Source Width Research Articles

Auditory Distance Control Using a Variable-Directivity Loudspeaker

The directivity of a sound source in a room influences the D/R ratio and thus the auditory distance. This study proposes various third-order beampattern pattern designs for a precise control of the D/R ratio. A comprehensive experimental study is conducted to investigate the hereby achieved effect on the auditory distance. Our first experiment auralizes the directivity variations using a virtual directional sound source in a virtual room using playback by a 24-channel loudspeaker ring. The experiment moreover shows the influence of room, source-listener distance, signal, and additional single-channel reverberation on the auditory distance. We verify the practical applicability of all the proposed beampattern pattern designs in a second experiment using a variable-directivity sound source in a real room. Predictions of experimental results are made with high accuracy, using room acoustical measures that typically predict the apparent source width.

Neutral-helium-atom diffraction from a micron-scale periodic structure: Photonic-crystal-membrane characterization

Surface scattering of neutral helium beams created by supersonic expansion is an established technique for measuring structural and dynamical properties of surfaces on the atomic scale. Helium beams have also been used in Fraunhofer and Fresnel diffraction experiments. Due to the short wavelength of the atom beams of typically 0.1nm or less, Fraunhofer diffraction experiments in transmission have so far been limited to grating structures with a period (pitch) of up to 200nm. However, larger periods are of interest for several applications, for example for the characterization of photonic crystal membrane structures, where the period is typically in the micron/high sub-micron range. Here we present helium atom diffraction measurements of a photonic crystal membrane structure with a two dimensional square lattice of 100x100 circular holes. The nominal period and hole radius were 490nm and 100nm respectively. To our knowledge this is the largest period that has ever been measured with helium diffraction. The helium diffraction measurements are interpreted using a model based on the helium beam characteristics. It is demonstrated how to successfully extract values from the experimental data for the average period of the grating, the hole diameter and the width of the virtual source used to model the helium beam.

Improved analytical model of surface potential with modified boundary conditions for double gate tunnel FETs

In this paper, an improved analytical model of the channel surface potential in the tunnel field effect transistors is established with modified boundary conditions considering the source and drain depletion widths, avoiding the deviation of the channel potential and the overestimate on the electric field. Based on the proposed surface potential model, the threshold voltage model is also developed with the transconductance change method. The influences of the channel and oxide structures on surface potential and threshold voltage are investigated. The good agreement is obtained by the comparison of the modeling results with the numerical simulation results, verifying the validation of the proposed model, and it also implied that this model will be helpful for the further investigation of TFETs.

Spatial perception in binaural reproduction with sparse head-related transfer function measurement grids

Growing interest in virtual reality has led to greater demand for immersive virtual audio systems. High fidelity spatial audio requires individualized head related transfer functions (HRTFs). Individualized HRTFs are, however, typically unavailable as they require specialized equipment and a large number of measurements. This motivates the development of a simpler more accessible HRTF estimation process. Previous work has demonstrated that spherical-harmonics (SH) can be used to reconstruct the HRTF from a smaller number of sample points, but this method has two known types of error: spatial aliasing and truncation error. Aliasing refer to loss of ability to represent high frequencies. Truncation error refer to the fact the SH representation will be order-limited which further limits spatial resolution. In this paper, the effect of sparse measurement grids on the reproduced binaural signal is studied by analyzing both types of errors. The expected effect of these errors on the perceived location, externalization and source width, is studied using a theoretical model and an experimental investigation. Preliminary results indicate relatively large effects of SH order on sound localization and smaller effects due to aliasing errors.

Analysis on decorrelation effect of audio signal in multichannel reproduction

Decorrelation of audio signal is a process that generates two or more incoherent signals from a single input signal, which has many applications in artificial auditory effects, such as broadening the apparent source width (ASW), enhancing the subjective envelopment, producing subjective diffusion in multichannel reproduction, etc. Frequently used decorrelation method is convoluting audio signal with random (or pseudo-random) noise. In this work, we focus on the relationship of reproduction zone of multichannel reproduction with decorrelation degree. Simulation calculation result show that, by changing the decorrelation degree which is measured by the interaural cross-correlation coefficients (IACC) of reproduced signals, the timbre will change when move off the listening center. Listening zone with small timbre deviation (for example, binaural loudness spectra less than 1dB/ERB) relative to center position increase with the value of IACC decrease. But as well known, for good subjective diffusion, the least IACC value does not mean the best effect. There exit a best IACC value range from 0.2~0.4 for different audio signal. Adapting a best IACC value, a reproduction zone across different frequencies can be achieved.

