Open Access. Powered by Scholars. Published by Universities.®
Physical Sciences and Mathematics Commons™
Open Access. Powered by Scholars. Published by Universities.®
- Discipline
-
- Computer Sciences (2526)
- Engineering (1889)
- Environmental Sciences (1883)
- Chemistry (1869)
- Physics (1823)
-
- Life Sciences (1613)
- Earth Sciences (1537)
- Mathematics (1376)
- Social and Behavioral Sciences (1164)
- Oceanography and Atmospheric Sciences and Meteorology (722)
- Statistics and Probability (696)
- Medicine and Health Sciences (691)
- Education (645)
- Electrical and Computer Engineering (557)
- Astrophysics and Astronomy (526)
- Geology (482)
- Computer Engineering (460)
- Arts and Humanities (446)
- Databases and Information Systems (410)
- Applied Mathematics (400)
- Business (399)
- Natural Resources Management and Policy (367)
- Natural Resources and Conservation (357)
- Water Resource Management (347)
- Environmental Monitoring (343)
- Sustainability (292)
- Hydrology (272)
- Public Affairs, Public Policy and Public Administration (259)
- Optics (246)
- Institution
-
- Selected Works (1771)
- University of Nebraska - Lincoln (590)
- TÜBİTAK (419)
- Singapore Management University (359)
- University of Kentucky (337)
-
- Old Dominion University (282)
- University of Dayton (238)
- University of South Florida (206)
- Utah State University (196)
- City University of New York (CUNY) (189)
- Missouri University of Science and Technology (189)
- Portland State University (187)
- University of Wollongong (172)
- Louisiana State University (171)
- University of Texas at El Paso (163)
- Western University (154)
- William & Mary (154)
- Florida International University (146)
- Nova Southeastern University (141)
- Purdue University (134)
- University of Tennessee, Knoxville (131)
- Embry-Riddle Aeronautical University (128)
- SelectedWorks (128)
- Georgia Southern University (125)
- Brigham Young University (121)
- University of Arkansas, Fayetteville (114)
- Wayne State University (112)
- San Jose State University (110)
- Parkland College (109)
- Western Kentucky University (106)
- Keyword
-
- Stander Symposium project (151)
- Climate change (103)
- Mathematics (95)
- Course Syllabus (94)
- Chemistry (73)
-
- Sustainability (65)
- Chemical Engineering (51)
- GIS (50)
- Sea level rise (50)
- Physics (49)
- Carbon (47)
- Science (47)
- Graphene (46)
- Pure sciences (41)
- Applied sciences (40)
- Modeling (40)
- Computer Science (39)
- Statistics (38)
- Galaxies (37)
- Nanoparticles (37)
- Data (36)
- Earth sciences (36)
- Georgia Southern University (36)
- Security (36)
- Conservation (34)
- Management (33)
- Water quality (33)
- Biology (32)
- CCRM GIS Data (32)
- Geology (32)
- Publication
-
- Research Collection School Of Computing and Information Systems (345)
- Theses and Dissertations (329)
- Electronic Theses and Dissertations (214)
- John R Rice (175)
- Turkish Journal of Electrical Engineering and Computer Sciences (166)
-
- Australian Institute for Innovative Materials - Papers (160)
- Stander Symposium Projects (151)
- Physics and Astronomy Faculty Publications (128)
- Electronic Thesis and Dissertation Repository (119)
- Faculty Publications (115)
- USF Tampa Graduate Theses and Dissertations (115)
- Doctoral Dissertations (113)
- Turkish Journal of Chemistry (106)
- Honors Theses (101)
- Masters Theses (101)
- Physics Faculty Publications (93)
- Graduate Theses and Dissertations (92)
- Publications and Research (91)
- Open Access Theses & Dissertations (85)
- Turkish Journal of Mathematics (83)
- Donald P. Umstadter (81)
- Richard C. Holz (81)
- Departmental Technical Reports (CS) (78)
- Journal of Electrochemistry (78)
- Chemistry Faculty Publications (75)
- Walden Dissertations and Doctoral Studies (74)
- The Synapse: Intercollegiate science magazine (72)
- Open Access Dissertations (70)
- Dissertations (69)
- Publications (69)
- Publication Type
Articles 1471 - 1500 of 12617
Full-Text Articles in Physical Sciences and Mathematics
Collision Induced Superfluorescence, A. Kumarakrishnan, Siddharaj Chudasama, Xianming Han
Collision Induced Superfluorescence, A. Kumarakrishnan, Siddharaj Chudasama, Xianming Han
