Power analysis of embedded software: a first step towards softwarepower minimization

Embedded computer systems are characterized by the presence of a dedicated processor and the software that runs on it. Power constraints are increasingly becoming the critical component of the design specification of these systems. At present, however, power analysis tools can only be applied at the lower levels of the design-the circuit or gate level. It is either impractical or impossible to use the lower level tools to estimate the power cost of the software component of the system. This paper describes the first systematic attempt to model this power cost. A power analysis technique is developed that has been applied to two commercial microprocessors-Intel 486DX2 and Fujitsu SPARClite 934. This technique can be employed to evaluate the power cost of embedded software. This can help in verifying if a design meets its specified power constraints. Further, it can also be used to search the design space in software power optimization. Examples with power reduction of up to 40%, obtained by rewriting code using the information provided by the instruction level power model, illustrate the potential of this idea     

Performance of a double-star synchronous generator with bridgerectified output

In this paper, the performance of a double-star synchronous generator with bridge rectified output is studied from the fundamental machine equations. The generator has two stator windings shifted by π/6 electrical radians, which with their bridges can be connected either in series or in parallel. Therefore the double-star synchronous generator with rectifier load can have two major operation modes. Using the fundamental machine equations, the expressions of displacement angles and commutation angles are derived under these operation modes. The performance of the double-star synchronous generator with bridge rectified output can be predicted from given load current, field current, generator speed, bridge delay angle and its parameters. Theoretical results are compared with experimental results obtained from a laboratory machine     

Unconventional energy sources

Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 2, pp. 49–52, February, 1991.     

Biomechanical evaluation of lift postures in adult Koli female labourers

Three lift-postures, back straight and knees bent, back bent and knees straight and squatting were evaluated biomechanically based on data from 100 Koli female labourers, when lifting loads from the floor to hold them at knee height. The maximum weight was lifted with the back bent and the knees straight which is a posture commonly used by Indian labourers for lifting a load. Squatting (a posture used by Indians for performing household chores) produced the least physical strain in terms of moment and moment ratio (moment per kilogramme of load lifted). Consequently, squatting was found to be the best posture for lifting a load, specifically for the Indian labourers who are accustomed to squatting when working.     

Implementation and laboratory test results for a fuzzy logic basedself-tuned power system stabilizer

Implementation of a fuzzy logic-based self-tuned controller as a power system stabilizer (PSS) is described. The stabilizing signal generated by the controller is computed using a standard fuzzy membership function and a self-tuned parameter. The calculation is based on the representation of the alternator state in the phase plane. Real-time test results are presented for various operating conditions and disturbances. The results obtained demonstrate the effectiveness and improved response of the implemented PSS compared with the conventional stabilizer. The proposed controller does not require any parameter identification in real time and has a much simpler algorithm than that for a self-tuning controller. The performance of the proposed stabilizer is demonstrated by practical implementation using a digital signal processor mounted on a PC-AT. Results of the experimental tests on a physical model of a power system are presented     

Effect of heat treatment procedures on site preferences of Fe in YBa2Cu3O7−D

Mössbauer spectra of YBa₂Cu_2·85Fe_0:15O_7?d prepared using different heat treatment procedures have been obtained. The transition temperature varies from 23 to 53 K, depending on the procedure adopted for preparation. Associated with this are changes in the lattice structure. Mössbauer spectra reveal population of the four components and their relation to the decrease in the transition temperatures.     

Voltage control of parallel operated self excited inductiongenerators

Two methods of analysis are proposed for use in the control of the common bus voltage of any number of parallel self-excited induction generators (SEIGs) under steady state balanced conditions. The methods are general and can be used for a single SEIG or a group of SEIGs employing similar or different machines with equal or unequal prime mover speeds. Theoretical predictions of the two models have been verified experimentally. Using these methods, effects of various parameters on the voltage control characteristics are examined for a number of cases employing similar and different SEIGs at equal and unequal speeds     

Negative base current and impact ionization phenomena inAlGaAs/GaAs HBTs

Impact ionization phenomena in the collector region of AlGaAs/GaAs heterojunction bipolar transistors give rise to base current reduction and reversal. These phenomena can be characterized by extracting the M-1 coefficient, which can be evaluated by measuring base current changes. Measurements of M-1 are affected at low current densities by the presence of the collector-base junction reverse current I_CBO. At high current densities, three effects contribute to lower the measured M-1 value: voltage drops due to collector (R_C) and base (R_B) parasitic resistances, device self-heating, and lowering of the base-collector junction electric field due to mobile carriers. By appropriately choosing the emitter current value, parasitic phenomena are avoided and the behavior of M-1 as a function of the collector-base voltage V_CB in AlGaAs/GaAs HBTs is accurately characterized