Accordion effect

A common problem with many continuous furnaces is an accordion effect that occurs after line stoppages. Continuous furnaces are wonderful as long as they maintain steady-state operation. To envision the accordian effect, think of the changes with passage of time of the temperature pattern throughout the length of a fumaoe with temperature sensors located at the traditional positions near the ceiling of the furnace and near the load-exit-end of each zone. 

The so-called accordion effect upsets the supposedly steady pattern of temperature progression as load pieces move through the zones of multizone reheat furnaces, whether rotary, pusher, walking beam, or walking hearth. (See chap. 6.)... 

Ribs do not always stiffen. Blow-molded ribs often increase surface area and reduce wall thickness, creating a flexible-bellow or accordion effect. Flexing may affect hinge points. Proper design prevents this. 

Later, the uses for transparent sheet included rules and set-squares for geometrical drawing, while pearlescent materials were highly effective for show purposes—as in drum kits for dance bands, accordions, and other musical instruments. Some pearl finishes were produced much as veneers, for embellishing small items like the handles of pen-knives. 

A 2002 review by Reynolds and Enriquez describes the most effective pulse sequences for natural product structure elucidation.86 For natural product chemists, the review recommends HSQC over HMQC, T-ROESY (transverse rotating-frame Overhauser enhancement) in place of NOESY (nuclear Over-hauser enhancement spectroscopy) and CIGAR (constant time inverse-detected gradient accordion rescaled) or constant time HMBC over HMBC. HSQC spectra provide better line shapes than HMQC spectra, but are more demanding on spectrometer hardware. The T-ROESY or transverse ROESY provides better signal to noise for most small molecules compared with a NOESY and limits scalar coupling artefacts. In small-molecule NMR at natural abundance, the 2D HMBC or variants experiment stands out as one of the key NMR experiments for structure elucidation. HMBC spectra provide correlations over multiple bonds and, while this is desirable, it poses the problem of distinguishing between two- and three-bond correlations. 

In a 2D experiments a series of FIDs are acquired using an incremented delay tl to build up a 2D data matrix, each row of the matrix corresponding to a specific value of tl. The effect of the incremented delay is to modulate the FIDs from the experiments, which can be interpreted and analysed as a pseudo FID with respect to the time delay tl. By convention the incremented delay is called dO and the increment inO. The detected frequency range in the fl dimension is given by ASW [Hz] = l/(inO ndO ). Normally there is only one time increment variable but in special pulse sequences based upon for instance the ACCORDION-principle, see section 5.9.3, additional increment variable ini, in2... can be defined. Usually for the first experiment dO = 3 us and for the second and subsequent experiments dO = 3u -i- inO (n -1). In a number of 2D experiments the... 

An accordion playing some popular air, first in air and then in, say, hydrogen, demonstrates still more clearly what would be the effect of an orchestra playing in such a gas—or even in a room where a cotmd rtMe quantity of tiiis gas was present. 

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