Neural-symbolic learning for knowledge base completion

A query answering task computes the prediction scores of ground queries inferred from a Knowledge Base (KB). Traditional symbolic-based methods solve this task using ‘exact’ provers. However, they are not very scalable and difficult to apply to current large KBs. Sub-symbolic methods have recently been proposed to address this problem. They require to be trained to learn the semantics of the symbolic representation and use it to make predictions about query answering. Such predictions may rely upon unknown rules over the given KB. Not all proposed sub-symbolic systems are capable of inducing rules from the KB; and even more challenging is the learning of rules that are human interpretable. Some approaches, e.g., those based on a Neural Theorem Prover (NTP), are able to address this problem but with limited scalability and expressivity of the rules that they can induce. We take inspiration from the NTP framework and propose three sub-symbolic architectures that solve the query answering task in a scalable manner while supporting the induction of more expressive rules. Two of these architectures, called Topical NTP (TNTP) and Topic-Subdomain NTP (TSNTP), address the scalability aspect. Trained representations of predicates and constants are clustered and the soft-unification of the backward chaining proof procedure that they use is controlled by these clusters. The third architecture, called Negation-as-Failure TSNTP (NAF TSNTP), addresses the expressivity of the induced rules by supporting the learning of rules with negation-as-failure. All these architectures make use of additional hyperparameters that encourage the learning of induced rules during training. Each architecture is evaluated over benchmark datasets with increased complexity in size of the KB, number of predicates and constants present in the KB, and level of incompleteness of the KB with respect to test sets. The evaluation measures the accuracy of query answering prediction and computational time. The former uses two key metrics, AUC_PR and HITS, adopted also by existing sub-symbolic systems that solve the same task, whereas the computational time is in terms of CPU training time. The evaluation performance of our systems is compared against that of existing state-of-the-art sub-symbolic systems, showing that our approaches are indeed in most cases more accurate in solving query answering tasks, whilst being more efficient in computational time. The increased accuracy in some tasks is specifically due to the learning of more expressive rules, thus demonstrating the importance of increased expressivity in rule induction.Open Acces

Identifying Indicators and Timescales of Agricultural Drought in the Northeast United States using Crop Area-weighted Drought Indices

Critical indices of agricultural drought in the Northeast United States (Northeast) are examined with a particular focus on the drought events in 2016 and 2020. We evaluate relationships of drought indices that are based on precipitation (PRCP), soil moisture (SM), and evaporative demand (E0) and their optimal timescales to agricultural-impacts data. We resampled forty years (1981-2020) of these daily climate drivers onto crop-cover maps provided by the National Agricultural Statistics Service (NASS) and computed standardized drought indices, namely the Standardized Precipitation Index (SPI), the Standardized Soil Moisture Index (SSMI), and the Evaporative Demand Drought Index (EDDI). Further indices that reflect actual evapotranspiration (ET) and the balance between PRCP and E0 — the Landscape Evaporative Response Index (LERI) and the Standardized Precipitation-Evapotranspiration Index (SPEI), respectively--were also included. Indices were estimated at timescales ranging from one week to twelve months. All climate drivers were averaged to state and county levels before their use in estimating the drought indices. Five of the most widely cultivated crops in the Northeast were selected--the most prominent being hay and pasture. Forty years (1981-2020) of annual hay yield and twenty-six years (1995-2020) of weekly pasture-condition records were retrieved from NASS. Hay yields were detrended and correlated to each set of drought indices, while pasture conditions were compared to the progression of indices within the drought years of 2016 and 2020. Results show the strongest correlation (Rmax) around 0.5-0.7 between drought indices and hay yield, with SPI correlations being positive and EDDI correlations negative. The Rmax values and associated distribution of dates and timescales were derived for states and counties and exhibited distinct regional spatial variation. Hay yield showed the strongest response to shorter timescales for SSMI and EDDI than for SPI and SPEI. Weekly pasture conditions in most states exhibited a strong response to the 2016 and 2020 droughts. Characteristics of how the degradation of pasture through the growing season tracks the progression of drought indices across different states were examined. Respectively, pasture conditions show the strongest response to 1- to 2-week SSMI, 2-week to 1-month EDDI, and 1- to 3-month SPI. At the 1-week timescale, fluctuations of LERI generally tracked fluctuations of SSMI throughout both 2016 and 2020. The times when major pastureland degradations began were usually accompanied by abnormally low LERI, low SSMI, and high EDDI, regardless of SPI

