Principles of Operation

We consider the separation of a hypothetical two-component feed containing components A and B, with A being the more strongly adsorbed species. The desorbent (C) should have an adsorption affinity intermediate between that of A and B. The process splits the original mixture into two streams, one (the extract) containing A and C with very little B and the other (the raffinate) 

FIGURE 12.11, Schematic diagram showing the roles played by the four sections of a Sorbex countercurrent displacement desorption process. 

Zone 1. In this section the more strongly adsorbed species A) is adsorbed. The solid entering this zone contains mainly desorbent C with some of Component B which is displaced by the adsorption of A. The liquid at the top of this zone contains only B and C, and a portion of this liquid is removed as the raffinate product. 

Zone II. The solid entering this zone has just been in contact with the feed and therefore contains both components A and B as well as desorbent C. The weakly adsorbed B is stripped from the solid by the more strongly adsorbed A. The concentration of A reaches a maximum at some point within this zone and the concentration of B falls essentially to zero at the bottom of this zone. 

Zone 111. The solid leaving zone II still contains an appreciable concentration of A as well as C. A is desorbed in zone III by countercurrent contact with a pure desorbent stream which enters at the bottom of the column. The extract product containing A + C, with essentially no B, is removed between zones II and III. 

The TSI 3000 Series Desktop LIBS comes in a variety of configurations, including 4 Czerny-Turner spectrographs with CCD detectors, and has a wavelength range of 190-950 nm. PMT detectors can be used, especially with multiple PMTs, with the drawback being that the wavelengths that can be monitored are fixed and limited to the number of detectors. 

The spectra are processed by computer software that now often includes advanced chemomet-ric methods (see the discussion of chemometrics in Section 4.7.2.1). Methods such as partial least squares (PLS) and principal component analysis are used by instrument software to construct calibration curves and provide quantitative analysis. LIBS software on many commercial systems supports library matching, sample classification, qualitative, semiquantitative and quantitative analysis including preloaded libraries and calibrations, and customer-built libraries and calibrations. 

A low-pressure Ar purge of the sample surface is used to prevent particulates from the laser ablation of the sample from dirtying the system optics, to generate a stronger emission signal and to displace air from the LIBS spark to enable the determination of N and O from samples. 

Instruments can be run as open-beam systems by focusing the laser onto a sample that is not in an enclosure, or as benchtop enclosed systems, and as standoff systems where the laser propagates through the atmosphere over significant distances and the emission is collected by a telescope. 

Fi ure 14-7. A MISFET in operation, (a) Vj=0 an -type channel of constant thickness 

Brief description and principles of operation of electrochemical components 

Generally speaking, an electrochemical component can operate as an electric generator or an electric load, or both if it has reversible function. 

The electrodes need to be good electrical conductors. The electrolyte has to be a good ion conductor and a good electron insulator, in order to avoid any short-circuits between the two electrodes. In the case of a liquid electrolyte, a separator is usually used to electrically insulate the two electrodes. The reactions consume reactants and form products, which have to be respectively brought to and evacuated from the reaction area. 

Finally, the phenomena described above are accompanied by heat exchanges the performances and lifetimes of the components are very sensitive to temperature. Hence, thermal aspects are of cracial importance for their implementation in electrical systems. 

There is a wide variety of electrochemical components for the production and storage of electricity [TUR 08], some of which will be the subject of a more in-depth description later on in this book. Amongst other things, it is possible to distinguish the following families of electrochemical components  

Electrons and holes generated in the i-layer by incident light are driven to the n- and p-layer by the internal electric field, respectively. The material quality of the intrinsic layer and the strength and distribution of the electric field are responsible for the charge carrier collection and mainly determine the electrical solar cell performance. Defects affect the charge carrier collection in two different ways On the one hand they act as recombination centers, and on the other hand their charge state modifies the electric field distribution in the i-layer. 

The more rectangular the. //E-curve appears, the higher the FF is and the better charge carriers are collected within the device. Finally, the conversion efficiency is defined as the ratio between electrical power density delivered by the solar cell under standard illumination conditions and the power density of the incident light Pnght 

The efficiency r is the most important parameter as it defines the overall quality of the device. 

