• Journal of the Korean Magnetic Resonance Society
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• v.10 no.1
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• pp.46-58
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• 2006

With a simple pulse sequence ($\pi/2$-{gradient, duration T}-acquisition) in solution NMR, detected signal has slowly grown up to percents of the equilibrium magnetization. The source of this unusual resurrection of dephased magnetization after a crushed gradient is cross-correlated effects of radiation damping and the distant dipolar field, which has been demonstrated by a numerical simulation and theoretical analysis.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.594-601
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• 1997

Propeller fans are commonly equipped in outdoor units of air-conditioners to provide effective cooling in a dried heat exchanger. A new design technique was developed to satisfy requirements of aerodynamic and aeroacoustic performance, which employs the intersection method of two cylinders for mean camber line. Three proto-types of propeller fan including Palm-Shaped, Highly-Swept(PSHS) fan (proto 3)were not only to provide low lift forces for dipole sound, but also to reduce the organized tip vortices interacting with the fan guide causing narrow-banded rotating instabilities. Cross-correlation technique was applied to study flow noise source characteristics for three proto-type fans designed. The cross-correlations between a microphone at far field and a hot-wire sensor at near field show that flows near hub region of proto 3 fan are less organized and the flow structures especially at high flow rate coefficients for proto 3 fan are less correlated with noise generated than other proto-types fans.

• Annual Conference on Human and Language Technology
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• 2017.10a
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• pp.281-284
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• 2017

On the basis of studies that show multi-word combinations, that is the field of phraseology, this study aims to examine relationship between the quality of text and phraseological competence in L2 English writing, following Yves Bestegen et al. (2014). Using two different association scores, t-score and Mutual Information(MI), which are opposite ways of measuring phraseological competence, in terms of scoring frequency and infrequency, bigrams from L2 writers' text scored based on a reference corpus, GloWbE (Corpus of Global Web based English). On a cross-sectional approach, we propose that the quality of the essays and the mean MI score of the bigram extracted from YELC, Yonsei English Learner Corpus, correlated to each other. The negative scores of bigrams are also correlated with the quality of the essays in the way that these bigrams are absent from the reference corpus, that is mostly ungrammatical. It indicates that increase in the proportion of the negative scored bigrams debases the quality of essays. The conclusion shows the quality of the essays scored by MI and t-score on cross-sectional approach, and application to teaching method and assessment for second language writing proficiency.

• 한국어정보학회:학술대회논문집
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• 2017.10a
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• pp.281-284
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• 2017

On the basis of studies that show multi-word combinations, that is the field of phraseology, this study aims to examine relationship between the quality of text and phraseological competence in L2 English writing, following Yves Bestegen et al. (2014). Using two different association scores, t-score and Mutual Information(MI), which are opposite ways of measuring phraseological competence, in terms of scoring frequency and infrequency, bigrams from L2 writers' text scored based on a reference corpus, GloWbE (Corpus of Global Web based English). On a cross-sectional approach, we propose that the quality of the essays and the mean MI score of the bigram extracted from YELC, Yonsei English Learner Corpus, correlated to each other. The negative scores of bigrams are also correlated with the quality of the essays in the way that these bigrams are absent from the reference corpus, that is mostly ungrammatical. It indicates that increase in the proportion of the negative scored bigrams debases the quality of essays. The conclusion shows the quality of the essays scored by MI and t-score on cross-sectional approach, and application to teaching method and assessment for second language writing proficiency.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.36 no.4
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• pp.319-323
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• 1991

To determine how closely related to field lodging for several characters affecting the field lodging for several characters affecting field lodging, and to obtain the basic information for selection of lodging resistance genotype, an experiment was conducted with 10 varieties from May to Oct., 1990 at the experimental field in Sunchon Xational University. Culm length, dry weight per unit culm length (W/1), bending moment per unit culm diameter (W1/d), lodging index (L), bending load ratio (W1/P), and index of critical lodging load(W$_{s}$$^{2}$/1$^4$) were the most closely related characters to field lodging. Culm length showed highly significant positive correlation coefficient with field lodging(r=0.7607), but it may be undesirable to judge lodging resistance of genotype by culm length itself without consideration of culm stiffness. Considering the difficulty and time-consuming to measure the character, clum length, W/1, W1/d, and W$_{s}$$^{2}$/1$^4$ were easy to measure and hence would be the most useful variables to judge the lodging resistance of genotype. Culm diameter, cross sectional area of culm, thickness of culm wall, and the second inertia moment of cross section of culm were not correlated with field lodging at all. Breaking strength of culm showed significantly negative correlation coefficient (r=-0.3986) with field lodging.ing.

