Theory Study Research Articles

Pavlo Movchan as an art researcher: word, image, sign

The subject of the research in the article is the peculiarities of theoretical-literary and art-scientific publications of the outstanding Ukrainian poet Pavlo Movchan, as well as his historical-literary and historical-artistic works. The main problem of the article was the need to reduce these features into a single concept, to determine the scientific basis of this concept. To do this, a large array of (more than fifty) articles, reviews, and essays of the research poet for the period from the mid-1970s to the second decade of the XXI century was collected from various sources and processed. The poet’s work has not been properly studied by scholars, and his theoretical-literary and historical-literary works have gone out of their attention if we do not take into account the cursory observations of O. Khomenko in one of the studies of poetry by P. Movchan. The aim of the article is to highlight the systemic nature of Pavlo Movchan’s literary views and apply them to the analysis of the works of classics and contemporary Ukrainian and foreign artists. To do this, we used the psychological method in determining the verbal and figurative essence of Movchan’s theoretical concept, historical and literary — in the analysis of his reviews and “portrait” publications, mythopoetic — in conceptualizing the oral and written word, the artistic word as a link between generations, author and recipients. The results of the research are 1. Conditionally literary and literary-critical research of Pavlo Movchan can be divided into several blocks: the theory of words, images, art; specifics of lyrics, literary translation; development of Ukrainian poetry in the second half of the XX–XXI centuries; analysis of works of Ukrainian classics (“A Word about Igor’s Regiment”, works by T. Shevchenko, M. Gogol, romantic poets, etc.), contemporary poets; evaluation of the works of foreign writers of the West and the East; reception of paintings and cinematographic works of Ukrainian contemporary artists. 2. The basis of the theoretical and literary concept of P. Movchan was the theory of O. Potebnja about the external and internal form of the word and its content, the constant need to restore or create specific sensory meaning of the word-image in art. The wide range of meanings of the word, accumulated over the centuries, is the basis of dialogue between the author and the recipients, the link between them. The artist’s skill level is interrelated with the ability to find and revive this wide range of meaning. 3. Pavlo Movchan considers the main task of literary translation to not just be an adequate mechanical transmission of words, but a reproduction of the spirit of words, works, and uniqueness of idiosyncrasies related to the creative intentions of authors, for which the translator must thoroughly study the biography and works of the original, literary and social context, the history of writing the work, the meaning and nuances of each word, excellent command of the native language and the specifics of the original language, the mentality of the people to which the author belongs and much more, up to flora and fauna, their symbols and more. 4. Pavlo Movchan sets the same principles and requirements as a literary critic in the study of specific works or works of certain authors. This gives him the opportunity not only to comprehensively and deeply characterize the creative work of various authors but also to dominant features, to make their own original and reasoned discoveries. 5. Pavlo Movchan’s art views in the field of visual arts are organically correlated with his literary concept, testify to a deep knowledge of this field and a subtle aesthetic sense in the evaluation of works of painting and cinema. The practical significance of the article lies in the possibility of its application in the study and teaching of literary theory and art theory, the basics of Potebnja theory, history of classical and modern Ukrainian and foreign literature, history of Ukrainian painting, and cinema of XX–XXI centuries, the uniqueness of Pavlo Movchan.

The Neutrosophic Treatment for Multiple Storage Problem of Finite Materials and Volumes

