197 results on '"KO NAKAMURA"'
Search Results
2. SNEWPY: A Data Pipeline from Supernova Simulations to Neutrino Signals
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Amanda L. Baxter, Segev BenZvi, Joahan Castaneda Jaimes, Alexis Coleiro, Marta Colomer Molla, Damien Dornic, Tomer Goldhagen, Anne Graf, Spencer Griswold, Alec Habig, Remington Hill, Shunsaku Horiuchi, James P. Kneller, Rafael F. Lang, Massimiliano Lincetto, Jost Migenda, Ko Nakamura, Evan O’Connor, Andrew Renshaw, Kate Scholberg, Christopher Tunnell, Navya Uberoi, Arkin Worlikar, and The SNEWS Collaboration
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Supernova neutrinos ,Particle astrophysics ,Supernovae ,Astrophysics ,QB460-466 - Abstract
Current neutrino detectors will observe hundreds to thousands of neutrinos from Galactic supernovae, and future detectors will increase this yield by an order of magnitude or more. With such a data set comes the potential for a huge increase in our understanding of the explosions of massive stars, nuclear physics under extreme conditions, and the properties of the neutrino. However, there is currently a large gap between supernova simulations and the corresponding signals in neutrino detectors, which will make any comparison between theory and observation very difficult. SNEWPY is an open-source software package that bridges this gap. The SNEWPY code can interface with supernova simulation data to generate from the model either a time series of neutrino spectral fluences at Earth, or the total time-integrated spectral fluence. Data from several hundred simulations of core-collapse, thermonuclear, and pair-instability supernovae is included in the package. This output may then be used by an event generator such as sntools or an event rate calculator such as the SuperNova Observatories with General Long Baseline Experiment Simulator (SNOwGLoBES). Additional routines in the SNEWPY package automate the processing of the generated data through the SNOwGLoBES software and collate its output into the observable channels of each detector. In this paper we describe the contents of the package, the physics behind SNEWPY, the organization of the code, and provide examples of how to make use of its capabilities.
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- 2022
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- View/download PDF
3. A configuration of model predictive PID control
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Ko NAKAMURA and Tohru KAWABE
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mpc (model predictive control) ,pid control ,heat conduction system ,mobile robot ,Mechanical engineering and machinery ,TJ1-1570 ,Engineering machinery, tools, and implements ,TA213-215 - Abstract
Although PID control is still widely used in the industry, it isn't answered a high performance demand. On the other hand, the model predictive control (MPC) is paid attention as effective control but it takes much cost to introduce MPC instead of the PID control since the MPC structure quite different from the PID control. To defeat such situation, this paper proposes a model predictive PID Control method. In this method, the PID control gains are derived by solving the constrained optimization problem based on MPC algorithm without using inverse matrixes. The numerical simulations show that the proposed method is effective for various control systems.
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- 2016
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4. A new electrode structure of IrOx/Bi-doped SrRuO3 for highly reliable La-doped Pb (Zr, Ti)O3-based ferroelectric memories.
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Wensheng Wang, Takashi Eshita, Kazuaki Takai, Ko Nakamura, Mitsuaki Oikawa, Nozomi Sato, Soichiro Ozawa, Kouichi Nagai, Satoru Mihara, Yukinobu Hikosaka, Hitoshi Saito, Manabu Kojima, Kenji Nomura, and Hideshi Yamaguchi
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ELECTRODES ,FERROELECTRICITY ,LANTHANUM ,ENERGY consumption ,IRIDIUM - Abstract
We successfully developed a lanthanum (La)-doped Pb (Zr,Ti)O
3 (PLZT) based ferroelectric capacitor (FC) using a new electrode material of bismuth (Bi) doped SrRuO3 (B-SRO) aiming at reduction of energy consumption of ferroelectric random access memory (FeRAM) by suppressing the leakage current of its FC. Our employed B-SRO layer is effective for suppressing the leakage current due to reducing atomic interdiffusions of Iridium and lead between IrOx top electrode (TE) and PLZT. Space charge limited conduction (SCLC) is dominant in the leakage current of the FC with B-SRO, while defect assisted conduction possibly includes in the leakage current of FC without B-SRO in addition with the SCLC. Switchable polarization, depending on the B-SRO thickness, has largest value for 1.0-1.5 nm thick B-SRO. Excellent imprint and switching (fatigue) endurances is proven on the FC with 1 nm thick BSRO. [ABSTRACT FROM AUTHOR]- Published
- 2024
