Safe Screening With Variational Inequalities and Its Application to LASSO

Sparse learning techniques have been routinely used for feature selection as the resulting model usually has a small number of non-zero entries. Safe screening, which eliminates the features that are guaranteed to have zero coefficients for a certain value of the regularization parameter, is a technique for improving the computational efficiency. Safe screening is gaining increasing attention since 1) solving sparse learning formulations usually has a high computational cost especially when the number of features is large and 2) one needs to try several regularization parameters to select a suitable model. In this paper, we propose an approach called "Sasvi" (Safe screening with variational inequalities). Sasvi makes use of the variational inequality that provides the sufficient and necessary optimality condition for the dual problem. Several existing approaches for Lasso screening can be casted as relaxed versions of the proposed Sasvi, thus Sasvi provides a stronger safe screening rule. We further study the monotone properties of Sasvi for Lasso, based on which a sure removal regularization parameter can be identified for each feature. Experimental results on both synthetic and real data sets are reported to demonstrate the effectiveness of the proposed Sasvi for Lasso screening.Comment: Accepted by International Conference on Machine Learning 201

HKC: An Algorithm to Predict Protein Complexes in Protein-Protein Interaction Networks

With the availability of more and more genome-scale protein-protein interaction (PPI) networks, research interests gradually shift to Systematic Analysis on these large data sets. A key topic is to predict protein complexes in PPI networks by identifying clusters that are densely connected within themselves but sparsely connected with the rest of the network. In this paper, we present a new topology-based algorithm, HKC, to detect protein complexes in genome-scale PPI networks. HKC mainly uses the concepts of highest k-core and cohesion to predict protein complexes by identifying overlapping clusters. The experiments on two data sets and two benchmarks show that our algorithm has relatively high F-measure and exhibits better performance compared with some other methods

Atomically phase-matched second-harmonic generation in a 2D crystal.

Second-harmonic generation (SHG) has found extensive applications from hand-held laser pointers to spectroscopic and microscopic techniques. Recently, some cleavable van der Waals (vdW) crystals have shown SHG arising from a single atomic layer, where the SH light elucidated important information such as the grain boundaries and electronic structure in these ultra-thin materials. However, despite the inversion asymmetry of the single layer, the typical crystal stacking restores inversion symmetry for even numbers of layers leading to an oscillatory SH response, drastically reducing the applicability of vdW crystals such as molybdenum disulfide (MoS2). Here, we probe the SHG generated from the noncentrosymmetric 3R crystal phase of MoS2. We experimentally observed quadratic dependence of second-harmonic intensity on layer number as a result of atomically phase-matched nonlinear dipoles in layers of the 3R crystal that constructively interfere. By studying the layer evolution of the A and B excitonic transitions in 3R-MoS2 using SHG spectroscopy, we also found distinct electronic structure differences arising from the crystal structure and the dramatic effect of symmetry and layer stacking on the nonlinear properties of these atomic crystals. The constructive nature of the SHG in this 2D crystal provides a platform to reliably develop atomically flat and controllably thin nonlinear media

Ocena postrzeganych zagrożeń środowiskowych dla życia mieszkańców w perspektywie środowiskowej opinii publicznej w Chinach

Population health, social development and the environment are important elements of sustainable development. This article uses the China People's Daily message board to collect environmental public opinion data, visualizes the public opinion hotspots of environmental based on word frequency statistics, and applies the Latent Dirichlet Allocations (LDA) topic model to analyze the spatial distribution of environmental risk perception dimensions. The conclusions are as follows: (1) in terms of the hotspots of environmental public opinion, the most frequent occurrences are the living environment, interest demands and noise pollution. (2) There is heterogeneity in the topic of environmental risk perception. The perception of pollution source types has the highest weight in environmental risk perception in the eastern, central, and western regions. Specifically, the types of pollution sources in the eastern that receive the most attention are garbage and noise pollution. In addition to paying attention to noise pollution, the central and western also have a higher perceived weight on the polluters. Residents in northeast are most concerned about changes in residents' health and living environment quality. (3) From the perspective of environmental risk perception, health perception has the highest proportion in northeast, followed by the eastern, and finally the central and western. Proportion of perception of interest demands is highest in the central region, perception of residential environment quality is highest in the northeast region, perception of pollution source types is highest in the eastern, central, and western regions, and lowest in the northeast region. Finally, some practical and feasible policy recommendations were proposed for different regions.Zdrowie ludności, rozwój społeczny i środowisko są ważnymi elementami zrównoważonego rozwoju. W tym artykule wykorzystano tablicę ogłoszeń China People's Daily do gromadzenia danych dotyczących opinii publicznej na temat środowiska, wizualizowano najważniejsze punkty opinii publicznej na temat środowiska w oparciu o statystyki częstotliwości słów i zastosowano model Latent Dirichlet Allocations (LDA) do analizy przestrzennego rozkładu wymiarów postrzegania ryzyka środowiskowego. Wnioski są następujące: (1) jeśli chodzi o najbardziej aktywne punkty opinii publicznej w zakresie ochrony środowiska, najczęstszymi zjawiskami są środowisko życia, wymagania dotyczące zainteresowań i zanieczyszczenie hałasem. (2) Istnieje różnorodność w temacie postrzegania ryzyka środowiskowego. Postrzeganie rodzajów źródeł zanieczyszczeń ma największe znaczenie w postrzeganiu ryzyka środowiskowego w regionach wschodnich, centralnych i zachodnich. W szczególności źródłami zanieczyszczeń we wschodniej części kraju, którym poświęca się najwięcej uwagi, są śmieci i hałas. Oprócz zwracania uwagi na zanieczyszczenie hałasem, regiony środkowe i zachodnie również przywiązują większą wagę do sprawców zanieczyszczeń. Mieszkańcy północno-wschodniej części kraju najbardziej niepokoją zmiany w ich zdrowiu i jakości środowiska życia. (3) Z punktu widzenia postrzegania ryzyka dla środowiska, postrzeganie zdrowia ma najwyższy odsetek na północnym wschodzie, następnie na wschodzie, a na końcu w środkowej i zachodniej części. Proporcja postrzegania potrzeb odsetkowych jest najwyższa w regionie centralnym, postrzeganie jakości środowiska mieszkalnego jest najwyższe w regionie północno-wschodnim, postrzeganie rodzajów źródeł zanieczyszczeń jest najwyższe w regionach wschodnich, centralnych i zachodnich, a najniższe w regionie północno-wschodnim. Na koniec zaproponowano kilka praktycznych i wykonalnych zaleceń politycznych dla różnych regionów