Scale Growth Research Articles

Perspectives on selected alloys in contact with eutectic melts for thermal storage: Nitrates, carbonates and chlorides

Increasing the operating temperature of molten salt-based concentrated solar power plants is of paramount importance to enable next-generation gas turbines and an overall increase in power conversion efficiency. The issue is how to mitigate the degradation of necessary metallic components in highly corrosive salt environments. In this study, three eutectic salt mixture candidates, nitrates, carbonates, and chlorides, are brought into contact with stainless steel (316H or 304L) and the FeCrAl alloy Kanthal® APMT. The post-exposure analysis is discussed in terms of the overall performance of each alloy as concerns mass change, scale growth, internal attack, and leaching. Significant reduction of corrosion is realised through the ability of Kanthal® APMT to form aluminium oxide species at the surface in contact with alkali nitrates and carbonates. On the other hand, aluminium is leached most efficiently in contact with chlorides, which causes a deeper attack on Kanthal® APMT than alloy 304L.The overall conclusion is that only by employing a holistic perspective on all individual measurements can a long-term performance estimation be formulated.

Prevalence of benefit finding and posttraumatic growth in long-term cancer survivors: results from a multi-regional population-based survey in Germany

BackgroundCancer studies reported mixed results on benefit finding (BF) and posttraumatic growth (PTG) prevalence and few were focused on long-term survivors.MethodsBF and PTG were assessed in a multi-regional population-based study in Germany with 6952 breast, colorectal and prostate cancer survivors, using the Benefit Finding Scale and Posttraumatic Growth Inventory. We calculated the age-adjusted prevalence, stratified by demographical and clinical characteristics.ResultsOverall, 66.0% of cancer survivors indicated moderate-to-high BF, and 20.5% moderate-to-high PTG. Age-adjusted prevalence of BF and PTG differed according to cancer type (breast > colorectal > prostate) and sex (female > male). BF and PTG prevalence were higher in younger than in older respondents; the age-adjusted prevalence was higher in respondents who survived more years after diagnosis. The strength and direction of associations of age-adjusted prevalence with cancer stage, disease recurrence, and time since diagnosis varied according to cancer type and sex.ConclusionsA substantial proportion of long-term cancer survivors reported moderate-to-high BF and PTG. However, the prevalence was lower in older and male cancer survivors, and during the earlier years after cancer diagnosis. Further longitudinal studies on PTG and BF in cancer survivors are warranted to address heterogeneity in survivors’ experience after cancer diagnosis.

Phenotypic Convergence in Sea Bass (Dicentrarchus labrax) Escaping From Fish Farms: The Onset of Feralization?

The impact of fish escaping from fish farms may depend on the extent to which escapees adapt to the natural environment, resemble wild conspecifics, and become feral. Yet, little is known about the process of feralization in marine fish. We examined phenotypic changes in body shape, body condition, and scale growth profiles of sea bass escaping from fish farms in the Canary Islands and quantified the extent to which escapees had diverged from farmed conspecifics. Most feral sea bass had sizes that overlapped with those of farmed fish, indicating that they had escaped throughout the production cycle. However, 29% of escapees were larger than the maximum size at harvesting, indicating growth in the wild. Analysis of scale growth profiles showed that some escapees had grown in the wild as fast as cultured fish, albeit at more variable growth rates. Feral sea bass tended to converge towards a similar body shape, having more streamlined bodies, lower body condition, and lower hepatosomatic indices (HSI) than fish in cages. Although our study cannot discriminate between phenotypic plasticity and differential mortality of escapees, we interpret phenotypic convergence as the likely result of a period of initial starvation, phenotypic plasticity, and selection against maladapted phenotypes. Our results warn against the risks of rearing sea bass in open-net cages and suggest that sea bass escapees could pose a threat to shallow coastal assemblages, particularly in areas where the species is not naturally found.

In situ nanoparticle-induced anti-oxidation mechanisms: Application to FeCrB alloys

In this work, in situ nanoparticles (TiB2 and TiC) can be demonstrated to induce significant improvement in the oxidation resistance of Fe-12 wt.%Cr-3.5 wt.%B alloys. To unravel the roles of nanoparticles in the anti-oxidation of Fe-12 wt.%Cr-3.5 wt.%B alloys, samples with various nanoparticle contents were synthesized to investigate their oxidation resistance. Results show that nanoparticles facilitate the formation of a continuous and dense Cr2O3 protective film and enhance its adhesion with the matrix. Furthermore, the nanoparticle assembly on the surface of borides can inhibit the inward diffusion of oxygen ions and the outward diffusion of cations, thereby effectively controlling the growth of oxide scales.

