Falling Paper

If a piece of paper falls to the ground, an alert person will observe the following  

When a few other experiments are performed, it is observed that samples of greater width rotate with lower rpm than those of smaller width. The inquisitive person will then question why the paper rotates and why the paper moves along a glide path instead of falling straight down. Answers to these questions are evident from elementary fluid meehanies. 

Rotation is caused by the alternate peeling of vertices (Karman Vortex Street) from the edges of the paper when oriented perpendicular to linear velocity vector (F) as in Fig. 12.4 (a). As each vortex leaves, it subjects the edge of the paper to a force opposite to (V) due to a 

The frequency (/) with which vortices peel alternately from the top and bottom edges of a stationary plate of width (d) oriented perpendicular to an airstream of velocity (F) [Fig. 12.4 (a)] is given by the nondimensional Strouhal Number [Eq. (6.17)]. The rotational frequency of the paper (/) will quickly adjust so that  

From Fig. 12.3, it is evident that there are five unknowns N, V, L, D, a. Hence, five independent relations are required for a complete solution  

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System falls Paper-based procedures Paper-based procedures Paper-based procedures... 

The use of iron-copper cooperative catalysis in the carbometallation of alkynes and alkenes was summarized recently in a fall paper Shirakawa, E.,... 

Figure 12.6. Possible applications of falling paper principle, (a) Dynamic kite made from expanded polystyrene bead material with S-shaped rotor wing, (b) Radar target consisting of pieces of aluminum foil rotating and translating in random directions, (c) Means for economic use of nucleating agent in a cloud seeding operation, (d) Auxiliary power driven Flettner rotor ship, (e) Axial view of Savonius wind driven rotor, (f) Sailboat with two collapsible nylon sails.

P. PRADERE and A. PEROL, paper presented at the ASNT 1996 fall conference. 

Fit securely to the lower end of the condenser (as a receiver) a Buchner flask, the side-tube carrying a piece of rubber tubing which falls well below the level of the bench. Steam-distil the ethereal mixture for about 30 minutes discard the distillate, which contains the ether, possibly a trace of unchanged ethyl benzoate, and also any biphenyl, CeHs CgHs, which has been formed. The residue in the flask contains the triphenyl carbinol, which solidifies when the liquid is cooled. Filter this residual product at the pump, wash the triphenyl-carbinol thoroughly with water, drain, and then dry by pressing between several layers of thick drying-paper. Yield of crude dry product, 8 g. The triphenyl-carbinol can be recrystallised from methylated spirit (yield, 6 g.), or, if quite dry, from benzene, and so obtained as colourless crystals, m.p. 162. ... 

Filling and sealing the Carius tube. Introduce 100-150 mg. of powdered silver nitrate into the Carius tube, either through a spill of filter -paper rolled and inserted as described on p.418, or through a small funnel, so that the powder falls freely to the bottom of the tube and does not touch or adhere to the walls. 

The simplest form of apparatus consists of a small porcelain evaporating dish covered with a filter paper which has been perforated with a number of small holes a watch glass of the same size, convex side uppermost, is placed on the filter paper. The substance is placed inside the dish, and the latter heated with a minute flame on a wire gauze or sand bath. The sublimate collects in the Fig. II, 45, 1. watch glass, and the filter paper below prevents the sublimate from falling into the residue. The watch glass may be kept cool by covering it with several pieces of damp filter... 

