Previous Pass Research Articles

Formation and suppression mechanism of lack of fusion in narrow gap laser-arc hybrid welding

In this study, the main defect, i.e., lack of fusion (LOF), occurring at the sidewalls in narrow gap laser-arc hybrid welding (NGHW) was confirmed to depend on the cross-sectional shape of previous pass, which was classified into four types, namely concave, convex, middle convex, and inclined shapes. Only the concave shape was effective in suppressing the LOF because the sharp corner between the weld and sidewalls could not be completely filled by next pass in the other three types. The effects of the welding parameters on the concave degree of weld cross-sectional shape were obtained from the dimensionless analysis related to the driving forces in the molten pool. It was found that the welding parameters, namely the arc current, welding speed, and groove width had a significant effect on the concave degree, whereas the laser power and laser-arc distance had no direct effect. A semi-quantitative criterion was proposed to predict the occurrence of the LOF. The LOF was suppressed when the ratio of the electromagnetic force to the liquid viscosity force was larger than 3.21 × 105, and the ratio of the surface tension gradient to the liquid viscosity force was larger than 1.28 × 104. The suppression mechanism of the LOF in NGHW was discussed in terms of the forces and melt flow in the molten pool.

The Feasibility and Effectiveness of PASS Plus, A Lay Health Worker Delivered Comprehensive Intervention for Autism Spectrum Disorders: Pilot RCT in a Rural Low and Middle Income Country Setting.

The treatment gap for autism globally is high. Our previous PASS intervention, delivered by community based lay health workers, showed effectiveness. This article reports the development and evaluation of a new "PASS 'Plus'" intervention in a rural population in India. Using formative research methods, we supplemented the PASS intervention with additional (Plus) modules to address autism comorbidities. This is the first time that a rigorous methodology has been used to evaluate autism symptom outcomes in a low and middle-income country setting. 40 parent-child dyads were recruited in a pilot randomized controlled trial against usual care (mean age 65 months (34 boys); n = 19 PASS Plus, n = 21 UC). 89% of intervention families partially or entirely completed the 12-session intervention. Intention to treat analysis showed a reduction in mean scores of autism symptom severity, though the confidence interval contains zero, (adjusted mean difference AMD -2.42 95% CI -7.75, 2.92; ES 0.22); large treatment effects on proximal outcomes of proportion of parent synchronous responses (AMD 0.35; 95% CI 0.18, 0.52; effect size ES 3.97) and proportion of child communication initiations with parent (AMD 0·17; 95% CI 0.03, 0.32; ES 1.02). Confidence intervals for effects on mutual shared attention (AMD 0.10; 95% CI -0.07, 0.27; ES 0.5) and co-morbid symptoms (AMD -9.0; 95% CI -24.26, 6.26; ES 0.32) contained zero. There were significant effects to improve parental mental health. PASS Plus shows good feasibility and adds to the evidence of the effectiveness of task sharing complex autism interventions to lay health workers in India. Autism Res 2019, 12: 328-339 © 2018 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: This article describes the development of a comprehensive, community-delivered, intervention for young children with autism, which combines a previously developed parent-mediated communication intervention with support for co-morbid problems like challenging behaviors and sensory sensitivities. The unique aspect of this intervention is that it can be delivered by community health workers, addressing the lack of specialists in low resource settings. Our study reports the encouraging findings of a pilot trial evaluating its feasibility and effectiveness.

Ti6Al4V metal cutting chip formation experiments and modelling over a wide range of cutting speeds

Measured forces, chip geometry and tool temperatures from machining a mill annealed Ti6Al4V at cutting speeds mainly from 1 to 100 m/min, but in some cases down to 0.1 m/min, are reported, as well as mechanical testing of the material. Finite element simulations with inputs the measured flow stress, and subsequently a small high temperature strain hardening recovery correction, and a failure model calibrated from the cutting tests at speeds from 1 to 10 m/min, give satisfactory agreement with the higher speed tests once surface strain hardening and damage from the previous pass of the tool are taken into account. This paper’s originality is firstly to show that more complicated flow stress models involving large strain softening are not needed provided shear failure is included; and secondly its failure model: this proposes a non-zero failed shear stress depending on local pressure and temperature. The simulations provide relations between tool mechanical and thermal loading and cutting conditions to aid process improvement.

