Search results for: sound absorption coefficients

Authors: J. Shiri, A. Mansourizadeh, F. Faghih, H. Vaez

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In this study, porous polyvinylidene fluoride (PVDF) hollow fiber membranes are fabricated via a wet phase-inversion Process and used in the gas–liquid membrane contactor for physical CO2 absorption. Effect of different air gap on the structure and CO2 flux of the membrane was investigated. The hollow fibers were prepared using the wet spinning process using a dope solution containing PVDF/NMP/Licl (18%, 78%, 4%) at the extrusion rate of 4.5ml/min and air gaps of 0, 7, 15cm. Water was used as internal and external coagulants. Membranes were characterized using various techniques such as Field Emission Scanning Electron Microscopy (FESEM), Gas permeation test, Critical Water Entry Pressure (CEPw) to select the best membrane structure for Co2 absorption. The characterization results showed that the prepared membrane at which air gap possess small pore size with high surface porosity and wetting resistance, which are favorable for gas absorption application air gap increased, CEPw had a decrease, but the N2 permeation was decreased. Surface porosity and also Co2 absorption was increased.

Keywords: porous PVDF hollow fiber membrane, CO2 absorption, phase inversion, air gap

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Authors: Grzegorz Dolzyk, Sungmoon Jung

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Thin-walled tubes are commonly used as energy absorption devices for their excellent mechanical properties and high manufacturability. Techniques such as grooving and pre-folded origami shapes were introduced to circular and polygonal tubes to improve its energy absorption efficiency. This paper examines the energy absorption characteristics of circular tubes with pre-embedded curved-crease pattern. Set of numerical analyzes were conducted with different grooving patterns for tubes with various diameter (D) to thickness (t) ratio. It has been found that even very shallow grooving can positively affect thin wall tubes, leading to increased energy absorption and higher crushing load efficiency. The phenomenon is associated with nonsymmetric deformation that is usually observed for tubes with a high D/t ratio ( > 90). Grooving can redirect a natural mode of post-buckling deformation to a one with a higher number of lobes such that its beneficial and more stable. Also, the opposite effect can be achieved, and highly disrupted deformation can be a cause of reduced energy absorption capabilities. Curved-crease engraved patterns can be used to stabilize and change a form of hazardous post-buckling deformation.

Keywords: axial crushing, energy absorption, grooving, thin-wall structures

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Authors: Ashwani Kumar

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In human beings, eyes play a vital role. A very less research has been done for rehabilitation of blindness for the blind people. This paper discusses the work that helps blind people for recognizing the basic shapes of the objects like circle, square, triangle, horizontal lines, vertical lines, diagonal lines and the wave forms like sinusoidal, square, triangular etc. This is largely achieved by using a digital camera, which is used to capture the visual information present in front of the blind person and a software program, which achieves the image processing operations, and finally the processed image is converted into sound. After the sound generation process, the generated sound is fed to the blind person through headphones for visualizing the imaginary image of the object. For visualizing the imaginary image of the object, it needs to train the blind person. Various training process methods had been applied for recognizing the object.

Keywords: image processing, pixel, pitch, loudness, sound generation, edge detection, brightness

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Authors: Anbang Liu, Huaqing Xie, Zihua Wu, Xiaoxiao Yu, Yuanyuan Wang

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Due to the temperature-dependence and mutual coupling of thermoelectric parameters, the Thomson effect always exists, which is derived from temperature gradients during thermoelectric conversion. The synergistic effect between the Thomson effect and non-equilibrium heat transport of charge carriers leads to local heat absorption or release in thermoelements, thereby affecting its power generation performance and conversion efficiency. This study verified and analyzed the influence and mechanism of the Thomson effect on N-type skutterudite thermoelement through quasi-steady state testing under approximate vacuum conditions. The results indicate the temperature rise/fall of N-type thermoelement at any position is affected by Thomson heat release/absorption. Correspondingly, the Thomson effect also contributes advantageously/disadvantageously to the output power of N-type skutterudite thermoelement when the Thomson coefficients are positive/negative. In this work, the output power can be promoted or decreased maximally by more than 27% due to the presence of Thomson heat when the absolute value of the Thomson coefficient is around 36 μV/℃.

