Approximation Algorithms for Route Planning with Nonlinear Objectives

We consider optimal route planning when the objective function is a general nonlinear and non-monotonic function. Such an objective models user behavior more accurately, for example, when a user is risk-averse, or the utility function needs to capture a penalty for early arrival. It is known that as nonlinearity arises, the problem becomes NP-hard and little is known about computing optimal solutions when in addition there is no monotonicity guarantee. We show that an approximately optimal non-simple path can be efficiently computed under some natural constraints. In particular, we provide a fully polynomial approximation scheme under hop constraints. Our approximation algorithm can extend to run in pseudo-polynomial time under a more general linear constraint that sometimes is useful. As a by-product, we show that our algorithm can be applied to the problem of finding a path that is most likely to be on time for a given deadline.Comment: 9 pages, 2 figures, main part of this paper is to be appear in AAAI'1

Autoencoders and Generative Adversarial Networks for Imbalanced Sequence Classification

Generative Adversarial Networks (GANs) have been used in many different applications to generate realistic synthetic data. We introduce a novel GAN with Autoencoder (GAN-AE) architecture to generate synthetic samples for variable length, multi-feature sequence datasets. In this model, we develop a GAN architecture with an additional autoencoder component, where recurrent neural networks (RNNs) are used for each component of the model in order to generate synthetic data to improve classification accuracy for a highly imbalanced medical device dataset. In addition to the medical device dataset, we also evaluate the GAN-AE performance on two additional datasets and demonstrate the application of GAN-AE to a sequence-to-sequence task where both synthetic sequence inputs and sequence outputs must be generated. To evaluate the quality of the synthetic data, we train encoder-decoder models both with and without the synthetic data and compare the classification model performance. We show that a model trained with GAN-AE generated synthetic data outperforms models trained with synthetic data generated both with standard oversampling techniques such as SMOTE and Autoencoders as well as with state of the art GAN-based models

Compliance and Imperfect Intertemporal Carbon Trading

This paper examines three compliance mechanisms of the Kyoto Protocol: (i) the restoration rate, (ii) the commitment period reserve rule, and (iii) the suspension mechanism, all potentially constraining greenhouse gas emissions trading across time and space. The joint effect of these mechanisms on prices and costs is studied in a twoperiod model under various assumptions about the competitiveness of the permit market and US participation. The analytical results indicate that the restoration rate can make discounted permit prices decrease over time. With the commitment period reserve, marginal costs may not only be lower, but also higher than the permit prices. The suspension rule will under quite general circumstances not affect prices and costs; only shift non-compliance from future sellers to future buyers. The numerical results suggest that with imperfect permit markets and non-participation of the US in the Kyoto Protocol in 2010, none of the three rules becomes binding.compliance; market power; emissions trading; Kyoto Protocol

Emergence and disappearance of micro-arcsecond structure in the scintillating quasar J1819+3845

The 4.8 GHz lightcurves of the scintillating intra-day variable quasar J1819+3845 during 2004-5 exhibit sharp structure, down to a time scale of 15 minutes, that was absent from lightcurves taken prior to this period and from the 2006 lightcurves. Analysis of the lightcurve power spectra show that the variations must be due to the emergence of new structure in the source. The power spectra yield a scattering screen distance of 3.8 +/- 0.3 pc for a best-fit v_ISS=59 +/- 0.5 km/s or 2.0 +/- 0.3 pc for the scintillation velocity reported by Dennett-Thorpe & de Bruyn (2003). The turbulence is required to be exceptionally turbulent, with C_N^2 > 0.7 Delta L_pc^{-1} m^{-20/3} for scattering material of thickness Delta L_{pc} pc along the ray path. The 2004 power spectrum can be explained in terms of a double source with a component separation 240 +/- 15 microas in 2004.Comment: MNRAS Lett (accepted), version with high-resolution figures at http://www.astro.caltech.edu/~jpm/MdB1819.pd

Tests of new instrument for measuring Dublin Descriptors

In the summer of 2007 a new instrument was developed which aimed at providingan operationalisation of the Dublin descriptors (Appendix 1). Special attention waspaid thereby to the so-called ‘anchor problem’ inherent in most self-assessments:the lack of an objective frame of reference against which different respondents canassess their own level of competence.The instrument consists of a combination of general and specific items. First of alla general item was formulated for each of the 5 Dublin descriptors. The generalitems were formulated in such a way as to match the original descriptors as closelyas possible. Anchors were developed for each of these items which correspond tojunior college, bachelors and masters levels. For example, for the item“communication” the junior college level was indicated by the anchor “is able totransmit information”, the bachelors level by "is able to communicate ideas andtransmit solutions” and the master level by “is able to communicate conclusionsand the knowledge, motivations and considerations that underlie these conclusionsin a convincing manner”. The anchors for the bachelors and masters level arederived more or less directly from the Dublin descriptors, and those for the juniorcollege level are based on the European Qualification Framework. For practicalreasons it was decided not to develop anchors for the PhD level. The anchors wereplaced in a scale ranging from 1 to 8, with the junior college level being assigned ascale value of 2, the bachelors level the value 5 and the masters level the value 7.This allowed respondents the option of choosing a level above masters level orbelow junior college level if they find that appropriate. The distances betweenjunior college, bachelors and masters level approximates the mean differences inyears of education corresponding to each level.labour market entry and occupational careers;

