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1
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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Dezfooliyan, Amir, and Andrew M. Weiner. "Experimental Investigation of UWB Impulse Response and Time Reversal Technique Up to 12 GHz: Omnidirectional and Directional Antennas." IEEE Transactions on Antennas and Propagation 60, no. 7 (July 2012): 3407–15. http://dx.doi.org/10.1109/tap.2012.2196927.
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Bastine, Amy, Thushara D. Abhayapala, and Jihui (Aimee) Zhang. "Power Response and Modal Decay Estimation of Room Reflections from Spherical Microphone Array Measurements Using Eigenbeam Spatial Correlation Model." Applied Sciences 11, no. 16 (August 21, 2021): 7688. http://dx.doi.org/10.3390/app11167688.
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Modal decays and modal power distribution in acoustic environments are key factors in deciding the perceptual quality and performance accuracy of audio applications. This paper presents the application of the eigenbeam spatial correlation method in estimating the time-frequency-dependent directional reflection powers and modal decay times. The experimental results evaluate the application of the proposed technique for two rooms with distinct environments using their room impulse response (RIR) measurements recorded by a spherical microphone array. The paper discusses the classical concepts behind room mode distribution and the reasons behind their complex behavior in real environments. The time-frequency spectrum of room reflections, the dominant reflection locations, and the directional decay rates emulate a realistic response with respect to the theoretical expectations. The experimental observations prove that our model is a promising tool in characterizing early and late reflections, which will be beneficial in controlling the perceptual factors of room acoustics.
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Yang, Yiqing, and Xi Wang. "Investigation into the linear velocity response of cantilever beam embedded with impact damper." Journal of Vibration and Control 25, no. 7 (January 21, 2019): 1365–78. http://dx.doi.org/10.1177/1077546318821711.
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The impact damper causes momentum exchange between the primary structure and impact mass, and achieves vibration attenuation through repeated collisions. A cantilever beam embedded with the impact damper is modeled in the form of a continuous system, and the equations of motion are formulated based on the mode superposition method. The mechanism of the impact damper is investigated, and linear velocity response is achieved by a proper selection of a mass ratio of 8.4%, clearance within 0.30 mm, and excitation force ranged from 3.2 N to 5.5 N. The reverse collision has higher damping than co-directional collision, based on which a new criterion of response regimes is proposed for the design of the impact damper. The velocity responses of the damped cantilever beam under sinusoidal and impulse excitation are simulated and verified via the sinusoidal sweep experiments. The velocity amplitudes of the damped cantilever beam are linearly decreased when the clearance is increased within 0.30 mm. Finally, linear and nonlinear velocity responses of the damped cantilever beam are discussed. It is found that the nonlinear velocity response reaches larger damping, but that a strongly modulated response exists.
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Astik, Mitesh B., Praghnesh Bhatt, and Bhavesh R. Bhalja. "Bi-Directional Position and Speed Estimation Algorithm for Sensorless Control of BLDC Motor." Electrical, Control and Communication Engineering 14, no. 2 (December 1, 2018): 125–33. http://dx.doi.org/10.2478/ecce-2018-0015.
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AbstractThe observer design for estimation of back EMF to control the Brushless DC (BLDC) motor is proposed in this paper. Rotor position of the BLDC motor is estimated using the sequence of estimated back EMF. During speed reversal of motor, the actual and estimated values of speed fail to track the reference speed and if corrective action is not taken by the observer, the motor goes into the unstable region. To overcome this problem, the speed estimation algorithm is proposed for BLDC motor control during its speed reversal operation. Infinite Impulse Response (IIR) Butterworth first order low-pass filters are used in the observer for smoothing the estimated back EMFs of the BLDC motor. A new controller scheme based on Modified Hybrid Fuzzy PI (MHFPI) controller is proposed to control the speed of the BLDC motor. The effectiveness of the proposed method has been validated through simulations for different disturbances such as step changes in the reference speed and load torque of the motor and results are compared with the existing methods.
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Lin, Ching-Chung, Shen-Yuan Chen, Dar-Yeh Hwang, and Chien-Fu Lin. "Does Index Futures Dominate Index Spot? Evidence from Taiwan Market." Review of Pacific Basin Financial Markets and Policies 05, no. 02 (June 2002): 255–75. http://dx.doi.org/10.1142/s021909150200078x.
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By utilizing vector error correction model (VECM) and EGARCH model, this article uses 5-minute intraday data to examine the interaction of return and volatility between Taiwan Stock Exchange Capitalization Weighted Stock Index (TAIEX) and the newly introduced TAIEX futures. VECM model shows that there exists bi-directional Granger causality between index spot and index futures markets, but spot market plays a more important role in price discovery. The results of impulse response function and information share indicate that most of the price discovery happens in index spot market. The evidence of EGRACH shows that the impacts of spot and futures innovations are asymmetrical, and the volatility spillovers between spot and futures markets are bi-directional. However, the information flow from spot to futures is stronger. These results suggest that the TAIEX spot market dominates the TAIEX futures market in terms of return and volatility.
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Gokmen, Orhan. "The Relationship between Foreign Direct Investment and Economic Growth: A Case of Turkey." International Journal of Economics and Finance 13, no. 7 (June 15, 2021): 85. http://dx.doi.org/10.5539/ijef.v13n7p85.
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This paper examines the relationship between net FDI inflows and real GDP for Turkey from 1970 to 2019. Although conventional economic growth theories and most empirical research suggest that there is a bi-directional positive effect between these macro variables, the results indicate that there is a uni- directional significant short-run positive effect of real GDP on net FDI inflows to Turkey by employing the Vector Error Correction Model, Granger Causality, Impulse Response Functions and Variance Decomposition. Also, there is no long-run effect of net FDI inflows found on real GDP, yet vice-versa long-run effect has been found. The findings recommend Turkish authorities optimally benefit from the potential positive effect of net incoming FDI on the real GDP by allocating it for the productive sectoral establishments while effectively maintaining the country’s real economic growth to attract further FDI inflows.
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Sheikh, Sharif I. Mitu, W. Abu-Al-Saud, and A. B. Numan. "Directive Stacked Patch Antenna for UWB Applications." International Journal of Antennas and Propagation 2013 (2013): 1–6. http://dx.doi.org/10.1155/2013/389571.
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Directional ultrawideband (UWB) antennas are popular in wireless signal-tracking and body-area networks. This paper presents a stacked microstrip antenna with an ultrawide impedance bandwidth of 114%, implemented by introducing defects on the radiating patches and the ground plane. The compact (20×34 mm) antenna exhibits a directive radiation patterns for all frequencies of the 3–10.6 GHz band. The optimized reflection response and the radiation pattern are experimentally verified. The designed UWB antenna is used to maximize the received power of a software-defined radio (SDR) platform. For an ultrawideband impulse radio system, this class of antennas is essential to improve the performance of the communication channels.
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Aw, S. T., G. M. Halmagyi, T. Haslwanter, I. S. Curthoys, R. A. Yavor, and M. J. Todd. "Three-dimensional vector analysis of the human vestibuloocular reflex in response to high-acceleration head rotations. II. responses in subjects with unilateral vestibular loss and selective semicircular canal occlusion." Journal of Neurophysiology 76, no. 6 (December 1, 1996): 4021–30. http://dx.doi.org/10.1152/jn.1996.76.6.4021.
