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ESSENTIAL NORMS AND STABILITY CONSTANTS OF WEIGHTED COMPOSITION OPERATORS ON C(X)
Takagi, Hiroyuki,Miura, Takeshi,Takahasi, Sin-Ei Korean Mathematical Society 2003 대한수학회보 Vol.40 No.4
For a weighted composition operator $uC_{\varphi}$ on C(X), we determine its essential norm and the constant for its Hyers-Ulam stability, in terms of the set $\varphi(\{x\;\in\;X\;:\;$\mid$u(x)$\mid$\;\geq\;r\})$ (r > 0).
Essential norms and stability constants of weighted composition
Hiroyuki Takagi,Takeshi Miura,Sin-Ei Takahasi 대한수학회 2003 대한수학회보 Vol.40 No.4
For a weighted composition operator uC_{varphi} on C(X), wedetermine its essential norm and the constant for its Hyers-Ulamstability, in terms of the set varphi ( { x in X : |u(x)| geqr } ) (r > 0).
Takagi, Hiroyuki,Murata, Isao The Korean Association for Radiation Protection 2016 방사선방어학회지 Vol.41 No.2
Background: Industrial X-ray CT system is normally applied to non-destructive testing (NDT) for industrial product made from metal. Furthermore there are some special CT systems, which have an ability to inspect nuclear fuel assemblies or rocket motors, using high power and high energy (more than 6 MeV) pulsed X-ray source. In these case, pulsed X-ray are produced by the electron linear accelerator, and a huge number of photons with a wide energy spectrum are produced within a very short period. Consequently, it is difficult to measure the X-ray energy spectrum for such accelerator-based X-ray sources using simple spectrometry. Due to this difficulty, unexpected images and artifacts which lead to incorrect density information and dimensions of specimens cannot be avoided in CT images. For getting highly precise CT images, it is important to know the precise energy spectrum of emitted X-rays. Materials and Methods: In order to realize it we investigated a new approach utilizing the Bayesian estimation method combined with an attenuation curve measurement using step shaped attenuation material. This method was validated by precise measurement of energy spectrum from a 1 MeV electron accelerator. In this study, to extend the applicable X-ray energy range we tried to measure energy spectra of X-ray sources from 6 and 9 MeV linear accelerators by using the recently developed method. Results and Discussion: In this study, an attenuation curves are measured by using a step-shaped attenuation materials of aluminum and steel individually, and the each X-ray spectrum is reconstructed from the measured attenuation curve by the spectrum type Bayesian estimation method. Conclusion: The obtained result shows good agreement with simulated spectra, and the presently developed technique is adaptable for high energy X-ray source more than 6 MeV.
Cloud mask generation algorithm over the ocean using GMS infrared images
Kuzuhara, Hiroyuki,Omi, Hiroyuki,Takagi, Mikio 대한원격탐사학회 2000 International Symposium on Remote Sensing Vol.16 No.1
Satellite remote sensing data offer the very powerful means to the understanding of global environment. It is, however, important to discriminate between clouds and the sea in oceanography. Therefore, it is required to remove clouds accurately. In this paper, automatic cloud mask generation algorithm over the ocean using GMS infrared images is described, because visible images are not available at night, but infrared images can be used day and night. This algorithm Consists of 4 steps. The maximum brightness temperature data for 5days, which may correspond to the sea surface temperature, has been developed in our laboratory. This sea surface temperature database is used as the reference to determine the threshold for cloud detection, because the sea surface temperature varies widely according to the latitude, current and location. Thick dominant clouds are detected by the temperature difference from this maximum brightness temperature data. The second step is the extraction of thin clouds around detected thick clouds from the brightness temperature difference between IR1 and IR2 channel. The third step is to detect the rest of clouds surrounding the detected clouds, tracing the edge of each cloud with a small window to determine the local threshold adaptively to remove clouds on the boundary. Finally, the region determined as cloud free is searched with a small window to extract isolated clouds. Sometimes, the boundary of warm current and cold current is classified as cloud area by conventional algorithms, but this proposed algorithm has solved this problem with the tracing the edge of cloud mask.