In this paper, we present a multi-inventory with limited size model to clarify the basic idea of ​​multi-inventory systems in order to understand the relationships between the main variables, and examine the inventory’s behaviour in a very broad range. In addition to the obvious applications in physical warehouses (such as electrical equipment, supplies, raw materials used in manufacturing, etc.), there are less predictable cases in which the multi-inventory model can be used. Such a model can be applied on the number of engineers and employees in a company, also on the number of students and professors in a university, as they constitute the processes of demand, hiring, and laying off which are types of compensation. Moreover, it may be useful at times not to look at physical goods as inventory as the prior examples are both types of inventory based on the space occupied as the available space can accommodate stored materials and is considered an inventory that must be compensated when depleted. The previous examples, in addition to many others, can be classified as inventory problems indicating the abundance of inventory models application, and the possibility of benefiting from the study of inventory theory in terms of clarifying the internal structure of the systems. In this study, we used the Neutrosophic logic to solve the problem of multi-inventory and limited size, depending on the fact that the optimal volume of materials to be stored is affected by the rate of demand for inventory. Moreover, this study is considered an expansion of one of the known classical inventory models that depend on finite data and that is done by assigning a constant value to the inventory demand rate over the storage cycle time period, which does not correspond with the realistic application. The limited application of classical inventory models was the motivating factor for this study as it deals with all data, whether specified or not in the inventory management process. Moreover, it takes into account all cases that the demand for inventory can go through, ranging from the cessation of demand for some stored materials to demand that exceeds the values ​​provided by the real study. Through this study, we developed mathematical relationships that we used to determine the necessary quantities of each of the materials to be stored based on the rate of demand and provide us with results that are more accurate. These results that can be utilized to store many materials in appropriate quantities and available volume, ensure that there is no shortage during the storage cycle period, and enables us to calculate all the necessary costs, which will achieve great profits.

A Study of Joshua Reynolds' Theory of Imitation—Focusing on Fifteen Discourses Delivered in the Royal Academy

<p>雷諾茲（Joshua Reynolds）是英國皇家美術學院的創始人及第一任院長，也是英國新古典主義繪畫的代表人物。他的《皇家美術學院十五講》是重要的理論著作。雷諾茲在演講中提出藝術創作的相關理論與指導原則。雷諾茲希望透過他的演講，與學生分享經驗，指引他們方向並縮短摸索的過程。他在演講中提倡一種知性的、普遍的理想美，這種美可以提升藝術家的品味與作品的質量，也可以使藝術家改善社會地位，將繪畫提升到自由藝術的層級，與工匠劃清界線。他的演講不僅反映了他的藝術觀點，也體現了英國十八世紀藝文界的思潮和歐陸數百年的藝術理論。模仿論是雷諾茲理論的核心內容，因此本文欲透過雷諾茲《皇家美術學院十五講》，找出雷諾茲的模仿理論及其思想的來源。</p> <p> </p><p>Sir Joshua Reynolds was an iconic British neoclassical painter, known as the founder and first dean of the Royal Academy of Arts. His book Fifteen Discourses Delivered in the Royal Academy is an important theoretical work. In it, Reynolds pro-posed a theory/ theories and guiding principles of artistic creation. In his speeches lectures, he advocated an intellectual, universal, and ideal version? vision? conceptu-alization? of beauty to that would? enhance artists’ taste and the quality of their work. Moreover, this beauty enabled artists to improve their social status, enhanced the standing of painting by making it into a liberal art, and definitively severed ties be-tween artists and artisans. Reynolds hoped to use his speeches lectures to share his ex-perience with his students, guide them in their artistic direction development and simplified simplify their process journey of discovery. His speeches lectures not only reflected his artistic viewpoints, but also embodied represented? British art and litera-ture during the eighteenth century, as well as the art theories of art developed in Brit-ain and the European continent over hundreds of years. His theoretical focus is based on the idea of idealized imitation. Therefore, this article intends to uses Reynolds’s Fifteen Discourses Delivered in the Royal Academy to explore his theory of imitation and analyze the sources of his thoughts and views.</p> <p> </p>

Hopefully, Augustine

When Augustine wrote about having discovered a hope (diuersa spes) different from the political ambitions that drew him to Rome then Milan (spes saeculi), he referred to Christians’ hopes for celestial reward. But several colleagues suggest that he also harbored hopes for a kinder political culture. Discussions of Augustine’s hopes have enlivened the study of political theory and political theology for several generations. During the twenty-first century two influential volumes took him as their inspiration for “hopeful citizenship” and “democratic citizenship.” Recently, two perceptive studies propose variations on the themes introduced there. What follows deploys several of Hannah Arendt’s observations about Augustine to suggest that his political hopes were somewhat more restricted but more radical than the latest contributions to his political theology suggest.

