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Relation between interdiffusion and polarity for MBE growth of GaN epilayers on ZnO substrates
Takuma Suzuki,Chihiro Harada,Hiroki Goto,Tsutomu Minegishi,Agus Setiawan,고항주,Meoung-Whan Cho,T.Yao 한국물리학회 2004 Current Applied Physics Vol.4 No.6
We report on GaN growth on Zn-polar ZnO substrates using plasma-assisted molecular-beam epitaxy (P-MBE). Before GaNgrowth, ZnO substrate annealing conditions were optimized. Reection high-energy electron diraction (RHEED) patterns afterlow-temperature GaN buer layer annealing changed from streaky to spotty, suggesting that zinc and oxygen atoms interdiusefrom the ZnO substrate into the GaN epilayer. This interdiusion results in a mix-polar GaN epilayer.
Clinical outcomes of permanent stenting with endoscopic ultrasound gallbladder drainage
Eisuke Suzuki,Yuji Fujita,Kunihiro Hosono,Yuji Koyama,Seitaro Tsujino,Takuma Teratani,Atsushi Nakajima,Nobuyuki Matsuhashi 대한소화기내시경학회 2023 Clinical Endoscopy Vol.56 No.5
Background/Aims: Endoscopic ultrasound gallbladder drainage (EUS-GBD) is gaining attention as a treatment method for cholecystitis. However, only a few studies have assessed the outcomes of permanent stenting with EUS-GBD. Therefore, we evaluated the clinicaloutcomes of permanent stenting using EUS-GBD. Methods: This was a retrospective, single-center cohort study. The criteria for EUS-GBD at our institution are a high risk for surgery,inability to perform surgery owing to poor performance status, and inability to obtain consent for emergency surgery. EUS-GBD wasperformed using a 7-Fr double-pigtail plastic stent with a dilating device. The primary outcomes were the recurrence-free rate of cholecystitisand the late-stage complication-avoidance rate. Secondary outcomes were technical success, clinical success, and procedural adverseevents. Results: A total of 41 patients were included in the analysis. The median follow-up period was 168 (range, 10–1,238) days. The recurrence-free and late-stage complication-avoidance rates during the follow-up period were 95% (38 cases) and 90% (36 cases), respectively. There were only two cases of cholecystitis recurrence during the study period. Conclusions: EUS-GBD using double-pigtail plastic stent was safe and effective with few complications, even in the long term, in patientswith acute cholecystitis.
Stress dependence on N/Ga ratio in GaN epitaxial films grownon ZnO substrates
Tsutomu Minegishi,Takuma Suzuki,Chihiro Harada,Hiroki Goto,Meoung-Whan Cho,Takafumi Yao 한국물리학회 2004 Current Applied Physics Vol.4 No.6
GaN films were grown on ZnO substrate under various beam equivalent pressure ratios by plasma-assisted molecular beamepitaxy (P-MBE). We theoretically calculated the thermal stress caused by the dierence of thermal expansion coecients betweenGaN and ZnO. The changes of stress and critical thickness were evaluated by measurement of XRD for HT GaN and LT GaNbuer grown under Ga-rich and N-rich conditions. From this study, we observed that GaN grown under Ga-rich condition causesGaN lm to under compressive-stress, while GaN grown under N-rich condition was tensile-stressed. Consequently, interdiusionhas no eect on the variation of the critical thickness.
Development and Evaluation of Avionics for System Identification of Small UAVs
Masaru Naruoka,Takuma Hino,Ryota Nakagawa,Takeshi Tsuchiya,Shinji Suzuki 한국항공우주학회 2008 한국항공우주학회 학술발표회 논문집 Vol.- No.-
A new avionics tor system identification of small unmanned aerial vehicles (UAVs) is proposed in this paper. The proposed avionics consists of three parts: 1) MEMS INS/GPS navigation unit, 2) air data sensor, and 3) command logger. The accuracy and error models of the components are obtained experimentally with a prototype device, and the total performance is evaluated with Monte Carlo simulations which solve the longitudinal stability derivatives of a small UAV with the obtained error model. Furthermore, a real flight log obtained by the prototype device is analyzed. The results shows that the proposed avionics is accurate enough 10 analyze the flight characteristic of small UAVs with the system identification techniques.