Correlated imaging with partially coherent light for remote sensing

Based on the extended Huygens–Fresnel integral and the theory of coherence of light field, we have investigated the correlated imaging by using the transverse normalized second-order intensity fluctuation correlation function with partially coherent light radiation. The imaging for a reflected object with relative long distance is determined by the feature of speckle-to-speckle correlation. By using the correlation function, we study the effects of imaging distance, the sizes of object lens and reference lens, the source’s transverse coherent width and its transverse size on the quality of correlated imaging. Numerical results show that the parameters of imaging system and the properties of partially coherent light source have significant influences on the imaging resolution and visibility. For an object lens with large enough diameter, the resolution is determined by the transverse coherent width of light source. On the contrary, it depends on the aperture of object lens. The magnification of the system depends only on the propagation distance. This speckle-to-speckle correlated imaging with unbalanced arms have potential applications in remote sensing due to its unique features.

Influence of the neutron transport tube on neutron resonance densitometry

Neutron Resonance Densitometry (NRD) is a non-destructive assay technique of nuclear materials in particle-like debris that contains various materials. An aim of NRD is to quantify nuclear materials in a melting fuel of Fukusima Daiichi plant, spent nuclear fuel and annihilation disposal fuel etc. NRD consists of two techniques of Neutron Resonance Transmission Analysis (NRTA) and Neutron Resonance Capture Analysis (NRCA) or Prompt Gamma-ray Analysis (PGA). A density of nuclear material isotopes is decided with NRTA. The materials absorbing a neutron in a wide energy range such as boron in a sample are identified by NRCA/PGA. The information of NRCA/PGA is used in NRTA analysis to quantify nuclear material isotopes. A neutron time of flight (TOF) method is used in NRD measurements. A facility, consisting of a neutron source, a neutron flight path, and a detector is required. A short flight path and a strong neutron source are needed to downsize such a facility and put NRD into practical use. A neutron transport tube covers a flight path to prevent noises. In order to investigate the effect of neutron transport tube and pulse width of a neutron source, we carried out NRTA experiments with a 2-m short neutron transport tube constructed at Kyoto University Research Reactor Institute - Linear Accelerator (KURRI-LINAC), and impacts of shield of neutron transport tube and influence of pulse width of a neutron source were examined. A shield of the neutron transport tube reduced a background and had a good influence on the measurement. The resonance dips of 183 W at 27 eV was successfully observed with a pulse width of a neutron source less than 2 μs.

Wavelet transform in the application of three-dimensional terahertz imaging for internal defect detection

Spatial resolution and spectral contrast are two major bottlenecks for non-destructive testing of complex samples with current imaging technologies. We use a three-dimensional terahertz (THz) imaging system to obtain the internal structure of the sample, and exploit the wavelet transform algorithm to improve the spatial resolution and the spectral contrast. With this method, the longitudinal resolution of terahertz imaging system can be improved to the wavelength comparable thickness, while the x-y plane resolution can be as high as 0.2 mm0.2 mm, which benefits from the point-to-point scanning on the x-y plane. In this three-dimensional terahertz imaging system, the Syn View Head 300 with light source/detector frequency of 0.3 THz is used for two-dimensional scanning (x-y direction) of the sample, and the linear frequency modulated continuous wave technique is used to obtain the reflected terahertz light intensity at different depths (z axis) of the sample. When the sample is thin, the upper and lower interface reflection peaks are difficult to distinguish due to broad peak width of the THz source. To solve this problem efficiently, continuous wavelet transform (CWT) is used. In recent years, CWT is applied widely because of its particular mathematical properties in the feature signal recognition. Since the Gaus2 wavelet basis is better to highlight the peak signal, we choose it for CWT. After CWT, one scale of the wavelet coefficients is chosen for three-dimensional data reconstruction, for which the widths of the reflection peaks are narrower and the noise signals are weaker. That means if we reconstruct the three-dimensional wavelet coefficient data on the chosen scale, the three-dimensional image of the tested sample will be enhanced. In order to demonstrate that, the three-dimensional images reconstructed by wavelet coefficients are compared with those by original data. The tested sample has holes inside with different depths. Based on the original three-dimensional THz image, it is hard to locate the top of 4 mm deep hole (1 mm deep photosensitive material plate), while the top of the inner 4 mm deep holes (the bottom of the 1 mm deep photosensitive material plate) can be distinctly located and the noises are greatly reduced based on the three-dimensional images reconstructed by wavelet coefficients. With this method, the longitudinal resolution of terahertz detection systems can be improved to 1 mm that is comparable to the wavelength, which demonstrates advantages of this method.

