Akira Iwasaki

Prof. Akira Iwasaki

Department of Aeronautics and Astronautics, The University of Tokyo, 2-8-1 Nishi-Shinjuku, Shinjuku-ku, 163-8001Tokyo, Japan
orcid

Research Focus & Metrics

Academic Career Length

23Years (2004-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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12 August 2011 in IEEE Transactions on Geoscience and Remote Sensing
Verified
Journal Article
Closed access
Naoto YokoyaNaoto Yokoya
Naoto Yokoya
TYTakehisa Yairi
Takehisa Yairi
Akira IwasakiAkira Iwasaki
Akira Iwasaki
Coupled nonnegative matrix factorization (CNMF) unmixing is proposed for the fusion of low-spatial-resolution hyperspectral and high-spatial-resolution multispectral data to produce fused data with high spatial and spectral resolutions. Both hyperspectral and multispectral data are alternately unmixed into end member and abundance matrices by the CNMF algorithm based on a linear spectral mixture model. Sensor observation models that relate the two data are built into the initialization matrix of each NMF unmixing procedure. This algorithm is physically straightforward and easy to implement owing to its simple update rules. Simulations with various image data sets demonstrate that the CNMF algorithm can produce high-quality fused data both in terms of spatial and spectral domains, which contributes to the accurate identification and classification of materials observed at a high spatial resolution.

1 September 2009 in Nature
Verified
Journal Article
Open access
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MOMakiko Ohtake
Makiko Ohtake
TMTsuneo Matsunaga
Tsuneo Matsunaga
JHJunichi Haruyama
Junichi Haruyama
YYYasuhiro Yokota
Yasuhiro Yokota
TMTomokatsu Morota
Tomokatsu Morota
JJJean-Luc Josset
Jean-Luc Josset
It has been thought that the lunar highland crust was formed by the crystallization and floatation of plagioclase from a global magma ocean1,2, although the actual generation mechanisms are still debated2,3. The composition of the lunar highland crust is therefore important for understanding the formation of such a magma ocean and the subsequent evolution of the Moon. The Multiband Imager4 on the Selenological and Engineering Explorer (SELENE)5 has a high spatial resolution of optimized spectral coverage, which should allow a clear view of the composition of the lunar crust. Here we report the global distribution of rocks of high plagioclase abundance (approaching 100 vol.%), using an unambiguous plagioclase absorption band recorded by the SELENE Multiband Imager. If the upper crust indeed consists of nearly 100 vol.% plagioclase, this is significantly higher than previous estimates of 82–92 vol.% (refs 2, 6, 7), providing a valuable constraint on models of lunar magma ocean evolution.

19 September 2017 in IEEE Transactions on Geoscience and Remote Sensing
Verified
Journal Article
Closed access
Junshi XiaJunshi Xia
Junshi Xia
Pedram GhamisiPedram Ghamisi
Pedram Ghamisi
Naoto YokoyaNaoto Yokoya
Naoto Yokoya
Akira IwasakiAkira Iwasaki
Akira Iwasaki
Classification techniques for hyperspectral images based on random forest (RF) ensembles and extended multiextinction profiles (EMEPs) are proposed as a means of improving performance. To this end, five strategies - bagging, boosting, random subspace, rotation-based, and boosted rotation-based - are used to construct the RF ensembles. EPs, which are based on an extrema-oriented connected filtering technique, are applied to the images associated with the first informative components extracted by independent component analysis, leading to a set of EMEPs. The effectiveness of the proposed method is investigated on two benchmark hyperspectral images: the University of Pavia and Indian Pines. Comparative experimental evaluations reveal the superior performance of the proposed methods, especially those employing rotation-based and boosted rotation-based approaches. An additional advantage is that the CPU processing time is acceptable.

12 November 2009 in Geophysical Research Letters
Verified
Journal Article
Closed access
PDF file
JHJunichi Haruyama
Junichi Haruyama
KHKazuyuki Hioki
Kazuyuki Hioki
MSMotomaro Shirao
Motomaro Shirao
TMTomokatsu Morota
Tomokatsu Morota
HHHarald Hiesinger
Harald Hiesinger
CPCarle M. Pieters
Carle M. Pieters

13 February 2009 in Science
Verified
Journal Article
Closed access
PDF file
JHJunichi Haruyama
Junichi Haruyama
MOMakiko Ohtake
Makiko Ohtake
TMTsuneo Matsunaga
Tsuneo Matsunaga
TMTomokatsu Morota
Tomokatsu Morota
CHChikatoshi Honda
Chikatoshi Honda
JJJean-Luc Josset
Jean-Luc Josset
We determined model ages of mare deposits on the farside of the Moon on the basis of the crater frequency distributions in 10-meter-resolution images obtained by the Terrain Camera on SELENE (Selenological and Engineering Explorer) (Kaguya). Most mare volcanism that formed mare deposits on the lunar farside ceased at ∼3.0 billion years ago, suggesting that mare volcanism on the Moon was markedly reduced globally during this period. However, several mare deposits at various locations on the lunar farside also show a much younger age, clustering at ∼2.5 billion years ago. These young ages indicate that mare volcanism on the lunar farside lasted longer than was previously considered and may have occurred episodically.

1 February 2011 in Earth and Planetary Science Letters
Verified
Journal Article
Closed access
TMTomokatsu Morota
Tomokatsu Morota
JHJunichi Haruyama
Junichi Haruyama
MOMakiko Ohtake
Makiko Ohtake
TMTsuneo Matsunaga
Tsuneo Matsunaga
CHChikatoshi Honda
Chikatoshi Honda
HHHarald Hiesinger
Harald Hiesinger