Add 25 g. of finely-powdered, dry acetanilide to 25 ml. of glacial acetic acid contained in a 500 ml. beaker introduce into the well-stirred mixture 92 g. (50 ml.) of concentrated sulphuric acid. The mixture becomes warm and a clear solution results. Surround the beaker with a freezing mixture of ice and salt, and stir the solution mechanically. Support a separatory funnel, containing a cold mixture of 15 -5 g. (11 ml.) of concentrated nitric acid and 12 -5 g. (7 ml.) of concentrated sulphuric acid, over the beaker. When the temperature of the solution falls to 0-2°, run in the acid mixture gradually while the temperature is maintained below 10°. After all the mixed acid has been added, remove the beaker from the freezing mixture, and allow it to stand at room temperature for 1 hour. Pour the reaction mixture on to 250 g. of crushed ice (or into 500 ml. of cold water), whereby the crude nitroacetanilide is at once precipitated. Allow to stand for 15 minutes, filter with suction on a Buchner funnel, wash it thoroughly with cold water until free from acids (test the wash water), and drain well. Recrystallise the pale yellow product from alcohol or methylated spirit (see Section IV,12 for experimental details), filter at the pump, wash with a httle cold alcohol, and dry in the air upon filter paper. [The yellow o-nitroacetanihde remains in the filtrate.] The yield of p-nitroacetanihde, a colourless crystalline sohd of m.p. 214°, is 20 g. 

Dissolve 20 g, (19 -6 ml.) of anihne in a mixture of 55 ml. of concentrated hydrochloric acid (1) and 55 ml. of water contained in a 350 ml, conical flask. Place a thermometer in the solution and immerse the flask in a bath of crushed ice (2) cool until the temperature of the stirred solution falls below 5°, Dissolve 16 g. of sodium nitrite in 75 ml. of water and chUl the solution by immersion in the ice bath add the sodium nitrite solution (3) in small volumes (2-3 ml. at a time) to the cold anihne hydrochloride solution, and keep the latter weh stirred with the thermometer. Heat is evolved by the reaction. The temperature should not be allowed to rise above 10° (add a few grams of ice to the reaction mixture if necessary) otherwise appreciable decomposition of the diazonium compound and of nitrous acid wih occur. Add the last 5 per cent, of the sodium nitrite solution more slowly (say, about 1 ml. at a time) and, after stirring for 3-4 minutes, test a drop of the solution diluted with 3-4 drops of water with potassium iodide - starch paper (4) if no immediate blue colour... 

The detector must be sensitive to the radiation falling on it, and the spectrum is very often displayed on a chart recorder. The spectrum may be a plot of absorbance or percentage transmittance (IOO///0 see Equation 2.16) as a function of frequency or wavenumber displayed linearly along the chart paper. Wavelength is not normally used because, unlike frequency and wavenumber, it is not proportional to energy. Wavelength relates to the optics rather than the spectroscopy of the experiment. 

D. A. Tillman, "The Fate of Arsenic at the Tacoma Steam Plant 2," paper presented at 1992 Fall International Symposium, American Flame Research Committee, Boston, Mass., 1992. 

J. J. Harrington and P. B. Valenti, 1976 Fall Meeting, Mmerican Institute of Mining Engineers Paper No. 76B-358, Engineering Societies Library, New... 

Constant flow jets operate by passiag a stream of charged particles contiauously through an electric field. In order for these to hit the substrate the drops have to be deflected by electrical force. Nondeflected drops fall iato a gutter. By changing the electrical field, drops can be deflected different distances and directions, so it is possible to obtain designs usiag a relatively few number of jets. Both techniques have been used widely for paper. 

Boxes Bulk boxes (Fig. 21-40) of corrugated kraft paper for dry bulk products fall into hvo broad categories large, for 0.5- to 2-ton loads, and small, for loads of 23 to 68 kg (50 to 150 lb). Large boxes are used extensively for resin shipment small ones, for certain regulated materials (such as caustic soda) and for low-bulk-density products that are assessed excessive freight rates if packed in drums. 

Figure 3.5 Schematic pH eind oxygen concentration profiles in an active tubercle. Below the magnetite shell oxygen concentration decreased sharply. pH rises above the magnetite shell due to cathodic hydroxyl-ion generation emd falls below the shell due to concentration of acidic anion, (Courtesy of National Association of Corrosion Engineers, Corrosion 91 Paper No. 84 by H. M. Herro.)...

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