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1. We studied the three-dimensional input-output human vestibuloocular reflex (VOR) kinematics after selective loss of semicircular canal (SCC) function either through total unilateral vestibular deafferentation (uVD) or through single posterior SCC occlusion (uPCO), and showed large deficits in magnitude and direction in response to high-acceleration head rotations (head “impulses”). 2. A head impulse is a passive, unpredictable, high-acceleration (3,000–4,000 degrees/s2) head rotation through an amplitude of 10–20 degrees in roll, pitch, or yaw. The subjects were tested while seated in the upright position and focusing on a fixation target. Head and eye rotations were measured with the use of dual search coils, and were expressed as rotation vectors. A three-dimensional vector analysis was performed on the input-output VOR kinematics after uVD, to produce two indexes in the time domain: magnitude and direction. Magnitude is expressed as speed gain (G) and direction as misalignment angle (delta). 3. G. after uVD, was significantly lower than normal in both directions of head rotation during roll, pitch, and yaw impulses, and were much lower during ipsilesional than during contralesional roll and yaw impulses. At 80 ms from the onset of an impulse (i.e., near peak head velocity), G was 0.23 +/- 0.08 (SE) (ipsilesional) and 0.56 +/- 0.08 (contralesional) for roll impulses, 0.61 +/- 0.09 (up) and 0.72 +/- 0.10 (down) for pitch impulses, and 0.36 +/- 0.06 (ipsilesional) and 0.76 +/- 0.09 (contralesional) for yaw impulses (mean +/- 95% confidence intervals). 4. delta, after uVD, was significantly different from normal during ipsilesional roll and yaw impulses and during pitch-up and pitch-down impulses. delta was normal during contralesional roll and yaw impulses. At 80 ms from the onset of the impulse, delta was 30.6 +/- 4.5 (ipsilesional) and 13.4 +/- 5.0 (contralesional) for roll impulses, 23.7 +/- 3.7 (up) and 31.6 +/- 4.4 (down) for pitch impulses, and 68.7 +/- 13.2 (ipsilesional) and 11.0 +/- 3.3 (contralesional) for yaw impulses (mean +/- 95% confidence intervals). 5. VOR gain (gamma), after uVD, were significantly lower than normal for both directions of roll, pitch, and yaw impulses and much lower during ipsilesional than during contralesional roll and yaw impulses. At 80 ms from the onset of the head impulse, the gamma was 0.22 +/- 0.08 (ipsilesional) and 0.54 +/- 0.09 (contralesional) for roll impulses, 0.55 +/- 0.09 (up) and 0.61 +/- 0.09 (down) for pitch impulses, and 0.14 +/- 0.10 (ipsilesional) and 0.74 +/- 0.06 (contralesional) for yaw impulses (mean +/- 95% confidence intervals). Because gamma is equal to [G*cos (delta)], it is significantly different from its corresponding G during ipsilesional roll and yaw, and during all pitch impulses, but not during contralesional roll and yaw impulses. 6. After uPCO, pitch-vertical gamma during pitch-up impulses was reduced to the same extent as after uVD; roll-torsional gamma during ipsilesional roll impulses was significantly lower than normal but significantly higher than after uVD. At 80 ms from the onset of the head impulse, gamma was 0.32 +/- 0.13 (ipsilesional) and 0.55 +/- 0.16 (contralesional) for roll impulses, 0.51 +/- 0.12 (up) and 0.91 +/- 0.14 (down) for pitch impulses, and 0.76 +/- 0.06 (ipsilesional) and 0.73 +/- 0.09 (contralesional) for yaw impulses (mean +/- 95% confidence intervals). 7. The eye rotation axis, after uVD, deviates in the yaw plane, away from the normal interaural axis, toward the nasooccipital axis, during all pitch impulses. After uPCO, the eye rotation axis deviates in same direction as after uVD during pitch-up impulses, but is well aligned with the head rotation axis during pitch-down impulses.
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Feng, Shan Yong, Fang Shuo Mo, Yue Ying Zhao, and Sheng Wo Sheng. "The Performance of Rotating Dual-Microphone System and its Application." Applied Mechanics and Materials 209-211 (October 2012): 225–29. http://dx.doi.org/10.4028/www.scientific.net/amm.209-211.225.
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The rotating dual-microphone system is designed to measure the spatial acoustical parameters of sound field in the room. It is mainly composed of a repeatable inspiriting sound source associated with two microphone fixed on slowly rotating platform. In this paper, a comprehensive investigation of performance of the test system by means of computer simulation and the experiment in anechoic chamber is presented, as well as the main affecting factors are also discussed. The spatial resolution of the system varies not only with the radius of the rotating microphone, but also with the direction of arriving sound wave. The study indicates that the system is provided with enough spatial resolution and can be applied to the room acoustic measurement conveniently. When the radius of the rotating microphone is more than 0.2m the measured beam width is less than 10 degrees. By using this system the directional impulse response of room can be analyzed in detail, and various objective spatial parameters of sound field can be obtained. Some practical applications in the auditorium are also described in this paper.
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Bai, Mingsian R., and Teng-Chieh Tsao. "Numerical Modeling of Head-Related Transfer Functions Using the Boundary Source Representation." Journal of Vibration and Acoustics 128, no. 5 (April 4, 2006): 594–603. http://dx.doi.org/10.1115/1.2203337.
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A technique based on the virtual source representation is presented for modeling head-related transfer functions (HRTFs). This method is motivated by the theory of simple layer potential and the principle of wave superposition. Using the virtual source representation, the HRTFs for a human head with pinnae are calculated with a minimal amount of computation. In the process, a special regularization scheme is required to calculate the equivalent strengths of virtual sources. To justify the proposed method, tests were carried out to compare the virtual source method with the boundary element method (BEM) and a direct HRTF measurement. The HRTFs obtained using the virtual source method agrees reasonably well in terms of frequency response, directional response, and impulse response with the other methods. From the numerical perspectives, the virtual source method obviates the singularity problem as commonly encountered in the BEM, and is less computationally demanding than the BEM in terms of computational time and memory storage. Subjective experiments are also conducted using the calculated and the measured HRTFs. The results reveal that the spatial characteristics of sound localization are satisfactorily reproduced as a human listener would naturally perceive by using the virtual source HRTFs.
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Ocran, Matthew. "South Africa and United States stock prices and the Rand/Dollar exchange rate." South African Journal of Economic and Management Sciences 13, no. 3 (September 3, 2010): 362–75. http://dx.doi.org/10.4102/sajems.v13i3.106.
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This paper seeks to examine the dynamic causal relations between the two major financial assets, stock prices of the US and South Africa and the rand/US$ exchange rate. The study uses a mixed bag of time series approaches such as cointegration, Granger causality, impulse response functions and forecasting error variance decompositions. The paper identifies a bi-directional causality from the Standard & Poor’s 500 stock price index to the rand/US$ exchange rate in the Granger sense. It was also found that the Standard & Poor’s stock price index accounts for a significant portion of the variations in the Johannesburg Stock Exchange’s All Share index. Thus, while causality in the Granger sense could not be established for the relationship between the price indices of the two stock exchanges it can argued that there is some relationship between them. The results of the study have implications for both business and Government.
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Vadarevu, Sabarish B., Sean Symon, Simon J. Illingworth, and Ivan Marusic. "Coherent structures in the linearized impulse response of turbulent channel flow." Journal of Fluid Mechanics 863 (January 30, 2019): 1190–203. http://dx.doi.org/10.1017/jfm.2019.15.
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We study the evolution of velocity fluctuations due to an isolated spatio-temporal impulse using the linearized Navier–Stokes equations. The impulse is introduced as an external body force in incompressible channel flow at $Re_{\unicode[STIX]{x1D70F}}=10\,000$. Velocity fluctuations are defined about the turbulent mean velocity profile. A turbulent eddy viscosity is added to the equations to fix the mean velocity as an exact solution, which also serves to model the dissipative effects of the background turbulence on large-scale fluctuations. An impulsive body force produces flow fields that evolve into coherent structures containing long streamwise velocity streaks that are flanked by quasi-streamwise vortices; some of these impulses produce hairpin vortices. As these vortex–streak structures evolve, they grow in size to be nominally self-similar geometrically with an aspect ratio (streamwise to wall-normal) of approximately 10, while their kinetic energy density decays monotonically. The topology of the vortex–streak structures is not sensitive to the location of the impulse, but is dependent on the direction of the impulsive body force. All of these vortex–streak structures are attached to the wall, and their Reynolds stresses collapse when scaled by distance from the wall, consistent with Townsend’s attached-eddy hypothesis.