“Nobody told me”: Chicana Women’s Madness and Mourning in Sandra Cisneros’s Have You Seen Marie?

“‘Nobody told me’: Chicana Women’s Madness and Mourning in Sandra Cisneros’s Have You Seen Marie?” employs interdisciplinary research to understand Sandra Cisneros’ tale of women’s mental illness in Have You Seen Marie?. Building on Marta Caminero-Santangelo’s critique of the inequitable treatment of mental illness in literary criticism of women’s writing, I argue that Cisneros draws awareness to the distinct challenges that Chicanas face while struggling with mental illness. Contextualizing Cisneros’ representation of the grief a Catholic Chicana woman experiences after losing her mother, I draw on the work of scholars from theology, psychology, sociology, critical race theory, postcolonial theory, and disability studies to further understand the impact of colonization on familial gender roles, the importance of la Virgen de Guadalupe, and representations of mental illness.

DFT Calculations of 2,5-Diphenyl Furan against SARS-CoV-2 Mpro based on Molecular Docking Approach

FTIR, FT-Raman and density functional theory (DFT) studies of 2,5-diphenyl furan (DPF) has been carried out to interpret the molecular structure, vibrational frequencies and its intensities. From the estimation, we obtained the HOMO-LUMO energy gap as 2.7113 eV, which is clearly significant the charge transfer occurs within the molecule. The intramolecular interaction and delocalization of the charges has been studied using NBO analysis. In addition, molecular electrostatic potential (MEP) calculations were also performed. The hydrogen bond interactions and binding energy of 2,5-diphenyl furan were estimated using molecular docking studies. The docking investigation was carried out to confirm the repressive nature of title molecule against SARS-CoV-2 main protease (Mpro) proteins.

CORPORATE GOVERNANCE THEORY AND MODEL : A CONCEPTUAL OBSERVATION

This paper outlines the conceptual, contextual and disciplinary scope of the rapidly evolving topic of corporate governance. The aim of this paper is to make a study of different theories and models of corporate governance that have been used globally by analysing strengths and weaknesses for each one. This is to determine which one is the best theory and model and if it can be adopted to different economic systems. Corporate governance theory has tended to look to this theory to guide the decisions of the board of directors in curbing excessive executive power in the hands of management. While useful for this purpose, the Agency Theory provides limited guidance on corporate governance in real life situations which are far more complex. With the blurring of the roles of the principal and the agent, the currently prevalent governance framework, based on the Agency Theory has become self limiting and ineffective. Efforts to supplement the Agency Theory with alternative theoretical frameworks such as the Stakeholder Theory and the Stewardship Theory have, at times, tended to place the board of directors in conflict with their legal obligations to work in the interests of the shareholders. A governance model based on the concept of Trusteeship, while providing fresh insights, suffers from problems in implementation and remains a goal . These alternative frameworks have, therefore, not been of much practical use to the board members in helping them to decide what constitutes the “right” decision. We need new theoretical insights that will take us towards a comprehensive theory of governance. This paper seeks to highlight the various theoretical frameworks for corporate governance.

