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Raouf M.H.A.,National Institute for Standards of Egypt
Measurement: Journal of the International Measurement Confederation | Year: 2017

Resistance boxes are used for calibration of devices that measure resistance at many electrical laboratories. In this research, a new automated Resistance Box (RB) has been presented that mainly consists of three decades. They have the same design, but each has four different internal resistive elements. Each decade generates 15 different output resistance values; therefore, it is more economical and practical compared to the other usual decades, which produce only 10 values by using 10 internal resistive elements per decade. 4096 resistance values can be obtained by the all possible combinations of the new RB decades. Design, fabrication process, and characterization of the new RB are demonstrated in detail including its main specifications and advantages. Maximum relative deviation from the nominal values of the new RB steps is ±50 ppm. © 2017 Elsevier Ltd

Sadek A.M.,National Institute for Standards of Egypt
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2013

The accuracy of the thermoluminescence (TL) kinetics parameters obtained using the computerized glow curve deconvolution (CGCD) algorithm was tested. The differential equation governing the electron traffic in the one trap-one recombination (OTOR) level model was solved with almost no approximation using the Fehlberg-Runge-Kutta method. A set of simulated glow peaks was generated for a wide range of kinetics parameter values. These glow peaks were then fitted using the general-order kinetics equation. Comparisons between the kinetics parameter values of the simulated glow peaks and those obtained by the CGCD method were made. The results show that the accuracy of the different kinetics parameters obtained by the CGCD method is not the same and that it varies according to the value of the kinetics order (b). The overlapping of two glow peaks with very close maximum peak positions (Tms) results in a glow peak with unexpected values for the kinetics parameters. A set of different cases of overlapping glow peaks is also discussed. © 2013 Elsevier B.V.

Hamza G.G.,National Institute for Standards of Egypt
Mapan - Journal of Metrology Society of India | Year: 2014

Measuring the time interval (TI) with an accuracy in the picoseconds range requires having an accurate measurement system and minimizing the sources of errors contributed by the signal being measured. Trigger level timing error is one of the main sources of error that dramatically affects the measurement accuracy. In this article we study the effect of changing the trigger level on the TI measurement accuracy for sinusoidal signals, introduce a laboratory method for determining the optimum trigger level that leads to the highest measurement accuracy, and make a method validation. © 2014, Metrology Society of India.

Hamza G.G.,National Institute for Standards of Egypt
Mapan - Journal of Metrology Society of India | Year: 2014

At April 2003 there were 25 National Metrology Institutes in 25 countries that are members in the European Association of National Metrology Institutes (EURAMETs) agreed to participate in an inter-laboratory comparison for time interval measurement (TIM). The main target of this comparison, as mentioned by EURAMET, was to support the current calibration measurement capabilities for TI and to gain better understanding of the TIM. Cable delay measurement was taken as an example. The time delay of three different length coaxial cables (short, medium, and long) was measured. The majority of the laboratories used the Counter Method. There was a large span between the measurements for all cables (about 1 ns). Consequently, the measurement results that had been published at 2007 were not satisfied for the participant laboratories. In this article, we study the probable reasons for this considerable span between the different measurements for the same artifact. © 2014 Metrology Society of India.

El-Sersy A.R.,National Institute for Standards of Egypt
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2010

In this work, CR-39 track detectors have extensively been used in the determination of fast neutron fluence-to-dose factor. The registration efficiency, ε, of CR-39 detectors for fast neutrons was calculated using different theoretical approaches according to each mode of neutron interaction with the constituent atoms (H, C and O) of the detector material. The induced proton-recoiled showed the most common interaction among the others. The dependence of ε on both neutron energy and etching time was also studied. In addition, the neutron dose was calculated as a function of neutron energy in the range from 0.5 to 14MeV using the values of (dE/dX) for each recoil particle in CR-39 detector. Results showed that the values of ε were obviously affected by both neutron energy and etching time where the contribution in ε from proton recoil was the most. The contribution from carbon and oxygen recoils in dose calculation was pronounced due to their higher corresponding values of dE/dX in comparison to those from proton recoils. The present calculated fluence-to-dose factor was in agreement with that either from ICRP no. 74 or from TRS no. 285 of IAEA, which reflected the importance of using CR-39 in absolute fast neutron dosimetry. © 2010 Elsevier B.V.