The role of nitrogen in the oxidation behaviour of a Ti6242S alloy: a nanoscale investigation by atom probe tomography

When used at high temperature in air, titanium-based alloys form an oxide scale at their surface but also dissolve large amount of oxygen in their metallic matrix and this is a cause of embrittlement. Nitrogen is a secondary oxidant, which also dissolves in and embrittles the alloy. Oxidation experiments of Ti-6Al-2Sn-4Zr-2Mo-0.1Si titanium-based alloy, for 1000 h at 650 °C in synthetic air (N2-20%O2) and in a mixture of Ar-20%O2, showed that nitrogen decreases both oxide scale growth and oxygen dissolution. Atom probe tomography was used to investigate the alloy/oxide interface. The results revealed that the nitrogen effect is due to the formation of interfacial layers of oxynitrides and nitride (Ti2N), but also to the formation of a nitrogen rich α-titanium-based solid solution, which all act as diffusion barriers for oxygen, because of their low oxygen solubility. A comparison between the experimental results and thermodynamic calculations is also reported.

Optimization of construction site layout using dynamic hybrid bacterial and ant colony algorithm

The efficient plan of site arrangement during the construction phase has been considered a vital duty to successful project performance due to the productivity enhancement as well as safety in executions. The optimization of the Construction Site Layout Problem (CSLP) is a combinatorial complexity that regards numerous objectives and considerable growth of scale as increasing of constraints and facilities. The rearrangement on site may thus need to be had dynamic plannings at several interval schedules as construction evolves to accommodate site needs. To resolve the complexity of this problem, many studies based on the Meta-heuristic approach have been done, there are however always drawbacks and should be improved to be more optimal. This research proposes a new Hybrid Meta-heuristic model which is a combination of Ant Colony Optimization algorithm (ACO), Bacterial foraging algorithm (BFA), and Pair-Wise Exchange Heuristic algorithm (PWEH). The proposed algorithm is named Dynamic Hybrid Ant Colony Algorithm (DHACA) model that can enhance local and global searches simultaneously. In addition, parameter values are optimized to create a better solution. This research also demonstrates the effectiveness of DHACA compared with the previous studies such as Multi-objectives Genetic Algorithm (MOGA), Simulated Annealing Algorithm based Multi-objectives Genetic Algorithm (SA-based MOGA) on the CSLP. DHACA supports the construction site dynamic planning with constraints on facilities to improve work efficiency.

Real-time computational imaging of reverse osmosis membrane scaling under intermittent operation

Small-scale photovoltaic-powered reverse osmosis (PVRO) could be a game-changer for off-the-grid water-stressed communities. However, cost and maintainability issues, due to membrane fouling, remain potentially major limitations of intermittently run PVRO. In particular, there is a common perception that this intermittent operation causes premature membrane degradation but has not been fully evaluated to date. This study seeks to understand the impacts of intermittent operation on mineral scaling propagation in PVRO through real-time imaging and post-operation morphological analysis of the scales. Lab-mixed synthetic groundwater, supersaturated with CaSO4, was used as the feedwater to scale BW30 RO membranes. Then, scaling growth on a statistically significant portion of a spacer-filled RO crossflow channel was imaged in real-time. Comparison between continuous (24 h) and intermittent (8 h/d × 3 d) experiments did not indicate any negative effect of periodic shutdowns on flux decline, which is contrary to the perception that intermittent operation decrease membrane permeability. In-situ imaging further supported this observation and highlighted a slower growth of intensive scaling spots under intermittent operation. After intermittent shut-off periods, the scaling distribution on the membrane appeared thinner and more uniform, hinting a momentary osmotic backflow at the end of each intermittent cycle. Scanning electron microscopy also confirmed the reduced CaSO4 scale growth and a different morphological structure of the scales under intermittent RO operation. This macro-scale imaging and postprocessing approach can aid in the development of optimized backwash and rinsing cycles, reducing fouling-related irreversible damage to the membrane and increasing the accessibility of PVRO for remote communities.

