Squeeze-film levitation characteristics of plates excited by piezoelectric actuators

A small mass is levitated by a vibrating plate with an arrangement of four piezoelectric actuators that generate a squeeze-film in the gap between the plate and the mass. Different arrangements of actuators and plate design are explored using simulation in order to produce better performance

Plate actuator vibration modes for levitation

The design of an aluminium or steel plate of various thicknesses for achieving levitation of a small aluminum disk is investigated by simulation using ANSYS. Each plate design is excited by an arrangement of four hard piezoelectric actuators driven with an AC voltage, which produces a centre displacement for generating a squeeze-film in the gap between the vibrating plate and the disk. Physical experiments show levitation conditions for one of the designs

Development of Afatinib lipid nanoparticles targeting non small cell lung cancer

Lung cancer is the most common cause of cancer-associated mortality in males and females globally. Widespread research is currently focused on the development of novel approaches for targeting non small cell lung cancer with different therapeutic nanotechnologies. In this study, a sensitive and selective HPLC method was developed for the quantification of afatinib (AFT) in formulations. Novel drug delivery systems based on cationic (CL) and pH-sensitive liposomes (PSL) for AFT were developed, with different ratios of lipid to AFT, using a film hydration method. The obtained liposomes had a small particle size of less than 50 nm with a low polydispersibilty index and acceptable zeta potential. The highest Encapsulation Efficiency (EE%) of AFT reached 43.20%, 50.20%, and 52.01% for NL (Non targeting liposomes), PSL, CL, respectively at the 1:0.5 ratio of AFT: lipids. The in vitro release study confirmed that all formulations had sustained release profiles in pH 7.4. However, in acidic pH values, PSL exhibited fast release. The stability study, conducted at 4°C and 25°C for 1 month, showed that the characteristics of liposomes in liquid form did not change significantly over this period. In vitro cytotoxicity studies revealed high antitumor activity of PSL on all cell lines at 0.75 µM concentration after 24 h exposure, based on using the Annexin V assay. A proteomics study identified 12 proteins which can be used as biomarkers capable of prediction of treatment response and choice of therapy for two different types of human NSCLC cells (H-1975 and H-1650). Spray drying was used to produce nanocomposite microparticles (NCMPs) using L-leucine and coated using different ratios of chitosan for the optimized PSL NPs. The particles had a corrugated surface except at high CH ratios, where more homogenous and smooth particles with some small indentations were obtained. The powder properties showed good flow properties and reproducible size. Coated NCMPs showed a delayed drug release profile compared to PSL NPs and the best correlation with the Higuchi model. A stability study at 40°C/ 75% ± 5% relative humidity (RH) showed large changes in the drug content for all coated NCMPs powders. Analysis of the in vitro aerosolization performance demonstrated a mass median aerodynamic diameter (MMAD) of 3.24 – 5.85 µm and fine particle fraction (FPF%) of 54.20-33.66%. The particle size of the reconstituted powders was ˂ 100 nm, which is within the size range to be effectively taken up by tumor cells. Assessment of the stability of spray dried liposomes after 3 months of storage at 40 °C/75% RH, showed that fusion and aggregation of the liposomes occurred in all samples tested. The C1NCMPs (lipid: LEU: CH ratio of 1:1.5:0.5) exhibited the highest FPF (51.2%) and fine particle dose (FPD) (40.0 µg of AFT) indicating deep lung deposition. Further cell viability studies of C1 NCMP, at a concentration of 0.75 μM on H-1975 NSCLC cell line showed a good toxicity profile comparable to PSL nanoparticles (NPs). The obtained data indicates that pulmonary delivery of PSL NCMPs is a potential new clinical strategy for better targetability and delivery of AFT for the treatment of lung cance

Plate vibration characteristics for squeeze film levitation

Squeeze-Film Levitation of a small object placed on a vibrating plate is investigated for 14 plate designs using simulation. Each plate is excited by an arrangement of four piezoelectric actuators driven by an ac voltage with dc offset. Physical experiments show plate mode shapes and dynamic deformation, plus disk levitation for one of the designs

Modelling Influence of Poisson's Contraction on Squeeze Film Levitation of Planar Objects

Poisson's contraction effect is utilised to generate squeeze film levitation and is investigated through a computer model and validated experimentally. A finite element model (ANSYS) is verified by the experimental testing of five different plate designs. Each plate is subjected to uniaxial plain stress by an arrangement of two hard piezoelectric actuators bounded to the bottom of the plate and driven with DC and AC voltages. It is observed that a pulsating dimple or crest shape along the longitudinal axis in the central area of the plate is created due to Poisson's contraction, generating a squeeze-film between the plate and a levitated object. The separation distance between the floating planar object and the plate is analysed using computational fluid dynamics (ANSYS) and experimentally measured by a laser sensor. A good agreement has been found between model predictions and experimental results

