Solution Structure Research Articles

Electronic analysis of n-propyl xanthate complexes with group 12 metals: a theoretical-experimental study.

Xanthates are organic compounds of great interest in coordination chemistry due to their different basic sites, which allow them to form complexes with different coordination modes and geometries. These compounds are relevant in the environment and act as heavy metal collectors in aqueous environments. In this theoretical-experimental work, electronic spectroscopy studies of n-propyl xanthate complexes with group 12 metals were performed. This study verified structural differences in these systems, depending on the environment in which they are inserted. In addition, structural differences were observed when the solid was changed to an n-hexane solution. Thus, it was observed that the complexes assume a mononuclear structure in solution, while they present a polymeric form in the solid phase. The electronic spectra obtained through TD-DFT calculations were compared to those of the previously synthesized complexes. In the final theoretical analysis, the main orbitals involved in these transitions were assigned using population analysis calculations. The synthesis of the complexes was confirmed through infrared (MID and FAR), UV‒Vis, Raman, and NMR-1H spectroscopic analyses. The structures of the mononuclear and polymeric complexes were optimized in vacuum and n-hexane. Under vacuum, DFT levels M06L/6-311 + + G** + LANL2TZ and M06L/def2-TZVP were used for the mononuclear complexes, and M06L/LANL2DZ + LANL2 were used for the polymer complexes. For the calculations of the mononuclear complexes in n-hexane, the same level of theory was used for the solid state. TD-DFT calculations for 300 excited states were performed with the same levels of theory and used the optimized structures of the complexes. Furthermore, population analysis was carried out on all the systems studied. Gaussian 09 software was used for the structure optimization, TD-DFT, and population analysis calculations. GaussSum software was used to evaluate the molecular orbitals and electronic spectra.

An evaluation of the psychometric properties of the Australian Collaborative Practice Assessment Tool

Objectives This study aimed to validate the Collaborative Practice Assessment Tool (CPAT) in the Australian setting and provide a quality instrument in terms of psychometric properties that can be used to measure interprofessional outcomes for both healthcare practitioners and students. The outcomes evaluated include the capacity to work in an interprofessional team, good interprofessional communication skills, leadership skills, ensuring clear division of tasks and roles in a team, effective conflict management, and being actively involved with patients and their families/communities in care. Methods The COSMIN (COnsensus-based Standards for the selection of health Measurement INstruments) taxonomy and standards were used as guides for evaluating the psychometric properties of the Australian CPAT, which include evaluations regarding instrument development requirements of sample target and size, content validity, internal structure (structural validity, internal consistency reliability and measurement invariance), and hypotheses testing. CPAT Australia was developed through two stages involving pilot studies and a validation study, both of which included healthcare practitioners and students as participants. A pilot study examined content validity regarding item relevance, item comprehensibility, and instrument comprehensiveness. The validation study was carried out to assess the internal structure of CPAT Australia for aspects of structural validity, internal consistency reliabilities, and configural, metric and scalar measurement invariance. The structural validity was explored using the following three steps: exploratory, confirmatory, and multi-group factor analysis. Construct validity was evaluated to confirm direct and indirect paths of assumptions based on a previously validated model. Data collected between August 2021 and May 2022. Results The content validity evaluation confirmed that all items were relevant, understandable and comprehensive for measuring interprofessional collaborative care in Australia. Three hundred ninety-nine participants contributed to the validation study (n=152 practitioners; n=247 students). The original instrument model of 8-Factor 56-Item was improved in the Australian CPAT. Two items, Item 27 (Physicians assume the ultimate responsibility) and Item 49 (Final decision rest with the physician), were consistently rejected and therefore discarded. The internal structure of the 7-Factor 54-Item solution was confirmed as a suitable model with fit indices meeting COSMIN standards for a good model in practitioner and student cohorts. Configural, metric and scalar invariances were confirmed, indicating the invariance of the instruments when used for the practitioner and student cohorts. The construct validity evaluation indicated that 81.3% of direct and indirect assumptions were accepted, fulfilling the COSMIN requirement of >75% of proposed assumptions being accepted. Conclusion The Australian CPAT with a 7-factor 54-item solution was confirmed as a quality measure for assessing interprofessional education and collaborative practice for both healthcare practitioners and students in Australia with robust psychometric properties.

