Diverse Angles Research Articles

Depositional patterns of slowly plugging neck cutoffs from core analysis and estimates of bedload transport, White River, Arkansas

AbstractMeander cutoffs and oxbow lakes are very common features of fluvial landscapes that add complexity and diversity to floodplain alluvial architecture and riverine habitats. Following initial cutoff, sediment accumulates within the entrance and exit of the original bend forming plugs that eventually disconnect the abandoned bend from the main channel. While studies have examined the sedimentology of these plugs once they have fully disconnected from the abandoned bend, fewer studies have detailed the sedimentological processes occurring during the early stages following cutoff initiation. Furthermore, recent studies have highlighted the importance that planform geometry plays in the evolution of neck cutoffs. This study examines the spatial depositional patterns of two neck cutoffs on the White River in central Arkansas, USA, that remain hydrologically connected to the main channel, providing a unique opportunity to research sedimentological processes before disconnection of the abandoned bend. Sediment cores were collected in key locations of each cutoff, including the entrance and exit of the abandoned bends, abandoned bend apices, and newly developed cutoff bars in the downstream channel. The cores were logged and interpreted and grain‐size analyses were performed. In addition to sediment cores, repeat high‐resolution multibeam echo sounding surveys were conducted roughly four hours apart to estimate bedload transport rates and patterns of bedload routing through each cutoff. Results from this research are different from previous studies. Sediment core results show a pattern of deposition typically associated with lower diversion angle chute cutoffs instead of higher diversion angle neck cutoffs. Previous research has indicated that plugging of abandoned bends drives disconnection from the active channel; however, this research shows that disconnection is more associated with the prevention of sediment from being delivered to the abandoned bends due to flow being pulled away from the abandoned bends and the evolving channel morphology.

Цикл «новых левых» в недавней истории Аргентины

This paper aims at outlining the main processes that, in Argentina’s recent past, may enable us to understand the emergence, development and eventual defeat of the social protest movement and the political radicalization of the period 1960-70s.Here, as in previous papers, we resort to the concept of new left toname the movement that, though heterogeneous and lacking a unified direction, became a major unit in deeds, for multiple actors coming the most diverse angles coincided in opposing the vicious political regime and the social order it supported. Consequently, we shall try to reinstate the presence of such wide range of actors: their projects, objectives and speeches. Some critical circumstances shall be detailed and processes through which protests gradually amalgamated will be shown. Such extended politicization provided the frame for quite radical moves ranging from contracultural initiatives and the classism in the workers’ movement to the actual action of guerrilla groups. Through the dynamics of the events themselves we shall locate the peak moments as well as those which paved the way for their closure and eventual defeat in 1976.

Numerical Simulation and Computational Flow Characterization Analyses of Centrifugal Pump Operating as Turbine

Using a pump in reverse mode as a hydraulic turbine remains an alternative for hydropower generation in meeting energy needs, especially for the provision of electricity to remote and rural settlements. The primary challenge with small hydroelectric systems is attributed to the high price of smaller size hydraulic turbines. A specific commercial pump model, with a flow rate of 12.5 m3/h, head 32 m, pressure side diameter of 50 mm, impeller out, and inlet diameters of 160 mm and 6 mm, respectively, was chosen for this research. This research aimed to investigate a pump’s flow characteristics as a turbine to help select a suitable pump to be used as a turbine for micro- or small hydropower construction. Numerical methodologies have been adopted to contribute to the thoughtful knowledge of pressure and velocity distribution in the pump turbine performance. In this study, the unsteady flow relations amongst the rotating impeller and stationary volute of the centrifugal pump made up four blades and four splitters. Intermittent simulation results of pressure and velocity flow characteristics were studied considering diverse impeller suction angles. The study was conducted by considering a wide range of rotational speeds starting from 750 rpm to 3250 rpm. From the results, it was found that PAT operation was improved when operated at low speeds compared to high-speed operation. Thus, speeds between 1500 rpm and 2000 rpm were suitable for PAT performance. This research helps to realize the unsteady flow physiognomies, which provide information for future research on PAT. This study makes useful facts available which could be helpful for the pump turbine development. Future studies should focus on cost analysis and emission generation in energy generation.

