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Highlights • Self-heating tendency is reduced by densification with alkalis. • Alkali hydroxides reduce this tendency in the order Ca(OH) 2 < KOH < NaOH. • Surface area reduction depends on the size and charge of the exchanged cation. • Alkalis shift the mass loss stages of coal oxidation to higher temperatures. • NaCl addition forms a very brittle product, but has higher T cr than raw coal. Abstract Victorian Morwell coal's physico-chemical properties were modified through densification with Ca(OH) 2 , KOH, NH 4 OH and NaOH, in order to compare the effects of varying alkali metals addition on self-heating behaviour. The wire basket results showed that densification of brown coal with alkali hydroxides increased the critical ignition temperature in the order Ca(OH) 2 < KOH < NaOH relative to densified sample with NH 4 OH and without additive. The surface area and pore volume of all coal products densified with alkalis reduced. In addition, results showed that the size and charge of the exchanged cations play an important role in their interaction with coal oxygen functional groups, the extent of cross-linking network and consequently on the reduction of surface area of densified products with alkalis. Thermogravimetric analysis (TGA) results demonstrated a decrease in the proportion of the mass loss occurring at lower temperatures, and a shift to higher temperature in the main oxidation/decomposition stages, consistent with increasing the critical ignition temperature. Fourier transform infrared spectroscopy (FTIR) results suggested a catalytic role for cations (K > NH 4 > Na > Ca) in the formation of quinones during kneading of brown coal under alkaline conditions. The results revealed that the addition of alkalis to brown coal at basic pH improves the oxidation tolerance of the carboxylic/carboxylate groups and also enhances the polymerization and aromatization reactions during the thermal oxidation of coal, generating aromatic ether and/or ketone substituted polymers with higher thermal stability toward oxidation. Using NaCl as additive, at coal's natural acidic pH, resulted in a very brittle densified product, with higher macro and mesopore volumes than the coal densified prepared without additive. However, the T cr value increased, probably due to its lower micropore volume. [ABSTRACT FROM AUTHOR]

The Behabad district, located in the central Iranian microcontinent, contains numerous epigenetic stratabound carbonate-hosted Zn-Pb ore bodies. The mineralizations formed as fault, fracture and karst fillings in the Permian-Triassic formations, especially in Middle Triassic dolostones, and comprise mainly non-sulfides zinc ores. These are all interpreted as Mississippi Valley-type (MVT) base metal deposits. From an economic geological point of view, it is imperative to recognize the processes that have plausibly controlled the emplacement of MVT Zn-Pb mineralization in the Behabad district. To address the foregoing issue, analyses of the spatial distribution of mineral deposits comprising fry and fractal techniques and analysis of the spatial association of mineral deposits with geological features using distance distribution analysis were applied to assess the regional-scale processes that could have operated in the distribution of MVT Zn-Pb deposits in the district. The obtained results based on these analytical techniques show the main trends of the occurrences are NW–SE and NE-SW, which are parallel or subparallel to the major northwest and northeast trending faults, supporting the idea that these particular faults could have acted as the main conduits for transport of mineral-bearing fluids. The results of these analyses also suggest that Permian-Triassic brittle carbonate sedimentary rocks have served as the lithological controls on MVT mineralization in the Behabad district as they are spatially and temporally associated with mineralization. [ABSTRACT FROM AUTHOR]

The thermal behaviour and chemical structure of densified products of two Victorian brown coals prepared with NaOH addition were analysed by differential gravimetric analysis/differential thermal analysis (DGA/DTA) and Fourier transform infrared spectroscopy (FTIR). Acid washing of coal led to lower tendency to spontaneous combustion through a decrease in the total enthalpy change and a shift of the main mass loss stages to higher temperatures due to strengthening coal hydrogen bonding network. The addition of a small amount of NaOH (such that pH < 7.5) shifted the main stages of the DTG/DTA curves to lower temperatures and had a catalytic effect on spontaneous combustion by disrupting the hydrogen bonds network and suppressing cross-linking reactions. The products densified with higher amount of NaOH (such that pH ≥ 7.5) showed lower proportions of mass loss at lower temperatures stages of the DGA/DTA curves during oxidation with air. The ion exchange of Na ions for hydrogen in acid functional groups, increases the polarity and strength of bonds leading to a more rigid coal structure, reduces the surface area and decreases the coal’s tendency to react with oxygen and consequently delays the onset of combustion. FTIR results showed that the order of thermal vulnerability of brown coal’s functional groups toward decomposition/oxidation was as follows: aliphatic groups > carboxylic groups > carboxylate and aromatic groups > substituted aromatic groups ≈ polymerized ethers and ketones. [ABSTRACT FROM AUTHOR]

