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The spray forming of thick, dissimilar steel clad tubes with the objective of achieving a high integrity metallurgical bond across the cladding-substrate interface able to withstand residual stresses and subsequent thermo-mechanical processing was investigated by large scale experiments, modelling and extensive microstructural characterization including microscopy, X-ray tomography, neutron scattering and mechanical testing. The simulated residual stress distributions across the cladding-substrate interface, accounting for any as-sprayed porosity and the distribution of martensitic and retained austenite phases, were compared with neutron diffraction measurements and differences used to infer the load transfer behaviour and thus the mechanical integrity of the interface. The mechanical properties of the interfaces were then also measured directly by shear testing. The link between substrate pre-heating, the spray forming temperature, and the resulting preform temperature, porosity, phase fractions, residual stress, strength and integrity of the interface were established and quantified explicitly. [ABSTRACT FROM AUTHOR]

The rapid microstructural evolution of gas atomised Ni superalloy powder compacts over timescales of a few seconds was studied using a Gleeble 3500 thermomechanical simulator, finite element based numerical model and electron microscopy. The study found that the microstructural changes were governed by the characteristic temperatures of the alloy. At a temperature below the γ' solvus, the powders maintained dendritic structures. Above the γ' solvus temperature but in the solid-state, rapid grain spheroidisation and coarsening occurred, although the fine-scale microstructures were largely retained. Once the incipient melting temperature of the alloy was exceeded, microstructural change was rapid, and when the temperature was increased into the solid + liquid state, the powder compact partially melted and then re-solidified with no trace of the original structures, despite the fast timescales. The study reveals the relationship between short, severe thermal excursions and microstructural evolution in powder processed components, and gives guidance on the upper limit of temperature and time for powder-based processes if desirable fine-scale features of powders are to be preserved. [ABSTRACT FROM AUTHOR]

Neutron diffraction was used to characterize the residual stresses in an as-sprayed tube-shaped steel preform. The measured residual stress distributions were compared with those simulated using finite element method by taking into account the effects of the thermal history, porosity and different phases of the sprayed preform. The porosity was measured using X-ray microcomputed tomography. The study revealed for the first time the correlation between the distribution of porosity and residual stress developed in the as-sprayed preform. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synchrotron X-ray total scattering method was used to study tensile fractured surface of a metallic glass and a metallic glass composite. • A clear correlation was found between X-ray scattering structure factor and the shear band density. • The higher the shear band density, the higher the X-ray scattering structure factor. • Such correlation has the potential to be developed into a nondestructive method for measuring the residual shear band density for metallic glasses after deformation. The tensile fractured surfaces of ZrTi-based bulk metallic glass and composite samples were studied using synchrotron X-ray total scattering. The scanned areas contain different shear bands densities. The shear bands create localized atomic strains, which in turn cause more ordered atomic structures. Such structural changes were reflected in the scattering structure factor, i.e. the higher the density of the shear bands, the higher the scattering structure factor. Similar phenomenon was also found in the metallic glass composite. [ABSTRACT FROM AUTHOR]

The mechanical performances of timber joints are particularly important for timber engineers involved in the design of the wood structures. In general, joints are often one of the weakest points in a timber structure. However, to simplify the problem, most previous investigations have considered the effects of individual parameters on the mechanical behavior of timber joints. Thus, it is difficult to undertake an analytical study due to interactions among parameters. In this paper, a finite element model for a dowel-type timber joint is proposed to investigate the mechanical performance of un-reinforced and reinforced timber joints affected by the various parameters. Moreover, a stress-interaction based failure criterion is proposed to predict the strength of such joints. The numerical prediction of the proposed finite element method model overall agrees with the experimental results of mechanical testing. [Copyright &y& Elsevier]

