The operation of the quartz crystal microbalance (QCM) in liquids is plagued by small flexural admixtures to the thickness-shear deformation. The resonator surface moves not only in the transverse direction, but also along the surface normal, thereby emitting compressional waves into the liquid. Using a simple analytical model and laser Doppler vibrometry, we show that the flexural admixtures are stronger on the fundamental mode than on the overtones. The normal amplitude of motion amounts to about 1% of the transverse motion on the fundamental mode. This ratio drops by a factor of two on the overtones. A similar dependence on overtone order is observed in experiments, where the resonator is immersed in a liquid and faces an opposite planar wall, the distance of which varies. Standing compressional waves occur at certain distances. The amplitudes of these are smaller on the overtones than on the fundamental mode. The findings can be rationalized with the tensor form of the small-load approximation.

An ANN model is proposed to predict the impurity concentration in solid diffusion process when the diffusion coefficient is not known using back-propagation learning technique based on insufficient data for analytical solution. The proposed model was very competitive against the analytical method as the results showed high-performance results with minimal amount of error comparing to the analytical method. Moreover, the proposed ANN model can be used where the analytical methods cannot as in some situations where the diffusion coefficient is not available

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The aim of this study was to improve the residential photovoltaic systems (RPVS) sector, using surveys as the research method. The research was carried out in four selected districts in Jordan, taking into account the largest population. The prepared sets of questionnaires covered a wide range of topics, divided into three parts and seven sections. The results showed that the highest use of solar energy for heating was in the Amman district, while in the Irbid and Zarqa districts photovoltaic (PV) system installations can potentially be more prospective because of high electricity and thermal energy usage. This study found the willingness of people to have a combined on-grid/off-grid PV systems, made by European and American manufacturers. However, those respondents were afraid of the high maintenance cost, the unclear lifespan of the system, doubtful reliability, and unclear warrantee of the PV systems.

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