• Title/Summary/Keyword: Estimating functions

Search Result 307, Processing Time 0.031 seconds

Efficient estimation and variable selection for partially linear single-index-coefficient regression models

  • Kim, Young-Ju
    • Communications for Statistical Applications and Methods
    • /
    • v.26 no.1
    • /
    • pp.69-78
    • /
    • 2019
  • A structured model with both single-index and varying coefficients is a powerful tool in modeling high dimensional data. It has been widely used because the single-index can overcome the curse of dimensionality and varying coefficients can allow nonlinear interaction effects in the model. For high dimensional index vectors, variable selection becomes an important question in the model building process. In this paper, we propose an efficient estimation and a variable selection method based on a smoothing spline approach in a partially linear single-index-coefficient regression model. We also propose an efficient algorithm for simultaneously estimating the coefficient functions in a data-adaptive lower-dimensional approximation space and selecting significant variables in the index with the adaptive LASSO penalty. The empirical performance of the proposed method is illustrated with simulated and real data examples.

Whole Genome Sequencing and Gene Prediction of Cynodon transvaalensis

  • Sol Ji Lee;Chang soo Kim
    • Proceedings of the Korean Society of Crop Science Conference
    • /
    • 2022.10a
    • /
    • pp.237-237
    • /
    • 2022
  • Cynodon transvaalensis belongs to the warm-season grasses and is one of the economically and ecologically important crops. Cynodon species with high heterozygosity are difficult to assemble, so genome research has not been actively conducted. In this study, hybrid assembly was performed by sequencing with Illumina and PacBio. As a result of the assembly, the number of scaffolds and the length of N50 were 1,392, 928 kb, respectively. The completeness of the assembly was confirmed by BSUCO at 98.3%. In addition, as a result of estimating the size of the assembled genome by K-mer analysis (k=25), it was approximately ~413 Mb. A total of 37,060 cds sequences were annotated in the assembled genome, and their functions were identified through blast. After that, we try to complete the assembled genome into a pseudochromosome-level genome through Hi-C technology. These results will not only help to understand the complex genome composition of african bermudagrass, but also provide a resource for genomic and evolutionary studies of grass and other plant species.

  • PDF

Optimal Latinized partially stratified sampling for structural reliability analysis

  • Majid Ilchi Ghazaan;Amirreza Davoodi Yekta
    • Structural Engineering and Mechanics
    • /
    • v.92 no.1
    • /
    • pp.111-120
    • /
    • 2024
  • Sampling methods are powerful approaches to solving the problems of structural reliability analysis and estimating the failure probability of structures. In this paper, a new sampling method is proposed offering lower variance and lower computational cost for complex and high-dimensional problems. The method is called Optimal Latinized partially stratified sampling (OLPSS) as it is based upon the Latinized Partially Stratified Sampling (LPSS) which itself is based on merging Stratified Sampling (SS) and Latin Hypercube Sampling (LHS) algorithms. While LPSS has a low variance, it may suffer from a lack of good space-filling of its generated samples in some cases. In the OLPSS, this issue has been resolved by employing a new columnwise-pairwise exchange optimization procedure for sample generation. The efficiency of the OLPSS has been tested and reported under several benchmark mathematical functions and structural examples including structures with a large number of variables (e.g., a structure with 67 variables). The proposed method provides highly accurate estimates of the failure probability of structures with a significantly lower variance relative to the Monte Carlo simulations, Latin Hypercube, and standard LPSS.

Verification on PTF (Pedo-Transfer Function) estimating soil water retention based on soil properties (토양특성 기반 토양수분 함량 예측을 위한 PTF 적용성 검정)

  • Hur, Seung-Oh;Sonn, Yeon-Gyu;Hyun, Byung-Kewn;Shin, Kook-Sik;Oh, Taek-Keun;Kim, Jeong-Gyu
    • Korean Journal of Agricultural Science
    • /
    • v.41 no.4
    • /
    • pp.391-398
    • /
    • 2014
  • Identifying soil water content as a major factor for evaluating irrigation and water resource is a primary module to develop a prediction model. A variety of PTFs (Pedo-Transfer Functions) are applied in the models to estimate soil water content, the analysis techniques, however, which compare the estimated from models and the measured by instruments, are not reached at the level to demonstrate the effectiveness of the PTFs in Korea. Many soil physicians such as Eom, Peterson, Rawls, Saxton, Bruand, Baties, Tomasella & Hodnett (T&H), and Minasny, have developed analytic models using PTFs. Soil data for the analysis used soil water contents on 347 soil series (10 kPa), 358 soil series (33 kPa), 356 soil series (1,500 kPa) established by NAAS (National Academy of Agricultural Science). A coefficient of determination on soil water content at 10, 33 and 1,500 kPa was the highest as 0.5932 in EM (Eom model), 0.6744 in REM (Rawls model) and 0.6108 in REM, respectively. In conclusion, it is strongly suggested that the use of EM or REM is suitable for estimating soil water content in Korea although SM (Saxton model) has been widely used.

Interference Analysis of TV Signal Affected by Flights of An Airplane around KimPo International Airport Circumference (항공기 운항으로 인한 김포국제공항 주변지역의 TV 수신 장애 분석)

  • Lee, Chan-Joo;Kim, Bong-Cheol;Cho, Sung-Joon
    • Journal of Advanced Navigation Technology
    • /
    • v.3 no.1
    • /
    • pp.20-31
    • /
    • 1999
  • In this paper, we have chosen KimPo International Airport as an area for estimating the flutter interference, in order to analyze the flutter interference. The field test at 25 points around KimPo International Airport and the simulation have been performed for estimating the flutter interference. We consider the received power of a direct wave, the height of an antenna, the ERP of a transmitting point, transmit frequency, and the reflection coefficients of an airplane, the transmit/receive point coordinates as estimation functions for the flutter. From the results, we have found that the flutter interference from flights is very serious around the route of flight circumference, and often occurs when the height of an airplane is low, range from 40 to 240 m. Besides, the degree of the flutter interference can be changed according to the distance between an airplane and a transmitting point, elevation angle, and the reflection coefficients of an airplane.