An accurate tidal forecast is an important task in determining constructions and human activities in ocean environments. Conventional tidal forecasting has been based on harmonic analysis using the least squares method to determine harmonic parameters. However, a large number of parameters are required for the prediction of a long-term tidal level with harmonic analysis. Unlike conventional harmonic analysis, this paper presents an artificial neural network (ANN) model for forecasting the tidal-level using the short term measuring data. The ANN model can easily decide the unknown parameters by learning the input–output interrelation of the short-term tidal records. Three field data with three types of tides will be used to test the performance of the proposed ANN model. The numerical results indicate that the hourly tidal levels over a long duration can be predicted using a short-term hourly tidal record. [Copyright &y& Elsevier]

Accurate tidal prediction and supplement is an important task in determining constructions and human activities in coastal and oceanic areas. The harmonic tidal level is conventionally used to predict tide levels. However, determination of the tidal components using the spectral analysis requires a long-term tidal level record (more than one year [Handbook of coastal and ocean engineering 1 (1990) 534]). In addition, calculating the coefficients abbreviated of tide component using the least-squares method also requires a large database of tide measurements. This paper presents an application of the artificial neural network for predicting and supplementing the long-term tidal-level using the short term observed data. On site, tidal-level data at Taichung Harbor in Taiwan will be used to test the performance of the artificial neural network model. The results show that the tidal levels over a long duration can be efficiently predicted or supplemented using only a short-term tidal record. [Copyright &y& Elsevier]

• Bulk CoCrFeMnNi high entropy alloy was fabricated by laser melting deposition. • The residual stress distribution was characterized using ND and FEM. • Residual stress decreases along the building direction. The dynamic thermal history during the laser melting deposition (LMD) process can induce significant residual stress that can lead to distortion and deteriorate functionality. The residual stress distribution in a bulk CoCrFeMnNi high entropy alloy with a single FCC phase and the dendritic structure fabricated by LMD process was studied using neutron diffraction and finite element modelling to reveal the effects of the thermal constraints, thermal cycles and temperature gradient along the deposition direction. Residual stress was found to decrease as the thermal gradient decreases along the building direction in the LMD process. [ABSTRACT FROM AUTHOR]

Highlights • A validated analytical-numerical model of the DED process is presented. • Finite element model uses realistic track geometry to predict residual stress and distortion. • A modified catchment efficiency was utilised in the analytical model to allow a more realistic approach to be implemented. • The maximum error for the peak temperature and residual stress was 3.1% and 18% respectively. Abstract Direct Energy Deposition (DED) is being increasingly used to repair high value components that have been damaged in-service. The uptake of DED and laser cladding operations for repair is inhibited by accurate modelling techniques. Often the repair process required is unique, therefore modelling techniques are necessary to determine the process inputs for the specific application. The DED process subjects the component to high thermal gradients resulting in high magnitude residual stresses and component distortion. Prediction of these parameters would reduce the need for costly experimental trials to quantify the repair strategy. Here, a single-track deposition of IN718, utilising a Nd:YAG laser source and coaxial nozzle, was modelled using a semi analytical-numerical approach. The track profile, temperature fields, melt pool geometry and stress evolutions were simulated for a constant set of process parameters. A corresponding experimental trial was conducted to validate the proposed model, through the use of focus variation microscopy, in-situ temperature measurements, optical micrographs and neutron diffraction measurements. A good correlation between the experimental and numerical data sets were apparent. The track profile was predicted with a maximum error of 1.98% and 0.43% for the width and height respectively. The maximum error for the peak temperature and residual stress was 3.1% and 18% respectively. Overall, the modelling strategy presented encompasses the key process variables, allowing accurate predictions of the thermal and mechanical effects of the process. Graphical abstract Image, graphical abstract [ABSTRACT FROM AUTHOR]

