This report describes a 2nd place solution of the detection challenge which is held within CVPR 2... more This report describes a 2nd place solution of the detection challenge which is held within CVPR 2020 Retail-Vision workshop. Instead of going further considering previous results this work mainly aims to verify previously observed takeaways by re-experimenting. The reliability and reproducibility of the results are reached by incorporating a popular object detection toolbox-MMDetection. In this report, I firstly represent the results received for Faster-RCNN and RetinaNet models, which were taken for comparison in the original work. Then I describe the experiment results with more advanced models. The final section reviews two simple tricks for Faster-RCNN model that were used for my final submission: changing default anchor scale parameter and train-time image tiling. The source code is available at https://github.com/tyomj/product_detection.
<p>A more accurate characterization of the sources and sinks of methane (CH... more <p>A more accurate characterization of the sources and sinks of methane (CH<sub>4</sub>) and carbon dioxide (CO<sub>2</sub>) in the vulnerable Arctic environment is required to better predict climate change. A large-scale aircraft campaign took place in September 2020 focusing on Siberian coast. CH<sub>4</sub> and CO<sub>2</sub> were measured in situ during the campaign and form the core of the study. Measured ozone (O<sub>3</sub>) and carbon monoxide (CO) are used here as tracers. Compared to the reference (i.e., the seasonal value at Mauna Loa, Hawaii, US), median CH<sub>4</sub> mixing ratios are fairly higher (1890-1969 ppb vs 1887 ppb) while CO<sub>2</sub> mixing ratios from all flights are lower (408.09-411.50 ppm vs 411.52 ppm). We also report on 3 case studies. Our analysis suggests that during the campaign the European part of Russia’s Arctic and Western Siberia were subject to long-range transport of polluted air masses, while the East mainly was under the influence of local emission of greenhouse gases. The relative contributions of anthropogenic and natural sources of CH<sub>4</sub> in Siberia are simulated using the Lagrangian model FLEXPART in order to identify dominant sources in the boundary layer and in the free troposphere. In western terrestrial flights, air masses composition is influenced by from wetlands and anthropogenic activities (waste management, the fossil fuel industry and to a lesser extent the agricultural sector), while in the East, emissions are dominated by freshwaters, wetlands, and the oceans, with an ambiguous contribution from likely anthropogenic sources related to fossil fuels. Our results generally highlight the importance of the contribution form freshwater and oceans emissions and, combined with the large uncertainties associated with them, suggest that the emission from these aquatic sources should receive more attention in Siberia.</p>
<p>Aerosols play an important role in radiation processes in the atmosphere... more <p>Aerosols play an important role in radiation processes in the atmosphere, as well as they have a significant impact on global and regional air quality. The process of the atmospheric nanoparticle formation starts from in situ conversion of condensable vapors. Then, the freshly formed nanometer-size clusters begin to grow due to the condensation of nucleating vapours on them and a self-coagulation as well, thus reaching the optically active size ranges. The relative contribution of the above mechanisms can be estimated by the chemical composition of size-segregated particles. Here, we present preliminary results of the analysis of aerosol samples characterizing the inorganic chemical composition of particles ranging from a few nm to 10 mm. The sampling was performed at Fonovaya Observatory (West Siberia) in October 2021 by means of the Model 125R Nano-MOUDI Impactor.</p><p>The analysis showed that in the lowest size range (<10 nm), only five ions were detected: SO<sub>4</sub><sup>2-</sup>, Cl<sup>-</sup>, K<sup>+</sup>, Na<sup>+</sup>, H<sup>+</sup>. The growth of the nucleation mode particles to the size range of 60-100 nm was accompanied by increasing content of SO<sub>4</sub><sup>2-</sup>, Na<sup>+</sup>, H<sup>+</sup> ions to 50, 37 and 13%, respectively, suggesting the condensation of H<sub>2</sub>SO<sub>4</sub> vapours or the coagulation of particles contained mainly Na<sub>2</sub>SO<sub>4</sub>. A content of ammonium ions (NH<sub>4</sub><sup>+</sup>) appeared to be significant only in the accumulation mode size range (0.1-1.0 mm). Nitrates (NO<sub>3</sub><sup>-</sup>) were detected mainly in the Aitken mode particles and then their contribution increases in accumulation and coarse mode ranges.</p><p>This work was supported by the RFBR grant No. 19-05-50024 (Microparticles in the atmosphere: formation and transformation in the atmospheric surface layer and in the free troposphere, radiation effects and impact on public health).</p>
