Unsupervised 2D dimensionality reduction with adaptive structure learning

© 2017 Massachusetts Institute of Technology. In recent years, unsupervised two-dimensional (2D) dimensionality reduction methods for unlabeled large-scale data have made progress. However, performance of these degrades when the learning of similarity matrix is at the beginning of the dimensionality reduction process.Asimilarity matrix is used to reveal the underlying geometry structure of data in unsupervised dimensionality reduction methods. Because of noise data, it is difficult to learn the optimal similarity matrix. In this letter, we propose a new dimensionality reduction model for 2D image matrices: unsupervised 2D dimensionality reductionwith adaptive structure learning (DRASL). Instead of using a predetermined similarity matrix to characterize the underlying geometry structure of the original2Dimage space, our proposed approach involves the learning of a similarity matrix in the procedure of dimensionality reduction. To realize a desirable neighbors assignment after dimensionality reduction, we add a constraint to our model such that there are exact c connected components in the final subspace. To accomplish these goals, we propose a unified objective function to integrate dimensionality reduction, the learning of the similarity matrix, and the adaptive learning of neighbors assignment into it. An iterative optimization algorithm is proposed to solve the objective function. We compare the proposed method with several 2D unsupervised dimensionality methods. K-means is used to evaluate the clustering performance. We conduct extensive experiments on Coil20, ATandT, FERET, USPS, and Yale data sets to verify the effectiveness of our proposed method

Performance of high strength structural bolts in tension: effects of tolerance classes

Structural bolts have been manufactured for building construction for hundreds of years. In practice, failure of high strength structural bolts might be caused by their tolerance classes or coating procedures, which may weaken their internal or external threads. However, this research work is dedicated to understanding a bit more on bolt performance in tension, accounting for effects of tolerance classes in the applied numerical simulation for assessment of performance of structural bolts subjected to tensile loading. In addition, different constitutive relationships has also been taken into account in the numerical analysis in use of both implicit and explicit methods. The observed simulation results demonstrated two failure mechanisms for structural bolts, threads stripping and bolt shank failure, which has proved to be associated with their tolerance classes and coating procedures applied. As a result of this, carefully selecting bolts and nuts is a deliberate solution in preventing the premature failure (threads stripping) in bolted connections for performance-based steel construction

Spatial-temporal dynamics of China's terrestrial biodiversity: A dynamic habitat index diagnostic

Biodiversity in China is analyzed based on the components of the Dynamic Habitat Index (DHI). First, observed field survey based spatial patterns of species richness including threatened species are presented to test their linear relationship with remote sensing based DHI (2001-2010 MODIS). Areas with a high cumulative DHI component are associated with relatively high species richness, and threatened species richness increases in regions with frequently varying levels of the cumulative DHI component. The analysis of geographical and statistical distributions yields the following results on interdependence, polarization and change detection: (1) The decadal mean Cumulative Annual Productivity (DHI-cum 4) in Southeast China are in a stable (positive) relation to the Minimum Annual Apparent Cover (DHI-min) and is positively (negatively) related to the Seasonal Variation of Greenness (DHI-sea); (2) The decadal tendencies show bimodal frequency distributions aligned near DHI-min~0.05 and DHI-sea~0.5 which separated by zero slopes; that is, regions with both small DHI-min and DHI-sea are becoming smaller and vice versa; (3) The decadal tendencies identify regions of land-cover change (as revealed in previous research). That is, the relation of strong and significant tendencies of the three DHI components with climatic or anthropogenic induced changes provides useful information for conservation planning. These results suggest that the spatial-temporal dynamics of China's terrestrial species and threatened species richness needs to be monitored by first and second moments of remote sensing based information of the DHI. © 2016 by the authors