Hydrogen Adsorption on Defective Nitrogen-Doped Carbon Nanotubes Explained via Machine Learning Augmented DFT Calculations and Game-Theoretic Feature Attributions

Complex machine learning (ML) models applied within computational chemistry and materials science tend to be seen as black boxes, yielding property predictions given some input features. While the purpose of ML methods is often to circumvent computationally expensive first-principles calculations, the fact that the inner workings of the models are not understood conceals chemical insight and knowledge regarding the underlying data and physical correlations within it. Knowing what a model is learning from the data and how outputs are formed is also useful in facilitating the justification and wider adoption of ML solutions. Here, we present an important contribution in this direction by exploring and explaining the hydrogen adsorption properties of defective nitrogen-doped carbon nanotubes (NCNTs) through density functional theory simulations and machine learning-based data analysis. As the main highlight, we demonstrate the application of a recent game-theoretic approach to deconvolute and interrogate the trained ML models, revealing how various structural, chemical, and electronic features contribute toward the hydrogen affinities of roughly 6500 different NCNT adsorption sites. The employed method of Shapley additive explanations (SHAP) attributes locally accurate importances to the investigated features, unraveling high spin polarization, narrow highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO–LUMO) gap, small dopant–adsorption site separation, and diverse angle and coordination effects as particularly impactful for increasing hydrogen adsorption strengths. The SHAP method is shown capable of promoting a deep understanding of complex feature–activity relationships, facilitating research efforts such as rational catalyst design for energy conversion applications.

A Review Article on Pharmacologic Evaluation, Botanical report and Calming uses of Dioscorea bulbifera Linn. and Dioscorea pentaphylla Linn.

The present-day investigation focuses on the Pharmacologic revision of the climbers of D. bulbifera L &. D. pentaphylla L. (Dioscoreaceae). Climbers have been deliberate from diverse angles of morphological and, residue scrutiny, and extractive standards. Morphological analysis discovered nature, dimensions, aroma and flavour of tubers. The genus Dioscorea have its place to the family Dioscoreaceae, universally recognized as yam, consist of nearly 600 sps. Scattered all over the earth realm, but customarily in steamy section. Most sps. encompass steroid saponins and correspondingly sapogenins, such as diosgenin, which is preparatory quantifiable for blend of various steroidal hormones castoff as anti-inflammatory, androgenic estrogenic and contraceptive drugs. Associates of the genre Dioscorea are one of ancient tuber crop cultured or garnered from uninhabited in steamy constituency all over earth realm and set up one of the key food element for various indigenous groups. Genus is reflected to be amid the most primeval angiosperms and was recognized to occur and broaden the horizons nearly 75 M. Yrs. past in segments of southern celestial-sphere at the termination of the cretaceous period

Gottlieb Polynomials and Their q-Extensions

Since Gottlieb introduced and investigated the so-called Gottlieb polynomials in 1938, which are discrete orthogonal polynomials, many researchers have investigated these polynomials from diverse angles. In this paper, we aimed to investigate the q-extensions of these polynomials to provide certain q-generating functions for three sequences associated with a finite power series whose coefficients are products of the known q-extended multivariable and multiparameter Gottlieb polynomials and another non-vanishing multivariable function. Furthermore, numerous possible particular cases of our main identities are considered. Finally, we return to Khan and Asif’s q-Gottlieb polynomials to highlight certain connections with several other known q-polynomials, and provide its q-integral representation. Furthermore, we conclude this paper by disclosing our future investigation plan.

Transcriptome and metabolite analysis related to branch development in two genotypes of Eucalyptus urophylla.