Abdelsalam D.G.,National Institute for Standards of Egypt
Measurement: Journal of the International Measurement Confederation | Year: 2013

This paper presents a quantitative comparison between off-axis digital holographic microscopy (DHM) and on-axis phase-shifting interferometry (PSI) for surface micro topography measurement. The comparison has been applied on an object of a 1.34 μm nominal step height. The experimental results show that single shot, dual-wavelength, off-axis DHM surpasses on dual-wavelength, on-axis PSI in terms of accuracy and repeatability. © 2013 The Author. Published by Elsevier Ltd. All rights reserved.

Ali S.H.R.,National Institute for Standards of Egypt
Measurement Science Review | Year: 2010

This paper aims at studying the effect of the dynamic errors on surface measurements using three different types of touch trigger probes attached to a bridge-type-CMM. Unforeseeable dynamic root errors of a ductile touch trigger probing system have been characterized theoretically and experimentally as well. The results were employed in validating a developed analytical two-dimensional-model (2DM) of stylus tip to be developed to demonstrate the capability of such approaches of emphasizing the root error concept, and to evaluate the accuracy of the CMM measurements. A set of experiments was conducted; the results were analyzed in order to investigate the effect of the dynamic root errors in the light of probe scanning speed at different stylus tip radii. Variations in the mass and geometry of the stylus have their consequent effects on its inherent intrinsic dynamic characteristics that in turn would cause relevant systematic root errors in the resulting measurements. 3D bore cylindrical surface form undulations were measured by employing a probe on the trajectory of internal surface diameter for the standard reference test gauge ring. Regression analysis was applied on the results of measurement density distribution; uncertainty of measurement repeatability was then evaluated and graphically presented. The results were investigated and optimum strategic measurement parameters could thus have been derived to ensure foreseeable accurate and precise results.

Ali R.S.M.,National Institute for Standards of Egypt
Measurement: Journal of the International Measurement Confederation | Year: 2011

In this paper, a comparison is done between two different techniques in measuring the AC voltage. The first technique is the single junction thermal voltage converters (SJTVC) which consist of one thermal element (TE) which its output e.m.f. in the range of 7-12 mV and the other is the new designed thermal voltage converters which consist of a number of TEs connected in parallel, series and series/parallel to increase their output e.m.f. (becomes in the range of 35-51 mV). The effect of increasing the output e.m.f. is studied in this paper through evaluating the uncertainty budget and proved that its increase has a great effect on the accuracy and the uncertainty of the AC voltage measurement. © 2011 Elsevier Ltd. All rights reserved.

Maghraby A.,National Institute for Standards of Egypt
Radiation Protection Dosimetry | Year: 2011

During the past 50 y alanine has been considered a reference dosimetry system using electron paramagnetic resonance (EPR), especially for the high doses associated with radiation processing. Extension of alanine/EPR system applications to the lower doses associated with radiation therapy and/or radiation protection is limited by the ability to extract the dosimetric signal with minimum associated noise. The signal-averaging technique is one of the common numerical methods used for enhancing the signal-to-noise ratio, through which the accumulated repetitive scans causes the reduction of noise due to its random behaviour and the signal growth due to its persistence. However, the use of signal averaging is usually associated with some uncertainty, which is not usually considered. In this work, there is a clarification of the importance of the evaluation of uncertainty associated to the single averaged alanine spectrum. © The Author 2010. Published by Oxford University Press. All rights reserved.

Nagib N.N.,National Institute for Standards of Egypt
Optics and Laser Technology | Year: 2013

The retardance introduced by a prism-type retroreflector depends on the refractive index of the prism material corresponding to the wavelength of the incident radiation and the values of the internal reflection angles. In normal-incidence devices (the external angle of incidence i=0°), the reflection angles θ are of fixed values and the retardance varies with the refractive index n. In this work, an oblique-incidence (i≠0), 3-reflection quarterwave retroreflector is presented which provides extreme stability of the retardance over extended spectral ranges. Between n=1.59 and n=1.73, the maximum deviation of the retardance from 90° is 0.1°. The device is suitable for use with laser beams. © 2012 Elsevier Ltd. All rights reserved.

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