Інформаційна технологія для класифікації наукових текстів на основі методу модифікованої логістичної регресії

Об’єкт дослідження: процес класифікації наукових текстів та практичне використання технологій обробки природної мови в освітніх додатках, з метою підвищення ефективності освітнього процесу. Предмет дослідження: методи, моделі машинного навчання та обробки природньої мови у задачах класифікації наукових текстів. Мета магістерської роботи: вдосконалення та пришвидшення процесу класифікації текстів з допомогою моделі логістичної регресії, з метою застосування її у освітніх додатках для покращення освітнього процесу. Методи дослідження. Для створення рекомендаційного та навчального асистента були використані засоби та методи машинного навчання, теорії множин, лінейної алгебри й обробки природної мови. Наукова новизна полягає у тому, що вдосконалено та розширено можливості методу логістичної регресії на основі комбінування його з методом ранжування, що в результаті дозволило використати метод логістичної регресії для навчального асистенті. Практична цінність полягає у тому, що в результаті роботи, було створено прототип навчального асистента, що використовує скомбіновану з методом ранжування модель логістичної регресії для класифікації текстів. Використані методи та підходи у прототипі можуть застосовуватись як при розробці «інтелектуальних» навчальних систем, так й в практиці викладання дисциплін, пов’язаних з обробкою природної мови

Nucleon Spin Fluctuations and Neutrino-Nucleon Energy Transfer in Supernovae

The formation of neutrino spectra in a supernova depends crucially on strength and inelasticity of weak interactions in hot nuclear matter. Neutrino interactions with nonrelativistic nucleons are mainly governed by the dynamical structure function for the nucleon spin density which describes its fluctuations. It has recently been shown that these fluctuations give rise to a new mode of energy transfer between neutrinos and nucleons which inside the neutrinosphere is of comparable or greater importance than ordinary recoil. We calculate numerically the spin density structure function in the limit of a dilute, non-degenerate medium from exact two-nucleon wave functions for some representative nuclear interaction potentials. We show that spectrum and magnitude of the energy transfer can deviate significantly from those based on the Born approximation. They are, however, rather insensitive to the particular nuclear potential as long as it reproduces experimental nucleon scattering phase shifts at energies up to a few tens of MeV. We also compare with calculations based on a one-pion exchange potential in Born approximation and briefly comment on their applicability near the center of a supernova core. Our study is relevant for numerical simulations of the neutrino spectra emerging from type-II supernovae.Comment: 11 latex pages, 3 postscript figures included, uses epsf.sty and revtex.sty in two-column format, submitted to Physical Review

Cause of Death and Predictors of All-Cause Mortality in Anticoagulated Patients With Nonvalvular Atrial Fibrillation : Data From ROCKET AF

M. Kaste on työryhmän ROCKET AF Steering Comm jäsen.Background-Atrial fibrillation is associated with higher mortality. Identification of causes of death and contemporary risk factors for all-cause mortality may guide interventions. Methods and Results-In the Rivaroxaban Once Daily Oral Direct Factor Xa Inhibition Compared with Vitamin K Antagonism for Prevention of Stroke and Embolism Trial in Atrial Fibrillation (ROCKET AF) study, patients with nonvalvular atrial fibrillation were randomized to rivaroxaban or dose-adjusted warfarin. Cox proportional hazards regression with backward elimination identified factors at randomization that were independently associated with all-cause mortality in the 14 171 participants in the intention-to-treat population. The median age was 73 years, and the mean CHADS(2) score was 3.5. Over 1.9 years of median follow-up, 1214 (8.6%) patients died. Kaplan-Meier mortality rates were 4.2% at 1 year and 8.9% at 2 years. The majority of classified deaths (1081) were cardiovascular (72%), whereas only 6% were nonhemorrhagic stroke or systemic embolism. No significant difference in all-cause mortality was observed between the rivaroxaban and warfarin arms (P=0.15). Heart failure (hazard ratio 1.51, 95% CI 1.33-1.70, P= 75 years (hazard ratio 1.69, 95% CI 1.51-1.90, P Conclusions-In a large population of patients anticoagulated for nonvalvular atrial fibrillation, approximate to 7 in 10 deaths were cardiovascular, whereasPeer reviewe

