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The results are presented of a bilateral comparison of pneumatic pressure measurements, carried out in the framework of EUROMET Project No. 537, between the Cesky Metrologicky Institut (CMI, Czech Republic) and the TÜBITAK-Ulusal Metroloji Enstitüsü (UME, Turkey). The measurements, in the range 15 kPa to 7 MPa, were carried out in two phases: (i) 18-24 June 1999 at the Pressure Section of the CMI in the range 15 kPa to 350 kPa; (ii) 29 June-8 July 1999 at the Pressure Section of the UME in the ranges 0.25 MPa to 1.75 MPa and 1 MPa to 7 MPa. Three different gas-operated reference standards were used. For the ranges 15 kPa to 350 kPa and 0.25 MPa to 1.75 MPa these were piston-cylinder assemblies with ceramic pistons and tungsten-carbide cylinders and nominal effective areas of 10 cm2 and 2 cm2, respectively. For the range 1 MPa to 7 MPa, a piston-cylinder assembly with tungsten-carbide piston and cylinder and a nominal effective area of 0.5 cm2 was used. The purpose of the measurements was to compare the effective areas of the Czech and Turkish primary pressure standards in gas media and gauge mode, and to confirm the agreement between the pressure scales of the two countries in the range 15 kPa to 7 MPa by application of the cross-floating method. Since the UME and the CMI are participating in different loops of EUROMET Project No. 439, a key comparison of pneumatic pressure, another important goal of this study was to establish a cross-link between the two loops.

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Through-the-Wall Imaging is an ever-expanding area in which processing time, scanning time, vertical, and horizontal resolutions have been tried to improve. In this study, several methods are investigated to obtain efficient reconstruction of through-the-wall imaging radar signals with high resolution. Microwave radar signals, which are produced in YTU Microwave Laboratory, are processed by compressive sensing (CS). B and C scanned reflection data samples collected between 1 and 7 GHz frequency band are taken randomly at 1/4, 1/2 of whole amount and reconstructed by CS method. Considering the signal structure, 10 and 20 compressible Fourier coefficients are taken through CS to analyze the difference between them. In addition, we applied synthetic aperture radar (SAR) processing, also combined with SAR-Multiple Signal Classification over raw data. Experimental performance results are given and shown in the figures with high quality.

The finite element method (FEM) was used in this study for the analysis of the strain distribution of a strain gauge pressure transducer for hydrostatic pressure measurements up to 150 MPa. The pressure transducer, which we investigated, on the basis of `thick-walled cylindrical vessel' theory has a free steel active element. Pressure is applied to the inside and both open ends of this active element. The symmetrical shape of the transducer and all the design parameters of the active element were selected in such a way as to ensure that a symmetrical stress and strain distribution was obtained even at the maximum working pressure of the transducer. The FEM analysis was conducted by investigating one half of the element in three dimensions. This paper presents the FEM output strain values for the area where the strain gauges were bonded. The validity of those values was established by comparing them with the results obtained from the strain gauge measurements. The relative difference between the two sets of values determined to be lower than 13% of the full scale. The two kinds of measuring elements were made of two different materials; AISI 4340 steel and Invar steel, which work in the hydraulic gauge pressure ranges of up to 150 and 100 MPa respectively. The transducers were calibrated using piston pressure balance. The metrological specifications of a total of eight specimens were evaluated. Although the scope of the study is only an application of the FEM, this evaluation also suggests that this type of transducer can be used with an estimated uncertainty of up to 0.1% of the full scale. However, this uncertainty can be improved by a small modification in design, to reduce the reproducibility and hysteresis errors of the device, which are the main parameters in the evaluation of the uncertainty. The results presented in this paper will be helpful for practical static pressure measurements as well as for the appropriate design of this kind of pressure transducer using the FEM.