The lithiation process and Li diffusion in amorphous SiO2 and Si from first-principles

Silicon is considered the next-generation, high-capacity anode for Li-ion energy storage applications, however, despite significant effort, there are still uncertainties regarding the bulk Si and surface SiO2 structural and chemical evolution as it undergoes lithiation and amorphization. In this paper, we present first-principles calculations of the evolution of the amorphous Si anode, including its oxide surface layer, as a function of Li concentration. We benchmark our methodology by comparing the results for the Si bulk to existing experimental evidence of local structure evolution, ionic diffusivity as well as electrochemical activity. Recognizing the important role of the surface Si oxide (either native or artificially grown), we undertake the same calculations for amorphous SiO2, analyzing its potential impact on the activity of Si anode materials. Derived voltage curves for the amorphous phases compare well to experimental results, highlighting that SiO2 lithiates at approximately 0.7 V higher than Si in the low Li concentration regime, which provides an important electrochemical fingerprint. The combined evidence suggests that i) the inherent diffusivity of amorphous Si is high (in the order 10−9cm2s−1 - 10−7cm2s−1), ii) SiO2 is thermodynamically driven to lithiate, such that Li–O local environments are increasingly favored as compared to Si–O bonding, iii) the ionic diffusivity of Li in LiySiO2 is initially two orders of magnitude lower than that of LiySi at low Li concentrations but increases rapidly with increasing Li content and iv) the final lithiation product of SiO2 is Li2O and highly lithiated silicides. Hence, this work suggests that - excluding explicit interactions with the electrolyte - the SiO2 surface layer presents a kinetic impediment for the lithiation of Si and a sink for Li inventory, resulting in non-reversible capacity loss through strong local Li–O bond formation

Optimising a Cyclo Drive

In this report the function of an eccentric drive (Cyclo Drive) is evaluated. The drive transfers torque between two parallel axes. The eccentric drive is used in a differential in an all-wheel drive system made by BorgWarner. The purpose of the Cyclo Drive is to transfer torque between two parallel-displaced axles without eccentric rotation. The mechanism consists of three discs with the middle disc being eccentrically placed relative to the outer ones. During the project, it has become apparent that the middle disc cannot withstand the load, which is the reason a thorough analysis of the system is required. The purpose is to redesign the current mechanism to fulfil the requirements as well as to be of use in future development of similar projects. The first action in the project is to investigate alternative solutions. The idea is to see if there is any other mechanical solution that could replace the Cyclo Drive. During the research some different mechanisms are suggested. These are then evaluated to establish which one most satisfies the expectations. The forces and contact pressures are derived analytically by analysing the geometry, while the calculations are carried out with the assist of MATLAB. The different parameters that define the geometry are varied to see how this affects the structure. The calculated loads are then used to optimise the geometry of structure. A fatigue analysis is conducted on the old and new design to determine whether the changes lead to an improvement. The modifications made includes a small increase of the outer radius, increased thickness, slightly increased hole radius as well as a reduction of number of holes from twelve to elven. In order to maintain the eccentricity an increase of the pin radius was required. The improvements made lead to a structure that is improved compared to the old one, however to be sure of the functionality some real life tests will need to be conducted

Vibration of a circular cylindrical tank containing liquid

Interest in the motion of a liquid contained in a circular cylinder has been generated by the desire to predict the response of a liquid propellent in a moving space vehicle

Boundary Waters

Today, Boston is confronted with three major urban issues each at a different scale: a defunct vestige of the past, a transforming seaport district and an inevitable rising sea level. Each of these urgent confrontations asks Boston to change its disposition of land expansionism and re-examine its narrative of urban development. The Northern Avenue Bridge rests at the nexus of these issues, no longer the conduit of urban progress but now as a part of the problem: a sentimental urban relic that consumes significant resources to maintain its decay. With Boston\u27s rapidly changing urban frontier, we find opportunity to re-activate the bridge by implanting an experimental music hall, a program inherently flexible to music\u27s constant shifting frontier. This architectural intervention transforms the infrastructure from a commercial conduit to a cultural container that responds to the evolving conditions of the city. This coupling of infrastructure from a commercial conduit to a cultural container that responds to the evolving conditions of the city. This coupling of infrastructure and architecture seeks to go beyond simply restoring the bridge\u27s relevance in today\u27s city by equipping it to serve again as a catalyst in the development of the future city. Through this, we establish the Northern Avenue Bridge as Boston\u27s cultural palimpsest

A new challenge for objective uncertainties and the propensity theorist

The paper is concerned with the existence of objective uncertainties. What would it take for objective uncertainties to exist, and what would be the consequences for our understanding of the world we live in? We approach these questions by considering two common theories on how we are to understand the being of propensities and how it pertains to possible outcomes that remain unmanifested. It is argued that both or these theories should be rejected, and be replaced with a theory we call unrestricted actualism according to which the possible outcomes of propensities (whether realized or unrealized) are denizens of the actual world

Climate change, values, and the cultural cognition thesis

Recently the importance of addressing values in discussions of risk perception and adaptation to climate change has become manifest. Values-based approaches to climate change adaptation and the cultural cognition thesis both illustrate this trend. We argue that in the wake of this development it is necessary to take the dynamic relationship between values and beliefs seriously, to acknowledge the possibility of bi-directional relationships between values and beliefs, and to address the variety of values involved (e.g. personal, epistemic and cultural values). The dynamic relationship between values and beliefs, we claim, highlights the need to bring ethical considerations to bear on climate change communication. In particular, we must ask whether it is acceptable to tailor information about the risks of climate change in an effort to maximize communicative effectiveness given the values of the target group

Case depth evaluation of induction-hardened camshaft by using magnetic Barkhausen noise (MBN) method

Magnetic Barkhausen noise (MBN) method is one of the non-destructive\ua0evaluating (NDE) techniques used in industry to monitor the quality of ferromagnetic products during manufacture. In this article, case depth evaluation of the camshaft lobes by this means after induction hardening is described. A\ua0routine industrial monitoring practice is found to have limitation to evaluate the thickness of this process-hardened\ua0layer. With the aid of metallography on selected samples, this uppermost layer is found to have one, or more than one microconstituents. This infers that each type possesses different physical properties in response to the MBN measurement. Consequently, the interpretation of the MBN signal/data for case depth evaluation is not straight-forward.\ua0From metallography, a\ua0qualified component should have a\ua0uniform layer of martensite with grains ≤ 50\ua0\ub5m and the thickness around\ua03.0–5.0\ua0mm. This gives the magnetoelastic parameter (i.e. mp) in a\ua0range of\ua020–70 in industrial MBN measurement. The mp outside this range corresponds to either a\ua0non-martensitic\ua0type or a\ua0martensitic type with grains > 50\ua0\ub5m. In fact, the characteristic features of a\ua0Barkhausen burst like peak intensity, width and position can be used to categorise different microstructural conditions. Then, the case depth of the qualified components, or the thickness of the qualified martensite, can be estimated. Statistical regression decision tree model helps to divide this qualified group into three sub-groups\ua0between 3.0 and\ua06.0\ua0mm, and each can be identified by the decision criteria based on the specific ranges of the mp reading, the RMS of peak intensity and the peak position. In the end, a\ua0physical model is used to show how the difference of microstructures is influencing the magnetic flux, and thus the mp. Nevertheless, more information is needed to improve the model for this application.

Why metaphysicians do not explain

The paper discusses the concept of explanation in metaphysics. Different types of explanation are identified and explored. Scientific explanation is compared with (alleged) metaphysical explanation. The comparison illustrates the difficulties with applying the concept of explanation in metaphysics