Artificial Neural Network for Prediction of Seat-to-Head Frequency Response Function During Whole Body Vibrations in the Fore-and-Aft Direction

Vibrations while driving, regardless of their intensity and shape, have the most obvious effect of reducing driving comfort. Seat-to-head frequency response function (STHT) is a complex relationship resulting from the movement of the head due to the action of excitation on the seat in the form of vibrations in the seat/head interface. In this research, an artificial neural network model was developed, which aims to simulate the STHT function through the body of the subjects based on the data obtained experimentally. The experiments were conducted with twenty healthy male volunteers, who were exposed to single-axis fore-and-aft random broadband vibration. All the results of the experiment were recorded on the basis of which the artificial neural network (ANN) was trained. The developed ANN model has the ability to predict STHT values in the range of trained values both when changing the anthropometric measures of the subjects and changes in the input characteristics of vibrations. The mathematical models based on recurrent neural networks (RNN) used in this paper show with high accuracy STHT values in case there exists prior information about the anthropometric measures of the subjects and the input characteristics of vibrations. The results show that the expensive real-time simulations could be avoided by using reliable neural network models

Diffusion of drugs in hydrogels based on (meth)acrylates, poly(alkylene glycol) (meth)acrylates and itaconic acid

The aim of this paper is to propose equations for the diffusion of drugs for investigated drug/hydrogel systems using the parameters affecting the transport of drug through poly- (2-hydroxyethylmethacrylate/itaconic acid) (P(HEMA/IA)), poly(2-hydroxyethylacrylate/ita- conic acid) (P(HEA/IA)), and poly(2-hydroxyethylmethacrylate/poly(alkyleneglycol) (meth)- acrylates) (P(HEMA/BIS)) copolymeric hydrogels. Different monomer types, as well as the variable content of some components in hydrogel composition (the amount of ionizable comonomer (IA) and different type of nonionic poly(alkyleneglycol) (meth)acrylates), ultimately defined the pore size available for drug diffusion. The hydrogels synthesized ranged from nonporous to microporous, based on the classification in accordance to the pore size, and could be classified as hydrogels that contain ionic groups and hydrogels without ionic groups. The drugs selected for this study are bronchodilators-theophylline (TPH), fenethylline hydrochloride (FE), and antibiotic cephalexin (CEX). Results of in vitro drug release tests defined the release systems based on the drug type, as well as the type of hydrogel used. The diffusion coefficient of drugs and the restriction coefficient, λ, defined as the ratio of solute to 'pore' radius (rs/rζ) that describes the ease of drug release from the gels, were used as factors that govern the release process.Cilj ove studije je da se predlože difuzione jednačine za ispitivane sisteme lek/hidrogel. Korišćeni su hidrogelovi poli(2-hidroksietilmetakrilat/itakonska kiselina) (P(HEMA/IK)), poli(2-hidroksietilakrilat/itakonska kiselina) (P(HEA/IK)) i poli-(2-hidroksietilmetakrilat/poli(alkilenglikol)-(met)akrilati) (P(HEMA/BIS)). Komponenta koja se menja u sastavu hidrogela HEMA, HEA, kao i udeo komponente sa promenljivim sadržajem (udeo jonizujućeg komonomera (IK) i tip BIS komponente) definiše veličinu pora koja je dostupna za difuziju leka. U ovoj studiji su korišćeni lekovi bronhodilatori teofilin (TPH) i fenetilin-hidrohlorid (FE), i antibiotik cefaleksin (CEX). Ovi gelovi su klasifikovani u režimu poroznosti kao neporozni i mikroporozni, sa veličinom pora u opsegu 0,18-24,9 nm. Kontrolisano otpuštanje lekova je izvedeno u in vitro uslovima u puferu pH 7,40 i na 37 °C, da bi se odredili difuzioni koeficijenti leka u hidrogelovima. Na osnovu toga su predložene jednačine difuzije leka kroz hidrogel za svaki sistem lek/hidrogel. Rezultati dobijeni fitovanjem eksperimentalnih podataka su pokazali da difuzija leka zavisi od hemijske strukture i morfologije hidrogela i parametra λ, koji predstavlja odnos prečnika leka i veličine pora. Eksponencijalna zavisnost koeficijenta restrikcije od normalizovanog koeficijenta difuzije je dobijena za sisteme TPH/P(HEMA/IA), FE/P(HEMA/ /IA), CEX/P(HEMA/BIS) i CEX/P(HEA/IA).Utvrđeno je da veliki uticaj na difuziju leka imaju interakcije koje se odigravaju između funkcionalnih grupa leka i polimerne mreže

