Context-Aware Prediction of Derivational Word-forms

Derivational morphology is a fundamental and complex characteristic of language. In this paper we propose the new task of predicting the derivational form of a given base-form lemma that is appropriate for a given context. We present an encoder--decoder style neural network to produce a derived form character-by-character, based on its corresponding character-level representation of the base form and the context. We demonstrate that our model is able to generate valid context-sensitive derivations from known base forms, but is less accurate under a lexicon agnostic setting

The Bifurcated Age-Metallicity Relation of Milky Way Globular Clusters and its Implications For the Accretion History of the Galaxy

We use recently derived ages for 61 Milky Way (MW) globular clusters (GCs) to show that their age-metallicity relation (AMR) can be divided into two distinct, parallel sequences at [Fe/H] \ga -1.8. Approximately one-third of the clusters form an offset sequence that spans the full range in age ($\sim 10.5$--13 Gyr), but is more metal rich at a given age by $\sim 0.6$ dex in [Fe/H]. All but one of the clusters in the offset sequence show orbital properties that are consistent with membership in the MW disk. They are not simply the most metal-rich GCs, which have long been known to have disk-like kinematics, but they are the most metal-rich clusters at all ages. The slope of the mass-metallicity relation (MMR) for galaxies implies that the offset in metallicity of the two branches of the AMR corresponds to a mass decrement of 2 dex, suggesting host galaxy masses of M_{*} \sim 10^{7-8} \msol for GCs that belong to the more metal-poor AMR. We suggest that the metal-rich branch of the AMR consists of clusters that formed in-situ in the disk, while the metal-poor GCs were formed in relatively low-mass (dwarf) galaxies and later accreted by the MW. The observed AMR of MW disk stars, and of the LMC, SMC and WLM dwarf galaxies are shown to be consistent with this interpretation, and the relative distribution of implied progenitor masses for the halo GC clusters is in excellent agreement with the MW subhalo mass function predicted by simulations. A notable implication of the bifurcated AMR, is that the identical mean ages and spread in ages, for the metal rich and metal poor GCs are difficult to reconcile with an in-situ formation for the latter population.Comment: 16 pages, 9 figures, accepted for publication in MNRA

Surprises in High-Dimensional Ridgeless Least Squares Interpolation

Interpolators -- estimators that achieve zero training error -- have attracted growing attention in machine learning, mainly because state-of-the art neural networks appear to be models of this type. In this paper, we study minimum $\ell_2$ norm (``ridgeless'') interpolation in high-dimensional least squares regression. We consider two different models for the feature distribution: a linear model, where the feature vectors $x_i \in {\mathbb R}^p$ are obtained by applying a linear transform to a vector of i.i.d.\ entries, $x_i = \Sigma^{1/2} z_i$ (with $z_i \in {\mathbb R}^p$); and a nonlinear model, where the feature vectors are obtained by passing the input through a random one-layer neural network, $x_i = \varphi(W z_i)$ (with $z_i \in {\mathbb R}^d$, $W \in {\mathbb R}^{p \times d}$ a matrix of i.i.d.\ entries, and $\varphi$ an activation function acting componentwise on $W z_i$). We recover -- in a precise quantitative way -- several phenomena that have been observed in large-scale neural networks and kernel machines, including the "double descent" behavior of the prediction risk, and the potential benefits of overparametrization.Comment: 68 pages; 16 figures. This revision contains non-asymptotic version of earlier results, and results for general coefficient

Master of Science

thesisEnhanced Geothermal Systems (EGS) are geothermal resources that are developed through hydraulic stimulation. Inadequate permeability and production from natural fractures and pores can be overcome via injection of cold water below fracturing pressure, by conventional hydraulic fracturing, or by some cyclic combination of these processes. At low injection rates or where thermal fracturing is being exploited, shearing of pre-existing weaknesses and potentially developing virgin fractures is envisioned to provide permeable, self-propped pathways. Alternatively, injection at pressures substantially above the minimum principal stress can also hydraulically connect, reopen, or create fractures and also possibly induce shearing (as known from microseismic monitoring). The heat from this artificially fractured reservoir is subsequently transferred to the injected fluid and extracted through a production well. Conventional steam turbines or a binary cycle power plants can be employed for electric generation. The technical challenges in developing EGS reservoirs are substantial and include controlling fracture direction and morphology, establishing an adequate heat transfer surface area, and maintaining conductivity. The latter was the focal point of investigation. It is commonly assumed that that the induced fractures will fail by shear and be self-propping. If tensile fractures are generated, they need to be explicitly held open by proppant (and it needs to be ensured that the proppant is not produced back into the wellbore). The conductivity of bauxite-propped fractures over extended periods of time and at elevated temperatures were measured in laboratory tests in order to assess the temporal and thermal dependency of conductivity in a typical surrogate fracture

Wood-Fired Train Kiln

My research focused on constructing a wood-fired train kiln. I utilized ashlar fine tooled masonry techniques to create a dry-stacked formation. Primarily, I analyzed the different materials to which I had access and determined the proper steps to create an ideal structure. In order to accomplish this, I sorted, cut, and shaved various series of both insulating and dense fire bricks to create a perfect fit, an expansion joint or a level surface. If a level surface could not be attained using solely bricks then a compound termed “butter” was applied, but I utilized a high temperature refractory mortar when I required a brick to be held in place. Furthermore, arches are formed to span the door, chamber, firebox and throat of the kiln using skewback along with varying arch brick, and subsequently, a steel frame is used to buttress the arches as well as hold the bricks in place during expansion; for this reason, I ascertained the importance of inspecting the structure to be true, level, flush, and plum. Through my research, I determined it is of the utmost importance one understands everything about their materials on hand; this allowed me to design a kiln to fit together in both a tight and level manner atop an unlevel foundation. I found that the efficiency of building a dry-stacked kiln is reliant upon organizing bricks according to their differences in height by sixteenths of an inch. In addition, a brick saw and several levels must be used with precision accuracy

Non-Contact Torque Transfer Using Ferrofluid

Gearing systems are a mechanical based systems that allow an input shaft torque to increase or decrease when it is transferred as an output shaft. Although the gearing system is an old creation that holds little mysteries in the current day, the complexities used to adapt it to new applications continues to grow. The invention discussed and researched in this paper goes in depth on how the gearing system was redesigned to accommodate new uses along with making the system more efficient. A gearing system uses a solid surface to surface contact to transfer the torque from input to output. Overtime, the solid contact surface deteriorate due to friction and inefficiencies causing the destruction of the system in order to produce longer lasting gearing system that require less maintenance and reduce the wear within the system, a more efficient and durable process must be implemented. This paper discusses the redesign of the common gearing system referred to as the non-contact torque transfer using ferrofluid. The ferrofluid gearing system was created within the bounds specified by the sponsor, Dr. Nassersharif. It has been designed to outlast other gearing systems, making it appeal to the customer demand through implementing magnets and ferrofluid. Through calculations and physical observations, the ferrofluid gearing system proved to work and the design concept is able to be patented