Unipolarity

We first examine how this works for the case of coherent flow. A typical pulse sequence is shown in figure Bl.14.9. This sequence creates a spin echo using two unipolar gradient pulses on either side of a 180° pulse. The duration of each gradient pulse of strength G, is . The centres of the gradient pulses are separated by A. 

In an HBT the charge carriers from an emitter layer are transported across a thin base layer and coUected by a third layer called the coUector. A small base current is present which iacludes the carriers that did not successfully cross the base layer from the emitter to the coUector. The FET is a unipolar device making use of a single charge carrier in each device, either electrons or holes. The HBT is a bipolar device, using both electrons and holes in each device. The emitter and coUector layers are doped the same polarity n- or -type), with the base being the opposite polarity (p- or n-ty- e). An HBT with a n-ty e emitter is referred to as a n—p—n device ap—n—p device has a -type emitter. The n—p—n transistors are typicaUy faster and have been the focus of more research. For the sake of simplicity, the foUowing discussion wiU focus on n—p—n transistors. 

The bipolar membranes are used in a more or less conventional ED stack together with conventional unipolar membranes. Such a stack has many acid—alkah producing membranes between a single pair of end electrodes. The advantages of the process compared to direct electrolysis seem to be that because only end electrodes are required, the cost of the electrodes used in direct electrolysis is avoided, and the energy consumption at such electrodes is also avoided. 

High level. Where the source is a process transmitter, the range resistor in the current loop converts the 4-20 milliamp signal into a 1-5 volt signal. The conversion equipment can be unipolar (i.e., capable of processing only positive voltages). 

On the output side, dedicated digital-to-analog converters are provided for each analog output. Outputs are normally unipolar, and require a lower resolution than inputs. A 10-bit resolution is normally sufficient, giving a resolution of 1 part in 1000 or 0.1%. 

Electrical mobility is utilized to obtain size distribution information in the 0.01-1.0 /xm diameter range. This measurement method requires unipolar... 

Output power Bipolar or unipolar flux Input voltage Number of windings Winding configuration... 

An air-gap is required for all unipolar flux drive applieations sueh as this. One method of aehieving this is shown in Equation 3.28a (CGS system (U.S.)). 

Using one of the core materials listed in Table D-1, the designer can feel reasonably confident that he or she has made the best choice for a ferrite. Mopermalloy is a ferrite alloy that has nonmagnetic molybdenum mixed with it. The molybdenum acts as a distributed air-gap within the material, which makes the material excellent for dc biased or unipolar applications. Unfortunately, it is only available in toroid core styles, and it typically used for output filter chokes. 

The traditional unipolar diffusion charging model is based on the kinetic theory of gases i.e., ions are assumed to behave as an ideal gas, the properties of which can described by the kinetic gas theory. According to this theory, the particle-charging rate is a function of the square of the particle size dp, particle charge numbers and mean thermal velocity of tons c,. The relationship between particle charge and time according White s... 

Currem field characteristics measured wiih conjugated polymers sandwiched between an indium-tin oxide (ITO) anode and an aluminum cathode are usually hole dominated and are, consequently, appropriate for testing injection/lransport models for the case of unipolar current How. Data shown in Figure 12-1 refer to injection-limited currents recorded on typically 100 nm thick spin-coated films of derivatives of poly(y d/"fi-phenylenevinylene) (PPV) and a planarized poly(/ /" -pheny-leue) employing a Keilhley source measure unit. The polymers were ... 

Studies of health economics in the UK and the USA in unipolar depressive illness show... 

AU these features—low values of a, a strong temperature dependence, and the effect of impurities—are reminiscent of the behavior of p- and n-type semiconductors. By analogy, we can consider these compounds as ionic semiconductors with intrinsic or impurity-type conduction. As a rule (although not always), ionic semiconductors have unipolar conduction, due to ions of one sign. Thus, in compounds AgBr, PbCl2, and others, the cation transport number is close to unity. In the mixed oxide ZrOj-nYjOj, pure 0 anion conduction t = 1) is observed. 

Because of the high values of conductivity which in individual cases are found at room temperature, such compounds are often called superionic conductors or ionic superconductors but these designations are unfounded, and a more correct designation is solid ionic conductors. Strictly unipolar conduction is typical for all solid ionic conductors in the silver double salts, conduction is due to silver ion migration, whereas in the sodium polyaluminates, conduction is due to sodium ion migration. 

Fig. 31.3. (a,b) Reproduction of distances D and angular distances 0 in a score plot (a = 1) or loading plot (p = 1) in the common factor-space (c,d) Unipolar axis through the representation of a row or column and through the origin 0 of space. Reproduction of the data X is obtained by perpendicular projection of the column- or row-pattern upon the unipolar axis (a + P = 1). (e,0 Bipolar axis through the representation of two rows or two columns. Reproduction of differences (contrasts) in the data X is obtained by perpendicular projection of the column- or row-pattern upon the bipolar axis (a + P = 1). 

Figure 31.4 shows the biplot of the trace elements and wind directions for the case when a = p = 0.5. Since here we have that a + P equals 1, we can reconstruct the values in the columns of the data table X by means of perpendicular projections upon unipolar axes. In Fig. 31.4a we have drawn a unipolar axis through Cl. Perpendicular projection of the four wind directions upon this axis reconstructs the order of the concentrations of Cl at the four wind directions as listed in Table 31.1. Now we have established a way which leads back from the graphic display to the tabulated data. This interpretation of the biplot emphasizes the one-to-one relationship between the data and the plot. Such a relationship is also inherent in the ordinary bivariate (or Cartesian) diagram. 

Fig. 31.4. (a) Biplot in which the concentrations of an atmospheric trace element (Cl) are reconstructed by perpendicular projection upon a unipolar axis, (b) Biplot in which the differences (contrasts) between two atmospheric trace elements (Cl, Si) are reproduced by perpendicular projection upon a bipolar axis. 

Fig. 31.6. Biplot of chromatographic retention times in Table 31.2, after column-centering of the data. Two unipolar axes and one bipolar axis have been drawn through the representations of the methods DMSO and methylenedichloride (CH2CI2). The projections of three selected compounds are indicated by dashed lines. TTie values read off from the unipolar axes reproduce the retention times in the corresponding columns. The values on the bipolar axis reproduce the differences between retention times.

There are two outstanding poles on this biplot. DMSO and dimethylchloride are at a large distance from the origin and from one another. These poles are the most likely candidates for the construction of unipolar axes. As has been explained in the previous section, perpendicular projections of points (representing compounds) upon a unipolar axis (representing a method) leads to a reproduction of the data in Table 31.3. In this case we have to substitute the untransformed value in eq. (31.35) by Zy of eq. (31.42) ... 

Since m, is a constant for the given unipolar axis through the Jth method, we obtain that the projections on this axis are equal to Xy minus a constant. 

The unipolar axis through the origin and DMSO reproduces rather well the data in the corresponding column of Table 31.2. By perpendicular projection of the... 

Finally, we have constmcted a bipolar axis through DMSO and methylenedichloride. By perpendicular projection of the centers of the circles upon this bipolar axis we obtain the differences in retention times obtained respectively with DMSO and with methylenedichloride. Using a similar reasoning as developed above for unipolar axes we can perform a substitution of eq. (31.42) in eq. (31.38) which leads to ... 

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