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5. Low Operating Voltage, Improved Breakdown Tolerance, and High Endurance in Hf0.5Zr0.5O2 Ferroelectric Capacitors Achieved by Thickness Scaling Down to 4 nm for Embedded Ferroelectric Memory
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Kasidit Toprasertpong, Kento Tahara, Yukinobu Hikosaka, Ko Nakamura, Hitoshi Saito, Mitsuru Takenaka, and Shinichi Takagi
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General Materials Science - Published
- 2022
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6. Optimal Time Point for Evaluation of Response to Pembrolizumab Treatment in Japanese Patients With Metastatic Urothelial Carcinoma
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TERUO INAMOTO, RYO SATO, YUTO MATSUSHITA, TAIZO UCHIMOTO, KO NAKAMURA, KAZUMASA KOMURA, KAZUKI NISHIMURA, YUSUKE YANO, KYOSUKE NISHIO, SHOKO KINOSHITA, TATSUO FUKUSHIMA, TOMOHISA MATSUNAGA, KEITA NAKAMORI, TAKESHI TSUTSUMI, TAKUYA TSUJINO, HIROFUMI UEHARA, KIYOSHI TAKAHARA, HIDEAKI MIYAKE, and HARUHITO AZUMA
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Research Article - Abstract
Background/Aim: The duration of pembrolizumab use in actual daily practice might be shorter than that in clinical trials because termination of pembrolizumab therapy is at the discretion of the physician. We retrospectively reviewed the response to pembrolizumab in Japanese patients with metastatic urothelial carcinoma (mUC) in relation to the time to response (TTR). Patients and Methods: The records of 165 patients treated with pembrolizumab for mUC were retrospectively analyzed. Response was evaluated at 2, 4, 6 and 8 months. TTR along with time to best response were analyzed. Phase II-III clinical trials were also reviewed to compare the TTR and time to best overall response. Results: The median patient age was 70 years. The objective response rate in the total cohort was 27.1% (42 out of 155 patients). Median TTR was 2.4 months and the time to best response was 3.1 months. Radiological evaluation at each time point significantly predicted overall survival (OS). Considering the evaluation of response at 2, 4, 6 and 8 months, the response at later time points tended to predict OS better. Multivariate analysis showed that the evaluation of response at 8 months (hazard ratio=1.91, 95% confidence interval=1.16-3.16 months; p
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- 2023
7. A new electrode structure of IrOx/Bi-doped SrRuO3 for highly reliable La-doped Pb (Zr, Ti)O3-based ferroelectric memories
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Wensheng Wang, Kazuaki Takai, Ko Nakamura, Mitsuaki Oikawa, Soichiro Ozawa, Kouichi Nagai, Satoru Mihara, Yukinobu Hikosaka, Hitoshi Saito, Manabu Kojima, Takashi Eshita, Kenji Nomura, and Hideshi Yamaguchi
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- 2023
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8. Tissue Distribution of Cisplatin by Intra-arterial Infusion Route in Comparison to Systemic Route: Implication to Therapy for Node-positive Bladder Cancer
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ATSUSHI ICHIHASI, TERUO INAMOTO, TAIZO UCHIMOTO, KO NAKAMURA, KAZUMASA KOMURA, YUSUKE YANO, KAZUKI NISHIMURA, SHOKO KINOSHITA, KYOSUKE NISHIO, TATSUO FUKUSHIMA, KEITA NAKAMORI, TOMOHISA MATSUNAGA, TAKESHI TSUTSUMI, TAKUYA TSUJINO, HIROFUMI UEHARA, KIYOSHI TAKAHARA, KAZUHIRO YAMAMOTO, RYUJI KATO, YOSHIO IJIRI, TETSUYA HAYASHI, and HARUHITO AZUMA
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Pharmacology ,Cancer Research ,General Biochemistry, Genetics and Molecular Biology ,Research Article - Abstract
Background/Aim: In clinical practice, platinum-based systemic chemotherapy works to shrink pelvic lymph nodes. Intra-arterial (IA) bolus infusion may result in more favorable results than systemic chemotherapy. In the present study, we investigated the distribution of cisplatin administrated by IA infusion in varying organs, specifically focusing on the node tissue, in comparison with the intra-venous (IV) route. Materials and Methods: Under anesthesia, cisplatin 0.42 mg/body was administrated by IA or IV infusion in rats to mimic a balloon-occluded arterial infusion model used in clinical practice. The kidney, bladder, lymphatic tissue, and peripheral blood were extracted to analyze the amount of cisplatin by inductively coupled plasma-mass spectrometry. Results: Concertation of cisplatin by IA infusion was higher than that by the IV route in the peripheral blood and kidney. IA infusion led to a significantly high concentration of cisplatin in the bladder compared to IV infusion (1.3±0.452 vs. 0.2 ppb/mg ± 0.055, p=0.050). Furthermore, the IA method led to an extremely high concentration of cisplatin in the lymphatic tissue compared to the IV method (0.1±0.036 vs. 13.3±5.36, p=0.048). Conclusion: High cisplatin accumulation in the lymphatic tissue and bladder by IA administration may have a potential role for treating patients with node-positive bladder cancer.
