Estimation of laser-Doppler anemometry measuring volume displacement in cylindrical pipe flow

Laser-Doppler anemometry application in measurements of the 3-D swirl turbulent flow velocity in the cylindrical pipe, behind the axial fan, have been analysed. This paper presents a brief overview of uncertainty sources in the laser-Doppler anemometry measurements. Special attention is paid to estimation of laser-Doppler anemometry measuring volume positioning in cylindrical pipe flow due to optical aberrations, caused by the pipe wall curvature. The hypothesis, that in the central part of the pipe (r/R < 0.6) exists a small, or negligible pipe wall influence on laser- -Doppler anemometry measuring position, is investigate. The required corrections, for measurements of axial, tangential, and radial velocity components such: shift of measuring volume and its orientation are analyzed and determined for used test rig and for some other pipe geometries. [Projekat Ministarstva nauke Republike Srbije, br. TR 35046

Statistical analysis of shear strength of welds in welded fabric for civil engineering with application of new tool design

Many new requirements in the field of testing of metals, emphasize traceability and accuracy of test results as of the end goal. These requirements have hidden context with emphasis on energy efficiency too., which is initiated by mass productions and increasing market of end products based on steels for civil engineering applications. The noted above move focus on improvements of existing test methods. The key point in the verification of improvements is a statistical analysis of test results. This paper describes one such analysis, based on results obtained by application of new insert tool for testing of shear strength of welded fabric for civil engineering. This paper presents an extensive series of experimental results to verify the efficiency of the application of the new insert tool. The obtained results justify applications of a new tool insert to reduce data scatter during testing of welded fabric for civil engineering

The new tool insert design for prevention the rotation of horizontal wire during shear testing of welded fabric

Many new requirements in the field of experimental mechanics, like testing of metallic materials, emphasize traceability and accuracy of test results as the end goal. These requirements have energy efficiency context too, due to the increase of mass productions of many finished and semi-finished products based on steel metallurgy. Combined, both of the above-noted perspectives impose the need for improvements of some of the existing test methods. This paper describes one such improvement, the developing of the new insert tool for testing of shear strength of the welded fabric, for civil engineering. The developed tool allows repeated testing of welded joints sampled from the welded fabric of different dimensions without tool changes and is generally related with the procedure for the determination of shear strength properties of different sizes of wires used for welded fabric. The construction of the tool insert allows aiming high operation safety and higher accuracy of results, which is described in detail. The paper also presents experimental results and the Finite Element Analysis performed in order to verify the impact of insert tool application on the testing results. The obtained results and conclusion about the possible contributions of the developed insert tool for extensively testing of welded fabric for civil engineering are discussed

Procedures for preventing corrosion of welded joints

This paper describes the procedures for preventing corrosion of welded joints. Also, a theoretical overview of the forms of corrosion that are most prevalent in welded joints is presented. The concept of corrosion in welded joints is very pronounced in real conditions. Welded joints are inseparable joints that form an integral part of steel welded constructions. The internal energy increases during the fusion welding especially in the heat affected places around the welded joint, which become initiating spot of corrosion degradation. That is why it is of vital importance to focus on ways to increase the resistance of welded structures to the impact of corrosion

Monitoring the amount of formed solid phase in aluminum alloy under free cooling conditions