Keywords: Thomson effect, heat transport, thermoelectric conversion, numerical simulation

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Authors: Syrine Bassi

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Sound symbolism has been able to give us an exciting new tool to target consumers’ brand perception. It acts on a subconscious level making them less likely to reject the implicit message delivered by the sound of the brand name. Most of the research conducted in the field was focused on the English language as it is the language used for international branding campaigns and global companies. However, more research is examining the sound symbolism in other languages and comparing it to the English language findings. Besides, researchers have been able to study luxury brand names and spot out the patterns used in them to provoke luxury and sophistication. It stands to a reason to connect the luxury brand names and the local language’s sound effects since a considerable number of these brands are promoting the origin of the Maison, therefore, have names in foreign languages. This study was established around the Hungarian luxury brand names. It aims to spot out the patterns used in these names that connect to the previous findings of luxury sound effects and also the differences. We worked with a non-Hungarian speaking sample who had some basic knowledge of the language just to make sure they were able to correctly pronounce the names. The results have shown both similarities and differences when it comes to perceiving luxury based on the brand name. As the Hungarian language can be qualified as a saturated language, consonant wise, it was easy to feed the luxury feeling only by using designers' names, however, some complicated names were too difficult and repulsive to consider as luxurious. On the other hand, oversimplifying some names did not convey the desired image as it was too simple and easy. Overall, some sounds have been proved to be linked to luxury as the literature suggests, the difficulty of pronunciation has also proved effective since it highlights the distant feeling consumers crave when looking for luxury. These results suggest that sound symbolism can set up an aura of luxury when used properly, leveraging each languages’ convenient assets.

Keywords: hungarian language, linguistics, luxury brands, sound symbolism

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Authors: Marine Segui, Ruxandra Mihaela Botez

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OpenVSP is an aerodynamic solver developed by National Aeronautics and Space Administration (NASA) that allows building a reliable model of an aircraft. This software performs an aerodynamic simulation according to the angle of attack of the aircraft makes between the incoming airstream, and its speed. A reliable aerodynamic model of the Cessna Citation X was designed but it required a lot of computation time. As a consequence, a prediction method was established that allowed predicting lift and drag coefficients for all Mach numbers and for all angles of attack, exclusively for stall conditions, from a computation of three angles of attack and only one Mach number. Aerodynamic coefficients given by the prediction method for a Cessna Citation X model were finally compared with aerodynamics coefficients obtained using a complete OpenVSP study.

Keywords: aerodynamic, coefficient, cruise, improving, longitudinal, openVSP, solver, time

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Authors: Neetu Malik, Sharad Shrivastava, Subrata Bandhu Ghosh

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Biocomposite materials were fabricated using mixing biodegradable polymer polycaprolactone (PCL) and Thermally Exfoliated Graphene Oxide (TEGO) through solution casting. Various samples of biocomposite films were prepared by varying the TEGO wt% composition by 0.1%, 0.5%, 1% and 1.5%. Thereafter, the density and water absorption of the composites were investigated with respect to immersion time in water. The moisture absorption results show that with an increase in weight percentage (from 0.1 to wt 1.5%) of TEGO within the biopolymer films, the absorption value of bio-nanocomposite films reduced rapidly from 27.4% to 14.3%. The density of hybrid composites also increased with increase in weight percentage of TEGO. These results indicate that the optimized composition of constituents in composite membrane could effectively reduce the anhydrous conditions of bio-composite film.