Xianming Han
We have studied superfluorescence (SF) in Ca vapor evolving on the 3d4s3DJ-4s4p3PJ−1 transitions at 1.9 mm by exciting the 4s21S0-4s4p1P1 with a pulsed dye laser. SF is generated following population transfer by spinchanging collisions with an inert gas Ar from the 4s4p1P1 and 3d4s1D2 levels. We show for the first time to our knowledge that the time delay for SF evolution follows the 1/ÎN dependence expected for the case of uniform excitation of the vapor column by collisional transfer. Here, N is the number of participating atoms that was measured directly from the photon yield. The measured photon yield for …
Superfluorescence Polarization: Signature Of Collisional Redistribution, A. Kumarakrishnan, S. Chudasama, Xianming Han
Superfluorescence Polarization: Signature Of Collisional Redistribution, A. Kumarakrishnan, S. Chudasama, Xianming Han
Xianming Han
We have studied effects of magnetic sublevel degeneracy on the polarization of superfluorescent pulses generated on the Ca 4s4p1P1–3d4s1D2 transition at 5.5μm. These pulses were generated from a cell of length 50 cm by optically pumping calcium vapor on the 4s21S0–4s4p1P1 transition in the presence of Ar gas. The axis of ellipticity of superfluorescence (SF) polarization is oriented parallel to the axis of the pump-laser polarization at large detunings, and undergoes an abrupt rotation through 90° for detunings close to resonance. The distribution of populations in the magnetic sublevels of the 1P1 state can be estimated using a simple model …
Diamond Growth Reactor Chemistry And Film Nucleation Enhancement Using Chlorinated Hydrocarbons, James Chenault, Charles Feigerle, Xianming Han, Robert Shaw
Diamond Growth Reactor Chemistry And Film Nucleation Enhancement Using Chlorinated Hydrocarbons, James Chenault, Charles Feigerle, Xianming Han, Robert Shaw
Xianming Han
The chemistry of diamond film growth from chlorinated hydrocarbons has been investigated using a hot filament reactor coupled to an orifice sampling mass spectrometer. The relative concentrations of the species present near the growth surface have been determined as a function of filament temperature for dilute mixtures of CH4, CH3Cl, CH2Cl2 and CHCl3 in H2. Mass spectral analysis indicated that chlorinated hydrocarbons are sequentially dechlorinated in the presence of hydrogen at moderate reactor temperatures. A dark film was deposited on all surfaces of the reactor during studies of this dechlorination of CHCl3. Raman analysis indicated that these deposits are small …
Fine‐Structure Mixing Within The Zn(43pj) Multiplet By Collisions With The Noble Gases, Xianming Han, J. F. Kelly
Fine‐Structure Mixing Within The Zn(43pj) Multiplet By Collisions With The Noble Gases, Xianming Han, J. F. Kelly
Xianming Han
Measurements of rate coefficients for intramultiplet state transfer of Zn(4 3 P 1→4 3 P J’) by collisions with the rare gases are presented. The state‐to‐state binary rate coefficients are derived from least‐squares fittings of the time‐resolved triexponential behavior of the 4 3 P 1fluorescence. These rate coefficients were studied systematically over a temperature range of 690–1100 K in order to characterize the velocity dependence of the collisional coupling. The systematic behavior of the rate coefficients with varying temperature and noble gas species is qualitatively consistent with a nearly adiabatic coupling limit for noncrossing levels.
Collisional Dynamics Of The First Excited States Of Neon In The 590-670 Nm Region Using Laser Optogalvanic Spectroscopy, Xianming Han, M. Su, C. Haridass, P. Misra
Collisional Dynamics Of The First Excited States Of Neon In The 590-670 Nm Region Using Laser Optogalvanic Spectroscopy, Xianming Han, M. Su, C. Haridass, P. Misra
Xianming Han
A mathematical rate equation model, incorporating the various processes contributing to the generation of optogalvanic signals in a discharge plasma, has been used to analyze the time-resolved waveforms of neon in the wavelength region 590–670 nm. Amplitudes, decay rates and the appropriate instrumental time constant have been determined using a non-linear least-squares fit of the observed time-resolved optogalvanic waveforms.
