Density functional theory study of LaMnO3 and its competing oxides: an insight into a prospective alkaline fuel cell cathode

LaMnO3 is an inexpensive alternative to precious metals (e.g. platinum) as a catalyst for the oxygen reduction reaction (ORR) in alkaline fuel cells (AFCs). In fact, recent studies have shown that among a range of non-noble metal catalysts, LaMnO3 provides the highest catalytic activity. However, further development of this catalyst is limited by the fact that very little is known about LaMnO3 in the AFC environment. While it has been established that the bulk phase possesses an orthorhombic structure, it has not been possible to determine the structure of the surfaces or the sites active towards the ORR. In this work, therefore, periodic hybrid-exchange (B3LYP) density functional calculations are performed in order to understand the origins of the catalytic activity of LaMnO3. The long term goal is to suggest strategies for optimising the activity of LaMnO3 through control of its crystallite morphology. Initially, the phase stability of LaMnO3 with respect to its competing (La, Mn) oxides is determined by accurate calculation of the Gibbs formation energies of each compound (1.6% mean error). The accuracy achieved is higher than in previous literature, validating the methodology adopted and the reliability of the chemical potentials determined to limit the stability of the bulk and surfaces of LaMnO3. Having determined the ground state of each Mn oxide it was possible to simulate electron energy-loss spectroscopy (EELS) for Mn in different valence states and local environments. The simulated EELS demonstrated that it is possible to identify its oxidation state and local coordination (i.e. the surface structure) on LaMnO3 surface terminations, based on the shift and shape of predicted L3 edges, which correlate well with measured EEL spectra. Calculations of the low-index, stoichiometric and non-polar surfaces of LaMnO3 were then performed in order to predict the equilibrium crystal morphology. For each low energy surface the adsorption sites were also identified. The energetics of the surfaces are rationalised in terms of the cleavage of Jahn-Teller distorted Mn-O bonds, the compensation of undercoordination for ions in the terminating layer and relaxation effects. Finally the adsorption sites identified are investigated by adsorption of molecular O2. The binding energies, adsorbate structure and charge transfer are analysed to predict the reactivity of each site. Results indicate that Jahn-Teller distortion and the coordination of Mn sites modulate the binding strength of O2. The main results presented are the crystallite morphology, the identification of surface reaction sites and the chemical characterisation of those sites. This is a theoretical characterisation of the LaMnO3 catalyst providing detailed atomistic information that has not been possible to deduce from experiment.Open Acces

PENENTUAN PREDIKSI JUMLAH GERHANA MATAHARI DENGAN ARGUMEN LINTANG BULAN DAN ARITMATIKA

Variation in the number of solar eclipses is one of the number phenomena that occurs every year. Territorially, eclipses can occur and be observed once or twice and globally, solar eclipses can occur in quantities of 2 until 5. There are several literatures that say the minimum-maximum number is different from the data above. With a statistical approach, this paper examines one of the important components of the initial eclipse prediction algorithm, which is the value of the argument of moon’s latitude symbolized by large F and through arithmetic used to find a pattern of variations in a number. There are two interesting findings, the first argument of moon’s latitude value has a regular number pattern on each lunation, which is increased by 30,6705. Second, if in general people have to predict eclipses every month, then this study suffices data from the beginning of the new moon in a year, to be able to find out the eclipse in the months after or before.Variation in the number of solar eclipses is one of the number phenomena that occurs every year. Territorially, eclipses can occur and be observed once or twice and globally, solar eclipses can occur in quantities of 2 until 5. There are several literatures that say the minimum-maximum number is different from the data above. With a statistical approach, this paper examines one of the important components of the initial eclipse prediction algorithm, which is the value of the argument of moon’s latitude symbolized by large F and through arithmetic used to find a pattern of variations in a number. There are two interesting findings, the first argument of moon’s latitude value has a regular number pattern on each lunation, which is increased by 30,6705. Second, if in general people have to predict eclipses every month, then this study suffices data from the beginning of the new moon in a year, to be able to find out the eclipse in the months after or before

A Cloud-based Framework for Quality Assurance and Enhancement as a Service (QAEaaS) for Universities with Blended Learning Approach

The dynamic and multi-dimensional quality assurance process for Saudi higher education institutes under the National Commission for Academic Accreditation and Assessment (NCAAA) demands an integrated framework for management and support of internal quality reviews and evidence-based self -studies in a cost-effective way. Due to cross-institutional involvement, quality assurance compliance with NCAAA standards is even more challenging for institutes offering courses with blended learning paradigm in multiple campuses. This papers proposes a Cloud-based framework to realize Quality Assurance and Enhancement as a Service (QAEaaS) to facilitate the internal quality reviews by providing efficient data management and effective communication for different stakeholders. Architecture of the proposed framework is described with respective features to cope with the identified quality assurance challenges and issues faced by the Saudi higher education institutes

Phytochemical analysis and antimicrobial activities of methanolic extracts of leaf, stem and root from different varieties of Labisa pumila Benth.