Effects of Model Reduction on Simulated Temperature Fields in Milling

Temperature fields generated in machining processes affect, among other internal material loads, the material modifications in the workpiece surface layer and therefore influence the functional performance of the final component. In particular this might become critical for multipass machining where the amount of heat in the workpiece is accumulated with every path and layer being cut. In the present work a finite element modelling approach for the milling of a complete steel plate is proposed that minimizes computation time while providing a reasonable accuracy of predicted temperature fields. The milling process is modelled as a moving heat source taking into account material removal. Computation time can be reduced up to 98% by systematically increasing the width of the material removal and the heat source width. The effects of the model reduction regarding the temperature fields are investigated in comparison to a reference simulation and furthermore to experiments.

Simulation of Nano Fluid Flow and Natural Convection Heat Transfer in an Incinerator Shaped Cavity Containing a Heated Block

The present work reports a numerical investigation of characteristic convection in an incinerator molded nook with a limited warmed source arranged at the base. Grid Boltzmann Method (LBM) is utilized to reproduce Nano liquid (water-Al2O3) stream and warmth exchange. Reproductions have been completed for the relevant parameters: Rayleigh number (Ra=103-106), relative warmth source high (0 ≤ δ ≤ 0.5), and relative warmth source width (e=0.02-0.8). The correlation of the acquired outcomes is in amazing concurrence with results from writing. I might be noticed that the increments of the Rayleigh number (Ra=103-106), the strong volume portion, and the warmth source stature (δ=0.1-0.5) improve the warmth exchange and impacts the stream design and the warm structures and the warmth exchange rate measured by the Nusselt number. However for the relative warmth source width (e=0.02-0.8), it assumes inverse part for qualities better than 0.4.

Crystallization of Iron Nanostructures with Secondary‐Laser‐Assisted Pulsed Laser Ablation

SUMMARYIn this paper, we have investigated the growth technique of graphite‐coated nanomagnet particles to apply a sustainable environment technology by millisecond YAG pulsed laser ablation (PLA) method in ethanol solution using Fe bulk target. To control crystallized forms and/or grain size of nanomagnet materials, laser diode (LD) beam was irradiated to the ablation plumes, which were generated by this PLA method. In addition, magnetic field was applied to the ablation plumes, in order to separate a nanomagnet particle and a nonmagnet one. Ablation plumes were observed by high‐speed camera images, and they were reexcited by LD laser beam irradiation. In the case of magnetic field assist, ablation plumes were attracted to the magnet. This suggested that growth nanoparticles had magnetic property. Typical carbon‐coated nanoparticles, which grown by nonassisted PLA, were observed by TEM images, and these grain sizes were dependent on the pulsed width of PLA source. On the other hand, LD‐assisted samples showed there were rod‐sharped nanomaterials, and crystallization of these materials was β‐Fe3O4, γ‐Fe2O3 surmised by electron diffraction.

Efficacy of a new spatial ear training program for “Ensemble width” and “Individual source width”

The authors have devised a matching-based training paradigm that assists listeners in evaluating spatial width of a reproduced sound field with increased sensitivity and memory. The program uses a learning paradigm of repeated comparison and match to references. All sound sources were horizontally spread using a pairwise constant power panning law over front five loudspeakers located at + -60, + -30, and 0 degree. Trainees were asked to adjust a parameter controlling the panning intervals of five-channel sound sources until it matched to the perceived width of a given reference. The program provided visual feedback for isomorphic mapping. To make the training equipment more accessible, the headphone version of the program was also developed using a simulation of listener and sound sources positions in a room. Thirty participants were divided into three groups: a group with loudspeaker-based training, a group with headphone-based training, and a group without training. Participants in the trained groups to...