The First Multi-Color Photometric Study Of The Short-Period Contact Eclipsing Binary Gk Aqr, Liyun Zhang, Qingfeng Pi, Xianming Han, Tongan Li, Xiliang Zhang, Hongyan Sang, Daimei Wang, Shuai Wang
The First Multi-Color Photometric Study Of The Short-Period Contact Eclipsing Binary Gk Aqr, Liyun Zhang, Qingfeng Pi, Xianming Han, Tongan Li, Xiliang Zhang, Hongyan Sang, Daimei Wang, Shuai Wang
Xianming Han
We made the first VRI CCD light curves of the short-period contact eclipsing binary GK Aqr, which was observed on October 5 and 8, 2013 at Xinglong station of National Astronomical Observatories, China. The ephemeris of GK Aqr was calculated based on our two newly obtained minima and the minima that other observers obtained previously. We discovered that the orbital period of GK Aqr exhibits an increasing trend of Ṗ=2.8(0.1)×10^-7 days/year by means of fitting the O-C values of the minima. This phenomenon might be explained by mass transfer from the primary (less massive) component to the secondary (more massive) …
Four Color Observations Of 2501 Lohja, Bin Li, Haibin Zhao, Hao Lu, Xianming Han
Four Color Observations Of 2501 Lohja, Bin Li, Haibin Zhao, Hao Lu, Xianming Han
Xianming Han
Photometric studies of asteroid 2501 Lohja were made between 2014 June 24 and 25 using the Southeastern Association for Research in Astronomy (SARA) Kitt Peak telescope with Bessell B, V, R and I filters. We obtained a synodic period of 3.81 ± 0.01h, which is consistent with previous values.
Spin-Exchange Cross Section For Electron Excitation Of Na 3s 3p Determined By A Novel Spectroscopic Technique, Xianming Han, G. W. Schwinn, A. Gallagher
Spin-Exchange Cross Section For Electron Excitation Of Na 3s 3p Determined By A Novel Spectroscopic Technique, Xianming Han, G. W. Schwinn, A. Gallagher
Xianming Han
An experimental technique is described which enables determination of the partial cross sections for electron excitation of atoms as a function of changes in spin and orbital angular momentum. This method provides a good signal-to-noise ratio in the energy region near threshold, and could be used to study long- or short-lived excited states of many atomic systems. Measurements for Na 3S−3P, near-threshold excitation are reported here. The results are generally in good agreement with the close-coupling calculations of D. L. Moores and D. W. Norcross [J. Phys. B 5, 1482 (1972)] for the largest ΔmS and ΔmL components of the …
8077 Hoyle: A Short Period Asteroid, Daniel A. Klinglesmith Iii, Ethan Risley, Janek Turk, Angelica Vargas, Xianming Han, Orry R. Heffner, Adam W. Kidd, Bradley J. Magnetta, Frederick W. Rastede
8077 Hoyle: A Short Period Asteroid, Daniel A. Klinglesmith Iii, Ethan Risley, Janek Turk, Angelica Vargas, Xianming Han, Orry R. Heffner, Adam W. Kidd, Bradley J. Magnetta, Frederick W. Rastede
Xianming Han
The main-belt asteroid 8077 Hoyle was observed on 13 nights over a span of 47 days in 2012 April-May. A bimodal synodic period of 2.7454 ± 0.0002 h and an amplitude of 0.20 ± 0.02 mag. were obtained.
Period Determination For Nea (162421) 2000 Et70, Eduardo Manuel Alvarez, Julian Oey, Xianming Han, Orry R. Heffner, Adam W. Kidd, Bradley J. Magnetta, Frederick W. Rastede
Period Determination For Nea (162421) 2000 Et70, Eduardo Manuel Alvarez, Julian Oey, Xianming Han, Orry R. Heffner, Adam W. Kidd, Bradley J. Magnetta, Frederick W. Rastede
Xianming Han
Lightcurve analysis for (162421) 2000 ET70 was performed in collaboration with observers in Uruguay, Australia, and the United States from observations obtained during the asteroid’s favorable opposition in 2012. The synodic rotation period was found to be 8.947 ± 0.001 h and the lightcurve amplitude was 0.60 ± 0.07 mag.