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Aw, S. T., T. Haslwanter, G. M. Halmagyi, I. S. Curthoys, R. A. Yavor, and M. J. Todd. "Three-dimensional vector analysis of the human vestibuloocular reflex in response to high-acceleration head rotations. I. Responses in normal subjects." Journal of Neurophysiology 76, no. 6 (December 1, 1996): 4009–20. http://dx.doi.org/10.1152/jn.1996.76.6.4009.
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1. The kinematics of the human angular vestibuloocular reflex (VOR) in three dimensions was investigated in 12 normal subjects during high-acceleration head rotations (head “impulses”). A head impulse is a passive, unpredictable, high-acceleration (3,000–4,000 degrees/s2) head rotation of approximately 10–20 degrees in roll, pitch, or yaw, delivered with the subject in the upright position and focusing on a fixation target. Head and eye rotations were measured with dual search coils and expressed as rotation vectors. The first of these two papers describes a vector analysis of the three-dimensional input-output kinematics of the VOR as two indexes in the time domain: magnitude and direction. 2. Magnitude is expressed as speed gain (G) and direction as misalignment angle (delta). G is defined as the ratio of eye velocity magnitude (eye speed) to head velocity magnitude (head speed). delta is defined as the instantaneous angle by which the eye rotation axis deviates from perfect alignment with the head rotation axis in three dimensions. When the eye rotation axis aligns perfectly with the head rotation axis and when eye velocity is in a direction opposite to head velocity, delta = 0. The orientation of misalignment between the head and the eye rotation axes is characterized by two spatial misalignment angles, which are the projections of delta onto two orthogonal coordinate planes that intersect at the head rotation axis. 3. Time series of G were calculated for head impulses in roll, pitch, and yaw. At 80 ms after the onset of an impulse (i.e., near peak head velocity), values of G were 0.72 +/- 0.07 (counterclockwise) and 0.75 +/- 0.07 (clockwise) for roll impulses, 0.97 +/- 0.05 (up) and 1.10 +/- 0.09 (down) for pitch impulses, and 0.95 +/- 0.06 (right) and 1.01 +/- 0.07 (left) for yaw impulses (mean +/- 95% confidence intervals). 4. The eye rotation axis was well aligned with head rotation axis during roll, pitch, and yaw impulses: delta remained almost constant at approximately 5–10 degrees, so that the spatial misalignment angles were < or = 5 degrees. delta was 9.6 +/- 3.1 (counterclockwise) and 9.0 +/- 2.6 (clockwise) for roll impulses, 5.7 +/- 1.6 (up) and 6.1 +/- 1.9 (down) for pitch impulses, and 6.2 +/- 2.2 (right) and 7.9 +/- 1.5 (left) for yaw impulses (mean +/- 95% confidence intervals). 5. VOR gain (gamma) is the product of G and cos(delta). Because delta is small in normal subjects, gamma is not significantly different from G. At 80 ms after the onset of an impulse, gamma was 0.70 +/- 0.08 (counterclockwise) and 0.74 +/- 0.07 (clockwise) for roll impulses, 0.97 +/- 0.05 (up) and 1.09 +/- 0.09 (down) for pitch impulses, and 0.94 +/- 0.06 (right) and 1.00 +/- 0.07 (left) for yaw impulses (mean +/- 95% confidence intervals). 6. VOR latencies, estimated with a latency shift method, were 10.3 +/- 1.9 (SD) ms for roll impulses, 7.6 +/- 2.8 (SD) ms for pitch impulses, and 7.5 +/- 2.9 (SD) ms for yaw impulses. 7. We conclude that the normal VOR produces eye rotations that are almost perfectly compensatory in direction as well as in speed, but only during yaw and pitch impulses. During roll impulses, eye rotations are well aligned in direction, but are approximately 30% slower in speed.
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Fuentes, Fernanda, and Rodrigo Herrera. "Dynamics of Connectedness in Clean Energy Stocks." Energies 13, no. 14 (July 18, 2020): 3705. http://dx.doi.org/10.3390/en13143705.
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This paper examines the dynamics of connectedness among the realized volatility indices of 16 clean energy stocks belonging to the SPGCE and the implied volatility indices of two important stock markets—the S&P 500 and the STOXX50—and two commodities markets—the crude oil and gold markets. The empirical results show a unidirectional connectedness from the implied volatility indices to the clean energy stocks. Our analysis further reveals similar volatility connectedness behaviors among companies in the same energy production subsector. However, there exists heterogeneous behavior between different energy production subsectors over time. Further, we identify pairwise directional connectedness clusters among related companies, indicating that there are few possibilities for portfolio diversification within the energy production subsectors. Finally, through an impulse–response analysis, we confirm that the expectation of future market volatility of the S&P 500 index and the gold price plays a leading role in volatility connectedness with clean energy stocks.
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Alnefaee, Saad Mohammed. "Short and Long-Run Determinants of Inflation in Saudi Arabia: A Cointegration Analysis." International Journal of Financial Research 9, no. 4 (August 21, 2018): 35. http://dx.doi.org/10.5430/ijfr.v9n4p35.
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This paper investigates the short and long-run determinants of inflation in Saudi Arabia for the period of 1987-2017. To achieve this objective, the Johansen and Julius cointegration procedure and Vector Error Correction Model (VECM) were conducted to examine the existence of the short and long-run relationships between inflation, the money supply, domestic demand, the exchange rate and oil prices. The results reveal that inflation, in the long-run, is positively influenced by the money supply, domestic demand, and oil prices. It is negatively influenced by the exchange rate. Inflation is also highly influenced by domestic factors in the short-run (e.g., money supply, domestic demand). The Granger causality results indicate a bi-directional causality between the money supply and inflation. The unidirectional causality goes from the domestic demand and the oil prices to the price level. The Impulse Response Analysis illustrates that shocks associated with the money supply, domestic demand and oil prices have a positive impact on inflation.
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Ahmed, Waqas, Khalid Zaman, Sadaf Taj, Rabiah Rustam, Muhammad Waseem, and Muhammad Shabir. "Economic growth and energy consumption nexus in Pakistan." South Asian Journal of Global Business Research 2, no. 2 (August 16, 2013): 251–75. http://dx.doi.org/10.1108/sajgbr-05-2011-0010.
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PurposeThis study aims to examine the relationship between electricity consumption per capita (ELEC) and real per capita income (Y), as the direction of causation of this relationship remains controversial in the existing literature. It also seeks to explore the relationship between energy consumption per capita (ENC) and real per capita income, over a 34‐year period (between 1975 and 2009).Design/methodology/approachThe study uses Johansen cointegration technique to determine the short‐ and long‐run relationship between the variables. The authors also utilize Granger causality test to determine the causal relationship between the selected variables.FindingsThe study provides evidence of bi‐directional causality between the electricity consumption per capita and real per capita income on one hand; and energy consumption per capita and real per capita income on the other hand as the direction of causality has significant policy implications.Research limitations/implicationsThis study does not include all dimensions of the energy growth, but is limited to the three variables which the authors consider to be critical to economic development, including energy consumption, electricity consumption and economic growth.Originality/valueThe study uses a sophisticated econometric technique with additional tests of forecasting framework to examine the effect of energy demand on economic growth over a period of the next ten years, i.e. 2010‐2019, in the context of Pakistan. The impulse response describes the reaction of the system as a function of independent variable that parameterizes the dynamic behavior of the system.