Creating von Laue patterns in crystal scattering with partially coherent sources

When spatially coherent radiation is diffracted by a crystalline object, the field is scattered in specific directions, giving rise to so-called von Laue patterns. We examine the role of spatial coherence in this process. Using the first-order Born approximation, a general analytic expression for the far-zone spectral density of the scattered field is obtained. This equation relates the coherence properties of the source to the angular distribution of the scattered intensity. We apply this result to two types of sources. Quasihomogeneous Gaussian Schell-model sources are found to produce von Laue spots whose size is governed by the effective source width. Delta-correlated ring sources produce von Laue rings and ellipses instead of point-like spots. In forward scattering, polychromatic ellipses are created, whereas in backscattering striking, overlapping ring patterns are formed. We show that both the directionality and the wavelength-selectivity of the scattering process can be controlled by the state of coherence of the illuminating source.

Study of the Effect of the Pulse Width of the Excitation Source on the Two-Photon Absorption and Two-Photon Circular Dichroism Spectra of Biaryl Derivatives.

Herein we report on the expanded theoretical calculations and the experimental measurements of the two-photon absorption (TPA) and two-photon circular dichroism (TPCD) spectra of a series of optically active biaryl derivatives (R-BINOL, R-VANOL, and R-VAPOL) using femtosecond pulses. The comparative analysis of the experimental TPCD spectra obtained with our tunable amplified femtosecond system with those previously measured in our group on the same series of compounds in the picosecond regime reveals a decrease in the amplitude of the signal and an improvement in matching with the theory in the former. These results can be explained based on the negligible contribution of excited state absorption (ESA) using femtosecond pulses compared to the picosecond regime. We show how ESA affects both the strength of the signal and the shape of the TPA and TPCD spectra. TPA and TPCD spectra were obtained using the double L-scan technique over a broad spectral range (450-750 nm) using 90 fs pulses at 50 Hz repetition rate produced by an amplified femtosecond system. The theoretical calculations were performed using modern analytical response theory within the time-dependent density functional theory (TD-DFT) approach using CAM-B3LYP and 6-311++G(d,p) basis sets.

Calibration of the OHREX high-resolution imaging crystal spectrometer at the Livermore electron beam ion traps.

We report the calibration of the Orion High-Resolution X-ray (OHREX) imaging crystal spectrometer at the EBIT-I electron beam ion trap at Livermore. Two such instruments, dubbed OHREX-1 and OHREX-2, are fielded for plasma diagnostics at the Orion laser facility in the United Kingdom. The OHREX spectrometer can simultaneously house two spherically bent crystals with a radius of curvature of r = 67.2 cm. The focusing properties of the spectrometer allow both for larger distance to the source due to the increase in collected light and for observation of extended sources. OHREX is designed to cover a 2.5°-3° spectral range at Bragg angles around 51.3°. The typically high resolving powers at these large Bragg angles are ideally suited for line shape diagnostics. For instance, the nominal resolving power of the instrument (>10 000) is much higher than the effective resolving power associated with the Doppler broadening due to the temperature of the trapped ions in EBIT-I. The effective resolving power is only around 3000 at typical EBIT-I conditions, which nevertheless is sufficient to set up and test the instrument's spectral characteristics. We have calibrated the spectral range for a number of crystals using well known reference lines in the first and second order and derived the ion temperatures from these lines. We have also made use of the 50 μm size of the EBIT-I source width to characterize the spatial focusing of the spectrometer.

Vegetative Filter Strip (Vfs) Applications for Runoff and Pollution Management in the Saemangeum Area of Korea

AbstractThis study was conducted to develop a vegetative filter strip (VFS) technique to manage agricultural non‐point source (NPS) pollution in the region in Korea. The experimental plots were constructed with two different sizes and slopes in the uplands within the Saemangeum Basin. The soil type of the study area was classified as loam with NRCS hydrologic soil type B, and showed typical upland soil characteristics. The rainfall–runoff relationships and NPS pollution reduction effects of the VFS were assessed, and the total cost of VFS application was estimated. It was noted that runoff reduction effects ranged from 14.1 to 69.3%, and NPS pollution reduction effects were 9.8–94.2% in suspended solid (SS), 24.0–73.3% in total nitrogen (T‐N) and 47.6–80.9% in total phosphorus (T–P) from the VFS plots. The variations of VFS effects were caused by various factors including size and slope of the source area, cover ratio and width of VFS, as well as rainfall characteristics. The total VFS application cost was estimated to be approximately US$3390 ha−1 yr.−1, considering the costs for construction and maintenance of the VFS system and the loss of benefit caused by giving up crop cultivation in the area needed for VFS construction. Copyright © 2016 John Wiley & Sons, Ltd.