Photometric Observation Of 3024 Hainan, 3920 Aubignan, And 5951 Alicemonet, Bin Li, Haibin Zhao, Xianming Han, Wenjuan Liu, Luming Sun, Jingjing Shi, Shan Gao, Hongyan Zhou
Photometric Observation Of 3024 Hainan, 3920 Aubignan, And 5951 Alicemonet, Bin Li, Haibin Zhao, Xianming Han, Wenjuan Liu, Luming Sun, Jingjing Shi, Shan Gao, Hongyan Zhou
Xianming Han
Three minor planets were measured photometrically between 2012 September 4 and 21 using the SARA (Southeastern Association for Research in Astronomy) South telescope, located in Cerro Tololo Inter-American Observatory. The following synodic periods were found: 3024 Hainan, P = 11.785 ± 0.005 h; 3920 Aubignan, P = 4.4762 ± 0.0005 h; and 5951 Alicemonet, P = 3.8871 ± 0.0005 h.
Monte Carlo Least-Squares Fitting Of Experimental Signal Waveforms, Xianming Han, Vladimir Pozdina, C. Haridas, Prabhakar Misra
Monte Carlo Least-Squares Fitting Of Experimental Signal Waveforms, Xianming Han, Vladimir Pozdina, C. Haridas, Prabhakar Misra
Xianming Han
This paper focuses on why the regular least{squares ¯tting technique is unstable when used to ¯t exponential functions to signal waveforms, since such functions are highly correlated. It talks about alternative approaches, such as the search method, which has a slow convergence rate of 1=N1=M, for M parameters, where N is the number of computations performed. We have used the Monte Carlo method, utilizing both search and random walk, to devise a stable least{squares ¯tting algorithm that converges rapidly at a rate 1=N1=2, regardless of the number of parameters used in ¯tting the waveforms. The Monte Carlo approach has been …
Superfluorescence From Optically Trapped Calcium Atoms, Xianming Han
Superfluorescence From Optically Trapped Calcium Atoms, Xianming Han
Xianming Han
We have studied superfluorescence (SF) under highly unfavorable conditions of rapid collisional and radiative distribution in a Doppler-broadened medium. Nanosecond SF pulses at 5.5 μm were generated on the Ca 4s4p1P1–3d4s1D2 transition from a column of calcium vapor buffered with Ar by optically pumping the 4s21S0–4s4p1P1 transition. The Rabi frequency associated with the intense pump pulse prevents the occurrence of SF while the pump laser is on. As a result, the predicted scaling laws that describe the properties of SF in a transversely excited system, such as peak heights, pulse widths, and delay times, are shown to apply in our …
Abrupt Change In Neon Discharge Plasma Detected Through Optogalvanic Effects, Xianming Han, Michael Blosser, Prabhakar Misra, Haridass Chandran
Abrupt Change In Neon Discharge Plasma Detected Through Optogalvanic Effects, Xianming Han, Michael Blosser, Prabhakar Misra, Haridass Chandran
Xianming Han
When a laser is tuned between two excited energy levels of a gas in a Direct Current discharge lamp, the discharge current will experience a temporary disturbance lasting tens or hundreds of microseconds known as the optogalvanic effect. We have carried out extensive studies of optogalvanic effects in neon discharge plasmas for transitions at 621.7 nm, 630.5 nm, 638.3 nm, 650.7 nm and 659.9 nm. A nonlinear least-squares Monte Carlo technique has been used to determine the relevant amplitude coefficients, decay rates and the instrumental time constant. We discovered an abrupt change in the neon discharge plasma at a discharge …
Collisional Ionization Of Excited State Neon In A Gas Discharge Plasma, Xianming Han, Verl Wiseheart, Scott Conner, Meng-Chih Su, David Monts
Collisional Ionization Of Excited State Neon In A Gas Discharge Plasma, Xianming Han, Verl Wiseheart, Scott Conner, Meng-Chih Su, David Monts
Xianming Han