Lobachevsky University Electrocardiography Database (LUDB) is an ECG signal database with marked ... more Lobachevsky University Electrocardiography Database (LUDB) is an ECG signal database with marked boundaries and peaks of P, T waves and QRS complexes. The database consists of 200 10-second 12-lead ECG signal records representing different morphologies of the ECG signal. The ECGs were collected from healthy volunteers and patients of the Nizhny Novgorod City Hospital No 5 in 2017-2018\. The patients had various cardiovascular diseases while some of them had pacemakers. The boundaries of P, T waves and QRS complexes were manually annotated by cardiologists for all 200 records. Also, each record is annotated with the corresponding diagnosis. The database can be used for educational purposes as well as for training and testing algorithms for ECG delineation, i.e. for automatic detection of boundaries and peaks of P, T waves and QRS complexes.
Communications in Computer and Information Science, 2017
Knowledge graph management use cases often require addressing hybrid information needs that invol... more Knowledge graph management use cases often require addressing hybrid information needs that involve multitude of data sources, multitude of data modalities (e.g., structured, keyword, geospatial search), and availability of computation services (e.g., machine learning and graph analytics algorithms). Although SPARQL queries provide a convenient way of expressing data requests over RDF knowledge graphs, the level of support for hybrid information needs is limited: existing query engines usually focus on retrieving RDF data and only support a set of hard-coded built-in services. In this paper we describe representative use cases of metaphacts in the cultural heritage and pharmacy domains and the hybrid information needs arising in them. To address these needs, we present Ephedra: a SPARQL federation engine aimed at processing hybrid queries. Ephedra provides a flexible declarative mechanism for including hybrid services into a SPARQL federation and implements a number of static and runtime query optimization techniques for improving the hybrid SPARQL queries performance. We validate Ephedra in the use case scenarios and discuss practical implications of hybrid query processing.
Companion of the The Web Conference 2018 on The Web Conference 2018 - WWW '18, 2018
Vector embedding models have recently become popular for encoding both structured and unstructure... more Vector embedding models have recently become popular for encoding both structured and unstructured data. In the context of knowledge graphs such models often serve as additional evidence supporting various tasks related to the knowledge base population: e.g., information extraction or link prediction to expand the original dataset. However, the embedding models themselves are often not used directly alongside structured data: they merely serve as additional evidence for structured knowledge extraction. In the metaphactory knowledge graph management platform, we use federated hybrid SPARQL queries for combining explicit information stated in the graph, implicit information from the associated embedding models, and information extracted using vector embeddings in a transparent way for the end user. In this paper we show how we integrated RDF data with vector space models to construct an augmented knowledge graph to be used in customer applications.
The alignment of terminologies can be considered as a kind of “translation” between two or more t... more The alignment of terminologies can be considered as a kind of “translation” between two or more terminologies that aims to enhance the communication among people coming from different domains or expertise. In this paper we introduce the Visual Terminology Alignment tool (VisTA) that enables the exact alignment for RDF/SKOS-like terminologies, suitable for integrating knowledge bases, rather than information retrieval systems. The tool provides a simple and friendly web-based user interface for the alignment between two terminologies, while it visualizes the terminology hierarchies, enables the interactive alignment process, and presents the alignment result. The latter is a native RDF/SKOS graph that interconnects the two terminology graphs, supporting interoperability and extending the search capabilities over the integrated semantic graph, using the broader and exact match properties.
