Proton exchange membrane electrolysis sustained by water vapor

The current–voltage characteristics of a proton exchange membrane (PEM) electrolyzer constructed with an IrRuOx water oxidation catalyst and a Pt black water reduction catalyst, under operation with water vapor from a humidified carrier gas, have been investigated as a function of the gas flow rate, the relative humidity, and the presence of oxygen. The performance of the system with water vapor was also compared to the performance when the device was immersed in liquid water. With a humidified Ar(g) input stream at 20 °C, an electrolysis current density of 10 mA cm^(−2) was sustained at an applied voltage of ~ 1.6 V, with a current density of 20 mA cm^(−2) observed at ~ 1.7 V. In the system evaluated, at current densities >40 mA cm^(−2) the electrolysis of water vapor was limited by the mass flux of water to the PEM. At <40 mA cm^(−2), the electrolysis of water vapor supported a given current density at a lower applied bias than did the electrolysis of liquid water. The relative humidity of the input carrier gas strongly affected the current–voltage behavior, with lower electrolysis current density attributed to dehydration of the PEM at reduced humidity values. The results provide a proof-of-concept that, with sufficiently active catalysts, an efficient solar photoelectrolyzer could be operated only with water vapor as the feedstock, even at the low operating temperatures that may result in the absence of active heating. This approach therefore offers a route to avoid the light attenuation and mass transport limitations that are associated with bubble formation in these systems

A Qualitative Representation of Spatial Scenes in R2 with Regions and Lines

Regions and lines are common geographic abstractions for geographic objects. Collections of regions, lines, and other representations of spatial objects form a spatial scene, along with their relations. For instance, the states of Maine and New Hampshire can be represented by a pair of regions and related based on their topological properties. These two states are adjacent (i.e., they meet along their shared boundary), whereas Maine and Florida are not adjacent (i.e., they are disjoint). A detailed model for qualitatively describing spatial scenes should capture the essential properties of a configuration such that a description of the represented objects and their relations can be generated. Such a description should then be able to reproduce a scene in a way that preserves all topological relationships, but without regards to metric details. Coarse approaches to qualitative spatial reasoning may underspecify certain relations. For example, if two objects meet, it is unclear if they meet along an edge, at a single point, or multiple times along their boundaries. Where the boundaries of spatial objects converge, this is called a spatial intersection. This thesis develops a model for spatial scene descriptions primarily through sequences of detailed spatial intersections and object containment, capturing how complex spatial objects relate. With a theory of complex spatial scenes developed, a tool that will automatically generate a formal description of a spatial scene is prototyped, enabling the described objects to be analyzed. The strengths and weaknesses of the provided model will be discussed relative to other models of spatial scene description, along with further refinements

Meaningfulness as Sensefulness

It is only in the last few decades that analytic philosophers in particular have begun to pay any serious attention to the topic of life’s meaning. Such philosophers, however, do not usually attempt to answer or analyse the traditional question ‘What is the meaning of life?’, but rather the subtly different question ‘What makes a life meaningful?’ and it is generally assumed that the latter can be discussed independently of the former. Nevertheless, this paper will argue that the two questions are indeed connected, and that identifying and expanding upon the most plausible analysis of the former will provide the resources necessary to determine the most plausible answer to the latter. Specifically, this paper will argue that the traditional question is simply a request for the information which constitutes a coherent answer to one or more of a certain set of questions regarding human existence that were salient to the asker. In simpler language, the meaning of life itself is the information a person needs to make sense of it. This analysis can then also be applied to individual lives, such that asking for the meaning of X’s life is an analogous request for the information necessary to make sense of that life in particular. Running with this concept of the ‘meaning’ of something as its ‘sense’, the paper then outlines an accompanying theory of ‘meaningfulness’ as ‘sensefulness’: a measure of the richness of certain aspects of the life, multiplied by their intelligibility

Is the desire for a meaningful life a selfless desire?

Susan Wolf defines a meaningful life as one that is somewhat successfully engaged in promoting positive value. I grant this claim; however, I disagree with Wolf’s theory about why we desire meaningfulness, so understood. She suggests that the human desire for meaningfulness is derived from an awareness of ourselves as equally insignificant in the universe and a resulting anti-solipsistic concern for promoting goodness outside the boundaries of our own lives. I accept that this may succeed in explaining why people want to engage in projects that happen to be meaningful. Nevertheless, I argue that Wolf fails to explain why people have a desire for meaningfulness itself. In other words, she has told us one reason we may be motivated to promote positive value, but not why we personally want to be the people who promote it—why we think it is a good thing that meaningful acts be done, but not why we want them to be our meaningful acts. In detailing my response, I follow Wolf in relating our desire for meaningfulness to a kind of love-based motivation. However, I argue that it has more in common with a selfish form of love than the altruistic kind of love proposed by Wolf. Finally, I suggest an alternative explanation which I believe can more fully account for our desire for meaningfulness: the prospect of disappearing from the universe without a trace makes us anxious, so we pursue meaningful achievements in an attempt to make our own physical deaths less final