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Royer, Sébastien, Marzia Martina, and Denis Paré. "Polarized Synaptic Interactions Between Intercalated Neurons of the Amygdala." Journal of Neurophysiology 83, no. 6 (June 1, 2000): 3509–18. http://dx.doi.org/10.1152/jn.2000.83.6.3509.
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The intercalated (ITC) cell masses are small GABAergic cell clusters interposed between the basolateral (BL) complex and central (CE) nucleus of the amygdala. ITC cells receive excitatory afferents from the BL complex and generate feed-forward inhibition in the CE nucleus. Recently it was shown that ITC cells could gate impulse traffic between the BL complex and CE nucleus in a spatiotemporally differentiated manner. In addition, it was hypothesized that lateromedial inhibitory interactions between different ITC cell clusters played a critical role in this respect. Given the potential importance of such conditional computations, the present study aimed to characterize the connectivity existing among ITC cells. To this end, whole cell recordings of ITC neurons were obtained under visual guidance in coronal slices of the guinea pig amygdala. Electrical stimuli applied in the BL complex primarily elicited excitatory responses when they were applied at the same lateromedial level or more medially than the recorded ITC cells. As the stimulation site was moved laterally, the character of the response shifted toward inhibition. Both bicuculline and non- N-methyl-d-aspartate receptor antagonists abolished this BL-evoked inhibition, suggesting that it was not mediated by BL inhibitory cells projecting to ITC neurons. In keeping with this, local glutamate injections in and around the ITC clusters revealed that the most effective site to inhibit ITC cells were ITC clusters located laterally with respect to the recorded one. The activation of more medial ITC clusters evoked much smaller responses. Thus, connections between ITC clusters tend to run in a lateromedial direction. To identify the source of these directionally polarized synaptic interactions, the morphological features of ITC cells were analyzed by intracellular injection of Neurobiotin. This analysis revealed that the dendritic tree and axonal arbor of ITC cells are asymmetric in the lateromedial plane. In particular, their laterally directed dendrites were longer than the medial ones, whereas their laterally directed axon collaterals were shorter than the medial ones. It is concluded that the morphological asymmetry of ITC cells accounts for the directional polarization of inter-ITC connections. The significance of these findings for the gating of information transfer from the BL complex to the CE nucleus is discussed.
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Vicker, M. G., J. M. Lackie, and W. Schill. "Neutrophil leucocyte chemotaxis is not induced by a spatial gradient of chemoattractant." Journal of Cell Science 84, no. 1 (August 1, 1986): 263–80. http://dx.doi.org/10.1242/jcs.84.1.263.
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Chemotaxis and directed locomotion of neutrophil leucocytes are generally thought to be determined by the directed response of the cell to stable, spatial gradients of chemoattractants. In most cases, however, cells are also exposed to characteristic temporal changes in the attractant concentration during the lifetime of the gradient, especially as it develops. We have attempted to test whether neutrophils can respond to a spatial gradient in which these temporal changes are essentially absent. Gradients of formyl-peptides were made across a narrow barrier of agarose gel that separated two fluid reservoirs, and the cells were observed cinematographically as they moved between gel and glass. In gradients predeveloped at low temperature, at which cell motion and responses to attractant were inhibited, neutrophils showed no tendency to accumulate up-gradient when warmed to 37 degrees C. Yet their speed and turning behaviour was related to the local concentration of formyl-peptide. However, gradients that developed at 37 degrees C, whilst the cells were responsive, elicited directed locomotion. We also tested populations that were either spreading into or already evenly distributed across micropore filters to see how cells might sense directional cues. We reasoned that evenly distributed populations could accumulate in a spatial gradient only if cells were able to ‘read’ it. However, no redistribution occurred without an applied impulse of attractant. It seems that the oriented, temporal component of an attractant signal is essential if a directed response (i.e. non-random turning) is to occur; a spatial gradient of soluble attractant alone does not induce neutrophil accumulation or taxis. This finding has implications for the termination of the acute inflammatory response, for clinical tests of leucocyte behaviour and for morphogen signal interpretation by cells in developing tissues.
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Hu, Jin-Li, Tzu-Pu Chang, Fang-Yu Yeh, and Tzu-Cheng Yang. "The Linkage between Imported Energy and Trade in Taiwan." ISRN Economics 2012 (September 2, 2012): 1–11. http://dx.doi.org/10.5402/2012/816964.
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This study examines the Granger causality between Taiwan's aggregate and disaggregate energy consumption and trade variables, including total imports (IM), total exports (EX), total energy consumption (ENERGY), oil and petroleum products consumption (OIL), coal and coal products consumption (COAL), natural gas consumption (GAS), export value of the industrial sector (EX_I), export value of heavy-chemical industrial products (EX_HI), and export value of non-heavy-chemical industrial products (EX_NHI) with monthly data during 1998–2009. Via applying Hsiao's version of the Granger causality method, the results find causality running from ENERGY to IM, EX, EX_I, and EX_HI. The impulse-response simulations show that the above relations have positive responses at the initial period. OIL Granger causes all trade variables. The impulse directions to IM and EX_NHI are negative, whereas others are positive. On the other hand, COAL responds to impulses in all trade variables. The impulse-response simulations show that these relations have positive responses at the initial period except for causality running from EX_HI and EX_NHI to COAL. GAS positively responds to impulses in EX, EX_I, and EX_HI at the initial period. The bidirectional Granger causality between pairs of variables (such as GAS and EX_NHI as well as GAS and EX_HI) is found.
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Dugda, Mulugeta, and Farzad Moazzami. "Generalized Pattern Search Algorithm for Crustal Modeling." Computation 8, no. 4 (December 8, 2020): 105. http://dx.doi.org/10.3390/computation8040105.
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In computational seismology, receiver functions represent the impulse response for the earth structure beneath a seismic station and, in general, these are functionals that show several seismic phases in the time-domain related to discontinuities within the crust and the upper mantle. This paper introduces a new technique called generalized pattern search (GPS) for inverting receiver functions to obtain the depth of the crust–mantle discontinuity, i.e., the crustal thickness H, and the ratio of crustal P-wave velocity Vp to S-wave velocity Vs. In particular, the GPS technique, which is a direct search method, does not need derivative or directional vector information. Moreover, the technique allows simultaneous determination of the weights needed for the converted and reverberated phases. Compared to previously introduced variable weights approaches for inverting H-κ stacking of receiver functions, with κ = Vp/Vs, the GPS technique has some advantages in terms of saving computational time and also suitability for simultaneous determination of crustal parameters and associated weights. Finally, the technique is tested using seismic data from the East Africa Rift System and it provides results that are consistent with previously published studies.
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Mickiewicz, Witold, Michał Raczyński, and Arkadiusz Parus. "Performance Analysis of Cost-Effective Miniature Microphone Sound Intensity 2D Probe." Sensors 20, no. 1 (January 3, 2020): 271. http://dx.doi.org/10.3390/s20010271.
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This article presents the functional properties of modified versions of the 2D pressure–pressure intensity probe allowing us to determine the vector of sound intensity on a plane using a mechatronic system with one or two miniature electret microphones. The introduction contains basic information about the application areas of the sound intensity and its measurement problems. Next, the principle of operation of the probes and the construction of the prototype measurement system are described. It was subjected to comparative analysis for the stability of obtained results and accuracy of directional characteristics in free field conditions. For this purpose, experiments were conducted to analyze the flow of acoustic power in an anechoic chamber using both (one- and two-microphone) probes. The results were used for a comparative metrological analysis of the described methods and to indicate the advantages and disadvantages of both constructions. The next part of the article presents an experiment concerning the measurement of the sound intensity impulse response of a room, which is an example of practical use of the probe to analyze reflections in the room, which can be used in sound engineering and architectural acoustics.