Scientists' bounded mobility on the epistemic landscape

Despite persistent efforts in revealing the temporal patterns in scientific careers, little attention has been paid to the spatial patterns of scientific activities in the knowledge space. Here, drawing on millions of papers in six disciplines, we consider scientists' publication sequence as "walks" on the quantifiable epistemic landscape constructed from large-scale bibliometric corpora by combining embedding and manifold learning algorithms, aiming to reveal the individual research topic dynamics and association between research radius with academic performance, along their careers. Intuitively, the visualization shows the localized and bounded nature of mobile trajectories. We further find that the distributions of scientists' transition radius and transition pace are both left-skewed compared with the results of controlled experiments. Then, we observe the mixed exploration and exploitation pattern and the corresponding strategic trade-off in the research transition, where scientists both deepen their previous research with frequency bias and explore new research with knowledge proximity bias. We further develop a bounded exploration-exploitation (BEE) model to reproduce the observed patterns. Moreover, the association between scientists' research radius and academic performance shows that extensive exploration will not lead to a sustained increase in academic output but a decrease in impact. In addition, we also note that disruptive findings are more derived from an extensive transition, whereas there is a saturation in this association. Our study contributes to the comprehension of the mobility patterns of scientists in the knowledge space, thereby providing significant implications for the development of scientific policy-making.Comment: article paper, 47 pages, 29 figures, 4 table

La representación de la cortesía en la serie de televisión Sueño en el Pabellón Rojo (Wang Fulin, 1987)

La tesis doctoral —titulada La representación de la cortesía en la serie de televisión Sueño en el Pabellón Rojo (Wang Fulin, 1987)— responde el deseo de dar a conocer la cortesía en la cultura tradicional china estudiando una serie de televisión que adapta una novela clásica china del siglo XVIII. Tomamos la serie de televisión Sueño en el Pabellón Rojo de 1987 como objeto de estudio. Investigamos la producción de esta serie y la televisión china bajo el contexto social y cultural de la década de 1980 y estudiamos las teorías sobre la cortesía y sus distintas representaciones en esta serie de televisión, teniendo como referencia la sociedad feudal china del siglo XVIII. Analizamos la cortesía representada en los 36 episodios de la serie de televisión Sueño en el Pabellón Rojo para identificar las representaciones generales de la cortesía en el siglo XVIII de la antigua China. Tenemos en cuenta la novela Sueño en el Pabellón Rojo de Cao Xueqin, los estudios de la Rojología, la trayectoria del director Wang Fulin, el grupo de producción de la serie de televisión, entre otros..

Three dimensional photonic Dirac points in metamaterials

Topological semimetals, representing a new topological phase that lacks a full bandgap in bulk states and exhibiting nontrivial topological orders, recently have been extended to photonic systems, predominantly in photonic crystals and to a lesser extent, metamaterials. Photonic crystal realizations of Dirac degeneracies are protected by various space symmetries, where Bloch modes span the spin and orbital subspaces. Here, we theoretically show that Dirac points can also be realized in effective media through the intrinsic degrees of freedom in electromagnetism under electromagnetic duality. A pair of spin polarized Fermi arc like surface states is observed at the interface between air and the Dirac metamaterials. These surface states show linear k-space dispersion relation, resulting in nearly diffraction-less propagation. Furthermore, eigen reflection fields show the decomposition from a Dirac point to two Weyl points. We also find the topological correlation between a Dirac point and vortex/vector beams in classic photonics. The theoretical proposal of photonic Dirac point lays foundation for unveiling the connection between intrinsic physics and global topology in electromagnetism.Comment: 15 pages, 5 figure

Flowmeter for large-scale pipes

AbstractThis paper studied a new type of flowmeter, the bypass flowmeter. It is suitable for large-scale pipes. The principle of bypass flowmeter is studied by analyzing flowing in parallel pipes and carrying out experiments at a modified performance test system for centrifugal pumps. The study results showed that the flowrate ratio between the main pipe and the bypass pipe is determined by the geometric structures of pipes and the flowing states in the pipes. The flowrate ratio varies greatly when the Reynolds numbers are relatively lower both in the main pipe and the bypass pipe. The flowrate ratio keeps constant when the Reynolds number in the main pipe is larger than 120000. The head loss becomes smaller when the bypass pipe is connected to the main pipe. The percentage of head loss decrease is from 7.64% to 9.34%. The results indicate that bypass flowmeter is suitable for flowrate measuring in large scale pipes. It will not cause additional head loss to the flow