Warping

Part of the land around the Humber estuary is warpland and the best is probably that in the lower Trent valley. Most of this work was done in the nineteenth century. It is too expensive to consider now. 

The texture of blowaway sandy soils and Black Fen soils can be improved by applying 400-750 t/hectare of clay or marl (a lime-rich clay). If the subsoil of the area is clay, it can be dug out of trenches and roughly scattered by a dragline excavator. In other cases, the clay is dug in pits and transported in special lorry spreaders. Rotary cultivators help to spread the clay. If the work is done in late summer or autumn, the winter frosts help to break down the lumps of clay. As a practice, it is no longer considered economical. 

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Figure Bl.14.1. Spin warp spin-echo imaging pulse sequence. A spin echo is refocused by a non-selective 180° pulse. A slice is selected perpendicular to the z-direction. To frequency-encode the v-coordinate the echo SE is acquired in the presence of the readout gradient. Phase-encoding of the > -dimension is achieved by incrementmg the gradient pulse G...

Edelstein W A, Hutchison J M S, Johnson G and Redpath T W 1980 Spin warp NMR imaging and appiications to human whoie-body imaging B 25 751-6... 

It is used in adhesives, paper coating and sizing, and textile warp size and finishing applications. 

Glass-fiber-reinforced (increased stiffness and tensile strength) and mineral filled (reduced shrink and warp) grades also have been developed. 

Commercially, elastomeric fibers are almost always used in combination with hard fibers such as nylon, polyester, or cotton. Use levels vary from a low of about 3% in some filling stretch cotton fabrics to a high of about 40% in some warp-knit tricot fabrics. Raschel fabrics used in foundation garments normally contain 10—20% spandex fiber. 

The high speed continuous filament process (69) was first used for manufacturing in 1974, and this enabled the yam production rates to be raised from 150 to 380 m /min. This system uses a pair of net conveyor belts to protect and transport an overfed warp of yams through washing and drying. 

With disk diameters above 5.25 in., all parameters, eg, water absorption and thermal expansion, become more critical which aggravates the expansion or warp of disks. If in the future disk rotation speeds have to be increased significantly to boost data transfer rates, higher demands will be placed on warp (tilt angle) and modulus to avoid creeping (ie, irreversible elongation in radial direction). A survey of the requirement profile for the substrate material of optical disks is given in Table 5 (182,186,187,189). 

Poly(methyl methacrylate). PMMA offers distinct advantages over BPA-PC with respect to significandy lower birefringence, higher modulus, and lower costs, but has not been successhil as a material for audio CDs and CD-ROM as well as a substrate material for WORM and EOD disks because of its high water absorption (which makes it prone to warp) and its unsuitabiUty for metallising, and less so because of its low resistance to... 

Table 9 compares the most important properties of substrate materials based on BPA-PC, PMMA, and CPO (three different products) (216,217). The future will prove if the current disadvantages of CPO against BPA-PC regarding warp, processibiUty (melt viscosity), and especially cost can be alleviated. CycHc polyolefins (CPO) and, especially cycloolefin copolymers (COC) (218) and blends of cycloolefin copolymers with suitable engineering plastics have the potential to be interesting materials for substrate disks for optical data storage. 

Fabric-Based Grades. Grade C is made from cotton fabric weighing over 140 g/m (4 oz/yd ). The maximum thread count in any ply is 28/cm (72/in.) in the fiU direction, and the maximum total thread count in the warp and fiU directions is 56/cm (140/in.). Heavier fabrics provide higher impact strength but rougher machined edges. Its use for electrical apphcations is not recommended. 

Lea.dAnodes. A principal use for lead—calcium—tin alloys is lead anodes for electrowinning. The lead—calcium anodes form a hard, adherent lead dioxide layer during use, resist corrosion, and gready reduce lead contamination of the cathode. Anodes produced from cast lead—calcium (0.03—0.09 wt %) alloys have a tendency to warp owing to low mechanical strength and casting defects. 

Flame spray metallising is widely used for the protection of metal against corrosion, especially for in situ protection of stmctural members. The principal metal used for spraying of plastics is sine. Aluminum and copper are also used. If the distance from the part is too great, the zinc solidifies before it touches the part and adhesion is extremely poor. If the molten zinc oxidizes, conductivity and adhesion are poor. If the distance is too short, the zinc is too hot and the plastic warps or degrades. These coatings are not as dense as electrically deposited coatings because of numerous pores, oxide inclusions, and discontinuities where particles have incompletely coalesced. 

When selecting a particular paster adhesive, coating material, and coating process for sohd fiber packaging, the fact that sohd fiberboard lacks the open-flute stmcture (to facihtate exit of moisture from internal phes of paperboard) should be considered. It is generally desirable to minimize the amount of process water added with the adhesive or coating with sohd fiber products. Moisture trapped in the filler phes can result in pin holes or bhsters in the coating and/or warp of the sheet (15). 

Microdenier nylon and polyester were a significant spinning breakthrough when demonstrated in 1985. The finer-than-silk fibers added a new dimension to fabric aesthetics, comfort, and performance. Microdenier nylons are used in weaving, warp knits, and weft knits for sports-, leisure-, and... 

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