Voice-enabled user interfaces have become a popular means of interaction with various kinds of ap... more Voice-enabled user interfaces have become a popular means of interaction with various kinds of applications and services. In addition to more traditional interaction paradigms such as keyword search, voice interaction can be a convenient means of communication for many groups of users. Amazon Alexa has become a valuable tool for building custom voice-enabled applications. In this demo paper we describe how we use Amazon Alexa technologies to build a Semantic Web applications able to answer factual questions using the Wikidata knowledge graph. We describe how the Amazon Alexa voice interface allows the user to communicate with the metaphactory knowledge graph management platform and a reusable procedure for producing the Alexa application configuration from semantic data in an automated way.
The idea of code quality assessment is well known for a long time; class connectivity metrics wer... more The idea of code quality assessment is well known for a long time; class connectivity metrics were proposed by community several years ago and have not become generally applicable practice in industrial programming. The objective of the study, part of which we present in this paper, is to critically analyze the metrics available for today: Are they completely unusable, or considering their specifics can be useful helpers for software specialists. Specifically, we try to answer the questions: Are there any connection between design patterns and cohesion metrics, and how these patterns affect metrics if they do.
Knowledge graph management use cases often require addressing hybrid information needs that invol... more Knowledge graph management use cases often require addressing hybrid information needs that involve a multitude of data sources, a multitude of data modalities (e.g., structured, keyword, geospatial search), and availability of computation services (e.g., machine learning and graph analytics algorithms). Although SPARQL queries provide a convenient way of expressing data requests over RDF knowledge graphs, the level of support for hybrid information needs is limited: existing query engines usually focus on retrieving RDF data and only support a set of hard-coded built-in services accessible via SPARQL 1.1 queries. To deal with this problem, we present Ephedra: a SPARQL federation engine aimed at processing hybrid queries, which provides a flexible declarative mechanism for including hybrid services into a SPARQL federation.
Abstract Class cohesion, understood as the degree of how tightly are bound or related its interna... more Abstract Class cohesion, understood as the degree of how tightly are bound or related its internal elements to one another, is often a critically important for quality assurance (QA) of object-oriented software. Typically, a low cohesive class contains disparate and/or isolated members; therefore, cohesion level is useful for detecting of poorly designed classes and ensuring faster and better system reconfiguration. There are over thirty different metrics to measure cohesion, based on class member analysis in terms of number and structure of attributes and methods. Utilizing class cohesion metrics can promote Java code static analysis quality, improve object-oriented programming practices, and suggest advanced and efficient ones. The jPeek tool with its library for inspecting objects in Java was developed by Huawei Technologies Co. Ltd. to achieve these goals [1]. The idea of code quality assessment is well known for a long time; class connectivity metrics were proposed by community several years ago and have not become generally applicable practice in industrial programming. The main goal of this study is to make a methodology for using cohesion metrics to analyze code that allows users to estimate their projects in the most appropriate way. During the study, each of the metrics was studied in detail, the influence of programming patterns on the result of the metrics was evaluated, and as a result a methodology for using the metrics to obtain the most reliable estimate was formulated.
The continuous ground-based measurements of greenhouse gases carried out in Siberia in the past t... more The continuous ground-based measurements of greenhouse gases carried out in Siberia in the past two decades allowed the long-term trends, as well as the diurnal and seasonal cycles of CO 2
First results on the constitution of the ternary systems Li-Sn-C and Li-Sn-Si are presented. Extr... more First results on the constitution of the ternary systems Li-Sn-C and Li-Sn-Si are presented. Extrapolation calculations from the binary boundary systems allow identifying three alloys with key compositions that yield substantial information about the ternary phase diagrams. These alloys were characterized after long-term annealing using X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The XRD and DSC measurements suggest the formation of a solid solution of the isostructural phases Li 5 Sn 2 and Li 7 Si 3 instead of predicted three phase equilibrium in the Li-Sn-Si system. Ternary phases are not observed.