Magnetic Memory in a Ceramic YBCO Superconductor Composed of Sub-micron-size Grains
Hiroyuki Deguchi,Takuya Ashida,Mitsuhiro Syudo,Masaki Mito,Seishi Takagi,Makoto Hagiwara,Kuniyuki Koyama 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.12
The ceramic YBa2Cu4O8 (YBCO) composed of sub-micron-size grains is considered as a randomJosephson-coupled network of 0 and junctions and shows successive phase transitions. The firsttransition occurs inside each grain at Tc1 = 81 K, and the second transition occurs among thegrains at Tc2 = 47 K. A magnetic glass behavior similar to those of spin-glasses is observed attemperatures below Tc2. The memory phenomena are investigated by recording the zero-fieldcooledand thermoremanent magnetizations measured on heating after the cooling process witha halt at Ts = 41 K. Memory effects of the halt are imprinted in the system when the sampleis re-heated. In the case without a field switch at Ts, the influence of the halt is confined to anarrow temperature region near Ts whereas the memory effect of the halt employing a field switchis extended over a wide temperature region below Ts. The results suggest that chiral-glass orderingoccurs at Tc2 in the ceramic YBCO.
Cloud Mask Generation for the Sea Surface Temperature Database Using Infrared GMS Images
OmiI, Hiroyuki,Takagi, Mikio 대한원격탐사학회 2001 International Symposium on Remote Sensing Vol.17 No.1
In this paper, automatic cloud mask generation over the ocean using GMS infrared images and the sea surface temperature (SST) database production with cloud mask are described. The first step is the thick cloud detection using the temperature difference between the maximum brightness temperature data for 5days, which may correspond to SST, and IR1 brightness temperature. In proposed algorithm, the image is divided into small blocks, because GMS observes the earth disk and the sea surface temperature differs widely. according to the latitude, and the threshold is determined automatically at each block. The second step is the thin cloud detection using split window channels. The third step is to detect the edge of cloud mask generated by previous 2 steps. When tracing the edge of detected cloud with a small window is started, in our conventional algorithm, the starting point is the edge of detected cloud, but in proposed algorithm, the starting point is moved at the boundary of thin cloud and the sea. In this step, thin cloud detection accuracy is improved. Finally, isolated clouds are detected. This algorithm prevents to classify the boundary of warm current and cold current as cloud area, and the cloud detection accuracy is improved compared with other algorithm. SST and the composite SST (CSST), which are overlaid with this cloud mask is produced. Since these are applied atmospheric correction (MCSST), in wide area; the accuracy SST can be derived.
Tadayuki Takagi,Mitsuru Sugimoto,Hidemichi Imamura,Yosuke Takahata,Yuki Nakajima,Rei Suzuki,Naoki Konno,Hiroyuki Asama,Yuki Sato,Hiroki Irie,Jun Nakamura,Mika Takasumi,Minami Hashimoto,Tsunetaka Kato 대한소화기내시경학회 2023 Clinical Endoscopy Vol.56 No.1
high tumors. Therefore, sufficient sampling of histological specimens is necessary in cases of unresectable pancreatic cancer (UR-PC). This multicenter study investigated the efficacy of endoscopic ultrasound-guided fine-needle biopsy (EUS-FNB) using a Franseen needlefor MSI evaluation in patients with UR-PC. Methods: A total of 89 patients with UR-PC who underwent endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) orEUS-FNB using 22-G needles at three hospitals in Japan (2018–2021) were enrolled. Fifty-six of these patients (FNB 23 and FNA 33)were followed up or evaluated for MSI. Patient characteristics, UR-PC data, and procedural outcomes were compared between patientswho underwent EUS-FNB and those who underwent EUS-FNA. Results: No significant difference in terms of sufficient tissue acquisition for histology was observed between patients who underwentEUS-FNB and those who underwent EUS-FNA. MSI evaluation was possible significantly more with tissue samples obtained usingEUS-FNB than with tissue samples obtained using EUS-FNA (82.6% [19/23] vs. 45.5% [15/33], respectively; p<0.01). In the multivariateanalysis, EUS-FNB was the only significant factor influencing the possibility of MSI evaluation. Conclusions: EUS-FNB using a Franseen needle is desirable for ensuring sufficient tissue acquisition for MSI evaluation.