Basic Principles and Operation

In this section, a description of the SOFC is given in terms of its basic principles and operation, different design configurations, components and materials. 

Since water is formed at the anode side where hydrogen is supplied as the reactant, the issue of mass transfer loss as a result of water flooding at the anode is relatively low and less critical in SOFC due the higher dif-fusivity of hydrogen in water. A major characteristic of SOFC is that the oxygen reduction kinetics in the cathode side is relatively fast and results in a lower activation voltage loss, and hence does not require any noble metals as catalyst. 

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Investigators working in the field of digital microfluidics have conducted extensive research on the basic principles and operations underlying the implementation of electrowetting-based microfluidic systems. The result is a substantial microfluidic toolkit of automated droplet operations, a sizable... 

SPR is a representative physical phenomenon that is widely utilized for label-free characterization of molecules on thin metal films. The basic principle and operation of SPR has been described in more detail in several review articles [77, 78]. The reports on SPR-based immune sensors have steeply increased for detection of analytes with low molecular weights in recent years. SPR detection in microfluidic systems can provide various advantages. Immunoreactions are completed within a short time due to small sample volumes down to the nanolitre scale. Kim et al. developed a simple and versatile miniaturized SPR immunosensor enabling parallel analyses of multiple analytes [79]. Their SPR sensor was claimed to exhibit good stability and reusability for 40 cycles and more than 35 days. Feltis et al. demonstrated a low-cost handheld SPR-based immunosensor for the toxin Ricin [80]. Springer et al. reported a dispersion-free microfluidic system with a four-channel SPR sensor platform, which considerably improved the response time and sensitivity [81]. The sensor was able to detect short sequences of nucleic acids down to a femtomole level for 4 min. Waswa et al. demonstrated the immunological detection of E. coli 0157 H7 in milk, apple juice, and meat juice extracted from... 

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]. 

Basic Principles of Operation RO and NF are pressure-driven processes where the solvent is forced through the membrane by pressure, and the undesired coproducts frequently pass through the membrane by diffusion. The major processes are rate processes, and the relative rates of solvent and sohite passage determine the quality of the product. The general consensus is that the solution-diffusion mechanism describes the fundamental mechanism of RO membranes, but a minority disagrees. Fortunately, the equations presented below describe the obseiwed phenomena and predict experimental outcomes regardless of mechanism. 

In Section 13.2, we introduce the materials used in OLEDs. The most obvious classification of the organic materials used in OLEDs is small molecule versus polymer. This distinction relates more to the processing methods used than to the basic principles of operation of the final device. Small molecule materials are typically coated by thermal evaporation in vacuum, whereas polymers are usually spin-coated from solution. Vacuum evaporation lends itself to easy coaling of successive layers. With solution processing, one must consider the compatibility of each layer with the solvents used for coating subsequent layers. Increasingly, multilayered polymer devices arc being described in the literature and, naturally, hybrid devices with layers of both polymer and small molecule have been made. 

The pCOj electrode was first described in 1957 by Stow and later improved to its presently used form by Severinghaus The basic principle of operation relies on equilibration of COj with an aqueous solution. The change in pH in the aqueous solution associated with the equilibration due to carbonic acid formation (H2CO3) is measured and varies with log pCO2] It should be pointed out here that these measurements (and likewise for the pO electrode described below) give CO2 tension not concentration. To obtain concentration, Henry s Law of gas solubUity must be applied. However, for most medical and biological applications the knowledge of the gas tension is sufficient. 

Basic Principles of Operation Gas-separation literature often uses nomenclature derived from distillation, a practice that will generally be followed here. L is the molar feed rate, V is the molar permeate rate, R is the molar residue (L — V). Mole fractions of components i, j, in the feed-residue phase will be Xj, Xj. .. and in the permeate phase yi,yj.... Stage cut, 0, is permeate volume/feed volume, or V/L. 

The Malvern particle sizer is one of the most widely used, most effective, simple, and reliable methods commercially available for rapid measurements of ensemble characteristics of a spray. It is able to handle high droplet concentrations. It is easy to use and does not require comprehensive knowledge of its basic principles for operation. The primary advantage of the system is the speed of data acquisition and analysis. In addition, measurements of droplet size distributions can be made at any droplet velocities due to the fact that the diffraction patterns generated by droplets are independent of the... 

The first SRS unit was built as a demonstration plant and has been in operation since September 1997. The basic principle of operation is that a solution of sodium chloride and sodium sulphate in contact with a nanofiltration membrane at high pressure, will separate into a sulphate-lean permeate stream and a sulphate-rich concentrate stream. 

It must be made clear that WSL has only used olfactometers constructed on its own premises and calibrated by WSL staff one such instrument is the WSL Transportable model. (It is emphasised that this olfactometer is not the same as the commercially-available Portable model.) The WSL Transportable olfactometer and its operation have been described in detail previously (1) and only its main features need be reviewed here. From time to time, certain applications have required a special re-design of the olfactometer, e.g. to measure very weak odours, but the basic principles and the mode of operation have remained unchanged for some years. The main features of the standard WSL Transportable olfactometer are as follows ... 

