Optimizing the locations of the measuring points for an online calculation of the exhaust flue-gas loss

Flue gas properties are very important for evaluation of a boilers performance. Non-homogeneity of the properties and large dimensions of flue-gas ducts require measurements with large number of measuring points to provide high accuracy of measurement results. An analysis of simpler measuring methods is presented. It is shown that high accuracy can be achieved with small number of measuring points if their positions are optimised with respect to pre-determined conditions in the flue gas duct. The methods can be used as operational measurements to monitor boilers performance and for on-line calculation of boilers efficiency.

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Zusammenfassung Messungen der Rauchgaseigenschaften sind sehr wichtig zur Bestimmung der Kesselleistung. Aufgrund der Inhomogenität der Rauchgaseigenschaften und der großen Ausmaße von Rauchgasleitungen ist die Messung mit einer großen Anzahl an Messpunkten erforderlich, um eine hohe Genauigkeit der Messergebnisse zu erzielen. Hier wird die Analyse einfacher messtechnischer Verfahren vorgestellt. Es hat sich gezeigt, daß eine hohe Messgenauigkeit mit einer geringen Anzahl an Messpunkten dann erzielt werden kann, wenn die Lage der Messstellen unter Berücksichtigung der vorausbestimmten Rauchgaseigenschaften in der Rauchgasleitung optimiert wird. Dieses Verfahren eignet sich für die Durchführung von Messungen bzw. zur Überwachung der Kesselleistung und zur Online-Berechnung des Kesselwirkungsgrades.

     

The problem of choosing the points for measurement monitoring of measuring instruments

A method is proposed for solving the problem of choosing the monitoring poinst of measuring instruments on the basis of identifying their error function using the compactness maximum method. Translated from Izmeritel'naya Tekhnika, No. 9, pp. 69–72, September, 1998.     

Algorithms for the calculation of limit and bifurcation points using Lanczos methods

The computation of limit and bifurcation points in structural mechanics using iterative preconditioned Lanczos solvers is studied. Contrary to classical implementations of algorithms for the calculation of limit and bifurcation points, which depend in general strongly on observing the diagonal elements of the decomposed matrix – obtained by a Gauß- or Cholesky decomposition – , we use an approach of determining limit and bifurcation points by examination of the subspace spanned by the iteration vectors of the Lanczos solver. Using a multilevel preconditioning with a coarse grid solver may result in a non positive definite preconditioning matrix if the coarse grid matrix is not positive definite in the post-critical solution branch. In that case the iteration has to be performed in the complex vector space. We prove by mathematical induction that all vectors and scalars are either purely real or purely imaginary. Therefore the generalized computation can be performed with about the same number of operations as in the case of a positive definite preconditioning matrix.     

Method free from mismatching errors for measuring the loss of attenuators

Summary The method of evaluating the attenuation by measuring the ratio of voltages or powers in the lateral branches of two directional couplers, between which the attenuator is placed, provides a complete elimination of two of the three components of the matching error.In order to reduce residual errors, the directional coupler at the input of the attenuator must have a good directivity, and the directional coupler at its output must have small reflections from its flanges and from the load in its main branch.It is possible to eliminate completely in the first approximation the matching eror by using a sliding load (or any other method of phase adjustment).     

Hybrid neuro-fuzzy approach to the generation of measuring points for knowledge-based inspection planning

A knowledge-based inspection planning system is presented that can generate effective and consistent inspection plans automatically. The knowledge-based inspection planning system integrates part geometry information, tolerance information and heuristic knowledge of experienced inspection planners to determine the numbers and positions of measurement points. The system receives the tolerance information from users and stores it in the common database with 3D CAD geometry. A set of fuzzy rules and membership functions is automatically extracted from historic learning data using a hybrid neuro-fuzzy method. After the fuzzy rules are generated by the hybrid neuro-fuzzy model, a genetic algorithm is applied to optimize the weight parameters to find the best values for the constants. The proposed knowledge-based inspection planning system provides the stable and consistent inspection plan by removing the subjectivity of a human planner.     

Computer-aided calculation of errors of measuring instruments

Translated from Izmeritel'naya Tekhnika, No. 1, pp. 16–18, January, 1989.     