On the investigation of fractional coupled nonlinear integrable dynamical system: Dynamics of soliton solutions

The primary focus of this paper is the investigation of the truncated M fractional Kuralay equation, which finds applicability in various domains such as engineering, nonlinear optics, ferromagnetic materials, signal processing, and optical fibers. As a result of its capacity to elucidate a vast array of complex physical phenomena and unveil more dynamic structures of localized wave solutions, the Kuralay equation has received considerable interest in the scientific community. To extract the solutions, the recently developed integration method, referred to as the modified generalized Riccati equation mapping (mGREM) approach, is utilized as the solving tool. Multiple types of optical solitons, including mixed, dark, singular, bright-dark, bright, complex, and combined solitons, are extracted. Furthermore, solutions that are periodic, hyperbolic, and exponential are produced. To acquire a valuable understanding of the solution dynamics, the research employs numerical simulations to examine and investigate the exact soliton solutions. Graphs in both two and three dimensions are presented. The graphical representations offer significant insights into the patterns of voltage propagation within the system. The aforementioned results make a valuable addition to the current body of knowledge and lay the groundwork for future inquiries in the domain of nonlinear sciences. The efficacy of the modified GREM method in generating a wide range of traveling wave solutions for the coupled Kuralay equation is illustrated in this study.

The isosbestic point in the Raman spectra of the hydration shell

Isosbestic point is often observed in a series of spectra, but their interpretation is still controversial, such as whether the continuum model can produce an isosbestic point. In order to answer this question, the Raman spectra of hydration shell with continuous distribution structure in different ionic aqueous solutions were separated by Raman ratio spectra, and an isosbestic point was successfully observed. Our experimental results show that the continuum model can indeed produce the isosbestic point. In order to deepen the understanding of the isosbestic point, we calculate the first moment of the Raman spectra and conduct molecular dynamics (MD) simulations. Both experimental and theoretical findings indicate that elevated temperatures lead to increased disorder among water molecules within the hydration shell.

Probing Isolated Water Molecules in Aqueous Acetonitrile Solutions Using Oxygen K-Edge X-ray Absorption Spectroscopy.

Oxygen K-edge X-ray absorption spectroscopy (XAS) of an aqueous acetonitrile solution exhibited a sharp peak at approximately 537 eV, which was similar to that of water vapor and was not observed in liquid water. The inner-shell spectra of isolated water molecules and water clusters of different sizes surrounded by acetonitrile molecules were obtained by extracting these water structures from the liquid structures of aqueous acetonitrile solutions, as calculated using molecular dynamics simulations. The sharp peak profiles of the O K-edge XAS spectra were derived not from water clusters but from isolated water molecules surrounded by acetonitrile molecules. The present study proposes that isolated water molecules are easily formed in aqueous acetonitrile solutions and that the electronic structures of the isolated water molecules can be analyzed using O K-edge XAS spectra, which separates the contributions of small water clusters.

Imagining and implementing healthy city interventions: Combined results from parallel concept mapping exercises in Montreal with community members and stakeholders.

Built environment interventions provide structural solutions to complex urban challenges. Though community voices are part of municipal decision-making, planners and public health professionals need tools to better integrate their perspectives for desired changes (what) when implementing built environment interventions (how). We present two simultaneous concept mapping exercises conducted in Montréal, Canada, to facilitate the consideration of these dimensions. Community members were prompted about neighbourhood changes that could improve their quality of life; stakeholders were prompted about factors that contribute to successful implementation of interventions. Through each exercise, items were generated, grouped, and rated on importance and feasibility. Concept maps were produced using multidimensional scaling and hierarchical cluster analysis. The clusters identified by community members and stakeholders were combined into a Community × Stakeholder Matrix, which supported discussions on interventions with the research's Advisory Committee. Thirty-two community members generated 41 responses, which resulted in 6 clusters: (1) strengthen public transportation, (2) reduce space dedicated to cars, (3) foster local social connections, (4) develop quality cycling infrastructure, (5) improve pedestrian accessibility, and (6) green the city. Thirty-seven stakeholders generated 40 items, which resulted in 5 clusters: (1) collaboration with stakeholders and citizens, (2) planning and evaluation, (3) common vision for the future, (4) regulatory framework and funding, and (5) context-informed approach. Capturing the collective vision of our urban environments and the processes underlying change through concept mapping can lead to more successful changes. We propose combining understandings of the what and how into a matrix to support evaluation and strategic planning of interventions and better integrate community voices into operational planning.