Jedan od najefikasnijih načina za buduće projektovanje, proizvodnju, analizu i optimizaciju novih procesa koji uključuju faznu promenu materijala je razvoj visokoosetljivih kvantitativnih metoda zasnovanih na detekciji temperaturnih promena tokom trajanja procesa i korelaciji tih promena sa promenama u tretiranom materijalu. U ovom radu, sekundarna legura Al-8wt%Si-3wt%Cu je formirana iz tečnog stanja u uslovima slobodnog hlađenja. Identifikovane su karakteristične temperature transformacija i formalizovan je metod za praćenje količine čvrste faze tokom procesa očvršćavanja. Iz snimljene krive hlađenja određene su vrednosti prvog izvoda i formirana je odgovarajuća referentna kriva. Površina između prvog izvoda krive hlađenja i referentne krive je korišćena za praćenje količine očvrslog dela materijala tokom procesa očvršćavanja. Dobijeni rezultati su pokazali da je predložena metoda efikasna u dobijanju podataka o količini očvrslog dela materijala u svakom trenutku procesa očvršćavanja, kao i da se mogu dalje koristiti za detekciju broja faza i mikrokonstituenata u formiranoj strukturi i eksperimentalnu potvrdu latentne toplote očvršćavanja novih materijala. Metoda praćenja količine formirane čvrste faze u uslovima slobodnog hlađenja ne zahteva posebnu pripremu uzoraka niti kompleksnu laboratorijsku opremu, pa shodno tome, u praktičnoj primeni efikasno zamenjuje standardne metode za detekciju termofizičkih osobina materijala, kao što su diferencijalna termijska analiza ili diferencijalna skenirajuća kalorimetrija.One of the most effective ways for the future design, production, analysis and optimization of new processes, involving phase change of materials, is the development of highly sensitive quantitative methods based on the detection of temperature changes during the solidification process and the correlation of these changes with changes in the treated material. In this work, the secondary Al-8wt%Si3wt%Cu alloy was formed from the liquid state under free cooling conditions. Characteristic transformation temperatures were identified and a method for monitoring the amount of solid phase during the solidification process was formalized. From the recorded cooling curve, the values of the first derivative were determined and the corresponding reference curve was formed. The area between the first derivative of the cooling curve and the reference curve was used to assess the amount of solidified part of the material during the solidification process. The obtained results showed that the proposed method is effective in obtaining data of the fraction solid at every moment of the solidifcation process, as well as that it can be further used to detect the number of phases and microconstituents in the formed structure, as well as an experimental examination of the latent heat of solidification of new materials. The method of monitoring the amount of solid phase, formed under free cooling conditions, does not require specific preparation of samples or complex laboratory equipment, and accordingly, in practical application it effectively replaces standard methods for detecting thermophysical properties of materials, such as differential thermal analysis or differential scanning calorimetry

B-Type Natriuretic Peptide as a Marker of Different Forms of Systemic Sclerosis

Background: Systemic sclerosis (SSc) is an autoimmune connective tissue disease which affects various tissues and organs, including skin, lungs, kidneys, gastrointestinal tract and cardiovascular system. Cardiac involvement is the most commonly recognized problem and a significant cause of morbidity. The brain natriuretic peptide (BNP) is a previously known marker of elevated cardiovascular risk in SSc, but the levels of BNP in various forms of SSc have not been investigated so far. Aim: The aim of our study was to evaluate the influence of SSc on the function of the right ventricle and the right atrium using the echocardiographic parameters. Moreover, we examined the levels of BNP in different forms of SSc as well as the association of disease severity with the plasma concentrations of BNP. Methods: We included 42 patients with newly diagnosed SSc and patients whose disease had been diagnosed earlier. SSc patients and non-SSc control patients were examined by using echocardiography and the concentrations of BNP were determined. Results: We analyzed differences in the parameters of right ventricle (RV) function and right atrium (RA) function between SSc patients and healthy controls. The two groups had similar distribution of gender, but SSc patients were significantly older than controls. RV wall thickness was increased in SSc patients (p lt 0.001), while right ventricular end-systolic area (RVEDA; p=0.408) and right ventricular end-diastolic area (RVEDA; p=0.368) did not differ among the examinees. In contrast, RA minor-axis dimension (p=0.001) and the tricuspid annular plane systolic excursion (TAPSE) (p=0.001) were significantly higher in SSc patients. Also, we analyzed differences in brain natriuretic peptide (BNP) concentrations between diffuse cutaneous systemic sclerosis (DSSc) and limited cutaneous systemic sclerosis (LSSc) patients. DSSc patients had significantly higher concentrations of BNP. We found that levels of BNP were in significant positive correlations with age (p=0.007), disease duration (p=0.023), C reactive protein (CRP) (p=0.032), right ventricle fractional area change (FAC) (p=0.022), pulmonary vascular resistance (PVR) and Rodnan score (p=0.019). Conclusions: Given the obtained results, the laboratory determination of BNP could be useful in differentiating different forms of systemic sclerosis as well as in predicting the severity of the disease and future cardiovascular complications

Functional Properties of Pea (Pisum sativum, L.) Protein Isolates Modified with Chymosin