Influence of multi-pass friction stir processing on microstructure and mechanical properties of 7B04-O Al alloy

Three-pass friction stir processing (FSP) with different moving distances of the stirring tool between the two successive passes, 50% diameter of the pin (traditional way) and 50% diameter of the shoulder (novel way), was conducted on 7B04-O Al alloy. The result shows that an improvement in the mechanical properties of the processed zone is accomplished due to grain and second phase particles refinement. The hardness of the multi-pass FSP (M-FSP) sample is about HV 40 higher than that of the base metal. And the tensile strength of the M-FSP specimens is also significantly increased to about 1.4 times that of the base metal. Besides, the weak region of the processed zone is mainly dependent on the moving distance, where it is the previous pass stir zone in the traditional way and the transitional zone in the novel way. Increasing the rotational speed narrows the weak region in the novel way, while it does not in the traditional way.

Third-order updated full-discretization method for milling stability prediction

Based on third-order Newton interpolation polynomial and direct integration scheme (DIS), this paper proposes a method to generate stability lobe diagram in milling process. The dynamic model of milling process with consideration of regeneration effect is described by time periodic delay-differential equation (DDE). Then, the DDE is rewritten as state space equation by a transformation. After equally discretizing the time delay into a series of small time intervals, the state space equation of milling system is integrated on the small time interval. Both the state term and delayed term are interpolated by third-order Newton interpolation polynomial, and the periodic-coefficient matrix is interpolated by first-order Newton interpolation polynomial. The state transition matrix which reflects the discrete mapping relation of dynamic responses for current tooth pass period and immediate previous tooth pass period is obtained directly. The accuracy of the proposed method is evaluated by comparing with benchmark methods in terms of the rate of convergence. The efficiency of the proposed method is verified through the comparison of computational time with existing methods. The proposed method is proved to be an accurate and efficient method by the comparison results. The distinction between up-milling and down-milling operations is also analyzed by comparing the stability lobe diagrams for these two operations. Besides, according to the analysis of rate of convergence, the number of substitutions, which are used to convert the variables located out of the required range into the required range, may affect the results of stability lobe diagrams. Moreover, the stability lobe diagram cannot be generated by using fourth-order updated full-discretization method.

Stress and strain distribution in twist extrusion of AA6063 aluminum alloy

Twist extrusion is one of the common methods in the area of severe plastic deformation. By passing the sample through a twist channel grain refinement will occur. In this article, the twist extrusion process is modeled by ABAQUS finite element software. Three different approaches are used for prediction of strain field distribution for higher passes of TE. The FE results are compared with the experimental results of twist extruded AA6063 aluminum alloy specimens. A sensitivity analysis has been implemented to choose the proper element size and friction coefficient during simulation. The microstructures of TE samples have been observed by SEM microscopy and analyzed by Pixcaviator software. Comparing the results of the microstructure study and FE shows that importing the material properties and deformation field from the previous pass to the current pass is the best way to simulate a multi-pass twist extrusion process. The plastic strain distributions show that the effective plastic strain is higher at the corner of the samples than at the center of it. The FE results show that the maximum Von-Mises stress increases at the corner elements by increasing the extrusion passes from 42 MPa at pass #1 to 110 MPa at pass #7. Most of this increase occurs in the first three passes.