Some published experimental results on the thermodynamic data of pure solid CaO and MgO significa... more Some published experimental results on the thermodynamic data of pure solid CaO and MgO significantly contradict the widely used data in review books or tables, such as JANAF data. We scrutinized all the original experimental data forming the basis in review books and tables in order to establish a more realistic uncertainty range. The two Gibbs energy functions of CaO and MgO are combined with those of all other relevant phases to develop a thermodynamic database for the Mg–Ca–O system. The first systematic study of the calculated Mg–Ca–O phase diagram is presented. This phase diagram is validated by recently obtained dedicated experimental data using in-situ synchrotron radiation diffraction to study phase formation and reactions during melting and solidification of Mg and Mg–Ca alloys with CaO-additions below 1050 K. Intricacies in the solidification path of Mg-rich ternary alloys are revealed by the present thermodynamic calculations. Mg-rich alloys are categorized in four group...
ABSTRACT Thermodynamic descriptions are developed for the ternary Mg-Ce-Sn and the quaternary Mg-... more ABSTRACT Thermodynamic descriptions are developed for the ternary Mg-Ce-Sn and the quaternary Mg-Ca-Ce-Sn systems by combining the Calphad method with experimental investigations on selected key samples. Ten ternary and six quaternary alloy samples were prepared from the elements in sealed Ta-capsules and studied by differential thermal, microstructural and x-ray diffraction analyses. These data were used together with the scarce literature data to develop and/or validate the thermodynamic descriptions and the calculated phase diagrams in the Mg-rich regions. Phase formation and microstructure development is also compared with solidification simulations under equilibrium and Scheil conditions. The ternary MgSnCe compound is found to be extremely stable. In the quaternary Mg-Ca-Ce-Sn system it exhibits very large solid solubility of Ca and exists as a single solid phase up to the known intermetallic solution phase range MgSnCa-Ca2Sn, all exhibiting the same crystal structure. These features result in significant complexity of phase equilibria in quaternary Mg-rich alloys.
This report describes a 2nd place solution of the detection challenge which is held within CVPR 2... more This report describes a 2nd place solution of the detection challenge which is held within CVPR 2020 Retail-Vision workshop. Instead of going further considering previous results this work mainly aims to verify previously observed takeaways by re-experimenting. The reliability and reproducibility of the results are reached by incorporating a popular object detection toolbox-MMDetection. In this report, I firstly represent the results received for Faster-RCNN and RetinaNet models, which were taken for comparison in the original work. Then I describe the experiment results with more advanced models. The final section reviews two simple tricks for Faster-RCNN model that were used for my final submission: changing default anchor scale parameter and train-time image tiling. The source code is available at https://github.com/tyomj/product_detection.
<p>A more accurate characterization of the sources and sinks of methane (CH... more <p>A more accurate characterization of the sources and sinks of methane (CH<sub>4</sub>) and carbon dioxide (CO<sub>2</sub>) in the vulnerable Arctic environment is required to better predict climate change. A large-scale aircraft campaign took place in September 2020 focusing on Siberian coast. CH<sub>4</sub> and CO<sub>2</sub> were measured in situ during the campaign and form the core of the study. Measured ozone (O<sub>3</sub>) and carbon monoxide (CO) are used here as tracers. Compared to the reference (i.e., the seasonal value at Mauna Loa, Hawaii, US), median CH<sub>4</sub> mixing ratios are fairly higher (1890-1969 ppb vs 1887 ppb) while CO<sub>2</sub> mixing ratios from all flights are lower (408.09-411.50 ppm vs 411.52 ppm). We also report on 3 case studies. Our analysis suggests that during the campaign the European part of Russia’s Arctic and Western Siberia were subject to long-range transport of polluted air masses, while the East mainly was under the influence of local emission of greenhouse gases. The relative contributions of anthropogenic and natural sources of CH<sub>4</sub> in Siberia are simulated using the Lagrangian model FLEXPART in order to identify dominant sources in the boundary layer and in the free troposphere. In western terrestrial flights, air masses composition is influenced by from wetlands and anthropogenic activities (waste management, the fossil fuel industry and to a lesser extent the agricultural sector), while in the East, emissions are dominated by freshwaters, wetlands, and the oceans, with an ambiguous contribution from likely anthropogenic sources related to fossil fuels. Our results generally highlight the importance of the contribution form freshwater and oceans emissions and, combined with the large uncertainties associated with them, suggest that the emission from these aquatic sources should receive more attention in Siberia.</p>
