## IMEKO Event Proceedings

Page 787 of 822 Results 7861 - 7870 of 8218

**Uncertainty evaluation of totalization of flow and volume measurements in drinking water supply networks**

Clean water and sanitation are one of the 17 sustainable development goals (SDG) of the United Nations’ 2030 agenda for action, being directly related to several other objectives, namely, economic growth, sustainable cities’ communities, responsible consumption and production, and climate action. Since demand for this resource is constantly growing, problems of scarcity of water and transboundary issues are becoming critical to increase water supply efficiency and to improve water management in modern society. Water providers make use of large infrastructures – water supply networks – defined as engineering systems based on hydrological and hydraulic elements able to supply water to consumers, industries, facilities, services and other users. These infrastructures rely on the quality of measurement as a condition to management, having a relevant role in the process of decision-making and to deal with the common problem of water losses. Good measurement practices and uncertainty evaluation are needed to support robust analysis in urban water supply systems. For many water utilities the evaluation of uncertainty is still considered a difficult task, often in situations of missing data for the analysis, having to deal with large amounts of raw and processed data, and requiring support to apply the provisions of the Guide to the expression of uncertainty in measurement (GUM). However, the application of the GUM to the simple mathematical models used in this context makes it possible to obtain simplified equations that can be used in specific conditions of measurement, providing support to non-expert users with more straightforward approaches. Those include measurement of constant flow, totalization of volume at a single measurement point, and sums and differences obtained by combining branches of a network.

**Uncertainty Evaluation Problems in Measurements of Volume and Surface Resistivities**

The problems associated with evaluation of uncertainty of volume and surface resistivities were presented in the paper. Special attention was paid to the measurements carried out on extremely high resistivity materials. Different factors affecting the uncertainty were classified and estimated. A simplified method of uncertainty evaluation was proposed.

**Uncertainty Evaluation: Analysis of Simultaneous Measurement of Multiple Measurands**

The Guide to the expression of uncertainty in measurement (GUM) (ISO,1995), contains internationally agreed recommendations for the evaluation and expression of uncertainties in a measurement process, providing valuable advise for constituting the model that relates input to output quantities.

If a probability density function is associated with each of input quantities, a probability “region” for the outputs quantities (the measurands) can be derived and its level of confidence may be evaluated by analytical or numerical methods.

This paper analyzes the uncertainty evaluation of a process concerning simultaneous measurement of multiple measurands on the base of the fundamental properties of the probability confidence region.

**UNCERTAINTY EVALUATIONOF A 3D VISION SYSTEM: COMPARISON OF MONTE CARLO SIMULATION WITHA CLASSICAL EXPERIMENTAL CALIBRATION**

The Guide to the Expression of Uncertainty in Measurement has some limitations, especially for systems with complex mathematical models. In this article, two alternative methods to obtain the measurement uncertainty (Monte-Carlo simulation and calibration based on experimental measurement) are compared. These methods are widely used to calculate the measurement uncertainty of measurement systems. The advantages and disadvantages of these two methods are going to be studied estimating the uncertainty of the flatness measurement using a system based on laser triangulation. The measurement system captures images of the laser plane projected in the surface to be digitalized. The laser pointsin each image are identified and extracted and transformed into 3D coordinates to calculate the flatness of the surface. The influence of different factors will be characterized and the results of the estimation of the uncertainty with both Monte Carlo simulation and the calibration based on experimental measurement will be compared as well as the characteristics and requirements of each procedure.

**Uncertainty factors in time-interval measurements in ballistocardiography**

There is a growing interest on measuring time intervals between the J peak of the ballistocardiogram (BCG) and several features of other cardiovascular signals such as the ECG in order to obtain cardiovascular function markers. Nevertheless, possible uncertainty factors involved in these measurements have not been identified and analyzed, which is a necessary step to advance towards standardization in this reemerging biomedical engineering field. In this paper we analyze the effect of the low-pass cutoff frequency and phase characteristic of filters, noise and power line interference on J-peak time measurement. We conclude that BCG acquisition systems require a minimum low-pass cutoff frequency of 25 Hz but the phase angle of filters at this frequency introduce more than 6 ms delay that increases with increasing filter order. Further, SNR and power line interference levels respectively below about 25 dB and 30 dB, commonly found in data acquisition systems in this area, may lead to uncertainties in the time position of the J peak of tens of milliseconds, which are comparable to measured time interval changes that may have diagnostic interest.

