Maximum Attainable Accuracy Research Articles

Logarithmic singularity in the specific heat in the vicinity of phase transitions in uniaxial ferroelectrics

Using precise vacuum adiabatic calorimetry it is shown that the specific heat of the model ferroelectric crystal TGS does not exhibit the logarithmic singularity predicted by theory above the transition temperature. This discrepancy with the available specific heat data in the literature, obtained by dynamical measurements, is discussed with allowance for the maximum attainable measurement accuracy (0.3%) in the static adiabatic experiment.

Wide-band measurements of dc voltages using two-parametric amplitude adaptation

A method of analyzing the accuracy and speed of adaptive measuring instruments based on two-parametric iteration algorithms of amplitude adaptation in precision high-speed dc voltage measurements is discussed. The method makes it possible to estimate the real and maximum attainable accuracy of adaptive dc voltage measurements over a wide dynamic range.

On the limitations of geomagnetic measures of interplanetary magnetic polarity

The maximum attainable accuracy in inferring the interplanetary magnetic polarity from polar cap magnetograms is about 88 %. This is achieved in practice, when high latitude polar cap stations are used during local summer-months, and the signature in the ground records is strong. An attempt by Svalgaard (1972) to use this effect to infer an index of interplanetary magnetic polarity back to 1926 has not been so successful. Furthermore, some of the properties of the index have changed with time. Prior to 1963, the inferred polarities are strongly dependent on geomagnetic activity, while after this time they are not. Thus, this index should not be used to separate solar-magnetic from solar-activity effects prior to 1963.

Acoustic Ray Tracing on the General-Purpose Electronic-Analog Computer

A simulation of the trajectory of underwater acoustic rays is implemented on a general-purpose electronic-analog computer. Equations defining the phenomena are summarized, assumptions are listed, and a preferred form of the equations is developed to provide maximum attainable accuracy of solution. Included are considerations of the velocity of sound as an arbitrary function of both depth and range, and the effects of reflections from both the surface and an arbitrary bottom. A complete computer diagram is presented and special circuits are described. Typical results of depth versus range are shown for varying launch depths and launch angles. A method of obtaining the difference in time required for rays leaving a common emitter at various angles to reach a common receiver is also derived. By use of perturbations, Taylor series expansions, and the method of steepest descents to insert the constraint cos ?/c = constant, the overall error in this highly sensitive computation has been reduced to 0.01 per cent or better.

A new collector of solar radiant energy—Theory and experimental verification

An effective quality control is essential for a large-scale dissemination of solar thermal technologies on the products being offered by the industry to the end users. For this, there is a need to establish test procedures and methodologies for producing performance characteristic parameters, which could provide an equitable basis for comparison of performances of these products. At present, paraboloid concentrator type solar cooker technology is moving towards the phase of commercialization in India. For the thermal performance evaluation of paraboloid concentrator type solar cooker, Mullick et al. (1991) developed a test procedure that essentially recommends determination of optical efficiency factor (F′ηo) and heat loss factor (F′UL) based on heating and cooling tests. Further a test method has been proposed by Funk (2000) for testing of all kind of solar cookers that characterizes the performance of solar cooker by two parameters, namely, adjusted cooking power (Pa) and overall heat loss coefficient (UL) as obtained from heating test. These are the only test methods available for testing of paraboloid concentrator type solar cooker.The present communication analyzes the effect of instrumentation, on the values of F′ηo, F′UL, Pa and UL, which is supported by a large number of outdoor tests conducted on a paraboloid concentrator type solar cooker under heating and cooling test conditions. The role of individual associated parameters on F′ηo, F′UL, Pa and UL has been analyzed along with the estimation of overall error in these values due to the error in the determination of associated parameters. Though the maximum attainable accuracy in determining F′UL varies from 1.15% to 0.65% (for loads of 1.0 to 8.0 kg), the associated error in the determination of F′ηo is quite high viz. 5.13% to 5.04% for the same load conditions. Similarly, the maximum attainable accuracy in the determination of standardized cooking power has been observed from 4.98% to 5.02% under the load conditions from 1.0 to 8.0 kg.

Underwater Acoustic Ray Analysis

A simulation of the trajectory of underwater acoustic rays was implemented on a general purpose electronic analog computer. Equations defining the phenomena are summarized, assumptions are listed and included, and a preferred form of the equations is developed to provide maximum attainable accuracy of solution. Included are considerations of the velocity of sound as an arbitrary function of both depth and range and the effects of reflections from the surface and an arbitrary bottom. Complete computer diagram is presented and special circuits are described. Typical results of depth versus range are shown for varying launch depths and launch angles. A method of obtaining the difference in time required for rays leaving a common emitter at various angles to reach a common receiver is also covered. Finally, provision for computing spreading loss as a function of range is described.

The distribution of solar radiation over the earth's surface : Black, J. N. Arch. Meteor. Geophys. Bioklimatol. B, 7(2): 165–189, 1956

An effective quality control is essential for a large-scale dissemination of solar thermal technologies on the products being offered by the industry to the end users. For this, there is a need to establish test procedures and methodologies for producing performance characteristic parameters, which could provide an equitable basis for comparison of performances of these products. At present, paraboloid concentrator type solar cooker technology is moving towards the phase of commercialization in India. For the thermal performance evaluation of paraboloid concentrator type solar cooker, Mullick et al. (1991) developed a test procedure that essentially recommends determination of optical efficiency factor (F′ηo) and heat loss factor (F′UL) based on heating and cooling tests. Further a test method has been proposed by Funk (2000) for testing of all kind of solar cookers that characterizes the performance of solar cooker by two parameters, namely, adjusted cooking power (Pa) and overall heat loss coefficient (UL) as obtained from heating test. These are the only test methods available for testing of paraboloid concentrator type solar cooker.The present communication analyzes the effect of instrumentation, on the values of F′ηo, F′UL, Pa and UL, which is supported by a large number of outdoor tests conducted on a paraboloid concentrator type solar cooker under heating and cooling test conditions. The role of individual associated parameters on F′ηo, F′UL, Pa and UL has been analyzed along with the estimation of overall error in these values due to the error in the determination of associated parameters. Though the maximum attainable accuracy in determining F′UL varies from 1.15% to 0.65% (for loads of 1.0 to 8.0 kg), the associated error in the determination of F′ηo is quite high viz. 5.13% to 5.04% for the same load conditions. Similarly, the maximum attainable accuracy in the determination of standardized cooking power has been observed from 4.98% to 5.02% under the load conditions from 1.0 to 8.0 kg.