著者

Sun Chao Yang Yi-xin

出版者

ACOUSTICAL SOCIETY OF JAPAN

雑誌

Acoustical science and technology (ISSN:13463969)

巻号頁・発行日

vol.25, no.1, pp.2-8, 2004

参考文献数

9

被引用文献数

8

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The problem of beamforming and related beamspace high resolution direction-of-arrival (DOA) estimation is studied in this paper. All beamspace processing methods are based on the beam outputs and the beampattern design plays an important role in providing high quality beam output data for further processing. Three typical situations which are frequently encountered in practical sonar system working environment and the most widely studied MUSIC algorithm are considered herein. First, when isotropic noise is the dominant noise at sensors, conventional beamforming techniques provide the optimum performance in the sense that DOA estimate is the ML estimate. Good DOA estimates are obtainable by applying MUSIC to the beam outputs directly. Then, uncorrelated interferes with much higher strength than the wanted signals are assumed to be present in the sidelobe region, and low sidelobe Dolph-Chebyshev and adaptive MVDR beampatterns are designed to guarantee the performance of MUSIC. And finally, the robustness of conventional techniques is combined with the adaptivity of MVDR beamforming to deal with the situation when the interfere in the sidelobe region is strongly correlated with one of the wanted sources. Performance in all three situations is studied with numerical examples.

著者

SU Shih-Hao KUO Hung-Chi HSU Li-Huan YANG Yi-Ting

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.90, no.5, pp.721-736, 2012

被引用文献数

57

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We studied the temporal and spatial characteristics of extreme typhoon rainfall in Taiwan using Central Weather Bureau hourly precipitation data from 21 surface stations during the past 51 years (1960-2010). Extreme rainfall is defined as 95th percentile intensity of total rain events, or equivalently, rain events greater than 9 mm hr^-1 which contribute 40% to the total rain amount in Taiwan. It was found that approximately 70% (20%) of extreme rain is in the typhoon season (Mei-Yu) from July to October (from May to June). There are significant variations of typhoon extreme rainfall over the annual and decadal time scales, with larger extreme rainfall values and events in the periods of 1960-1976 and 1994-2010, and less in the 1977-1993 period. The recent 1994-2009 period has the most extreme rainfall and events, as well as, inter-annual variability. In contrast, there are strong inter-annual variations of Mei-Yu extreme rainfall, but no significant decadal variations. The averaged typhoon rain intensity, however, is about the same, being 19 mm hr^-1 in all these three periods. Our analysis indicates that the typhoon extreme rainfall spatial pattern is phased locked with the Central Mountain Range, Taiwan. In general, the amount of extreme rainfall was related to the typhoon translation speed and duration time, but not typhoon intensity. Slower speeds and longer duration time lead to larger extreme rainfall values. Our analysis also indicate that the mean duration time of Taiwan landfall typhoons with northern tracks (tracks north of 23 degrees latitude) is about 3 hours longer than that of southern track typhoons in the last 51 years, and is more likely to produce three times as much extreme rainfall. The interactions of summer or winter monsoons with typhoons are also important factors that may contribute to the extreme rainfall in Taiwan. Examples of extreme rainfall due to typhoon circulation interaction with summer and winter monsoon flows are presented. Monsoon water vapor supply, typhoon slow translation speed, and mesoscale convection due to typhoon-monsoon flow interactions are the key factors in extreme precipitation events.

著者

Zheng Zhihui Yang Yi Shao Huayi Liu Zongying Lu Xinhua Xu Yanni He Xiaobo Jiang Wei Jiang Qin Zhao Baohua Zhang Hua Li Zhuorong Si Shuyi

出版者

公益社団法人 日本薬学会

雑誌

Biological and Pharmaceutical Bulletin (ISSN:09186158)

巻号頁・発行日

vol.34, no.10, pp.1631-1634, 2011

被引用文献数

6

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In our previous study, two synthetic thiophenes such as IMB-05 and IMB-15 were found as peroxisome proliferator-activated receptor gamma (PPARγ) agonists and exhibited beneficial effects on glucose tolerance of diabetic mice <i>in vivo</i>. In the present study, their effect on the transactivity of other nuclear receptors was further investigated. IMB-05 and IMB-15 could not only activated PPARγ but also efficiently activate PPARα in GAL4-hPPARα/γ (ligand binding domain (LBD)) chimeric receptor assay and PPAR response element (PPRE)-luc reporter gene assay with EC₅₀ values of 1.8—5.2 μ<small>M</small>, whereas no activity was observed in other nuclear receptor assays. In addition, the maximal efficacy of IMB-05 and IMB-15 in activating PPARα/γ was approximately 30% of that observed with Wy14643 and rosiglitazone. These data indicate that the two thiophene derivatives are novel class of partial PPARα/γ dual agonists, which may be the mechanism underlying their regulatory effects on glucose homeostasis.