Electrically complex systems

An electric power system involves the production and transportation of electrical energy from generating facilities to energy-consuming customers. This is accomplished through a complex network of transmission lines, switching and transformer stations. 

The reliability of a modern electric power system depends on continuous real-time control of power and energy production, transmission line flows, system frequency, and voltage. This complex task will get more involved in the new environment with increased market participation on both the supply and the demand sides. 

The North American electric power transmission system has been described as the largest, most complex machine ever built by humanity. It is a massive network of generating stations, transmission lines, substations, distribution lines, motors, and other electrical loads all interdependently linked for the conversion, transportation, and control of electrical energy. Approximately 60 percent of all energy utilized in the United States passes through the interconnected electric power system. The major goal of the system is to most efficiently and reliably deliver electric power from generating stations to residential, commercial, and industrial consumers. 

One example of the complexity of the process was in load forecasting technology. By the 1960s and 1970s, utilities had developed processes to replicate the extensive electric power system for study purposes to include generation resources, transmission networks and individual points of load seiwice to customers. The... 

Modern representations of the virtual heart, therefore, describe structural aspects like fibre orientation in cardiac muscle, together with the distribution of various cell types, active and passive electrical and mechanical properties, as well as the coupling between cells. This then allows accurate reproduction of the spread of the electrical wave, subsequent contraction of the heart, and effects on blood pressure, coronary perfusion, etc. It is important to point out, here, that all these parameters are closely interrelated, and changes in any one of them influence the behaviour of all others. This makes for an exceedingly complex system. 

In addition to the described above methods, there are computational QM-MM (quantum mechanics-classic mechanics) methods in progress of development. They allow prediction and understanding of solvatochromism and fluorescence characteristics of dyes that are situated in various molecular structures changing electrical properties on nanoscale. Their electronic transitions and according microscopic structures are calculated using QM coupled to the point charges with Coulombic potentials. It is very important that in typical QM-MM simulations, no dielectric constant is involved Orientational dielectric effects come naturally from reorientation and translation of the elements of the system on the pathway of attaining the equilibrium. Dynamics of such complex systems as proteins embedded in natural environment may be revealed with femtosecond time resolution. In more detail, this topic is analyzed in this volume [76]. 

An ionophoretic method was described by Tewari [41] for the study of equilibria in a mixed ligand complex system in solution. This method is based on the movement of a spot of metal ion in an electric field with the complexants added in the background electrolyte at pH 8.5. The concentration of the primary ligand (nitrilo-triacetate) was kept constant, while that of the secondary ligand (penicillamine) was varied. The stability constants of the metal nitrilotriacetate-penicillamine complexes have been found to be 6.26 0.09 and 6.68 0.13 (log K values) for the Al(III) and Th(IV) complexes, respectively, at 35 °C and an ionic strength of 0.1 M. 

One of the applications of TRXRD is to study complex systems where electric fields couple to multiple degrees of freedom. Though femtosecond laser pulses can generate THz radiation from ferroelectric LiTa03, the corresponding lattice motion remained undetected by optical measurements. Cavalleri and coworkers demonstrated the coherent modulation of the X-ray intensity at 1.5 THz [10], and assigned it as phonon-polariton mode of A symmetry (Fig. 3.3). Nakamura and coworkers detected the coherent LO phonon of CdTe... 

Potassium channels are part of a complex system that helps maintain the normal ionic balance across the cell membrane. In excitable cells, like those in nerves and muscles, the channels also help reestablish the electrical difference between the inside and outside of the cells after excitation. In the case of neuron firing, potassium ions, and thus positive charge, builds up inside the... 

Kwon and coworkers described solid polyelectrolyte complex systems which dissolve rapidly in response to small electric currents. The solid doses were based on poly(ethyl oxazoline) and poly(methacrylic acid) with a repeating unit stoichiometry of 1 1. Insulin was released in response to slight electric currents due to electrically induced polymer dissolution [380]. In similar work Kwon and coworkers [381] studied release of edrophonium chloride and hydrocortisone from poly(2-acrylamido-2-methylpropane sulfonate-co-n-butyl methacrylate). An on/oflf mechanism of the edrophonium chloride release was observed and was attributed to ion exchange of solute and hydroxonium ion. The cationic solute release was assisted by electrostatic forces, whereas release of the neutral hydrocortisone solute was only affected by swelling and deswelling. 

The first carbon nanotubes discovered in nature, such as those produced in Iijima s experiments, were multiwalled nanotuhes (MWNT). Multiwalled nanotuhes consist of a number of concentric carbon cylinders, a set of tubes nested inside each other. They are somewhat complex systems that are relatively difficult to study. An important step forward in research on carbon nanotuhes occurred in 1993, when scientists learned how to make single-walled nanotubes (SWNT). Using the simpler SWNTs, scientists have learned quite rapidly a great deal about the electrical conductivity, tensile strength, flexibility, toughness, and other physical properties of carbon nanotuhes. 

When a voltage step is applied to the simple RC parallel circuit shown in Fig. 2.54 the response current decays to zero in a manner describable by a single relaxation time. The frequency response of the impedance also yields a semicircle as shown below. Such a circuit can represent a lossy capacitor, and more elaborate combinations of resistors and capacitors correspondingly more electrically complex materials and systems. It is this rather more general approach which is described by impedance spectroscopy . 

The work which is reviewed here provides accurate structural data from micro-wave and radiofrequency spectroscopy of relatively small molecule, hydrogen bonded complexes. Its role has been to provide information concerning the stereochemistry and electronic properties — electric dipole moments and nuclear hyperfine interactions — characteristic of hydrogen bonds. The experiments are done on gas phase samples, often in molecular beams, which eliminates environmental perturbations of the hydrogen bonds. In addition, the small molecules used are amenable to ab initio calculations 7 9) and thus the results are extremely useful as criteria for the accuracy of these calculations. Finally, the results are useful to construct models of more complex systems in chemistry and biology involving hydrogen bonds 4). 

In grate-fired boilers, the biomass is fed in a thin layer, so it is evenly distributed over a sloped stationary, traveling, or vibrating grate. Improved control over the combustion process can be achieved with better carbon conversion. Fluidized-bed combustors are more complex systems, but offer much better control of combustion temperature, improved carbon conversion, and fuel flexibility. Using a boiler to produce both heat and electricity (co-generation) can improve the overall system efficiency to as much as 85 percent. Boiler efficiencies are affected by fuel moisture content, air-fuel ratio, excess air, combustion temperature, and biomass ash content. 

Nearly 160,000 miles of high-voltage electrical transmission lines in the United States carry power from power stations to load centers (Edison Electric Institute, 2002). In addition, distribution lines carry the power from substations to end users. The electrical power system is fundamentally different from the liquid or gaseous fuel supply systems, which involve fluid flows that are relatively easy to direct and control. Electric power flow, which is dictated by complex physics principles, can often be difficult to control. 

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