Rational design of the aerodynamic rudder structure taking into account strength, rigidity and aeroelastic stability

The paper considers a design process of an aerodynamic rudder, which structure comprises the skin of constant thickness, a load-bearing structure and a trimmed nose that plays the role of an anti-flutter balancer. The aim of the work is to set and solve the design problem of a rational structural and technological solution of the rudder that meets the requirements of strength, rigidity, aeroelastic stability and minimum mass. To solve this problem, a design algorithm for the rudder, using topological and parametric optimization, is proposed. The main parameters of the design area and the trimmed nose required for topological optimization are determined. The ANSYS Workbench software package was used for the finite element analysis and topological optimization. Based on the results of optimization, post-processing was carried out. A structural and technological solution, that combines structural layouts with constant and variable width of the trimmed nose, was proposed. An analysis of the stress-strain state was carried out, and it was found that the designed structure meets the strength requirements for the given design case. A scheme for solving the parametric optimization problem of the rudder under the condition of aeroelastic stability is proposed. Within the framework of solving this problem, a flutter study was conducted, using a multi-mode model, which makes it possible to study the rudder and body-rudder flutter forms of an unmanned aerial vehicle (UAV) equipped with aerodynamic rudders. The results of the flutter study for the design mode of the UAV flight are obtained in the form of dependencies of the critical flutter velocity and frequency on the average width of the trimmed nose. The analysis of these dependencies allowed us to derive the optimal values of the trimmed nose parameters from the minimum weight condition for two rudder configurations: with a constant and variable width of the trimmed nose.

The Micron-Droplet-Confined Continuous-Flow Synthesis of Freestanding High-Entropy-Alloy Nanoparticles by Flame Spray Pyrolysis.

Alloying multiple immiscible elements into a nanoparticle with single-phase solid solution structure (high-entropy-alloy nanoparticles, HEA-NPs) merits great potential. To date, various kinds of synthesis techniques of HEA-NPs are developed; however, a continuous-flow synthesis of freestanding HEA-NPs remains a challenge. Here a micron-droplet-confined strategy by flame spray pyrolysis (FSP) to achieve the continuous-flow synthesis of freestanding HEA-NPs, is proposed. The continuous precursor solution undergoes gas shearing and micro-explosion to form nano droplets which act as the micron-droplet-confined reactors. The ultrafast evolution (<5ms) from droplets to <10nm nanoparticles of binary to septenary alloys is achieved through thermodynamic and kinetic control (high temperature and ultrafast colling). Among them, the AuPtPdRuIr HEA-NPs exhibit excellent electrocatalytic performance for alkaline hydrogen evolution reaction with 23mV overpotential to achieve 10mA cm-2, which is twofold better than that of the commercial Pt/C. It is anticipated that the continuous-flow synthesis by FSP can introduce a new way for the continuous synthesis of freestanding HEA-NP with a high productivity rate.

New Phases in the Sc−Mn−Si and Sc−Mn−Al−Si Systems Through Molten Indium Flux Synthesis

AbstractThrough the application of synthesis via molten indium flux, we have been able to expand the ternary Sc−Mn−Si system and the quaternary Sc−Mn−Al−Si system. Specifically, we report on five previously unknown chemical compounds, namely β‐ScMnSi2, Sc4+xMn4Si7–2x, Sc2Mn4Si5, Sc2Mn3Si4, and Sc4Mn2AlSi4. The compounds with the stoichiometries Sc2Mn4Si5, Sc2Mn3Si4, and Sc4Mn2AlSi4 have previously not been reported. We find that these crystallize in the V6Si5, Hf2Ru3Si4, and Ho4Ni2InGe4 structure types, respectively. For the ternary compounds with the stoichiometries of ScMnSi2 and Sc4+xMn4Si7–2x, we find clearly deviating structural solutions compared to earlier reports. β‐ScMnSi2 is found to crystallize in the monoclinic crystal system isostructural to a supercell of the MnTiSi2 structure and clearly deviating from the known orthorhombic α‐polymorph. The compound Sc4+xMn4Si7–2x is structurally very similar to Sc4Mn4Si7, but exhibits the P4/nmm space group instead of I4/mmm, and is related to the Zr4Co4Ge7 structure. Disorder between Si and Sc sites leads to the off‐stoichiometric composition, for which we found x=0.287(5).