The terms electrochemically and assisted are used in these process names because additional voltage must be added to the circuit. In an MFC an anode potential can approach the theoretical limit of E = -0.3 V of the substrate (e.g., acetate. Table 3.1, 298 K, pH = 7). With oxygen, the cathode potential in an MFC is -0.2 V (vs. NHE), achieving an overall a cell voltage approaching -0.5 V [0.2 V - (-0.3 V) = 0.5 V). If we wish to form hydrogen at the cathode, however, we must remove the oxygen and overcome a cathode potential at pH = 7 and 298 C of 

Therefore, the calculated cell voltage for a system that could produce hydrogen at the cathode is 

Microbial Fuel Cells. By Bnice E. Logan Copyright 2008 John Wiley Sons, Inc. 

The voltage needed to achieve H2 gas production in a MEC can be applied using an MFC or any power source. If higher potentials could be obtained at the anode with 

The first system reported for H2 evolution was developed by Liu et al. (2005c) using a two-bottle (310 mL each) reactor, with the chambers filled to 200 mL and separated by a small cation exchange membrane (CEM Nafion) held in a tube between the reactors 

In a lithium-metal polymer battery, the eleetrochemical chain involved is  

The reaction principle behind the operation of a Li-metal battery is given below  

2 LiTFSI is the abbreviation for LiN(S02CF3)2 (hthium bis(trifluoromethanesulfonyl)imide). It corrodes the aluminum of the current collectors with a voltage higher than 4.2 V. However, as PEO requires the voltage to be limited to 4 V, we can use LiTFSI with no danger of degradation of the element. 

The negative electrode comprises a foil of metal lithium, which also serves as a current collector. Between this strip and the outer terminal, it is necessary to use a copper current retriever on the edge of the roll or the stack. 

The electrolyte is a poly(ethylene oxide) (PEO) film with a dissolved hthium salt LiTFSI. In order to obtain a sufficiently good ionic conductivity, we need to operate the battery at a temperature greater than the glass transition temperature of the polymer. The operating temperature required is 60-80°C, which limits the field of application to large batteries, which notably precludes the mobile market. Under no circumstances must the thermal degradation temperature of the PEO, which is around 120 C, be surpassed. 

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The principle of operation of the hydraulic reciprocating pump is similar to the beam pump, with a piston-like sub-surface pump action. The energy to drive the pump, however, is delivered through a hydraulic medium, the power fluid, commonly oil or water. The power fluid drives a downhole hydraulic motor which in turn drives the pump. A separate surface pump delivers the hydraulic power. The power fluid system can be of the closed loop or of the open type. In the latter case, the power fluids are mixed with the produced fluid stream. The performance of the hydraulic pump is primarily monitored by measuring the discharge pressures of both surface and sub-surface pumps. 

The Scania plant at Falun in Sweden manufaetures bus and truck steering knuckles. These are safety-critical components that are specified as having to be crack-free. For this reason, every component is now inspected using an automatic process that ensures the appropiate inspection is consistently canied out to the required standards of quality. Photos of the system are shown in Fig 1. The principle of operation is as follows. 

In this work, a microwave interferometric method and apparatus for vibration measurements is described. The principle of operation is based on measurement of the phase of reflected electromagnetic wave changing due to vibration. The most important features of the method are as follows simultaneous measurement of tlie magnitude and frequency of the rotating object high measurement accuracy weak influence of the roll diameter, shape and distance to the object under test. Besides, tlie reflecting surface can be either metallic or non-metallic. Some technical characteristics are given. 

Acoustic foremnners appear as ground vibrations in the range from 0,1 to 50 Hz with the amplitudes from 10 to 10 m (dynamic range is 160 dB). To control these parameters a large number of earthquake-shock recorders based on different principle of operation are manufactured... 

The principles of operation of quadnipole mass spectrometers were first described in the late 1950s by Wolfgang Paul who shared the 1989 Nobel Prize in Physics for this development. The equations governing the motion of an ion in a quadnipole field are quite complex and it is not the scope of the present article to provide the reader with a complete treatment. Rather, the basic principles of operation will be described, the reader being referred to several excellent sources for more complete infonnation [13, H and 15]. 