A local herb, Kacip Fatimah, is famous amongst Malay women for its uses in parturition; however, its phytochemical contents have not been fully documented. Therefore, a study was performed to evaluate the phenolics, flavonoids, and total saponin contents, and antibacterial and antifungal properties of the leaf, stem and root of three varieties of Labisia pumila Benth. Total saponins were found to be higher in the leaves of all three varieties, compared to the roots and stems. Leaves of var. pumila exhibited significantly higher total saponin content than var. alata and lanceolata, with values of 56.4, 43.6 and 42.3 mg diosgenin equivalent/g dry weight, respectively. HPLC analyses of phenolics and flavonoids in all three varieties revealed the presence of gallic acid, caffeic acid, rutin, and myricetin in all plant parts. Higher levels of flavonoids (rutin, quercitin, kaempferol) were observed in var. pumila compared with alata and lanceolata, whereas higher accumulation of phenolics (gallic acid, pyrogallol) was recorded in var. alata, followed by pumila and lanceolata. Antibacterial activities of leaf, stem and root extracts of all varieties determined against both Gram positive (Micrococcus luteus, Bacillus subtilis B145, Bacillus cereus B43, Staphylococcus aureus S1431) and Gram negative (Enterobacter aerogenes, Klebsiella pneumonia K36, Escherichia coli E256, Pseudomonas aeruginosa PI96) pathogens showed that crude methanolic extracts are active against these bacteria at low concentrations, albeit with lower antibacterial activity compared to kanamycin used as the control. Antifungal activity of methanolic extracts of all plant parts against Fusarium sp., Candida sp. and Mucor using the agar diffusion disc exhibited moderate to appreciable antifungal activities compared to streptomycin used as positive control

A Study of Form and Content of Private Speech Used by Iranian EFL Learners

From the sociocultural point of view, the investigation of private speech is important in seeing how the mind works. Yet, not much is known about the form and content of private speech. A group of English language learners were required to talk about some topics of their reading courses. Their voices were recorded and the private speech used by them were identified. It was found that the main role of the loud and silent forms of the private speech in the data is to help learners manage the interaction. Private speech is embedded within the speech context and it needs to be explained in the context in which it happens

Emergency response network design for hazardous materials transportation with uncertain demand

Transportation of hazardous materials play an essential role on keeping a friendly environment. Every day, a substantial amount of hazardous materials (hazmats), such as flammable liquids and poisonous gases, need to be transferred prior to consumption or disposal. Such transportation may result in unsuitable events for people and environment. Emergency response network is designed for this reason where specialist responding teams resolve any issue as quickly as possible. This study proposes a new multi-objective model to locate emergency response centers for transporting the hazardous materials. Since many real-world applications are faced with uncertainty in input parameters, the proposed model of this paper also assumes that reference and demand to such centre is subject to uncertainty, where demand is fuzzy random. The resulted problem formulation is modelled as nonlinear non-convex mixed integer programming and we used NSGAII method to solve the resulted problem. The performance of the proposed model is examined with several examples using various probability distribution and they are compared with the performance of other existing method

ODABIR NAJPRIKLADNIJEGA NAČINA BUŠENJA I MINIRANJA UPOTREBOM MADM METODA (STUDIJA SLUČAJA: RUDNIK ŽELJEZA SANGAN, IRAN)

Drilling is the first stage of open pit mining that has a considerable effect on the other stages of mining, including blasting, loading, hauling and crushing. An unsuitable drilling pattern may lead to undesirable results such as poor fragmentation, back break and fly rock that not only results in technical and safety issues but also increases the operating cost of the mine. Multi-Attribute Decision-Making (MADM) methods can be useful approaches to select the appropriate drilling pattern among various alternatives, performed previously. This paper aims to select the most proper drilling and blasting pattern for Sangan Iron Mine, Iran. To achieve this, in the first step, rock fragmentation, back break, fly rock, specific charge and specific drilling were considered as the decision criteria and their degree of importance was calculated using the AHP method under a fuzzy environment. Then, TOPSIS and PROMETHEE methods were used to select the most proper alternative. The results of this study show that the drilling pattern with a spacing of 5 m, burden 4 m, hole depth 10 m, and hole diameter 15 cm is the most suitable one. The stemming length and powder factor of the suggested pattern are 2.3 m and 2.6 gr/cm3, respectively.Bušenje je prva faza površinske eksploatacije koja ima znatan utjecaj na ostale faze rudarenja, uključujući miniranje, utovar, transport i drobljenje. Neprimjeren način bušenja može dovesti do nepoželjnih rezultata poput loše fragmentacije, povratnoga loma i odbacivanja stijena, što ne samo da rezultira tehničkim i sigurnosnim problemima, već i povećava operativne troškove rudnika. Metode donošenja odluka s više atributa (MADM) mogu biti korisne za odabir odgovarajućega načina bušenja među raznim prethodno izvedenim alternativama. Cilj je ovoga rada odabrati najpogodniji način bušenja i miniranja za rudnik željeza Sangan, Iran. Da bi se to postiglo, u prvome koraku kao kriteriji za odlučivanje razmatrani su fragmentacija stijena, povratno lomljenje, odbacivanje stijena, specifično punjenje i specifično bušenje, a njihova važnost izračunana je korištenjem AHP metode u neizrazitome okruženju. Zatim su korištene metode TOPSIS i PROMETHEE za odabir najprikladnije alternative. Rezultati ove studije pokazuju da je najprikladniji način bušenja s razmakom od 5 m, opterećenjem od 4 m, dubinom rupe od 10 m i promjerom rupe od 15 cm. Duljina čepa bušotine i specifična potrošnja eksploziva predloženoga uzorka iznose 2,3 m, odnosno 2,6 g/cm3