THEORETICAL ANALYSIS OF THE EVOLUTION OF MONETARY SYSTEMS OF RUSSIA IN EXTREME MILITARY-POLITICAL CIRCUMSTANCES OF THE FIRST HALF OF THE TWENTIETH CENTURY (IN CONNECTION WITH THE 80TH ANNIVERSARY OF THE BEGINNING OF THE GREAT PATRIOTIC WAR)

The author of the article, addressed to those who teach and study in higher education economic theory, the history of economic thought and the socio-economic history of Russia, proceeds from the premise that changes in the socio-economic system of the country during the period of change in the dominant technological order actualize the development of the theory of money and the study of various stages of historical evolution of the domestic monetary economy (Russian monetary systems). In this context, an analysis of those periods of this evolution in the first half of the twentieth century, when the credit ruble becomes an extraordinary resource of the «war economy», unfolds. The article also examines the peculiarities of monetary circulation during the operation of the gold standard system and during the period of gold «leaving» to the state reserve fund. The author puts forward a hypothesis according to which the changes taking place in the monetary system in connection with the demonetization of gold are the accumulation of prerequisites for the transition to a post-industrial economic system.
 
 Inclusion in the analysis of the events of the global military-political history of 1914–1917 and 1941–1945, i.e. events of the First and Second World Wars, helps to reveal the real basis on which a special type of economic relations was formed — the phenomenon of «war economy». The article identifies the key factors of instability in the twentieth century — industrial, monetary and world crises. The study of the peculiarities of the development of the crisis in peacetime and in the conditions of a «military-inflationary economy» in the works of prominent Russian economists deepens the understanding of the structural deformation of the national economy.
 
 It is shown that the «price revolution», which characterizes the explosive growth of inflation, has become a vivid manifestation of the world economic instability during the development of extreme military-political events in Russia and in the countries of Western Europe. Attention is drawn to the fact that the «price revolution» in the conjuncture theory of M.I. Tugan-Baranovsky and the works of Z.S. Katsenelenbaum was considered as a function of qualitative changes that took place in the economic system as a result of the expansion of the sphere of money circulation during the transition from natural production to industrial production. The «price revolution» manifested itself with the greatest force in the conditions of the «war economy». The destruction of the national economy was accompanied by the development of «golden» inflation, indicating a chronic commodity deficit.
 
 The author argues that the size of the accumulation of gold in 1920–1945, the emergence of large banks — custodians of the gold and foreign exchange reserves of the countries — members of the monetary unions — largely influenced the results of the competition between the three leading currencies (franc, pound and dollar), claiming to be the world leader. The conclusion is argued that the accumulation of gold and foreign exchange reserves in the conditions of the «war economy» accelerated the formation of a new monetary and financial «map» of the world in the second half of the twentieth century.

Nonencounters ‘in the wake’: re-inscribing a Black Transpacific in Tanin no kao and La Muerte de Artemio Cruz

This article draws from Black critical theory and critical race studies to explore how the relationship between the wound, the body, and the role of trauma in literary text can be reposed as a relationship to racial inscription in two novels, Abe Kōbō’s Tanin no kao (The face of Another, 1964) and Carlos Fuentes’s La Muerte de Artemio Cruz (The Death of Artemio Cruz, 1962). In these terms, the article explores the function of injury in these literary texts as it relates to their representations, or fictionalizations, of Blackness. The article deploys a critical approach to transpacific literary comparison that does not draw from naturalized connections – termed a framework of ‘nonencounter’ – to discuss how the questions of race and Blackness in both novels re-inscribes the particular histories of colonialism and the transpacific entanglements of antiblackness that shaped dominant discourses on the national subject and cultural identity in Mexico and Japan. 1

Crossing Borders in Film Theory and Adaptation Studies

The history of film theory is full of what we might call migrating concepts. From the Russian Formalists which, in their Poetica Kino (Poetics of cinema) adapt concepts initially created as part of literary theory (fabula vs. syuzhet, film as language, cine-stylistics) to David Bordwell and Kristin Thompson and their formalist inspired approach to film studies, from André Bazin and his theory of realism, inspired by phenomenological concepts, the history of film theory can be thought of as a genealogy of crossing borders. The circulation of concepts from literary theory to film theory is also quite astonishing in the theory of adaptation. In the study of the adaptation of literary works for cinema, the travel of concepts (the crossing of borders) can be observed and analysed especially in narrative theory and adaption theory.