Abstract: Monohydride-terminated n-Si(111) electrodes were used as substrates for the electrodeposition of Cu from 0.1M H2SO4+0.1mM CuSO4. In situ scanning tunneling microscopy, ex situ atomic force microscopy and scanning electron microscopy revealed that (a) the nucleation starts preferentially at surface defects such as etch pits or step edges, and (b) the deposition occurs by a Volmer–Weber growth mode. In situ surface X-ray diffraction on this system, reported for the first time, revealed the structure and the epitaxial relationship of the copper deposit on the Si substrate. Under the X-ray beam, the Cu deposit could be stabilized only with a significant overpotential. Cu clusters grow with the (111), (110), and (001) planes oriented parallel to the Si(111), with the first two orientations being dominant. Within the Si(111) plane, Cu clusters can be found in any rotational orientation around the Si(111) surface normal. The intensity distribution can be described as powder rings. This distribution is, however, peaked along specific directions. For the Cu clusters with Cu(110)∥Si(111) it is found that in-plane Cu〈111〉∥Si〈110〉. The peaks in the distribution of the Cu clusters with Cu(111)∥Si(111) reveal that these Cu clusters are basically rotated by 30° around the Si(111) surface normal but exhibit additionally a ±4.5° epitaxial rotation around the mean, high symmetry direction. [Copyright &y& Elsevier]

Direct Energy Deposition (DED) is being widely used to repair damaged components to increase service life and economical operation. Process parameters including laser power, traverse speed and the mass flowrate of the feedstock material may be adapted in-situ. This allows bespoke repair strategies to be devised to match the variability in the condition of the parts supplied that require repair; however, there are limited modelling techniques that allow the adaptive control within the DED process to be represented. In this study, a novel modelling strategy is presented which allows the DED process to be modelled in a transient state. This allows varying process parameters to be included in the model, to predict the transient track geometry and the associated thermomechanical effects of the process. Here, a single-track deposition of IN718 with a varying cross section has been modelled utilising the proposed approach. The modelling methodology was validated with a corresponding experimental study on a deposition made using a Nd:YAG laser source with a coaxial nozzle. An in-situ modification was generated by variation of the laser power. The track profile was compared against focus variation microscopy images and the thermomechanical portion of the model was validated through in-situ temperature measurements, micrographs and residual stress, obtained from neutron diffraction measurements. A good agreement between the predicted and experimental findings were observed. The track height and width were predicted with a maximum error of 6.5% and 7.6% respectively. The peak temperature and residual stress were predicted within 6.2% and 11.4% respectively. Overall, the modelling method presented will allow complex and bespoke multi parameter repair strategies to be rapidly developed. Image 1 • A validated analytical-numerical model of the adaptive DED process is presented. • Model predicts track geometry during transient regions of the process. • The maximum error for the track width and height was 5.1% and 12.5% respectively. • The maximum error for the peak temperature and residual stress was 6.2% and 11.4% respectively. [ABSTRACT FROM AUTHOR]

Abstract The fatigue fragmentation of dendritic structures of a SCN-5 wt.% Camphor transparent alloy in an ultrasound field was investigated systematically using high-speed imaging. Dynamic interactions between oscillating ultrasonic bubbles and the primary and secondary dendrites were observed and recorded. High speed images show that when an ultrasound bubble was trapped inside an interdendritic region, the oscillation of the bubble can cause cyclic bending of the dendritic arms. Consequently, a fatigue type crack initiated at the arm root and propagated through the dendrite, causing the dendrite to fragment, i.e. dendritic fragmentation. From the recorded videos, the cycle numbers for the fatigue fragmentation were extracted, then, the fatigue strength and fatigue life of the SCN-5 wt.% Camphor transparent alloy were calculated. Results showed that the cyclic fatigue load cause a crack initiating on a SCN dendrite at a much lower stress level than its tensile strength under high frequent oscillation. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Additively manufactured intersections have the theoretical risk to contain hydrostatic tensile residual stresses, which eventually cannot be thermally stress relieved. The stresses in Ti-6Al-4V wire + arc additively manufactured (WAAM) intersections are lower compared to single pass walls and stresses in continuous walls are larger compared to discontinuous walls with otherwise identical geometry. Thermal stress relief was found to virtually eliminate them. Inter-pass rolling can yield the desired grain refinement, without having any noteworthy influence on the development of residual stresses. The strain measurement itself by neutron diffraction is facilitated by the refined microstructure, because the otherwise textured microstructure produces anisotropic peak intensity, not allowing Pawley refinement. Without rolling, the 10 1 ¯ 1 and 10 1 ¯ 3 family of hcp planes are the only ones that diffract consistently in the three principal directions. [ABSTRACT FROM AUTHOR]