Pressure-induced double-dome superconductivity in kagome metal CsTi3Bi5

We present high-pressure resistance measurements up to 40 GPa on recently discovered titanium-based kagome metal CsTi$_3$Bi$_5$. At ambient pressure, CsTi$_3$Bi$_5$ shows no evidence of superconductivity in resistivity and specific heat. By applying pressure, superconductivity emerges and the superconducting transition temperature ${\it T}_{\rm c}$ reaches its first maximum of 1.2 K at $\sim$5 GPa. Then the ${\it T}_{\rm c}$ is suppressed by pressure and cannot be detected around 10 GPa, manifesting as a superconducting dome. Remarkably, upon further increasing pressure above $\sim$13 GPa, another superconducting dome shows up, with the maximum ${\it T}_{\rm c}$ of 0.6 K and ending pressure at $\sim$36 GPa. The variation of ${\it T}_{\rm c}$ displays a clear double-dome shape in the superconducting phase diagram. Our work demonstrates the similarity between CsTi$_3$Bi$_5$ and CsV$_3$Sb$_5$, providing valuable insights into the rich physics of these novel kagome metals.Comment: 7 pages, 5 figure

Change-Point Analysis of Precipitation and Drought Extremes in China over the Past 50 Years

Increases in climate extremes and their impacts have attracted global attention recently. In this study, the change-point years of precipitation extremes (PEs) and drought extremes (DEs) were investigated by Moving t-Test at 500 stations across the six regions in China. The detailed temporal change processes of them were demonstrated by the cumulative deviation method based on the data from nine typical stations. The results showed that: 1) DEs were more significantly and widely increased than PEs, the stations with increasing trends of PEs and DEs accounted for greater than 52.6% and 61.6% of the total, respectively; 2) increasing trends of DEs were mainly distributed in the east of Hu Huanyong Line. In this area, the increasing change-point years of DEs often occurred in the early 1980s in the south of the Yangzi River, while occurred in the 1990s in the north of the Yangzi River; 3) increasing trends of PEs were mainly distributed in Qing-Tibet Platen, Northwest China, and the southeastern area of Hu Huanyong Line. In these areas, the increasing change-point years of PEs often occurred around 1990 in the southeast of Hu Huanyong Line, while often occurred in the early 1980s in Qing-Tibet Platen. The results indicated that the area in the southeast of Hu Huanyong Line was under the threats of both PEs and DEs, this may produce severe impacts on agriculture, environment, water resources management, human society, etc.</jats:p

High inertness of W@Si-12 cluster toward O-2 molecule

The geometry, electronic structure, and reactivity with O2 molecules of an isolated W@Si12 cluster have been investigated by first principles simulations. The results confirm that O2 can weakly adsorb on the HP-W@Si12 cage with a binding energy of 0.004 to 0.027 eV. O2 may dissociate on the cluster by overcoming energy barrier of at least 0.593 eV. However, this is a spin-forbidden reaction, rendering the high inertness of the HP-W@Si12 cluster toward O2. These results confirm the high inertness of the W@Si12 cluster toward O2 molecules in ambient conditions, in close agreement with experimental observations of magic cluster of W@Si12

Trend and Change-Point Analysis of Streamflow and Sediment Discharge of the Gongshui River in China during the Last 60 Years

The Gongshui River basin exhibits one of the most serious soil erosion areas in southern China, and has always been the key control area of national soil and water conservation programs. This study used daily precipitation, streamflow, and sediment concentration data collected from 1957 to 2015 from the main hydrological stations of the Gongshui River to investigate streamflow and sediment discharge variations and their responses to precipitation and human activities. The Mann-Kendall and Pettitt’s test were used for trend and change-point detection. The double mass curve (DMC) method was employed to quantify the effects of precipitation change and human activities on hydrological regime shifts. The results showed insignificant trends of both annual precipitation and streamflow for all stations, while the sediment discharge of most stations exhibited significant decreasing trends. Change-point analyses revealed that all hydrologic stations except Mazhou had transition years. The estimation via DMC indicated that after the change point years, there was a rapid reduction in sediment discharge at Hanlinqiao, Fengkeng, Julongtan, Xiashan, and Chawu stations, but not at Mazhou, Ruijin, and Yangxinjian stations. Human activity provided a significantly greater contribution to sediment discharge than precipitation. The evidence clearly indicates that the degree and extension of conservation or destruction measures and the construction of large- and medium-sized reservoirs were the major factors significantly decreasing or increasing annual sediment discharge of the Gongshui River. This work could serve as the basis for decision making regarding river basin water resources management to estimate the effects of anthropogenic impacts on water and sediment discharge variations during the last few decades, thereby guiding adaptation and protection of the water resources of the Gongshui River flowing into the Poyang Lake.</jats:p

