Sawtooth profile

Quantifying the effect of surface roughness or morphology is difficult, however. Surface preparations that provide different degrees of surface roughness also usually produce surfaces that have different oxide thicknesses and mechanical properties, different compositions, or different contaminant levels. The problem of separation of these variables was circumvented in a recent study [52] by using a modified microtome as a micro milling machine to produce repeatable, well-characterized micron-sized patterns on clad 2024-T3 aluminum adherends. Fig. 2 shows the sawtooth profile created by this process. 

A graphoepitaxy method has been developed in which a topographic top-down defined pattern on a substrate is used to direct the epitaxial growth in an overlaying block copolymer bottom-up nanostructure by creating a periodic thickness profile (Fig. 5). Fasolka and coworkers [66] employed a faceted silicon substrate, which has sawtooth-profile corrugations in the nanometer... 

As a result, the wavelength X in units of X0 exhibits a sawtooth -profile as function of the film thickness (Figs. 15,32) for a parallel arrangement of the lamellae between symmetric walls (Fig. 3a, Fig. 26b,d, Fig. 27b,d) the domains are compressed or expanded to enforce the condition D=nIUn the whole range from... 

Most modern processes are low pressure processes. Plant capacities range from 150-3000 tons/day. The plants differ mainly in reactor design and, interrelated with this, in the way the heat produced by the reaction is removed. In the ICI process an adiabatic reactor is used with a single catalyst bed. The reaction is quenched by adding cold reactant gas at different heights in the catalyst bed. The temperature profile in the bed has a sawtooth profile. A flow scheme of the ICI process is given in Fig. 2.20. 

Linear profiles are the simplest profiles to use for powder compressions. Typically, a sawtooth or v-shaped profile is used where the punch is extended at a constant velocity and retracts at a constant velocity. In theory, during a sawtooth profile, the punch reverses its motion instantaneously between the compression and a decompression strokes. At low speeds (e.g.. <1 mm/sec), the hydraulic response system can easily accommodate this discontinuity. However, at high speeds (>100mm/.sec), the control system may show a small lag in the position-time waveform (<10 milliseconds) as it attempts to rapidly reverse the direction of punch. The sawtooth waveform is commonly used for more fundamental compression studies (e.g.. Heckel analysis), where the desired powder volume reduction is proportional to time. It is also u.seful when evaluating instrument performance during factory acceptance testing. 

The sawtooth waveform can be augmented to create a trapezoidal profile. Like the sawtooth profile, the trapezoidal profile uses constant compression and decompression rates. However, between the compression and decompression segments an intentional dwell time is incorporated. The dwell time is often defined as the time that the moving punches remain stationary at their furthest point of travel. This type of profile is useful when studying either the effects of compression rate or dwell time on powder compression behavior. 

Figure 11 Quasi-isothermal crystallization of polyamide 12 at 7 o=173°C, fp = 600s, ytr=0-5K. (a) Temperature profile consisting of an asymmetric sawtooth profile. The resulting heating rate and the heat flow rate show sharp spikes containing a broad spectrum of higher harmonics. (b) Specific reversing heat capacity as a function of time for different frequencies as indicated in the graph. The lines labeled Cp and Cp c indicate the data for liquid and crystalline polyamide 12 at 173 °C available from the ATHAS-DB, respectively. The used temperature time profile for sample preparation and crystallization is shown in the inset. Reproduced with permission from Schick, C. Anal. Bioanal. Chem. 2009, 395,1589-1611. ...

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