Active Balancing

Figure 1. The basic processes influencing the activity balance of radon and radon daughters in houses.

Material equilibrated Max H Temperature (°C) Activity balance (%) a (cpm of solid 1 cpm of gas) Structure of alloy... 

We note that fission product activity balance requires that the specific activity of a volatile chain increase more rapidly than a refractory chain with decreasing diameter because of the large depletion factors noted in 89Sr/144Ce in large sizes. 

Correia-de-Sd P, Timotco MA, Ribeiro JA (1996) Presynaptic Ai inhibitory/A2A fadlitatory adenosine receptor activation balance depends on motor nerve stimulation paradigm at the rat hemidi-aphragm. J Neurophysiol 76 3910-19... 

Most of the active balancing devices, specifically developed for the DLC, turn out to be a subgroup of the passive systems. The cell voltages are monitored by a survey equipment. When one of these cells reaches or overcomes a preset threshold level, a bypass is activated by an interrupter (transistor). This opens a path for the current which may flow in a dissipative resistor [56,57], This method limits the self-discharge amplitude to a minimum value because the system is working only when necessary. 

Activation energy, stability in trickle-bed reactors, 76 Activation overpotential, cross-flow monolith fuel cell reactor, 182 Activity balance, deactivation of non-adiabatic packed-bed reactors, 394 Adiabatic reactors stability, 337-58 trickle-bed, safe operation, 61-81 Adsorption equilibrium, countercurrent moving-bed catalytic reactor, 273 Adsorption isotherms, countercurrent moving-bed catalytic reactor, 278,279f... 

Bruhn H, Frahm J, Gyngell ML et at (1989). Cerebral metabolism in man after acute stroke new observations using localized proton NMR spectroscopy. Magnetic Resonance Medicine 9 126-131 Calautti C, Naccarato M, Jones PS et at (2007). The relationship between motor deficit and hemisphere activation balance after stroke a 3T fMRI study. Neuroimage 34 322-331... 

For nuclides that are fully sorbed, i.e., / , = oo eq. (4) is modified into equation of activity balance in sorbed phase ... 

Figure 3 shows simulated spatial distributions of TDS concentration and log of fluid total activity for 300 years of simulation obtained by the fully coupled model. This figure indicates that decreasing of fluid viscosity in the heat-generating zone makes potential for upward transport of small concentration of TDS and activity. The influence of coupled effects on waste transport is shown in table 2 and 3. These tables summarize the results of overall activity balance calculation for 100 years and TDS balance for 300 years for non-coupled and fully coupled models. 

Table 2. Overall total activity balance % for 100 years. First row is non-coupled model and second...

About 5000 m s of sea water reacts with fresh hot basalt in the rift zones. Hydrothermal reactions produce large changes in the composition of the sea salts. The reactions lead to a loss of magnesium, sulfate, and fluoride, but to an addition of calcium and potassium. The hydrothermal activity balances some of the river inputs and contributes to maintenance of the steady state and the conservation of the constant composition of sea salts. 

The activity balance is provided by two unknown peaks (2.7%), whose retention times on both GC columns used are greater, yet very close, to that of jj-fluoro-toluene. 

As with PWRs, several attempts have been made to describe activity and contamination buildup in BWR plants by computerized models. These models are essentially based on materials balances for the iron transport and on materials and activity balances for the cobalt transport. The reaction rates and the reaction orders needed for the calculations in the partly very complex models are in most cases empirical values or even assumptions. The principles of some of the models have been outlined e. g. by Ishigure (1987) and by Alder et al. (1992). 

FIGURE 10.284 The concept of common-mode rejection ratio (CMRR) for an active-balanced input circuit (a) differential gain measurement (b) calculating CMRR. 

FIGURE 10.285 The simplest and least expensive active-balanced input op-amp circuit. Performance depends on resistor-matching and the balance of the source impedance. 

Early active-balanced output circuits used the approach shown in Fig. 10.288. The signal is buffered to provide one phase of the balanced output. This signal then is inverted with another op-amp to provide the other phase of the output signal. The outputs are taken through two resistors, each of which is half of the desired source impedance. Because the load is driven from the two outputs, the maximum output voltage is double that of an unbalanced stage. 

FIGURE 10.286 An active-balanced input circuit using two op-amps one to invert the positive input terminal and the other to buffer the difference signal. Without adjustments, this circuit will provide about 50 dB CMRR. 

FIGURE 10.287 An active-balanced input circuit using three op-amps to form an instrumentation-grade circuit. The input signals are buffered, then applied to a differential amplifier. 

FIGURE 10.288 A basic active-balanced output circuit. This configuration works well when driving a single balanced load... 

As the performance of electronic equipment improved, transformers kept pace with reduced distortion and broadened frequency response. Their physical size and weight, however, made them inconvenient for use in the ever shrinking chassis of transistorized equipment. As solid-state technology became standard, designers sought ways to eliminate transformers. The result was electronically (active) balanced inputs and outputs (I/O). 

The move away from transformers introduced several unexpected problems. Installation practices that provide acceptable performance with transformer-isolated equipment may not work for active balanced I/O equipment. Active balanced circuits can be less forgiving of wiring faults and short circuits some output stages will self-destruct if shorted. Avoidance of ground loops is more important with an active balanced system than with transformers. Active balanced input circuits can provide excellent noise rejection under ideal conditions. In the real world, however, their noise rejection can deteriorate rapidly. Transformers remain the best choice for the toughest situations. 

FIGURE 16.26 Common mode rejection ratio for an active balanced input circuit. 

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