Corrosion by Hot CO2 Gases

Heat-resisting alloys are designed to survive high-temperature oxidation by forming a slow-growing scale, usually Cr2O3, which acts as a barrier between the metal and its environment. However, alloys that succeed in this way when exposed to hot oxygen or air fail to do so in CO2 gas. Instead, they exhibit rapid “breakaway” corrosion, developing oxides of alloy base metal iron and/or nickel. The growth of these non-protective scales is accompanied by internal carburization of the underlying alloy. Carbon passes through the oxide, dissolves in the alloy, and precipitates chromium as carbide. Removal of chromium from its matrix makes the alloy incapable of reforming chromia, and recovery from breakaway becomes impossible.

Deep Structured Learning for Natural Language Processing

The real-time and dissemination characteristics of network information make net-mediated public opinion become more and more important food safety early warning resources, but the data of petabyte (PB) scale growth also bring great difficulties to the research and judgment of network public opinion, especially how to extract the event role of network public opinion from these data and analyze the sentiment tendency of public opinion comment. First, this article takes the public opinion of food safety network as the research point, and a BLSTM-CRF model for automatically marking the role of event is proposed by combining BLSTM and conditional random field organically. Second, the Attention mechanism based on vocabulary in the field of food safety is introduced, the distance-related sequence semantic features are extracted by BLSTM, and the emotional classification of sequence semantic features is realized by using CNN. A kind of Att-BLSTM-CNN model for the analysis of public opinion and emotional tendency in the field of food safety is proposed. Finally, based on the time series, this article combines the role extraction of food safety events and the analysis of emotional tendency and constructs a net-mediated public opinion early warning model in the field of food safety according to the heat of the event and the emotional intensity of the public to food safety public opinion events.

Research on the Measurement and Influencing Factors of Implicit Water Resources in Import and Export Trade from the Perspective of Global Value Chains

In this study, China’s virtual water trade was measured on the basis of multi-region input/output tables, and its influencing factors of change were decomposed. The results revealed that virtual water export and import increased from 161.5 billion tons and 114.07 billion tons in 2007 to 193.31 billion tons and 157.1 billion tons in 2014, respectively. Eight economies accounted for more than 50% of China’s total virtual water export and import, whereby the total of the United States, Japan, and Europe reached 44% (export) and 31.3% (import). The export scale, export of intermediate products, export industry structure, domestic water consumption coefficient, and domestic intermediate input structure were the main factors of the change in virtual water export. The growth of export scale was the primary reason for the growth of virtual water export. A decline in the domestic water consumption coefficient was the primary reason for the restrained growth of virtual water export. The import scale, import of intermediate products, import industry structure, water consumption coefficient of foreign countries, and the correlation among domestic industries were the main factors affecting the change in virtual water import. The growth of import scale was the primary reason for the growth of virtual water import in most sectors. A decline in the water consumption coefficient abroad was the primary reason for the restrained growth of virtual water import.

Preference-Aware Edge Server Placement in the Internet of Things

While it is well understood that edge computing can significantly facilitate IoT-related applications by deploying edge servers close to IoT devices, it also faces many challenges with numerous IoT devices connected and interacted. One of the most important issues is how to efficiently deploy edge servers under a certain budget with the explosive growth of data scale and user base. Existing studies for edge server placement fail to consider user’s query preferences since individual users may be interested in events in particular regions and are keen to receive up-to-date data streams that originate in regions of interest. In this article, we present a preference-aware edge server placement approach that offers better workload distribution in terms of both minimizing query latency and balancing the load of edge servers. To achieve this, we formulate edge server placement with multiobjective optimization as a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${p}$ </tex-math></inline-formula> -center problem and design two progressive approaches. We first propose quadratic integer programming (QIP) for small-scale data sets. Since the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${p}$ </tex-math></inline-formula> -center problem is an NP-hard problem, we thus propose a heuristic algorithm named TAKG (TAbu search with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K$ </tex-math></inline-formula> -means and Genetic algorithm) for large-scale data sets. To evaluate the utility of the proposed models, we have conducted a comprehensive evaluation on a large data set that is collected by more than 1900 IoT devices during 30 days. Experimental results indicate our approaches outperform all baselines significantly in terms of both query latency and load balancing.

Developmental, cellular and biochemical basis of transparency in clearwing butterflies.