In this paper, the effects of limited hydrolysis on functional properties, as well as on protein composition of laboratory-prepared pea protein isolates, were investigated. Pea protein isolates were hydrolyzed for either 15, 30 and 60 min with recombined chymosin (Maxiren). The effect of enzymatic action on solubility, emulsifying and foaming properties at different pH values (3.0; 5.0; 7.0 and 8.0) was monitored. Chymosin can be a very useful agent for improvement of functional properties of isolates. Action of this enzyme caused a low degree of hydrolysis (3.9–4.7%), but improved significantly functional properties of pea protein isolates (PPI), especially at lower pH values (3.0–5.0). At these pH values all hydrolysates had better solubility, emulsifying activity and foaming stability, while longer-treated samples (60 min) formed more stable emulsions at higher pH values (7.0, 8.0) than initial isolates. Also, regardless of pH value, all hydrolysates showed improved foaming ability. A moderate positive correlation between solubility and emulsifying activity index (EAI) (0.74) and negative correlation between solubility and foam stability (−0.60) as well as between foam stability (FS) and EAI (−0.77) were observed. Detected enhancement in functional properties was a result of partial hydrolysis of insoluble protein complexes

Overview of uncertainty sources in flow velocity vector measurement by LDA

Many sources of uncertainties are inherent in LDA practices and must be recognized to obtain good experimental results. Analysis of uncertainty, for tests that include LDA measurements of velocity vectors in wind tunnels or in cylindrical pipe swirl flows is very complex problem. An overview of the most significant uncertainty sources in the LDA measurements is presented. One of the main groups of uncertainty sources is determined by the optical components arrangement. In this paper, special attention is paid to estimation of laser-Doppler anemometry uncertainty of measurement volume positioning in test devices caused by the wind and water tunnel windows thickness, or by the pipe wall curvature (without using refractive index matching). The required corrections, for measurements of velocity components such: shift of measuring volume and its orientation are analyzed and determined for VTI wind and water tunnels and for some very often used geometry of cylindrical pipes in industry. Depending on different experimental conditions, some of these sources of uncertainty may be neglected, but generally, it is necessary to take into account all of them in all optical methods, as LDA, PDA, PIV and so on

Overview of uncertainty sources in flow velocity vector measurement by LDA

Many sources of uncertainties are inherent in LDA practices and must be recognized to obtain good experimental results. Analysis of uncertainty, for tests that include LDA measurements of velocity vectors in wind tunnels or in cylindrical pipe swirl flows is very complex problem. An overview of the most significant uncertainty sources in the LDA measurements is presented. One of the main groups of uncertainty sources is determined by the optical components arrangement. In this paper, special attention is paid to estimation of laser-Doppler anemometry uncertainty of measurement volume positioning in test devices caused by the wind and water tunnel windows thickness, or by the pipe wall curvature (without using refractive index matching). The required corrections, for measurements of velocity components such: shift of measuring volume and its orientation are analyzed and determined for VTI wind and water tunnels and for some very often used geometry of cylindrical pipes in industry. Depending on different experimental conditions, some of these sources of uncertainty may be neglected, but generally, it is necessary to take into account all of them in all optical methods, as LDA, PDA, PIV and so on

Modelling of chemical surface acoustic wave sensors and comparative analysis of new sensing materials

Comparative analysis of different, new gas sensing materials in surface acoustic wave chemical sensors is presented. Different gas sensing materials as polyaniline (PANI), Teflon AF 2400, polyisobutylene (PIB), polyepichlorohydrin (PECH) are considered. They are chosen according to the type of gas to be detected and the desired accuracy: Teflon AF 2400 thin film for the detection of CO2, PANI nanocomposites film that belongs to the group of conductive polymers for the detection of CO, NO2 and phosgene (COCl2), and PECH and PIB for the detection of dichloromethane (CH2Cl2, DCM). In the analysis, the simple and useful method of the complete analyses of gas chemical sensors is used. The method is based on the electrical equivalent circuit of the surface acoustic wave sensor. The method is very efficient and can be used for the optimal design of CO2 sensors. The results are compared with those presented in public literature and good agreement is obtained, demonstrating the validity of modelling