<p>Aerosols play an important role in radiation processes in the atmosphere... more <p>Aerosols play an important role in radiation processes in the atmosphere, as well as they have a significant impact on global and regional air quality. The process of the atmospheric nanoparticle formation starts from in situ conversion of condensable vapors. Then, the freshly formed nanometer-size clusters begin to grow due to the condensation of nucleating vapours on them and a self-coagulation as well, thus reaching the optically active size ranges. The relative contribution of the above mechanisms can be estimated by the chemical composition of size-segregated particles. Here, we present preliminary results of the analysis of aerosol samples characterizing the inorganic chemical composition of particles ranging from a few nm to 10 mm. The sampling was performed at Fonovaya Observatory (West Siberia) in October 2021 by means of the Model 125R Nano-MOUDI Impactor.</p><p>The analysis showed that in the lowest size range (<10 nm), only five ions were detected: SO<sub>4</sub><sup>2-</sup>, Cl<sup>-</sup>, K<sup>+</sup>, Na<sup>+</sup>, H<sup>+</sup>. The growth of the nucleation mode particles to the size range of 60-100 nm was accompanied by increasing content of SO<sub>4</sub><sup>2-</sup>, Na<sup>+</sup>, H<sup>+</sup> ions to 50, 37 and 13%, respectively, suggesting the condensation of H<sub>2</sub>SO<sub>4</sub> vapours or the coagulation of particles contained mainly Na<sub>2</sub>SO<sub>4</sub>. A content of ammonium ions (NH<sub>4</sub><sup>+</sup>) appeared to be significant only in the accumulation mode size range (0.1-1.0 mm). Nitrates (NO<sub>3</sub><sup>-</sup>) were detected mainly in the Aitken mode particles and then their contribution increases in accumulation and coarse mode ranges.</p><p>This work was supported by the RFBR grant No. 19-05-50024 (Microparticles in the atmosphere: formation and transformation in the atmospheric surface layer and in the free troposphere, radiation effects and impact on public health).</p>
Lobachevsky University Electrocardiography Database (LUDB) is an ECG signal database with marked ... more Lobachevsky University Electrocardiography Database (LUDB) is an ECG signal database with marked boundaries and peaks of P, T waves and QRS complexes. The database consists of 200 10-second 12-lead ECG signal records representing different morphologies of the ECG signal. The ECGs were collected from healthy volunteers and patients of the Nizhny Novgorod City Hospital No 5 in 2017-2018\. The patients had various cardiovascular diseases while some of them had pacemakers. The boundaries of P, T waves and QRS complexes were manually annotated by cardiologists for all 200 records. Also, each record is annotated with the corresponding diagnosis. The database can be used for educational purposes as well as for training and testing algorithms for ECG delineation, i.e. for automatic detection of boundaries and peaks of P, T waves and QRS complexes.
Communications in Computer and Information Science, 2017
Knowledge graph management use cases often require addressing hybrid information needs that invol... more Knowledge graph management use cases often require addressing hybrid information needs that involve multitude of data sources, multitude of data modalities (e.g., structured, keyword, geospatial search), and availability of computation services (e.g., machine learning and graph analytics algorithms). Although SPARQL queries provide a convenient way of expressing data requests over RDF knowledge graphs, the level of support for hybrid information needs is limited: existing query engines usually focus on retrieving RDF data and only support a set of hard-coded built-in services. In this paper we describe representative use cases of metaphacts in the cultural heritage and pharmacy domains and the hybrid information needs arising in them. To address these needs, we present Ephedra: a SPARQL federation engine aimed at processing hybrid queries. Ephedra provides a flexible declarative mechanism for including hybrid services into a SPARQL federation and implements a number of static and runtime query optimization techniques for improving the hybrid SPARQL queries performance. We validate Ephedra in the use case scenarios and discuss practical implications of hybrid query processing.