Figure Bl.19.1. Principle of operation of a scanning tiimrelling microscope. The x- andj -piezodrives scan the tip across the surface. In one possible mode of operation, the current from the tip is fed into a feedback loop that controls the voltage to die z-piezo, to maintam constant current. The Ime labelled z-displacement shows the tip reacting both to morphological and chemical (i.e. electronic) inliomogeneities. (Taken from [213].)...

Calorimetry is the basic experimental method employed in thennochemistry and thennal physics which enables the measurement of the difference in the energy U or enthalpy //of a system as a result of some process being done on the system. The instrument that is used to measure this energy or enthalpy difference (At/ or AH) is called a calorimeter. In the first section the relationships between the thennodynamic fiinctions and calorunetry are established. The second section gives a general classification of calorimeters in tenns of the principle of operation. The third section describes selected calorimeters used to measure thennodynamic properties such as heat capacity, enthalpies of phase change, reaction, solution and adsorption. 

B1.27.4.1 CLASSIFICATION BY PRINCIPLE OF OPERATION ISOTHERMAL CALORIMETERS (MORE PRECISELY, QUASI-ISOTHERMAL)... 

A liquid serves as the calorimetric medium in which the reaction vessel is placed and facilitates the transfer of energy from the reaction. The liquid is part of the calorimeter (vessel) proper. The vessel may be isolated from the jacket (isoperibole or adiabatic), or may be in good themial contact (lieat-flow type) depending upon the principle of operation used in the calorimeter design. 

Figure C2.2.14. Principle of operation of a polymer-dispersed liquid crystal display. The contours of the liquid...

A scintillator, sometimes known as the Daly detector, is an ion collector that is especially useful for studies on metastable ions. The principle of operation is illustrated in Figure 28.4. As with the first dynode of an electron multiplier, the arrival of a fast ion causes electrons to be emitted, and they are accelerated toward a second dynode. In this case, the dynode consists of a substance (a scintillator) that emits photons (light). The emitted light is detected by a commercial photon... 

There are many types of scales using many different principles of operation. There are, however, three distinct elements which can be identified regardless of the principle of operation (Fig. 2). 

Blast Furnace. The blast furnace is the predominant method for making iron. Estabhshed for centuries as the premier ironmaking process, blast furnace ironmaking both enabled and profited from the Industrial Revolution. Although the fundamental principles of operation are unchanged, the blast furnace has evolved into a highly efficient and productive process. 

Principle of Operation. Electrical current flows are induced in all conductors when exposed to an a-c field. These currents generate a magnetic field surrounding the conductors which oppose the field being produced by the a-c field with a force sufficient to repel the conductor. Eigure 16 illustrates this principle by showing a rotor consisting of many poles. 

Tritium is readily detectable because of its radioactivity. Under certain conditions concentrations as low as 370 )-lBq/mL (10 //Ci/mL) can be detected. Most detection devices and many analytical techniques exploit the ioni2ing effect of the tritium P-decay as a principle of operation (62,63). 

Scrubber Ttfpes and Performance The diversity of particulate scrubber designs is so great as to defy any detailed and selhconsistent system of classification based on configuration or principle of operation. However, it is convenient to cliaracterize scrubbers loosely according to prominent constructional features, even though the modes of operation of different devices in a group may vary widely. 

Air Filters The types of equipment previously described are intended primarily for the collection of process dusts, whereas air filters comprise a variety of filtration devices designed for the collec tion of particulate matter at low concentrations, usually atmospheric dust. The difference in the two categories of equipment is not in the principles of operation but in the adaptations required to deal with the dif-... 

Principle of Operation Spiral concentration of ores and industrial materials is based primarily on the specific-gravity differentials of the materials to be separated. The shape facdor of the feed material is also important, and utilization of reagentized feed can change the apparent specific gravity of component minerals by forced attachment of air bubbles to mineral floes. The best known spiral-type concentrator is the Humphreys spiral concentrator, which first proved its commercial feasibihty in 1943. In that year an Oregon plant successfully... 

The principle of operation of batch-type scales is based on the concept that a flowing stream of material has constant density. If this is true, then if at some point in advance of the desired batch weight the stream is cut off, the amount of material flowing will remain con-... 

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