• Natural Product Sciences
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• 제11권3호
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• pp.170-173
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• 2005

Compounds of (+)-5,5'-dimethoxylariciresinol (1) and (3S,5R,6S,7E)-5,6-epoxy-3-hydroxy-7-megastigmen-9-one (2) were isolated from an EtOAc extract of the whole plant of Sasa borealis (Hack.) Makino (Gramineae) for the first time in the present investigation. The structures of compounds were identified by analysis of spectral data including 1D- and 2D-NMR spectra as well as by comparison of their data with the published values. These compounds have never been isolated previously from the family Gramineae.

• Bulletin of the Korean Chemical Society
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• 제32권1호
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• pp.109-112
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• 2011

A new derivative of tacrolimus was evaluated for its molecular weight, using LC-MS of the tacrolimus bulk active pharmaceutical ingredient (API) recovered through the purification of crude tacrolimus produced by Streptomyces clavuligerus CKD-1119. In addition, the molecular weight of the new derivative of tacrolimus was found to be at m/z 818 and was identified by $^{13}C$-NMR with peak assignments based on the differences in methyl group location resulting from the chemical structure. The structure of the new derivative, an unknown impurity of tacrolimus, was found to be 18-methyltacrolimus through comparison of the spectral data of the structural differences between ascomycin, tacrolimus, and the new derivative 18-methyltacrolimus.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.125-129
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• 2003

The identification of location and strength distribution of extended noise sources is important in the practical noise control engineering, especially in the viewpoint of dealing with the inherent nature of noise problem in question. For noise source ranking inside an automotive vehicle, the window method has been mainly used due to its simplicity. However, time and cost drawbacks in the measurement and inaccuracy due to low-frequency tunneling and lack of phase information have been a serious problem in using this method. In this study, the inverse FRF method was employed to carry out the noise source ranking inside an automotive vehicle and it was also used to predict the interior sound pressure with the change of sound insulation materials. As a result, it was found that the source contribution of vehicle panels could be successfully identified in comparison with the window method. The sound pressure at driver's ear position was predicted based on the obtained data and was compared with the measured data. The agreement in spectral trends was acceptable and their difference in level was within 3㏈ above 500㎐.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2000년도 춘계 학술대회 논문집 통권 3호 Proceedings of the 2000 KSRS Spring Meeting
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• pp.49-54
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• 2000

Conventional methods for measuring winds provide wind velocity observations over limited area and time period. The use of satellite imagery for measuring wind velocity overcomes some of these limitations by providing wide area and near condinuous coverage. And its accurate depiction is essential for operational weather forecasting and for initialization of NWP models. GMS-5 provides full disk images at hourly intervals. At four times each day - 0500, 1100, 1700, 2300 hours UTC-a series of three images is received, separated by thirty minutes, centered at the four times. The current wind system generates winds from sets of 3 infrared(IR) images, separated by an hour, four times a day. It also produces visible(VIS) and water vapor(WV) image-based winds from half-hourly imagery four times a day. The derivation of wind from satellite imagery involves the identification of suitable cloud targets. tracking the targets on sequential images, associating a pressure height with the derived wind vector, and quality control. The aim of this research is to incorporate imagery from other available spectral channels and examine the error characteristics of winds derived from these images.

• Smart Structures and Systems
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• 제17권2호
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• pp.209-230
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• 2016

The Canton Tower is a high-rise slender structure with a height of 610 m. A structural health monitoring system has been instrumented on the structure, by which data is continuously monitored. This paper presents an investigation on the identified modal properties of the Canton Tower using ambient vibration data collected during a whole day (24 hours). A recently developed Fast Bayesian FFT method is utilized for operational modal analysis on the basis of the measured acceleration data. The approach views modal identification as an inference problem where probability is used as a measure for the relative plausibility of outcomes given a model of the structure and measured data. Focusing on the first several modes, the modal properties of this supertall slender structure are identified on non-overlapping time windows during the whole day under normal wind speed. With the identified modal parameters and the associated posterior uncertainty, the distribution of the modal parameters in the future is predicted and assessed. By defining the modal root-mean-square value in terms of the power spectral density of modal force identified, the identified natural frequencies and damping ratios versus the vibration amplitude are investigated with the associated posterior uncertainty considered. Meanwhile, the correlations between modal parameters and temperature, modal parameters and wind speed are studied. For comparison purpose, the frequency domain decomposition (FDD) method is also utilized to identify the modal parameters. The identified results obtained by the Bayesian method, the FDD method and a finite element model are compared and discussed.

• 대한원격탐사학회지
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• 제40권1호
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• pp.93-101
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• 2024

Accurate field crop classification is essential for various agricultural applications, yet existing methods face challenges due to diverse crop types and complex field conditions. This study aimed to address these issues by combining support vector machine (SVM) models with multi-seasonal unmanned aerial vehicle (UAV) images, texture information extracted from Gray Level Co-occurrence Matrix (GLCM), and RGB spectral data. Twelve high-resolution UAV image captures spanned March-October 2021, while field surveys on three dates provided ground truth data. We focused on data from August (-A), September (-S), and October (-O) images and trained four support vector classifier (SVC) models (SVC-A, SVC-S, SVC-O, SVC-AS) using visual bands and eight GLCM features. Farm maps provided by the Ministry of Agriculture, Food and Rural Affairs proved efficient for open-field crop identification and served as a reference for accuracy comparison. Our analysis showcased the significant impact of hyperparameter tuning (C and gamma) on SVM model performance, requiring careful optimization for each scenario. Importantly, we identified models exhibiting distinct high-accuracy zones, with SVC-O trained on October data achieving the highest overall and individual crop classification accuracy. This success likely stems from its ability to capture distinct texture information from mature crops.Incorporating GLCM features proved highly effective for all models,significantly boosting classification accuracy.Among these features, homogeneity, entropy, and correlation consistently demonstrated the most impactful contribution. However, balancing accuracy with computational efficiency and feature selection remains crucial for practical application. Performance analysis revealed that SVC-O achieved exceptional results in overall and individual crop classification, while soybeans and rice were consistently classified well by all models. Challenges were encountered with cabbage due to its early growth stage and low field cover density. The study demonstrates the potential of utilizing farm maps and GLCM features in conjunction with SVM models for accurate field crop classification. Careful parameter tuning and model selection based on specific scenarios are key for optimizing performance in real-world applications.

