City University London

About: City University London is a education organization based out in London, United Kingdom. It is known for research contribution in the topics: Population & Context (language use). The organization has 5735 authors who have published 17285 publications receiving 453290 citations.

Training Recurrent Neural Networks With the Levenberg–Marquardt Algorithm for Optimal Control of a Grid-Connected Converter

Abstract: This paper investigates how to train a recurrent neural network (RNN) using the Levenberg–Marquardt (LM) algorithm as well as how to implement optimal control of a grid-connected converter (GCC) using an RNN. To successfully and efficiently train an RNN using the LM algorithm, a new forward accumulation through time (FATT) algorithm is proposed to calculate the Jacobian matrix required by the LM algorithm. This paper explores how to incorporate FATT into the LM algorithm. The results show that the combination of the LM and FATT algorithms trains RNNs better than the conventional backpropagation through time algorithm. This paper presents an analytical study on the optimal control of GCCs, including theoretically ideal optimal and suboptimal controllers. To overcome the inapplicability of the optimal GCC controller under practical conditions, a new RNN controller with an improved input structure is proposed to approximate the ideal optimal controller. The performance of an ideal optimal controller and a well-trained RNN controller was compared in close to real-life power converter switching environments, demonstrating that the proposed RNN controller can achieve close to ideal optimal control performance even under low sampling rate conditions. The excellent performance of the proposed RNN controller under challenging and distorted system conditions further indicates the feasibility of using an RNN to approximate optimal control in practical applications.

On the Origin of Utility, Weighting, and Discounting Functions: How They Get Their Shapes and How to Change Their Shapes

Abstract: We present a theoretical account of the origin of the shapes of utility, probability weighting, and temporal discounting functions. In an experimental test of the theory, we systematically change the shape of revealed utility, weighting, and discounting functions by manipulating the distribution of monies, probabilities, and delays in the choices used to elicit them. The data demonstrate that there is no stable mapping between attribute values and their subjective equivalents. Expected and discounted utility theories, and also their descendants such as prospect theory and hyperbolic discounting theory, simply assert stable mappings to describe choice data and offer no account of the instability we find. We explain where the shape of the mapping comes from and, in describing the mechanism by which people choose, explain why the shape depends on the distribution of gains, losses, risks, and delays in the environment. Data, as supplemental material, are available at http://dx.doi.org/10.1287/mnsc.2013.1853 . This paper was accepted by Yuval Rottenstreich, judgment and decision making.

Umbilical vein testosterone in female infants born to mothers with polycystic ovary syndrome is elevated to male levels

Abstract: The aetiology of polycystic ovary syndrome (PCOS) is poorly understood, but an intrauterine hyperandrogenic environment has been implicated. This study was designed to assess whether the female offspring of mothers with PCOS are exposed to raised levels of testosterone (T) in utero. In this case-control study, three groups of pregnant women were recruited from the labour ward: PCOS women with a female baby (n = 10, PCOS girls); control women with a female baby (n = 20, control girls) and control women with a male baby (n = 10, control boys). Maternal and umbilical vein (UV) blood was assayed for T levels. UV T in PCOS girls was significantly raised, compared with control girls (p < 0.012). The difference in UV T between PCOS girls and control boys was not significant (p < 0.254). This is the first demonstration of a hyperandrogenic in utero environment in PCOS pregnancies; UV T in female infants is raised to male levels.

Conflict and Astroturfing in Niyamgiri: The Importance of National Advocacy Networks in Anti-Corporate Social Movements

Abstract: Traditional models of transnational advocacy networks (TANs) and stakeholder management do not capture the nuance and dynamics of (counter-)organizing processes around anti-corporate mobilization. Based on the case of a resistance movement against a planned bauxite mine on tribal land in India, we develop a process theory of interactions between local, national and international actors within transnational advocacy networks. These encounters are not always friendly and are often characterized by conflict between actors with disparate goals and interests. We highlight the importance of national advocacy networks (NANs) in anti-corporate social movements and describe the conflicts and disruptions that result from ignoring them. Our findings also point to the role of corporate counter-mobilization strategies in shaping resistance movements. Our narrative revolves around a particular focal actor in the anti-mining campaign: a young tribal man who emerged as a passionate spokesperson for the movement, but later became a supporter of the controversial mine. Our findings contribute to a richer understanding of the processes underlying transnational and national anti-corporate mobilization.