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Pesterev, Ivan S., and Boris G. Stepanov. "RESEARCH OF WIDEBAND HYDRO ACOUSTIC SYSTEM, CONTAINING TRANSDUCERS OF WAVEGUIDE TYPE." Journal of the Russian Universities. Radioelectronics, no. 5 (December 6, 2018): 60–70. http://dx.doi.org/10.32603/1993-8985-2018-21-5-60-70.
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The results of experimental research of models of antennas hydroacoustic system (HAS), containing transducers of the waveguide type (TWT), which represent a coaxial set of identical water-filled piezocylinders, electrically excited by the principle of a traveling wave formation in the inner cavity of the TWT, are given. Possibilities of the TWT are analyzed when they are excited in accordance with the solution of the synthesis problem for the investigated HAS. The realization of such excitation is carried out by means of software-controlled multichannel blocks and allows providing a close to uniform amplitude-frequency characteristic of radiation and linear phase-frequency characteristic of radiation in a 3-octave frequency band. The possibility of radiation in this band of ultrashort pulses, tunable in frequency, as well as the formation of signals similar to the signals of cetaceans, is shown. The influence of the number of active piezocylinders of the TWT and the character of its electric excitation on the frequency and impulse response of the investigated HAS is considered. Directional properties of models of antennas HAS, including scanning and pulse operation modes, are considered. A comparative evaluation of the calculated and experimental data, as well as an evaluation of the efficiency of the TWT radiation, is given.
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D’Orazio, Dario, Elena Rossi, and Massimo Garai. "Comparison of different in situ measurements techniques of intelligibility in an open-plan office." Building Acoustics 25, no. 2 (June 2018): 111–22. http://dx.doi.org/10.1177/1351010x18776431.
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Acoustic comfort in open-plan offices is a relatively recent research topic and some practices have not yet been consolidated. The goal in these spaces is to achieve good speech privacy at every workstation, reaching a high value of spatial decay of the sound pressure level. In case of refurbishment, a proper measurement of intelligibility criteria is needed, for example, in order to properly calibrate a numerical model or to plan acoustic treatments. This work compares different measurement techniques to evaluate the spatial distribution of intelligibility criteria. In situ measurements were done in an open-plan office used as a case study. Both omnidirectional and directional sound sources with different sound power levels were used, according, respectively, to ISO 3382-3:2012 and ITU-T P.51:1996. Furthermore, compensation algorithms were used in impulse response measurements in presence of Heating, Ventilation and Air Conditioning noise. The study shows, in a preliminary way, how different techniques and equipment can influence intelligibility criteria used in the open-plan office characterization. Results show that the indirect method of measuring Speech Transmission Index could not be used when the background level is high as the case study while the direct method returns good results.
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Liow, KimHiang, Xiaoxia Zhou, Qiang Li, and Yuting Huang. "Dynamic interdependence between the US and the securitized real estate markets of the Asian-Pacific economies." Journal of Property Investment & Finance 37, no. 1 (February 4, 2019): 92–117. http://dx.doi.org/10.1108/jpif-07-2018-0048.
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Purpose The purpose of this paper is to revisit the dynamic linkages between the US and the national securitized real estate markets of each of the nine Asian-Pacific (APAC) economies in time-frequency domain. Design/methodology/approach Wavelet decomposition via multi-resolution analysis is employed as an empirical methodology to consider time-scale issue in studying the dynamic changes of the US–APAC cross-real estate interdependence. Findings The strength and direction of return correlation, return exogeneity, shock impulse response, market connectivity and causality interactions change when specific time-scales are involved. The US market correlates with the APAC markets weakly or moderately in the three investment horizons with increasing strength of lead-lag interdependence in the long-run. Moreover, there are shifts in the net total directional volatility connectivity effects at the five scales among the markets. Research limitations/implications Given the focus of the five approaches and associated indicators, the picture that emerges from the empirical results may not completely uniform. However, long-term investors and financial institutions should evaluate the time-scale based dynamics to derive a well-informed portfolio decision. Practical implications Future research is needed to ascertain whether the time-frequency findings can be generalizable to the regional and global context. Additional studies are required to identify the factors that contribute to the changes in the global and regional connectivity across the markets over the three investment horizons. Originality/value This study has successfully decomposed the various market linkage indicators into scale-dependent sub-components. As such, market integration in the Asia-Pacific real estate markets is a “multi-scale” phenomenon.
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Zhang, Xubao. "Designs, Experiments, and Applications of Multichannel Structures for Hearing Aids." European Journal of Electrical Engineering and Computer Science 5, no. 4 (August 3, 2021): 46–55. http://dx.doi.org/10.24018/ejece.2021.5.4.347.
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The structures of common multichannel processing for hearing aids include equal bandwidth (BW) finite impulse response (FIR) filter bank, nonuniform BW FIR filter bank, and fast Fourier transform (FFT) plus inverse FFT (IFFT). This paper analyzes their operation principles, indicates the design methods by means of MATLAB R2018b resources, and describes the main characteristics: synthetical ripple, bank filters’ group delays, and individual filter sidelobe attenuation. Three schemes are proposed: equal BW sixteen-filter bank, logarithmic BW eight-filter bank, and 128-point FFT plus IFFT with overlap-add operation. To build the experimental modules, we introduce the settings of spectrum scopes, the acquirement of realistic speech and noises, and the gain enhancing/reducing needs of hearing aid features; the characteristics of synthetical outputs confirm precise control ability of the multichannel modules and differences between the three schemes. Subsequently, this paper illustrates two applications of the multichannel structures in hearing aids, the equal BW sixteen-filter bank with spectral subtraction (SS) for an artificial intelligence (AI) noise reduction (NR) and 128-point FFT plus IFFT spectral distortion removal for a directional microphone (DM). In Amy’s speech mixed with ringing, milk steamer, and strong wind noises separately, the SS processor improves signal-noise-ratio (SNR) by 6.5 to 15.9 dB. By measuring waveforms and spectra at the DM input and output, the DM system seamlessly removes the spectral distortion.
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Vega-Bermudez, F., and K. O. Johnson. "SA1 and RA Receptive Fields, Response Variability, and Population Responses Mapped with a Probe Array." Journal of Neurophysiology 81, no. 6 (June 1, 1999): 2701–10. http://dx.doi.org/10.1152/jn.1999.81.6.2701.
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SA1 and RA receptive fields, response variability, and population responses mapped with a probe array. Twenty-four slowly adapting type 1 (SA1) and 26 rapidly adapting (RA) cutaneous mechanoreceptive afferents in the rhesus monkey were studied with an array of independently controlled, punctate probes that covered an entire fingerpad. Each afferent had a receptive field (RF) on a single fingerpad and was studied at 73 skin sites (50 mm2). The entire array was lowered to 1.6 mm below the point of initial skin contact (the background indentation) before delivering single-probe indentations. SA1 and RA responses differed in several ways. 1) SA1 RF boundaries were affected much less by indentation depth than were RA boundaries, and the SA1 RF areas were much more uniform in size. The mean SA1 RF area grew from 5.1 to 8.8 mm2 as the indentation depth increased from 50 to 500 μm; the mean RA RF area grew from 5.5 to 22.4 mm2 over the same intensity range. 2) SA1 RFs were more elongated than RA RFs. Elongated RFs were oriented in all directions relative to the skin ridges and the finger axis. 3) SA1 impulse rates were linear functions of indentation depth at all probe locations in the RF; RA responses tended toward saturation beginning at 100 μm indentation depth when the probe was over the HS. Similarities between SA1 and RA responses were that 1) both were extremely repeatable with SDs < 1 impulse per trial and 2) both had population responses (number of impulses) that were nearly linear functions of indentation depth. However, SA1s represented increasing indentation depth by increasing impulse rates in a small, relatively constant group of afferents, whereas the RAs represented increasing indentation depth predominantly by the recruitment of new afferents at a distance.