Psychological distress mediates the link between bullying and truancy in Australian LGBQ+ adolescents with experiences of homelessness

ABSTRACT Homelessness is a high prevalence experience among lesbian, gay, bisexual, and queer (LGBQ+) youth, and potentiates both significant morbidity and future homelessness. While educational attainment is cited as a structural solution to homelessness, limited research exists on homeless LGBQ+ youths’ schooling experiences. A nationwide, cross-sectional survey involving 4,370 cisgender LGBQ+ participants aged 14–21 was conducted to address this gap. Regression analyses showed previous homelessness was associated with an increased odds of verbal, physical and sexual bullying and harassment within school contexts. Mediation analyses confirmed the mediating role of psychological distress on the associations between physical and sexual harassment and truancy, regardless of past homelessness. Previous experiences of homelessness are not associated with increased distress in relation to bullying or harassment. However, the indirect effect of harassment on truancy was significantly more pronounced for youth with past homelessness. Our findings crucially suggest that bullying presents both direct and indirect structural risks to cisgender LGBQ+ youth, and is particularly inconducive to continued engagement with schooling for youth with experiences of homelessness. Interventions aiming to address truancy among this group should aim to reduce the incidence of bullying within educational settings, whilst also providing assistance for managing the challenges associated with experiencing homelessness.

New long tail gemini surfactant in aqueous solution: Self-assembly, rheological properties and responsiveness to hydrocarbon

Gemini surfactants are promising to replace conventional monomeric surfactants in various applications. In this paper, a new gemini surfactant with long unsaturated oleyl tails and bis(hydroxyethyl) ammonium head groups linked by butyl spacer was synthesized. Its critical micelle concentration in salt-free water (12 µM) is much lower than for its monomeric analog (220 µM). Without any additives this surfactant can form viscoelastic solutions with the viscosity of up to 1 kPa·s and elastic modulus of 15 Pa at the conditions, when the viscosity of the single-chained monomeric analog is close to that of pure water. These are one of the highest values reported so far for C18-tailed gemini surfactants without additives. The structure of the gemini surfactant solutions was studied by cryo-TEM and SAXS. Cryo-TEM revealed the presence of closed-looped micelles coexisting with linear wormlike micelles as well as the regular spacing between the micelles arising from strong electrostatic repulsion between them. The SAXS curves were well-fitted by a form-factor of core–shell cylinder, which yielded the radius of the core and the thickness of the shell equal to 1.4 nm each. Addition of n-decane induced the drop of viscosity by 6 orders of magnitude accompanied by the transformation of wormlike micelles into microemulsion droplets with 4.4 nm radius. Such gemini surfactants providing high viscoelasticity to aqueous solution that is responsive to added hydrocarbon are promising for the application in oil recovery as thickeners of fracturing fluids that can be cleaned up without any breakers at the backflow of oil.

Research on lightweight design method of diesel engine steel piston based on heat transfer characteristics

Steel pistons are gradually replacing traditional aluminum–silicon alloy pistons as the preferred choice for high-power density engines. However, there is still a lack of systematic research on the heat transfer characteristics of steel pistons in the field of small bore diesel engines. For this reason, this paper was based on the storage temperature testing system to study the variation of temperature field and thermal stress in steel pistons of the small-bore diesel engine under the maximum torque conditions. The results show that there are significant temperature variations in the circumferential path of the steel piston head, indicating that the temperature distribution of the steel piston is highly uneven. The highest temperatures and maximum thermal stresses were found in the rim. To further achieve the lightweighting of the steel piston, a lightweight design method based on heat transfer characteristics was proposed. A multi-objective optimization algorithm was used to optimize the top land height and the position and shape of the cooling gallery. The structural design solutions with volume and thermal stress control were finally obtained. The optimized design solution can reduce the mass by a maximum of 10.01 %, the maximum temperature by a maximum of 35.04 °C and the maximum thermal stress by a maximum of 18.38 % compared to the original design.