Immobilization of lipase from Candida rugosa into copolymer hydrogels of poly(N-isopropylacrylamide-co-itaconic acid) synthesized in the presence of surfactants

To overcome the problems of free enzyme application as catalysts in chemical reactions, i.e., high costs of isolation and purification processes, high sensitivity to process conditions, insufficient enzyme stability etc., different immobilization techniques need to be used. Immobilization to/within solid support improves enzyme stability decreasing its denaturation. This paper deals with hydrogels of N-isopropylacrylamide and itaconic acid with incorporated nonionic surfactants (Triton X-100, Brij 30 and Tween 80) synthesized in distilled water at room temperature by free radical polymerization. These hydrogels were used as supports for immobilization of enzyme, lipase from Candida rugosa by post-entrapment method. The aim was to investigate the effect of the non-ionic surfactants on the lipase binding capacity, as well as on its hydrolytic activity. In order to characterize the obtained hydrogels, FT-IR analysis has been performed. Further, the swelling behaviour of these samples in buffer solution of pH 6.80 has been investigated. The dynamic-mechanical properties of hydrogels have been studied, too. The immobilized lipase showed somewhat reduced hydrolytic activity, compared to the activity of free lipase as well as in comparison to the lipase immobilized to the reference sample (sample synthesized under the same polymerization conditions, but in the absence of surfactants). It was concluded that the addition of surfactants increased the hydrogel mesh size. The surfactant addition did not affect the dynamic-mechanical properties of the investigated hydrogels. The largest percentage of specific activity and yield of activity were presented by the reference sample, too. It is obvious that the absence of surfactants charged groups has no influence on the lipase binding capacity, and the obtained activity yields are to be expected.U radu je ispitana imobilizacija lipaze iz Candida rugosa u hidrogel poli(N-izopropilakrilamid-ko-itakonska kiselina) sintetisane u prisustvu nejonskih površinski aktivnih materija. Pri sintezi je varirana vrsta i sadržaj površinski aktivnih materija. Ispitana su mehanička svojstva sintetisanih hidrogelova i urađena je FT-IR analiza. Imobilizacija lipaze je izvedena bubrenjem prethodno sintetisanih hidrogelova u rastvoru lipaze, a zatim je ispitan uticaj dodatka površinski aktivnih materija pri sintezi nosača na kapacitet uklapanja lipaze u hidrogel i na aktivnost tako uklopljene lipaze. Imobilisana lipaza iz Candida rugosa je pokazala umanjenu hidrolitičku aktivnost, kako u odnosu na aktivnost slobodne lipaze, što je i očekivano, tako i u odnosu na aktivnost lipaze imobilisane u referentni hidrogel, sintetisan bez prisustva površinski aktivnih materija

Thermal analysis of solid and vented disc brake during the braking process

Braking system is one of the most important components of a vehicle on the road. This system has the task to bring the vehicle to stop or slow down. Friction brakes, during the braking process, convert the kinetic and potential energy into the thermal energy (heat). The basic components of braking systems, brake discs and brake pads, in a short period of time absorb a large amount of heat release (Travaglia et al. 2014). The absorbed heat must be, as far as possible, effectively dissipated in order to ensure the normal operation of the braking system (Day et al. 1984). High temperature during the braking process may cause many problems such as thermal cracks, premature wear, brake fade and thermally-excited vibration (Lee 1999). In this study, a typical disc brake system was modeled including brake disc and pads. Using COMSOL Multiphysics 5.0, we investigated thermal behavior of two types of discs - solid and vented dics. The results show that the vented disc is a much better solution than the solid disc, because the greater amount of heat is released for the same amount of time

