight, and Lan Wu. "Nonlinear Dynamic Simulation of an Active Magnetic Bearing System With Non-Symmetric Coordinate Coupling Forces." In ASME 1997 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/97-gt-113.

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Equations of motion are presented for a two degree of freedom system representing a rotor suspended with an active magnetic bearing. The rotor is subjected to both a rotating unbalance force and a steady load, which is balanced by differential bias in the vertical magnet pair. A coupling between the coordinate directions resulting from the spatial arrangement of magnets is included in the equations of motion, which renders them nonlinear even though the closed loop control on each axis is linear. Results of a path-following analysis of the equations show that the addition of a steady load has several effects. Compared with previous results for an unloaded system, the response is now asymmetric due to unequal stiffnesses, and the region of unacceptable high amplitude response extends over a larger frequency range. In addition, the frequency ranges over which multiple stable solutions coexist is expanded. New results for the unloaded case are also presented that show domains of attraction to large amplitude stable response due to an applied impulse. There is a strong dependence of the domains of attraction on the timing of the impulse.
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Hokazono, Taisuke, Ryuta Sato, Isamu Nishida, and Keiichi Shirase. "Evaluation of Contacting Effect Between Tool and Workpiece on Vibration Characteristics of NC Machine Tools." In JSME 2020 Conference on Leading Edge Manufacturing/Materials and Processing. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/lemp2020-8518.

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Abstract:
Abstract It is expected that the vibration characteristics of NC machine tools are affected by the contact between the tool and the workpiece during the cutting operations. However, the influences of the contact have not been clarified up to now. In this study, a method to evaluate the contacting effect and evaluated results are described. Frequency response of a vertical type milling machine during cutting operation is evaluated in this study. The evaluation tests of the contacting effect are carried out with and without cutting operations. In order to clearly evaluate the influence of the contact between a tool edge and a workpiece, boring operations of 50 mm diameter are carried out. The frequency responses are measured by using feed motor torque. Impulse signal is applied to the motor torque command during the cutting operations to oscillate the machine tool, and the axial acceleration of the table is measured to obtain the frequency responses. The impulse signal can be applied by refereeing the spindle rotational angle to control the relationships between the cutting edge and workpiece surface. As the results of the evaluations, it is clarified that the proposed method can evaluate the influence of the contact adequately. The natural frequency slightly increases and the vibration amplitude decreases when the tool contacts with the workpiece, regardless of whether non-cutting or cutting. It has also been confirmed that the vibration amplitude of the frequency characteristics is changed due to the contact length and the relative direction of the cutting edge.
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