Numerical Simulations Based on a Meshfree Method for Nickel-Steel Welded Joint Manufactured by Micro-Jet Cooling

The article presents a numerical–experimental approach to the weldability and mechanical resistance of the joint of Alloy 59 (2.4605, nickel-chromium-molybdenum) and S355J2W (1.8965) structural steel manufactured by the MIG process with the use of micro-jet cooling. This research was considered because the standard MIG process does not guarantee the procurement of a mixed hard-rusting structural steel superalloy weld of a repeatable and acceptable quality. Welds made through the classic MIG process express cracks that result from their unfavorable metallographic microstructure, while the joint supported by micro-jet cooling does not reflect any cracks and has a high strength with good flexibility. This was achieved by the application of helium for cooling. The joining technology was also considered in the numerical stage, represented by calculations in situ. For this purpose, the fundamental solution method (FSM) for the simulation of heat transfer during the process of welding with micro-jet cooling was implemented according to the initial boundary value problem (IBVP). The problem was solved employing the method of combining the finite difference method, Picard iterations, approximation by the radial basis function, and the fundamental solution method so as to solve the IVBP. The proposed method was validated by the data and results obtained during in situ experiments. The numerical approach enabled us to obtain variations in the temperature distribution values in HAZ with its different dimensional variants, ranging between 600 °C and 1400 °C.     

An Investigation of the Thermal Transitions and Physical Properties of Semiconducting PDPP4T:PDBPyBT Blend Films

This work focuses on the study of thermal and physical properties of thin polymer films based on mixtures of semiconductor polymers. The materials selected for research were poly [2,5-bis(2-octyldodecyl)-pyrrolo [3,4-c]pyrrole-1,4(2H,5H)-dione-3,6-diyl)-alt-(2,2′;5′,2″;5″,2′′′-quater-thiophen-5,5′′′-diyl)]—PDPP4T, a p-type semiconducting polymer, and poly(2,5-bis(2-octyldodecyl)-3,6-di(pyridin-2-yl)-pyrrolo [3,4-c]pyrrole-1,4(2H,5H)-dione-alt-2,2′-bithiophene)—PDBPyBT, a high-mobility n-type polymer. The article describes the influence of the mutual participation of materials on the structure, physical properties and thermal transitions of PDPP4T:PDBPyBT blends. Here, for the first time, we demonstrate the phase diagram for PDPP4T:PDBPyBT blend films, constructed on the basis of variable-temperature spectroscopic ellipsometry and differential scanning calorimetry. Both techniques are complementary to each other, and the obtained results overlap to a large extent. Our research shows that these polymers can be mixed in various proportions to form single-phase mixtures with several thermal transitions, three of which with the lowest characteristic temperatures can be identified as glass transitions. In addition, the RMS roughness value of the PDPP4T:PDBPyBT blended films was lower than that of the pure materials.     

Effects of Early versus Standard Central Line Removal on the Growth of Preterm Infants with Very Low Birth Weight: A Non-Inferiority,Randomized Clinical Trial

Very preterm infants are usually supported by parenteral nutrition delivered through central lines (CLs) while progressing with enteral intake, although the optimal time point for their removal is unclear. This study evaluated the impact of the CL discontinuation time on the short-term growth outcomes of preterm infants. A non-inferiority, parallel-group, randomized controlled trial was conducted in four neonatal intensive care units in Poland. Preterm infants with very low birth weight (VLBW) without congenital abnormalities were eligible. Patients were allocated to discontinue central access at an enteral feeding volume of 100 mL/kg/day (intervention group) or 140 mL/kg/day (control group). The study’s primary outcome was weight at 36 weeks’ postmenstrual age, with a non-inferiority margin of −210 g. Overall, 211 patients were allocated to the intervention or control groups between January 2019 and February 2021, of which 101 and 100 were eligible for intention-to-treat analysis, respectively. The mean weight was 2232 g and 2200 g at 36 weeks’ postmenstrual age in the intervention and control groups, respectively. The mean between-group difference was 32 g (95% confidence interval, −68 to 132; p = 0.531), which did not cross the specified margin of non-inferiority. No intervention-related adverse events were observed. Early CL removal was non-inferior to the standard type for short-term growth outcomes in VLBW infants.     

Determination of Two-Stage Heat Treatment Parameters in Industrial Conditions in Order to Obtain a TRIP Structure in Low-Alloy Carbon Steel Wires

