Structural-&-Phase Condition and the Damageability of the Welded Joints of Steam Pipelines at Thermal Power Plants

The authors studied the interrelation between the type of structure and the damage rate of the welded joints of steam pipelines made of the heat-resistant pearlitic steels that were operated for a long time, i.e. more than 270 thousand hours in the conditions of creepage and low-cycle fatigue. The purpose of this research was to establish the interrelation between the structural-&-phase condition of the metal used for welded joints of the elements of steam systems and their damageability rate for the service life of welded joints exceeding 270 thousand hours. During the studies, the methods of optical and electron microscopy were used according to the requirements of the guideline documentation and also the methods that are used for the determination of mechanical properties. The level of their reliability has been substantiated and the residual life has been determined. To impart functional performances to welded joints we used well-known methods that were appropriately emended according to the structural changes of above joints. Such changes condition the conversion of the original structure of welded joints into the ferrite-carbide mixture. The availability of the conversion process of the initial structure on the thermal action zone sections (TAZ) of welded joints has essential distinctions due to a different disposition of metal to its own damageability. On the whole, the welded joints are damaged more intensively in comparison to the basic metal of steam pipelines. The analysis of the structural state of welded joints in the steam pipelines of thermal power plants as for the extension of their service life results in a considerable economic effect. Understanding the fact that the metal deterioration in welded joints adheres mainly to the fragile mechanism we managed to establish the level of their damageability that demands the renewal of damaged welded joints. We believe that the damageability level of welded joints that tots up to 0.25 or 0.35 of the volume of their TAZ section should be considered as critical for the service life exceeding 270 thousand hours. The damaged welded joints should be renewed throughout the time period of 15 to 20 thousand hours as soon as the specified damageability level is attained.

In silico Evaluation of Cucurbit[6]uril as a Potential Detector for Cocaine and Its Adulterants Lidocaine, Caffeine, and Procaine

Illicit drugs and their trafficking require worldwide efforts in investigation, detection, and control. Colorimetric tests are often applied to identify drugs. Cocaine has some well-known adulterants that can provide a false positive response. Cucurbit[6]uril (CB[6]) has been suggested as a potential detector for cocaine and other illicit drugs. This work uses in silico methods to evaluate the use of CB[6] to detect cocaine and these interfering substances. More specifically, this work analyzes different possibilities of CB[6] complexation with cocaine, lidocaine, caffeine, and procaine and compares the results achieved for cocaine and its adulterants. Different methodologies were employed: quantum chemistry was investigated through DFT B3LYP/TZVP (density functional theory-Becke, three-parameter, Lee-Yang-Parr with triple zeta valence plus polarization basis set) and the semi-empirical methods Austin model 1 (AM1), parametric methods 3, 6, and 7 (PM3, PM6, PM7), and Recife model 1 (RM1). We used these methodologies intending to compare the reasonability and reproducibility of the results in the gas phase condition. Solvent influence was studied by molecular dynamics (MD) simulations. Results showed that CB[6] does not bind to these substances, as judged from the positive values of binding free energy obtained with all methods. DFT and MD were the most reliable methods whereas semiempirical ones were not reproductible in describing these systems. Results also showed that interactions are not specific, so CB[6] does not provide a good response for cocaine detection.

Peculiarities of crystal structure and superfine interactions in alloys Ti-Co-Sn

Alloys with the general formula TiCo2-хSn were produced by way of sintering primary components – pure metals in an argon atmosphere. The alloys were homogenized by annealing in the evacuated quartz vessel at T=1070 K during 500 h. X-ray diffraction analysis confirmed single-phase condition of all samples. Nuclear gamma resonance (NGR) analysis was made at T=295 and 80 K using radiation source BaSn119Sn. It was established, that Sn atoms in samples with x=0.6 and 1.0 are in two crystallographic positions, pyramids (1) and tetrahedrons (2) to which isomer shifts correspond (relative to SnO2 1.52-1.65 mm/s for Sn(1) and 2.99 mm/s for Sn(2). Zeeman splitting for Sn(1) in TiCo2Sn takes place at T=295 and 80 K, and for compositions with x=0.3-1.0 at T=80 K only. For Sn(2) it is noted only in alloy TiCoSn at T=80 K. The conclusion has been made on the reason of formation of effective magnetic fields on non-magnetic tin atoms nuclei.

Effect of the Ti6Al4V Alloy Track Trajectories on Mechanical Properties in Direct Metal Deposition

The TiAl6V4 alloy is widely used in selective laser melting and direct laser melting. In turn, works devoted to the issue of how the track stacking scheme affects the value of mechanical properties is not enough. The influence of the Ti6Al4V alloy track trajectories on the microstructure and mechanical properties during direct laser deposition is studied in this article for the first time. The results were obtained on the influence of «parallel» and «perpendicular» technique of laying tracks in direct laser synthesis. All studied samples have a microstructure typical of the hardened two-phase condition titanium. Here, it is shown that the method of laying tracks and the direction of load application during compression testing relative to the location of the tracks leads to a change in the ultimate strength of the Ti-6Al-4V alloy from 1794 to 1910 MPa. The plasticity of the Ti-6Al-4V alloy obtained by direct laser alloying can vary from 21.3 to 33.0% depending on the direction of laying the tracks and the direction of the compression test. The hardness of alloys varies in the range from 409 to 511 HV and depends on the method of laying the tracks and the direction of hardness measurements.