ABSTRACTThe wings of butterflies and moths (Lepidoptera) are typically covered with thousands of flat, overlapping scales that endow the wings with colorful patterns. Yet, numerous species of Lepidoptera have evolved highly transparent wings, which often possess scales of altered morphology and reduced size, and the presence of membrane surface nanostructures that dramatically reduce reflection. Optical properties and anti-reflective nanostructures have been characterized for several ‘clearwing’ Lepidoptera, but the developmental processes underlying wing transparency are unknown. Here, we applied confocal and electron microscopy to create a developmental time series in the glasswing butterfly, Greta oto, comparing transparent and non-transparent wing regions. We found that during early wing development, scale precursor cell density was reduced in transparent regions, and cytoskeletal organization during scale growth differed between thin, bristle-like scale morphologies within transparent regions and flat, round scale morphologies within opaque regions. We also show that nanostructures on the wing membrane surface are composed of two layers: a lower layer of regularly arranged nipple-like nanostructures, and an upper layer of irregularly arranged wax-based nanopillars composed predominantly of long-chain n-alkanes. By chemically removing wax-based nanopillars, along with optical spectroscopy and analytical simulations, we demonstrate their role in generating anti-reflective properties. These findings provide insight into morphogenesis and composition of naturally organized microstructures and nanostructures, and may provide bioinspiration for new anti-reflective materials.

Mechanobiology of cell division in plant growth.

Cell division in plants is particularly important as cells cannot rearrange. It therefore determines the arrangement of cells (topology) and their size and shape (geometry). Cell division reduces mechanical stress locally by producing smaller cells and alters mechanical properties by reinforcing the mechanical wall network, both of which can alter overall tissue morphology. Division orientation is often regarded as following geometric rules, however recent work has suggested that divisions align with the direction of maximal tensile stress. Mechanical stress has already been shown to feed into many processes of development including those that alter mechanical properties. Such an alignment may enable cell division to selectively reinforce the cell wall network in the direction of maximal tensile stress. Therefore there exists potential feedback between cell division, mechanical stress and growth. Improving our understanding of this topic will help to shed light on the debated role of cell division in organ scale growth.

WSN Topology Control algorithm for High Speed Railway Monitoring

In order to solve the safety problems caused by the continuous improvement of train speed and the continuous growth of railway scale, it is inevitable to apply wireless sensor network (WSN) to train operation environment monitoring. In order to prolong the survival time of wireless monitoring network, the game theory is used to construct a distributed topology model. In order to solve the problem of network lifetime shortening caused by uneven energy consumption of nodes, the Theil index is introduced to improve the energy consumption balance of nodes, and a topology control algorithm for energy consumption balance (EBTCA) is proposed. Experiments show that the algorithm has good results in terms of network lifetime and energy balance.

Cause Analysis of Railway Traffic Accidents Based on Random Forest

With the rapid growth of the railway operation scale, all kinds of railway traffic accidents happen from time to time, so it is great significant to accurately identify the main influencing factors and their influence degree. In this paper, random forest model is proposed to analyze the cause of railway traffic accidents. Considering people, equipment, environment and other aspects, 11 influencing factors were extracted from 491 accident data. The influence degree of different factors on the severity of the accident is judged through variable importance measures of the random forest. On the basis of this, some suggestions are put forward for raising the safety level of railway transportation. The results show that the random forest model is accurate for analyzing the causes of railway traffic accidents, which can provide decision support for railway transportation safety management.

Effect of Water Vapor on Alumina Scale Growth Based on First-Principles Calculations

Despite much effort directed at elucidating the impact of water vapor on the high-temperature oxidation behavior of metallic materials, a complete understanding of its atomistic mechanisms remains ...

Discontinuities in Oxidation Kinetics: A New Model and its Application to Cr\u2013Si-Base Alloys

Some alloys such as many Cr-based systems show mass gain discontinuities during thermogravimetric measurements which strongly affect the oxidation kinetics. The behaviour cannot be described by the current models available in the literature. Thus, a novel k_mathrm{para}–k_mathrm{lin}-P-model was developed to describe oxidation kinetics during the isothermal exposure of materials which show such behaviour. Beside the parabolic rate constant k_mathrm{para} and the linear mass loss constant k_mathrm{lin}, the P-value and f_P are introduced to take into account spontaneous rapid mass gains due to local oxide scale failure. The parameter P serves as a measure for the mass gain due to discontinuous events and f_P is the frequency of such events. The both parameters can be related to oxide scale detachment and growth stresses. The application of the model is demonstrated for the oxidation of Cr–Si-based alloys in synthetic air at 1200^{circ }hbox {C} for 100 h. For these alloys, the origin of the mass gain discontinuities is discussed and the meaning of P and f_P is explained in more detail. Using this newly developed model, an insight into growth and nitridation resistance of oxide scales as well as scale adhesion is gained.

