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Sheng Yu

Publications and source records attributed to Sheng Yu.

At least 55 records · Page 3Linked to original sources

High-throughput relation extraction algorithm development associating knowledge articles and electronic health records

Objective: Medical relations are the core components of medical knowledge graphs that are needed for healthcare artificial intelligence. However, the requirement of expert annotation by conventional algorithm development processes creates a major bottleneck for mining new relations. In this paper, we present Hi-RES, a framework for high-throughput relation extraction algorithm development. We also show that combining knowledge articles with electronic health records (EHRs) significantly increases the classification accuracy. Methods: We use relation triplets obtained from structured databases and semistructured webpages to label sentences from target corpora as positive training samples. Two methods are also provided for creating improved negative samples by combining positive samples with naïve negative samples. We propose a common model that summarizes sentence information using large-scale pretrained language models and multi-instance attention, which then joins with the concept embeddings trained from the EHRs for relation prediction. Results: We apply the Hi-RES framework to develop classification algorithms for disorder-disorder relations and disorder-location relations. Millions of sentences are created as training data. Using pretrained language models and EHR-based embeddings individually provides considerable accuracy increases over those of previous models. Joining them together further tremendously increases the accuracy to 0.947 and 0.998 for the two sets of relations, respectively, which are 10-17 percentage points higher than those of previous models. Conclusion: Hi-RES is an efficient framework for achieving high-throughput and accurate relation extraction algorithm development.

cs.LG

Enhanced piezoelectricity and electronic band structure transition assisted by atomic shift in MoS2 monolayer

Piezoelectricity appears in the inversion asymmetric crystal that converts mechanical deformational force to electricity. Two-dimensional transition metal dichalcolgenide (TMDC) monolayers exhibit the piezoelectric effect due to the inversion asymmetry. The intrinsic piezoelectric coefficient (e11) of MoS2 is ~298 pC/m. For the single atomic shift of Mo of 20% along the armchair direction, the piezoelectric coefficient (e11) of MoS2 with 5x5 unit cells was enhanced up to 18%, and significantly modified the band structure. The single atomic shift in the MoS2 monolayer also induced new energy levels inside the forbidden bandgap. The defect-induced energy levels for a Mo atom shift along the armchair direction are relatively deeper than the energy levels for a S atom shift along the same direction. It indicates that the piezoelectricity and band structure of MoS2 can be engineered by a single atomic shift in the monolayer with multi unit cells for mechano-electrical applications.

physics.app-ph

First principle study on the transition of electronic, mechanic and piezoelectric property of hexagonal Boron Nitride nanotube

One-dimensional nanostructures such as nanowires and nanotubes are stimulating tremendous interest due to their structural, electronic and magnetic properties. In this study, the first principle calculation was performed to investigate on the size effect on the electronic, mechanic and piezoelectric properties of hexagonal-BN nanotube (BNNT). It demonstrates that the nanotube diameter can modulate the direct bandgap significantly of the zigzag-BNNT, increasing from 3.96eV to 4.44eV with the larger diameter from 10 to 16 unit cells in circular direction. Both armchair and zigzag BNNT exhibit large elastic modulus, implying promising applications in nanoscale surface engineering, tribology and nanomanufacturing/nanofabrication. Outstanding piezoelectricity is also observed with large piezoelectric coefficient of 0.084C/m2 for 10-zigazag-BNNT and 0.13 C/m2 for 16-zigzag-BNNT, exhibiting excellent potential in producing mechao-electric power generators.

physics.app-ph

Piezoelectric conversion in TMDCs Heterostructure Atomic Layers

Two-dimensional heterostructure of WSe2/MoS2 atomic layers has unique piezoelectric characteristics which depends on the number of atomic layer, stacking type, and interlayer interaction size. The van der Waals heterostructure of p- and n-type TMDC atomic layers with different work functions forms a staggered gap alignment. The large band offset of conduction band minimum and valence band maximum between p-type WSe2 and n-type MoS2 atomic layers leads to the large electric polarization and piezoelectricity. The output voltages for a MoS2/WSe2 partial vertical heterostructure with a size of 3.0 nm and 1.5 nm were 0.137 V and 0.183 V for 4% and 8% tensile strains, respectively. The output voltage of AB-stacking MoS2/WSe2 heterostructure was larger than that of AA-stacking heterostructure for 4% tensile strain due to the contribution of intrinsic piezoelectricity and the symmetric condition in out-of-plane. The AB-stacking has a lower formation energy and better structural stability compared to AA-stacking. The large output voltage of nanoscale partial or full vertical heterostructure of 2D WSe2/MoS2 atomic layers in addition to the increased output voltage through series connection of multiple nanoscale piezoelectric devices will enable the realization of nano electromechanical systems (NEMS) with TMDC heterostructure atomic layers.

cond-mat.mes-hall

Spin-resolved Visible Optical Spectra and Electronic Characteristics of Defect-mediated Hexagonal Boron Nitride Monolayer

