Vibrating Mesh Research Articles

Coupled fluid structure analysis for wing 445.6 flutter using a fast dynamic mesh technology

ABSTRACTThe flow around wing 445.6 was modelled using Navier–Stokes equations and S-A model. The wing vibration and flow mesh deformation were computed using a fast dynamic mesh technology proposed by our own group. Wing 445.6 flutter was analysed through a strong coupling between the wing vibration and flow. The reduced flutter velocity was predicted and results are in good agreement with the experimental data. It is found that the subsonic flutter is mainly induced by the flow separation and the transonic and supersonic flutter are mainly caused by the oscillating shock wave and its induced flow separation. The positive aerodynamic work increases due to the oscillating shock wave when the subsonic flow becomes transonic reducing the flutter velocity. While the positive aerodynamic work induced by the oscillating shock wave decreases when the transonic flow becomes supersonic increasing the flutter velocity. That is why the transonic dip exists.

Employing DEM to study the impact of different parameters on the screening efficiency and mesh wear

Discrete element method (DEM) was employed in modeling vibrating screen, in order to study the effects of different parameters on the process efficiency and the mesh wear. A review was provided about modeling the contact force between colliding bodies. However, Hertz elastic and Kelvin–Voigt viscoelastic models were combined for the purpose of this study. Gear's approach was used in the numerical integration of the governing equations. The required programs were developed to perform the simulations using an open source code. Factors affecting numerical computations were tuned to achieve suitable values and obtain reliable results in the numerical studies. In the section of numerical studies, several simulations were built to reveal the effects of mesh slope, vibration frequency and excitation direction on the screening efficiency and wear of the screen mesh. Results related to the dependence of the efficiency on vibration frequency, excitation angle and mesh inclination were in agreement with those of data reported in open literature. However, no comparable data was seen with regards to the wear of the screen mesh. It was observed that most of the introduced parameters affect the efficiency and wear. The results were appropriately discussed and were presented graphically using diagrams and graphs. The conclusions and methodology of this study can be employed in both practical and theoretical fields.

Effects of Deposition Temperature and Doping Ratio on Structural and Optoelectronic Properties of ITO Films by Ultrasonic Vibrating Mesh Nebulizer Spray Pyrolysis

Effects of Deposition Temperature and Doping Ratio on Structural and Optoelectronic Properties of ITO Films by Ultrasonic Vibrating Mesh Nebulizer Spray Pyrolysis

Nonlinear dynamic study and vibration reduction of a power turret gear train with modified design parameters

This work presents the nonlinear dynamic characteristics and vibration reduction of a numerical control power turret three-stage gear transmission system composed of four spur gears. Considering translational and rotational motions, the nonlinear lumped-parameter and multi-degrees of freedom models of modified and unmodified transmission systems are introduced to study the dynamic behavior while the time-varying mesh stiffness and backlash of gear mesh pairs are involved as internal excitations. For the requirement of high speed and low vibration, high contact ratio by modifying design parameters is suggested in this study. By numerical method, the dynamic vibration responses are calculated. Results in the time and frequency domains show that the vibration amplitudes and mesh forces are efficiently decreased after modification. The influences of key parameters, such as mesh stiffness, damping, backlash, and torque on the dynamic response are also studied here. To demonstrate the effectiveness of the proposed model, the vibration tests are conducted by two physical prototypes of the power turret. The values of vibration acceleration at different tests points and speeds are obtained and analyzed. Experimental results validate that the vibration of turret is decreased by the design improvement of gear system.

In situ forming nimodipine depot system based on microparticles for the treatment of posthemorrhagic cerebral vasospasm

The present study was conducted to examine the feasibility of nimodipine-loaded PLGA microparticles suspended in Tisseel™ fibrin sealant as an in situ forming depot system. This device locally placed can be used for the treatment of vasospasm after a subarachnoid hemorrhage. Microparticles were prepared via spray-drying by using the vibration mesh spray technology of Nano Spray Dryer B-90. Spherically shaped microparticles with different loadings and high encapsulation efficiencies of 93.3–97.8% were obtained. Depending on nimodipine loading (10–40%), the particle diameter ranged from 1.9±1.2μm to 2.4±1.3μm. Thermal analyses using DSC revealed that nimodipine is dissolved in the PLGA matrix. Also, fluorescent dye loaded microparticles were encapsulated in Tisseel™ to examine the homogeneity of particles. 3D-pictures of the in situ forming devices displayed uniform particle homogeneity in the sealant matrix. Drug release was examined by fluorescence spectrophotometry which demonstrated a drug release proportional to the square root of time. A prolonged drug release of 19.5h was demonstrated under in vitro conditions. Overall, the nimodipine in situ forming device could be a promising candidate for the local treatment of vasospasm after a subarachnoid hemorrhage.