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Ruichong Zhang, Ray. "Concept and Fundamentals of Temporal-Spatial Pulse Representation for Dislocation Source Modeling." Journal of Applied Mechanics 71, no. 6 (November 1, 2004): 887–93. http://dx.doi.org/10.1115/1.1855316.
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For far-field wave-motion response to a point dynamic dislocation source, the temporal and spatial features of the source mechanism are characterized, respectively, by two factors, i.e., a source time function for dislocation growth and a combination of nine couples of impulse forces that is equivalent to the final dislocation. The mathematical representation for each of the couples, referred to as spatial couples, is a couple of impulses acting in opposing directions with an infinitesimal separation distance or, in the limit, by the derivative of the impulse with respect to the separation-distance parameter. This study proposes a temporal-spatial pulse representation for the nine couples, referred to as temporal-spatial couples, and subsequently for the dislocation source modeling. Each temporal-spatial couple consists of two impulses acting in opposite directions with both an infinitesimal separation distance and an infinitesimal time delay. By examining dynamite source modeling, this study shows that the proposed representation can intrinsically integrate the spatial and temporal features of the dislocation sources from the response point of view. This study also shows an example of a point, shear-slip seismic source modeling using traditional and proposed pulse representations for far-field wave motion. Discussion is finally provided for the implications of the proposed representation in broad applications.
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Johnsen, Skjalg E., and Mats Trulsson. "Receptive Field Properties of Human Periodontal Afferents Responding to Loading of Premolar and Molar Teeth." Journal of Neurophysiology 89, no. 3 (March 1, 2003): 1478–87. http://dx.doi.org/10.1152/jn.00537.2002.
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Impulses in 45 single mechanoreceptive afferents were recorded from the human inferior alveolar nerve with permucosally inserted tungsten microelectrodes. All afferents responded to mechanical stimulation of one or more premolar or molar teeth and most likely innervated their periodontal ligaments. For each afferent, isolated “ramp-and-hold” shaped force profiles of similar magnitudes (252 ± 24 mN; mean ± SD) were applied to the lower first premolar, the second premolar, and the first molar on the recording side. The tooth loads were applied in six directions: lingual, facial, mesial, and distal in the horizontal plane and up and down in the vertical direction of the tooth. The afferents response during the static phase of the stimulus was analyzed. All afferents were slowly adapting, discharging continuously in response to static forces in at least one stimulation direction. Twenty-nine afferents (64%) were spontaneously active, exhibiting an ongoing discharge in the absence of external stimulation. Stimulation of a single tooth was found to excite each afferent most strongly. The most sensitive tooth (MST) was the first premolar for 23, the second premolar for 13, and the first molar for 9 afferents. About half of the afferent population also responded to loading of one or two more teeth. The response profiles of these afferents indicated that the multiple-teeth receptive fields were due to mechanical coupling between the teeth rather than branching of single afferents to innervate several teeth. The afferent responses to loading the mesial and distal halves of the first molars were very similar. Thus both intensive and directional aspects of the afferent response when loading one side of the tooth was preserved to a great extent when loading the other side. When loading the MST, the afferents typically showed excitatory responses in two to four of the six stimulation directions, i.e., the afferents were broadly tuned to direction of tooth loading. In the horizontal plane, the afferent populations at the premolar teeth expressed no clear directional preferences. The afferents at the molar, however, showed a strong directional bias in the distal-lingual direction. In the vertical plane, there was a preference for downward-directed forces with a gradually decreasing sensitivity distally along the dental arch. The present results demonstrate that human periodontal afferents supplying anterior and posterior teeth differ in their capacity to signal horizontal and vertical forces, respectively.
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Marques, Luís Miguel, José Alberto Fuinhas, and António Cardoso Marques. "On the restricted form of energy-growth nexus: a global level VECM approach and the historical structural breaks." International Journal of Energy Sector Management 14, no. 6 (May 1, 2020): 1205–20. http://dx.doi.org/10.1108/ijesm-09-2019-0009.
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Purpose The purpose of this paper is to focus on global energy consumption using the economic growth nexus, the prevalent energy hypothesis at a global level and the impact of the main historical events assessed for the period from 1965 to 2015. Design/methodology/approach Given the confirmed presence of endogeneity and cointegration between energy consumption and economic growth, a vector error correction with structural dummies model was used. Furthermore, the impulse-response functions and variance decomposition were computed to evaluate the variables’ dynamics. Findings Bi-directional causality running from energy consumption to economic growth was found, both in the short and long-run, supporting the feedback hypothesis. It is proved that the 2008 crisis impacted on the global energy–growth nexus. Furthermore, there is evidence of the impact of the 1990s oil price shock on the nexus. Innovations in energy consumption have a positive impact on economic growth; however, this impact tends to be null in the long run. Practical implications The results suggest that at a global level, any energy policy should be carefully designed in order not to hamper economic growth. Countries should not remain indifferent to the policies that other countries might follow. Very few historical crises impacted on the global energy–growth nexus. Originality/value This paper offers a different approach to the study of the energy–growth nexus. The energy–growth nexus is analysed in the major macroeconomic aggregate. Global variables reveal their relevance as a benchmark in the energy–growth nexus. Furthermore, this paper arrives at some conclusions about how historical crises impact on global relationships.
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Müller, Kaspar, and Franz Zotter. "Auralization based on multi-perspective ambisonic room impulse responses." Acta Acustica 4, no. 6 (2020): 25. http://dx.doi.org/10.1051/aacus/2020024.
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Most often, virtual acoustic rendering employs real-time updated room acoustic simulations to accomplish auralization for a variable listener perspective. As an alternative, we propose and test a technique to interpolate room impulse responses, specifically Ambisonic room impulse responses (ARIRs) available at a grid of spatially distributed receiver perspectives, measured or simulated in a desired acoustic environment. In particular, we extrapolate a triplet of neighboring ARIRs to the variable listener perspective, preceding their linear interpolation. The extrapolation is achieved by decomposing each ARIR into localized sound events and re-assigning their direction, time, and level to what could be observed at the listener perspective, with as much temporal, directional, and perspective context as possible. We propose to undertake this decomposition in two levels: Peaks in the early ARIRs are decomposed into jointly localized sound events, based on time differences of arrival observed in either an ARIR triplet, or all ARIRs observing the direct sound. Sound events that could not be jointly localized are treated as residuals whose less precise localization utilizes direction-of-arrival detection and the estimated time of arrival. For the interpolated rendering, suitable parameter settings are found by evaluating the proposed method in a listening experiment, using both measured and simulated ARIR data sets, under static and time-varying conditions.
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Fursov, V. A. "Constructing a quadratic-exponential FIR-filter with an extended frequency response midrange." Computer Optics 42, no. 2 (July 24, 2018): 297–305. http://dx.doi.org/10.18287/2412-6179-2018-42-2-297-305.
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This article is concerned with synthesizing filter with finite impulse response (FIR-filters) employed to correct radially symmetric distortions such as defocusing. We propose a new parametric class of finite impulse response filters (FIR-filters) based on a model of the one-dimensional radially symmetric frequency response. In the proposed method, the one-dimensional frequency response is composed of quadratic and exponential functions. The two-dimensional impulse response of the filter is constructed by sampling one-dimensional impulse responses for all directions. The development consists in introducing an extended mid-frequency region of the frequency response, thus increasing the contribution of the frequencies to image correction. Examples are given in order to illustrate the possibility of the high-quality distortion correction. In particular, it is shown that the proposed method provides the restoration quality higher than that obtained when using an optimal Wiener filter (taken from OpenCV).
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Lee, Hsiu-Chuan, Chih-Hsiang Hsu, and Cheng-Yi Chien. "Spillovers of international interest rate swap markets and stock market volatility." Managerial Finance 42, no. 10 (October 10, 2016): 943–62. http://dx.doi.org/10.1108/mf-08-2015-0221.