Efficiency Driven Effect of Education in China: The Perspective of Global Competitiveness and Graduate Education

Capital, natural resources, technology and education are often considered to be the most important factors in improving the level of economic development. China is in the "efficiency-driven" stage of economic development. There are objective laws in the development of education level and economic growth, but they interact with each other. Economic growth provides the foundation and necessary conditions for the development of education. At the same time, the role of education in promoting economic growth is also very obvious. Based on the perspective of postgraduate training, this paper studies the role of education in economic efficiency-driven, through the study of theory, data collection and empirical analysis, combined with the development characteristics of China's higher education, and compares China's and US higher education policies to guide China's higher education. The development of education, and then promote the transformation of China into the "innovation-driven" stage, has certain theoretical and practical significance.

A Brazilian Perspective on Audiobooks

Abstract This paper presents a Brazilian perspective on audiobooks. It contextualizes the past and current realities of the format in the country, on the basis of surveys coordinated by national associations connected to the book market and of archival research we have undertaken, and shows some examples of recorded literary works and recent initiatives in audiobook production. The ‘acoustic-editorial project’ idea is proposed as a way to highlight and deepen the materiality and production process of audiobooks, and to understand the editorial elements through which the listening experience is created. Authors from book history, bibliography, communication theory, and audiobook studies influenced this investigation and strengthened our construction of audiobooks as a research object.

Terrifying Allure: The Beauty of Harley Quinn in U.S. and Mexican Cosplay

Abstract Analyzing the evolution of DC Comics character Harley Quinn, this article addresses how fans approach Quinn’s appearance, identifying with and aspiring to be like the character. Focusing on the changes in Quinn’s costume and visual presentation, this article describes how cosplayers (practitioners of public costume play) link outer appearance to inner self and appropriate elements of Quinn’s costume for their own practice. Anchored in a humanities perspective that includes philosophy, beauty theory and fan studies, this article provides a close reading of the canonical figure’s visual representation and how that representation is used by cosplayers in the United States and Mexico to express fan identity.

The first two decades of Circular Economy in the 21st century: a bibliographic review

PurposeThe purpose of this paper is to analyze and map the main areas of the Circular Economy literature of the first two decades of 21st century, offering a broad vision about the growth of the theme during these years.Design/methodology/approachThe research was divided into two stages: the first was a systematic review of literature and the second consisted on generation and analysis of bibliographic maps.FindingsThe publication indicates the prominence of China and European Union countries in the production of articles about Circular Economy. Furthermore, the topic is restricted to academic area, and that research on Circular Economy is still very focused on theory studies, even with exponential growth in the number of published articles about the theme since 2015. Finally, it also provides a collection of information as the principal authors, the most cited publications, citations, co-citations and countries that have most published beyond which are the most discussed topics.Research limitations/implicationsA possible limitation of the research is that it was performed only in the Scopus database. It may be suggested as future searches that other databases are included as well, and another suggestion is to reduce the time period between research samples due to the exponential increase in the number of publications and topics discussed lately.Practical implicationsThe results of this paper can guide future researches about the development of Circular Economy during the next decades or years and serve as a facilitator for researchers and for managers that want to know more about the topic.Originality/valueA mapping of the principal players and main discussions about Circular Economy made in the first two decades of the 21st century and an analysis about the growth and changes about the theme.

