Influence of elastic strain on the thermodynamics and kinetics of lithium vacancy in bulk LiCoO2

The influence of elastic strain on the lithium vacancy formation and migration in bulk LiCoO2 is evaluated by means of first-principles calculations within density functional theory (DFT). Strain dependent energies are determined directly from defective cells and also within linear elasticity theory from the elastic dipole tensor (Gij) for ground state and saddle point configurations. We analyze finite size-effects in the calculation of Gij, compare the predictions of the linear elastic model with those obtained from direct calculations of defective cells under strain and discuss the differences. Based on our data, we calculate the variations in vacancy concentration and mobility due to the presence of external strain in bulk LiCoO2 cathodes. Our results reveal that elastic in-plane and out-of-plane strains can significantly change the ionic conductivity of bulk LiCoO2 by an order of magnitude and thus strongly affect the performance of Li-secondary batteries

Theoretical study of superionic phase transition in Li2S

We have studied temperature-induced superionic phase transition in Li2S, which is one of the most promising Li-S battery cathode material. Concentration of ionic carriers at low and high temperature was evaluated from thermodynamics of defects (using density functional theory) and detailed balance condition (using ab initio molecular dynamics (AIMD)), respectively. Diffusion coefficients were also obtained using AIMD simulations. Calculated ionic conductivity shows that superionic phase transition occurs at T = 900 K, which is in agreement with reported experimental values. The superionic behavior of Li2S is found to be due to thermodynamic reason (i.e. a large concentration of disordered defects)

Communication: Nanosize-induced restructuring of Sn nanoparticles

Stabilities and structures of β- and α-Sn nanoparticles are studied using density functional theory. Results show that β-Sn nanoparticles are more stable. For both phases of Sn, nanoparticles smaller than 1 nm (∼48 atoms) are amorphous and have a band gap between 0.4 and 0.7 eV. The formation of band gap is found to be due to amorphization. By increasing the size of Sn nanoparticles (1–2.4 nm), the degree of crystallization increases and the band gap decreases. In these cases, structures of the core of nanoparticles are bulk-like, but structures of surfaces on the faces undergo reconstruction. This study suggests a strong size dependence of electronic and atomic structures for Sn nanoparticle anodes in Li-ion batteries

Stabilization of the γ-Sn phase in tin nanoparticles and nanowires

Structures of Sn nanoparticles and nanowires are studied using density functional theory in conjunction with thermodynamic considerations. Besides the low-temperature α and room-temperature β phases, the high-temperature γ phase is considered. Results show that at ambient temperatures for sizes smaller than 50 nm, metallic β- and γ-Sn nanoparticles are more stable than semimetallic α-Sn ones because of their lower surface energies. Moreover, very small Sn nanostructures, exemplified by nanowires, are expected to exhibit the γ phase even at 0 K

A Diagnostics Model for Industrial Communications Networks

Over the past twenty years industrial communications networks have become common place in most industrial plants. The high availability of these networks is crucial in smooth plant operations. Therefore local and remote diagnostics of these networks is of primary importance in solving any existing or emerging network problems. Users for most part consider the “plant networks” as black boxes, and often not sure of the actual health of the networks. The major part of the work outlined in this research concentrates on the proposed “Network Diagnostics Model” for local and remote monitoring. The main objective of the research is to aid the establishment of tools and techniques for diagnosis of the industrial networks, with particular emphasis on PROFIBUS and PROFINET. Additionally this research has resulted in development of a number of devices to aid in network diagnostics. The work outlined in this submission contributes to the developments in the area of online diagnostics systems. The development work was conducted in the following phases: 1. Development of Function Block (FB) for diagnosing PROFIBUS network for implementation on PLC. 2. Development of OPC server for diagnosing PROFIBUS network for implementation on PC. 3. Development of a web based diagnostic software for multiple fieldbuses for implementation on imbedded XP platform. 4. Development of OPC server for diagnosing PROFINET network for implementation on PC 5. Conformance testing of masters (PLC) in PROFIBUS network to increase the health of the network. 6. Use of diagnostics tools for performance analysis of fieldbuses networks for high performance applications. The research work outlined in this submission has made a significant and coherent contribution to online diagnostics of fieldbus communications networks, and has paved the way for the introduction of the online diagnostics devices to the market place. It has shown that the proposed model provides a uniform framework for research and development of diagnostics tools and techniques for fieldbus networks. Organizations that use fieldbus should consider installing advanced online diagnostic systems to boost maintenance efficiency and reduce operating costs, and maintain the availability of plant resources. Based on the experience gained over a number of years a multilayer model is proposed for future development of diagnostics tools