The spectrum–area (S–A) fractal model is a powerful tool for decomposition of complex anomaly patterns of gridded geochemical data. Ordinary moving average interpolation techniques are commonly being used for gridding geochemical data; however, these methods suffer from two major drawbacks of (1) ignoring the locally high values and (2) smoothing the interpolated surface. Multifractal moving average interpolation methods have been developed to overcome the shortcomings of ordinary moving average methods. This study seeks to compare two sets of multifractal and ordinary gridded geochemical data using success rate curves and applies the S–A fractal model to decompose anomalous geochemical patterns. A set of stream sediment geochemical data in Ahar area, NW Iran, was used as a case study. Then, a mineralization-related multi-element geochemical signature was gridded by ordinary and multifractal approaches and considered for further analyses. The S–A fractal method was applied to decompose anomaly and background components of the resultant multi-element geochemical signature. Exploration targets were delimited and further evaluated using two bivariate statistical procedures of Student's t-value and normalized density index. The results revealed that (a) application of multifractal gridded data enhances the predicting ability of geochemical signatures, (b) application of S–A fractal model on multifractal gridded data allows for superior discrimination of geochemical anomalies, and (c) the multi-element geochemical anomalies in the Ahar area related to porphyry-Cu deposits were properly delineated through sequence application of multifractal interpolation and S–A fractal model. [ABSTRACT FROM AUTHOR]

The process, where brown coal is extruded after mechanical kneading and then allowed to air dry slowly to form a product known as ‘densified coal’, was applied to reduce the moisture content of two Victorian brown coals. NaOH at different concentrations (0–1.5 M) was used as an additive in the kneading step. The spontaneous combustion propensity of the densified products was evaluated and compared against multiple physical properties and morphological features of materials. The densification process reduced the moisture content of the sample from around 60% to around 12%. NaOH addition led to a progressive reduction in the CO 2 surface area, as well as the porosity determined by mercury intrusion, due to the development of a stronger electrostatic network within the coal structure. The reduced micropore volume limits the accessibility of O 2 to internal surfaces of the coal leading to a significant increase in the critical ignition temperature (T cr ) measured by the wire basket test method. SEM imaging indicated that the coal particle surface changed from spongy and porous for nitrogen dried raw coal to very smooth and contiguous for densified coal. These trends also correlated with progressive reduction in the CO 2 surface area, as well as the porosity determined by mercury intrusion porosimetry. [ABSTRACT FROM AUTHOR]

The evolution of flow stress with imposed strain for an aluminum alloy (AA1100) processed by severe plastic deformation (SPD) has been described by utilizing three different models. The applied constitutive laws include a generalized three-dimensional dislocation density based model, a formulation based on the combination of the Estrin and Mecking model with an Avrami-type equation (EMA), and finally a relationship based upon the dimensional analysis using Pi-theorem. To verify the predicted flow stress, newly developed SPD process called multi-axial incremental forging and shearing (MAIFS) were performed from one to eight passes on the aluminum alloy workpieces. It was shown that the predictions of the EMA and Pi-theorem based models agreed well with the experimental trend of flow stress variations over a wide range of strain, and these models were able to address both hardening and softening observed at high strains. But, some modifications should be carried out on the dislocation density based model to give results with a reasonable agreement with the experimental data in the range of strain softening. The correct true stress–strain curves of each of eight passes after tensile test flow localization were firstly calculated according to a neck evolution model proposed by Segal et al. (2006). Then, a general descriptive constitutive equation for tensile flow behavior of the material after each pass of SPD process was developed based on an extension of the model originated from Pi-theorem. Furthermore, the severely deformed specimens kept fairly large total tensile elongation and for proving ductility, scanning electron microscopy observations of fracture surfaces were carried out. These observations indicated that the fracture surfaces were characterized by a dimple-like structure, which implied the existence of a ductile failure mode. [ABSTRACT FROM AUTHOR]