The effect of hydrogen charging on dislocation multiplication in super duplex stainless steel was investigated. Steel samples were pre-strained and charged with hydrogen for 10 days. Dislocation density was then measured using neutron diffraction. It is found that dislocation density multiplies by about one order of magnitude in samples with less than 5% pre-strain, but remains the same level in samples with pre-strain level of 10% and above. [ABSTRACT FROM AUTHOR]

Describes the polarity of a 1 um thick GaN film grown by molecular beam epitaxy on an single crystal using the x-ray standing wave method. How the standing was generated from the GaN film; Qualities of noncentrosymmetric compound crystals; What perfect single crystals exhibit.

A novel interdendritic-melt solidification control (IMSC) technique is developed to manufacture equiaxed Ni-based superalloy with much reduced porosity. The basic concept of IMSC is illustrated. The effects of IMSC on the porosity and phases of IN792 alloy are investigated using quantitative metallography and synchrotron X-ray diffraction. Compared to conventional investment casting, IMSC can produce castings with no shrinkage porosity, much less microporosity and larger dendritic arm spacing, slightly larger sized eutectic (γ+γ′) and MC carbides, and has no significant effects on the relative amount of phases. [ABSTRACT FROM AUTHOR]

Abstract: The effects of shallow trench isolation (STI) induced mechanical strain on gate induced drain leakage (GIDL) current in Hf-based and SiON n-type metal oxide semiconductor field effect transistors (nMOSFETs) are investigated in detail. With T-CAD simulator, the compressive strain is found to increase with decreasing active area length. The STI-induced mechanical strain induces band narrowing and increases intrinsic carrier concentration, thus enhancing GIDL current via both trap-assisted tunneling and band-to-band tunneling. In addition, the HfO2 gated nMOSFET has higher strain sensitivity than that of the SiON gated device for the higher density of interface states induced by the mechanical strain. Finally, the symmetric layout shows a higher ability to suppress the STI-enhanced GIDL current with the same active area length. [Copyright &y& Elsevier]

A potential connection between the residual stresses generated by a cladding operation, the thermal stresses generated during post weld heat treatment (PWHT), and the propensity for underclad cracking was investigated. As-deposited residual stresses were measured at ambient temperature, using the contour method and neutron diffraction. Measurements were performed in 20 mm thick steel substrates that were partially clad with AISI grade 309 (layer 1) and grade 308 (layer 2) stainless steels, using the submerged-arc welding process. Neutron diffraction measurements were also performed after heating the clad samples to 200 and 325 °C. The mechanical properties in each region within the steel heat affected zone (HAZ) were determined, at those same temperatures, by subjecting coupons to simulated cladding thermal cycles and then to tension tests. Substantial tensile residual stresses in the HAZ were measured after cladding. These persisted during subsequent heating to 325 °C: a temperature that is approximately at the mid-point of the heating ramp in a typical PWHT cycle. The tensile results, however, indicated that each microstructural zone within the HAZ is likely to retain sufficient ductility to prevent fracture, and that underclad cracking is unlikely to occur during the early stages of the PWHT ramp. • Residual stresses can be a risk factor for underclad cracking. • May be particularly detrimental during heating in the post weld heat treatment. • They were measured using the contour method and neutron diffraction while heating. • Substantial stresses were recorded. Tension tests were performed too during heating. • The heat affected zone seems to have sufficient ductility to prevent fracture. [ABSTRACT FROM AUTHOR]

