Sparse Linear Identifiable Multivariate Modeling

In this paper we consider sparse and identifiable linear latent variable (factor) and linear Bayesian network models for parsimonious analysis of multivariate data. We propose a computationally efficient method for joint parameter and model inference, and model comparison. It consists of a fully Bayesian hierarchy for sparse models using slab and spike priors (two-component delta-function and continuous mixtures), non-Gaussian latent factors and a stochastic search over the ordering of the variables. The framework, which we call SLIM (Sparse Linear Identifiable Multivariate modeling), is validated and bench-marked on artificial and real biological data sets. SLIM is closest in spirit to LiNGAM (Shimizu et al., 2006), but differs substantially in inference, Bayesian network structure learning and model comparison. Experimentally, SLIM performs equally well or better than LiNGAM with comparable computational complexity. We attribute this mainly to the stochastic search strategy used, and to parsimony (sparsity and identifiability), which is an explicit part of the model. We propose two extensions to the basic i.i.d. linear framework: non-linear dependence on observed variables, called SNIM (Sparse Non-linear Identifiable Multivariate modeling) and allowing for correlations between latent variables, called CSLIM (Correlated SLIM), for the temporal and/or spatial data. The source code and scripts are available from http://cogsys.imm.dtu.dk/slim/.Comment: 45 pages, 17 figure

Pitching for PIDs: European support for a sustainable PID infrastructure - Avoiding a PIDfall

The TechLib libraries (DTU Copenhagen, ETH Zurich, TIB Hannover and TU Delft) would like to start a community discussion around European support for sustainable PID infrastructures. Please take the time to read our pitch. We would very much appreciate your thoughts and ideas

Analysis Of Tourism Preferences In Choosing Online-Base Travel Agents In Indonesia

The high demand for tourism is one of the triggers for the mushrooming of e-commerce based on travel. The high competition of online-based travel agents requires each provider to improve its features and services. Based on this background, it is important to further research the preferences of tourists in choosing a travel agent. The study involved 112 samples (Time Linear Period), by comparing 3 providers namely Traveloka.com, Tiket.com and Pegipegi.com. Analytic Hierarchy Process (AHP) is used as a data analysis tool, while the valuation aspect is related to product completeness, price, promos, service quality. The results showed that Traveloka is the most preferred provider by tourists; this is because Traveloka offers many promos, and services that are considered quite fast compared to other providers. Index Terms: E-commerce, Analytic Hierarchy Process (AHP), travel, Indonesia, online-based travel agents, e-business, touris

Development and evaluation of a method to estimate the potential of decarbonisation technologies deployment at higher education campuses

peer-reviewedThis paper describes a method for the quantitative estimation of the potential of decarbonisation technologies deployed on Higher Education Campuses (HEC). This was developed to fill the need for a practicable and standardised method to provide preliminary estimations of the deployment potential of building integrated photovoltaics (PV), micro-wind turbines, rainwater harvesting and ground mounted PV at HECs. The method identifies two key variables, namely roof area and open carpark area, to aid estimation of decarbonisation technologies deployment at HECs, using Google Earth imagery coupled with publicly available online HEC maps. The method was trialled for the higher education sector in Ireland identifying major potential for deployment of decarbonisation technologies for the sector. The building decarbonisation aspect of the proposed approach is applicable to sectors outside HEC particularly commercial and industrial sectors due to similarity in building footprint characteristics. The open carpark component of the methodology is also applicable to city-scale analysis due to uniformity in form of open carparks worldwide. This highlights the usefulness of this method through informing city-scale transitions towards decarbonisatio

NuSTAR discovery of a cyclotron line in KS 1947+300

We present a spectral analysis of three simultaneous Nuclear Spectroscopy Telescope Array and Swift/XRT observations of the transient Be-neutron star binary KS 1947+300 taken during its outburst in 2013/2014. These broadband observations were supported by Swift/XRT monitoring snapshots every three days, which we use to study the evolution of the spectrum over the outburst. We find strong changes of the power-law photon index, which shows a weak trend of softening with increasing X-ray flux. The neutron star shows very strong pulsations with a period of P ≈ 18.8 s. The 0.8–79 keV broadband spectrum can be described by a power law with an exponential cutoff and a blackbody component at low energies. During the second observation we detect a cyclotron resonant scattering feature at 12.5 keV, which is absent in the phase-averaged spectra of observations 1 and 3. Pulse phase-resolved spectroscopy reveals that the strength of the feature changes strongly with pulse phase and is most prominent during the broad minimum of the pulse profile. At the same phases the line also becomes visible in the first and third observation at the same energy. This discovery implies that KS 1947+300 has a magnetic field strength of B ≈ 1.1 × 10^(12) (1 + z) G, which is at the lower end of known cyclotron line sources

The effects of wind-induced inclination on the dynamics of semi-submersible floating wind turbines in the time domain

This study focusses on the coupling effects arising from the changes in the hydrodynamic behaviour of a semi-submersible floating wind turbine when it undergoes large inclinations under wind loading. By means of a range of time-domain simulations, it is shown that both the hull geometric nonlinearity effect and the alteration of viscous hydrodynamic forces can significantly affect the dynamics of a typical floating wind turbine operating in waves at rated conditions. The consequences of said effects for both aligned and misaligned wind and waves are explored. In general terms inclinations are found to increase motions, where the modes that are more affected depend on the relative direction between incident wind and waves. Understanding the sources of aero-hydrodynamic coupling is key to providing sound design and modelling guidelines for the coming generation of floating wind turbines