We report the first case where it is possible to clearly identify and quantitatively characterize the dominant physical processes contributing to production of the optogalvanic effect (OGE) signal in a discharge plasma. This work concentrates on the simplest case where only two states are involved in the optical transition. The theoretical model with only four parameters is in excellent agreement with the experimentally obtained time-resolved OGE waveforms. The collisional ionization rate in the upper state is twice as fast as that in the lower state although the two states are only separated by 1.94 eV. We conclude that the optogalvanic …
Lightcurve Analysis Of Four Asteroids, Bin Li, Haibin Zhao, Xianming Han, Lina Annable, Eli Finkel, Orry Heffner, Adam Kidd, Bradley Magnetta, Tiffany Ramires, Frederick Rastede, Sean Sproston
Lightcurve Analysis Of Four Asteroids, Bin Li, Haibin Zhao, Xianming Han, Lina Annable, Eli Finkel, Orry Heffner, Adam Kidd, Bradley Magnetta, Tiffany Ramires, Frederick Rastede, Sean Sproston
Xianming Han
From June 2011 through May 2012 May, photometric data for four asteroids were obtained using the Southeastern Association for Research in Astronomy (SARA) telescope located at the Kitt Peak National Observatory. The following synodic periods were found: 4808 Ballaero, P = 8.8976 ± 0.0007 h; 7750 McEwen, P = 27.82 ± 0.01 h; 11941 Archinal, P = 2.717 ±0.006 h; and (47035) 1998WS, P = 7.996 ± 0.001 h.
Investigations Of Superfluorescent Cascades, A. Kumarakrishnan, Xianming Han
Investigations Of Superfluorescent Cascades, A. Kumarakrishnan, Xianming Han
Xianming Han
We report our studies of superfluorescent cascades in atomic calcium which result from two-photon excitation of several levels reasonably close to the ionization limit. We have observed significant conversion efficiencies for some of these transitions which result in subnanosecond pulses particularly in the visible wavelengths. We report the discovery of a novel two-photon scattering mechanism which could prove to be a useful method for determining collisional broadening rates. In addition, a hyper Raman transition near 17 μm is discovered which appears to be a promising candidate for a tunable source.
Production And Diagnosis Of A Highly Spin-Polarized Na Beam, G. Schinn, Xianming Han, A. Gallagher
Production And Diagnosis Of A Highly Spin-Polarized Na Beam, G. Schinn, Xianming Han, A. Gallagher
Xianming Han
We describe optically pumping a beam of sodium atoms to >96% mS and >92% mS, mI state selection. (We have accurately measured the population of every mS, mI state in the optically pumped beam.) For the optical pumping both ground hyperfine states are pumped, using single-mode cw dye-laser radiation tuned to the 3S1/2–3P1/2 transition that is phase modulated in a LiTaO3 crystal to produce first-order sidebands at approximately the 1772-MHz hyperfine splitting of the ground state. The z-directed optical pumping is performed in a z-directed magnetic field of ~5 G. The state-selected atoms then move, in ~1 cm, into an …
Rotation Periods Of 1660 Wood, 7173 Sepkoski, 12738 Satoshimiki, And (23233) 2000 Wm72, Xianming Han, Bin Li, Haibin Zhao
Rotation Periods Of 1660 Wood, 7173 Sepkoski, 12738 Satoshimiki, And (23233) 2000 Wm72, Xianming Han, Bin Li, Haibin Zhao
Xianming Han
We present rotation periods of four asteroids: 1660 Wood, 7173 Sepkoski, 12738 Satoshimiki, and (23233) 2000 WM72. The observations were undertaken using the SARA (Southeastern Association for Research in Astronomy) South telescope, located in Cerro Tololo Inter-American Observatory in Chile, from 2011 December to 2012 April. The following synodic periods were found: 1660 Wood, P = 6.8088 ± 0.0002 h; 7173 Sepkoski, P = 2.44 ± 0.02 h; 12738 Satoshimiki, P = 8.708 ± 0.001 h; and (23233) 2000 WM72, P = 3.732 ± 0.003 h.