Keywords: thermally exfoliated graphene oxide, PCL, water absorption, density

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Authors: I. Wardana Ketut, I. Suparwa Nyoman

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This study investigated the form and characteristic of speech sound produced by three Balinese subjects who have recovered from aphasia as well as intervened their language impairment on side of linguistic and neuronal aspects of views. The failure of judging the speech sound was caused by impairment of motor cortex that indicated there were lesions in left hemispheric language zone. Sound articulation phenomena were in the forms of phonemes deletion, replacement or assimilation in individual words and meaning building for anomic aphasia. Therefore, the Balinese sound patterns were stimulated by showing pictures to the subjects and recorded to recognize what individual consonants or vowels they unclearly produced and to find out how the sound disorder occurred. The physiology of sound production by subject’s speech organs could not only show the accuracy of articulation but also any level of severity the lesion they suffered from. The subjects’ speech sounds were investigated, classified and analyzed to know how poor the lingual units were and observed to clarify weaknesses of sound characters occurred either for place or manner of articulation. Many fricative and stopped consonants were replaced by glottal or palatal sounds because the cranial nerve, such as facial, trigeminal, and hypoglossal underwent impairment after the stroke. The phonological intervention was applied through a technique called phonemic articulation drill and the examination was conducted to know any change has been obtained. The finding informed that some weak articulation turned into clearer sound and simple meaning of language has been conveyed. The hierarchy of functional parts of brain played important role of language formulation and processing. From this finding, it can be clearly emphasized that this study supports the role of right hemisphere in recovery from aphasia is associated with functional brain reorganization.

Keywords: aphasia, intervention, phonology, stroke

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Authors: Rashidah Omar, Suzeini Abdul Halim, Aini Janteng

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The coefficients estimate problem for Taylor-Maclaurin series is still an open problem especially for a function in the subclass of bi-univalent functions. A function f ϵ A is said to be bi-univalent in the open unit disk D if both f and f^-1 are univalent in D. The symbol A denotes the class of all analytic functions f in D and it is normalized by the conditions f(0) = f’(0) – 1=0. The class of bi-univalent is denoted by  The subordination concept is used in determining second and third Taylor-Maclaurin coefficients. The upper bound for second and third coefficients is estimated for functions in the subclasses of bi-univalent functions which are subordinated to the function φ. An analytic function f is subordinate to an analytic function g if there is an analytic function w defined on D with w(0) = 0 and |w(z)| < 1 satisfying f(z) = g[w(z)]. In this paper, two subclasses of bi-univalent functions associated with Hohlov operator are introduced. The bound for second and third coefficients of functions in these subclasses is determined using subordination. The findings would generalize the previous related works of several earlier authors.

Keywords: analytic functions, bi-univalent functions, Hohlov operator, subordination

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Authors: Rafael Felipe Guatura da Silva, José Luis Gomes da Silva, Luiz Antonio, Ferreira Perrone de Brito

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Noise can cause serious damage to human health, such as hearing loss, stress, irritability, fatigue, and others. Aviation is a place where your entire process should be work out with the utmost attention and commitment of human resources, thus the need to study the effects of noise in this sector, as aeronautical noise levels are high. This study aimed to evaluate the impact of noise pollution on the performance of professionals regarding the fatigue generated by aeronautical noise and time to noise exposure. The methodology used consists of measurements of sound pressure levels at 42 points of the aerodrome. The selected points are located inside the hangars and outside the airfield hangars. All points chosen are close to the professionals' work areas, seeking to identify the sound pressure levels to which they submitted. The other part of the research used the principle on the application of a self-report questionnaire to a sample of 207 people working inside the aerodrome. The 207 professionals surveyed consist of aircraft mechanics, pilots, maintenance managers, and administrative professionals. The questionnaire was intended to evaluate the knowledge that professionals have about health risks caused by sound exposure as well as to identify diseases that professionals have, and that may be associated with exposure to high levels of sound pressure. Preliminary results identify points with sound pressure levels of up to 91.7 dB, thus highlighting the need for the use of personal protective equipment that reduces noise exposure. It was also identified a large number of professionals who are bothered by the sound exposure and approximately 25% of professionals interviewed reported having a hearing disorder.