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- 2023
9. Re-challenging chemotherapy after pembrolizumab in platinum-refractory urothelial carcinoma
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Taizo Uchimoto, Tatsuo Fukushima, Kazumasa Komura, Wataru Fukuokaya, Takahiro Adachi, Takeshi Hashimoto, Atsuhiko Yoshizawa, Ko Nakamura, Yusuke Yano, Kazuki Nishimura, Kyosuke Nishio, Keita Nakamori, Kosuke Iwatani, Shutaro Yamamoto, Fumihiko Urabe, Keiichiro Mori, Takafumi Yanagisawa, Shunsuke Tsuduki, Kiyoshi Takahara, Teruo Inamoto, Jun Miki, Takahiro Kimura, Yoshio Ohno, Ryoichi Shiroki, Shin Egawa, and Haruhito Azuma
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Urology - Abstract
To assess the real-world clinical benefit of re-challenging chemotherapy after pembrolizumab in patients with metastatic urothelial carcinoma (mUC), as there have been several reports suggesting that programmed cell death protein-1/programmed death-ligand 1inhibitors can restore platinum sensitivity.Of 236 patients treated with pembrolizumab, we excluded 45 patients who did not experience progressive disease (PD) for pembrolizumab during the follow-up and 86 patients who discontinued pembrolizumab by the diagnosis of PD followed by the best supportive care. A total of 105 patients were identified for a logistic regression propensity score model to compare the survival outcomes between patients treated with continuing pembrolizumab (80) and re-challenging chemotherapy (25) after the diagnosis of PD for pembrolizumab.A median overall survival (OS) from PD for pembrolizumab was 11 months in 105 patients. Of 25 patients treated with re-challenging chemotherapy, platinum-including chemotherapy (gemcitabine and cisplatin; gemcitabine/cisplatin/paclitaxel [GCP]; methotrexate and vinblastine and adriamycin and cisplatin; and methotrexate and carboplatin and vinblastine MCAVI) was offered in 20 patients (80%). The objective response rate (ORR) for the first-line chemotherapy in the 105 patients was 30%, with a comparable ORR in 25 patients treated with re-challenging chemotherapy of 28%. GCP as a re-challenging regimen was offered in 12 of 25 (48%) patients. The ORR for the GCP regimen was 50%. Propensity score matching was performed using putative clinical factors, from which 34 patients were identified as pair-matched groups. The OS for patients treated with re-challenging chemotherapy was significantly longer than continuing pembrolizumab (a median of 13.9 and 5.8 months, respectively: P = 0.048).Re-challenging chemotherapy including platinum agents after PD with pembrolizumab offers clinical benefits in patients with mUC.
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- 2022
10. Three-dimensional simulation of a core-collapse supernova for a binary star progenitor of SN 1987A
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Ko Nakamura, Tomoya Takiwaki, and Kei Kotake
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High Energy Astrophysical Phenomena (astro-ph.HE) ,Space and Planetary Science ,Astrophysics::High Energy Astrophysical Phenomena ,FOS: Physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,Astronomy and Astrophysics ,Astrophysics - High Energy Astrophysical Phenomena ,Astrophysics::Galaxy Astrophysics - Abstract
We present results from a self-consistent, non-rotating core-collapse supernova simulation in three spatial dimensions using a binary evolution progenitor model of SN 1987A by Urushibata et al. (2018). This 18.3 solar-mass progenitor model is evolved from a slow-merger of 14 and 8 solar-mass stars, and it satisfies most of the observational constraints such as red-to-blue evolution, lifetime, total mass and position in the Hertzsprung-Russell diagram at collapse, and chemical anomalies. Our simulation is initiated from a spherically symmetric collapse and mapped to the three-dimensional coordinates at 10 ms after bounce to follow the non-spherical hydrodynamics evolution. We obtain the neutrino-driven shock revival for this progenitor at 350 ms after bounce, leading to the formation of a newly-born neutron star with average gravitational mass of 1.35 solar mass and spin period of 0.1 s. We also discuss the detectability of gravitational wave and neutrino signals for a Galactic event with the same characteristics as SN 1987A. At our final simulation time (660 ms postbounce), the diagnostic explosion energy, though still growing, is smaller (0.15 foe) compared to the observed value (1.5 foe). The 56Ni mass obtained from the simulation (0.01 solar mass) is also smaller than the reported mass from SN 1987A (0.07 solar mass). Long-term simulation including several missing physical ingredients in our 3D models such as rotation, magnetic fields, or more elaborate neutrino opacity should be done to bridge the gap between the theoretical predictions and the observed values., 14 pages, 14 figures, accepted for publication in MNRAS
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- 2022
11. Astrophysical Journal