Impact of pilot-scale microfluidization on soybean protein structure in powder and solution

The effect of microfluidization treatment on the primary, secondary, and tertiary structure of soybean protein isolate (SPI) was investigated. The samples were treated with and without controlling the temperature and circulated in the system 1, 3, and 5 times at high pressure (137 MPa). Then, the treated samples were freeze-dried and reconstituted in water to check the impact of the microfluidization on two different states: powder and solution. Regarding the primary structure, the SDS-PAGE analysis under reducing conditions showed that the protein bands remained unchanged when exposed to microfluidization treatment. When the temperature was controlled for the samples in their powder state, a significant decrease in the quantities of β-sheet and random coil and a slight reduction in α-helix content was noticed. The observed decrease in β-sheet and the increase in β-turns in treated samples indicated that microfluidization may lead to protein unfolding, opening the hydrophobic regions. Additionally, a lower amount of α-helix suggests a higher protein flexibility. After reconstitution in water, a significant difference was observed only in α-helix, β-sheet and β-turn. Related to the tertiary structure, microfluidization increases the surface hydrophobicity. Among all the conditions tested, the samples where the temperature is controlled seem the most suitable.

Tuning the Solvation Structure in Water-Based Solution Enables Surface Reconstruction of Layered Oxide Cathodes toward Long Lifespan Sodium-Ion Batteries.

Layered oxides of sodium-ion batteries suffer from severe side reactions on the electrode/electrolyte interface, leading to fast capacity degradation. Although surface reconstruction strategies are widely used to solve the above issues, the utilization of the low-cost wet chemical method is extremely challenging for moisture-sensitive Na-based oxide materials. Here, the solvation tuning strategy is proposed to overcome the deterioration of NaNi1/3Mn1/3Fe1/3O2 in water-based solution and conduct the surface reconstruction. When capturing the water molecules by the solvation structure of cations, here is Li+, the structural collapse and degradation of layered oxides in water-based solvents are greatly mitigated. Furthermore, Li(H2O)3EA+ promotes the profitable Li+/Na+ exchange to build a robust surface, which hampers the decomposition of electrolytes and the structural evolution upon cycling. Accordingly, the lifespan of Li-reinforced materials is prolonged to three times that of the pristine one. This work represents a step forward in understanding the surface reconstruction operated in a water-based solution for high-performance sodium layered oxide cathodes.

A systematic investigation of solution and technological parameters for the fabrication and characterization of poly (vinyl alcohol–chitosan electrospun nanofibers

AbstractNanomaterials, particularly nanofibers are demonstrating exceptional potential for medical applications considered as promising systems for the integration of drug molecules, providing an enhancement of drug effectiveness and safety, while reducing drug side effects. Nanofibers based on two polymeric matrices poly(vinyl alcohol) (PVA) and chitosan (CS) have been demonstrated to be safe and promising materials for the drug integration and targeted drug delivery. This article studied the factors influencing on the fabrication and properties of PVA–CS nanofibers, including the impact of solution components on solution structure, rheological properties, electrospinning technology parameters, as well as the structure and thermomechanical properties of the obtained nanofibers have been investigated in details. The increasing of acetic acid concentration has the effect of pH lowering as well as electrical conductivity while heightening its viscosity. The pH, conductivity, and viscosity values of the solution rises as the CS concentration increases. Based on the Hildebrand‐Scatchard solubility theory, calculated Teas diagrams that account intermolecular interactions allow to predict low‐defect nanofibers based on PVA–CS in binary solvent systems with a greater concentration of hydrogen bonds. The optimal solution content and electrospinning parameters were determined. Infrared spectroscopy confirmed that the two polymer materials have a good interaction and the acetic acid was completely separated from the PVA–CS nanofibers. The XRD spectrum reveals that the crystal lattice parameters of the nanofibers change according to the polymer ratio. The polymers ratio also influence on the thermal and tensile properties. Such biosafe polymer materials may be considered as the promising drug delivery systems with the targeted mode of action.

