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Development of a Pressure Measuring Unit Based on a Thermal Conductivity Gauge and a Low-Cost Embedded Solution for Mid-Range Vacuum Applications

Abstract

This study presents the development of a pressure measuring unit based on a Pirani gauge and a dedicated embedded system, incorporating a simple, low-cost practical solution for significantly reducing the various measurement altering factors, such as drifts, offsets and set point drifts. This is achieved by eliminating the conventional differential analogue signal processing stage and replacing it with a high resolution analog to digital converter. Therefore the goal was to minimize the number of the electronic components whose operation is influenced by variations in ambient temperature. The main topics discussed in the paper include the presentation of the measuring circuit’s configuration, the development of a low-cost embedded system, the calibration method and the solution implemented for eliminating the platforms limitation regarding the precision of the different mathematical calculations.

Open access
Electron Percolation In Copper Infiltrated Carbon

Abstract

The work describes the dependence of the electrical conductivity of carbon materials infiltrated with copper in a vacuum-pressure autoclave on copper concentration and on the effective pore radius of the carbon skeleton. In comparison with non-infiltrated material the electrical conductivity of copper infiltrated composite increased almost 500 times. If the composite contained less than 7.2 vol% of Cu, a linear dependence of the electrical conductivity upon cupper content was observed. If infiltrated carbon contained more than 7.2 vol% of Cu, the dependence was nonlinear – the curve could be described by a power formula (xxc)t. This is a typical formula describing the electron percolation process in regions containing higher Cu fraction than the critical one. The maximum measured electrical conductivity was 396 × 104 Ω−1 m−1 for copper concentration 27.6 vol%. Experiments and analysis of the electrical conductivity showed that electron percolation occurred in carbon materials infiltrated by copper when the copper volume exceeded the critical concentration. The analysis also showed a sharp increase of electrical conductivity in composites with copper concentration higher than the threshold, where the effective radius of carbon skeleton pores decreased to 350 nanometres.

Open access
Preanalytical Nonconformity Management Regarding Primary Tube Mixing in Brazil

Summary

Background: The multifaceted clinical laboratory process is divided in three essential phases: the preanalytical, analytical and postanalytical phase. Problems emerging from the preanalytical phase are responsible for more than 60% of laboratory errors. This report is aimed at highlighting and discussing nonconformity (e.g., nonstandardized procedures) in primary blood tube mixing immediately after blood collection by venipuncture with evacuated tube systems.

Methods: From January 2015 to December 2015, fifty different laboratory quality managers from Brazil were contacted to request their internal audit reports on nonconformity regarding primary blood tube mixing immediately after blood collection by venipuncture performed using evacuated tube systems.

Results and Conclusions: A minority of internal audits (i.e., 4%) concluded that evacuated blood tubes were not accurately mixed after collection, whereas more than half of them reported that evacuated blood tubes were vigorously mixed immediately after collection, thus magnifying the risk of producing spurious hemolysis. Despite the vast majority of centers declaring that evacuated blood tubes were mixed gently and carefully, the overall number of inversions was found to be different from that recommended by the manufacturer. Since the turbulence generated by the standard vacuum pressure inside the primary evacuated tubes seems to be sufficient for providing solubilization, mixing and stabilization between additives and blood during venipuncture, avoidance of primary tube mixing probably does not introduce a major bias in tests results and may not be considered a nonconformity during audits for accreditation.

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Effect of fabrication processes on mechanical properties of glass fiber reinforced polymer composites for 49 meter (160 foot) recreational yachts

Abstract

Polymer composite materialsoffer high strength and stiffness to weight ratio, corrosion resistance, and total life cost reductions that appeal to the marine industry. The advantages of composite construction have led to their incorporation in U.S. yacht hull structures over 46 meters (150 feet) in length. In order to construct even larger hull structures, higher quality composites with a lower cost production techniques need to be developed. In this study, the effect of composite hull fabrication processes on mechanical properties of glass fiber reinforced plastic(GFRP) composites is presented. Fabrication techniques used in this study are hand lay-up (HL), vacuum infusion (VI), and hybrid (HL+VI) processes. Mechanical property testing includes: tensile, compressive, and ignition loss sample analysis. Results demonstrate that the vacuum pressure implemented during composite fabrication has an effect on mechanical properties. The VI processed GFRP yields improved mechanical properties in tension/compression strengths and tensile modulus. The hybrid GFRP composites, however, failed in a sequential manor, due to dissimilar failure modes in the HL and VI processed sides. Fractography analysis was conducted to validate the mechanical property testing results