First principles studies of the potential-induced lifting of the Au(100) surface reconstruction

The potential-induced surface reconstruction of Au(100) has been studied by a combination of density functional theory and thermodynamic considerations. Surface free energies of reconstructed-(5 x 1) and unreconstructed-(1 x 1) surfaces were calculated as function of an external electric field using the extended ab initio atomistic thermodynamics approach. After relating electric field and electrode potential by using capacitance measurements, we calculate lifting of the reconstruction to occur at 0.58 V in 0.01 M HClO4 and 0.27 V in 0.01 M H2SO4, being in agreement with the experimental values of 0.60 and 0.27 V (vs. SCE). Finally, the consequences of using experimental capacitance measurements for calculating surface free energies are discussed

Regularization of the big bang singularity with random perturbations

We show how to regularize the big bang singularity in the presence of random perturbations modeled by Brownian motion using stochastic methods. We prove that the physical variables in a contracting universe dominated by a scalar field can be continuously and uniquely extended through the big bang as a function of time to an expanding universe only for a discrete set of values of the equation of state satisfying special co-prime number conditions. This result significantly generalizes a previous result \cite{Xue:2014} that did not model random perturbations. This result implies that the extension from a contracting to an expanding universe for the discrete set of co-prime equation of state is robust, which is a surprising result. Implications for a purely expanding universe are discussed, such as a non-smooth, randomly varying scale factor near the big bang.Comment: 21 pages, 4 figure

An Audit of Emergency Department Accreditation Based on Joint Commission International Standards (JCI)

Introduction: Despite thousands of years from creation of medical knowledge, it not much passes from founding the health care systems. Accreditation is an effective mechanism for performance evaluation, quality enhancement, and the safety of health care systems. This study was conducted to assess the results of emergency department (ED) accreditation in Shohadaye Tajrish Hospital, Tehran, Iran, 2013 in terms of domesticated standards of joint commission international (JCI) standards. Methods: This is a cohort study with a four months follow up which was conducted in the ED of Shohadaye Tajrish hospital in December 2013. The standard evaluation check list of Iran hospitals (based on JCI standards) included 24 heading and 337 subheading was used for this purpose. The effective possible causes of weak spots were found and their solutions considered. After correction, assessment of accreditation were repeated again. Finally, the achieved results of two periods were analyzed using SPSS version 20. Results: Quality improvement, admission in department and patient assessment, competency and capability test for staffs, collection and analysis of data, training of patients, and facilities had the score of below 50%. The mean of total score for accreditation in ED in the first period was 60.4±30.15 percent and in the second period 68.9±22.9 (p=0.005). Strategic plans, head of department, head nurse, resident physician, responsible nurse for the shift, and personnel file achieved the score of 100%. Of total headings below 50% in the first period just in two cases, collection and analysis of data with growth of 40% as well as competency and capability test for staffs with growth of 17%, were reached to more than 50%. Conclusion: Based on findings of the present study, the ED of Shohadaye Tajrish hospital reached the score of below 50% in six heading of quality improvement, admission in department and patient assessment, competency and capability test for staffs, collection and analysis of data, training of patients, and facilities. While, the given score in strategic plans, head of department, head nurse, resident physician, responsible nurse for the shifts, and personnel file was 100%

Structure of palladium nanoparticles under oxidative conditions

Using density functional theory (DFT) and thermodynamic considerations we study the shape and stability of Pd nanoparticles in oxygen-lean and oxygen- rich atmospheres. We find that at very high oxygen coverage cubes exposing (100) faces will form, which are stabilized due to the formation of a Image o/√(5) x √(5)R27° overlayer. The shape of oxygen-covered Pd and Pt nanoparticles is compared in this study