Photometric Observations Of 782 Montefiore, 3842 Harlansmith, 5542 Moffatt, 6720 Gifu, And (19979) 1989 Vj, Xianming Han, Bin Li, Haibin Zhao, Wenjuan Liu, Luming Sun, Jingjing Shi, Shan Gao, Shufen Wang, Xiang Pan, Peng Jiang, Hongyan Zhou
Photometric Observations Of 782 Montefiore, 3842 Harlansmith, 5542 Moffatt, 6720 Gifu, And (19979) 1989 Vj, Xianming Han, Bin Li, Haibin Zhao, Wenjuan Liu, Luming Sun, Jingjing Shi, Shan Gao, Shufen Wang, Xiang Pan, Peng Jiang, Hongyan Zhou
Xianming Han
Five solar system minor planets were measured photometrically between 2012 October and December using the SARA (Southeastern Association for Research in Astronomy) telescopes located in Kitt Peak National Observatory in USA and Cerro Tololo Inter-American Observatory in Chile. The following synodic periods were found: 782 Montefiore P = 4.0728 ± 0.0006 h; 3842 Harlansmith, P = 2.7938 ± 0.0005 h; 5542 Moffatt P = 5.187 ± 0.001 h; 6720 Gifu, P = 4.231 ± 0.001 h; and (19979) 1989 VJ, P = 7.568 ± 0.005 h.
Mixed Methods Research Designs, Kevin P. Gosselin Phd
Mixed Methods Research Designs, Kevin P. Gosselin Phd
Research Day
No abstract provided.
Flexible Gating Of Contextual Influences In Natural Vision, Odelia Schwartz
Flexible Gating Of Contextual Influences In Natural Vision, Odelia Schwartz
Mathematics Colloquium Series
An appealing hypothesis suggests that neurons represent inputs in a coordinate system that is matched to the statistical structure of images in the natural environment. I discuss theoretical work on unsupervised learning of statistical regularities in natural images. In the model, Bayesian inference amounts to a generalized form of divisive normalization, a canonical computation that has been implicated in many neural areas. In our framework, divisive normalization is flexible: it is recruited only when the image is inferred to contain dependencies, and muted otherwise. I particularly focus on recent work in which we have applied this approach to understanding spatial …
Can You Summarize This? Identifying Correlates Of Input Difficulty For Generic Multi-Document Summarization, Ani Nenkova, Annie Louis
Can You Summarize This? Identifying Correlates Of Input Difficulty For Generic Multi-Document Summarization, Ani Nenkova, Annie Louis
Ani Nenkova
Different summarization requirements could make the writing of a good summarymore difficult, or easier. Summary length and the characteristics of the input are such constraints influencing the quality of a potential summary. In this paper we report the results of a quantitative analysis on data from large-scale evaluations of multi-document summarization, empirically confirming this hypothesis. We further show that features measuring the cohesiveness of the input are highly correlated with eventual summary quality and that it is possible to use these as features to predict the difficulty of new, unseen, summarization inputs.