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Amanda L. Baxter, Segev BenZvi, Joahan Castaneda Jaimes, Alexis Coleiro, Marta Colomer Molla, Damien Dornic, Tomer Goldhagen, Anne Graf, Spencer Griswold, Alec Habig, Remington Hill, Shunsaku Horiuchi, James P. Kneller, Rafael F. Lang, Massimiliano Lincetto, Jost Migenda, Ko Nakamura, Evan O’Connor, Andrew Renshaw, Kate Scholberg, Christopher Tunnell, Navya Uberoi, Arkin Worlikar, AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Centre de Physique des Particules de Marseille (CPPM), Aix Marseille Université (AMU)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), SNEWS, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPC), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)
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stars ,Nuclear Theory ,[PHYS.NUCL]Physics [physics]/Nuclear Theory [nucl-th] ,Physics::Instrumentation and Detectors ,supernova: collapse ,Astrophysics::High Energy Astrophysical Phenomena ,FOS: Physical sciences ,gap ,programming ,Nuclear Theory (nucl-th) ,High Energy Physics - Phenomenology (hep-ph) ,neutrino: spectrum ,nuclear physics ,supernova ,[PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det] ,Instrumentation and Methods for Astrophysics (astro-ph.IM) ,Monte Carlo ,Solar and Stellar Astrophysics (astro-ph.SR) ,High Energy Astrophysical Phenomena (astro-ph.HE) ,bursts ,r-process ,neutrinos ,Astronomy and Astrophysics ,matter ,astronomy ,observatory ,star: massive ,High Energy Physics - Phenomenology ,neutrino: detector ,collapse ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,[PHYS.HPHE]Physics [physics]/High Energy Physics - Phenomenology [hep-ph] ,oscillations ,spectral ,interface ,neutrino: current ,galaxy ,astropy ,Astrophysics - Instrumentation and Methods for Astrophysics ,Astrophysics - High Energy Astrophysical Phenomena ,[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] - Abstract
Current neutrino detectors will observe hundreds to thousands of neutrinos from a Galactic supernovae, and future detectors will increase this yield by an order of magnitude or more. With such a data set comes the potential for a huge increase in our understanding of the explosions of massive stars, nuclear physics under extreme conditions, and the properties of the neutrino. However, there is currently a large gap between supernova simulations and the corresponding signals in neutrino detectors, which will make any comparison between theory and observation very difficult. SNEWPY is an open-source software package which bridges this gap. The SNEWPY code can interface with supernova simulation data to generate from the model either a time series of neutrino spectral fluences at Earth, or the total time-integrated spectral fluence. Data from several hundred simulations of core-collapse, thermonuclear, and pair-instability supernovae is included in the package. This output may then be used by an event generator such as sntools or an event rate calculator such as SNOwGLoBES. Additional routines in the SNEWPY package automate the processing of the generated data through the SNOwGLoBES software and collate its output into the observable channels of each detector. In this paper we describe the contents of the package, the physics behind SNEWPY, the organization of the code, and provide examples of how to make use of its capabilities., Comment: Software available at https://github.com/SNEWS2/snewpy
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- 2021
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12. A study on the flicker motion after effect caused by v-movement
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Ko Nakamura
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- 2019
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13. An improvement of low temperature characteristics of an La-doped Pb(Zr,Ti)O3 capacitor
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Wensheng Wang, Takashi Eshita, Kazuaki Takai, Kenji Nomura, Hideshi Yamaguchi, Ko Nakamura, Soichiro Ozawa, Kouichi Nagai, Junichi Watanabe, Satoru Mihara, Yukinobu Hikosaka, Hitoshi Saito, and Manabu Kojima
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Physics and Astronomy (miscellaneous) ,General Engineering ,General Physics and Astronomy - Abstract
We developed a lanthanum-doped Pb(Zr0.4,Ti0.6)O3 (PLZT)-based ferroelectric capacitor (FE) aiming at low-voltage operation of ferroelectric random access memory at low temperatures down to −45 °C. High-temperature sputter-deposited IrO x (1 < x < 2) or HT-IrO x was employed as a top electrode (TE) instead of room-temperature (RT) deposited IrO x or RT-IrO x over two PLZT stacked layers. We observed that polarization characteristics drastically improved even at −45 °C by employing HT-IrO x and thinning PLZT, even though leakage current was increased by about one order of magnitude. Transmission electron microscopy observations showed that HT-IrO x has a columnar-like crystalline structure while RT-IrO x has a granular-like crystalline structure. Secondary ion mass spectroscopy indicated that Pb diffusion from PLZT into TE was suppressed by HT-IrO x , which is considered to cause the improvement of polarization characteristics.