Epileptic Spike Detection by Using a Linear-Phase Convolutional Neural Network

To cope with the lack of highly skilled professionals, machine leaning with proper signal techniques is a key to establishing automated diagnostic-aid technologies to conduct epileptic electroencephalogram (EEG) testing. In particular, frequency filtering with appropriate passbands is essential to enhance biomarkers—such as epileptic spike waves—that are noted in the EEG. This paper introduces a novel class of convolutional neural networks (CNNs) having a bank of linear-phase finite impulse response filters at the first layer. These may behave as bandpass filters that extract biomarkers without destroying waveforms because of linear-phase condition. The proposed CNNs were trained with a large amount of clinical EEG data, including 15,899 epileptic spike waveforms recorded from 50 patients. These have been labeled by specialists. Experimental results show that the trained data-driven filter bank with supervised learning is dyadic like discrete wavelet transform. Moreover, the area under the curve achieved above 0.9 in most cases.

Numerical Calculation of Energy Performance and Transient Characteristics of Centrifugal Pump under Gas-Liquid Two-Phase Condition

The unstable operation of a centrifugal pump under the gas-liquid two-phase condition seriously affects its performance and reliability. In order to study the gas phase distribution and the unsteady force in an impeller, based on the Euler-Euler heterogeneous flow model, the steady and unsteady numerical calculations of the gas-liquid two-phase full flow field in a centrifugal pump was carried out, and the simulation results were compared with the test data. The results show that the test results are in good agreement with the simulation data, which proves the accuracy of the numerical calculation method. The energy performance curve of the model pump decreases with the increase of the gas content, which illustrates a serious impact on the performance under the part-load operating condition. The results reveal that the high-efficiency-operating range become narrow, as the gas content increases. The gas phase is mainly distributed on the suction surface of the impeller blades. When the gas content reaches a certain value, the gas phase separation occurs. As the inlet gas content increases, the radial force on the impeller blades decreases. The pattern of the pressure pulsation is similar to that under pure water and low gas content conditions, and the number of peaks during the pulsation is equal to the number of the impeller blades. After the gas content reaches a certain value, the pressure fluctuates disorderly and the magnitude and the direction of radial force change frequently, which are detrimental to the operation stability of the pump. The intensity of the pressure pulsations in the impeller flow channel continues to increase in the direction of the flow under pure water conditions. The pressure pulsation intensities at the blade inlet and the volute tongue become more severe with the increase of the gas content.

Extracting and determining components in the carotenoids colorant from pumpkin (Cucurpita pepo)

In this paper, the extraction of carotenoids colorants from three types of pumpkin (Vam Rang (C. maxima), ho lo (C. moschata) and Japan pumpkin (Delica)) were investigated to scale up. With suitable conditions, the pumpkin powder should be extracted with alcohol 96o with a solvent / material ratio of 12/1 mL/g at 50°C for 60 minutes. The content of carotenoids (7,5- 8 mg/mL) and the extraction efficiency of the color extract (88,37 mg/g) of ho lo pumpkin was the highest. The carotenoid concentration and extraction efficiency were determined by UV/Visible spectroscopy (432, 444 and 468 nm), and high performance liquid chromatography (the mobile phase condition isopropanol/MeOH:2/98, 450 nm. The results of the two methods were also suitable for each other. The results showed that the complex carotenoids were composition of 3 types compounds. In addition, more research is needed to enhance the durability of carotenoids.

A SVM-3D Based Encoderless Control of a Fault-Tolerant PMSM Drive

This paper exhibits a novel technique to obtain an encoderless speed control of a permanent magnet synchronous motor (PMSM) in the case of a loss of one phase. The importance of this work is that it presents solutions in order to maintain the operation of the system in various conditions. This will increase the reliability of the whole drive system to meet the safety issues required in some applications. To achieve that, a fault-tolerant inverter modulated through a 3-dimension space vector pulse width modulation technique (3D-SVPWM) is used. Besides that, an algorithm to obtain the exact position of the saturation saliency in the case of a loss of one phase is introduced to achieve a closed-loop field-oriented encoderless speed control and to further enhance the reliability of the whole drive system. This algorithm is based on measuring the transient stator current responses of the motor due to the insulated-gate bipolar transistors (IGBTs) switching actions. Then according to the operating condition (normal or a loss of one phase), the saliency position signals are constructed from the dynamic current responses. Simulation results are provided to demonstrate the effectiveness of the saliency tracking technique under normal and under a loss of one phase conditions. Moreover, the results verify the maximum reliability for the whole drive system that is achieved in this work through a continuous operation of the drive system under a loss of one phase condition and under encoderless speed control.

Mechanical Property Association of Dual Phase and Austempered AISI 4140 Normalized Steel

The present investigation intended to analyse the mechanical properties of medium carbon low alloy steel (AISI 4140) under dual phase heat treatment condition. Formation of dual phase, ferrite and martensite (F+M) from normalized condition followed by heating in the intercritical temperature range to form different volume fractions of ferrite and martensite alters tensile, hardness and impact strength of medium carbon steel. Effect of alloying elements in dual phase treatment will change the mechanical properties. Tensile strength and hardness of austempered steel shows higher value followed by dual phase condition. Ductility of normalized shows better as compared to as bought and dual phase, but austempered shows almost similar to normalized result. Impact strength of the austempered is excellent followed by dual phase condition. Heat treated specimen microstructures reveal the different phase’s present.