Identifikasi Permasalahan Infrastruktur Drainase di Kampus Universitas Hasanuddin Tamalanrea, Kota Makassar

The Unhas Tamalanrea campus is an educational area which has an area of 220 hectares, one of the problems that exist when the intensity of rain is high enough in the area, namely the occurrence of inundation and flooding on several roads so it is necessary to find causes and solutions to these problems. The purpose of this study was to determine the problem of drainage infrastructure in the Unhas area. This research took place from November 2020 to April 2021. This research is located in the Hasanuddin University Area, Tamalanrea Campus, which is located in Tamalanrea District, Makassar City. Types of secondary data are the number of Unhas Tamalanrea campus communities, the volume of dirty water per person based on the number of communities in Unhas Tamalanrea and PERMEN PU RI No.12/PRT/M/2014 with data collection methods, namely literature, theory, and NSPK studies. The type of primary data is the existing condition of the drainage network at the Unhas Tamalanrea campus, with data collection methods namely surveys or field observations. The data analysis technique used is a comparative analysis, which is to compare the ideal or proper drainage infrastructure with the existing conditions of the research location. Based on the results of the study, there is a drainage infrastructure that is classified as a tertiary drainage channel and then leads to a secondary drainage channel on Polytechnic Street and empties into the Tallo River as a primary drainage channel that is well connected. The quality of the drainage infrastructure is not good, seen from the dimension of the drainage construction that is not wide enough and the drainage network where sedimentation occurs due to lack of maintenance.

A semiparametric Gumbel regression model for analyzing longitudinal data with non-normal tails.

Abnormal longitudinal values in biomarkers can be a sign of abnormal status or signal development of a disease. Identifying new biomarkers for early and efficient disease detection is crucial for disease prevention. Compared to the majority of the healthy general population, abnormal values are located within the tails of the biomarker distribution. Thus, parametric regression models that accommodate abnormal values in biomarkers can better detect the association between biomarkers and disease. In this article, we propose semiparametric Gumbel regression models for (1) longitudinal continuous biomarker outcomes, (2) flexibly modeling the time-effect on the outcome, and (3) accounting for the measurement error in biomarker measurements. We adopted the EM algorithm in combination with a two-dimensional grid search to estimate regression parameters and a function of time-effect. We proposed an efficient asymptotic variance estimator for regression parameter estimates. The proposed estimator is asymptotically unbiased in both theory and simulation studies. We applied the proposed model and two other models to investigate associations between fasting blood glucose biomarkers and potential risk factors from a diabetes ancillary study to the Atherosclerosis Risk in Communities (ARIC) study. The real data application was illustrated by fitting the proposed regression model and graphically evaluating the goodness-of-fit value.

A Graph Theory-Based Method for Dynamic Modeling and Parameter Identification of 6-DOF Industrial Robots

At present, the absolute positioning accuracy and control accuracy of industrial serial robots need to be improved to meet the accuracy requirements of precision manufacturing and precise control. An accurate dynamic model is an important theoretical basis for solving this problem, and precise dynamic parameters are the prerequisite for precise control. The research of dynamics and parameter identification can greatly promote the application of robots in the field of precision manufacturing and automation. In this paper, we study the dynamical modeling and dynamic parameter identification of an industrial robot system with six rotational DOF (6R robot system) and propose a new method for identifying dynamic parameters. Our aim is to provide an accurate mathematical description of the dynamics of the 6R robot and to accurately identify its dynamic parameters. First, we establish an unconstrained dynamic model for the 6R robot system and rewrite it to obtain the dynamic parameter identification model. Second, we establish the constraint equations of the 6R robot system. Finally, we establish the dynamic model of the constrained 6R robot system. Through the ADAMS simulation experiment, we verify the correctness and accuracy of the dynamic model. The experiments prove that the result of parameter identification has extremely high accuracy and the dynamic model can accurately describe the 6R robot system mathematically. The dynamic modeling method proposed in this paper can be used as the theoretical basis for the study of 6R robot system dynamics and the study of dynamics-based control theory.

