The disruption and electrification of liquid jets

Imperial Users onl

Invariant Models for Causal Transfer Learning

Methods of transfer learning try to combine knowledge from several related tasks (or domains) to improve performance on a test task. Inspired by causal methodology, we relax the usual covariate shift assumption and assume that it holds true for a subset of predictor variables: the conditional distribution of the target variable given this subset of predictors is invariant over all tasks. We show how this assumption can be motivated from ideas in the field of causality. We focus on the problem of Domain Generalization, in which no examples from the test task are observed. We prove that in an adversarial setting using this subset for prediction is optimal in Domain Generalization; we further provide examples, in which the tasks are sufficiently diverse and the estimator therefore outperforms pooling the data, even on average. If examples from the test task are available, we also provide a method to transfer knowledge from the training tasks and exploit all available features for prediction. However, we provide no guarantees for this method. We introduce a practical method which allows for automatic inference of the above subset and provide corresponding code. We present results on synthetic data sets and a gene deletion data set

Modernization in the Virginia General Assembly : the Commission on the Legislative Process 1972-73

Of the forces which led to institutional modernization in the Virginia General Assembly in the early 1970\u27s, the Commission on the Legislative Process was one of the most significant. The Commission focused its attention on those administrative, managerial and structural problems which were among the most significant impedi­ ments to the Assembly\u27s efficient operation. In the administrative and managerial areas the Commission had great success. Administrative improvements in staff support were especially significant. Staff support was recommended and subsequently approved for individual legislators, standing committees and the Assembly as a whole

How deep is deep enough? -- Quantifying class separability in the hidden layers of deep neural networks

Deep neural networks typically outperform more traditional machine learning models in their ability to classify complex data, and yet is not clear how the individual hidden layers of a deep network contribute to the overall classification performance. We thus introduce a Generalized Discrimination Value (GDV) that measures, in a non-invasive manner, how well different data classes separate in each given network layer. The GDV can be used for the automatic tuning of hyper-parameters, such as the width profile and the total depth of a network. Moreover, the layer-dependent GDV(L) provides new insights into the data transformations that self-organize during training: In the case of multi-layer perceptrons trained with error backpropagation, we find that classification of highly complex data sets requires a temporal {\em reduction} of class separability, marked by a characteristic 'energy barrier' in the initial part of the GDV(L) curve. Even more surprisingly, for a given data set, the GDV(L) is running through a fixed 'master curve', independently from the total number of network layers. Furthermore, applying the GDV to Deep Belief Networks reveals that also unsupervised training with the Contrastive Divergence method can systematically increase class separability over tens of layers, even though the system does not 'know' the desired class labels. These results indicate that the GDV may become a useful tool to open the black box of deep learning

Guaranteed Employment Plans

Att skapa genom att koda är ett nytt och spännande sätt att gestalta konst, lära sig att koda eller bara ha roligt. Denna rapports syfte är att utforska hur en sådan upplevelse kan göras mer interaktiv och intuitiv för användaren samt hur sådan funktionalitet kan implementeras. Som bas för detta ligger en explorativ fallstudie av det arbete som projektgruppen har utfört för att förbättra hemsidan för CodeArt. Det visar sig att ökad användarupplevelse kan uppnås med hjälp av implementation av olika verktyg och funktioner, i detta fall livekodning, versionshantering, hjälptexter och ett loggningsverktyg

Fluctuations in the homogenization of the Poisson and Stokes equations in perforated domains

We study the homogenization problem of the Poisson and Stokes equations in $\mathbb{R}^3$ perforated by $m$ spherical holes, identically and independently distributed. In the critical regime when the radii of the holes are of order $m^{-1}$, we consider the fluctuations of the solutions $u_m$ around the homogenization limit $u$. In the central limit scaling, we show that these fluctuations converge to a Gaussian field, locally in $L^2(\mathbb{R}^3)$, with an explicit covariance.Comment: 40 page

Spin-Polarized Electrons in Monolayer MoS2_2

The optical susceptibility is a local, minimally-invasive and spin-selective probe of the ground state of a two-dimensional electron gas. We apply this probe to a gated monolayer of MoS$_2$. We demonstrate that the electrons are spin polarized. Of the four available bands, only two are occupied. These two bands have the same spin but different valley quantum numbers. We argue that strong Coulomb interactions are a key aspect of this spontaneous symmetry breaking. The Bohr radius is so small that even electrons located far apart in phase space interact, facilitating exchange couplings to align the spins

Quantum confined Stark effect in a MoS2_2 monolayer van der Waals heterostructure

The optics of dangling-bond-free van der Waals heterostructures containing transition metal dichalcogenides are dominated by excitons. A crucial property of a confined exciton is the quantum confined Stark effect (QCSE). Here, such a heterostructure is used to probe the QCSE by applying a uniform vertical electric field across a molybdenum disulfide (MoS$_2$) monolayer. The photoluminescence emission energies of the neutral and charged excitons shift quadratically with the applied electric field provided the electron density remains constant, demonstrating that the exciton can be polarized. Stark shifts corresponding to about half the homogeneous linewidth were achieved. Neutral and charged exciton polarizabilities of (7.8~\pm~1.0)\times 10^{-10}~\tr{D~m~V}^{-1} and (6.4~\pm~0.9)\times 10^{-10}~\tr{D~m~V}^{-1} at relatively low electron density (8 \times 10^{11}~\tr{cm}^{-2}) have been extracted, respectively. These values are one order of magnitude lower than the previously reported values, but in line with theoretical calculations. The methodology presented here is versatile and can be applied to other semiconducting layered materials as well

Decentralization and Solid Waste Management in Urbanizing Ghana: Moving beyond the Status Quo

Waste management is competing with more pressing economic and social issues such as social protection programs, education, and health. The government of Ghana has therefore decentralized the waste management system in the country. With this development, local government authorities and private sector actors are now playing key roles in waste management in the country. This study sought to examine decentralized solid waste management in the Berekum and Dormaa Municipalities in the Brong Ahafo Region of Ghana. Specifically, it analyzed the involvement of the private sector in solid waste management, and the quality of waste management services in the two selected municipalities. Through a survey of 312 households, the study analyzed the performance improvement, regulatory policy, and sustainable service delivery of solid waste management in the municipalities. The study found that there were no mechanisms for full cost recovery to include majority of the residents, who patronize communal collection service. The study therefore recommends the adherence to normative standards and agreed rules, adoption, and use of appropriate cost recovery strategies for low-income groups as well as the restructuring of institutional arrangements to ensure user involvement and enforcement of legislation to improve municipal solid waste management in Ghana