Dispersion pattern of geochemical elements in stream sediment data of a study area is affected by several factors, e.g., geological and geomorphological characteristics of the area. In this paper, we demonstrated recognition of efficient and inefficient mono-elemental geochemical signatures in a study area and exclusion of inefficient elements is worthwhile for increasing the probability of exploration success. For this, we adapted prediction-area (P-A) plot, normalized density and success-rate curve as tools that evaluate the ability of geochemical signatures in prediction of undiscovered mineral deposits and in delimiting exploration targets. After identification of efficient and inefficient elements, we combined efficient indicator elements to generate an effective prospectivity model. To illustrate the procedure we used a stream sediment data set for prospecting porphyry-Cu deposits in the Noghdouz area, Iran. [ABSTRACT FROM AUTHOR]

This study intends to (i) identify the potential sources of heavy metal (HM) pollution in an industrial town situated in the northwestern part of Iran and (ii) and assess whether the pollution levels discharged by HMs are significant. A suite of geochemical samples collected from the topsoil horizon of the study area were analyzed for HMs, namely Cr, Ni, Co, Cu, V, Zn, Mn, and Pb, to attain the objectives mentioned above. Compositional data analysis (CODA) techniques were employed for pinpointing the potential source of HM pollution. Initially, the centered log-ratio (clr) transformation was applied to the dataset containing raw values of chemically analyzed soil samples to address the data closure problem. Multifractal moving average interpolation was then applied to the clr-transformed data to model the spatial distribution of HMs in the study area. Maps of the spatial distribution of HMs in the study area were further classified by the concentration-area (C-A) fractal technique for identifying the potential hotspots of HM pollution in the area. It was followed by using the K-means clustering technique for classifying samples into distinct classes. This method was selected for geochemical pattern recognition owing to its simplicity and robustness in identifying subtle patterns embedded in geochemical data. The above hybrid methodology points to three anthropogenic sources discharging HM pollution into the area: leather factories, brickworks, and highways. Finally, pollution indices, namely the geo-accumulation index, pollution load index, and potential ecological risk, revealed that the elevated levels of Ni, Cr, and Co can pose serious impediments to the soil quality of the study area. [Display omitted] • A CODA-aided mapping and clustering approach applied to topsoil geochemical samples. • Heavy metal pollution were recognized to be linked to three anthropogenic sources. • Assessing heavy metal pollution levels by pollution indices. [ABSTRACT FROM AUTHOR]

After on-pump coronary artery bypass graft surgery, a patient had acute heparin-induced thrombocytopenia with thoracic arterial and venous thrombus formations. Complex emergency surgery with cardiopulmonary bypass and deep hypothermic circulatory arrest using bivalirudin anticoagulation was performed. [ABSTRACT FROM AUTHOR]

Abstract Stream sediments remain the preferred geochemical sampling media for regional mineral exploration programs in most parts of the world where there is a well-defined drainage system. In Au exploration the analysis of either Bulk Leach Extractable Gold (BLEG) or acid-extractable Au in the −80# (<180 μm) stream sediment fraction are the two most common approaches. Western Turkey contains a variety of mineral deposit types and geological settings. Using a geochemical database derived mainly from company exploration programs, a study is made on the efficiency of singularity mapping technique in detecting the known mineral deposits or prospects. The composite media of samples are representative of sampling locations but also are extremely diluted. Therefore, recognition and mapping of significant geochemical anomalies of composite media still remains a challenge. In this study, geochemical assay results were subjected to multifractal analyses to detect gold geochemical anomalies, which are related to gold mineralization. In this regard, a singularity mapping technique was applied to enhance the single element geochemical signatures of BLEG sand −80# stream sediment data. Since the singularity mapping technique does not define threshold values for delineation of anomalies, number-size (N-S) and concentration-area (C-A) fractal models were applied to delimit the geochemical anomalies as target areas for further exploration. A hundred percent of the known gold deposits and prospects discovered in the study area are delineated by BLEG Au stream sediment anomalies by N-S and C-A multifractal modeling. Moreover, 89% of known gold prospects of the study area are delineated within the recognized anomalous zones of Au in −80# stream sediment data. The comparison of the delineated geochemical anomalies of BLEG and −80# stream sediment with those of rock chip samples demonstrated the efficiency of the applied methodology. Graphical abstract Image 1 Highlights • Bulk leach extractable gold and −80# stream sediment sampling was carried out. • Concentration-area and number-size fractal modeling were applied. • Singularity mapping method was applied to delineate geochemical anomalies. • Singularity method applied to −80# stream sediments detected 90% of gold prospects. • Singularity method applied to BLEG also detected 100% of known gold prospects. [ABSTRACT FROM AUTHOR]