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- 2022
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14. Prognostic value of the fluctuation in the neutrophil–lymphocyte ratio at 6 weeks of pembrolizumab treatment is specific to the clinical response in metastatic urothelial carcinoma
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Taizo Uchimoto, Ko Nakamura, Kazumasa Komura, Wataru Fukuokaya, Yusuke Yano, Kazuki Nishimura, Shoko Kinoshita, Kyosuke Nishio, Tatsuo Fukushima, Keita Nakamori, Tomohisa Matsunaga, Takeshi Tsutsumi, Takuya Tsujino, Kohei Taniguchi, Tomohito Tanaka, Hirofumi Uehara, Kiyoshi Takahara, Teruo Inamoto, Takahiro Kimura, Shin Egawa, and Haruhito Azuma
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Carcinoma, Transitional Cell ,Urinary Bladder Neoplasms ,Oncology ,Neutrophils ,Urology ,Humans ,Lymphocytes ,Antibodies, Monoclonal, Humanized ,Prognosis ,Aged ,Retrospective Studies - Abstract
Most patients with metastatic urothelial carcinoma experience no objective response to pembrolizumab and have poor overall survival (OS). Here, we investigated the prognostic value of fluctuation in the neutrophil-lymphocyte ratio (NLR) at 6 weeks of pembrolizumab treatment, focusing on its association with the achievement of objective response.The clinical records of 177 metastatic urothelial carcinoma patients treated with pembrolizumab were retrospectively analyzed.The median age was 72 years, and the median OS was 14 months. The objective response rate in the total cohort was 26.5% (47 of 177 patients). Multivariable analysis showed that objective response achievement (hazard ratio 0.3 [95% confidence interval 0.15-0.59], P0.001) and decline in NLR from that at baseline at 6 weeks of treatment (0.54 [0.34-0.88], P = 0.013) were independent prognostic factors for improved OS. For 47 (26.5%) patients who achieved an objective response, OS was similar regardless of NLR fluctuation at 6 weeks of treatment (P = 0.723). Intriguingly, of the 130 (73.5%) patients with no objective response, those who showed a decreased NLR at 6 weeks of pembrolizumab treatment (57 patients) from that at baseline had significantly longer OS than those with elevated NLR (73 patients) (14 vs. 6 months, P = 0.007).The fluctuation in NLR from that at baseline at 6 weeks of pembrolizumab treatment may be useful for patients without an objective response. This could potentially aid decision-making for post pembrolizumab therapies.
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- 2022
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15. Three-dimensional Hydrodynamics Simulations of Precollapse Shell Burning in the Si- and O-rich Layers
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Tomoya Takiwaki, Hideyuki Umeda, Takashi Yoshida, Kei Kotake, Ko Nakamura, and Koh Takahashi
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Convection ,010504 meteorology & atmospheric sciences ,Astrophysics::High Energy Astrophysical Phenomena ,Scalar (mathematics) ,FOS: Physical sciences ,01 natural sciences ,symbols.namesake ,0103 physical sciences ,Gravitational collapse ,Astrophysics::Solar and Stellar Astrophysics ,010303 astronomy & astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,Mixing (physics) ,Astrophysics::Galaxy Astrophysics ,0105 earth and related environmental sciences ,High Energy Astrophysical Phenomena (astro-ph.HE) ,Physics ,Spherical harmonics ,Astronomy and Astrophysics ,Computational physics ,Stars ,Supernova ,Astrophysics - Solar and Stellar Astrophysics ,Mach number ,Space and Planetary Science ,symbols ,Astrophysics - High Energy Astrophysical Phenomena - Abstract
We present 3D hydrodynamics simulations of shell burning in two progenitors with zero-age main-sequence masses of 22 and 27 $M_{\odot}$ for $\sim$65 and 200 s up to the onset of gravitational collapse, respectively. The 22 and 27 $M_{\odot}$ stars are selected from a suite of 1D progenitors. The former and the latter have an extended Si- and O-rich layer with a width of $\sim$10$^9$ cm and $\sim$5$\times 10^9$ cm, respectively. Our 3D results show that turbulent mixing occurs in both of the progenitors with the angle-averaged turbulent Mach number exceeding $\sim$0.1 at the maximum. We observe that an episodic burning of O and Ne, which takes place underneath the convection bases, enhances the turbulent mixing in the 22 and 27 $M_\odot$ models, respectively. The distribution of nucleosynthetic yields is significantly different from that in 1D simulations, namely, in 3D more homogeneous and inhomogeneous in the radial and angular direction, respectively. By performing a spectrum analysis, we investigate the growth of turbulence and its role of material mixing in the convective layers. We also present a scalar spherical harmonics mode analysis of the turbulent Mach number. This analytical formula would be helpful for supernova modelers to implement the precollapse perturbations in core-collapse supernova simulations. Based on the results, we discuss implications for the possible onset of the perturbation-aided neutrino-driven supernova explosion., 23 pages, 26 figures, 5 tables. Accepted for publication in Astrophys. J