The defect-mediated hexagonal boron nitride (hBN) supercell display the visible optical spectra and electronic characteristics. The defects in the hBN supercell include the atomic vacancy, antisite, antisite vacancy, and substitution of a foreign atom for boron or nitrogen. The hBN supercell with VB, CB, and NB-VN has the high electron density of states across the Fermi level which indicates the high conductive electronic characteristics. The hBN with defects including atomic vacancy, antisite vacancy, and substitution of a foreign atom for boron or nitride exhibit the distinct spin-resolved optical and electronics characteristics, while the defects of boron and nitrogen antisite do not display the spin-resolved optical characteristics. The hBN with positively charged defects has a dominant optical and electronic characteristics at the longer spectral region.

cond-mat.mtrl-sci

A Transition of Saturable and Reverse Saturable Absorption between Monolayer and Bilayer/Multilayer of TMDCs

The nonlinear absorption of two-dimensional molybdenum disulfide was analyzed using the Z-scan technique. Sample size corresponding to a number of layer determines the band gap in the materials which play the key role for nonlinearity. Exciton dipole transition from ground state to excited state for monolayer and bilayer/multilayer is determined by the excitation source, ESA and GSA values. If the band gap is wider than the excitation source, two-photon excitation process is dominant which requires the larger ESA than GSA. For narrower bandgap, one-photon excitation is favorable because of the larger GSA than ESA. In addition, defects, the temperature may alter the band gap. Therefore, the transition from RSA to SA and vice versa is determined by the number of layers in materials, temperature, and defects for a given excitation energy.

physics.optics

NILE: Fast Natural Language Processing for Electronic Health Records

Objective: Narrative text in Electronic health records (EHR) contain rich information for medical and data science studies. This paper introduces the design and performance of Narrative Information Linear Extraction (NILE), a natural language processing (NLP) package for EHR analysis that we share with the medical informatics community. Methods: NILE uses a modified prefix-tree search algorithm for named entity recognition, which can detect prefix and suffix sharing. The semantic analyses are implemented as rule-based finite state machines. Analyses include negation, location, modification, family history, and ignoring. Result: The processing speed of NILE is hundreds to thousands times faster than existing NLP software for medical text. The accuracy of presence analysis of NILE is on par with the best performing models on the 2010 i2b2/VA NLP challenge data. Conclusion: The speed, accuracy, and being able to operate via API make NILE a valuable addition to the NLP software for medical informatics and data science.

cs.CL

Generation of Synthetic Electronic Medical Record Text

Machine learning (ML) and Natural Language Processing (NLP) have achieved remarkable success in many fields and have brought new opportunities and high expectation in the analyses of medical data. The most common type of medical data is the massive free-text electronic medical records (EMR). It is widely regarded that mining such massive data can bring up important information for improving medical practices as well as for possible new discoveries on complex diseases. However, the free EMR texts are lacking consistent standards, rich of private information, and limited in availability. Also, as they are accumulated from everyday practices, it is often hard to have a balanced number of samples for the types of diseases under study. These problems hinder the development of ML and NLP methods for EMR data analysis. To tackle these problems, we developed a model to generate synthetic text of EMRs called Medical Text Generative Adversarial Network or mtGAN. It is based on the GAN framework and is trained by the REINFORCE algorithm. It takes disease features as inputs and generates synthetic texts as EMRs for the corresponding diseases. We evaluate the model from micro-level, macro-level and application-level on a Chinese EMR text dataset. The results show that the method has a good capacity to fit real data and can generate realistic and diverse EMR samples. This provides a novel way to avoid potential leakage of patient privacy while still supply sufficient well-controlled cohort data for developing downstream ML and NLP methods. It can also be used as a data augmentation method to assist studies based on real EMR data.

cs.CL

Word Segmentation as Graph Partition

We propose a new approach to the Chinese word segmentation problem that considers the sentence as an undirected graph, whose nodes are the characters. One can use various techniques to compute the edge weights that measure the connection strength between characters. Spectral graph partition algorithms are used to group the characters and achieve word segmentation. We follow the graph partition approach and design several unsupervised algorithms, and we show their inspiring segmentation results on two corpora: (1) electronic health records in Chinese, and (2) benchmark data from the Second International Chinese Word Segmentation Bakeoff.

cs.CL

Strain effect engineered in α-Al2O3/monolayer MoS2 interface by first principle calculations

With the advances in low dimensional transition metal dichalcolgenides (TMDCs) based metal oxide semiconductor field effect transistor (MOSFET), the interface between semiconductors and dielectrics has received considerable attention due to its dramatic effects on the morphology and charge transport of semiconductors. In this study, first principle calculations were utilized to investigate the strain effect induced by the interface between Al2O3 (0001) and monolayer MoS2. The results indicate that Al2O3 in 1.3nm thickness can apply the strain of 0.3% on MoS2 monolayer. The strain effect monotonically increases with the larger thickness of the dielectric layer. Also, the study on temperature effect indicates the monotonic lattice expansion induced by the higher temperature. Our study proposes that the dielectric engineering can be an effective tool for strain effect in the nanotechnology.