Orthogonal polynomial approximation method for stability prediction in milling

Based on orthogonal polynomial approximation scheme, this paper presents several stability prediction methods using different kinds of orthogonal polynomials. The milling dynamics with consideration of the regenerative effect is described by time periodic delay-differential equations (DDEs). Firstly, this work employs the classical Legendre and Chebyshev polynomials to approximate the state term, delayed term, and periodic-coefficient matrix. With the help of direct integration scheme (DIS), the state transition matrixes which indicate the mapping relations of the dynamic response between the current tooth pass and the previous tooth pass are obtained. The stability lobe diagrams for single degree of freedom (DOF) and two DOF milling models are generated by using the Legendre and Chebyshev polynomial approximation-based methods. The rate of convergence of the Legendre and Chebyshev polynomial-based methods is compared with that of the benchmark first-order semi-discretization method (1stSDM). The comparison results indicate that the rate of convergence and the numerical stability of the Legendre and Chebyshev polynomial-based methods are both need to be improved. In order to develop new methods with high rate of convergence and numerical stability base on DIS, the monic orthogonal polynomial sequences are constructed by using Gram-Schmidt orthogonalization to approximate the state term, delayed term, and periodic-coefficient matrix. The rate of convergence and the computational efficiency of the monic orthogonal polynomial-based methods are evaluated by comparing with those of the benchmark 1stSDM. The results turn out that the monic orthogonal polynomial-based methods are advantageous in terms of the rate of convergence and numerical stability. The stability lobe diagrams for single DOF and two DOF milling models obtained by the monic orthogonal polynomial-based methods are compared with those obtained by the 1stSDM. Finally, the monic orthogonal polynomial-based methods are proved to be the effective and efficient methods to predict the milling stability.

El ejercicio de la iniciativa legislativa de las Comunidades Autónomas ante el Gobierno de la Nación. Singularidad, déficits y propuestas de lege ferenda

Abstract: The article 87.2 of the Spanish Constitution assigns to the Assemblies of the Autonomous Communities the power to initiate state laws, power that can exercise before the National Government or the Chamber of Deputies. However, few studies dealing with the regional legislative initiative focusing exclusively on the second of the routes received by that article. Practically it has not been carried out any theoretical commentary try to make sense, to criticize and develop a certain guarantees to the use of the road with the Government. The procedure for exercising the request to government bills opens some substantive problems (for example, why should stimulate the implementation of the law before a body which is not a legislator?), and others of a procedural nature (mainly concerning the processing to be followed within the Government requests for bills approved by regional parliaments), all of which this study try to respond. For this, it examines each of the two phases through which the exercise of this regional initiative articulates. The first phase takes place within regional parliaments in accordance with the provisions of their respective parliamentary rules in order that such chambers approve the referral to the State Government a proposed bill. The second phase develops within the Government, which, if it decides to grant the request submitted by a regional Assembly, it will initiate the procedure for preparation, approval and subsequent submission to the state Parliament of the bill. We examined its regulatory framework, the assumption of the regional impulse by the Government (the “previous pass” of the Council of Ministers), or the advantages can have this form of the regional legislative initiative against the other form of regional legislative. Of particular interest is analyzed the consequences of the incomprehensible absence of a minimum procedure to prolong the action of the regional initiative with some kind of action to be taken by the Government of the Nation, which has the result of reducing to a “vacuum” the statutory provision of article 87.2 of the Constitution, for which reason it is proposed here some further measures de lege ferenda that are desirable in order to this institution might better fulfil their purposes in an efficient manner.

In situ scratch testing and abrasion simulation of WC/Co

WC/Co hardmetals are used in many applications where wear resistance is important. However, despite recent work, the microstructural basis of wear is not completely understood.This paper describes the results of in situ scratch experiments carried out with a NPL designed and manufactured microtribometer in which spherically ended diamond indenters were moved under load across polished WC/Co samples to generate damage. The microtribometer was mounted in the chamber of a high resolution SEM so that sequential images and video of the damage generated by repeat scratches could be captured. In the experiments, the effects of changing the number of repeat passes, and whether repeat passes were carried out in the same lateral position over the top of the previous pass or with a random lateral offset to simulate abrasion were also investigated.The results gave valuable information on details of how the damage observed was related to the WC/Co microstructure. A major mechanism of damage, clearly observed in the videos of the damage accumulation appended with this paper, was the progressive fragmentation of WC grains; the movement of the WC fragments could be followed from one pass to the next until they are finally removed from the wear interface as debris.

