Search results for "feature"
showing 10 items of 4091 documents
The Induced Smoothed lasso: A practical framework for hypothesis testing in high dimensional regression.
2020
This paper focuses on hypothesis testing in lasso regression, when one is interested in judging statistical significance for the regression coefficients in the regression equation involving a lot of covariates. To get reliable p-values, we propose a new lasso-type estimator relying on the idea of induced smoothing which allows to obtain appropriate covariance matrix and Wald statistic relatively easily. Some simulation experiments reveal that our approach exhibits good performance when contrasted with the recent inferential tools in the lasso framework. Two real data analyses are presented to illustrate the proposed framework in practice.
Structure Learning in Nested Effects Models
2007
Nested Effects Models (NEMs) are a class of graphical models introduced to analyze the results of gene perturbation screens. NEMs explore noisy subset relations between the high-dimensional outputs of phenotyping studies, e.g., the effects showing in gene expression profiles or as morphological features of the perturbed cell. In this paper we expand the statistical basis of NEMs in four directions. First, we derive a new formula for the likelihood function of a NEM, which generalizes previous results for binary data. Second, we prove model identifiability under mild assumptions. Third, we show that the new formulation of the likelihood allows efficiency in traversing model space. Fourth, we…
Optimal design of new steel connections
2019
The Limited Resistance Rigid Perfectly Plastic Hinge (LRPH) are special steel connections mainly usable to join beam elements of plane or spa-tial steel frames. The fundamental characteristics of these devices are the mutu-al independence of their own resistance and stiffness features as well as the re-spect of assigned constraints related to the elastic and limit behaviour of the joined elements. Within the frame structural scheme, the device plays the role of a rigid perfectly plastic hinge, constituted by a suitably sized sandwich sec-tion. The efficient use of the LRPH in the relevant frame depends on the appro-priate design of the device geometry. In the present paper, a new approach d…
Motor learning and body size within an insect brain computational model
2014
Nowadays modeling insect brains is also an important source of inspiration to develop learning architectures and control algorithms for applications on autonomous walking robots. Within the insect brain two important neuropiles received a lot of attention: the mushroom bodies (MBs) and the central complex (CX). Recent research activities considered the MBs as a unique architecture where different behavioural functions can be found. MBs are well known in bees and flies for their role in performing associative learning and memory in odor conditioning experiments [4]. They are also involved in the processing of multiple sensory modalities including visual tasks [3], different forms of learning…
Adaptive sparse representation of continuous input for tsetlin machines based on stochastic searching on the line
2021
This paper introduces a novel approach to representing continuous inputs in Tsetlin Machines (TMs). Instead of using one Tsetlin Automaton (TA) for every unique threshold found when Booleanizing continuous input, we employ two Stochastic Searching on the Line (SSL) automata to learn discriminative lower and upper bounds. The two resulting Boolean features are adapted to the rest of the clause by equipping each clause with its own team of SSLs, which update the bounds during the learning process. Two standard TAs finally decide whether to include the resulting features as part of the clause. In this way, only four automata altogether represent one continuous feature (instead of potentially h…
Spatio-Temporal Assessment of the European Hake (Merluccius merluccius) Recruits in the Northern Iberian Peninsula
2021
14 pages, 9 figures, 3 tables.-- This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY)
A paradigm of extreme rainfall pluvial floods in complex urban areas: the flood event of 15 July 2020 in Palermo (Italy)
2021
Abstract. In the last few years, some regions of the Mediterranean area have witnessed a progressive increase in extreme events, such as urban and flash floods, as a response to the increasingly frequent and severe extreme rainfall events, which are often exacerbated by the ever-growing urbanization. In such a context, the urban drainage systems may not be sufficient to convey the rainwater, thus increasing the risk deriving from the occurrence of such events. This study focuses on a particularly intense urban flood that occurred in Palermo (Italy) on 15 July 2020; it represents a typical pluvial flood due to extreme rainfall on a complex urban area that many cities have experienced in rece…
Forest drainage: a threat to benthic biodiversity of boreal headwater streams?
1998
1. Forest drainage, including mainly ditching of waterlogged peatlands in order to increase wood growth, has caused substantial changes in the hydrology and water quality of Finnish streams. However, knowledge on the ecological impact of these changes is poor. This paper studies the potential impact of forest drainage, catchment characteristics and habitat factors on the water quality and benthic macroinvertebrates in headwater streams of the River Isojoki, western Finland. An intensive programme of water sampling was carried out at nine study sites, while zoobenthic samples covered a total of 18 streams. 2. According to multivariate regression models concentrations of aluminium and suspend…
Changes in habitat structure, benthic invertebrate diversity, trout populations and ecosystem processes in restored forest streams: a boreal perspect…
2007
SUMMARY 1. Most Finnish streams were channelised during the 19th and 20th century to facilitate timber floating. By the late 1970s, extensive programmes were initiated to restore these degraded streams. The responses of fish populations to restoration have been little studied, however, and monitoring of other stream biota has been negligible. In this paper, we review results from a set of studies on the effects of stream restoration on habitat structure, brown trout populations, benthic macroinvertebrates and leaf retention. 2. In general, restoration greatly increased stream bed heterogeneity. The cover of mosses in channelised streams was close to that of unmodified reference sites, but a…
Stress generation at ridge axes by plate divergence and magma rise
1995
Abstract A model is explored for the rifting process particularly at the divergent plate boundary in Iceland, based on direct observations of the Krafla rifting episode 1975–1984. Magma accumulates near the axial crust-mantle transition as the plates diverge from each other and compression on the boundary decreases. Two-dimensional finite-element modelling is applied to investigate how divergence and buoyant rise of magma interact in triggering rifting. Both processes are found to be important, but long intervals between rifting episodes require the time-average deviatoric stress to be compressible normal to the axis.