A História da Alimentação: balizas historiográficas

Os M. pretenderam traçar um quadro da História da Alimentação, não como um novo ramo epistemológico da disciplina, mas como um campo em desenvolvimento de práticas e atividades especializadas, incluindo pesquisa, formação, publicações, associações, encontros acadêmicos, etc. Um breve relato das condições em que tal campo se assentou faz-se preceder de um panorama dos estudos de alimentação e temas correia tos, em geral, segundo cinco abardagens Ia biológica, a econômica, a social, a cultural e a filosófica!, assim como da identificação das contribuições mais relevantes da Antropologia, Arqueologia, Sociologia e Geografia. A fim de comentar a multiforme e volumosa bibliografia histórica, foi ela organizada segundo critérios morfológicos. A seguir, alguns tópicos importantes mereceram tratamento à parte: a fome, o alimento e o domínio religioso, as descobertas européias e a difusão mundial de alimentos, gosto e gastronomia. O artigo se encerra com um rápido balanço crítico da historiografia brasileira sobre o tema

Influence of Pulse Amplitude and Frequency on Plasma Properties of a Pulsed Low-Current High-Voltage Discharge Operated at Atmospheric Pressure

Non-equilibrium conditions in plasma are often achieved by pulsed power delivery, where the pulse shape and repetition rate determine the properties of the plasma constituents and thus its chemical reactivity. The evaluation of the latter is becoming increasingly important to understand the observed effects, especially when new application fields are targeted. The composition of the plasma and the occurring chemical reactions can be calculated using various models. Thereby, the temperature of the electrons, the electron number density, as well as the heavy particle temperature are usually required as the basis of such calculations. In this work, the influence of pulse amplitude and repetition rate on these plasma parameters is determined by laser scattering for a low-current, high-voltage discharge operated with nitrogen at atmospheric pressure. In particular, the characteristic parameters regarding the plasma free electrons in such discharges have not yet been experimentally determined to this extent. The results are validated by spectroscopic measurements, i.e., the electron density is estimated from the Stark broadening of the hydrogen beta line and the heavy particle temperature is estimated by fitting the spectrum of nitrogen molecular transitions. Depending on the operating frequency, a pure nitrogen discharge with an input power of about 650 W displays an electron density between 1.7×1021m−3 and 2.0×1021m−3 with electron temperatures in the range of 40,000 K and heavy particle temperatures of about 6000 K in the core of the discharge channel. Furthermore, a relatively slow electron recombination rate in the range of 20 µs is observed

Spectroscopic Characterization of a Pulsed Low-Current High-Voltage Discharge Operated at Atmospheric Pressure

The advantages of pulsed low-current high-voltage discharges operated at atmospheric pressure and the ease with which such discharges can be implemented industrially contributed to their popularity. However, the high reactivity of a pulsed plasma implies that thorough diagnostics are needed to fully understand the interactions inside these plasmas. Some of the key parameters determining plasma properties of low-current discharges are the electron number density and the temperature of heavy particles. Both parameters can be determined experimentally with spectroscopic techniques, for example by investigating the broadening of spectral lines due to the Stark effect and by fitting synthetic spectra to molecular transitions. To the authors’ knowledge, experimentally determined electron densities for pulsed low-current discharges operated in a power range between 300 W and 1000 W have not been performed in previous works. Thus, in this work, the electron number density and temperature of heavy particles of one of several commercially available plasma systems are determined by means of emission spectroscopy

A Simple and Compact Laser Scattering Setup for Characterization of a Pulsed Low-Current Discharge

Recent research trends show an increasing interest in non-equilibrium plasmas operated at atmospheric pressure, which are often used to tackle several environmental and health issues. Nevertheless, due to the complexity of the applications, these trends also show the need for a comprehensive characterization of such plasmas for a deeper understanding of the observed effects. One of the diagnostic methods for experimental determination of key parameters which affect the reactivity of a plasma, i.e., electron temperature, electron density and heavy particle temperature, is laser scattering. In this work, an approach based on a simple and compact laser scattering setup is proposed, which allows an estimation of the above parameters without any additional changes in the acquisition settings. Thus, the experimental effort and possible sources of error can be reduced. The proposed setup is tested experimentally with a commercially available pulsed plasma system, and the results are compared to available data. From this comparison, it is found that the plasma parameters estimated with the proposed scattering setup are plausible