Abstract: The trapping characteristics of positive bias temperature instability (PBTI) on a high-k/metal gate n-type metal oxide semiconductor field effect transistor (nMOSFET) have been investigated with a complementary multi-pulse technique (CMPT) in detail. With the CMPT technique, we found the threshold voltage shifts after PBTI are higher than that with the conventional direct current method, and the thickness of the SiO 2 interfacial layer has a significant effect on the measured results. The observation of these new results is attributed to the CMPT technique has the unique feature of effectively reducing the detrapping effect induced by the large bulk traps existed in high-k dielectrics. Besides, based on the results, the mechanism of PBTI in metal gate/high-k nMOSFETs is re-modeled. [Copyright &y& Elsevier]

Abstract: Electrochemical deposition of Cu and Co in monolayer amounts on hydrogen terminated Si(111) was studied ex situ and in situ by X-ray techniques. The X-ray beam was found to have a strong effect on the deposit causing desorption under the beam. Cu deposition on GaAs(001) from UHV is compared with electrodeposited Cu on the same surface, elucidating similarities and differences of electrochemical and UHV deposition. Roughening due to corrosion of Cu3Au(111) is observed by crystal truncation scattering. The observed behaviour of passivation of this surface is explained by the formation of Au clusters, increasingly covering the surface at higher oxidation potential. [Copyright &y& Elsevier]

Klebsiella infection has previously been reported in a few patients with transfusion-dependent thalassemia. The incidence and clinical spectrum of this infection in our cohort of patients were reviewed retrospectively. Among 160 patients observed for 12 years, there were 15 episodes of Klebsiella infection that occurred in 12 patients (7.5%), resulting in an incidence of 0.78 infections per 100 patient-years. The clinical spectrum included sinusitis (4 cases), intracranial infection (5 cases), septicemia (4 cases), and abscesses of the liver, lung, kidney, and parotid gland (1 case each). Three patients had recurrent infections involving different sites, 2 (16%) died of fulminant septicemia, and 3 (25%) had significant permanent neurological deficits. The antibiotic susceptibility pattern for the isolates was similar to the pattern for isolates recovered in the community. With regard to predisposing factors, iron overload and liver function derangement were found to be significant on univariate analysis (P = .046 and P = .049, respectively) but insignificant on multivariate analysis. Klebsiella infection was a serious and frequently encountered complication in our patients with transfusion-dependent thalassemia, resulting in high mortality and morbidity rates. [ABSTRACT FROM AUTHOR]

Abstract: Narrow 〈110〉Si oriented trenches with high aspect ratio served as template to grow Ge on Si (001) substrate. Cross section high resolution transmission electron microscopy reveals a high crystalline quality relaxed Ge inside the trench with only a few structural defects in the vicinity of a well ordered misfit dislocation grid at the Ge/Si interface. These dislocations are formed along the 〈111〉Ge lattice planes and terminate in the first 20nm of grown Ge. The high structural Ge quality is maintained both parallel and perpendicular to the trench as was confirmed by additional plan view and cross section inspections along the trench. [Copyright &y& Elsevier]

• The tensile behavior of the BMGMC was studied in-situ using neutron diffraction. • The crystalline phase yielded prior to the amorphous phase during the loading. • A redistribution of the applied stress was also observed in (110) and (200) planes. In situ neutron diffraction has been used to study the tensile deformation behaviors of a ZrTi-based bulk metallic glass matrix composites (BMGMC) at room temperature. The crystalline phase yielded prior to the amorphous phase during the tensile loading, and the glassy matrix bore more stress partition during the plastic deformation stage. A redistribution of the applied stress in dendrites occurred in the grains with an orientation of (110) and (200) during the plastic deformation. This work provides new insights into the tensile deformation mechanism of the BMGMCs at the microscopic level. [ABSTRACT FROM AUTHOR]

Examines the dopant distribution of the silicon delta-doped gallium arsenide by transmission electron spectroscopy. Observation of different silicon doses from half a monolayer to two monolayers; Indication of excellent confinement of dopants in gallium arsenide; Uniform distribution of silicon atoms in the doped layer.