Branching in long-lived plants can cause scarring at the base and affect wood density, which greatly inhibits wood yield and quality. Eucalyptus urophylla is one of the most important commercial forest tree species in South China, with diverse branch number and branch angles under different genetic backgrounds. However, the main elements and regulatory mechanisms associated with different branching traits in E. urophylla remain unclear. To identify the factors that may influence branching, the transcriptome and metabolome were performed on the shoot apex (SA), lateral shoot apex (LSA), and stem segment at the 5th axillary bud from the shoot apex (S1) in lines ZQUC14 (A) and LDUD26 (B), with A exhibiting a smaller Ba than B. A total of 307.3 million high-quality clean reads and nine hormones were identified from six libraries. Several differentially expressed regulatory factors were identified between the two genotypes of E. urophylla. The Kyoto Encyclopedia of Genes and Genomes pathways were enriched in plant hormone signal transduction, plant hormone biosynthesis and their transport pathways. Furthermore, gene expression pattern analysis identified genes that were significantly downregulated or upregulated in S1 relative to the SA and LSA segments, and the plant hormone signal transduction pathway was constructed to explain branching development. This study clarified the main plant hormones and genes underlying branch numbers and angles of E. urophylla, confirmed that ABA and SA could promote a larger branch angle and smaller branch number, while IAA has an opposite function. Numbers of key candidate genes involved in plant hormone signal transduction were found in the positive regulation of branch formation. These novel findings should aid molecular breeding of branching in Eucalyptus.

Devising a model of the airflow with dust particles in the intake system of a vehicle’s internal combustion engine

This paper considers the mechanism of malfunction of internal combustion engines that implies the accelerated local wear of parts in individual cylinders as a result of uneven distribution of dust particles that pass through the air filter in the intake system. In order to acquire quantitative data on the effect of the structure of the intake system on the redistribution of dust in engine cylinders, the two-phase flow of air with dust particles in the standard elements of the intake system was mathematically modeled. ANSYS software package was used to solve the problem. A simulation technique was devised in which the airflow was first calculated to determine the boundary conditions for dust, after which the flow of air with particles was calculated. The calculations were carried out in a range of air velocities of 5‒20 m/s in branching channels with diversion angles of 45°, 90°, and 135° for the most characteristic particle sizes of 5‒30 µm. It has been estimated that dust particles deviate from the air streamlines by inertia and can slip through the lateral drain the stronger the larger particle size, diversion angle, and velocity of air. The comparison of the simulation results with experimental data confirmed that in the intake system of some engines, due to uneven particle distribution, there is local abrasive wear in one or more cylinders, which can significantly reduce the resource. This paper shows the need to take into consideration the centrifugation and redistribution of dust in the intake systems during the design, modernization, expert studies to determine the causes of faults associated with faulty operating conditions, as well as to clarify the regulations for the maintenance of existing engines.

Multifunctional sensing activities toward heavy metals of three luminescent complexes: Effect of N-donor coligands and sensing medium