• Structural Engineering and Mechanics
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• 제26권6호
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• pp.709-723
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• 2007

Considering the vast usage of time-history dynamic analyses to calculate structural responses and lack of sufficient and suitable earthquake records, generation of artificial accelerograms is very necessary. The main target of this paper is to present a novel method based on nonstationary Kanai-Tajimi model and wavelet transform to generate more artificial earthquake records, which are compatible with target spectrum. In this regard, the generalized nonstationary Kanai-Tajimi model to include the nonstationary evaluation of amplitude and dominant frequency of ground motion and properties of wavelet transform is used to generate ground acceleration time history. Application of the method for El Centro 1940 earthquake and two Iranian earthquakes (Tabas 1978 and Manjil 1990) is presented. It is shown that the model and identification algorithms are able to accurately capture the nonstationary features of these earthquake accelerograms. The statistical characteristics of the spectral response of the generated accelerograms are compared with those for the actual records to demonstrate the effectiveness of the method. Also, for comparison of the presented method with other methods, the response spectra of the synthetic accelerograms compared with the models of Fan and Ahmadi (1990) and Rofooei et al. (2001) and it is shown that the response spectra of the synthetic accelerograms with the method of this paper are close to those of actual earthquakes.

• Natural Product Sciences
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• 제25권4호
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• pp.348-353
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• 2019

Soluble epoxide hydrolases (sEH) are enzymes present in all living organisms, metabolize epoxy fatty acids to 1,2-diols. sEH in the metabolism of polyunsaturated fatty acids plays a key role in inflammation. In addition, the endogenous lipid mediators in cardiovascular disease are also broken down to diols by the action of sEH that enhanced cardiovascular protection. In this study, sEH inhibitory guided fractionation led to the isolation of five phenolic compounds trans-resveratrol (1), trans-piceatannol (2), sulfuretin (3), (+)-balanophonin (4), and cassigarol E (5) from the ethanol extract of the seeds of Passiflora edulis Sims cultivated in Vietnam. The chemical structures of isolated compounds were determined by the interpretation of NMR spectral data, mass spectra, and comparison with data from the literature. The soluble epoxide hydrolase (sEH) inhibitory activity of isolated compounds was evaluated. Among them, trans-piceatannol (2) showed the most potent inhibitory activity on sEH with an IC₅₀ value of 3.4 μM. This study marks the first time that sulfuretin (3) was isolated from Passiflora edulis as well as (+)-balanophonin (4), and cassigarol E (5) were isolated from Passiflora genus.

• 전기학회논문지
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• 제66권2호
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• pp.261-284
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• 2017

This paper describes the results of a low-frequency oscillation analysis using data measured in PMU installed in the KEPCO system, and the comparison with eigenvalues computed from the linear model. The dominant oscillation modes are estimated by applying various algorithms. The algorithms are: the extended Prony method; multiple time interval parameter estimation method; subspace system identification method; and spectral analysis. From the measurement data, modes of frequency 0.68[Hz] and 0.92[Hz] were estimated, and modes of frequency 0.63[Hz] and 0.80[Hz] were computed from the eigenvalue calculation. There was a difference between the mode estimated from measurement data and that from the linear model. This is possibly because of an error in the dynamic data of the KEPCO system used in eigenvalue calculation. Because wide area modes exist in the KEPCO system, these modes should be monitored continuously for the reliable operation of the system. In order to prevent total blackouts caused by wide area oscillation, moreover, contingency analysis should be performed in relation to this mode and appropriate measures should be established.

• 대한화학회지
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• 제39권7호
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• pp.564-571
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• 1995

NaOH 수용액에서 과산화수소로 2-thiobiuret를 산화성 고리화 반응시켜 5-amion-2H-1, 2, 4-thiadiazoline-3-one을 합성하였다. 이 화합물에 대한 토오토머화 현상을 IR, $^1H$ NMR, $^13C$ NMR 등의 분광학적인 방법으로 고찰하고 분자괘도함수에 의한 이론적 계산 결과와 비교 검토하였다. 이 결과 5-Amion-2H-1, 2, 4-thiadiazoline-3-one는 락팀형보다는 락탐형으로 존재한다. 알킬화 반응을 여러 염기로 DMF 용매와 이상용매계 $H_2O$-THF에서 시도한 결과 N-2 위치에서 알킬화 반응이 일어남을 알 수 있었다. 알킬화 반응은 할로켄화 알칸을 $Li_2CO_3$/DMF의 조건하에서 반응시켰을 때 가장 수율이 좋았다. N-2 위치에서 알킬화 반응 생성물의 확인은 IR, $^1H$ NMR과 $^13C$ NMR 등의 분광학적인 방법과 5-methyl-2-thiobiuret를 thiobiuret와 같이 산화성 고리화 반응을 통하여 5-amino-2-methyl-1,2,4-thiadiazolidine-3-one 표준 시료를 합성하여 알킬화 반응 생성물과 비교 확인하였다.