Towards an inhalative in vivo application of immunomodulating gelatin nanoparticles in horse-related preformulation studies

Delivering active ingredients using biocompatible and biodegradable carriers such as gelatin nanoparticles (GNPs) to the lung constitutes a promising non-invasive route of administration. However, the pulmonary delivery of nanoparticle-based immunotherapy is still a field that requires more clarification.In this study, GNPs loaded with cytosine-phosphate-guanine oligodeoxynucleotides (CpG-ODN)-loaded and plain GNPs were aerosolised either by a conventional pressured metered dose inhaler (pMDI) or by active or passive vibrating-mesh (VM) nebulisers. GNP sizes after nebulisation by active and passive VM nebulisers were 248.2 ± 7.34 and 222.3 ± 1.42 nm, respectively. GNP concentrations after aerosolisation were found consistent and second-stage particle deposition in an impinger was up to 65.68 ± 11.2% of the nebulised dose. VM nebulisers produced high fine particle fractions, while pMDIs did not. Nebulised CpG-ODN-loaded GNPs remained capable to stimulate IL-10 release (225.2 ± 56.3 pg/ml) in vitro from equine alveolar lymphocytes. Thus, a novel system for pulmonary GNP-mediated immunotherapy in vivo was established.

Delivery Efficacy of a Vibrating Mesh Nebulizer and a Jet Nebulizer under Different Configurations

Jet nebulizers coupled to spacers are frequently used to promote drug lung deposition, but their clinical efficacy has not been established. Few in vivo studies have been performed with mesh nebulizers, commonly used to nebulize antibiotics. Our study compared inhaled mass and urinary drug concentration of amikacin by using three different nebulizer delivery configuration systems: a standard unvented jet nebulizer (Sidestream(®)) used alone or coupled to a 110-mL corrugated piece of tubing and a vibrating mesh nebulizer (e-Flow rapid(®)). The inhaled mass of amikacin was assessed using the residual gravimetric method. Delivery efficacy was evaluated by assessing amikacin urinary drug concentration in six healthy spontaneously breathing volunteers. Urinary amikacin was monitored by fluorescent polarization immunoassay then cumulative excreted amount and antibiotic elimination rate were calculated. The total daily amount of amikacin urinary excretion (Cu) was almost twice as high with eFlow rapid(®) compared to Sidestream(®) used alone; intermediate values being observed when the device was coupled to a corrugated piece of tubing. The latter configuration was also associated with a higher total daily amount of amikacin urinary excretion. In vivo drug output rate was around threefold higher with the eFlow Rapid(®) than with the Sidestream(®) used in any configuration. These results were concordant to those obtained with in vitro analysis comparing inhaled mass of amikacin for the three nebulizers. The elimination constant (Ke) and the mass median aerodynamic diameter (MMAD) did not differ between the three devices. In conclusion, the vibrating mesh nebulizer is more efficient, promoting larger urinary drug concentration and drug output. Coupling a corrugated piece of tubing to the standard jet nebulizer favors delivery efficacy.

Application of a Droplet Evaporation Model to Aerodynamic Size Measurement of Drug Aerosols Generated by a Vibrating Mesh Nebulizer

Droplet evaporation has been known to bias cascade impactor measurement of aerosols generated by jet nebulizers. Previous work suggests that vibrating mesh nebulizers behave differently from jet nebulizers. Unlike jet nebulizers, vibrating mesh nebulizers do not rely on compressed air to generate droplets. However, entrained air is still required to transport the generated droplets through the cascade impactor during measurement. The mixing of the droplet and entrained air streams, and heat and mass transfer occurring downstream determines the final aerosol size distribution actually measured by the cascade impactor. This study is aimed at quantifying the effect of these factors on droplet size measurements for the case of vibrating mesh nebulizers. A simple droplet evaporation model has been applied to investigate aerodynamic size measurement of drug aerosol droplets produced by a proprietary vibrating mesh nebulizer. The droplet size measurement system used in this study is the Next Generation Impactor (NGI) cascade impactor. Comparison of modeling results with experiment indicates that droplet evaporation remains a significant effect when sizing aerosol generated by a vibrating mesh nebulizer. Results from the droplet evaporation model shows that the mass median aerodynamic diameter (MMAD) measured by the NGI is strongly influenced not only by the initial droplet size, but also by factors such as the temperature and humidity of entrained air, the nebulizer output rate, and the entrained air flow rate. The modeling and experimental results indicate that the influence of these variables on size measurements may be reduced significantly by refrigerating the impactor down to 5°C prior to measurement. The same data also support the conclusion that for the case of nebulized drug solutions, laser diffraction spectrometry provides a meaningful droplet sizing approach, that is simpler and less susceptible to such droplet evaporation artifacts.

