The welding of foils, textiles, and textile composites made of thermoplastic polymer materials using machines with an ultrasonic rotary sonotrode is a high-tech welding technique. Many authors have ...dealt with only a few parameters in earlier papers, mainly mentioning the speed, i.e., the welding time, and the power of the ultrasonic generator. In this paper, the acoustic model of ultrasonic welding is defined. Based on the model, a group of 44 different parameters important for ultrasonic welding of polymer materials has been summarised, namely 12 parameters of the polymer material, 11 general acoustic and electroacoustic parameters, and 21 technical parameters depending on the ultrasonic machine. Based on this, a comprehensive mathematical derivation was carried out, linking parameter groups with other findings from acoustics, thermodynamics of polymers, and technical and technological parameters of welding polymer materials. The most important parameters are the power of the ultrasonic generator and the welding time, which in practice are adjusted to produce a solid weld. The method of measuring the amplitude of the sonotrode using a photonic sensor is presented in this paper. For 42 groups of welds done at various welding speeds and ultrasonic generator powers, the breaking forces of ultrasonic welds were measured. There are illustrations of power dependence and breaking forces. The accuracy of the mathematical model was confirmed by comparison with the calculation results based on the findings of these measurements.
Presbycusis and noise-induced hearing loss result in characteristic audiogram curves with increasing levels of hearing loss at higher frequencies. Another specific form of audiogram curve is the ...cookie bite, which is often the result of inherited hearing loss and sometimes the result of illness or injury. The influence of the hearing loss on speech intelligibility was examined along with a list of words selected according to the frequency range of the phonemes present. Dependence of speech intelligibility and frequency of dominant hearing loss, at lower, middle and higher frequencies and over the whole range is shown. The method of speech audiometry with the simulated hearing loss on the speech material and the normal hearing people is presented.
The paper presents a new method for determining the machine-hand welding times of synthetic polymer materials using ultrasonic welding machines with rotary sonotrode. The method is based on the ...claims and observations of W. Möller intended for the clothing industry in the 1990s, according to which there is a spontaneous drop in sewing speed when strongly curved seams are joined, which is due to the possibility of human reactions. The method for determining machine-hand sewing times of curved seams was well accepted in garment production processes. It is used to standardize production time. Using ultrasonic welding machines with rotary sonotrode, the problem of determining the time of ultrasonic joining of curved seams on clothing or technical textiles remained unsolved. That is why is completely new and original model was created, which combines eight technical parameters of ultrasonic welds, eight technological parameters of the production process and seven ergonomic parameters depending on the psychophysical conditions of the workers. The systematic development of the mathematical relationship of all 23 parameters mentioned and the corresponding mathematical expressions for determining and calculating these parameters are presented. These results were also verified by experimental measurements, which show a favourable correlation between the calculated and measured machine hand times. The relationships between the recommended welding speeds, the critical radii of curvature and the number of reactions required according to Möller and the new model are also presented. An analysis of the success in the application of Möller’s and the new model was also performed.
Various studies performed so far have not provided unique answers to the acoustic quality evaluation of the sound control rooms, as no influence of specific features of the respective sound control ...room have been taken into account. In a process described in this paper, all the specific features that these rooms have are taken into consideration and sound is evaluated by means of reproduction through high quality professional equipment. Also, a listening area is a small, exactly given place for optimal listening for sound control engineer.The optimal sound control room must provide a complete and clear perception of reproduced sound with all specific features, and the room's spatial characteristics may not influence nor change the characteristics of the reproduced sound. Conjoint Analisys method is used to obtain estimation of the impact of the room objective acoustic quality parameters on the subjective assessment of the professional sound control room. Thereby, the use of modern statistical method (Conjoint Analysis - CA) shows dependence of one subjective parameter on more than one objective parameter. This principle determines more accurately real-life conditions, where all ratings are subject to complex dependence on more objective parameters.
High frequency (HF) welding of polymer materials is increasingly used in modern manufacturing processes. The literature on HF welding process parameters was reviewed and it was found that 3-5 basic ...welding parameters were considered, which is insufficient for the scientific study of HF welding of polymeric materials. This article presents the mathematical expressions for the evaluation combining 17 influential parameters. For the first time, the specific and latent heat of the welded polymer material were used. The breaking forces of welds made by RF welding are investigated by varying the anode current, the coupling capacitor, and the exposure time of the HF electromagnetic fields. It was found that the amount of HF energy supplied depends on the breaking forces of the weld. A characteristic inflection point was also observed in the graph of the dependence of the breaking forces on the percentage of the coupling capacitor and the anode current. During elongation, it was observed that the weld is separated by peeling before the inflection point and breaks after the inflection point by tearing at the extruded edges of the weld. If the HF energy is applied to the weld for too long, there will be excessive melting of the material in the weld, thinning of the weld, unfavourable appearance of the extruded edges and electrical breakdown, and a drastic drop in the breaking force.