Under the headline of instmmentation we shall mainly discuss the different types of mass analyzers in order to understand their basic principles of operation, their specific properties and their performance characteristics. Of course, this is only one aspect of instmmentation hence topics such as ion detection and vacuum generation will be addressed in brief. As a matter of fact, sample introduction is more closely related to particular ionization methods than to the type of mass analyzer employed, and therefore, this issue is treated in the corresponding chapters on ionization methods. The order of appearance of the mass analyzers in this chapter neither reflects the ever-changing percentage they are employed in mass spectrometry nor does it strictly follow a time line of their invention. Instead, it is attempted to follow a trail of easiest understanding. 

The scope of the use of mass spectrometry in the protein analysis has grown enormously in the past few decades. MS has become an important analytical tool in biological and biochemical research. Its speed, accuracy and sensitivity are unmatched by conventional analytical techniques. The variety of ionization methods permits the analysis of peptide or protein molecules from below 500 Da to as big as 300 Da (Biemann 1990 Lahm and Langen 2000). Basically, a mass spectrometer is an instrument that produces ions and separates them in the gas phase according to their mass-to-charge ratio (m/z). The basic principle of operation is to introduce sample to volatilization and ionization source, and then the molecular fragments from the ionization of the sample are detected by various kinds of detector and the data are analyzed with computer software. 

For all our purposes, a synthetic ion-selective membrane is nothing but a thin sheet of dense nonporous ion-exchanger. In fact, producing a sheet out of a conventional ion-exchanger was exactly the way in which ion-selective membranes were prepared a few decades ago this is the reason why they are still often called ion-exchange membranes. Yet, the basic principles of operation of a bulk ion-exchanger and of an ion-exchange membrane are... 

Anon, EngrgDesHndbk, Fuzes, Proximity, Electrical, Part Two (U) , DARCOM-P-706-212(S) (no date) [Discusses basic principles and design considerations for radio proximity fuzes operated in the VHF and UHF bands]... 

Notice that there is a feedback of information from the lower levels back up to the higher levels. The basic idea of feedback control occurs at the unit operation and fundamental control levels. Here, control algorithms are used to adjust manipulated inputs (controller outputs or control variables) to maintain process outputs (process variables) at desired values (known as setpoints). The basic principles and techniques of process control are pre-... 

The next four chapters discuss the basic principles underlying operation and method development of the most common electrodriven analytical techniques CE, capillary isoelectric focusing (cIEF), capillary gel electrophoresis (CGE), and affinity capillary electrophoresis (ACE). Weinberger presents a comprehensive approach for method development in CE with an emphasis on small-molecule applications. This is followed by Kilar s chapter describing the principles of and method development in cIEF, as well as recent innovations... 

Expenses for taxes and insurance play an important part in determining the economic situation for any industrial process. Because Federal, state, and local taxes may amount to a major portion of a concern s earnings, it is essential for the chemical engineer to understand the basic principles and factors underlying taxation. Insurance costs ordinarily are only a small part of the total expenditure involved in an industrial operation however, adequate insurance coverage is necessary before any operation can be carried out on a sound economic basis. 

The production of flat-panel cathode ray tubes (CRTs) is essentially a fabrication issue. The basic principle of operation is the same as a standard CRT. Electrons are emitted from a hot cathode. These are guided by a magnetic field to the glass screen coated in a layer of phosphorescent material. Upon impact the energy of the electron is transferred to the phosphor and light is emitted. A regular pattern of red, green and blue phosphors creates a dense pattern of... 

In order to understand the basic principles of operation of the many different kinds of LCDs being developed and/or manufactured at the present time, it is necessary to briefly describe the liquid crystalline state and then define the physical properties of direct relevance to LCDs. First, the nematic, smectic and columnar liquid crystalline states will be described briefly. However, the rest of the monograph dealing with liquid crystals will concentrate on nematic liquid crystals and their physical properties, since the vast majority of LCDs manufactured operate using mixtures of thermotropic, non-amphiphilic rodlike organic compounds in the nematic state. 

HtMMELBLAU, D. M., Basic Principles and Cdlculatiarts in Chemical Engineering, 4th ed. Upper Saddle River, N.J. Prentice Hall, 1982, Chaps. 4 and 6. Westerwerp, K. R., W, P. M. Van Swaad, and A. A. C. M. Beenackers, Chemical Reactor Design and Operation, New York Wiley, 1984. 

Hot packs and cold packs are sold in various sports supply stores and pharmacies for the treatment of muscle ache and sports injuries. Although usually made with different salts, the basic principles of operation are the same as the preceding demonstration. 

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