Keywords: aeronautical noise, fatigue, noise and health, noise management

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Authors: Marziehossadat Moezzi

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In this paper, electromagnetically induced transparency (EIT) is investigated in a cylindrical quantum dot (QD) with a parabolic confinement potential. We study the effect of control lasers polarization on absorption coefficient, refractive index and also on the generation of the double transparency windows in this system. Considering an effective mass method, the time-independent Schrödinger equation is solved to obtain the energy structure of the QD. Also, we study the effect of structural characteristics of the QD on refraction and absorption of the QD in the presence of EIT.

Keywords: electromagnetically induced transparency, cylindrical quantum dot, absorption coefficient, refractive index

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Authors: Yong-Taeg Lee, Jun-Ho Na, Seung-Hun Kim, Seong-Uk Hong

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Damages from noise and vibration are increasing every year, most of which are noises between floors in deteriorated building caused by floor impact sound. In this study, the concrete slab measured vibration impact sound for evaluation floor vibration of deteriorated buildings that fails to satisfy with the minimum thickness. In this experimental study, the vibration scale by impact sound was calibrated and compared with ISO and AIJ standard for vibration. The results show that vibration in slab with thickness used in existing building reach human perception levels.

Keywords: vibration, frequency, accelerometer, concrete slab

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Authors: Mohammad R. Rahim, Shagil Akhtar, Prem K. Bharti, Syed Muneeb Iqbal

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Deformation and energy absorption studies with corrugated tubes where corrugation is perpendicular to the line of action which coincides exactly with the unstrained axis of the tubes. In the present study, several specimens with various geometric parameters are prepared and compressed quasi-statistically in ANSYS Workbench. It is observed that tubes with perpendicular corrugation alters the deformation condition considerably and culminates in a substantial escalation in energy absorption scope in juxtaposed with the tubes having a circular cross-section. This study will help automotive, aerospace and various other industries to design superior components with perpendicular corrugated tubes and will reduce the experimental trials by conducting the numerical simulations.

Keywords: ANSYS Workbench, deformation and energy absorption, corrugated tubes, quasi-static compression

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Authors: Chan Jong Park, Hye Min Park, Jeong Ho Kim, Ki Hyun Park, Koan Sik Joo

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This research used the MCNPX simulation program to evaluate the utility of a filter that was developed to minimize the damage to a semiconductor device during defect testing with X-ray. The X-ray generator was designed using the MCNPX code, and the X-ray absorption spectrum of the semiconductor device was obtained based on the designed X-ray generator code. To evaluate the utility of the filter, the X-ray absorption rates of the semiconductor device were calculated and compared for Ag, Rh, Mo and V filters with thicknesses of 25μm, 50μm, and 75μm. The results showed that the X-ray absorption rate varied with the type and thickness of the filter, ranging from 8.74% to 49.28%. The Rh filter showed the highest X-ray absorption rates of 29.8%, 15.18% and 8.74% for the above-mentioned filter thicknesses. As shown above, the characteristics of the X-ray absorption with respect to the type and thickness of the filter were identified using MCNPX simulation. With these results, both time and expense could be saved in the production of the desired filter. In the future, this filter will be produced, and its performance will be evaluated.

Keywords: X-ray, MCNPX, filter, semiconductor, damage

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Authors: Enes Yasa, Guven Fidan

