Effect of Aerosols on Climate Change

A modified two-stream approximation is presented, which includes the effect of solar zenith angle and is applicable to study the effect of aerosols on both regional and global climate changes. More realistic results are derived. A reasonable critical value of 0.8 for aerosol single scattering albedo to determine whether the aerosols will heat or cool the climate is derive

Application of Stable Operating Criterion to Grating Tuned Strong External Feedback Semiconductor Lasers

Stability analysis is done by applying criterion dnQ((o)/cfco\u3e0 for grating tuned strong external feedback semiconductor lasers. The resulting stable and unstable operating ranges agree well with experiment results

Modification of Surface Properties of Polymeric Materials

Polymeric materials are successfully used in virtually all industries ranging from semiconductors, and coatings, to household appliances, automotive, and biomedical implants. Polymers generally have excellent bulk physical and chemical properties. However, certain properties of polymers such as low surface energy, low wettability, and high electrical resistivity sometimes limit their applications. Changing the bulk formulation of the polymers can alter some of these properties, but in general this is not acceptable as it can affect desirable bulk properties. Surface modification techniques have been used to alter polymer surfaces without affecting the bulk properties of the material. Most polymers have very high surface and bulk resistivity, which causes static charge problems in many applications. One such application is powder coating where the accumulation of excess charge causes an adverse impact on the appearance of the powder layer. Similarly the buildup of static charge during processing and application of polymer films in packaging industries is often harmful to sensitive electronic components such as those used in the computer industry. Charge buildup may be reduced by surface modification to control the surface resistivity. In this work, atmospheric plasma treatment was used to modify the surface resistivity of polymers. The surface resistivity of polyethylene film decreased from 1.28x1O16 Q/D to 5.73x1O15 Q/U at 18% RH

Study of Velocity and Materials on Tribocharging of Polymer Powders for Powder Coating Applications

Electrostatic powder deposition is widely used in a plethora of industrial-applications ranging from the pharmaceutical and food.industries, to farm equipment and automotive applications. The disadvantages of this technique are possible back corona (pin-like formations) onset and the Faraday penetration limitation (when the powder does not penetrate in some recessed areas). A possible solution to overcome these problems is to use tribochargers to electrostatically charge the powder. Tribocharging, or contact charging while two materials are in contact, is related to the work function difference between the contacting materials and generates bipolarly charged particles. The generation of an ion-free powder cloud by tribocharging with high bipolar charge and an overall charge density of almost zero, provides a better coverage of the recessed areas. In this study, acrylic and epoxy powders were fluidized and charged by passing through stainless steel, copper, aluminum, and polycarbonate static mixers, respectively. The particle velocity was varied to determine its effect on the net charge-to-mass ratio (QIM) acquired by the powders. In general, the Q/M increases rapidly when the velocity was increased from 1.5 to 2.5 m/s, remaining almost constant for higher velocities. Charge separation experiments showed bipolar charging for all chargers

Effect of Charge on the Deposition of Electrostatically Charged Inhalable Aerosol in Lung Model

Inhalable drugs are widely used for treating lung diseases such as asthma, emphysema, and cystic fibrosis. The aerosol particles in these inhalable drugs may be charged electrostatically. The deposition of these inhaled therapeutic aerosol particles in the different regions of the lung depends on the particle aerodynamic diameter, electrostatic charge distribution, particulate number density, breathing rate, aerodynamics of the lung, ambient temperature, and relative humidity (RH). The primary mechanisms for lung deposition of inhaled particles are impaction, gravitational settling, diffusion, interception, and electrostatic attraction. To simulate lung deposition, electrostatically charged aerosol particles are introduced through a throat section into a glass bead lung model. The E-SPART analyzer was used to measure aerosol deposition as a function of the particle charge and size. Experiments were carried out to determine the increase in deposition efficiency as a function of the net charge-to-mass ratio (Q/M) of aerosol particles. Using a fairly monodisperse aerosol of 5.0 um count median aerodynamic diameter, it was found that the total deposition efficiency increased from 54% to 91% when Q/M increased from 0.5 to 9.67 |muC/g. The data show that enhanced delivery of the therapeutic aerosol in the lung can be achieved by controlling the electrostatic charge on the inhaled aerosol particles

Alumina and Synthesis Intermediates Derived from Diethylkaluminum Amide, Benzaldehyde and Water

