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A finite element analysis of acoustic propagation in a multilayered medium is presented in this paper. A circular transmitter (diameter 14 mm, thickness 3 mm) and a rectangular receiver (20×10×0.5 mm3) are set to detect the variations in the propagation pattern. A complex medium (70×40×60 mm3) composed of skin, fat, muscle, bone and liquid is designed in a simulated environment. A scale of frequencies (10 kHz to 2 MHz) is applied to trace the impact on the propagation pattern as well. It is found from the analysis that fat and liquid layers affect the acoustic propagation the most (-69 dB), which results in a significant drop in the received sound pressure level at the receiving end. Again, other than skin and fat layers, low frequencies (less than 1 MHz) are more beneficial in terms of sound pressure level. However, higher frequencies contribute to lower displacements at the receiving end, which will cause less power potential as well. ABSTRAK: Analisis elemen terhingga bagi penyebaran akustik dalam medium berlapis dibentangkan dalam kajian ini. Pemancar bulat (diameter 14 mm, ketebalan 3 mm) dan penerima segi empat tepat (20 × 10 × 0.5 mm3) diatur bagi mengesan perubahan pola penyebaran. Medium kompleks (70 × 40 × 60 mm3) yang terdiri daripada kulit, lemak, otot, tulang dan cecair direka dalam persekitaran simulasi. Skala frekuensi (10 kHz hingga 2 MHz) digunakan bagi mengesan corak penyebaran. Dapatan kajian menunjukkan bahawa lapisan lemak dan cecair mempengaruhi penyebaran akustik (-69 dB), yang mengakibatkan penurunan mendadak tahap penerimaan tekanan bunyi di hujung penerima. Selain lapisan kulit dan lemak, frekuensi rendah (kurang dari 1 MHz) adalah lebih berguna dari segi tahap tekanan suara. Walau bagaimanapun, frekuensi lebih tinggi menyebabkan kurang anjakan di hujung penerima, sekaligus mengurangkan potensi daya tenaga.

Product warranty seals or stickers are criteria for after-sale warranty services. The unauthorized removal or modification of a seal will void the warranty. So far, there is no detection method to confirm the warranty, other than the visual inspection of the deformation of the seal. Hence, a system to detect, read, and record the ’warranty’ seal deformation is presented in this paper. A flexible piezoelectric sensor was used to determine the mechanical impacts of the seal. Three major impacts are discussed and evaluated in this paper—partial removal, complete removal, and drop deformations of the seal. These impacts were compared with the ambient responses to distinguish the conditions. All three impact cases show distinct characteristics in terms of sensor values, pulses, and pulse widths. For partial removal and complete removal of the seal, both cases exhibited maximum sensor values but differed in pulse and pulse width. A partially removed seal experienced the maximum number of pulses while complete removal experienced the maximum pulse width. However, if the seal experienced a drop impact, it showed lower sensor values, with the lowest pulse and pulse width. Hence, an algorithm was applied to generalize the conditions and decisions of warranty violations.

In this study, the modification of the desorption behavior of LiAlH4 by the addition of K2NbF7 was explored for the first time. The addition of K2NbF7 causes a notable improvement in the desorption behavior of LiAlH4. Upon the addition of 10 wt.% of K2NbF7, the desorption temperature of LiAlH4 was significantly lowered. The desorption temperature of the LiAlH4 + 10 wt.% K2NbF7 sample was lowered to 90°C (first-stage reaction) and 149°C (second-stage reaction). Enhancement of the desorption kinetics performance with the LiAlH4 + 10 wt.% K2NbF7 sample was substantiated, with the composite sample being able to desorb hydrogen 30 times faster than did pure LiAlH4. Furthermore, with the presence of 10 wt.% K2NbF7, the calculated activation energy values for the first two desorption stages were significantly reduced to 80 and 86 kJ/mol; 24 and 26 kJ/mol lower than the as-milled LiAlH4. After analysis of the X-ray diffraction result, it is believed that the in situ formation of NbF4, LiF, and K or K-containing phases that appeared during the heating process promoted the amelioration of the desorption behavior of LiAlH4 with the addition of K2NbF7.

In this study, three different advanced oxidation processes (AOPs), namely UV, ozone, and a combination of UV/ozone, were applied for rubber wastewater treatment. The kinetics of chemical oxygen demand (COD), total nitrogen and total phosphorous removal in the rubber wastewater treated with the AOPs were investigated. Moreover, the optimum exposure time to treat wastewater with the oxidizing agents (UV, ozone, and both) was revealed. Furthermore, the effluent after the treatment was completed was tested as a potential microalgae culture medium. The reaction rate constant was in a range of 3 × 10−4 to 1.2 × 10−3 s−1, which was higher than the results of the second-order kinetics. UV/ozone combination was the best method to treat the rubber wastewater due to its higher reaction rate constant. The results indicated that a decrease in the COD was observed, following a first-order reaction with a high determination coefficient (R2) (0.936–0.984). The COD removal was 81.44% when the UV/ozone method was used, and the removal of total nitrogen and phosphorus was 69.62% and 25.53%, respectively. Next, Spirulina platensis was cultivated in 30% (v/v) of the effluent obtained from the best method. The results showed that the microalgal growth rate and ODmax were 0.67 and 0.3 day−1, respectively. This research showed that the nutrients in wastewater effluent could be used as food supplements for microalgae production, and therefore, reduce the production costs in large scale microalgae cultivation bioprocesses.

An electroactive supercapacitor electrodes have been prepared through deposition of multi walled carbon nanotubes-polypyrrole (MWCNTs-PPy) via alternating current electrophoretic deposition method (AC-EPD). Using safranin (SAF) as co-dispersant, a stable and well-dispersed MWCNTs were obtained and the deposits of MWCNTs-PPy were successfully formed using AC peak to peak voltage of 8 V but at difference frequencies of 0.01 Hz, 4 Hz and 250 Hz. Varying the frequencies of the applied voltage has been found influencing the morphology and electrochemical properties of the deposited films. A more porous and highest deposited mass of 0.021 g was obtained at frequency of 4 Hz, while at 250 Hz the deposited mass reduces to 0.017 g. The lowest deposited mass of 0.015 g was obtained at the lowest frequency (0.01 Hz). In addition, the morphology structure of the composite film at 4 Hz shows that the PPy were well-distributed throughout MWCNTs surface. The XRD result shows the presence of amorphous PPy and graphite-like MWCNTs for all deposited samples. It has been shown that the specific capacitance values for the composites also strongly depends on the frequency of applied voltage. In the case of frequency of 4 Hz, higher values can be found at 76.08 F g ^−1 which was more than two folds increment from the lowest frequency (0.01 Hz), however at the highest frequency (250 Hz) a specific capacitance values of 65.03 F g ^−1 have been measured. The AC-EPD provides avenue for depositing nanocomposites film at relatively low apllied voltage however, there have no linear correllations been observed on the morphology and electrochemical properties of the deposited films as the frequencies of applied voltage increases.