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Building Simulation tools need to better evaluate convective heat exchanges between external air and wall surfaces. Previous analysis demonstrated the significant effects of convective heat transfer coefficient values on the room energy balance. Some authors have pointed out that large discrepancies observed between widely used building thermal models can be attributed to the different correlations used to calculate or impose the value of the convective heat transfer coefficients. Moreover, numerous researchers have made sensitivity calculations and proved that the choice of Convective Heat Transfer Coefficient values can lead to differences from 20% to 40% of energy demands. The thermal losses to the ambient from a building surface or a roof mounted solar collector represent an important portion of the overall energy balance and depend heavily on the wind induced convection. In an effort to help designers make better use of the available correlations in the literature for the external convection coefficients due to the wind, a critical discussion and a suitable tabulation is presented, on the basis of algebraic form of the coefficients and their dependence upon characteristic length and wind direction, in addition to wind speed. Many research works have been conducted since early eighties focused on the convection heat transfer problems inside buildings. In this context, a Computational Fluid Dynamics (CFD) program has been used to predict external convective heat transfer coefficients at external building surfaces. For the building facades model, effects of wind speed and temperature differences between the surfaces and the external air have been analyzed, showing different heat transfer conditions and coefficients. In order to provide further information on external convective heat transfer coefficients, a numerical work is presented in this paper, using a Computational Fluid Dynamics (CFD) commercial package (CFX) to predict convective heat transfer coefficients at external building surface.

Keywords: CFD in buildings, external convective heat transfer coefficients, building facades, thermal modelling

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Authors: F. Forouharmajd, S. Pourabdian, N. Ziayi Ghahnavieh

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For many years, the ear protectors have been used to preventing the audio and non-audio effects of received noise from occupation environments. Despite performing hearing protection programs, there are many people which still suffer from noise-induced hearing loss. This study was conducted with the aim of determination of human hearing system response to received noise and the effectiveness of ear protectors on preventing of noise-induced hearing loss. Sound pressure microphones were placed in a simulated ear canal. The severity of noise measured inside and outside of ear canal. The noise reduction values due to installing ear protectors were calculated in the octave band frequencies and LabVIEW programmer. The results of noise measurement inside and outside of ear canal showed a different in received sound levels by ear canal. The effectiveness of ear protectors has been considerably reduced for the low frequency limits. A change in resonance frequency also was observed after using ear protectors. The study indicated the ear canal structure may affect the received noise and it may lead a difference between the received sound from the measured sound by a sound level meter, and hearing system. It means the human hearing system may probably respond different from a sound level meter. Hearing protectors’ efficiency declines by increasing the noise levels, and thus, they are not suitable to protect workers against industrial noise particularly low frequency noise. Hearing protectors may be solely a reason to damaging of hearing system in a special frequency via changing of human hearing system acoustical structure. We need developing the subjective method of hearing protectors testing, because their evaluation is not designed based on industrial noise or in the field.

Keywords: ear protector, hearing system, occupational noise, workers

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Authors: Ana Cleide Vieira Gomes Guimbal de Aquino

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Sound communication is present in most vertebrates, from fish, mainly in species that live in murky waters, to some species of reptiles, anuran amphibians, birds, and mammals, including primates. There are, in fact, relevant similarities between human language and animal sound communication, and among these similarities are the vocalizations called calls. The first specific call in human babies is crying, which has a characteristic prosodic contour and is motivated most of the time by the need for food and by affecting the puppy-caregiver interaction, with a view to communicating the necessities and food requests and guaranteeing the survival of the species. The present work aims to articulate speech processing in the motor context with aspects of the project entitled emotional states and vocalization: a comparative study of the prosodic contours of crying in human and non-human animals. First, concepts of speech motor processing and general aspects of speech evolution will be presented to relate these two approaches to animal sound communication.

Keywords: speech motor processing, animal communication, animal behaviour, language acquisition

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Authors: H. Solomon, A. Abdul-Latif, R. Baleh, I. Deiab, K. Khanafer

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Aluminum foams were developed and tested due to their high energy absorption abilities for multifunctional applications. The aim of this research work was to investigate experimentally the effect of quasi-static biaxial loading complexity (combined compression-torsion) on the energy absorption capacity of highly uniform architecture open-cell aluminum foam manufactured by kelvin cell model. The two generated aluminum foams have 80% and 85% porosities, spherical-shaped pores having 11mm in diameter. These foams were tested by means of several square-section specimens. A patented rig called ACTP (Absorption par Compression-Torsion Plastique), was used to investigate the foam response under quasi-static complex loading paths having different torsional components (i.e., 0°, 37° and 53°). The main mechanical responses of the aluminum foams were studied under simple, intermediate and severe loading conditions. In fact, the key responses to be examined were stress plateau and energy absorption capacity of the two foams with respect to loading complexity. It was concluded that the higher the loading complexity and the higher the relative density, the greater the energy absorption capacity of the foam. The highest energy absorption was thus recorded under the most complicated loading path (i.e., biaxial-53°) for the denser foam (i.e., 80% porosity).