PROPERTIES OF DUST IN VARIOUS ENVIRONMENTS OF NEARBY GALAXIES
HIDEHIRO KANEDA,Takuma Kokusho,Rika Yamada,DAISUKE ISHIHARA,SHINKI OYABU,TORU KONDO,MITSUYOSHI YAMAGISHI,Akiko Yasuda,TAKASHI ONAKA,Toyoaki Suzuki 한국천문학회 2017 天文學論叢 Vol.32 No.1
We have performed systematic studies of the properties of dust in various environments of nearby galaxies with AKARI. The unique capabilities of AKARI, such as near-infrared (near-IR) spectroscopy combined with all-sky coverage in the mid- and far-IR, enable us to study processing of dust, particularly carbonaceous grains includings polycyclic aromatic hydrocarbons (PAHs), for unbiased samples of nearby galaxies. In this paper, we first review our recent results on individual galaxies, highlighting the uniqueness of AKARI data for studies of nearby galaxies. Then we present results of our systematic studies on nearby starburst and early-type galaxies. From the former study based on the near-IR spectroscopy and mid-IR all-sky survey data, we find that the properties of PAHs change systematically from IR galaxies to ultra-luminous IR galaxies, depending on the IR luminosity of a galaxy or galaxy population. From the latter study based on the mid- and far-IR all-sky survey data, we find that there is a global correlation between the amounts of dust and old stars in early-type galaxies, giving an observational constraint on the origin of the dust.
Bin Guo,Mitsuhisa Ichiyanagi,Takuma Ohashi,Qinyue Zheng,Takashi Suzuki 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.7
Ammonia has received significant attention as a fuel due to its carbon-free molecular structure. However, burning ammonia is challenging because of its low laminar burning velocity. To promote the combustion velocity, the authors propose a constant volume combustion chamber with a sub-chamber. This study investigated the effects of the mixing time and equivalence ratio of the ammonia/oxygen/argon mixture on combustion. The mean velocity of the ejection from the sub-chamber can be calculated by evaluating the combustion pressure, mass fraction burned, and volume fraction burned. It was clarified that with the sub-chamber structure, the ejection from the sub-chamber improved the compression and turbulence of unburned gas in the main chamber and increased the mean flame velocity of ammonia combustion. The appropriate glow plug temperature could improve the ignitability of the fuel mixture, leading to increased combustion efficiency, maximum combustion pressure, and reduced combustion time.
Underwater Acoustic Mavlink Communication for Swarming AUVS
Muller, Yukiko,Oshiro, Shiho,Motohara, Takuma,Kinjo, Atsushi,Suzuki, Taisaku,Wada, Tomohisa International Journal of Computer ScienceNetwork S 2021 International journal of computer science and netw Vol.21 No.4
The objective of this project is to conduct an underwater survey. The primary goal is to develop a device that can achieve the desired output under test conditions. For this reason, certain practical considerations must be taken into account, and the implementation is then developed to be carried out to obtain stable performance with the available hardware based on that experiment. The experiment was performed via BlueROV2 (Remotely Operated Vehicle) using RaspberryPi and softwares such as QGC (QGroundControl) and ArduPilot. This paper explains the work, the results with the collected data and how we implemented the work is presented in the end. The intention of this experiment is to connect two PCs using RaspberryPi with MAVLink communication using a Commercial-Off-The-Shelf device.
Hiroki Goto,Hisao Makino,Agus Setiawan,Takuma Suzuki,Chihiro Harada,Tsutomu Minegishi,Meoung-Whan Cho,Takafumi Yao 한국물리학회 2004 Current Applied Physics Vol.4 No.6
Optical properties of ZnO thin lms with/without MgO-buer annealing were investigated by low and room temperature photoluminescence measurements. The ZnO lms were grown onc-sapphire substrates by plasma-assisted molecular-beam epitaxy employing a thin MgO-buer layer. Dislocation density of ZnO layer was reduced from 5.3· 109 to 1.9· 109 cm. 2 by annealingMgO-buer prior to the growth of ZnO. The intensity of free exciton emission from the sample with MgO-buer annealing wasalmost twice of that from the sample without annealing, while the deep level emission from the sample with MgO-buer annealingwas about 1/3 of that without annealing. The MgO-buer annealing improves optical quality of overgrown ZnO lms.