The functional groups and flexibility of organic building blocks were crucial for regulating the structure and luminescence as well as detecting activity of MOFs. Three Complexes of a flexible carboxylate ligand with –CH2-O- groups, namely, [Cd3(L)2(DMF)4]n (1), {[Cd3(L)2(bpea)3(H2O)4]∙2H2O∙4DMF}n (2), and [Cd3(L)2(bpy)]n (3) (H3L = 3,5-bis[(3-carboxyphenyl)oxy]benzoic acid, bpea = bis(pyridyl)ethane, and bpy = 4,4′-bipyridine), were synthesized under solventhermal conditions. Both complexes 1 and 2 exhibit interesting 2-D trilayer structures with (3,6)- and (3,4,6)-connected topology, respectively. Complex 3 displays 3-D complicated framework, in which Cd2+ ions are connected by the carboxylate groups of L3− ligands into 3-D motifs and further linked by bpy ligands. The flexible carboxylate ligand adopts three different coordination modes with the aromatic rings forming diverse dihedral angles. Luminescence measurements reveal that both the frameworks and the solvents play an important role on the sensing activities. Three complexes can selectively and sensitively detect Fe3+ and Cr2O72− in DMF through luminescence quenching (turn-off) with the latter two showing high water stability and sensing activities toward Fe3+ and Cr(VI) (Cr2O72− and CrO42−). The detection limits are in the range of 0.21–2.05 μM, comparable or superior to those of previous luminescence sensors. Specially, complex 3 could also detect Pb2+ in H2O with detection limit of 1.43 μM (0.30 ppm). The building units, the structures, the sensing media all have an effect on the sensing activities. Possible quenching mechanisms for detection of these ions were carefully investigated and proposed based on luminescence inner filter effect (IFE) and weak interactions between the target ions and frameworks. Moreover, the recoveries of 96.7–103.4% for the detection of above ions in tap water samples are achieved, suggesting practical application.

A novel algorithm by combining nonlinear workspace partition with neural networks for solving the inverse kinematics problem of redundant manipulators

Abstract. Redundant manipulators (RMs) have been gaining more attention thanks to their excellent merits of operating flexibility and precision. Inverse kinematics (IK) study is critical to the design, trajectory planning, and control of RMs, while it is usually more complicated to solve IK problems which may inherently have innumerable solutions. In this work, a novel approach for solving the IK problems for RMs while retaining the redundancy characteristics has been proposed. By employing a constraint function, the method delicately reduces the infinite IK solutions of a RM to a finite set. Furthermore, the workspace of RMs is divided into nonlinear partitions through diverse joint angle intervals, which have further simplified the mapping correlations between the desired point and manipulators' joint angles. For each partition, a pre-trained neural network (NN) model is established to acquire its IK solutions with high efficiency and precision. After combing all nonlinear partitions, multiple reasonable IK solutions are available. The presented method offers a possible selection of the most appropriate solution for trajectory planning and energy consumption and therefore has the potential for facilitating novel robot development.

Effect of Main Channel Bed Roughness on the Branch Channel Discharge . (C)

In light of the current complex water situation in Egypt, scientists and researchers have to develop alternative plans to provide new quantities of water by paying attention to the constructions and tools that are used in distributing and controlling the flow in open channels. One of the most critical parameters in the analysis of diversion channel flow is the discharge ratio (Qr). It is the primary goal of this research to investigate the effect of changing the bed roughness of the main channel on the discharge of the branch channel (Qb). The bed roughness of the branch channel was kept constant (nb = 0.01), while for the main channel bed roughness was changed to five values (nm = 0.01, 0.016, 0.023, 0.033, and 0.04). The diversion angle of the branch channel was taken as (45˚), which gave a maximum (Qr) as recommended by some researchers. A discharge range from 4.88 to 17.14 L/sec was used, and 35 runs were conducted. From the analysis of the laboratory data, it was found that the discharge ratio (Qr) decreases as the total discharge through the main channel increases. While it increases with the increase of bed roughness ratios (nr). Moreover, at the bed roughness ratios (nr) ranged from 2.20 to 3.0, the difference in the discharge ratio (Qr) is no significant, for all discharge values passing through the main channel. Thus, maintaining a constant flow rate for the branched channel is considered one of the most essential factors in designing these channels, as it is vital in distributing water shares as percentages and in a consistent manner.