**UNCERTAINTY FOR NOISE ATTENUATION MEASUREMENTS OF HEARING PROTECTORS BY REAT METHOD**

The objective of this paper is to present a model for the calculation of measurement uncertainty for noise attenuation measurements of hearing protector by REAT method. The uncertainty calculation was based on the document: "Guide to expression of uncertainty in measurement" by the International Organization for Standardization, first edition, corrected and reprinted in 1995, Geneva, Switzerland. The uncertainty of each source of error was estimated. The overall uncertainty of the noise attenuation measurement of hearing protectors was calculated for each 1/1 octave band frequency test and the results applied in the single number (NRRSF - Noise Reduction Rating for subject fit) uncertainty calculation.

**UNCERTAINTY IMPROVEMENT OF GEOMETRICAL THICKNESS MEASUREMENT OF A SILICON WAFER USING A FEMTOSECOND PULSE LASER**

We describe a method to simultaneously measure geometrical thickness and refractive index of a silicon wafer using a femtosecond pulse laser having 100 nm spectral bandwidth. The improved phase measurement algorithm is applied to increase insensitivity to environmental disturbances and interferometer noise. The measurement results show that the geometrical thickness and refractive index of a silicon wafer were measured to be 320.699 µm and 3.621 respectively, which are the improved results by about one order of magnitude in comparison with previous research. By considering the dispersion effect caused by 100 nm bandwidth source, the conclusion can be reached that there is no dispersion effect on measurement of geometrical thickness.

**UNCERTAINTY IN MEASUREMENT: A KEY CRITERION FOR DEFINING THE COVERAGE FACTOR ASSOCIATED WITH THE MANUFACTURING PROCESS OF WOVEN FABRICS**

This study evaluates the *fractional coverage factor* (Cf_{T}) of a woven fabric before and after the manufacturing process is completed. The uncertainty associated with Cf_{T} was evaluated for specific conditions of mechanical strain of the thread yarns during the weaving process. The economic impact from undesirable geometric deviations of Cf_{T} is performed by making use of the *Taguchi’s Loss Function*. The proposed method proved to be effective to correlate the limits of acceptability of geometrical deviations with the *coverage factor* for a given tolerance of the manufacturing process, thereby reducing the degree of waste.

**UNCERTAINTY IN MEASURING THE NOISE FACTOR OF CASCADE-CONNECTED LINEAR TWO-PORTS**

The paper presents the derived dependence on the total noise factor of cascade-connected linear two-ports in the conditions of energy mismatching. The method of assessing the uncertainty in measuring this factor, which takes into account propagation of standard partial uncertainties of the measurement of the set of four noise parameters, disposable power gains and input and output impedance of particular two-ports, is determined. The uncertainty analysis takes into account the correlation among these parameters. A strict dependence between the mismatching stages of two-ports in the cascade and the uncertainty in measuring the total noise factor is shown. Sensitivity coefficients determining the participation of particular standard partial uncertainties are defined. The results of the analyses and simulations of particular uncertainties components, which were carried out for a typical communications receiver, are presented.

**Uncertainty in Measuring the Power Spectrum Density of a Random Signal**

The method to assess uncertainty in measuring the power spectrum density of a random waveform is presented. Then, the evaluation of assessing uncertainty of power spectrum density is carried out. It takes into account propagation of uncertainties associated with each sample recording in the algorithm of digital signal processing and an error of the estimator bias resulting from a mathematical model of the measured value. The dependences for uncertainties in measuring the power spectrum density of a random waveform are introduced.

Page 787 of 822 Results 7861 - 7870 of 8218