Bayesian Nonparametric Multilevel Clustering with Group-Level Contexts

We present a Bayesian nonparametric framework for multilevel clustering which utilizes group-level context information to simultaneously discover low-dimensional structures of the group contents and partitions groups into clusters. Using the Dirichlet process as the building block, our model constructs a product base-measure with a nested structure to accommodate content and context observations at multiple levels. The proposed model possesses properties that link the nested Dirichlet processes (nDP) and the Dirichlet process mixture models (DPM) in an interesting way: integrating out all contents results in the DPM over contexts, whereas integrating out group-specific contexts results in the nDP mixture over content variables. We provide a Polya-urn view of the model and an efficient collapsed Gibbs inference procedure. Extensive experiments on real-world datasets demonstrate the advantage of utilizing context information via our model in both text and image domains.Comment: Full version of ICML 201

Realizing a complex of unstable modules

6 pagesIn a preceding article the authors and Tran Ngoc Nam constructed a minimal injective resolution of the mod 2 cohomology of a Thom spectrum. A Segal conjecture type theorem for this spectrum was proved. In this paper one shows that the above mentioned resolutions can be realized topologically. In fact there exists a family of cofibrations inducing short exact sequences in mod 2 cohomology. The resolutions above are obtained by splicing together these short exact sequences. Thus the injective resolutions are realizable in the best possible sense. In fact our construction appears to be in some sense an injective closure of one of Takayasu. It strongly suggests that one can construct geometrically (not only homotopically) certain dual Brown-Gitler spectra. Content

Failure of Embankment on Soil-Cement Columns for Thi Vai Port, Vietnam

The Thi Vai Container Port is constructed on reclaimed ground along the Thi Vai River in the Mekong delta approximately 90 km southeast of Ho Chi Minh City, Vietnam. The soil profile consists of an about 15 to 23 m thick deposit of soft, normally consolidated, highly compressible clay deposited on dense to compact sand. A soil improvement scheme was instigated aiming to reduce long-term settlement after construction of the facilities and improve the stability of the river bank. The scheme combined wick drains and, along the river bank, soil cement columns and toe revetments. The wick drains were installed at a spacing of about 1.5 m and a staged surcharge was placed to a maximum height of 6 through 6.6 m to bring about the consolidation of the clay. After a surcharge height of 4.7 m had been in place for about three months and the measured settlement was about 1.2 m, a slope failure occurred along about 200 m length of the riverbank. An investigation indicated that the three-month consolidation period had not increased clay undrained shear strength as anticipated and that the slope failure had broken the soil cement columns at about 11 m depth below the original ground surface. Costs to remedy the collapsed and damaged area amounted to about US$10 million. The paper presents the background information, soil failure details, results of bank stability analyses, and the solution chosen for the remedial construction

Analysis of Piled-Raft Foundation for CAI MEP Container Port, Vietnam

During the last decade, a series of ports are being built along the Thi Vai River in the Mekong delta approximately 80 km southeast of Ho Chi Minh City, Vietnam. The ports are built on reclaimed ground over an about 30 to 40 m thick deposit of soft, normally consolidated, compressible clay deposited on dense to compact sand The deep foundation system typically used for buildings in this region consists of pretensioned spun high strength concrete piles driven to significant toe bearing in dense soils. Because of the anticipated significant costs of this solution, a more economical alternative foundation system was essential, and the alternative of a shaft bearing pile, a precast concrete pile, was proposed for Cai Mep Container Port. To reduce settlements, a soil improvement scheme was imposed, consisting of wick drains installed through the clay to the sand and placing an up to 8 m thick surcharge over the area. After removal of the surcharge, piled-raft foundations were constructed for the Port building, incorporating 400 mm square, precast concrete piles, which were driven to depths of 18 m. Settlement monitoring showed that the area and the piles continued to settle after the removal of the surcharge, indicating that consolidation settlement had not been completed despite the about 18 months long surcharge period. It became clear that the long-term settlements, primarily due to downdrag, would exceed the limit of maximum 400 mm over a 20-year period. In order to remedy the situation, the piles were lengthened to a total length of 44 m to ensure that the neutral plane was located in the sand, where no long-term settlement would occur. The problem and its solution were analyzed by means of the Unified Design Method. The remedial solution added about US$2 million to the project and caused a 12-month delay

