Machine-learning approach for discovery of conventional superconductors

First-principles computations are the driving force behind numerous discoveries of hydride-based superconductors, mostly at high pressures, during the last decade. Machine-learning (ML) approaches can further accelerate the future discoveries if their reliability can be improved. The main challenge of current ML approaches, typically aiming at predicting the critical temperature $T_{\rm c}$ of a solid from its chemical composition and target pressure, is that the correlations to be learned are deeply hidden, indirect, and uncertain. In this work, we showed that predicting superconductivity at any pressure from the atomic structure is sustainable and reliable. For a demonstration, we curated a diverse dataset of 584 atomic structures for which $\lambda$ and $\omega_{\log}$, two parameters of the electron-phonon interactions, were computed. We then trained some ML models to predict $\lambda$ and $\omega_{\log}$, from which $T_{\rm c}$ can be computed in a post-processing manner. The models were validated and used to identify two possible superconductors whose $T_{\rm c}\simeq 10-15$K and zero pressure. Going forward, this strategy will be improved to better contribute to the discoveries of new superconductors

Low-energy structures of zinc borohydride Zn(BH4_4)2_2

We present a systematic study of the low-energy structures of zinc borohydride, a crystalline material proposed for the hydrogen storage purpose. In addition to the previously proposed structures, many new low-energy structures of zinc borohydride are found by utilizing the minima-hopping method. We identify a new dynamically stable structure which belongs to the $I4_122$ space group as the most stable phase of zinc borohydride at low temperatures. A low transition barrier between $I4_122$ and $P1$, the two lowest-lying phases of zinc borohydride is predicted, implying that a coexistence of low-lying phases of zinc borohydride is possible at ambient conditions. An analysis based on the simulated X-ray diffraction pattern reveals that the $I4_122$ structure exhibits the same major features as the experimentally synthesized zinc borohydride samples.Comment: Version accepted by Phys. Rev. B. Manuscript has 8 pages, 5 figures, 2 tables (with 6 pages, 5 figures, 2 tables in supplemental material

The relationship between service quality, customer satisfaction and customer loyalty: An investigation in Vietnamese retail banking sector

This study develops and empirically tests the interrelationships between service quality, customer satisfaction, and customer loyalty in a retail banking context. Increasingly intense competitiveness and fundamental changes in the business environment nowadays are forcing firms to implement a customer-focused strategy which raises the importance of customer-related constructs such as customer satisfaction, service quality, and customer loyalty in explaining a firm’s performance. In particular, they are essential for competitiveness in industries where the exchanges are complex and customers are closely involved in the decision-making process, such as the banking industry. In this study, first, a research model about the interrelationships between service quality, customer satisfaction, and customer loyalty is suggested. Then a survey is conducted with retail banking customers about these constructs, which results in 261 valid respondents. The hypotheses are then proposed and tested using confirmatory factor analysis (CFA) and the structural equation modelling technique (SME). The analysis reveals that service quality and customer satisfaction are important antecedents of customer loyalty and customer satisfaction mediates the effects of service quality on customer loyalty. These findings suggest that there are non-linear relationships between three constructs and emphasize the need to treat customer loyalty management as a process which includes plenty of factors interacting with each other.Internal Grant Agency of Faculty of Management and Economics, Tomas Bata University in Zlin [IGA/FaME/2016/020

LES RÔLES DE L'ORGANISATION PAYSANNE ET DE L'ACTION COLLECTIVE POUR LE RENFORCEMENT DES FILIÈRES DE COMMERCIALISATION DES PRODUITS DE «SPÉCIALITÉ LOCALE» LE CAS DU LONGANE «LONG» DE LA PROVINCE DE HUNGYEN AU VIETNAME

N° ISBN - 978-2-7380-1284-5International audienceLe Vietnam est actuellement engagé dans un processus d'intégration économique internationale issue notamment de son adhésion récente à l'OMC. Ce processus inclut une ouverture croissante du secteur agro-alimentaire domestique à la concurrence des produits importés. Les exploitations agricoles familiales sont particulièrement fragilisées par ce nouveau contexte, en raison de le petite taille et du morcellement des superficies cultivables. Les moyens de renforcer la compétitivité des produits issues de l'agriculture familiale constitue ainsi une des priorités pour les recherches vietnamiennes en économie agricole. Au Vietnam, le longane “Long” produit dans la province de Hungyen est un produit de spécialité locale, c'est-à-dire dont la qualité spécifique est reconnue par une partie des consommateurs. Néanmoins, le manque d'action collective entre les exploitations agricoles familiales fragilisent les performances de cette filière face aux longanes des autres régions du Vietnam et les longanes importés. Cet article présente les expériences d'appui pour le renforcement de la filière du longane “Long” de la province de Hungyen au Vietnam vers le développement de l'indication géographique. Grâce à l'appui de GTZ (German Technical Cooperation) et de l'IPSARD (Institut de politique et de stratégie pour l'agriculture et le développement rural), la coopérative de longane Long Hongnam, qui consiste en une organisation de producteurs et de commerçants, a été mise sur pied en 2006. La coopérative a permis la mise en place des actions collectives suivantes: l'application d'un itinéraire technique de production amélioré incluant le respect de certaines bonnes pratiques agricoles locales (Good agricultural practices ou GAP), et la mise sur pied d'un espace de dialogue avec les commerçants. Grace à ce dispositif, les producteurs ont pu augmenter leur prix du vente, améliorer l'homogénéité de la qualité des produits, et améliorer leur revenu. La durabilité de ce dispositif est discutée. L'article fait le bilan des forces et faiblesses de ces strategies de soutien a l'action collective