- Published
- 2021
16. A three-dimensional hydrodynamics simulation of oxygen-shell burning in the final evolution of a fast-rotating massive star
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Takashi Yoshida, Kei Kotake, Koh Takahashi, David R. Aguilera-Dena, Ko Nakamura, Norbert Langer, Hideyuki Umeda, and Tomoya Takiwaki
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Physics ,High Energy Astrophysical Phenomena (astro-ph.HE) ,Spiral galaxy ,010308 nuclear & particles physics ,Metallicity ,Shell (structure) ,Implosion ,FOS: Physical sciences ,Astronomy and Astrophysics ,Angular velocity ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,01 natural sciences ,Specific relative angular momentum ,Stars ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics - High Energy Astrophysical Phenomena ,010303 astronomy & astrophysics ,Stellar evolution ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics::Galaxy Astrophysics - Abstract
We perform for the first time a 3D hydrodynamics simulation of the evolution of the last minutes pre-collapse of the oxygen shell of a fast-rotating massive star. This star has an initial mass of 38 M$_\odot$, a metallicity of $\sim$1/50 Z$_\odot$, an initial rotational velocity of 600 km s$^{-1}$, and experiences chemically homogeneous evolution. It has a silicon- and oxygen-rich (Si/O) convective layer at (4.7-17)$\times 10^{8}$ cm, where oxygen-shell burning takes place. The power spectrum analysis of the turbulent velocity indicates the dominance of the large-scale mode ($\ell \sim 3$), which has also been seen in non-rotating stars that have a wide Si/O layer. Spiral arm structures of density and silicon-enriched material produced by oxygen-shell burning appear in the equatorial plane of the Si/O shell. Non-axisymmetric, large-scale ($m \le 3$) modes are dominant in these structures. The spiral arm structures have not been identified in previous non-rotating 3D pre-supernova models. Governed by such a convection pattern, the angle-averaged specific angular momentum becomes constant in the Si/O convective layer, which is not considered in spherically symmetrical stellar evolution models. Such spiral arms and constant specific angular momentum might affect the ensuing explosion or implosion of the star., 6 pages, 6 figures, accepted for publication in MNRAS Letters
- Published
- 2021
17. Neutrino Process in Core-collapse Supernovae with Neutrino Self-interaction and MSW Effects
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Ko Nakamura, Heamin Ko, Toshitaka Kajino, Grant J. Mathews, Masa-aki Hashimoto, Eunja Ha, Ken'ichi Nomoto, Motohiko Kusakabe, Hirokazu Sasaki, Alexey Tolstov, Satoshi Chiba, Toshihiko Kawano, Myung-Ki Cheoun, Masaomi Ono, Takehito Hayakawa, and M. D. Usang
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Physics ,Light nucleus ,010504 meteorology & atmospheric sciences ,Isotope ,Collapse (topology) ,Astronomy and Astrophysics ,Astrophysics ,01 natural sciences ,Spectral line ,Core (optical fiber) ,Supernova ,Space and Planetary Science ,Abundance (ecology) ,0103 physical sciences ,Neutrino ,010303 astronomy & astrophysics ,0105 earth and related environmental sciences - Abstract
We calculate the abundances of 7Li, 11B, 92Nb, 98Tc, 138La, and 180Ta produced by neutrino (ν)-induced reactions in a core-collapse supernova explosion. We consider the modification by ν self-interaction (ν-SI) near the neutrinosphere and the Mikheyev–Smirnov–Wolfenstein (MSW) effect in the outer layers based on time-dependent neutrino energy spectra. Abundances of 7Li and the heavy isotopes 92Nb, 98Tc, and 138La are reduced by a factor of 1.5–2.0 by the ν-SI. In contrast, 11B is relatively insensitive to the ν-SI. We find that the abundance ratio of heavy to light nuclei, 138La/11B, is sensitive to the neutrino mass hierarchy, and the normal mass hierarchy is more likely to be consistent with the solar meteoritic abundances.