Investigation into squeeze-film induced levitation of light objects

The performance of a system consisting of a thin rectangular plate under plane stress due to the action of PT actuators, thus subjected to the Poisson’s contraction effect, and a light circular object freely floating over it was studied both numerically and experimentally. The results show that performance of the system is influenced by a few factors, including the magnitude of elastic deformation of the plate and the electrostatic action of the PZTs attached to the plate, which combine to form oscillating dimples created by the Poisson’s effect to separate the object from the plate with a film of compressible fluid. The importance of operating frequency of PZTs, shape and size of the dimple, offset and amplitude voltage under which PZTs operate, and distribution of PZTs on the plate’s surface were all examined theoretically and verified experimentally. The plate was made of aluminium and stainless steel in order to find out the importance of the material’s energy absorption rate for the effectiveness of squeeze-film induced levitation. The agreement between theoretical models and experimental measurements proved to be quite satisfactory

Effect of Emulsified Asphalt on Expansive Soil Strength and Swelling

Some clay soils classified as extended soils threaten the structures resting on them. Many additives are available to improve the properties of expanded soils. This study tries to investigate the consequences of wetting-drying cycles on the swelling behavior of modified expansive clayey soils under laboratory conditions by modifying expansive clayey soil samples using emulsified asphalt. Five different percentages of emulsified asphalt were used: (2, 4, 6, 8, and 10) %. The natural and treatment soils were tested for classification, specific gravity, compaction characteristics, free swell and swell pressure, consolidation, and compressive strength. The liquid limit and plasticity index have been lowered by adding Emulsified Asphalt. After that, the effects of Emulsified Asphalt on undrained shear strength characteristics (cohesion and friction angle) have been studied. The results revealed that when the emulsified asphalt content was increased to 10%, the swelling pressure and swelling potential decreased by 58 and 78 %, respectively. The swell and shrink improvement factor for the 10% emulsified asphalt addition is always larger than 75%. As the duration of wetting-drying cycles increased, the swelling pressure and swelling potential values were also reduced. The plastic limit, on the other hand, increased as the Emulsified Asphalt content increased. Increasing the amount of Emulsified Asphalt increased the maximum dry unit weight values, whereas the optimum water contents increased. It was concluded that emulsified asphalt stabilization may be useful for expansive clay as it improves compressive shear strength

Prototype Design and Feasibility Analysis for Self-Levitated Conveying

In order to avoid friction and scratching when conveying object, an acoustic levitation prototype was designed to verify the feasibility. The modal shapes and the forced harmonic shapes of the prototype are obtained by an ANSYS coupled field computation with a one-quarter symmetry model and the levitation capacity was assessed by the use of groups of simulation and physical testing. The simulation results showed that the pure flexural and mixed flexural wave shapes with different wave numbers existed at some specific frequency. The amplitude in the central point of an aluminum plate having four piezo-electric discs glued to the bottom surface was simulated for a frequency spectrum. The experimental results confirmed the theoretical results and the feasibility of the prototype and confirm that objects can be floated at several resonant frequencies under forced vibrating condition. The system can provide largest bearing capacity when both the piezoelectric disc and the plate resonances coincide

Fractal Dimension Analysis of Transient Visual Evoked Potentials: Optimisation and Applications

Purpose The visual evoked potential (VEP) provides a time series signal response to an external visual stimulus at the location of the visual cortex. The major VEP signal components, peak latency and amplitude, may be affected by disease processes. Additionally, the VEP contains fine detailed and non-periodic structure, of presently unclear relevance to normal function, which may be quantified using the fractal dimension. The purpose of this study is to provide a systematic investigation of the key parameters in the measurement of the fractal dimension of VEPs, to develop an optimal analysis protocol for application. Methods VEP time series were mathematically transformed using delay time, τ, and embedding dimension, m, parameters. The fractal dimension of the transformed data was obtained from a scaling analysis based on straight line fits to the numbers of pairs of points with separation less than r versus log(r) in the transformed space. Optimal τ, m, and scaling analysis were obtained by comparing the consistency of results using different sampling frequencies. The optimised method was then piloted on samples of normal and abnormal VEPs. Results Consistent fractal dimension estimates were obtained using τ = 4 ms, designating the fractal dimension = D2 of the time series based on embedding dimension m = 7 (for 3606 Hz and 5000 Hz), m = 6 (for 1803 Hz) and m = 5 (for 1000Hz), and estimating D2 for each embedding dimension as the steepest slope of the linear scaling region in the plot of log(C(r)) vs log(r) provided the scaling region occurred within the middle third of the plot. Piloting revealed that fractal dimensions were higher from the sampled abnormal than normal achromatic VEPs in adults (p = 0.02). Variances of fractal dimension were higher from the abnormal than normal chromatic VEPs in children (p = 0.01). Conclusions A useful analysis protocol to assess the fractal dimension of transformed VEPs has been developed