Structure and Non-reactive Dynamics of the Dimeric Catalytic Domain of Human Carbonic Anhydrase IX

Despite the availability of high resolution crystal structure of the catalytic domain of human carbonic anhydrase IX (HCA IX-c), its solution structure and functional dynamics are mostly unknown. In this article, we report classical molecular dynamics (MD) simulation studies on the structure and non-reactive dynamics of dimeric HCA IX-c (d-HCA IX-c, with chains A and B) in water and compare them to each chain simulated in water as a monomeric solute (mA/mB). While the average solution structures appear to be largely similar in all systems, d-HCA IX-c shows significant deviations from mA and mB in terms of non-reactive reorganization of the active site needed to initiate the rate determining proton transfer step between a zinc-bound water and one of the sidechain N-atoms of a distal histidine residue (His-64). First, 2−6 water molecules are found to form fluctuating hydrogen bonded networks that would serve as proton paths across the active site. A minimally frustrated core of each monomer in the dimeric protein is found to be associated with a significantly higher likelihood of forming complete proton transfer pathways mediated by 2 water molecules synchronously at the two active sites hosted by the monomeric chains. The relative stability and kinetics of transition between two major sidechain rotamers of His-64 are also found to be affected by dimerization. The sidechain rotation of His-64 is found to involve at least one transition as slow as 105 per second in chain A of d-HCA IX-c thereby rendering it slower than the actual rate determining proton transfer step and suggests important deviation from the widely accepted mechanism of catalysis by HCAs.

Reaction calorimetry and structural crystal properties of non-ideal binary rhabdophane solid solutions (Ce1−xREExPO4·nH2O)

Rhabdophane is a hydrous phosphate that commonly replaces monazite as a weathering product in critical mineral deposits during the alteration of rare earth elements (REE) bearing carbonatites and alkaline igneous complexes. It is an important host to the light (L)REE (i.e., La to Gd) but the stability and structure of binary solid solutions between the Ce and the other LREE endmembers have not yet been determined experimentally. Here we present room temperature calorimetric experiments that were used to measure the enthalpy of precipitation of rhabdophane (Ce1−xREExPO4·nH2O; REE = La, Pr, Nd, Sm, Eu, and Gd). The solids were characterized using X-ray diffraction, scanning electron microscopy, Raman spectroscopy, and the role of water in the rhabdophane structure was further determined using thermogravimetric analysis coupled with differential scanning calorimetry. The calorimetric experiments indicate a non-ideal behavior for all of the binary solid solutions investigated with an excess enthalpy of mixing (ΔHex) described by a 2- to 3-term Guggenheim parameters equation. The solid solutions were categorized into three groups: 1) binary Ce-La and Ce-Pr which display positive ΔHex values with a slight asymmetry; 2) binary Ce-Nd and Ce-Sm which display negative ΔHex values with a nearly symmetric shape; 3) Ce-Eu and Ce-Gd which display both negative and positive ΔHex values with nearly symmetric shape. The excess Gibbs energy (ΔGex) of the solid solutions was further investigated using a thermodynamic analysis approach of aqueous-solid solution equilibria and the optimization programs GEMS and GEMSFITS. The resulting ΔGex values combined with the calorimetric ΔHex values indicate that there is likely an excess entropy contribution implying important short-range structural modifications in the solid solutions dependent on the deviation of the REE ionic radii from the size of Ce3+. These observations corroborate with the trends in the Raman v1 stretching bands of the PO4-site. The excess molar volumes determined from X-ray diffraction analysis further indicate an overall asymmetric behavior in all of the studied binary solid solutions, which becomes increasingly important from La to Gd. The pronounced short-range order–disorder occurring in groups 2 and 3 solid solutions mimics some of the behavior observed from previous studies in anhydrous monazite solid solutions. This study highlights the potential to use the chemistry and the structural modifications of rhabdophane as potential indicators of formation conditions in geologic systems and permits improving our modeling capabilities of REE partitioning in critical minerals systems.

