Headings parallelism

In the third (and last) move of the Experimental Approach section, you describe how you will conduct your proposed work. A well-organized and logical progression of ideas is essential in this move. Most authors demark the start of this move with a level 2 heading, parallel to the level 2 headings used for moves 1 and 2. A few examples are shown in table 13.6. 

When you start walking, be conscious of your posture. Keep your shoulders, back, and spine straight with weight centered over the hips. Keep your head parallel to the ground. By taking smooth, easy steps, your body will move fluidly through the walking motion. 

Measurements of sound velocity at ultrasonic frequencies are usually made by an acoustic interferometer. An example of this apparatus11 is shown in Fig. 2. An optically flat piezo-quartz crystal is set into oscillation by an appropriate electrical circuit, which is coupled to an accurate means of measuring electrical power consumption. A reflector, consisting of a bronze piston with an optically flat head parallel to the oscillating face of the quartz, is moved slowly towards or away from the quartz by a micrometer screw. The electrical power consumption shows successive fluctuations as the distance between quartz and reflector varies between positions of resonance and non-resonance of the gas column. Measurement of the distance between resonance positions gives a value for A/2, and if /... 

In this extensive study of thiourea synthesis by coupling isothiocyanates with amines under mechanochemical conditions of neat and LAG, a total of 49 different thiourea derivatives were prepared. Since the supramolecular chemistry of simple synunetrical and nonsymmetrical diarylthiouieas had not previously been studied in detail, the information from the PXRD patterns of the milling products in this work also allowed for a systematic analysis of structural features of diarylthio-ureas. The three main self-assembly motifs were identified. A characteristic supramolecular synthon based on bifurcated N—H - S hydrogen bonds was found in most cases, whereby the individual thiourea molecules were assembled into chains aligned in a head-to-head (parallel molecular dipoles) or head-to-tail (antiparallel molecular dipoles) manner. In the case of slerically hindered thioureas, such as A -(2,6-dimethylphenyl)-A -phenylthiourea, the third motif arising from discrete cen-trosymmetric dimers based on rI(S) supramolecular synthon was found. A detailed look at the measured PXRD patterns for aU diarylthioureas revealed that solid-state structures of these compounds could be classified into two structural families, denoted as family I and family II (Fig. 1.11). 

Ti,0g = 0, is the most repulsive. A head-to-tail, parallel arrangement, 0 = 0g = is attractive but less... 

The cell head is fabricated from a 2.54-cm steel plate and has separate compartments for fluorine and hydrogen. The oudet-gas manifolds, hydrogen fluoride feed and purge lines, and electrical connections are on top of the head. The gas separation skirt is made of Monel. An insulating gasket maintains the seal between the tank and the head. The anode assembly consists of 32 carbon blades bolted onto a copper bar, each of which contains three copper conductor posts. The cathode assembly consists of three vertical, 0.6-cm parallel steep plates. The plates surround the anode assembly and are supported by three steel posts which also serve as conductors. 

Horizontal pre.s.sure leaf filters. In these filters the leaves may be rectangular leaves which run parallel to the axis and are of varying sizes since they form chords of the shell or they may be circular or square elements parallel to the head of the shell, and aU of the same dimension. The leaves may be supported in the sheU from an independent rack, individuaUy from the shell, or from a filtrate manifold. Horizontal filters are particiilarly suited to diy-cake discharge. 

Third, you would. suppose that parallel pumps are identical, that they were manufactured and assembled together. But it is possible that one pump of the pair is the dominant pump and the other is the runt pump. If you start the dominant pump first in the parallel system, and then decide to add the runt pump of the pair, the weaker pump may not be able to open the check valve. The pump operator perceives that the flow meter on the second pump is stuck or broken. This is because the second pump might be dead heading against a closed check valve, maintained that w ay by the dominant pump. If this situation exists, it may re.sult in premature failure of bearings and. seals, leading maintenance and operations personnel thinking that parallel pumps are problematic. 

The solution is Identify the dominant and weak pump should they exist. To do this, take pressure gauge readings with the pumps running at shut-off head. Verify that the impellers are the same diameter, and that the wear bands and motor speeds are equal. If you can identify one pump in the pair as dominant, ahvays start the weak pump first and then add the dominant pump in parallel with the weaker. The dominant pump coming on stream w ill push open the check valve. It may be necessary to override a sequential starter. 

In this diagram the key features are A - Diffusion baffle this serves four roles. First to dissipate the velocity head, thereby improving the overall hydraulic characteristics of the separator. Next, to direct incoming flow downward and outward maximizing the use of the separator volume. Third, to reduce flow turbulence and to distribute the flow evenly over the separator s cross-sectional area. Finally, to isolate inlet turbulence from the rest of the separator. B- Internal chambers In the sediment chamber, heavy solids settle out, and concentrated slugs of oil rise to the surface. As the oily water passes through the parallel corrugated... 

Shell-and-tube exchangers contain several types of baffles to help direct the flow of both tube-side and shelbside fluids. Pass partition baffles force the fluid to flow through several groups of parallel tubes. Each of these groups of tubes is called a pass, . since it passes the fluid from one head to another. By adding pass partition baffles on each end. the tube-side fluid can be forced to take as many passe.s through the exchanger as desired. 

When comparable amounts of oil and water are mixed with surfactant a bicontinuous, isotropic phase is formed [6]. This bicontinuous phase, called a microemulsion, can coexist with oil- and water-rich phases [7,1]. The range of order in microemulsions is comparable to the typical length of the structure (domain size). When the strength of the surfactant (a length of the hydrocarbon chain, or a size of the polar head) and/or its concentration are large enough, the microemulsion undergoes a transition to ordered phases. One of them is the lamellar phase with a periodic stack of internal surfaces parallel to each other. In binary water-surfactant mixtures, or in... 

FIGURE 10.41 (a) Gramicidin forms a double helix in organic solvents a helical dimer is the preferred strnctnre in lipid bilayers. The strnctnre is a head-to-head, left-handed helix, with the carboxy-termini of the two monomers at the ends of the strnctnre. (b) The hydrogen-bonding pattern resembles that of a parallel /3-sheet. 

Berliner, E., Young, E., Anderson, K., et al., 1995. Failure of a. single-headed kine.sin to track parallel to microtubule protofilaments. Nature 373 718-721. 

Pumps are operated in parallel to divide the load between two (or more) smaller pumps rather than a single large one, or to provide additional capacity in a system on short nodce, or for many other related reasons. Figure 3-35 illustrates the operational curve of two identical pumps in parallel, each pump handling one half the capacity at the system head conditions. In the parallel arrangement of two or more pumps of the same or different characteristic curves, the capacities of each pump are added, at the head of the system, to obtain the delivery flow of the pump system. Each pump does not have to carry the same How but it will operate on its own characteristic curve, and must deliver the required head. At a common tie point on the discharge of all the pumps, the head will be the same for each pump, regardless of its flow. 

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