- Published
- 2020
18. Ferroelectric capacitor with an asymmetric double-layer PLZT structure for FRAM
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Wensheng Wang, Ko Nakamura, Takashi Eshita, Kenji Nomura, Kazuaki Takai, Hideshi Yamaguchi, Satoru Mihara, Yukinobu Hikosaka, Hitoshi Saito, and Manabu Kojima
- Subjects
Physics and Astronomy (miscellaneous) - Abstract
We developed a lanthanum-doped Pb(Zr0.4,Ti0.6)O3 (PLZT)-based ferroelectric capacitor for low-voltage operation of ferroelectric memory for use in edge devices in the internet of things. The structure, consisting of PLZT stacked layers 30 and 90 nm thick, showed drastically improved performance in three main measures: low leakage current, high saturation polarization, and low saturation voltage. Secondary ion mass spectroscopy indicated that atomic interdiffusion between PLZT and IrOx in the top electrode (TE) was suppressed by the 30 nm thick PLZT, which plays the role of a diffusion barrier, producing a low leakage current and high saturation polarization. The higher oxygen atomic density of the PLZT near the TE interface lowers the oxygen vacancy, which should also suppress the leakage current and the P–V hysteresis shift (imprint). The large grain size and high crystalline quality of PLZT near the TE interface in the PLZT structure provide a high saturation polarization with low leakage current.
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- 2022
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19. Three-dimensional supernova simulation of SN 1987A progenitor with implications for multi-messenger signals
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Ko Nakamura
- Abstract
Recently a new progenitor model for SN 1987A has been constructed. This progenitor model is based on a slow-merger of 14 M⊙ and 9 M⊙ stars and it satisfies most of the observational constraints such as red-toblue evolution, lifetime, total mass and position in the Hertzsprung-Russell diagram at collapse, and chemical anomalies. We perform a three-dimensional self-consistent core-collapse supernova simulation using this new progenitor model and find that it successfully presents an explosion and leaves a 1.53 M⊙ neutron star. Assuming a detector sensitivity of Kamiokande-II and the distance to the supernova of 51 kpc, we obtain 16 neutrino detection events in one second. Some characteristic modes in its gravitational wave signal are also discussed in this article.
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- 2022
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20. Efficacy of pembrolizumab and comprehensive CD274/PD-L1 profiles in patients previously treated with chemoradiation therapy as radical treatment in bladder cancer
- Author
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Kazuki Nishimura, Kyosuke Nishio, Kensuke Hirosuna, Kazumasa Komura, Takuo Hayashi, Wataru Fukuokaya, Ayako Ura, Taizo Uchimoto, Ko Nakamura, Tatsuo Fukushima, Yusuke Yano, Nobushige Takahashi, Keita Nakamori, Shoko Kinoshita, Tomohisa Matsunaga, Takeshi Tsutsumi, Takuya Tsujino, Kohei Taniguchi, Tomohito Tanaka, Hirofumi Uehara, Kiyoshi Takahara, Teruo Inamoto, Yoshinobu Hirose, Takahiro Kimura, Shin Egawa, and Haruhito Azuma
- Subjects
Male ,Pharmacology ,Cancer Research ,genetic structures ,Immunology ,Neoplasms. Tumors. Oncology. Including cancer and carcinogens ,Chemoradiotherapy ,Middle Aged ,Antibodies, Monoclonal, Humanized ,Survival Analysis ,B7-H1 Antigen ,Antineoplastic Agents, Immunological ,Urinary Bladder Neoplasms ,Oncology ,Humans ,Molecular Medicine ,Immunology and Allergy ,Female ,RC254-282 ,Aged ,Retrospective Studies - Abstract
BackgroundChemoradiation therapy (CRT) has been increasingly reported as a possible alternative to total cystectomy (TC) for localized bladder cancer (BC). Pembrolizumab is the standard of care for platinum-refractory metastatic urothelial carcinoma, although it is unknown whether the efficacy of pembrolizumab in patients previously treated with curative CRT varies from the results of benchmark trials.MethodsWe retrospectively assessed whether the survival benefit of pembrolizumab differs between patients previously treated with TC or CRT as radical treatment. A total of 212 patient records were collected for a logistic regression propensity score model. An independent dataset with next-generation sequencing (n=289) and PD-L1 Combined Positive Score (CPS: n=266) was analyzed to assess whether CRT-recurrent tumor harbors distinct CD274/PD-L1 profiles.ResultsPropensity score matching was performed using putative clinical factors, from which 30 patients in each arm were identified as pair-matched groups. There was no significant difference in overall survival from the initiation of pembrolizumab (p=0.80) and objective response rate (p=0.59) between CRT and TC treatment groups. In the independent 289 BC cohort, 22 samples (7.6%) were collected as CRT-recurrent tumors. There was no significant difference in CD274 mRNA expression level between CRT-naïve and CRT-recurrent tumors. The compositions of CD274 isoforms were comparable among all isoforms detected from RNAseq between CRT-naïve (n=267) and CRT-recurrent (n=22) tumors. No actionable exonic mutation in CD274 was detected in CRT-recurrent tumors. PD-L1 CPS was positively correlated with CD274 mRNA expression level, and PD-L1 CPS was comparable between CRT-naïve and CRT-recurrent tumors.ConclusionsThe efficacy of pembrolizumab for patients previously treated with CRT was similar to those treated with TC. The enhanced tumor regression by combining programmed cell death protein 1/PD-L1 inhibitor and CRT might be expected only in the concurrent administration.