Complexity and tortuosity hydraulic fracture morphology due to near-wellbore nonplanar propagation from perforated horizontal wells

Perforated fracturing enhances single well production in the tight sandstones formations with low porosity and permeability effectively, however, some issues are caused after such achievements, such as high breakdown pressure, short fracture length, and limited proppant migration. All are tightly related to hydraulic fracture complex propagation behavior near wellbore. To understand its mechanism, a 3D near-wellbore fracture propagation model is established based on the combination of finite element method and post-failure damage mechanism. The model is applied on a cased and perforated horizontal well to investigate fracture initiation characteristics, near-wellbore fracture non-planar propagation behavior, and torturous hydraulic fracture morphology. Moreover, the effects of stress shadow and perforation parameters are discussed. Based on induced hydraulic fracture initiation position and propagation speed, three main fracture propagation behaviors are observed under the stress shadow effect in simulation results: limited propagation, nonuniform circular propagation, and opposite direction propagation. These nonplanar propagation behaviors cause complexity and tortuosity hydraulic fracture morphologies near the wellbore, which could be mainly divided into four types: spiral-shaped fracture, multi-spiral shaped fracture, horizontal-vertical crossing shaped fracture, and multi-layered shaped fracture. In addition, the reasonable perforation parameter design could reduce torturous fracture surface, resulting in a near flat fracture. The increase in perforation density or perforation diameter could shorten perforation spacing to provide a small diversion angle for induced fractures to interact with each other and form a small spiral degree fracture geometry. However, increased perforation phase causes many perforations in the same direction to create a longitudinal fracture that has a short fracture length for the horizontal well. Therefore, based on above analyses, high perforation density, small perforation phase, and large perforation diameter are suggested to be an effective perforation parameter combination to conduct the perforated fracturing in tight sandstone formation, in order to create a near flat fracture surface with a minimum tortuosity as well as to increase hydraulic fracture propagation area.

Distinctive Weak Interactions Underlie Diverse Nucleation and Small-Angle Scattering Behavior of Aqueous Cholesterol, Cholesteryl Hemisuccinate, and Glycocholic Acid.

Increased total cholesterol is a major cause of serious heart ailments leading to an estimated 3 million deaths annually throughout the world. Understanding the flocculation behavior of small lipids is thus quintessential. Nucleation, small-angle scattering, and dynamical behavior of lipids and analogues like cholesterol (CHL), cholesteryl hemisuccinate (CHM), and glycocholic acid (GHL) are studied in water by molecular dynamics simulation. The study shows a distinct aggregation behavior of these physiologically relevant molecules owing to a systematic gradation in their non-bonding interactions with solvents and near neighbors. Spontaneous self-assemblies formed during simulation are observed to have different stability, aggregation patterns, and dynamics depending crucially on the nature of the hydrophobic/hydrophilic tails. With increasing hydrophilicity, in the order CHL < CHM < GHL, the aggregates become breakable and less compact, often interposed by water molecules in the interstitial spaces between the lipids. Small-angle scattering data obtained from our simulations provide insights toward the structural integrity and shape of the aggregates formed. Unique features are noticed while following the time evolution of the packing of the nucleated assemblies from the solution phase in terms of local density and molecular orientation. As hydrophilicity increases from CHL to GHL, the packing becomes progressively erratic with diverse angles between the molecular vectors. Surface electrostatic potential calculation indicates drastic increase in positive surface charge from CHL to CHM, which has strong implication in water and ion transport through membranes. These observations can be further correlated to comprehend the flocculation of cholesterol and bile acids in the human body.

Synthesis of Micro-Doppler Signatures of Human Activities From Different Aspect Angles Using Generative Adversarial Networks

In this paper, we propose to produce synthesized micro-Doppler signatures from different aspect angles through conditional generative adversarial networks (cGANs). Micro-Doppler signatures of non-rigid human body motions vary considerably as a function of the radar's aspect angle. Because the direction of the human motion can be arbitrary, a large volume of training data across diverse aspects is needed for practical target activity classification through machine learning. As measurements can require significant monetary and labor costs, the synthesis of micro-Doppler signatures can be an alternate solution. Therefore, we investigate the feasibility of data augmentation through synthesizing micro-Doppler signatures of human activities from diverse radar aspect angles with input data from a single aspect angle. For the training data, the micro-Doppler radar signatures of 12 human activities are generated from different angles ranging from 0 to 315 degrees, at 45-degree increments, through simulations. For each angle, cGANs are trained to synthesize the micro-Doppler signatures for that specific angle given micro-Doppler signatures from another angle. The output of each model is evaluated by calculating mean-square errors and structural similarity indexes between the synthesized micro-Doppler signatures and the ground-truth ones obtained from simulations. We test three different scenarios, and report the respective results.