Inclusions and Microstructure of Ce-Added Weld Metal Coarse Grain Heat-Affected Zone in Twin-Wire Submerged-Arc Welding

In high heat-input multi-pass twin-wire submerged-arc welding, weld metal of previous pass will be affected by the heat input of subsequent one and form coarse-grained heat-affected zone (CGHAZ). This study focused on the effects of welding thermal cycle on the inclusions and microstructure of Ce-alloyed weld metal CGHAZ. According to the study of inclusions and microstructure of weld metal CGHAZ, it was found that the composition and type of the inclusions did not change under the effect of welding thermal cycle. Although the inclusions were coarsened slightly, the promoting ability to acicular ferrite (AF) was not deprived after thermal cycling. There are three types of AF in weld metal CGHAZ, which include oxy-sulfides of Ce inclusions-promoted AF, home-position-precipitated AF, and sympathetic AF. Results showed more than 80% of microstructure was AF, which greatly benefited the mechanical properties of weld metal CGHAZ, even though granular bainite and M-A constituents were generated.

Modeling State-Conditional Observation Distribution Using Weighted Stereo Samples for Factorial Speech Processing Models

This paper investigates the effectiveness of factorial speech processing models in noise-robust automatic speech recognition tasks. For this purpose, the paper proposes an idealistic approach for modeling state-conditional observation distribution of factorial models based on weighted stereo samples. This approach is an extension to previous single pass retraining for ideal model compensation which is extended here to support multiple audio sources. Non-stationary noises can be considered as one of these audio sources with multiple states. Experiments of this paper over the set A of the Aurora 2 dataset show that recognition performance can be improved by this consideration. The improvement is significant in low signal to noise energy conditions, up to 4% absolute word recognition accuracy. In addition to the power of the proposed method in accurate representation of state-conditional observation distribution, it has an important advantage over previous methods by providing the opportunity to independently select feature spaces for both source and corrupted features. This opens a new window for seeking better feature spaces appropriate for noisy speech, independent from clean speech features.

High strain-rate superplasticity of fine- and ultrafine-grained AA5083 aluminum alloy at intermediate temperatures

Abstract Superplastic behavior of fine and ultra fine-grained AA5083 Al alloy was examined using the shear punch test. To achieve fine- and ultra fine-grained microstructures, a relatively new severe plastic deformation (SPD) process, namely Double Equal Channel Lateral Extrusion (DECLE) was employed. The strain rate sensitivity indices (m) of samples were evaluated after 1, 2, 4, and 6 passes for shear strain rates in the range of 3 × 10− 3 to 3 × 10− 1 s− 1 and temperatures in the range of 573 to 673 K. For microstructural observations, TEM images together with the corresponding SAED patterns were prepared and utilized. A considerable increase in the m-value was observed after the first pass of the operation for all testing temperatures. The best condition for achieving a good superplasticity for the alloy was found to be a single pass DECLE at 673 K in the strain rate range of 10− 2 to 10− 1 s− 1. This process condition resulted in an m-value of 0.43, indicative of a high strain rate superplastic deformation behavior. Further passes of the SPD process did not show any sign of superplasticity until the last pass of the operation, during which the m-value slightly increased, compared with the previous pass.

Thermal Inactivation of Shiga Toxin–Producing Escherichia coli Cells within Cubed Beef Steaks following Cooking on a Griddle

Thermal inactivation of Shiga toxin-producing Escherichia coli (STEC) cells within knitted/cubed beef steaks following cooking on a nonstick griddle was quantified. Both faces of each beef cutlet (ca. 64 g; ca. 8.5 cm length by 10.5 cm width by 0.75 cm height) were surface inoculated (ca. 6.6 log CFU/g) with 250 μl of a rifampin-resistant cocktail composed of single strains from each of eight target serogroups of STEC: O26:H11, O45:H2, O103:H2, O104:H4, O111:H(2), O121:H19, O145:NM, and O157:H7. Next, inoculated steaks were (i) passed once through a mechanical tenderizer and then passed one additional time through the tenderizer perpendicular to the orientation of the first pass (single cubed steak; SCS) or (ii) passed once through a mechanical tenderizer, and then two tenderized cutlets were knitted together by passage concomitantly through the tenderizer two additional times perpendicular to the orientation of the previous pass (double cubed steak; DCS). SCS and DCS were individually cooked for up to 3.5 min per side in 30 ml of extra virgin olive oil heated to 191.5°C (376.7°F) on a hard-anodized aluminum nonstick griddle using a flat-surface electric ceramic hot plate. Regardless of steak preparation (i.e., single versus double cubed steaks), as expected, the longer the cooking time, the higher the final internal temperature, and the greater the inactivation of STEC cells within cubed steaks. The average final internal temperatures of SCS cooked for up 2.5 min and DCS cooked for up to 3.5 min ranged from 59.8 to 94.7°C and 40.3 to 82.2°C, respectively. Cooking SCS and DCS on an aluminum griddle set at ca. 191.5°C for 0.5 to 2.5 min and 1.0 to 3.5 min per side, respectively, resulted in total reductions in pathogen levels of ca. 1.0 to ≥6.8 log CFU/g. These data validated that cooking SCS (ca. 0.6 cm thick) or DCS (ca. 1.3 cm thick) on a nonstick aluminum griddle heated at 191.5°C for at least 1.25 and 3.0 min per side, respectively, was sufficient to achieve a 5.0log reduction in the levels of the single strains from each of the eight target STEC serogroups tested.

