Modeling Nucleation and Growth of Zinc Oxide During Discharge of Primary Zinc-Air Batteries

Metal-air batteries are among the most promising next-generation energy storage devices. Relying on abundant materials and offering high energy densities, potential applications lie in the fields of electro-mobility, portable electronics, and stationary grid applications. Now, research on secondary zinc-air batteries is revived, which are commercialized as primary hearing aid batteries. One of the main obstacles for making zinc-air batteries rechargeable is their poor lifetime due to the degradation of alkaline electrolyte in contact with atmospheric carbon dioxide. In this article, we present a continuum theory of a commercial Varta PowerOne button cell. Our model contains dissolution of zinc and nucleation and growth of zinc oxide in the anode, thermodynamically consistent electrolyte transport in porous media, and multi-phase coexistance in the gas diffusion electrode. We perform electrochemical measurements and validate our model. Excellent agreement between theory and experiment is found and novel insights into the role of zinc oxide nucleation and growth and carbon dioxide dissolution for discharge and lifetime is presented. We demonstrate the implications of our work for the development of rechargeable zinc-air batteries.Comment: 16 pages, 8 figures, Supplementary Information uploaded as ancillary fil

What is to be Done?

If the question is: what is to be done for philosophy?, then it calls for a political answer and I have little to say besides the obvious. If the question is: what is to be done in philosophy?, then I’m stuck. Drawing up a list of to-do’s and not-to-do’s would not, I think, be a good way to honor the general conception of philosophy that inspired Topoi throughout these years, and that I deeply share

Optimal water allocation for joint sustainability of irrigated agriculture and urban growth

2017 Fall.Includes bibliographical references.Historically, agriculture was the main water consumer in Colorado. But the state's demand for water has increased because of rapid urban growth and development of oil and gas industry. Urban communities started buying agricultural water rights to satisfy their growing demands. However, alternative land uses for farms without water right are limited and often they are left fallow. Colorado's newly finalized water plan recognizes agriculture dry-up as one of the primary water challenges of the state and supports projects that explore alternatives to the permanent transfer of agricultural water rights to municipal and industrial users. This research has investigated deficit irrigation and limited irrigation strategies as methods of reducing farm water consumption as well as methods of temporary transfer of water, viable under Colorado's Water Law. These two sets of information formed a conceptual framework for defining an effective transfer method. An economic model was developed to determine optimal water partitioning between on-farm water uses and off-farm water renting. The model proves partitioning water is only optimal when crop water production function is concave; for linear functions the optimal option is to allocate all farm water to the most profitable. Field experimentation has determined the effect of water scarcity on agricultural production and revenue. In particular, crop yield response to water stress was quantified in experimental farms for three common crops in Colorado: corn, sunflower, and sorghum-sudangrass. The filed observations support a linear crop water production function for sorghum-sudangrass and a concave function for corn and sunflower with corn function being more concave than sunflower function. The economic model was used for South Platte River Basin to determine the minimum renting price of water for water partitioning to be optimal. The results show current renting prices of water in South Platte River Basin are too low and need to increase to more than six times before partitioning of water becomes a worthwhile practice. It was also concluded that two set of engineering tools are required for implementation of deficit irrigation; 1) tools to accurately apply desired amount of water, and 2) tools to measure farm consumptive use on a daily basis. At institutional level, Colorado Water Law's no-injury and anti-speculation rules need to be simplified for deficit irrigation to be a worthwhile alternative method to buy-and-dry

The Naming of Facts

"The naming of facts is a difficult matter / it isn’t just one of your holiday games / You may think at first I’m as mad as a hatter / When I tell you, a fact may have TWO DIFFERENT NAMES." A versification of a disturbing philosophical tribulation, after T. S. Eliot’s ‘The Naming of Cats

The Vagueness of ‘Vague’: Rejoinder to Hull

Is ‘vague’ vague? Why so much fuss about a single word? One reason, I think, is that a lot depends on how we settle the question. For example, Frege famously remarked that logic must be restricted to non-vague predicates. But if ‘vague’ is vague, then so is ‘non-vague’, hence the restriction is itself vague and, therefore, helpless. For another example, incoherence theorists such as Unger have claimed that vague terms have no clear instances, blocking the sorites paradox at the base step. If ‘vague’ is vague, however, then either it is a clear instance of itself, in which case the incoherentist claim is plainly false, or it has an empty extension, in which case the claim is vacuously true (there are no vague predicates) and the paradox strikes back. Finally, if ‘vague’ is vague, then—as Hyde has argued—vague predicates must suffer from the phenomenon of higher-order vagueness (at least some must, if Tye is right). So I agree with Hull: this is no small issue and we need to look at it closel

Cover To Cover

A dialogue on the ethics of musical covers and pop songwriting inspired by classical music

Ontological Commitment and Reconstructivism

Some forms of analytic reconstructivism take natural language (and common sense at large) to be ontologically opaque: ordinary sentences must be suitably rewritten or paraphrased before questions of ontological commitment may be raised. Other forms of reconstructivism take the commitment of ordinary language at face value, but regard it as metaphysically misleading: common-sense objects exist, but they are not what we normally think they are. This paper is an attempt to clarify and critically assess some common limits of these two reconstructivist strategies

Mereological Commitments

We tend to talk about (refer to, quantify over) parts in the same way in which we talk about whole objects. Yet a part is not something to be included in an inventory of the world over and above the whole to which it belongs, and a whole is not something to be included in an inventory over and above its own parts. This paper is an attempt to clarify a way of dealing with this tension which may be labeled the Minimalist View: an element in the field of a part-whole relation is to be included in an inventory of the world if, and only if, it does not overlap any other element that is itself included in the inventory. As it turns out, a clarification of this view involves both a defense of mereological extensionality and an account of the topological distinction between detached and undetached parts (and the parallel opposition between scattered and connected wholes)

Beth Too, but Only If

Today’s test will be on the conditional connective. As always, I will just give you a sentence in English and you will have to symbolize it in the language of sentential logic. Remember that symbolization is a procedure whereby you extract the logical form of a sentence. This is not just a translation procedure and there is no straightforward algorithm for it; it sometimes involves a difficult process of interpretation. But it is crucially important for logic, for the logical techniques that we are going to develop will apply to well-formed formulas of the language of sentential logic and only indirectly to the sentences of English. It will apply, that is, to the logical forms of the sentences of English