The reaction of diethylaluminum amide [Et2AINH2] with benzaldehyde in toluene produces a solution of ethylaluminoxane polymer [EtAlO] and hydrobenzamide [PhCH=NCH(Ph)N=CHPh]. Alumina then is precipitated by the addition of water. Transition aluminas that may be useful in heterogeneous catalyst applications are obtained after calcining. Details of the chemistry of solution intermediates according to 1H NMR and the properties of the alumina product according to surface area analyses and powder x-ray diffraction are described

Reduction of Dendrite Formations to Improve the Appearance of the Powder Cured Films for Automotive Industry

The appearance of powder-coated films is dependent upon powder chemistry and spraying parameters. One of the most important physical factors controlling the powder film appearance is the microdeposition of the powder particles on the grounded substrate. During the electrostatic deposition of powder, the formation of dendrites and agglomerates was observed; these formations have an adverse effect on the final film appearance and their elimination may result in smoother and glossier films. Dendrites are generated due to bipolar charging and inter-particulate electrostatic attractive forces. The corona charging technique is mostly used in industrial powder coating applications. At low corona voltages (- 40 to - 60 kV) a greater degree of bipolar charging was observed compared to that at higher voltages (- 80 to - 100 kV). At the higher voltages, the increase n number of ions produces a more unipolar charging and higher charge-to-mass ratios. As the film builds up, the powder transfer efficiency decreases as the repulsion forces between oncoming charged particles and the already deposited powder layer increase. By controlling the deposition patterns, the final film appearance can be improved. The smoothest films were obtained when the voltage was ramped from - 60 to - 100 kV. Another method to reduce dendrite formations was to deposit powder particles charged unipolarly by first separating them from the oppositely charged ones by using a charge separator

Electrostatic Charge Polarity Effect on Respiratory Deposition in the Glass Bead Tracheobronchial Airways Model

The effects of unipolar and bipolar electrostatic charges on the deposition efficiency of therapeutic aerosols in the physical model of human tracheobronchial (TB) airways have been investigated. Respirable size aerosol particles were generated by a commonly prescribed and commercially available nebulizer and charged by a corona charger and then their size and charge distributions were characterized by an Electronic Single Particle Aerodynamic Relaxation Time analyzer to study the drug aerosol particles\u27 deposition pattern. The experiments were performed with a glass bead tracheobronchial model (GBTBM) (physical model) which was designed and developed based upon widely used and adopted dichotomous lung morphometric data presented in the Ewald R. Weibel model. The model was validated with the respiratory deposition data predicted by the International Commission on Radiological Protection and the United States Pharmacopeia (USP) approved Andersen Cascade Impactor (ACI). Unipolarly and bipolarly charged particles were characterized for two configurations: a) without TB model in place and b) with TB model in place. Findings showed that the deposition of unipolarly charged particles was about 3 times of the bipolarly charged particles. It was also found that bioengineered therapeutic aerosols with good combinations of aerodynamic size and electrostatic charge are good candidates for the administration of respiratory medicinal drugs

Electrostatic Charge Polarity Effect on Respiratory Deposition in the Glass Bead Tracheobronchial Airways Model

The effects of unipolar and bipolar electrostatic charges on the deposition efficiency of therapeutic aerosols in the physical model of human tracheobronchial (TB) airways have been investigated. Respirable size aerosol particles were generated by a commonly prescribed and commercially available nebulizer and charged by a corona charger and then their size and charge distributions were characterized by an Electronic Single ParticleAerodynamic Relaxation Time analyzer to study the drug aerosol particles\u27 deposition pattern. The experiments were performed with a glass bead tracheobronchial model (GBTBM) (physical model) which was designed and developed based upon widely used and adopted dichotomous lung morphometric data presented in the Ewald R. Weibel model. The model was validated with the respiratory deposition data predicted by the International Commission on Radiological Protection and the United States Pharmacopeia (USP) approved Andersen Cascade Impactor (ACI). Unipolarly and bipolarly charged particles were characterized for two configurations: a) without TB model in place and b) with TB model in place. Findings showed that the deposition of unipolarly charged particles was about 3 times of the bipolarly charged particles. It was also found that bioengineered therapeutic aerosols with good combinations ofaerodynamic size and electrostatic charge are good candidates for the administration of respiratory medicinal drugs