Hydrogel based on chitosan, itaconic acid and methacrylic acid as adsorbent of Cd2+ ions from aqueous solution

A hydrogel has been synthesized by ionic crosslinking of chitosan (Ch) with itaconic acid (IA), followed by a free radical polymerization and crosslinking of Ch/IA network by adding methacrylic acid and the crosslinker. The resulting material (Ch/IA/MAA hydrogel) was characterized by spectral (Fourier transform infrared (FTIR)), thermal (thermogravimetric analysis (TGA)) and structural (SEM/EDX and atomic force microscopy (AFM)) analyses. The prepared hydrogel was investigated as potential adsorbent for removal of Cd2+ ions from aqueous solution. The effect of various physico-chemical parameters such as pH, adsorbent dosage, adsorbate concentration and contact time was studied in batch experiments. The results of spectral analyses of Cd-loaded hydrogel have shown that active functional groups are -NH2, -OH and -COOH. SEM/EDX analysis and AFM surface topography and phase images indicated that apart from the adsorption on the surface of the hydrogel, sorption takes place in the bulk, as well. The experimental kinetic and equilibrium data were better fitted by pseudo-second order kinetic model and Langmuir adsorption isotherm. The parameters obtained in thermodynamic studies showed that the adsorption of Cd2+ on Ch/IA/MAA hydrogel was spontaneous and exothermic in nature. Desorption studies were carried out using acid leaching (HNO3) and it has been shown that the regenerated hydrogel can be reused three times without any loss of adsorption capacity. The maximum adsorption of 285.7 mg/g has been obtained at pH 5.5 and the results of adsorption/desorption experiments implies that the Ch/IA/MAA hydrogel may be used as efficient sorbent for removal of Cd2+ ions from aqueous solution

Removal of Cu2+ ions using hydrogels of chitosan, itaconic and methacrylic acid: FTIR, SEM/EDX, AFM, kinetic and equilibrium study

A removal of Cu2+ ions from aqueous solutions onto hydrogels of chitosan. itaconic and methacrylic acid has been investigated using batch adsorption technique. The extent of adsorption was investigated as a function of pH, adsorbent dose, initial metal ion concentration, contact time and temperature. The FIR spectra showed that -NH2, -OH and -COOH groups are involved in the Cu2+ ions adsorption. The surface topography changes were observed by AFM, where the phase images indicated that sorption takes place on the surface of the hydrogel and in the bulk. Pseudo-first order, pseudo-second order and intraparticle diffusion models were analyzed and showed that the Cu2+ ions adsorption followed pseudo-second order kinetics. The equilibrium data were analyzed using Langmuir, Freundlich and Redlich-Peterson isotherms and the best interpretation was given by Redlich-Peterson. The adsorption capacity was found to be 122.59 mg/g, based on the non-linear Langmuir isotherm. Based on the separation factor. R-L, the Cu2+ ion adsorption is favorable, while the low activation energies indicate physisorption. Desorption experiments, done with a nitric acid, showed that the investigated hydrogels could be reused without significant losses of the initial properties even after three adsorption-sorption cycles

Sorption of zinc by novel pH-sensitive hydrogels based on chitosan, itaconic acid and methacrylic acid

Novel pH-sensitive hydrogels based on chitosan, itaconic acid and methacrylic acid were applied as adsorbents for the removal of Zn(2+) ions from aqueous solution. In batch tests, the influence of solution pH, contact time, initial metal ion concentration and temperature was examined. The sorption was found pH dependent, pH 5.5 being the optimum value. The adsorption process was well described by the pseudosecond order kinetic. The hydrogels were characterized by spectral (Fourier transform infrared-FTIR) and structural (SEM/EDX and atomic force microscopy-AFM) analyses. The surface topography changes were observed by atomic force microscopy, while the changes in surface composition were detected using phase imaging AFM. The negative values of free energy and enthalpy indicated that the adsorption is spontaneous and exothermic one. The best fitting isotherms were Langmuir and Redlich-Peterson and it was found that both linear and nonlinear methods were appropriate for obtaining the isotherm parameters. However, the increase of temperature leads to higher adsorption capacity, since swelling degree increased with temperature