  • PDF

Deep learning-based approach to improve the accuracy of time difference of arrival - based sound source localization (도달시간차 기반의 음원 위치 추정법의 정확도 향상을 위한 딥러닝 적용 연구)

  • Iljoo Jeong;Hyunsuk Huh;In-Jee Jung;Seungchul Lee
    • The Journal of the Acoustical Society of Korea
    • /
    • v.43 no.2
    • /
    • pp.178-183
    • /
    • 2024
  • This study introduces an enhanced sound source localization technique, bolstered by a data-driven deep learning approach, to improve the precision and accuracy of direction of arrival estimation. Focused on refining Time Difference Of Arrival (TDOA) based sound source localization, the research hinges on accurately estimating TDOA from cross-correlation functions. Accurately estimating the TDOA still remains a limitation in this research field because the measured value from actual microphones are mixed with a lot of noise. Additionally, the digitization process of acoustic signals introduces quantization errors, associated with the sampling frequency of the measurement system, that limit the precision of TDOA estimation. A deep learning-based approach is designed to overcome these limitations in TDOA accuracy and precision. To validate the method, we conduct comprehensive evaluations using both two and three-microphone array configurations. Moreover, the feasibility and real-world applicability of the suggested method are further substantiated through experiments conducted in an anechoic chamber.

Time-Varying Effects of Oil Shocks on the Korean Economy (한국경제에 미치는 유가충격의 시간-가변적 효과에 관한 연구)

  • Cha, Kyungsoo
    • Environmental and Resource Economics Review
    • /
    • v.27 no.3
    • /
    • pp.495-520
    • /
    • 2018
  • Because of structural changes in the international oil market and the economy, it is widely recognized that the impact of oil shocks on the economy has weaken since the mid-1980s. This study tries to examine the validity of the recent perception about the relationship between oils shocks and the economy, estimating the time-varying effects of oil shocks on the Korean economy. The results show that the dynamic effects of oil shocks normalized to a one standard deviation has been relatively constant, in contrast to the recent perception and a number of existing studies. In addition, because the shape of impulse response functions at each point in time spanning from 1984:II to 2017:IV has not been changed significantly, it seems that the propagation mechanism of oil shocks also has not been substantially altered. These findings indicate that even though structural changes of the economy, such as the reduction in the share of oil consumption and the spread of high-efficiency energy technologies, have been rapidly progressed, it is not still enough to offset the negative effects of oil shocks. Rather, it seems that the recent perception about the shrinking effects of oil shocks is mainly due to the assumptions that do not reflect changes in the size of oil shocks. In particular, this problem appears more pronounced in the case of the typical a one standard deviation increase oil shock under homoskedasticity assumption, which is widely adopted in the most VAR analyses. Therefore, in estimating the effects of oil shocks on the economy, it is important to specify the correct model and normalization method, to reflect changes in the size of oil shocks.

The Local Behavior of Stiffened Plates with Open Ribs Subject to a Concentrated Load (집중하중을 받는 개단면 리브 보강판의 국부 거동)

  • Chu, Seok Beom
    • Journal of Korean Society of Steel Construction
    • /
    • v.17 no.5 s.78
    • /
    • pp.593-604
    • /
    • 2005
  • In this paper, the parametric study on the local displacement and the local moment due to a concentrated load is performed for stiffened plates with open ribs and the orthotropic rigidity ratio of stiffened plates is selected as the parameter. For estimating the local behavior, stiffened plates loaded on the center of plates between the ribs were considered and for the global behavior, stiffened plates loaded on the rib at the center of plates were analyzed. The Analyzed results for the local behavior of stiffened plates show that the increasing ratio of the local moment according to rib sizes is constant regardless of rib spaces and the ratio of the local displacement to the global displacement can be expressed as a function of the rib space and the rigidity ratio. The application of functions to examples shows good accuracy in comparison with the local behavior of stiffened plates loaded on the center of plates and the application to the orthotropic analysis of stiffened plates improves accuracy. Therefore, using functions proposed in this study, the local behavior can easily be estimated from the global behavior of stiffened plates with open ribs.

Optimal Thresholds from Mixture Distributions (혼합분포에서 최적분류점)

  • Hong, Chong-Sun;Joo, Jae-Seon;Choi, Jin-Soo
    • The Korean Journal of Applied Statistics
    • /
    • v.23 no.1
    • /
    • pp.13-28
    • /
    • 2010
  • Assuming a mixture distribution for credit evaluation studies, we discuss estimating threshold methods to minimize errors that default borrowers are predicted as non defaults or non defaults are regarded as defaults. A method by using statistical hypotheses tests, the most powerful test and generalized likelihood ratio test, for the probability density functions which are defined with the score random variable and the parameter space consisted of only two elements such as the default and non default states is proposed to estimate a threshold. And anther optimal thresholds to maximize classification accuracy measures of the accuracy and the true rate for ROC and CAP curves are estimated as equations related with these probability density functions. Three kinds of optimal thresholds in terms of the hypotheses testing, the accuracy and the true rate are obtained from normal random samples with various means and variances. The sums of the type I and type II errors corresponding to each optimal threshold are obtained and compared. Finally we discuss about their efficiency and derive conclusions.