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Purpose The purpose of this paper is to investigate volatility spillovers across the interest rate swap markets of the G7 economies, and then the authors investigate whether spillovers of swap markets contain useful information to explain subsequent stock price movements. Design/methodology/approach This study uses the short- and long-term swap spread volatility of the G7 countries to explore the spillover effects of international swap markets, and then investigates the relationship between swap and stock markets. The authors use the generalized VAR approach suggested by Diebold and Yilmaz (2012) to study spillovers of international swap markets. The Granger-causality tests are employed to examine the linkage of interest rate swap and stock markets. Findings This paper shows that a moderate spillover effect exists for the short- and long-term swap markets. Moreover, the results show that the short- and long-term swap markets of France and Germany have a larger impact on other countries’ swap markets than that of other countries’ swap markets on the French and German swap markets. Finally, the results indicate that the total volatility spillovers for the long-term swap markets have a larger influence on the total volatility spillover index of stock markets and the global stock market volatility than that of the short-term swap markets. Originality/value Prior literature has used impulse response and variance decomposition analyses to investigate international swap markets linkages. However, the results depend on the ordering of variables. This study uses the framework of Diebold and Yilmaz (2012) to overcome the ordering issue, and thus the authors can compute directional spillovers. This paper is the first study to explore the linkage of the total volatility spillover of swap markets and the stock markets.
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Karawani, Kefah, Marzena Bielinska, Joanna Nowosielska-Grygiel, Piotr Pietkiewicz, Krzysztof Kusmierczyk, Katarzyna Kolary, and Jurek Olszewski. "Comparative evaluation of the diagnostic value of the VHIT and Dix-Hallpike test in patients with balance system disorders in out-patient healthcare practice and expertise preparation." Otolaryngologia Polska 72, no. 4 (September 26, 2018): 1–5. http://dx.doi.org/10.5604/01.3001.0012.5421.
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Introduction: The aim of the paper was the comparative analysis of the diagnostic value of the Video Head Impulse Testing (VHIT) Ulmer I and Dix-Hallpike Test in patients with balance system disorders in out-patient practice and expertise preparation. Material and methods: The examination was performed in 63 patients aged 20-79, including 28 women aged 20-72 and 35 men aged 23-79, divided into two groups: Group I (study group) – 33 patients with mixed cause vertigo (on the basis of the Fitzgerald-Hallpike caloric test during the VNG examination), and Group II (reference group) – 30 healthy patients. After the ENT interview and physical examination, exclusion of pathological lesions in the external acoustic meatus and middle ear, each patient was subjected to a Fitzgerald-Hallpike caloric test during VNG examination, as well as a VHIT test and Dix-Hallpike test, with the evaluation of eyeball reaction during head rotation. Results: In the group of patients with mixed-cause vertigo (Group I), the Fitzgerald-Hallpike caloric test showed unilateral labyrinth deficiencies in 90.9% of the patients (with the average value of 41.8%) and relative directional preponderance with the average value of 19.0%, while in 9.1% of the patients, the detected values of labyrinth excitability were normal. In the examination of patients with vertigo, benign paroxysmal positional vertigo was diagnosed in 9.1% of cases. This diagnosis was based on the positive response to the Dix-Hallpike manoeuvre and indicative of damage to the posterior semicircular canal in the VHIT test (without signs of deficiency in the VNG examination). Conclusion: The VHIT test and Dix-Hallpike test enable quick and precise detection of benign paroxysmal positional vertigo in out-patient practice and expertise preparation.
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Dietz, V., G. A. Horstmann, and W. Berger. "Interlimb coordination of leg-muscle activation during perturbation of stance in humans." Journal of Neurophysiology 62, no. 3 (September 1, 1989): 680–93. http://dx.doi.org/10.1152/jn.1989.62.3.680.
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1. Electromyographic (EMG) responses were recorded in both legs, along with corresponding joint movements, after uni- and bilateral perturbations during stance on a treadmill with split belts. Displacements were directed forward, backward, or in opposing directions. They were induced by randomly timed ramp impulses at one of four different rates of treadmill acceleration. 2. Unilateral perturbations directed backward were followed by a bilateral gastrocnemius-EMG response, forward-directed perturbations by a bilateral tibialis anterior-EMG response. The amplitude of these responses was dependent on the rate of treadmill acceleration. Relative to the response of the displaced leg, the amplitude of the EMG response on the nondisplaced side was smaller when a gastrocnemius EMG response was induced, and about equal when the tibialis anterior muscle was activated. The onset latencies were shorter on the displaced side (displaced leg 75-96 ms, non-displaced leg 93-112 ms). 3. Bilateral perturbations in one direction were followed by larger EMG responses in both legs (in the gastrocnemius for backward-directed impulses, in the tibialis anterior for forward-directed impulses). For a given acceleration rate, their amplitude was about equal to the sum of the EMG amplitude of the displaced leg and that of the nondisplaced leg obtained during unilateral displacement. The inverse result was obtained when the legs were simultaneously displaced in opposite directions: EMG responses in both legs were significantly smaller than those obtained after unilateral displacement. 4. It is concluded that a unilateral displacement evokes reflex EMG responses in the synergistic muscles of both legs, which are graded according to the size of the proprioceptive input from the primarily displaced joint. During bilateral displacements, the activity induced by the respective contralateral leg is linearly summed or subtracted, depending on whether the legs are displaced in the same or in opposite directions. In view of the short latencies of these bilateral responses, it would seem that they are mediated by a spinal mechanism. 5. Distinct differences in the behavior of the antagonistic leg muscles were observed: 1) the coactivation of the contralateral leg muscle was significantly smaller when the gastrocnemius was stretched unilaterally, whereas it was about equal for the tibialis anterior; and 2) the gastrocnemius EMG responses were closely correlated with the displacement velocity, whereas the tibialis anterior response was more closely correlated with acceleration, i.e., the tibialis anterior response was more dynamic in nature.(ABSTRACT TRUNCATED AT 400 WORDS)
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Leys, S. P., and R. W. Meech. "Physiology of coordination in sponges." Canadian Journal of Zoology 84, no. 2 (February 1, 2006): 288–306. http://dx.doi.org/10.1139/z05-171.
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All multicellular organisms need a means of communicating between cells and between regions of the body. The evolution of a nervous system, by the Cnidaria, provided a fast means of communication and enabled the colonization of rapidly changing environments. Sponges, the descendants of the first multicellular animals, lack nerves but nevertheless have a number of different systems that allow coordinated behaviour, albeit rather slow coordinated behaviour. It is from elements within these systems that the origins of the nervous and endocrine systems, the grand organizing principles of higher animals, seem likely to have appeared. Electrical activity has not been found in cellular sponges, yet local contractions are elicited in response to a variety of stimuli and, in some cases, contractions propagate across the body to control the hydrodynamics of the feeding current. The mechanism of propagation is thought to involve hormones or a combination of other signaling molecules and direct mechanical action of one cell on the next, leading to increased intracellular calcium. In other instances cellular sponges respond to stress, such as heat shock, by elevating intracellular calcium by way of second messengers such as cyclic ADP-ribose. Electrical communication, well known in plants and protists, was first demonstrated in a sponge in 1997. Hexactinellids (glass sponges), which arrest their feeding current within 20 s of mechanical or electrical stimulation, do so via an electrical impulse that propagates through syncytial tissues. These unusual syncytial tissues are cytoplasmically coupled from outside to inside and top to bottom so that there are no membrane boundaries to impede the electrical currents. Pharmacological tests suggest that Ca2+, rather than Na+, drives the action potential. The conduction velocity is slow (0.27 cm·s–1) and is highly temperature sensitive (Q10 ~3). At present, glass sponges are the only poriferans known to have propagated electrical signals. In addition, reports of directional swimming in sponge larvae, of the rapid and coordinated changes in the tensile strength of the extracellular matrix in Chondrosia Nardo, 1847, and of the rapid closure of ostia of some cellular sponges in response to mechanical stimuli further illustrate the variety of coordinating mechanisms that evolved in the Porifera in the absence of a nervous system.