Numerical Investigation on Hydrodynamic Performance of a Ducted Propeller for Vectored Underwater Robot

This paper investigated hydrodynamic performance of the Ka4-70+No.19A ducted propeller astern of a vectored underwater robot at diverse deflection angles. Employing SSTk-ω turbulence model combined with moving reference frame technique, numerical computation of the ducted propeller in a fully developed turbulence behind hull was carried out. The validity of the model was verified by comparing the numerical results of open water performance and the experimental values. The hydrodynamic performance of the ducted propeller was worked out and discussed in detail. The wake flow and thrust deduction fraction corresponding to different deflection angles were analyzed. Results show that the ducted propeller generates more thrust and requires more torque at lager deflection angle. In addition, the thrust deduction fraction increases with the increase of the deflection angle.

Fundamental frequency optimization of variable stiffness composite skew plates

In this study, natural frequencies and vibrational mode shapes of variable stiffness composite skewed plates are optimized applying a genetic algorithm. The variable stiffness behavior is obtained by altering the fiber angles continuously according to two selected curvilinear fiber path functions in the composite laminates. Fundamental frequency and related mode shapes of the plates are optimized for two different fiber path functions using the structural model obtained based on the virtual work principle. A three-layer composite skewed plate with four types of boundary conditions and different plate geometries is considered as case study in this research. Diverse sweptback angles as well as different aspect ratios are considered as various plate geometries. The present study aims to calculate the best fiber path with maximized fundamental frequency or in-plane strengths for a composite skewed plate. The generalized differential quadrature method of solution is employed to solve the governing equations of motion. Moreover, the linear kinematic strain assumptions are used, and the first-order shear deformation theory is employed to generalize the formulation for the case of moderately thick plates including transverse shear effects. Numerical results demonstrate the effect of the fiber angles, boundary conditions, and diverse geometries on the natural frequencies of the composite plate. The optimal fiber angles of each layer are presented for the above cases in free vibration analysis. It is verified that the application of optimized curvilinear fibers instead of the traditional straight fibers introduces a higher degree of flexibility, which can be used to adjust frequencies and mode shapes.

Diverse polarization angle swings from a repeating fast radio burst source.

Fast radio bursts (FRBs) are millisecond-duration radio transients1,2 of unknown origin. Two possible mechanisms that could generate extremely coherent emission from FRBs invoke neutron star magnetospheres3-5 or relativistic shocks far from the central energy source6-8. Detailed polarization observations may help us to understand the emission mechanism. However, the available FRB polarization data have been perplexing, because they show a host of polarimetric properties, including either a constant polarization angle during each burst for some repeaters9,10 or variable polarization angles in some other apparently one-off events11,12. Here we report observations of 15 bursts from FRB180301 and find various polarization angle swings in seven of them. The diversity of the polarization angle features of these bursts is consistent with a magnetospheric origin of the radio emission, and disfavours the radiation models invoking relativistic shocks.