Keywords: open-cell aluminum foams, biaxial loading complexity, foams porosity, energy absorption capacity, characterization

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Authors: Shahin A. Abdel-Naby, Asad T. Hassan

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Electron-ion recombination data are needed for plasma modeling. The recombination processes include radiative recombination (RR), dielectronic recombination (DR), and trielectronic recombination (TR). When a free electron is captured by an ion with simultaneous excitation of its core, a doubly-exited intermediate state may be formed. The doubly excited state relaxes either by electron emission (autoionization) or by radiative decay (photon emission). DR process takes place when the relaxation occurs to a bound state by photon emission. Reliable laboratory astrophysics data (theory and experiment) for DR rate coefficients are needed to determine the charge state distribution in photoionized sources such as X-ray binaries and active galactic nuclei. DR rate coefficients for NIII and OIV ions are calculated using state-of-the-art multi-configuration Breit-Pauli atomic structure AUTOSTRUCTURE collisional package within the generalized collisional-radiative framework. Level-resolved calculations for RR and DR rate coefficients from the ground and metastable initial states are produced in an intermediate coupling scheme associated with Δn = 0 (2→2) and Δn = 1 (2 →3) core-excitations. DR cross sections for these ions are convoluted with the experimental electron-cooler temperatures to produce DR rate coefficients. Good agreements are found between these rate coefficients and the experimental measurements performed at the CRYRING heavy-ion storage ring for both ions.

Keywords: atomic data, atomic process, electron-ion collision, plasmas

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Authors: El Korchi Ayoub, Cherif Raef

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Interior noise in vehicles is an essential factor affecting occupant comfort. Over recent decades, much work has been done to develop simulation tools for vehicle NVH. At the medium high-frequency range, the statistical energy analysis method (SEA) shows significant effectiveness in predicting noise and vibration responses of mechanical systems. In this paper, the evaluation of the sound pressure level (SPL) inside an automobile cabin has been performed numerically using the statistical energy analysis (SEA) method. A test car cabin was performed using a monopole source as a sound source. The decay rate method was employed to obtain the damping loss factor (DLF) of each subsystem of the developed SEA model. These parameters were then used to predict the sound pressure level in the interior cabin. The results show satisfactory agreement with the directly measured SPL. The developed SEA vehicle model can be used in early design phases and allows the engineer to identify sources contributing to the total noise and transmission paths.

Keywords: SEA, SPL, DLF, NVH

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Authors: Claudio Burguez, María Castelló, Mikaela Pisani, Marcos Umpiérrez

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BIOFEEDBACK exhibition offers a unique experience for each visitor, combining art, neuroscience, and technology in an interactive way. Using a headband that captures the bioelectric activity of the brain, the visitors are able to generate sound and images in a sequence loop, making them an integral part of the artwork. Through this interactive exhibit, visitors gain a deeper appreciation of the beauty and complexity of the brain. As a special takeaway, visitors will receive an NFT as a present, allowing them to continue their engagement with the exhibition beyond the physical space. We used the EEG Biofeedback technique following a closed-loop neuroscience approach, transforming EEG data captured by a Muse S headband in real-time into audiovisual stimulation. PureData is used for sound generation and Generative Adversarial Networks (GANs) for image generation. Thirty participants have experienced the exhibition. For some individuals, it was easier to focus than others. Participants who said they could focus during the exhibit stated that at one point, they felt that they could control the sound, while images were more abstract, and they did not feel that they were able to control them.