A mathematical model for flow field with condensation discontinuity: One‐dimensional Euler equations with singular sources

Condensation induces both heat addition and mass consumption effects on the carrier flow field, leading to complex wave patterns. In this study, we aim to elucidate the structures of flow field under the influence of condensation. To achieve this, we present a mathematical model, which is formulated using Euler equations with a singular source term. Given the difficulties posed by both weak solution theory and the Dal Maso–LeFloch–Murat (DLM) theory (J. Math. Pures Appl. 483‐548 (1995)) in defining solutions to the Riemann problem, we propose a novel approach. This involves the coupling of weak solutions within two subregions, taking into consideration the discontinuity of source term. Firstly, we identify two stationary discontinuities originating from the singular source term—namely, stationary waves and composite waves. Admissibility criterions are developed for these discontinuities to facilitate the selection of physically meaningful solutions. Secondly, we employ a double classical Riemann problems (CRPs) framework to analyze the structures of Riemann solution. Our analysis reveals that the Riemann solution may exhibit seven structures with stationary wave and four structures with composite wave. Finally, the proposed model and its theoritical results are applied to validate the structure of the flow field with condensation discontinuities. For the pure heat addition problem, we successfully demonstrate all wave patterns of the flow field, perfectly matching the outcomes of numerical experiments.

On thermal and strain-rate dependences of polymethacrylimide (PMI) foam materials

Polymethacrylimide (PMI) foams exhibit great potentials in engineering applications thanks to its outstanding lightweight and superior mechanical properties. However, the temperature and loading rate can greatly affect its mechanical behaviors, which are the key factors in analysis and design of the PMI foam structures for practical applications. Unfortunately, there is lack of fundamental data and constitutive models available concerning the elastic-plastic properties of the PMI foam in various stress states at different ambient temperatures and different strain rates. Therefore, this study aims to fill this knowledge gap by generating basic experimental data and providing a generic modeling solution for PMI foam materials and structures. To better reflect the actual service conditions in practice, different stress states are considered under different temperatures and strain rates. The cyclic loads are applied to characterize the actual mechanical responses of the PMI foam where the initial and subsequent yield surfaces were calibrated and analyzed. Following the experimental results, the elasticity, plasticity, viscosity and damage of the PMI foam are investigated thoroughly, especially for the initial and subsequent yielding behaviors. Further, the thermal and strain rate dependent constitutive models are established and calibrated based on the in-house experimental data for finite element (FE) modeling. A novel damage model is proposed to replicate the phenomenon of the stiffness degradation in compression. It is found that accurate predictions on the mechanical responses of PMI foam can be achieved under different temperatures and strain rates. This study is anticipated to provide fundamental experimental data and effective constitutive models of PMI foam for real engineering applications, such as lightweight design of sandwich structures under some harsh conditions.

Novel comprehensions of lithological and structural features gleaned via Sentinel 2 texture analysis

Detailed geological mapping is the decisive key for mineral deposit prospecting, deciphering tectonic models, and outlining the main framework for most development programs and constructions. Without a doubt, various remote sensing datasets have introduced reliable lithological and structural mapping solutions. The main defect with remote sensing data is the curse of dimensionality, especially with hyperspectral data, where a lot of time is spent handling and selecting representative bands for various geological analyses. Consequently, and for the first time, our research is an attempt to resolve the complicated structural patterns (lineaments, folds, foliations, and cross-cutting relationships) and enhance lithological discrimination using a single band (of Sentinel 2 and ALOS PRISM data) and textural analysis. Through several trials over different pixel sizes (2.5 m and 10 m) and various kernels (3 × 3, 7 × 7, or 11 × 11), reasonable results are obtained, enabling lithological discrimination, in-depth structural analysis (foliations, faults, joints, and folds), shape recognition of systematic rock bodies, and delineation of quaternary deposits using single band analysis rather than time-consuming multiple band processing. Our results have been verified using intensive fieldwork and accurate visual interpretations using different datasets (e.g., previous geological maps, remote sensing data, etc.). Upon field verification and petrographical investigations of this research outcomes, we strongly recommend the adopted approach for the geological community, as it opens the doors for various applications utilizing single-band second-order statistics. We expect that this research could significantly help the geological community by reviving several previous studies and being applicable for future research, besides offering a reasonable approach for minimizing the time and efforts required for detailed field studies by highlighting micro- and mesoscale structures.