Systematic kinetic study of magnesium production using magnesium oxide and carbonic materials at different temperatures

The main goal of this study was to determine the industrially best reductant for reduction of magnesium oxide to magnesium with wood charcoal and petroleum coke (petcoke) each in molar ratio 1:1 and 1:2 (oxidant:reductant) at high temperatures. In this study, a new and reliable combination of mathematical modeling and discrete numerical optimization theory by presenting 18 “mathematical filters” not relying only on statistical quantities of fitting (contrary to many similar researches) was introduced. The purpose of these filters was the determination of correct kinetic equation and therefore, the corresponding rate coefficient from among 18 equations most used at present in the challenging field of solid state chemical kinetics. With assistance of a new and fundamental mathematical function and the obtained values of rate coefficients, the function of rate coefficient in temperature was attained. The activation energy was then calculated as a function of temperature using the general definition of activation energy and the determined function for rate coefficient. The comparison between different reducing agents in the different conditions and with relevant previous study was accomplished to determine the best reducing agent from industry standpoint. Also, the areas under experimental data were calculated numerically and utilized for method validation and comparison. It turned out finally that relying only on fitting quantities in the solid state chemical kinetics can readily lead to wrong conclusions about the correct kinetic equation and about the most suitable reducing agent. It is obvious that the erroneous calculations and wrong decisions in the laboratory scale become significant and paramount in industry and this reveals the significance of rigorous mathematical analysis.Graphical abstract

Jihad as an Individual Duty (farḍ al-ʻayn) in the Ideology of Circassian Sultans (1382–1517)

This article is devoted to the study of the development of the theory and practice of jihad during the rule of the Circassian sultans in Egypt and Syria (1382–1517). The purpose of the study is to trace the development of key aspects of jihad, to identify features of its perception in the Mamluk state. An essential feature of the theory of jihad in the Mamluk period is the interpretation of jihad as farḍ al-ʿayn (the individual duty of every Muslim). While studying the theory of jihad, the authors rely on a holistic and balanced approach justified in the papers of M. Bonner and D. Cook and their interpretation of the concept of jihad, which has a centuries-old history of development and a sophisticated, multi-layered set of meanings. Another methodological basis of the present paper was the concept of minimalism and maximalism, developed by Yusef Waghid. The source base for the study of jihad theory is the works of Ibn al-Nahhas (d. 1411), a prominent philosopher of the Mamluk era. The interpretation of jihad as an individual duty of every Muslim, substantiated by Ibn al-Nahhas, was the foundation of the volunteer movement that developed in Egypt and Syria in the 15th century. The doctrine of jihad where the concepts of justice (al-‘adl) and truth (al-ḥaqq) play a key role, was used by the Mamluks and then by the Ottomans as a powerful ideological tool to manipulate the minds of Muslims. The relevance of the study is that the findings are not only true for the Middle Ages but are directly related to the present.

A density functional theory (DFT) study on reduced partition function ratios of oxygen species adsorbed on a Pt19 cluster and oxygen isotope effects

ABSTRACT A density functional theory (DFT) computation on oxygen species adsorbed on platinum (Pt) catalyst surfaces has been carried out to elucidate oxygen isotope fractionation observed at the cathode of a polymer electrolyte membrane fuel cell (PEMFC). The Pt(111) catalyst surface was modelled by a Pt19 cluster, and O, OH, OHH, OO, OOH, OHOH and HOHOH were assumed to be the oxygen species adsorbed on the Pt(111) surface. The oxygen isotope reduced partition function ratios (RPFRs) of the adsorbed species were calculated using the vibrational frequencies obtained by normal mode analyses performed on the optimized structures. Various oxygen isotope exchange equilibria among the adsorbed oxygen species and oxygen and water molecules in the gas phase were examined using their RPFRs. Experimental observation that the lighter 16O is enriched in water molecules exhausted from the cathode is explainable in a satisfactory manner by assuming oxygen isotope exchange equilibria of O2 molecule with O, OH, OO and OOH adsorbed on the Pt(111) surface that appear in the first half of the conversion reaction from O2 to H2O and those of H2O molecule with the adsorbed oxygen species, OHH, OHOH and HOHOH, formed in the latter half of the conversion reaction.