Keywords: art, audiovisual, biofeedback, EEG, NFT, neuroscience, technology

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Authors: Emanuel Guariglia

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In this paper we deal with Chebyshev wavelets. We analyze their properties computing their Fourier transform. Moreover, we discuss the differential properties of Chebyshev wavelets due the connection coefficients. The differential properties of Chebyshev wavelets, expressed by the connection coefficients (also called refinable integrals), are given by finite series in terms of the Kronecker delta. Moreover, we treat the p-order derivative of Chebyshev wavelets and compute its Fourier transform. Finally, we expand the mother wavelet in Taylor series with an application both in fractional calculus and fractal geometry.

Keywords: Chebyshev wavelets, Fourier transform, connection coefficients, Taylor series, local fractional derivative, Cantor set

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Authors: Hyery Kang, Dong-Yeun Koh, Yun-Ho Ahn, Huen Lee

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Terahertz time-domain spectroscopy (THz-TDS) was used to observe the THF clathrate hydrate system with dosage of polyvinylpyrrolidone (PVP) with three different average molecular weights (10,000 g/mol, 40,000 g/mol, 360,000 g/mol). Distinct footprints of phase transition in the THz region (0.4 - 2.2 THz) were analyzed and absorption coefficients and complex refractive indices are obtained and compared in the temperature range of 253 K to 288 K. Along with the optical properties, ring breathing and stretching modes for different molecular weights of PVP in THF hydrate are analyzed by Raman spectroscopy.

Keywords: clathrate hydrate, terahertz, polyvinylpyrrolidone (PVP), THz-TDS, inhibitor

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Authors: Mauricio Gracia, Luis Leal, Bharat Verma

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Computational fluid dynamics (CFD) has become nowadays an important tool in the process of hydrodynamic design of modern ships. CFD is used to model any phenomena related to fluid flow in a control volume like a ship or any offshore structure in the sea. In the present study, the current force drag coefficients for a Colombian Navy Frigate in deep and shallow water are estimated through the application of CFD. The study shows the process of simulating the ship current drag coefficients using the CFD simulations method, which is conducted using STAR-CCM+ software package. The Almirante Padilla class Frigate ship scale model is investigated. The results show the ship current drag coefficient calculated considering a current speed of 1 knot with a 90° drift angle for the full-scale ship. Predicted results were compared against the current drag coefficients published in the Lloyds register OCIMF report. It is shown that the simulation results agree fairly well with the published results and that STAR-CCM+ code can predict current drag coefficients.

Keywords: CFD, current draft coefficient, STAR-CCM+, OCIMF, Bollard pull

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Authors: F. Laatar, S. Ktifa, H. Ezzaouia

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Plasma Enhanced Chemical Vapor Deposition (PECVD) method is used to deposit hydrogenated nanocrystalline silicon films (nc-Si: H) on Porous Anodic Alumina Films (PAF) on glass substrate at different deposition duration. Influence of the deposition time on the physical properties of nc-Si: H grown on PAF was investigated through an extensive correlation between micro-structural and optical properties of these films. In this paper, we present an extensive study of the morphological, structural and optical properties of these films by Atomic Force Microscopy (AFM), X-Ray Diffraction (XRD) techniques and a UV-Vis-NIR spectrometer. It was found that the changes in DT can modify the films thickness, the surface roughness and eventually improve the optical properties of the composite. Optical properties (optical thicknesses, refractive indexes (n), absorption coefficients (α), extinction coefficients (k), and the values of the optical transitions EG) of this kind of samples were obtained using the data of the transmittance T and reflectance R spectra’s recorded by the UV–Vis–NIR spectrometer. We used Cauchy and Wemple–DiDomenico models for the analysis of the dispersion of the refractive index and the determination of the optical properties of these films.