Companion of the The Web Conference 2018 on The Web Conference 2018 - WWW '18, 2018
Vector embedding models have recently become popular for encoding both structured and unstructure... more Vector embedding models have recently become popular for encoding both structured and unstructured data. In the context of knowledge graphs such models often serve as additional evidence supporting various tasks related to the knowledge base population: e.g., information extraction or link prediction to expand the original dataset. However, the embedding models themselves are often not used directly alongside structured data: they merely serve as additional evidence for structured knowledge extraction. In the metaphactory knowledge graph management platform, we use federated hybrid SPARQL queries for combining explicit information stated in the graph, implicit information from the associated embedding models, and information extracted using vector embeddings in a transparent way for the end user. In this paper we show how we integrated RDF data with vector space models to construct an augmented knowledge graph to be used in customer applications.
The alignment of terminologies can be considered as a kind of “translation” between two or more t... more The alignment of terminologies can be considered as a kind of “translation” between two or more terminologies that aims to enhance the communication among people coming from different domains or expertise. In this paper we introduce the Visual Terminology Alignment tool (VisTA) that enables the exact alignment for RDF/SKOS-like terminologies, suitable for integrating knowledge bases, rather than information retrieval systems. The tool provides a simple and friendly web-based user interface for the alignment between two terminologies, while it visualizes the terminology hierarchies, enables the interactive alignment process, and presents the alignment result. The latter is a native RDF/SKOS graph that interconnects the two terminology graphs, supporting interoperability and extending the search capabilities over the integrated semantic graph, using the broader and exact match properties.
Voice-enabled user interfaces have become a popular means of interaction with various kinds of ap... more Voice-enabled user interfaces have become a popular means of interaction with various kinds of applications and services. In addition to more traditional interaction paradigms such as keyword search, voice interaction can be a convenient means of communication for many groups of users. Amazon Alexa has become a valuable tool for building custom voice-enabled applications. In this demo paper we describe how we use Amazon Alexa technologies to build a Semantic Web applications able to answer factual questions using the Wikidata knowledge graph. We describe how the Amazon Alexa voice interface allows the user to communicate with the metaphactory knowledge graph management platform and a reusable procedure for producing the Alexa application configuration from semantic data in an automated way.
The idea of code quality assessment is well known for a long time; class connectivity metrics wer... more The idea of code quality assessment is well known for a long time; class connectivity metrics were proposed by community several years ago and have not become generally applicable practice in industrial programming. The objective of the study, part of which we present in this paper, is to critically analyze the metrics available for today: Are they completely unusable, or considering their specifics can be useful helpers for software specialists. Specifically, we try to answer the questions: Are there any connection between design patterns and cohesion metrics, and how these patterns affect metrics if they do.
Knowledge graph management use cases often require addressing hybrid information needs that invol... more Knowledge graph management use cases often require addressing hybrid information needs that involve a multitude of data sources, a multitude of data modalities (e.g., structured, keyword, geospatial search), and availability of computation services (e.g., machine learning and graph analytics algorithms). Although SPARQL queries provide a convenient way of expressing data requests over RDF knowledge graphs, the level of support for hybrid information needs is limited: existing query engines usually focus on retrieving RDF data and only support a set of hard-coded built-in services accessible via SPARQL 1.1 queries. To deal with this problem, we present Ephedra: a SPARQL federation engine aimed at processing hybrid queries, which provides a flexible declarative mechanism for including hybrid services into a SPARQL federation.