The development of microstructural banding and surface hot shortness during hot rolling in a 1.4 wt% Cu-bearing steel was studied. Different hot rolled states were produced by cross rolling, air cooling, and furnace cooling to investigate the effect of initial microstructure on the mechanical properties. It was revealed that to insure the hot workability of Cu-bearing steel against liquid metal embrittlement and prevention of the failure, a good practice is conducting hot working operations at temperatures below the melting point of copper to suppress the formation of liquid Cu-enriched phase that penetrates into grain boundaries. Cross rolling was found to be a promising approach to decrease the anisotropy of the rolled sheets resulted from the presence of the banded structure. Moreover, air-cooling yielded maximum strength due to its resultant fine and complex microstructure. These results can find application in processing and optimization of mechanical properties of steel sheets. [ABSTRACT FROM AUTHOR]

In this study, the sigmoidal kinetics of deformation-induced martensitic transformation (DIMT) in the transformation-induced plasticity (TRIP)-assisted alloys, including metastable high-entropy alloys (HEAs), austenitic stainless steels, and advanced high-strength steels (AHSSs) such as low-alloyed TRIP steels, medium-Mn steels, and quenching and partitioning steels, were studied using various models. To tune mechanical stability, the influences of stacking fault energy (SFE), chemical composition, austenite grain size, deformation temperature, strain rate, and stress state were considered. The novel Fe 47 Co 30 Cr 10 Ni 5 V 8- x Si x (x = 3, 4, and 6 at.%) alloys were the main investigated HEAs in the present work, in which silicon addition effectively led to lowering SFE and faster DIMT kinetics by promoting the formation of body-centered cubic α΄-martensite. The Olson-Cohen, Guimaraes (based on Johnson-Mehl-Avrami-Kolmogorov analysis), Shin, and Ahmedabadi models were analyzed and critically discussed. Moreover, a Hill-based sigmoid model was formulated as f α' / f sat = 1 – p / (p + ε q ) with the parameters p and q characterizing the stability of austenite, and f sat representing the saturated volume fraction of α΄-martensite. It was demonstrated that χ = p × q can be considered the sole austenite stability parameter. It was concluded that the proposed Hill-based model, demonstrating the highest accuracy among the studied models, can effectively simulate the kinetics of α΄-martensite formation. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: The method of severe plastic deformation (SPD) is often used to produce bulk ultrafine grained (UFG) metallic materials. SPD is a procedure, whereby the initial coarse grained structure of the material usually changes to deformed and UFG state. In the present study, a new SPD process called repetitive corrugation and straightening by rolling (RCSR) is introduced. A strain calculation method is then reported for inducing high strains after repetitive cycles in order to fabricate UFG metallic materials. RCSR consists of corrugated and flattened rolls. Changeable position of the workpieces during different routes, is of substantial capabilities of this procedure. Fe–10Ni–7Mn martensitic steel sheets were subjected to RCSR process. Optical and scanning electron microscopy along with mechanical testing investigation was used to systematically study the microstructure and mechanical properties of the workpieces. Microstructural study depicts micro-voids formation with average size of 100–150nm. The spherical morphology appeared mostly along the laths, resulted from the non-equilibrium grain boundaries. [Copyright &y& Elsevier]

A simple framework was proposed for quantitative characterization and modeling of composite microstructures, in which the degree of particle distribution homogeneity, the mean spacing between particles, the average particle size, and the volume fraction of particles are appropriately integrated into the model. One of the main prospects of this technique is quantifying the degree of inhomogeneity of particle distribution, which is essential during processing and post-processing of metal-matrix composites (MMCs) for structural refinement. The outcome of the developed model based on experimental verification was promising and it is anticipated that this model finds applications in improving the fabrication process of MMCs, especially where a comparative study has to be conducted. [ABSTRACT FROM AUTHOR]