Ionic wind

Electric Wind By virtue of the momentum transfer from gas ions moving in the electrical field to the surrounding gas molecules, a gas circiilation, known as the electric or ionic wind, is set up between the electrodes. For conditions encountered in electrical precipitators, the velocity of this circulation is on the order of 0.6 m/s. (2 ft/s). Also, as a result of this momentum transfer, the pressure at the collecting eleclrode is slightly higher than at the discharge electrode (White-head, op. cit., p. 167). 

The earliest information dealing with this phenomenon dates back to 600 B.c. It was found that a piece of amber after it had been rubbed was able to attract small fibers. More recent observations are from the 17th century, when William Gilbert noticed that amber, sulfur, and other dielectrics charged by friction could attract smoke. Similar observations were made by Boyle (1675) and Otto von Guericke (1672). Francis Hauksbee (1709) reported that he had discovered a phenomenon which is now called ionic wind or electric wind. Ionic wind and the glow from the corona discharge was discussed by Isaac Newton (1718). 

For simplicity of the model, it is assumed that the natural convection, radiation, and ionic wind effect are ignored. The ignorance of the radiation loss from the spark channel during the discharge may be reasonable, because the radiation heat loss is found to be negligibly small in the previous studies [5,6]. The amount of heat transfer from the flame kernel to the spark electrodes, whose temperature is 300 K, is estimated by Fourier s law between the electrode surface and an adjacent cell. 

In order to determine the relationship between the force of the ionic wind on a plane surface and the voltage supplied to the electrode at a frequency of 400 Hz, we used a torsion balance with metal and glass pans. The force of the ionic wind was found to be proportional to the potential supplied to the electrode. For example, with a potential of 2 kV, the force of the ionic wind was 0.2 mgf when the potential was increased to 3 kV, the force increased linearly, reaching a level of 3.2 mgf. 

If the only cause of dust-particle detachment were the ionic wind, the efficiency of particle removal should increase with increasing electrode potential. This however, is not in accord with the actual facts (Fig. VII.5). With relatively small distances between the electrode and the treated surface (1-3 mm), the clean spot diameter increases as the electrode potential is increased up to 3.2 kV, but further increases in potential fail to produce any increase in the clean spot... 

Mechanism of Particle Detachment. Whereas on subjection to a steady dc electric field the particles are removed instantaneously from the surface and fly to the electrode, on subjection to an ac field the adhering particles move over the surface from the center to the periphery of the cleaned spot, and the dust is blown off very much as in the case of an air jet. This is because the gas is ionized at the point of the needle electrode and an ionic wind develops [467]. 

Fig. X.IO. Force of ionic wind as a function of the potential applied to the electrode during the cleaning of glass (a) and metal surfaces (b).

In lithium-based cells, the essential function of battery separator is to prevent electronic contact, while enabling ionic transport between the positive and negative electrodes. It should be usable on highspeed winding machines and possess good shutdown properties. The most commonly used separators for primary lithium batteries are microporous polypropylene membranes. Microporous polyethylene and laminates of polypropylene and polyethylene are widely used in lithium-ion batteries. These materials are chemically and electrochemically stable in secondary lithium batteries. 

Figure 27-5 (A, B) Two possible models of the 30-nm chromatin fiber.55 (A) Thoma et al.85 (B) Woodcock et al.6i 87 The fully compacted structure is seen at the top of each figure. The bottom parts of the figures illustrate proposed intermediate steps in the ionic strength-induced compaction. (C) Possible organization of the DNA within a metaphase chromosome. Six nucleosomes form each turn of a solenoid in the 30-nm filament as in (A). The 30-nm filament forms 30 kb-loop domains of DNA and some of these attach at the base to the nuclear matrix that contains topoisomerase II. About ten of the loops form a helical radial array of 250-nm diameter around the core of the chromosome. Further winding of this helix into a tight coil 700 nm in diameter, as at the top in (C), forms a metaphase chromatid. From Manuelidis91.

The pte value of 4.4 (see Table 3-2) for DNOC suggests that in natural waters with a pH 5-9, >50% of the compound exists in the ionic state at pH 5 and the percent of ionic forms increases as the pH increases. In addition to this dissociation effect, DNOC may form H-bonds in water (EPA 1979), reducing its vapor pressure and chances of volatility from water. Using a Henry s law constant value of 1.4x10" atm-m /mole (Shen et al. 1982a, 1982b) and an estimation method (Thomas 1990), the estimated volatilization half-life of DNOC from a typical river 1 meter deep, with a current speed of 1 m/second, and an overhead wind speed of 3 m/second, is 36 days. Therefore, direct volatilization from water will not be significant for DNOC. 

Winding oils for texturized yarns, non-ionic, antistatic, good washability. 

Following a nuclear accident, deposited radionuclides may be present in different physico-chemical forms, ranging from mobile low molecular mass (LMM) ionic species to inert high molecular mass (HMM) colloidal forms or particles. Even in areas far from the actual site, the relative fraction of radionuclides associated with HMM formed in rain-water may be substantial (Salbu, 1988). The size distribution patterns of radionuclides deposited, the composition of the fallout, level of activities and the activity ratios, will depend on the accident scenario, course of event, distance from the source, wind dispersion and climatic or microclimatic conditions. Spatial and temporal variations in the behaviour of deposited radionuclides with respect to mobility and bioavailability are to be expected and may in part be attributed to differences in the physico-chemical forms of radionuclides in the fallout, at least during the first years after deposition (Salbu et al., 1994). 

---