Microstructure Characterization of Single and Multipass 13Cr4Ni Steel Welded Joints

13Cr4Ni martensitic stainless steels are frequently used in hydroelectric industries. Considering the size and geometry of the turbine runners manufactured in hydroelectric industries, multipass welding procedures are common methods for fabrication and repair. In this research, the microstructures and crystallographic textures of single-pass and double-pass welds have been studied as a first approach to understand a multipass weld. The highest hardness has been measured in the high-temperature heat-affected zone (HAZ) inside the base metal. Similarly, it has been found that the heat of the second pass increases the hardness of the previous pass and produces a finer martensite microstructure. In areas of the HAZ, 3–6 mm from the fusion line, a tempering-like effect is reported; traces of austenite have also been found in these areas documenting the complexity of the microstructure found in the multipass welds.

Comparison of dislocation density based approaches for prediction of defect structure evolution in aluminium and copper processed by ECAP

Three known dislocation density based models are compared to each other, and to available experimental results. All three models were embedded into ANSYS finite element (FE) software and firstly utilised to predict aluminium and copper transformations (dislocation density evolution and the resulting grain size) in a result of a single pass of equal channel angular pressing (ECAP). It is demonstrated that for the studied problem dislocation density evolution under severe plastic deformation (SPD) can be precisely predicted utilizing simple classical model. One of the models was utilized to predict defect structure evolution for the series of ECAP passes. Simulations have revealed that within the framework of the proposed model the increase of the dislocation density on ECAP pass is proportional to yield strength increment on the previous pass for both studied materials. This fact gives grounds to a proposal of a semi-analytical approach, predicting dislocation density evolution in a result of consequent ECAP passes on the basis of a numerical simulation of the two first passes. The utilized kinetic model for dislocation density evolution separates between densities of mobile and immobile dislocations. Employing the idea of separation of dislocations into mobile and immobile, a new approach for dynamic recrystallization coupling dislocation density and the size of grain formed in metal is proposed. The proposed approach for dynamic recrystallization appeared to be applicable for the whole range of grain sizes.

A point-based variation propagation model for multi-pass machining process

In a machining process, the workpiece is usually machined by several passes to achieve the desired dimension and form. Workpiece deviation generated in the previous pass will affect the next pass. A new point-based variation propagation model for a single machining process with multi-passes was proposed in this article to investigate the relationships between different passes. The effects of locating errors, geometric errors of machine tool, and tool deflection on workpiece deviation are analyzed. Based on these analyses, a point-based variation propagation model for a machining process with multi-passes was derived. By including the influence of the tool deflection, a linkage between workpiece deviation and the cutting parameters is established. Since different passes are distinguished by their cutting parameters, the relationships between different passes are built up via this model. At the end of this article, case studies were carried out to validate the model and its application in cutting parameters’ optimization.