Discourse Indicators For Content Selection In Summaization, Annie Louis, Aravind K. Joshi, Ani Nenkova
Discourse Indicators For Content Selection In Summaization, Annie Louis, Aravind K. Joshi, Ani Nenkova
Ani Nenkova
We present analyses aimed at eliciting which specific aspects of discourse provide the strongest indication for text importance. In the context of content selection for single document summarization of news, we examine the benefits of both the graph structure of text provided by discourse relations and the semantic sense of these relations. We find that structure information is the most robust indicator of importance. Semantic sense only provides constraints on content selection but is not indicative of important content by itself. However, sense features complement structure information and lead to improved performance. Further, both types of discourse information prove complementary …
Automatic Sense Prediction For Implicit Discourse Relations In Text, Emily Pitler, Annie Louis, Ani Nenkova
Automatic Sense Prediction For Implicit Discourse Relations In Text, Emily Pitler, Annie Louis, Ani Nenkova
Ani Nenkova
We present a series of experiments on automatically identifying the sense of implicit discourse relations, i.e. relations that are not marked with a discourse connective such as “but” or “because”. We work with a corpus of implicit relations present in newspaper text and report results on a test set that is representative of the naturally occurring distribution of senses. We use several linguistically informed features, including polarity tags, Levin verb classes, length of verb phrases, modality, context, and lexical features. In addition, we revisit past approaches using lexical pairs from unannotated text as features, explain some of their shortcomings and …
Automatic Evaluation Of Linguistic Quality In Multi-Document Summarization, Emily Pitler, Annie Louis, Ani Nenkova
Automatic Evaluation Of Linguistic Quality In Multi-Document Summarization, Emily Pitler, Annie Louis, Ani Nenkova
Ani Nenkova
To date, few attempts have been made to develop and validate methods for automatic evaluation of linguistic quality in text summarization. We present the first systematic assessment of several diverse classes of metrics designed to capture various aspects of well-written text. We train and test linguistic quality models on consecutive years of NIST evaluation data in order to show the generality of results. For grammaticality, the best results come from a set of syntactic features. Focus, coherence and referential clarity are best evaluated by a class of features measuring local coherence on the basis of cosine similarity between sentences, coreference …
Structural Features For Predicting The Linguistic Quality Of Text: Applications To Machine Translation, Automatic Summarization And Human-Authored Text, Ani Nenkova, Jieun Chae, Annie Louis, Emily Pitler
Structural Features For Predicting The Linguistic Quality Of Text: Applications To Machine Translation, Automatic Summarization And Human-Authored Text, Ani Nenkova, Jieun Chae, Annie Louis, Emily Pitler
Ani Nenkova
Sentence structure is considered to be an important component of the overall linguistic quality of text. Yet few empirical studies have sought to characterize how and to what extent structural features determine fluency and linguistic quality. We report the results of experiments on the predictive power of syntactic phrasing statistics and other structural features for these aspects of text. Manual assessments of sentence fluency for machine translation evaluation and text quality for summarization evaluation are used as gold-standard. We find that many structural features related to phrase length are weakly but significantly correlated with fluency and classifiers based on the …
Measuring Importance And Query Relevance In Toopic-Focused Multi-Document Summarization, Surabhi Gupta, Ani Nenkova, Dan Jurafsky
Measuring Importance And Query Relevance In Toopic-Focused Multi-Document Summarization, Surabhi Gupta, Ani Nenkova, Dan Jurafsky
Ani Nenkova
The increasing complexity of summarization systems makes it difficult to analyze exactly which modules make a difference in performance. We carried out a principled comparison between the two most commonly used schemes for assigning importance to words in the context of query focused multi-document summarization: raw frequency (word probability) and log-likelihood ratio. We demonstrate that the advantages of log-likelihood ratio come from its known distributional properties which allow for the identification of a set of words that in its entirety defines the aboutness of the input. We also find that LLR is more suitable for query-focused summarization since, unlike raw …
Using Entity Features To Classify Implicit Discourse Relations, Annie Louis, Aravind K. Joshi, Rashmi Prasad, Ani Nenkova
Using Entity Features To Classify Implicit Discourse Relations, Annie Louis, Aravind K. Joshi, Rashmi Prasad, Ani Nenkova
Ani Nenkova
We report results on predicting the sense of implicit discourse relations between adjacent sentences in text. Our investigation concentrates on the association between discourse relations and properties of the referring expressions that appear in the related sentences. The properties of interest include coreference information, grammatical role, information status and syntactic form of referring expressions. Predicting the sense of implicit discourse relations based on these features is considerably better than a random baseline and several of the most discriminative features conform with linguistic intuitions. However, these features do not perform as well as lexical features traditionally used for sense prediction.
Creating Local Coherence: An Empirical Assessment, Annie Louis, Ani Nenkova
Creating Local Coherence: An Empirical Assessment, Annie Louis, Ani Nenkova
Ani Nenkova
Two of the mechanisms for creating natural transitions between adjacent sentences in a text, resulting in local coherence, involve discourse relations and switches of focus of attention between discourse entities. These two aspects of local coherence have been traditionally discussed and studied separately. But some empirical studies have given strong evidence for the necessity of understanding how the two types of coherence-creating devices interact. Here we present a joint corpus study of discourse relations and entity coherence exhibited in news texts from the Wall Street Journal and test several hypotheses expressed in earlier work about their interaction.