El trauma de los niños vietnamitas que viven en familias incompletas

Children living in incomplete families have to suffer from more hardships than others including psychological trauma that could never be cured without safe approaches. In this paper, we used the Children Behavior Checklist (CBCL test) by Achenbach to initially filter the incidence of children in incomplete families with psychological trauma, the extent of childhood trauma, and the signs of trauma. Moreover, the Self-esteem scale of Toulouse was also utilized to investigate children's self-esteem and determine the impact of psychological trauma on the self-assessment of children. Based on these tools, the research conducted a correlation analysis of psychological trauma of children in incomplete families through indicators of awareness of, emotions with, and behaviors towards family and social life (self-evaluated by children). The results showed that there are differences in psychological trauma of children in terms of awareness, emotions, and behaviors. The differences allow for a better definition of children's causes, influences, and degrees of psychological trauma. This is the basis for proposing timely filtering solutions and effective psychological support measures for these children. Keywords: correlation analysis; signs of psychological trauma; children; incomplete family; Vietnam.Los niños que viven en familias incompletas tienen que sufrir más dificultades que otros, incluido el trauma psicológico que nunca podría curarse sin enfoques seguros. En este artículo, se utiliza la Lista de Verificación de Comportamiento Infantil (prueba CBCL) de Achenbach para filtrar inicialmente la incidencia de niños en familias incompletas con trauma psicológico, el alcance del trauma infantil y los signos de trauma. Además, la escala de autoestima de Toulouse también se utilizó para investigar la autoestima de los niños y determinar el impacto del trauma psicológico en la autoevaluación de los niños. Con base en estas herramientas, la investigación realizó un análisis de correlación del trauma psicológico de los niños en familias incompletas a través de indicadores de conciencia, emociones y comportamientos hacia la vida familiar y social (autoevaluados por los niños). Los resultados mostraron que existen diferencias en el trauma psicológico de los niños en términos de conciencia, emociones y comportamientos. Las diferencias permiten una mejor definición de las causas, influencias y grados de trauma psicológico de los niños. Esta es la base para proponer soluciones de filtrado oportunas y medidas de apoyo psicológico eficaces para estos niños. Palabras clave: análisis de correlación; signos de trauma psicológico; niños; familia incompleta; Vietnam

Designing a novel heterostructure AgInS₂@MIL-101(Cr) photocatalyst from PET plastic waste for tetracycline degradation

Semiconductor-containing porous materials with a well-defined structure could be unique scaffolds for carrying out selective organic transformations driven by visible light. We herein introduce for the first time a heterostructure of silver indium sulfide (AgInS(2)) ternary chalcogenide and a highly porous MIL-101(Cr) metal–organic framework (MOF) synthesised from polyethylene terephthalate plastic waste. Our results demonstrate that AgInS(2) nanoparticles were uniformly attached to each lattice plane of the octahedral MIL-101(Cr) structure, resulting in a nanocomposite with a high distribution of semiconductors in a porous media. We also demonstrate that the nanocomposite with up to 40% of AgInS(2) doping exhibited excellent catalytic activity for tetracycline degradation under visible light irradiation (∼99% tetracycline degraded after 4 h) and predominantly maintained its performance after five cycles. These results could promote a new material circularity pathway to develop new semiconductors that can be used to protect water from further pollution

Thermodynamic stability of alkali metal/zinc double-cation borohydrides at low temperatures

We study the thermodynamic stability at low temperatures of a series of alkali metal/zinc double-cation borohydrides, including LiZn(BH$_4$)$_3$, LiZn$_2$(BH$_4$)$_5$, NaZn(BH$_4$)$_3$, NaZn$_2$(BH$_4$)$_5$, KZn(BH$_4$)$_3$, and KZn$_2$(BH$_4$)$_5$. While LiZn$_2$(BH$_4$)$_5$, NaZn(BH$_4$)$_3$, NaZn$_2$(BH$_4$)$_5$ and KZn(BH$_4$)$_3$ were recently synthesized, LiZn(BH$_4$)$_3$ and KZn$_2$(BH$_4$)$_5$ are hypothetical compounds. Using the minima-hopping method, we discover two new lowest-energy structures for NaZn(BH$_4$)$_3$ and KZn$_2$(BH$_4$)$_5$ which belong to the $C2/c$ and $P2$ space groups, respectively. These structures are predicted to be both thermodynamically stable and dynamically stable, implying that their existence may be possible. On the other hand, the lowest-energy $P1$ structure of LiZn(BH$_4$)$_3$ is predicted to be unstable, suggesting a possible reason elucidating why this compound has not been experimentally identified. In exploring the low-energy structures of these compounds, we find that their energetic ordering is sensitive to the inclusion of the van der Waals interactions. We also find that a proper treatment of these interactions, e.g., as given by a non-local density functional such as vdW-DF2, is necessary to address the stability of the low-energy structures of these compounds.Comment: Final versio