• Journal of the Korean Data and Information Science Society
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• v.23 no.2
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• pp.385-392
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• 2012

Logistic regression is a well known binary classification method in the field of statistical learning. Mixed-effect regression models are widely used for the analysis of correlated data such as those found in longitudinal studies. We consider kernel extensions with semiparametric fixed effects and parametric random effects for the logistic regression. The estimation is performed through the penalized likelihood method based on kernel trick, and our focus is on the efficient computation and the effective hyperparameter selection. For the selection of optimal hyperparameters, cross-validation techniques are employed. Numerical results are then presented to indicate the performance of the proposed procedure.

• The Journal of the Acoustical Society of Korea
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• v.43 no.5
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• pp.475-483
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• 2024

This paper examines the signal processing parameters of the field differencing method, a technique for estimating the source velocity or distance using a single receiver. The constraints that must be obeyed during the application of the field differencing method and the effect of the parameters on the velocity estimation performance were analyzed. Several cases identified in this study using the SWellEX-96 experiment data show that when applying the sound field differential technique, large errors may occur in the radial source velocity estimation results depending on parameter settings. The study confirmed that the influence of the processing parameters can vary depending on the signal frequency, and presented guidelines for selecting parameter values of the field differencing method for correct radial velocity estimation.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.11a
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• pp.48.1-48.1
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• 2009

Performance of organic field-effect transistors (OFETs) with various temperature-cured polyacrylate(PA) copolymer as a gate insulator was studied. The PA thin film, which was cured at an optimized temperature, showed high dielectric strength (>7 MV/cm), low leakage current density ($5{\times}10^{-9}\;A/cm^2$ at 1 MV/cm) and enabled negligible hysteresis in MIS capacitor and OFET. A field-effect mobility of ${\sim}0.6\;cm^2/V\;s$, on/off current ratio (Ion/Ioff) of ${\sim}10^5$ and inverse subthreshold slope (SS) as low as 1.22 V/decwere achieved. The high dielectric strength made it possible to scale down the thickness of dielectric, and low-voltage operation of -5 V was successfully realized. The chemical changes were monitored by FT-IR. The morphology and microstructure of the pentacene layer grown on PA dielectrics were also investigated and correlated with OFET device performance.

• Journal of Korea Water Resources Association
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• v.31 no.2
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• pp.145-153
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• 1998

In this paper the first- and second order statistics of soil moisture are derived using the Washita '92 data. Also the possible correlations among the soil texture, the brightness temperature, the NDVI and the soil moisture are investigated based in the linear regression study. Only the correlation between the soil moisture and the brightness temperature shows significant values. The soil moisture decay coefficients in time were estimated for each soil type and cross-checked by calculating the last rainfall time before the observation to be about 20days in all different soil types. The second-order statistics of soil moisture based on the correlogram and the spectrum was analyzed to derive the data characteristics and compared with those of the NDVI and the soil texture. This analysis shows that the soil moisture within the highly correlated soil texture field is affected much by the relatively less correlated vegetation field in the Washita area, where the effect of topography is known to be small. The soil moisture media was derived and its parameters were estimated successfully using the first - and sedcond -order statistics.

• Journal of Environmental Health Sciences
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• v.40 no.6
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• pp.442-453
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• 2014

Objectives: Persistent organic pollutants (POPs) are known to be the detrimental chemicals in the body, even at low levels, and are stored in adipose tissue. Recently, POPs have been reported to be associated with chronic diseases, including cancer and cardiovascular disease, and aging and obesity are reported as common factors in chronic disease. However, there have been only a few studies on the associations of POPs with age and body mass index (BMI) in Korea. Therefore, we analyzed the associations of serum POPs levels with age and BMI in Korea. Methods: This cross-sectional study includes 444 subjects (253 men and 191 women) from the Korean Cancer Prevention Study-II (2004-2011). Serum levels of 33 polychlorinated biphenyls (PCBs) and 19 organochlorine pesticides (OCPs) were measured by a gas chromatographer (Agilent 6890) coupled to high resolution mass spectrometer (JEOL JMS-800D). Results: Concentrations of PCB 153 (men: 12.26 ng/g lipid, women: 10.50 ng/g lipid) and p,p'-DDE (men: 94.66 ng/g lipid, women: 96.66 ng/g lipid) were the highest among serum PCBs and OCPs, respectively. PCBs and OCPs were significantly positively correlated with age in both sexes. After adjustment for age, non-dioxin like PCBs were significantly negatively correlated with body mass in women. However, cis-heptachlor epoxide was significantly positively correlated with body mass index in both sexes. When analyzed by sex, stronger associations were shown between POPs and age in men and POPs and BMI in women. Conclusion: These results may provide baseline data for the study of POPs and for the health management field in Korea.