Combination of Group Method of Data Handling (GMDH) and Computational Fluid Dynamics (CFD) for Prediction of Velocity in Channel Intake

This paper utilizes computational fluid dynamics as well as a group method of data handling (GMDH) method to predict the mean velocity of intake. Firstly, the three dimensional flow pattern in a 90-degree intake is simulated with ANSYS-CFX at a transverse ratio equal to one (W*b/W*m = 1) that W*m is the width of the main channel and W*b is the width of the branch channel. The comparison of mean velocity in the simulated intake and experimental channel represents the high accuracy of ANSYS-CFX modeling (mean absolute percentage error (MAPE) = 5% and root mean square error (RMSE) = 0.017). A group method of data handling (GMDH) is one type of artificial intelligence approach that presents elementary equations for calculating the problem’s target parameter and performing well in complex nonlinear systems. In this research, to train and test the GMDH method, input data is needed in all parts of the channel. Since there is not enough laboratory data in all parts of the channel, to increase the benchmarks, the laboratory model is simulated by the Computational Fluid Dynamics (CFD) numerical model. After ensuring the proper accuracy of the numerical results, the built-in CFD numerical model has been used as a tool to create primary benchmarks in the channel points, especially in areas where there is no laboratory data. This generated data has been used in training and testing the GMDH method. The diversion angle with the longitudinal direction of the main channel (θ), the longitudinal coordinates in the intake (y*), and the ratio of the branch channel width to the main channel (Wr) have been applied as the input training data in the GMDH method to estimate mean velocity. The results of the statistical indexes used to quantitatively examine this model, (R2 = 0.86, MAPE = 10.44, RMSE = 0.03, SI = 0.12), indicated the accuracy of this model in predicting the mean velocity of the flow within open channel intakes.

Hot‐cracking susceptibility of fully austenitic stainless steel using pulsed‐current gas tungsten arc‐welding process

AbstractThe pulsed‐current gas tungsten arc‐welding process (PCGTAW) has recently been recommended as an approach to eliminate the high susceptibility of austenitic stainless steel to hot cracking. Within a wide range of variables, in the present study, the effects of pulse frequency, time ratio, and pulse current on the cracking susceptibility of austenitic stainless‐steel thin sheets are investigated. A fan‐shaped cracking test specimen is adopted, and suitable final dimensions are obtained by conducting some preliminary experiments. A good correlation is found between the maximum crack length, which is taken as a cracking susceptibility index, and the pulse form variables. The results are found to be significantly improved when compared with those of the continuous‐current process, which indicates that the PCGTAW process has an effective role in reducing the hot‐cracking susceptibility. The optimal conditions of the pulse form variables based on the hot‐cracking susceptibility are determined. The optimal values of the time ratio are found to be less than 50%, together with a pulse frequency of less than 1 Hz. Some new microstructure measures, such as columnar structure ratio, grain orientation angle, puddle diversion angle, and overlapping ratio, which are originally defined in this work, in addition to grain size and puddle form factor (aspect ratio), are used to interpret the hot‐cracking behavior. All are found to have a direct impact on the hot‐cracking susceptibility. The results obtained from microstructure examinations showed that the cracks formed are either intergranular or transgranular cracks.

Development of a Helical Lamb Wave Electromagnetic Acoustic Transducer for Pipeline Inspection

The electromagnetic ultrasonic testing presents great potential in structural health monitoring due to its non-contact advantage. The electromagnetic acoustic transducers generating torsional and longitudinal guided wave have been extensively studied for pipeline structure. However, the transducer for helical wave and corresponding analysis still have not been adequately investigated. This paper proposes the novel transducer to generate helical Lamb wave in pipeline. Based on the Lorentz mechanism, the developed transducer contains the fan-shaped magnetic poles and a two-layer coil. The finite element model is built to simulate the wave generation and propagation from the transducer. The displacement distribution verifies the capacity of generating helical wave. The excitation and reception of helical wave are also carried out in the experiment. The actual frequency of the transducer measured from the frequency-sweeping coincides with the designed value. In addition, the defect detection experiment is conducted. The axial and circumferential location can be obtained according to the amplitude and time information. The further comparison and discussion indicate that the prior transducer with meander coil is not appropriate to generate helical wave. The developed transducer can generate wave with diverse incident angle which is superior than the transducer for torsional and longitudinal modes.