Leadership Development On The Go: A Multi-Perspective Two-Cohort Case Study To Explore Collective Leadership Development

There is a lack of studies focusing on how self-managed team experience across multiple tasks influence collective leadership capacities in an organisation. Responding to the long-standing calls to study collective leadership development (Raelin, 2006, 2018a; Day, 2011b; Yammarino et al., 2012; Day et al., 2014; Day and Liu, 2018; Eva et al., 2019) and to integrate shared leadership to the conceptualisation of leadership development (Klein and Ziegert, 2004; Klein et al., 2006; Bergman et al., 2012; Day and Liu, 2018; Raelin, 2018a), this thesis explores the potential of self-managed project team experience for enhancing leadership development as a collective capacity. The focus is shared leadership practices in self-managed project teams and the role of these practices for leadership learning and development across various tasks and time. The topic is relevant because collective leadership development has been understudied due to the predominant individualised focus in the existing leadership development studies (DeRue and Myers, 2014). Self-managed project teams engage in shared leadership to reach their objectives autonomously, and this engagement further enhances leadership capacities at multiple levels (Friedrich et al., 2009; Raelin, 2016b, 2018a). Due to the lack of prior studies, an overall understanding of the collective leadership development process and the outcomes was seen as an essential first step in contributing to the relevant literature. Thus, the study has a holistic approach and derives upon multiple theoretical perspectives (Eva et al., 2019). The study conceptualises collective leadership development through the lens of shared leadership. It draws on the concepts of complexity leadership, social network and social learning to explore the development process and outcomes holistically (Clarke, 2013; Eva et al., 2019). Therefore, the focus was on both dimensions of the leadership capacity development process: the acquisition of KSAs and the ability to engage in shared leadership behaviours. This kind of holistic approach requires multiple data sources and collection methods. The research was conducted as a case study with two cohorts embedded in a single organisational unit. The study has mainly utilised naturally occurring data from the practices in the unit across a series of (three) projects within eighteen (18) months to explore the phenomenon. Three primary data sources were post-project reviews (PPRs), participant surveys, and direct observation, with the first two being the main sources. Qualitative data concerning sense-making and learning were collected through document analysis of post-project review sessions, project documentations, open comments in the survey questionnaires, and observations. The behavioural data was collected through survey questionnaires where team members have rated each other’s shared leadership performances. The analysis is based on thematic analysis, time series analysis and constant comparison. The comparison of all data across time, methods and cohorts shows that self-managed team practice offers excellent opportunities for organisations to enhance collective (shared) leadership capacity. However, the impact of the experiences is more significant on creating awareness and acquiring knowledge, skills and attitudes (specifically social awareness and interpersonal skills) than on shared leadership behaviours. Analysis of the qualitative data identified seven broad themes: (1) openness to diversity and working with others, (2) communication and coordination, (3) self-awareness and confidence, (4) problem solving and decision making, (5) situational awareness and adaptability, (6) awareness and acceptance of different leadership styles, and (7) motivating others the learning outcomes resulting as collective capacity. Time series analysis of the shared leadership ratings shows a declining pattern. Integration of both types of analysis identified four challenging areas that need attention and additional coaching support for more effective development and performance. These areas were planning and scheduling, monitoring, providing critical feedback and team building The focus on the construction of meaning, learning and performance outcomes across multiple tasks and extended time is relevant for collective leadership development in multiple ways and thus, enriches the leadership development literature. First, the study contributes to the emerging collective leadership development literature by exploring the learning outcomes and performance outcomes across varying contexts in three projects rather than exploring them within the lifecycle of a single task in isolation from the contextual factors. Second, the multi-perspective conceptual model contributes to the much-demanded theorisation of collective leadership development. The study also contributes to practice by providing an overall picture of the capacity development process in self-managed project teams and identifying the bottlenecks in using self-managed teams for shared leadership development

The effect of service time variability on maximum queue lengths in M^X/G/1 queues

We study the impact of service-time distributions on the distribution of the maximum queue length during a busy period for the M^X/G/1 queue. The maximum queue length is an important random variable to understand when designing the buffer size for finite buffer (M/G/1/n) systems. We show the somewhat surprising result that for three variations of the preemptive LCFS discipline, the maximum queue length during a busy period is smaller when service times are more variable (in the convex sense).Comment: 12 page

A short-period Goodwin growth cycle

Growth Theory