Conventional polyurethane foam has non-tunable sound absorption properties. Here, a magneto-induced foam, called magnetorheological (MR) foam, was fabricated with the feature of being able to tune sound absorption properties, primarily from the middle- to higher-frequency ranges. Three different samples of MR foams were fabricated in situ by varying the concentration of Carbonyl Iron Particles (CIPs) (0, 35, and 75 wt.%). The magnetization properties and tunable sound absorption characteristics were evaluated. From the magnetic saturation properties, the results showed very narrow and small coercivity of hysteresis loops relative to the soft magnetic properties of the CIPs. MR foam with 75 wt.% CIPs showed a higher magnetic saturation at 91.350 emu/g compared to MR foam with 35 wt.% CIPs at 63.896 emu/g. For tunable sound absorption testing, the effect of ‘shifting’ to higher frequency was also observed when the magnetic field was applied, which was ~10 Hz for MR foam with 35 wt.% CIPs and ~130 Hz for MR foam with 75 wt.% CIPs. As the latest evolution of semi-active noise control materials, the results from this study are valuable guidance for the advancement of MR-based devices.

This paper proposes a new type of magnetorheological elastomer (MRE) using rubber from waste tires and describes its performance characteristics. In this work, scrap tires were utilized as a primary matrix for the MRE without incorporation of virgin elastomers. The synthesis of the scrap tire based MRE adopted a high-temperature high-pressure sintering technique to achieve the reclaiming of vulcanized rubber. The material properties of the MRE samples were investigated through physical and viscoelastic examinations. The physical tests confirmed several material characteristics—microstructure, magnetic, and thermal properties–while the viscoelastic examination was conducted with a laboratory-made dynamic compression apparatus. It was observed from the viscoelastic examination that the proposed MRE has magnetic-field-dependent properties of the storage modulus, loss modulus, and loss tangent at different excitation frequencies and strain amplitudes. Specifically, the synthesized MRE showed a high zero field modulus, a reasonable MR effect under maximum applied current, and remarkable damping properties.

The present study deals with the sound absorption performance of natural fibres from the oil palm frond (OPF), mainly considered agricultural waste. Therefore, this study aimed to investigate the sound absorption performance of OPF fibre-reinforced composite under normal incidence sound. The materials used were OPF particles and urea-formaldehyde was used as an adhesive. The particleboards were produced with three particle sizes and four target densities. The absorption coefficient of normal incidence sound (α_n) was tested using an impedance tube. The effects of particle size and bulk density were also evaluated. The findings reveal thatα_n exceeded 0.45 at 1000 Hz and could reach 0.95 above 3.3 kHz. This occurred when the bulk density of the OPF composite particleboards ranged between 0.3–0.4 g/cm³, and the particle size varied between medium to coarse. The results also indicated that the absorption frequency and the degree of α_n significantly increased as the bulk density decreased. Therefore, OPF fibres can be used to create sound-absorbing composite particleboards.

A novel strategy for detecting Premature Ventricular Contraction (PVC) is proposed and investigated. The strategy employs a Swarm-based Support Vector Machine (SSVM). An SSVM is an SVM optimised by using Particle Swarm Optimisation (PSO). The strategy proposes new inputs. The inputs involve the width and the gradient of the electrocardiographic QRS wave. Experiments with different inputs and different SVM kernel functions are conducted to find the best one for PVC detection. On a test using clinical data, SSVM performs well in PVC detection with sensitivity, specificity and accuracy of 98.94%, 99.99% and 99.46%, respectively.

This article introduces a new method for detection of atrial fibrillation (AFib) using a support vector machine (SVM). AFib could lead to heart failure and stroke and thus an AFib early detection is very important. In this article, an SVM and variabilities of electrocardiographic heart rate are employed to detect AFib. Radial basis functions (RBF) is utilized for SVM. Different SVM constructions are tested to find the best one. Furthermore, two features of electrocardiogram are examined as the inputs of SVM. Using clinical electrocardiogram, the proposed method find the performance of 95.81 %, 98.44% and 97.50% in terms of sensitivity, specificity and accuracy.

This article reports an experimental investigation of sound insulation and absorption performance of a materials made of reclaimed ground tire rubber which is known as un-recyclable thermoset. The bulk waste tire is processed using single step recycling methods namely high-pressure high-temperature sintering (HPHTS). The bulk waste tire is simply placed into a mold and then a pressure load of 3 tons and a heating temperature of 200°C are applied to the mold. The HPHTS conducted for an hour and then it is cooled in room temperature. The resulted product is then evaluated the acoustical properties namely sound transmission loss (STL) and sound absorption coefficient using B&K Tube Kit Type 4206-T based on ISO 10534-2, ASTM E1050 and ASTM E2611. The sound absorption coefficient is found about 0.04 until 0.08 while STL value ranges between 50 to 60 dB. The sound absorption values are found to be very low (<0.1), while the average STL is higher than other elastomeric matrix found in previous work. The reclaimed tire rubber through HPHTS technique gives good soundproof characteristic.