Shallow2Deep: Indoor scene modeling by single image understanding

Dense indoor scene modeling from 2D images has been bottlenecked due to the absence of depth information and cluttered occlusions. We present an automatic indoor scene modeling approach using deep features from neural networks. Given a single RGB image, our method simultaneously recovers semantic contents, 3D geometry and object relationship by reasoning indoor environment context. Particularly, we design a shallow-to-deep architecture on the basis of convolutional networks for semantic scene understanding and modeling. It involves multi-level convolutional networks to parse indoor semantics/geometry into non-relational and relational knowledge. Non-relational knowledge extracted from shallow-end networks (e.g. room layout, object geometry) is fed forward into deeper levels to parse relational semantics (e.g. support relationship). A Relation Network is proposed to infer the support relationship between objects. All the structured semantics and geometry above are assembled to guide a global optimization for 3D scene modeling. Qualitative and quantitative analysis demonstrates the feasibility of our method in understanding and modeling semantics-enriched indoor scenes by evaluating the performance of reconstruction accuracy, computation performance and scene complexity

Economic valuation of Earth’s critical zone: a pilot study of the Zhangxi catchment, China

This is the final version. Available from Mary Ann Liebert via the DOI in this record. Earth’s critical zone is the physical layer contained between the top of the vegetation canopy and the depth of the circulating groundwater below the land surface. The critical zone is defined within the study of Earth natural sciences as the unique terrestrial biophysical system that supplies most life-sustaining resources for humans. A feature of this specific physical system that is defined by geographical locale is the interactions of people with the vertically-connected biophysical flows and transformations (energy, material, biodiversity) that contribute to human welfare by delivering, both directly and indirectly, critical zone services to humankind. We have characterized these interactions by considering the full extent of the critical zone through the application of economic valuation methods. We estimated the current economic value of 14 critical zone services for 5 biophysical components of Earth’s critical zone, based on data collected from the Zhangxi catchment of Ningbo city located in the Yangtze River Delta region of China and from several additional published studies. For the full vertical extent of Earth’s critical zone bounded by the Zhangxi catchment, the value, most of which is outside the market, was estimated to be USD 116 million in 2018. Valuation of goods and services was delineated for benefits arising from key components of the critical zone physical system. The estimated value of the atmospheric component of Earth’s critical zone was USD 5 million; the vegetation component value was USD 96 million; the soil component value was USD 8 million; the surface water component value was USD 5 million; and the groundwater component value was USD 2 million. Because of the nature of the uncertainties and lack of data for the full range of identified services, these values are considered a minimum estimate. Gross domestic product in the Zhangxi catchment was around USD 431 million in 2018. These results illustrate, for one location, the range of services that arise when considering the full depth of Earth’s critical zone, the data needs for valuing this range of services, and the conceptual and potential methodological advances, and the challenges, that exist at the disciplinary interface between Earth natural sciences and applied economics.Natural Environment Research Counci

Measurement of the branching fractions of psi(2S) -> 3(pi+pi-) and J/psi -> 2(pi+pi-)

Using data samples collected at sqrt(s) = 3.686GeV and 3.650GeV by the BESII detector at the BEPC, the branching fraction of psi(2S) -> 3(pi+pi-) is measured to be [4.83 +- 0.38(stat) +- 0.69(syst)] x 10^-4, and the relative branching fraction of J/psi -> 2(pi+pi-) to that of J/psi -> mu+mu- is measured to be [5.86 +- 0.19(stat) +- 0.39(syst)]% via psi(2S) -> (pi+pi-)J/psi, J/psi -> 2(pi+pi-). The electromagnetic form factor of 3(pi+pi-) is determined to be 0.21 +- 0.02 and 0.20 +- 0.01 at sqrt(s) = 3.686GeV and 3.650GeV, respectively.Comment: 17pages, 7 figures, submitted to Phys. Rev.