Testing predictions of electron scale turbulent pedestal transport in two DIII-D ELMy H-modes

In this paper, we present linear and nonlinear gyrokinetic analyses in the pedestal region of two DIII-D ELMy H-mode discharges using the CGYRO code. The otherwise matched discharges employ different divertor configurations to investigate the impact of varying recycling and particle source on pedestal profiles. Linear gyrokinetic simulations find electrostatic ion-scale instabilities (ion temperature gradient and trapped electron modes, ITG–TEM) are present just inside the top of the pedestal with growth rates that are enhanced significantly by parallel velocity shear. In the sharp gradient region, E × B shearing rates are comparable or larger than ion scale growth rates, suggesting the suppression of ITG–TEM modes in this region. Instead, the electron temperature profiles are found to be correlated with and just above the electron temperature gradient (ETG) instability thresholds. Using gradients varied within experimental uncertainties, nonlinear electron-scale gyrokinetic simulations predict electron heat fluxes from ETG turbulence, that when added to neoclassical (NC) ion thermal transport simulated by NEO, account for 30%–60% of the total experimental heat flux. In addition, the NC electron particle flux is found to contribute significantly to the experimental fluxes inferred from SOLPS-ITER analysis. Additional nonlinear gyrokinetic simulations are run varying input gradients to develop a threshold-based reduced model for ETG transport, finding a relatively simple dependence on η e = L ne/L Te. Predictive transport simulations are used to validate this pedestal-specific ETG model, in conjunction with a model for NC particle transport. In both discharges, the predicted electron temperatures are always overpredicted, indicative of the insufficient stiffness in the ETG pedestal model to account for all of the experimental electron thermal transport. In the case of the closed divertor discharge with lower particle source, the predicted electron density is close to the experiment, consistent with the magnitude of NC particle transport in that discharge. However, the density profiles are overpredicted in the open divertor discharge (larger particle source), due to insufficient model transport. The implications for other mechanisms accounting for the remainder of transport in the sharp gradient region in the two discharges are discussed.

Investigations on the Diffusion of Platinum between CMSX-4 Superalloy and Platinum-Enriched Bond Coat

The depletion of Pt in Pt-enriched bond coats due to inter-diffusion with superalloys has been a critical concern for the long-term oxidation resistance of thermal barrier coatings. This study investigated the diffusion behaviour of Pt between CMSX-4 superalloys and two commercial Pt-enriched bond coats comprising intermetallic γ′/γ-phase or β-phase, with the aim to understand the mechanism that leads to the depletion of Pt at high temperatures. The results demonstrated that the diffusion of Pt in superalloy disrupts its phase equilibrium, causes a significant lattice parameter misfit between the γ-phase and γ′-phase, and results in the formation of large γ′-grains with irregular shapes and random orientations. In addition, by using the Thermo-Calc software, Pt was found to have negative chemical interactions with both Al and Ta that stabilise Pt by decreasing its chemical activity. The depletion of Al due to the growth of Al2O3 scale during oxidation increases the activity of Pt and therefore accelerates the inwards depletion of Pt towards superalloys.

Internal Factors Affecting the Surface Rumpling of a β-NiAlHf Coating

β-NiAl coatings on a superalloy substrate will inevitably result in severe rumpling at elevated temperatures; however, the associated rumpling mechanisms are not completely understood. The scale rumpling behavior of a β-NiAlHf coating deposited by electron beam physical vapor deposition (EB-PVD) on single crystal superalloy IC21 was investigated in this work. Some internal factors, including the mismatch in the coefficient of thermal expansion and the stress induced by the growth of oxide scale and the phase transformation, were taken into consideration. The thermal mismatch stress between the coating and substrate was the main internal factor responsible for rumpling behavior during thermal cyclic loads, while the phase degradation from β-NiAl to γ’-Ni3Al in the coating played a dominant role during static thermal loads.