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Adedoyin, Festus Fatai, and Festus Victor Bekun. "Modelling the interaction between tourism, energy consumption, pollutant emissions and urbanization: renewed evidence from panel VAR." Environmental Science and Pollution Research 27, no. 31 (July 7, 2020): 38881–900. http://dx.doi.org/10.1007/s11356-020-09869-9.
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Abstract In less than two decades, the global tourism industry has overtaken the construction industry as one of the biggest polluters, accounting for up to 8% of global greenhouse gas emissions as reported by the United National World Trade Organization (UNWTO 2018). This position resonates the consensus of the United Nations Framework Convention on Climate Change (UNFCCC). Consequently, research into the causal link between emissions and the tourism industry has increased significantly focusing extensively on top earners from the industry. However, few studies have thoroughly assessed this relationship for small island economies that are highly dependent on tourism. Hence, this study assessed the causal relationship between CO2 emissions, real GDP per capita (RGDP) and the tourism industry. The analysis is conducted for seven tourism-dependent countries for the period 1995 to 2014 using panel VAR approach, with support from fully modified ordinary least square and pooled mean group–autoregressive distributed lag models. Unit root tests confirm that all variables are stationary at first difference. Our VAR Granger causality/block exogeneity Wald test results show a unidirectional causality flowing from tourism to CO2 emission, RGDP and energy consumption, but a bi-directional causality exists between tourism and urbanization. This implies that in countries that depend on tourism, the behaviour of CO2 emission, RGDP and energy consumption can be predicted by the volume of tourist arrivals, but not the other way around. The impulse response analysis also shows that the responses of tourism to shocks in CO2 appear negative within the 1st year, positive within the 2nd and 3rd years but revert to equilibrium in the fourth year. Finally, the reaction of tourism to shocks in energy consumption is similar to its reaction to shocks in RGDP. Tourism responds positively to shocks in urbanization throughout the periods. These outcomes were resonated by the Dumitrescu and Hurlin causality analysis where the growth-induced tourism hypothesis is validated as well as feedback causality observed between tourism and pollutant emission and urbanization and pollutant emission in the blocks over the sampled period. Consequently, this study draws pertinent energy and tourism policy implications for sustainable tourism on the panel over their growth trajectory without compromise for green environment.
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Massé, Pierre, Thibaut Carpentier, Olivier Warusfel, and Markus Noisternig. "Denoising Directional Room Impulse Responses with Spatially Anisotropic Late Reverberation Tails." Applied Sciences 10, no. 3 (February 4, 2020): 1033. http://dx.doi.org/10.3390/app10031033.
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Directional room impulse responses (DRIR) measured with spherical microphone arrays (SMA) enable the reproduction of room reverberation effects on three-dimensional surround-sound systems (e.g., Higher-Order Ambisonics) through multichannel convolution. However, such measurements inevitably contain a nondecaying noise floor that may produce an audible “infinite reverberation effect” upon convolution. If the late reverberation tail can be considered a diffuse field before reaching the noise floor, the latter may be removed and replaced with an extension of the exponentially-decaying tail synthesized as a zero-mean Gaussian noise. This has previously been shown to preserve the diffuse-field properties of the late reverberation tail when performed in the spherical harmonic domain (SHD). In this paper, we show that in the case of highly anisotropic yet incoherent late fields, the spatial symmetry of the spherical harmonics is not conducive to preserving the energy distribution of the reverberation tail. To remedy this, we propose denoising in an optimized spatial domain obtained by plane-wave decomposition (PWD), and demonstrate that this method equally preserves the incoherence of the late reverberation field.
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Puomio, Otto, Nils Meyer-Kahlen, and Tapio Lokki. "Locating Image Sources from Multiple Spatial Room Impulse Responses." Applied Sciences 11, no. 6 (March 10, 2021): 2485. http://dx.doi.org/10.3390/app11062485.
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Measured spatial room impulse responses have been used to compare acoustic spaces. One way to analyze and render such responses is to apply parametric methods, yet those methods have been bound to single measurement locations. This paper introduces a method that locates image sources from spatial room impulse responses measured at multiple source and receiver positions. The method aligns the measurements to a common coordinate frame and groups stable direction-of-arrival estimates to find image source positions. The performance of the method is validated with three case studies—one small room and two concert halls. The studies show that the method is able to locate the most prominent image sources even in complex spaces, providing new insights into available Spatial Room Impulse Response (SRIR) data and a starting point for six degrees of freedom (6DoF) acoustic rendering.
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Wylie, Scott A., Daniel O. Claassen, Hilde M. Huizenga, Kerilyn D. Schewel, K. Richard Ridderinkhof, Theodore R. Bashore, and Wery P. M. van den Wildenberg. "Dopamine Agonists and the Suppression of Impulsive Motor Actions in Parkinson Disease." Journal of Cognitive Neuroscience 24, no. 8 (August 2012): 1709–24. http://dx.doi.org/10.1162/jocn_a_00241.
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The suppression of spontaneous motor impulses is an essential facet of cognitive control that is linked to frontal-BG circuitry. BG dysfunction caused by Parkinson disease (PD) disrupts the proficiency of action suppression, but how pharmacotherapy for PD impacts impulsive motor control is poorly understood. Dopamine agonists improve motor symptoms of PD but can also provoke impulsive–compulsive behaviors (ICB). We investigated whether dopamine agonist medication has a beneficial or detrimental effect on impulsive action control in 38 PD patients, half of whom had current ICB. Participants performed the Simon conflict task, which measures susceptibility to acting on spontaneous action impulses as well as the proficiency of suppressing these impulses. Compared with an off-agonist state, patients on their agonists were no more susceptible to reacting impulsively but were less proficient at suppressing the interference from the activation of impulsive actions. Importantly, agonist effects depended on baseline performance in the off-agonist state; more proficient suppressors off agonist experienced a reduction in suppression on agonist, whereas less-proficient suppressors off agonist showed improved suppression on agonist. Patients with active ICB were actually less susceptible to making fast, impulsive response errors than patients without ICB, suggesting that behavioral problems in this subset of patients may be less related to impulsivity in motor control. Our findings provide further evidence that dopamine agonist medication impacts specific cognitive control processes and that the direction of its effects depends on individual differences in performance off medication.
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Aw, S. T., G. M. Halmagyi, R. A. Black, I. S. Curthoys, R. A. Yavor, and M. J. Todd. "Head impulses reveal loss of individual semicircular canal function." Journal of Vestibular Research 9, no. 3 (June 1, 1999): 173–80. http://dx.doi.org/10.3233/ves-1999-9304.
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We studied individual semicircular canal responses in three dimensions to high-acceleration head rotations (“head impulses”) in subjects with known surgical lesions of the semicircular canals, and compared their results to those of normal subjects. We found that vestibular-ocular reflex (VOR) gains at close to peak head velocity in response to yaw, pitch and roll impulses were reliable indicators of semicircular canal function. When compared to normals, lateral canal function showed a 70–80% gain at peak of yaw head velocity during ipsilesional yaw impulses. After the loss of one vertical canal function there was a 30–50% and torsional VOR gain in response to ipsilesional pitch and roll impulses respectively. Bilateral deficits in anterior or posterior canal function resulted in a 80–90% impulses, while the loss of ipsilateral anterior and posterior canal functions will result in a 80–90% ipsilesional roll impulses. Three-dimensional vector analysis and animation of the VOR responses in a unilateral vestibular deafferented subject to yaw, pitch and roll impulses further demonstrated the deficits in magnitude and direction of the VOR responses following the loss of unilateral lateral, anterior and posterior canal functions.