Abstract Class cohesion, understood as the degree of how tightly are bound or related its interna... more Abstract Class cohesion, understood as the degree of how tightly are bound or related its internal elements to one another, is often a critically important for quality assurance (QA) of object-oriented software. Typically, a low cohesive class contains disparate and/or isolated members; therefore, cohesion level is useful for detecting of poorly designed classes and ensuring faster and better system reconfiguration. There are over thirty different metrics to measure cohesion, based on class member analysis in terms of number and structure of attributes and methods. Utilizing class cohesion metrics can promote Java code static analysis quality, improve object-oriented programming practices, and suggest advanced and efficient ones. The jPeek tool with its library for inspecting objects in Java was developed by Huawei Technologies Co. Ltd. to achieve these goals [1]. The idea of code quality assessment is well known for a long time; class connectivity metrics were proposed by community several years ago and have not become generally applicable practice in industrial programming. The main goal of this study is to make a methodology for using cohesion metrics to analyze code that allows users to estimate their projects in the most appropriate way. During the study, each of the metrics was studied in detail, the influence of programming patterns on the result of the metrics was evaluated, and as a result a methodology for using the metrics to obtain the most reliable estimate was formulated.
The continuous ground-based measurements of greenhouse gases carried out in Siberia in the past t... more The continuous ground-based measurements of greenhouse gases carried out in Siberia in the past two decades allowed the long-term trends, as well as the diurnal and seasonal cycles of CO 2
First results on the constitution of the ternary systems Li-Sn-C and Li-Sn-Si are presented. Extr... more First results on the constitution of the ternary systems Li-Sn-C and Li-Sn-Si are presented. Extrapolation calculations from the binary boundary systems allow identifying three alloys with key compositions that yield substantial information about the ternary phase diagrams. These alloys were characterized after long-term annealing using X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The XRD and DSC measurements suggest the formation of a solid solution of the isostructural phases Li 5 Sn 2 and Li 7 Si 3 instead of predicted three phase equilibrium in the Li-Sn-Si system. Ternary phases are not observed.
Some published experimental results on the thermodynamic data of pure solid CaO and MgO significa... more Some published experimental results on the thermodynamic data of pure solid CaO and MgO significantly contradict the widely used data in review books or tables, such as JANAF data. We scrutinized all the original experimental data forming the basis in review books and tables in order to establish a more realistic uncertainty range. The two Gibbs energy functions of CaO and MgO are combined with those of all other relevant phases to develop a thermodynamic database for the Mg–Ca–O system. The first systematic study of the calculated Mg–Ca–O phase diagram is presented. This phase diagram is validated by recently obtained dedicated experimental data using in-situ synchrotron radiation diffraction to study phase formation and reactions during melting and solidification of Mg and Mg–Ca alloys with CaO-additions below 1050 K. Intricacies in the solidification path of Mg-rich ternary alloys are revealed by the present thermodynamic calculations. Mg-rich alloys are categorized in four group...
ABSTRACT Thermodynamic descriptions are developed for the ternary Mg-Ce-Sn and the quaternary Mg-... more ABSTRACT Thermodynamic descriptions are developed for the ternary Mg-Ce-Sn and the quaternary Mg-Ca-Ce-Sn systems by combining the Calphad method with experimental investigations on selected key samples. Ten ternary and six quaternary alloy samples were prepared from the elements in sealed Ta-capsules and studied by differential thermal, microstructural and x-ray diffraction analyses. These data were used together with the scarce literature data to develop and/or validate the thermodynamic descriptions and the calculated phase diagrams in the Mg-rich regions. Phase formation and microstructure development is also compared with solidification simulations under equilibrium and Scheil conditions. The ternary MgSnCe compound is found to be extremely stable. In the quaternary Mg-Ca-Ce-Sn system it exhibits very large solid solubility of Ca and exists as a single solid phase up to the known intermetallic solution phase range MgSnCa-Ca2Sn, all exhibiting the same crystal structure. These features result in significant complexity of phase equilibria in quaternary Mg-rich alloys.
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Papers by Artem Kozlov