Keywords: hydragenated nanocrystalline silicon, plasma processing chemical vapor deposition, X-ray diffraction, optical properties

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Authors: Ali Rabiee, Hessam Ghasemnejad

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Extensive experimental investigation on the effect of stitching pattern on tubular composite structures was conducted. The effect of stitching reinforcement through thickness on using glass flux yarn on energy absorption of fiber-reinforced polymer (FRP) was investigated under high speed loading conditions at axial loading. Keeping the mass of the structure at 125 grams and applying different pattern of stitching at various locations in theory enables better energy absorption, and also enables the control over the behaviour of force-crush distance curve. The study consists of simple non-stitch absorber comparison with single and multi-location stitching behaviour and its effect on energy absorption capabilities. The locations of reinforcements are 10 mm, 20 mm, 30 mm, 10-20 mm, 10-30 mm, 20-30 mm, 10-20-30 mm and 10-15-20-25-30-35 mm from the top of the specimen. The effect of through the thickness reinforcements has shown increase in energy absorption capabilities and crushing load. The significance of this is that as the stitching locations are closer, the crushing load increases and consequently energy absorption capabilities are also increased. The implementation of this idea would improve the mean force by applying stitching and controlling the behaviour of force-crush distance curve.

Keywords: through-thickness stitching, 3D enforcement​, energy absorption, tubular composite structures

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Authors: Li Hung-Hui, Chen Chi-Chieh, Yang Zon-Yee

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This study aims to explore the impact energy absorption in the fragmented processes of rock samples during the split-Hopkinson-pressure-bar tests. Three kinds of rock samples including granite, marble and sandstone were tested. The impact energy absorptions were calculated according to the incident, reflected and transmitted strain wave histories measured by a oscilloscope. The degree of fragment rocks after tests was quantified by the box dimension of the fractal theory. The box dimension of rock fragments was obtained from the particle size distribution curve by the sieve analysis. The results can be concluded that: (1) the degree of rock fragments after tests can be well described by the value of box dimension; (2) with the impact energy absorption increasing, the degrees of rock fragments are varied from the very large fragments to very small fragments, and the corresponding box dimension varies from 2.9 to 1.2.

Keywords: SHPB test, energy absorption, rock fragments, impact loading, box dimension

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Authors: Mahmoudi Noureddine, Kaou Abdellah

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Energy absorption is a major requirement for automotive structures. Although crashworthy structures of composite based glass fiber have exhibited energy absorption greater than similar at other composites structures, the crush process in many cases is accompanied by fracture, rather than by plastic deformation. The crash experiments show that the tubes are crushed in progressive manner start from one end of the tubes and delamination takes place between the layers. To better understand details of the crash process, ABAQUS finite element code is used.

Keywords: Energy absorption, crash, PEHD

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Authors: Anshul Jain, P. Deepak Kumar, P. K. S. Dikshit

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To stabilize the riverbanks in the curved reaches of alluvial channels due to erosion and to stop sediment transportation, many models and theories have been put forth. One among such methods is to install flat vanes on the channel bed in predetermined manner. In practical, a relatively small no of vanes can produce bend flows which are practically uniform across the channel. The objective of the present study is to measure the drag and lift on such submerged vanes in open channels. Experiments were performed and the data collected have been presented and analyzed. Using the data collected herein, predictors for the coefficients of drag and lift have been developed. Such predictors yield the value of these coefficients for the known fluid properties and flow characteristic of the channel.

Keywords: drag, lift, vanes, open channel

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Authors: Budimir S. Sudimac, Andjela N. Dubljevic

Abstract:

The aim of thisresearch paper is to consider possibilities for improving the street lighting on the E75 highway, which passes through Serbia, using renewable sources of energy. In this paper, we analyzed the possibilities for installing sound barriers along the highway and integrating photovoltaic (PV) modules, which would generate electrical energy to power the lighting on the section of the highway running through Belgrade. The main aim of this paper is to analyze, show and promote innovative, hybrid, multi-functional solar technology using PV modules as an element of sound barriers in urban areas. The paper seeks to show the hybridity of using sustainable technologies in solving environmental issues. This structure solves the problem of noise in populated areas and provides the electricity from renewable source.

Keywords: noise, PV modules, solar energy, sound barriers

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