physics.comp-ph

Dirac Fermions induced in strained zigzag phosphorus nanotubes and the applications in field effect transistors

In this work, Dirac fermions have been obtained and engineered in one-dimensional (1D) zigzag phosphorus nanotubes (ZPNTs). We have performed a comprehensive first-principle computational study of the electronic properties of ZPNTs with various diameters. The results indicate that as the lattice parameter (Lc) along axial direction increases, ZPNTs undergo transitions from metal to semimetal and semimetal to semiconductor, whereas Dirac fermions appear at Lc ranging from 3.90Å to 4.10Å. In particular, a field effect transistor (FET) based on a 12-ZPNT (with 12 unit cells in transverse direction) exhibits semiconductor behaviors with efficient gate-effect modulation at Lc= 4.60Å. However, only weak gate modulation is demonstrated when the nanotube becomes semimetal at Lc= 4.10Å. This study indicates that ZPNTs are profoundly appealing in applications in the strain sensors. Our findings pave the way for development of high-performance strain-engineered electronics based on Dirac Fermions in 1D materials.

cond-mat.mes-hall

A Survey on Operational State Complexity

Descriptional complexity is the study of the conciseness of the various models representing formal languages. The state complexity of a regular language is the size, measured by the number of states of the smallest, either deterministic or nondeterministic, finite automaton that recognises it. Operational state complexity is the study of the state complexity of operations over languages. In this survey, we review the state complexities of individual regularity preserving language operations on regular and some subregular languages. Then we revisit the state complexities of the combination of individual operations. We also review methods of estimation and approximation of state complexity of more complex combined operations.

cs.FL

Computing Supply Function Equilibria via Spline Approximations

The supply function equilibrium (SFE) is a model for competition in markets where each firm offers a schedule of prices and quantities to face demand uncertainty, and has been successfully applied to wholesale electricity markets. However, characterizing the SFE is difficult, both analytically and numerically. In this paper, we first present a specialized algorithm for capacity constrained asymmetric duopoly markets with affine costs. We show that solving the first order conditions (a system of differential equations) using spline approximations is equivalent to solving a least squares problem, which makes the algorithm highly efficient. We also propose using splines as a way to improve a recently introduced general algorithm, so that the equilibrium can be found more easily and faster with less user intervention. We show asymptotic convergence of the approximations to the true equilibria for both algorithms, and illustrate their performance with numerical examples.

math.OC

An Empirical Study of How Users Adopt Famous Entities

Users of social networking services construct their personal social networks by creating asymmetric and symmetric social links. Users usually follow friends and selected famous entities that include celebrities and news agencies. In this paper, we investigate how users follow famous entities. We statically and dynamically analyze data within a huge social networking service with a manually classified set of famous entities. The results show that the in-degree of famous entities does not fit to power-law distribution. Conversely, the maximum number of famous followees in one category for each user shows power-law property. To our best knowledge, there is no research work on this topic with human-chosen famous entity dataset in real life. These findings might be helpful in microblogging marketing and user classification.

cs.SI

A Survey of Prediction Using Social Media

Social media comprises interactive applications and platforms for creating, sharing and exchange of user-generated contents. The past ten years have brought huge growth in social media, especially online social networking services, and it is changing our ways to organize and communicate. It aggregates opinions and feelings of diverse groups of people at low cost. Mining the attributes and contents of social media gives us an opportunity to discover social structure characteristics, analyze action patterns qualitatively and quantitatively, and sometimes the ability to predict future human related events. In this paper, we firstly discuss the realms which can be predicted with current social media, then overview available predictors and techniques of prediction, and finally discuss challenges and possible future directions.

cs.SI

Introducing the Adaptive Convex Enveloping

Convexity, though extremely important in mathematical programming, has not drawn enough attention in the field of dynamic programming. This paper gives conditions for verifying convexity of the cost-to-go functions, and introduces an accurate, fast and reliable algorithm for solving convex dynamic programs with multivariate continuous states and actions, called Adaptive Convex Enveloping. This is a short introduction of the core technique created and used in my dissertation, so it is less formal, and misses some parts, such as literature review and reference, compared to a full journal paper.

math.OC

Transition Complexity of Incomplete DFAs

In this paper, we consider the transition complexity of regular languages based on the incomplete deterministic finite automata. A number of results on Boolean operations have been obtained. It is shown that the transition complexity results for union and complementation are very different from the state complexity results for the same operations. However, for intersection, the transition complexity result is similar to that of state complexity.

cs.FL

State Complexity of Catenation Combined with Star and Reversal

This paper is a continuation of our research work on state complexity of combined operations. Motivated by applications, we study the state complexities of two particular combined operations: catenation combined with star and catenation combined with reversal. We show that the state complexities of both of these combined operations are considerably less than the compositions of the state complexities of their individual participating operations.

cs.FL