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Assessment of Sowing Quality of Radish Seeds with Working Unit of Pneumatic Seeder

8309017049. Gaikwad, B.B., Sirohi, N.P.S. (2008). Design of a low-cost pneumatic seeder for nursery plug trays. Biosystems Engineering , 99, 322-329. International standard ISO 7256/1-1984 (E). (1984). Sowing equipment – test methods Part 1: Single seed drills. Karayel, D., Barut, Z.B., Özmerzi, A. (2004). Mathematical Modelling of Vacuum Pressure on a Precision Seeder. Biosystems Engineering, 4, 437-444. Kaur, T., Kumar, D. (2013): Design and development of calibration unit for precision planter. International Journal of Computer Science

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Osmotic Dehydration of Apples Under Reduced Pressure Conditions

: effect of vacuum pressure and syrup concentration. Journal of Food Engineering, 57 , 305-314. Pasławska, M., Jałoszyński, K., Stępień, B., Surma, M. (2013). Mikrofalowo-próżniowe odwadnianie drożdży gorzelniczych. Agricultural Engineering, 4 (147), 249-258. Polish Norm PN-A-75101-03. (1990). Przetwory owocowe i warzywne. Przygotowanie próbek i metody badań fizykochemicznych. Oznaczanie zawartości suchej masy metodą wagową. In Polish. Rahman, M.S. (2001). Toward prediction of porosity in foods during drying: A brief review. Drying Techology , 19

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An alternative and indirect statistical modeling method for viscosity estimation and its experimental validation for low styrene content polyester resin

. Brouwer, W.D., van Herpt, E.C.F.C. & Labordus, M. (2003). Vacuum injection moulding for large Applications, Compos 34(6), 551-558. DOI: 10.1016/S1359-835X(03)00060-5. 5. Kedari, V.R., Farah, B.I. & Hsiao, K.T. (2011). Effects of vacuum pressure, inlet pressure, and mold temperature on the void content, volume fraction of polyester/e-glass fiber composites manufactured with VARTM process, J. Compos. Mater. 45, 2727-2742. DOI: 10.1177/0021998311415442. 6. Nawaz, A., Islam, B., Akhtar, R., Alamgir, K. & Noor, S. (2015). Failure of polyester

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Effect of electron beam injection on boron redistribution in silicon and oxide layer

, cleaned in an ultrasonic cleaner and dried in an oven. The SiO 2 layer was obtained on the polished side through thermal oxidation. The experiment was performed in a tubular resistance furnace at 1000 °C for 1 h with continuous oxygen gas flow. Then, the samples with homogenous oxide layer were subjected to EBI in an electron beam melting furnace which operated at a vacuum pressure lower than 5 × 10 −2 Pa and a 30 keV electron beam. One sample with oxide layer was subjected to EBI at 20 mA for 1 h and the other sample for 2 h. The wafer without oxide layer was

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Etching and ellipsometry studies on CL-VPE grown GaN epilayer

water to stop further etching. The GaN layers were cut in samples of 5 mm × 5 mm and were used for irradiation. Before irradiation the layers were etched with dilute HCl to remove surface oxides. 80 MeV silicon ion irradiation has been carried out on GaN epilayers at room temperature using 16-MV Pelletron Tandem Accelerator (NSC) under a background vacuum pressure of 400 Pa at various doses ranging from 1 × 10 11 cm −2 to 1 × 10 14 cm −2 . In order to find the effect of ion fluences on the refractive indices, thickness and extinction coefficient of the GaN layers

Open access
Strength and Deformation of Sand-Tire Rubber Mixtures (STRM): An Experimental Study

mold to produce a reasonably uniform, non-segregated mixture. After mixing the appropriate amount of dry sand and tire rubber, specimens were constructed carefully using the dry deposition method in six layers. Every layer was tamped using a metal rod tamper providing almost relative density of 80%. Tests have been performed based on ASTM D7181–11. After the sample had been set up in the cell with vacuum pressure (25 kPa), the inner and outer chambers were filled with de-aired water and the saturation process was carried out by applying different values of back

Open access