The research presented in this article aimed to obtain a semi-finished product in the form of TRIP wires, which in further research will be used to produce fasteners in the form of KPS-6 screws used in the construction industry. At present, the process of manufacturing this type of fastener (from wire rod to the finished product) involves two technological lines: one for carrying out the drawing process and obtaining a semi-finished product in the form of a wire with appropriate properties, and the other for the production of fasteners. Semi-finished product wires with a ferritic-perlitic structure obtained after the drawing process are the starting product for the production of fasteners, the tensile strength of which is approximately 450 MPa. In order to be able to obtain fasteners characterized by an increased level of properties in 8.8 grade, after the screw manufacturing process, heat treatment should be carried out by hardening and tempering. The new technology proposed in the article includes: a drawing wire rod with a semi-finished product diameter, two-stage heat treatment on the line for pass-through heating and cooling, ensuring the obtaining of a TRIP-type structure in drawn wires, and calibration drawing. The product of this process was a wire whose tensile strength was in the range of 700–800 MPa with a TRIP structure. Thanks to obtaining a TRIP-type structure with the assumed amount of retained austenite, we obtained wires with higher strength properties and very high plasticity in relation to wires with the same chemical composition and ferritic and perlitic structure. The research carried out in the article also allowed us to obtain, in the semi-finished product wires, a favourable relationship between the strength properties and plasticity of the material, expressed by the value of the R_e/R_m coefficient (yield strength/tensile strength) and the so-called yield ratio, which determines the material′s susceptibility to cold deformation; the smaller these coefficients, the greater the yield strength. The subsequent stages of the research will include the development of forming fasteners in the form of KPS-6 screws used in the steel construction industry with TRIP structures, with increased properties of products in the 8.8 property class, without conducting heat treatment by hardening and tempering. It is assumed that the resulting product will have an additional usable feature: preserving a certain amount of retained austenite in the structure of the finished fasteners, which will be transformed into martensite during operation, and thus affect the longevity of the fasteners.     

Polyaniline and Polyaniline-Based Materials as Sorbents in Solid-Phase Extraction Techniques

Polyaniline (PANI) is one of the best known and widely studied conducting polymers with multiple applications and unique physicochemical properties. Due to its porous structure and relatively high surface area as well as the affinity toward many analytes related to the ability to establish different types of interactions, PANI has a great potential as a sorbent in sample pretreatment before instrumental analyses. This study provides an overview of the applications of polyaniline and polyaniline composites as sorbents in sample preparation techniques based on solid-phase extraction, including conventional solid-phase extraction (SPE) and its modifications, solid-phase microextraction (SPME), dispersive solid-phase extraction (dSPE), magnetic solid-phase extraction (MSPE) and stir-bar sorptive extraction (SBSE). The utility of PANI-based sorbents in chromatography was also summarized. It has been shown that polyaniline is willingly combined with other components and PANI-based materials may be formed in a variety of shapes. Polyaniline alone and PANI-based composites were successfully applied for sample preparation before determination of various analytes, both metal ions and organic compounds, in different matrices such as environmental samples, food, human plasma, urine, and blood.     

Reductive Modification of Carbon Nitride Structure by Metals—The Influence on Structure and Photocatalytic Hydrogen Evolution

Pt, Ru, and Ir were introduced onto the surface of graphitic carbon nitride (g-C₃N₄) using the wet impregnation method. A reduction of these photocatalysts with hydrogen causes several changes, such as a significant increase in the specific surface area, a C/N atomic ratio, a number of defects in the crystalline structure of g-C₃N₄, and the contribution of nitrogen bound to the amino and imino groups. According to the X-ray photoelectron spectroscopy results, a transition layer is formed at the g-C₃N₄/metal nanoparticle interphase, which contains metal at a positive degree of oxidation bonded to nitrogen. These structural changes significantly enhanced the photocatalytic activity in the production of hydrogen through the water-splitting reaction. The activity of the platinum photocatalyst was 24 times greater than that of pristine g-C₃N₄. Moreover, the enhanced activity was attributed to significantly better separation of photogenerated electron–hole pairs on metal nanoparticles and structural distortions of g-C₃N₄.     

Evaluation of Selected Properties of Sodium Alginate-Based Hydrogel Material—Mechanical Strength, μDIC Analysis and Degradation

The search for ideal solutions for the treatment of urethral stenosis continues. This includes developing the material, design, while maintaining its optimal and desired properties. This paper presents the results of the research conducted on sodium alginate-based hydrogel material (AHM), which may be used as a material for stents dedicated to the treatment of pathologies occurring in the genitourinary system. In order to determine the selected parameters of the AHM samples, strength and degradation tests, as well as analysis of the micro changes occurring on the surface of the material using a digital image correlation (µDIC) system, were performed. This study shows that the material possessed good mechanical strength parameters, the knowledge of which is particularly important from the point of view of the stent-tissue interaction. The degradation analysis performed showed that the AHM samples degrade in an artificial urine environment, and that the degradation time mainly depends on the chemical composition of the material. The novel µDIC method performed allowed us to characterize the homogeneity of the material structure depending on the cross-linking agent used.     

Impact of Magnetization on the Evaluation of Reinforced Concrete Structures Using DC Magnetic Methods

The magnetic method is the most promising method that can be used to inspect large areas of reinforced concrete (RC) structures. Magnetization is a crucial process in this method. The paper aims to present the impact of the magnetization method on the results in the detection of reinforced bars (rebars) and the evaluation of concrete cover thickness in reinforced concrete (RC) structures. Three cases (without magnetization, same pole magnetization, and opposite pole magnetization) were considered in the experiments. Results achieved in all the methods are presented and evaluated. Two different sensing elements were used in the measurements: a magneto-optical (MO) sensor and an AMR sensor. The advantages and disadvantages of both mentioned transducers are presented and discussed in the context of a large areas inspection. The new approach involves using various magnetization methods to improve measurement results for complex structures.