A Novel Submicron Formulation of Nebulized Budesonide Delivered by a Vibrating Mesh Nebulizer Significantly Improves Delivery Efficiency at One-Fifth of the Nominal Dose of both Pulmicort Respules® and a Generic Budesonide Suspensions Delivered via a Jet Nebulizer - A Potentially Important Advancement in Pediatric Asthma

RATIONALE: Innovative aerosol generators can improve nebulization efficiency of aqueous suspensions by eliminating large residual volumes and concentrating effects associated with jet nebulizers. A novel submicron budesonide dispersion (sBUD) has been developed for use with these innovative aerosol generators, which are not approved for use with marketed aqueous suspensions used to treat of pediatric asthma.

Comparative Analysis of Methods to Measure Aerosols Generated by a Vibrating Mesh Nebulizer

Different approaches have been employed for in vitro assessment of the aerosol particle size generated by inhalation devices. In this study, aerosols from the Omron MicroAir vibrating mesh (VM) nebulizer were measured by cascade impaction (CI) using the MSP Next Generation Pharmaceutical Impactor (NGI), the ThermoAndersen Cascade Impactor (ACI), and by time-of-flight (TOF) analysis with the TSI 3321 Aerodynamic Particle Sizer Spectrometer (APS). The VM nebulizer was evaluated with sodium fluoride (NaF; 2.5%) and with generic albuterol (0.083%). Aerosol particle size (MMAD), respirable fractions (RF < 5 microm), and fine particle fractions (FPF < 3.3 microm) were determined with each method at room temperature (RT) and 4 degrees C using 50% average relative humidity. By NGI at either RT or 4 degrees C, aerosol particle sizes were similar for both NaF and albuterol (4.3-4.5 microm MMAD) with 55-61% RF and 27-43% FPF. With ACI, the distribution of particles at RT was similar except at the extremes of the dispersion and the MMAD was smaller (3.3 microm MMAD; p = 0.03). At 4 degrees C, particle sizes determined by ACI results were similar to the NGI (MMAD 4.1 microm; p > 0.05). TOF analysis by APS with albuterol gave significantly larger calculated MMAD (cMMAD) than either CI method (7.2 microm; p < 0.001). TOF measurements of nebulized albuterol at RT and 4 degrees C were equivalent. In summary, the results of VM nebulized NaF and albuterol were more consistent and generally equivalent when determined by NGI (at RT and 4 degrees C) and ACI analysis (at 4 degrees C). In contrast, aerosol particle sizes measured by TOF in the APS at both RT and 4 degrees C were larger than results obtained by CI. Differences in aerosol particle distribution obtained by different analysis methods should be considered while evaluating the in vitro performance of VM nebulizers.

DEVELOPMENT OF SMART STRUCTURE SYSTEMS FOR HELICOPTER VIBRATION AND NOISE CONTROL

Helicopters are susceptible to high vibratory loads, excessive noise levels and poor flight stability compared to fixed-wing aircraft. The multidisciplinary nature of helicopter structures offers many opportunities for the innovative smart structure technology to improve helicopter performance. This paper provides a review of smart structures research at the National Research Council Canada for helicopter vibration and cabin noise control applications. The patented Smart Spring approach is developed to vary the blade impedance properties adaptively to reduce the vibratory hub loads transmitted to the fuselage by vibration reduction at the source. A smart gearbox strut and active structural acoustic control technologies are investigated to suppress the vibration and tonal gear meshing noise into the cabin either by modifying the vibration load transmission path, or weakening the coupling between exterior and cabin acoustic fields. Two adaptive seat mount concepts are proposed to reduce the vibration of the aircrew directly to improve ride quality of the vehicle.