The Effects of Rotation and River Discharge on Net Mixing in Small-Mouth Kelvin Number Plumes

AbstractSmall-mouth Kelvin number plumes, or plumes with a source width smaller than the deformation radius, are characterized by near-field plume regions of rapid lateral expansion and strong vertical mixing. Net plume mixing, or the dilution of a plume by ocean water between the estuary mouth and the far-field plume, is examined using idealized numerical experiments with the Regional Ocean Modeling System (ROMS). The density anomaly of plume water entering the far field is determined from isohaline analysis of the modeled salinity field. The experiments indicate that when estuarine discharge increases, net plume mixing decreases in a rotating environment but increases in a nonrotating environment. Scaling analysis supports that this opposite trend in behavior is related to rotation turning the plume, limiting the lateral expansion and suppressing shear mixing. The results of this study explain different trends in net plume mixing reported in previous studies and compare favorably to observations of the Fraser River plume.

Rapid dike intrusion into Sakurajima volcano on August 15, 2015, as detected by multi-parameter ground deformation observations

We present observations of ground deformation at Sakurajima in August 2015 and model the deformation using a combination of GNSS, tilt and strain data in order to interpret a rapid deformation event on August 15, 2015. The pattern of horizontal displacement during the period from August 14 to 16, 2015, shows a WNW–ESE extension, which suggests the opening of a dike. Using a genetic algorithm, we obtained the position, dip, strike length, width and opening of a dislocation source based on the combined data. A nearly vertical dike with a NNE–SSW strike was found at a depth of 1.0 km below sea level beneath the Showa crater. The length and width are 2.3 and 0.6 km, respectively, and a dike opening of 1.97 m yields a volume increase of 2.7 × 106 m3. 887 volcano-tectonic (VT) earthquakes beside the dike suggest that the rapid opening of the dike caused an accumulation of strain in the surrounding rocks, and the VT earthquakes were generated to release this strain. Half of the total amount of deformation was concentrated between 10:27 and 11:54 on August 15. It is estimated that the magma intrusion rate was 1 × 106 m3/h during this period. This is 200 times larger than the magma intrusion rate prior to one of the biggest eruptions at the summit crater of Minami-dake on July 24, 2012, and 2200 times larger than the average magma intrusion rate during the period from October 2011 to March 2012. The previous Mogi-type ground deformation is considered to be a process of magma accumulation in preexisting spherical reservoirs. Conversely, the August 2015 event was a dike intrusion and occurred in a different location to the preexisting reservoirs. The direction of the opening of the dike coincides with the T-axes and direction of faults creating a graben structure.

How reproducible are psychoacoustic listening tests on spatial impression in auditoria?

In three psychoacoustic experiments, it was shown that changes in frequency (pitch) and level (loudness) of stimuli lead to significant differences in the perception of apparent source width (ASW). Due to partially identical test conditions in two of the experiments, it is possible to analyze the collected data in regard to stability of ASW perception over repeated testing sessions and to study inter-individual differences. This analysis shows that intra-individual effects of stimulus loudness and pitch are consistent across participants, whereas the absolute level of ASW perception varies between individuals and between experimental sessions. Using this data, possible influences such as listener training effect over repetition of test sessions are discussed. The presented results provide insights into possible improvements of investigating ASW in future studies.

First principles fluid modelling of magnetic island stabilization by electron cyclotron current drive (ECCD)

Tearing modes are MagnetoHydroDynamics (MHD) instabilities that reduce the performance of fusion devices. They can however be controlled and suppressed using electron cyclotron current drive (ECCD) as demonstrated in various tokamaks. In this work, simulations of island stabilization by ECCD-driven current have been carried out using the toroidal nonlinear 3D full MHD code xtor-2f, in which a current source term modeling the ECCD has been implemented. The efficiency parameter, , has been computed and its variations with respect to source width and location were also computed. The influence of parameters such as current intensity, source width and position with respect to the island was evaluated and compared to the modified Rutherford equation. We retrieved a good agreement between the simulations and the analytical predictions concerning the variations of control efficiency with source width and position. We also show that the 3D nature of the current source term can lead to the onset of an island if the source term is precisely applied on a rational surface. We report the observation of a flip phenomenon in which the O- and X-points of the island rapidly switch their position in order for the island to take advantage of the current drive to grow.