Quantified Boolean Formulas: Proof Complexity and Models of Solving

Quantified Boolean formulas (QBF), which form the canonical PSPACE-complete decision problem, are a decidable fragment of first-order logic. Any problem that can be solved within a polynomial-size space can be encoded succinctly as a QBF, including many concrete problems in computer science from domains such as verification, synthesis and planning. Automated solvers for QBF are now reaching the point of industrial applicability. In this thesis, we focus on dependency awareness, a dedicated solving paradigm for QBF. We show that dependency schemes can be envisaged in terms of dependency quantified Boolean formulas (DQBF), exposing strong connections between these two previously disparate entities. By introducing new lower-bound techniques for QBF proof systems, we study the relative strengths of models of dependency-aware solving, including the proposal of new, stronger models. Proof Complexity: Using the strategy extraction paradigm, we introduce new lower-bound techniques that apply to resolution-based QBF proof systems. In particular, we use the technique to prove exponential lower bounds for a new family of QBFs called the equality formulas. Our technique also affords considerably simpler, more intuitive proofs of some existing QBF proof-size lower bounds. Models of Solving: We apply our lower bound techniques to show new separations for QBF proof systems parametrised by dependency schemes. We also propose new models of dynamic dependency-aware solving and prove that they are exponentially stronger than the existing static models. Finally, we introduce Merge Resolution, a proof system modelling CDCL-style solving for DQBF, which is the first of its kind

Can Only Human Lives Be Meaningful?

Duncan Purves and Nicolas Delon have argued that one’s life will be meaningful to the extent that one contributes to valuable states of affairs and this contribution is a result of one’s intentional actions. They then argue, contrary to some theorists’ intuitions, that non-human animals are capable of fulfilling these requirements, and that this finding might entail important things for the animal ethics movement. In this paper, I also argue that things besides human beings can have meaningful existences, but I disagree with Purves and Delon’s theory of meaning, and some of the practical implications they suggest arise from their conclusion. Specifically, I argue that Purves and Delon are wrong to suggest that intentional agency is necessary for one’s life to be meaningful; contributing to valuable states of affairs can be sufficient by itself. Purves and Delon’s objection to such a claim is that it would allow even inanimate objects’ existences to count as meaningful. However, while I accept this consequence, I argue that it only seems counterintuitive because of two false beliefs they appear to hold: that some X cannot have a meaningful existence without that meaning (a) making X better off or (b) giving X reasons for pride

Development of a pneumatic three finger gripper that will incorperate a force feedback control system [abstract]

Abstract only availableIn this project I was given the task of designing a three finger gripper. This gripper was to be mounted on one of the Puma 200 robotic arms that is currently in use in the Electrical and Computer Engineering robotics laboratory. The gripper was designed to have three fingers to increase its ability to handle irregularly shaped objects while keeping the design complexity to a minimum. A pneumatic actuator was chosen to drive this device in order to incorporate force feedback into the control of the gripper. Force feedback is desirable because it allows the gripper to apply minimal force to an object in order to pick it up without damaging it. With all of the details of the gripper designed, the next step will be to create the force feedback control system for the gripper so that it will be able to function in the classroom.College of Engineering Undergraduate Research Optio

The impact of uncertainty in agriculture

Income uncertainty in the rural economy is widely considered an important impediment to growth in poor countries. This paper uses a rich dataset on productivity, land use, and output for 17 different crops across 500,000 plots of land in 87 countries to study the impact of uncertainty in the agricultural sector. The analysis relies on historical variability in crop productivity driven by local climatic conditions to estimate the impact of uncertainty on farmers’ land allocation. Applying a standard portfolio framework, we estimate that the incentive to diversify led to large losses in agricultural revenue. We adopt a spatial regression discontinuity approach that compares how national institutions affected agricultural outcomes near the borders of former British and French colonies in Africa. We find that farmers in former British colonies, which tended to adopt pro-private sector policies, adopted more advanced input technologies and achieved higher crop-specific returns. In contrast, farmers in former French colonies, which tended to devote more public resources to the agricultural sector, tolerated higher levels of uncertainty and adopted more specialized crop portfolios. These offsetting effects suggest that both a well-functioning market system along with public investments that reduce risk may be necessary to foster rural economic development