Objective parameters of the room acoustics quality are obtained from the impulse response, which is measured using the appropriate PC based acoustic measurement system with two types of loudspeakers. ...Such measurement gives the impulse response that is the result of measurement of the entire system, which consists of the room and electro acoustics equipment. In order to investigate the real influence of loudspeakers on the measurement results, the research was made in the same measuring conditions. Impulse responses were measured with the same measuring system. Measuring point was selected at the optimum listening position in the room, and all measurements were carried out in the same place. The loudspeakers were placed at the optimum and characteristic positions in the room, and rotated around their axes in order to determine the impact of their position and directivity characteristics on the measurement of objective parameters of room acoustic quality.Original Abstract: Vrijednosti objektivnih parametara akusticke kvalitete prostora dobivaju se iz impulsnog odziva, koji se mjeri odgovarajucom opremom temeljenom na osobnom racunalu, s dvije vrste zvucnika. Takvo mjerenje daje impulsni odziv koji je rezultat mjerenja cijelog sustava, koji se sastoji od prostora i primijenjene elektoakusticke opreme. Napravljeno je istrazivanje koliki je stvarni utjecaj zvucnika na rezultate mjerenja. Impulsni odzivi mjereni su uvijek istom opremom, a mjerne tocke su odabrane tako da budu na optimalnom mjestu za slusanje, i sva mjerenja su izvedena u istom prostoru. Zvucnici su smjesteni na optimalnim i karakteristicnim mjestima u prostoriji, i rotirani su oko vertikalne osi u cilju utvrdivanja utjecaja njihove pozicije i usmjerne karatkeristike na rezultate mjerenja objektivnih parametara akusticke kvalitete prostora.
Modelling voice tract using an acoustical-mechanical analogy is shown in this article. The process of modelling voice tract is often reduced to one-dimensional acoustical model, i.e. planar waveguide ...model. With this acoustical-mechanical model, computer programs are utilized to analyze and synthesize the voice tract. Hence, it is possible to calculate models which describe the voice tract with satisfactory quality and detail level and these models can be used in practice and applied to particular cases. In this article the process of producing a voice tract model is presented. The process includes the usage of three different computer programs, each of them dedicated to one segment of modelling. Recordings for three speakers were made and the analysis of voice parameters was performed. After the analysis is completed, a two-dimensional model of the voice tract was made, which resulted in a mechanical model consisting of specific number of tubes. Finally, the evaluation procedure for the model is done by applying a software developed specifically for this purpose, in order to determine whether the resulting model truly represents the voice tract of each speaker.
U sklopu istraživačkog projekta IP-2018-01-6363 Razvoj i toplinska svojstava
inteligentne odjeće (ThermIC) financiranog od Hrvatske zaklade za znanost,
u Zavodu za odjevnu tehnologiju ...Tekstilno-tehnološkog fakulteta uspostavljen
je Laboratorij za termoizolacijska svojstva odjeće. U laboratoriju je
instaliran integrirani mjeriteljski sustav za cjelovita ispitivanja termofizioloških
svojstava odjevnih kompozita i odjeće. Većina uređaja koji čine cjeloviti
mjeriteljski sustav predstavlja originalna patentirana rješenja voditelja
projekta i članova tima te su prikazani na domaćim i međunarodnim izložbama
inovacija, gdje su nagrađeni nizom priznanja i nagrada. Integrirani mjerni
sustav za termofiziološka svojstva odjeće sastoji se od mjernog sustava za
određivanje statičkih i dinamičkih toplinskih svojstava kompozita i odjeće
(vruće ploče i termalnog manekena), uređaja za mjerenje fizioloških parametara
ljudskog tijela pri egzaktnom vrednovanju toplinske udobnosti odjeće,
višenamjenskog diferencijalnog konduktometra za tekstilne kompozite i odjeću,
uređaja za nedestruktivno mjerenje otpora prolazu topline i propusnosti
vodene pare/otpora prolazu vode (Permetest) i uređaja za mjerenja temperaturnih
gradijenata u odjevnim kompozitima. Osim spomenutih mjernih uređaja,
u radu su prikazani funkcionalni prototipovi pametne i inteligentne
odjeće razvijene u Zavodu za odjevnu tehnologiju Tekstilno-tehnološkog
fakulteta.
Ovaj članak daje primjer izrade modela govornog trakta zasnovanog na akustičko-mehaničkim analogijama, za tri govornika, pomoću računalno zasnovanog sustava. Definiranje modela govornog trakta često ...se svodi na jednodimenzionalni akustički model, planarni valovodni model. Kad je napravljen akustičko-mehanički model, u analizu i sintezu uvode se računala i računalni programi. Pomoću njih se dobivaju modeli i izračuni koji sa zadovoljavajućom kvalitetom i preciznošću opisuju govorni trakt, pa takve modele možemo koristiti u praksi i primjenjivati na konkretne slučajeve. U članku su za dobivanje modela govornog trakta korištene tri različite programske podrške, svaka u svom segmentu izrade modela. Snimljena su tri govornika i napravljena je analiza glasa. Nakon toga je, opet koristeći računalo, izmodeliran dvodimenzionalni model govornog trakta, koji kao rezultat daje mehanički model s odre.enim brojem cjevčica. Na kraju je napravljena provjera tog modela sa programskom podrškom koja je napisana za tu svrhu, kako bi se utvrdilo da dobiveni model zaista predstavlja govorni trakt pojedinog govornika.
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