Fermi arc reconstruction in synthetic photonic lattice

The chiral surface states of Weyl semimetals have an open Fermi surface called Fermi arc. At the interface between two Weyl semimetals, these Fermi arcs are predicted to hybridize and alter their connectivity. In this letter, we numerically study a one-dimensional (1D) dielectric trilayer grating where the relative displacements between adjacent layers play the role of two synthetic momenta. The lattice emulates 3D crystals without time-reversal symmetry, including Weyl semimetal, nodal line semimetal, and Chern insulator. Besides showing the phase transition between Weyl semimetal and Chern insulator at telecom wavelength, this system allows us to observe the Fermi arc reconstruction between two Weyl semimetals, confirming the theoretical predictions.Comment: Main text: 4 pages, 4 figures. Supplemental materials: 19 pages, 18 figure

La fonction de partition de Minc et une conjecture de Segal pour certains spectres de Thom

On construit dans cet article une résolution injective minimale dans la catégorie \U des modules instables sur l'algèbre de Steenrod modulo $2$, de la cohomologie de certains spectres obtenus à partir de l'espace de Thom du fibré, associé à la représentation régulière réduite du groupe abélien élémentaire $(\Z/2)^n$, au dessus de l'espace $B(\Z/2)^n$. Les termes de la résolution sont des produits tensoriels de modules de Brown-Gitler $J(k)$ et de modules de Steinberg $L_n$ introduits par S. Mitchell et S. Priddy. Ces modules sont injectifs d'après J. Lannes et S. Zarati, de plus ils sont indécomposables. L'existence de cette résolution avait été conjecturée par Jean Lannes et le deuxième auteur. La principale indication soutenant cette conjecture était un résultat combinatoire de G. Andrews : la somme alternée des séries de Poincaré des modules considérées est nulle

Magic configurations in Moir\'e Superlattice of Bilayer Photonic crystal: Almost-Perfect Flatbands and Unconventional Localization

We investigate the physics of photonic band structures of the moir\'e patterns that emerged when overlapping two uni-dimensional (1D) photonic crystal slabs with mismatched periods. The band structure of our system is a result of the interplay between intra-layer and inter-layer coupling mechanisms, which can be fine-tuned via the distance separating the two layers. We derive an effective Hamiltonian that captures the essential physics of the system and reproduces all numerical simulations of electromagnetic solutions with high accuracy. Most interestingly, \textit{magic distances} corresponding to the emergence of photonic flatbands within the whole Brillouin zone of the moir\'e superlattice are observed. We demonstrate that these flatband modes are tightly localized within a moir\'e period. Moreover, we suggest a single-band tight-binding model that describes the moir\'e minibands, of which the tunnelling rate can be continuously tuned via the inter-layer strength. Our results show that the band structure of bilayer photonic moir\'e can be engineered in the same fashion as the electronic/excitonic counterparts. It would pave the way to study many-body physics at photonic moir\'e flatbands and novel optoelectronic devices.Comment: 6 pages + Supplement. Comments are welcome

Does hotter temperature increase poverty and inequality? Global evidence from subnational data analysis

Despite a vast literature documenting the harmful effects of climate change on various socioeconomic outcomes, little evidence exists on the global impacts of hotter temperature on poverty and inequality. Analysis of a new global panel dataset of subnational poverty in 134 countries finds that a one-degree Celsius increase in temperature leads to a 9.1 percent increase in poverty, using the US$1.90 daily poverty threshold. A similar increase in temperature causes a 1.4 percent increase in the Gini inequality index. The paper also finds negative effects of colder temperature on poverty and inequality. Yet, while poorer countries—particularly those in South Asia and Sub-Saharan Africa—are more affected by climate change, household adaptation could have mitigated some adverse effects in the long run. The findings provide relevant and timely inputs for the global fight against climate change as well as the current policy debate on the responsibilities of richer countries versus poorer countries