Sample-up-the-ramp

Figure 7.8 Sampling methods to reduce or eliminate noise in the output, (a) Correlated double sampling (CDS), (b) Fowler sampling, (c) Sampling up the ramp.

The total amount of HjS released per 0.10 g of sulfated sample during the soak-ramp (up to 800°C) mode test, i.e., the integrated area up to 800°C under each plot in Figure 1, is included in Table 2. Because each sample was 3h sulfated and all thrre steps (1 - 3) are reflected in these data, it is not surprising to see that the results do not parallel with the ranking based on TGA data (also included in Table 2) which cover a 15-min period of the steps 1 and 2 combined. Nevertheless, we found these data quite useful especially when TGA data for steps 1 and 2 were not immediately available. 

The feedback controller is continuous, and it sees a constant error between samples. Therefore the manipulated variable m, is ramped up or down during the sampling period by the integral action, as sketched in Fig. 18.12u. 

Either by further increasing the bias voltage or by reducing the tip-sample distance, carefully ramp up the field-emission current. 

From the curve estimate the glass transition temperature, Tg, the melting temperature, Tm, the crystallization temperature, Tc and the heat of fusion, A, for this specific PET sample during the temperature ramp-up. If the heat of fusion for a hypothetically 100% crystalline PET sample is 137 kJ/kg [64], what was the degree of crystallinity in the PET bottle screw-top ... 

Experimental Methods.— The initial fleeting excursions from frequency domain into time domain (for example, ref. S) appear to have been made because, at that time, steady-state measurements at very low frequencies ( 10 Hz) were unsatisfactory. Step-up, step-down, and ramp voltages were variously applied to capacitors containing dielectric samples, and the tranaent current i(/), or charge q t), responses monitored over a wide range of times such approaches have been reviewed. Although it is now quite feasible to make steady-state measurements at very low frequencies. 

The first of the separation techniques to be used in process measurement was gas chromatography (GC) in 1954. The GC has always been a robust instrument and this aided its transfer to the process environment. The differences between laboratory GC and process GC instruments are important. With process GC, the sample is transferred directly from the process stream to the instrument. Instead of an inlet septum, process GC has a valve, which is critical for repetitively and reproducibly transferring a precise volume of sample into the volatiliser and thence into the carrier gas. This valve is also used to intermittently introduce a reference sample for calibration purposes. Instead of one column and a temperature ramp, the set up involves many columns under isothermal conditions. The more usual column types are open tubular, as these are efficient and analysis is more rapid than with packed columns. A pre-column is often used to trap unwanted contaminants, e.g. water, and it is backflushed while the rest of the sample is sent on to the analysis column. The universal detector - thermal conductivity detector (TCD)-is most often used in process GC but also popular are the FID, PID, ECD, FPD and of course MS. Process GC is used extensively in the petroleum industry, in environmental analysis of air and water samples" and in the chemical industry with the incorporation of sample extraction or preparation on-line. It is also applied for on-line monitoring of volatile products during fermentation processes" ... 

A desorption peak at a selected temperature ramping rate. The exit stream concentration goes up as desorption starts at some point along the ramp, reaches a maximum, and then declines as the adsorbent is depleted on the sample. 

In the laboratory, the vial containing the swab was opened and the filter paper inserted into the liner of the cooled injector port (45°C) of a gas chromatograph (GC Hewlett Packard 5890 Series II) coupled to a mass spectrometer (MS Hewlett Packard 5971A) and fitted with a silica capillary column (J W, model DB5-HT, no. 122-5731, 30 m long x 0.25 mm ID x 0.1 pm film thickness). The sample was cryofocused onto the front of the GC column by maintaining the column at low temperature (2 C), and ramping up the injector to 150 C at 27 C/min. 

Ramped DSC experiments were carried out on samples taken after the first heat-up phase, at the end of the Dewar experiment, and at the end of the isothermal heat flow calorimetry experiment. Similar results were obtained in all cases — that is, a strong exothermic peak with a heat release of around 1140 J and an onset temperature of around 160°C. It can be seen that the shape of the curves obtained (Figure A2.5) as well as the heat released and onset temperature are nearly identical to that obtained from the DSC experiment on the mixture of reactants (Figure A2.2, page 198). Thus the exothermic peak from the mixture of reactants is not due to the process reaction, as originally postulated, but is caused by the decomposition of the reaction product. This was further confirmed when a DSC experiment was eventually carried out on a sample of the product taken during pilot plant manufacture. 

The nanotribological properties of PLL-g-dex copolymers were characterized by the acquisition of friction-vs-load plots in a number of areas on each sample. Briefly, the sample was laterally scaimed relative to a fixed tip-cantilever assembly posilion in a line-scan mode while the sample was simullaneously ramped up and Ihen ramped down in vertical direction to provide a variation in normal load. Both normal and lateral defiection of the tip—cantilever assembly generated from the interaction between the probe tip and the sample surface were detected by a four-quadrant photodiode and interpreted as the normal load (converted based on the manufacturers normal spring constant value, = 0.58 N m ) and the frictional forces (raw photodiode signals), respectively. With the fiictionforces plotted as a function of normal load, friction-vs-load plots were obtained. To ensure a valid comparison of the frictional properties... 

Figure 2.44. Schematic representation of the baseline method. Area A is the energy accounted for in the return to steady state, while areas B and C represent the energy necessary for melting the sample. AT = difference of reference temperature T minus the lagging sample temperature Ts.The subscripts i and f indicate initial and final, while q represents the ramp rate and t is time. Endotherm is up. [From Wunderlich (1990) reprinted with permission of B. Wunderlich and Elsevier].

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