Modelling the creation and destruction of columnar and equiaxed zones during solidification and melting in multi-pass welding of steel

The authors present a novel meso-scale (mm–cm) numerical model of multi-pass welding of stainless steel based on the front tracking formulation. During a typical multi-pass notched butt weld, multiple cycles of melting and solidification occur throughout the weld pool, where previously solidified equiaxed zones are destroyed by melting and subsequently resolidify in columnar form. These thermal cycles result from the thermal effects of the current deposition of liquid filler metal being superimposed onto those of the previous pass. The advancement of the liquidus isotherm is employed to characterize melting, while both columnar and equiaxed dendritic growth in the undercooled melt are considered in the model of solidification. Columnar solidification is simulated using a front tracking method where computational markers are employed to explicitly define the advancing columnar front. Competing equiaxed solidification is modelled using a volume averaging approach. During the first and second welding passes of a case study, the weld pool solidifies as purely columnar. This is due to the high thermal gradient present in the weld pool, which results in a very small region of undercooled liquid ahead of the columnar front and subsequently low levels of equiaxed grain nucleation/growth. Towards the end of the third and final pass the equiaxed grains have sufficient dwell time in the undercooled liquid to form a coherent network and present a physical barrier to the advancing columnar front. A Columnar to Equiaxed Transition (CET) occurs and the remainder of the weld pool solidifies in a fully equiaxed microstructure. The results are compared with Hunt’s analytical model of CET and the agreement is reasonably good. The occurrence of CET throughout the weld pool is directly predicted via this front tracking model without the need to rely on estimated thermal gradients and solidification rates. Further simulations indicate that CET can be promoted, even in early passes, by increasing the grain refiner level and/or by pre-heating the parent metal.

Underground localization using dual magnetic field sequence measurement and pose graph SLAM for directional drilling

With the development of unconventional gas, the technology of directional drilling has become more advanced. Underground localization is the key technique of directional drilling for real-time path following and system control. However, there are problems such as vibration, disconnection with external infrastructure, and magnetic field distortion. Conventional methods cannot solve these problems in real time or in various environments. In this paper, a novel underground localization algorithm using a re-measurement of the sequence of the magnetic field and pose graph SLAM (simultaneous localization and mapping) is introduced. The proposed algorithm exploits the property of the drilling system that the body passes through the previous pass. By comparing the recorded measurement from one magnetic sensor and the current re-measurement from another magnetic sensor, the proposed algorithm predicts the pose of the drilling system. The performance of the algorithm is validated through simulations and experiments.

Microstructures of Hardfaced Overlay on Low Carbon Steel by Gas Tungsten Arc Melt Injection of Diamond Grits

Ni-coated diamond grits were injected into hardfaced Ni-based alloy overlay on a low carbon steel substrate as reinforcing particles with a gas tungsten arc melt injection method. Microstructures of the hardfaced overlay were investigated with scanning electron microscope, energy dispersion spectroscopy and X-ray diffraction analyzer. The results showed that the Ni coating on the injected diamond grits was sound and the diamond grits were not damaged thermally. A very thin layer of TiC formed on the interface between the diamond and the Ni layer. In the overlapped region of the multi-passes specimen, the diamond grits injected in the previous pass were damaged thermally, while the ones injected in the successive pass were not.

Characterization and prediction of mRNA alternative polyadenylation sites in rice genes.

Polyadenylation [poly(A)] of mRNA is a critical step during gene expression, which plays an important role in the termination of transcription. Prediction of poly(A) sites can help identify 3' ends of genes and improve genome annotation. Due to the limited knowledge of poly(A) signals in plants, predictive modeling of poly(A) sites in agricultural crops remains challenging. Recent studies have uncovered widespread occurrences of alternative poly(A) (APA) sites in intron and coding sequence (CDS), whereas the study on the prediction of these APA sites is scarce. In this study, four feature representation methods, involving a position weight matrix, the k-gram frequency, core hexamers, and a transition matrix, were adopted to characterize poly(A) signals surrounding APA sites. The classification model was built to predict each group of APA sites. Experimental results showed that this model was effective in the identification of APA sites located in different genomic regions, with a compromise between sensitivity and specificity higher than 87%. Compared with previous model PASS rice, accuracies for the prediction of APA sites in 3'-UTR, intron and CDS were enhanced by 5%, 7%, and 27%, respectively. This model will contribute to genetic engineering by enabling researchers to control poly(A) site selection.