Optimizing the magnetic system parameters inside a measuring coil

Conclusions The magnetic core inside the coil of a magnetic measuring system has an optimal diameter to height ratio d_m/h_m for which the torque is maximal. The magnet diameter and height depend on the coil perimeter P, and their optimal ratio K_F is practically independent of the coil perimeter but depends on the alloy of which the magnet is made. Implementing optimal magnet dimensions makes possible fuller utilization of the energy of a permanent magnetic core inside the magnetic system coil. If the optimal ratio of magnet diameter to its height is known, calculation of the magnetic system parameters and the design of the entire measuring instrument becomes quite simple.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 32–34, April, 1991.     

Coaxial line methods for measuring permittivity and dielectric loss

Two coaxial line techniques for the determination of complex permittivities of solid and liquids are described. The first, the matched termination method, is essentially a comparison technique using air as the reference dielectric, producing accurate values of . In the second, the resonant line method, the characteristic impedance termination is replaced by an adjustable short circuit. This method was developed primarily for the purpose of determining the values of tan in low loss materials. Both methods can be used for frequencies in the 200 MHz to 9 GHz range and normally require only conventional apparatus. The results obtained for the materials under test agreed well with the published data, thus underlining the suitability of the two techniques for dielectric measurements.     

A neural network-based algorithm that searches for the measuring points of a rule surface

The purpose of this study is to use a proposed neural network-based algorithm to explore the determination of the recommended measuring points for a rule surface. The task of measuring a rule surface starts from the rule surface design blueprint. Mesh grid data on the designed rule surface were selected. The pattern recognition capability of the back-propagation neural network is explored in this article. The network learning was successfully performed by the learning and testing of the network, the support of a designated acceptable perpendicular error value, a learning model in which training examples were gradually added and the adjustment of the number of training examples according to the network structure.     

Social embeddedness in an online weight management programme is linked to greater weight loss

The obesity epidemic is heightening chronic disease risk globally. Online weight management (OWM) communities could potentially promote weight loss among large numbers of people at low cost. Because little is known about the impact of these online communities, we examined the relationship between individual and social network variables, and weight loss in a large, international OWM programme. We studied the online activity and weight change of 22 419 members of an OWM system during a six-month period, focusing especially on the 2033 members with at least one friend within the community. Using Heckman''s sample-selection procedure to account for potential selection bias and data censoring, we found that initial body mass index, adherence to self-monitoring and social networking were significantly correlated with weight loss. Remarkably, greater embeddedness in the network was the variable with the highest statistical significance in our model for weight loss. Average per cent weight loss at six months increased in a graded manner from 4.1% for non-networked members, to 5.2% for those with a few (two to nine) friends, to 6.8% for those connected to the giant component of the network, to 8.3% for those with high social embeddedness. Social networking within an OWM community, and particularly when highly embedded, may offer a potent, scalable way to curb the obesity epidemic and other disorders that could benefit from behavioural changes.     

Method for measuring and characterizing core loss in a motor

Because of the complex shape and variable flux densities of the toothed cores of motors, characterization of their core losses has been difficult. Manufacturers' material specification sheets usually refer only to Epstein tests, based on sinusoidally varying flux densities in simple geometries. Here, a more accurate and direct method for measuring core loss is presented. The method spins the motor core in a magnetic field and then measures the spin speed and drag torque imposed on the core. This test was used to successfully characterize the core loss in a small dc brushless spindle motor. Among the parameters examined were the turning speed, maximum gap flux, lamination material, lamination thickness, and the effects of stress-relief annealing. Mathematical models of the core loss were constructed for specific core geometries based upon an assumed form for the empirical data. The actual core losses were higher than would have been predicted from conventional Epstein tests     

An improved technique for measuring hysteresis loss in superconducting magnets

This technique is based on an XY display of the hysteresis loop of a magnet; the hysteresis loss is proportional to the loop area. It is shown that the shape and area of the loop are simply related to the short sample properties of the superconductor. Extraneous effects in a magnet can sometimes distort the loop and this enables the technique to be used as a diagnostic tool in magnet testing.     

Heat calculation for the cover of an electrolytic bath

A heat calculation based on the assumption of isothermality sometimes leads to large errors. Local overheating can affect the normal operation of a component. Hence, an accurate heat calculation requires the solution of the heat-conduction equation, which is difficult for components of complicated shape. This paper gives an example of such a calculation.     

An a priori assessment of the number of measuring devices and their locations in an experimental evaluation of the efficiency of a cryogenic plant

Translated from Izmeritel'naya Tekhnika, No. 11, pp. 42–44, November, 1992.