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- 2022
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21. Three-dimensional hydrodynamics simulations of shell burning in Si/O-rich layer of pre-collapse massive stars
- Author
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Takashi Yoshida, Tomoya Takiwaki, Kei Kotake, Koh Takahashi, Ko Nakamura, Hideyuki Umeda, David R. Aguilera-Dena, and Norbert Langer
- Abstract
We perform three-dimensional (3D)hydrodynamics simulations of shell burning in the silicon-and oxygen-rich layers in pre-collapse massive stars.Weadoptanon-rotating27 M⊙ starhaving anextended O/Si/Ne layer and afast-rotating 38 M⊙ star having a Si/Olayer, that has experienced chemically homogeneousevolution. Both pre-collapse stars showlarge-scale turbulent motion with a maximum Mach number of ~0.1 in the convective layers activated byneonand oxygenshellburning.The radialproflieoftheangle-averaged mass fraction distributioninO/Si/Ne layer is more homogeneous in the 3D simulation compared to the 1D evolution for the 27 M⊙ star. The angle-averaged specific angular momentum in the Si/O layer of the fast-rotating 38 M⊙ star tends to become roughly constant in the convective layer of the 3D simulation, which is not considered in the 1D evolution.
- Published
- 2022
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22. An investigation of Apparent Motion based on Feature Captured Motion illusion
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Ko Nakamura
- Subjects
Feature (computer vision) ,Computer science ,business.industry ,media_common.quotation_subject ,Illusion ,Computer vision ,Artificial intelligence ,business ,Motion (physics) ,media_common - Published
- 2018
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23. Evaluation for Effect of Transient Electromagnetic Fields on Processing inside ICs based on Observation of Timing Violation
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Yu-ichi Hayashi and Ko Nakamura
- Subjects
Electromagnetic field ,Physics ,Acoustics ,Transient (oscillation) ,Electrical and Electronic Engineering - Published
- 2018
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24. Core-collapse simulation of SN 1987A binary progenitor and its multimessenger signals
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Ko Nakamura
- Subjects
History ,Astrophysics::High Energy Astrophysical Phenomena ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics::Galaxy Astrophysics ,Computer Science Applications ,Education - Abstract
We perform a three-dimensional self-consistent core-collapse supernova simulation using a binary evolution progenitor model of SN 1987A. This progenitor model is based on a slow-merger of 14 M∹ and 9 M∹ stars and it satisfies most of the observational constraints such as red-to-blue evolution, lifetime, total mass and position in the Hertzsprung-Russell diagram at collapse, and chemical anomalies. We find that this progenitor model successfully present explosion and leave a 1.53 M∹ neutron star with a kick velocity of 70kms−1 and a spin period of 0.1 s. Assuming a detector sensitivity of Kamiokande-II and the distance to the supernova of 51 kpc, we obtain 16 neutrino detection events in one second. Some characteristic modes in its gravitational wave signal are also discussed in this article.
- Published
- 2021
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25. Information Leakage Threats for Cryptographic Devices Using IEMI and EM Emission
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Hideaki Sone, Ko Nakamura, Takaaki Mizuki, and Yu-ichi Hayashi
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Computer science ,microprocessor chips ,intentional electromagnetic interference (IEMI) ,EM leakage ,Encryption ,Cryptography ,Hardware_PERFORMANCEANDRELIABILITY ,02 engineering and technology ,injection timing estimation method ,Electromagnetic interference ,Transient analysis ,fault analysis method ,intentional electromagnetic interference ,0202 electrical engineering, electronic engineering, information engineering ,Electronic engineering ,characteristic fluctuation detection ,realistic secret information analysis method ,Fault analysis ,Timing ,Electrical and Electronic Engineering ,fault-injection timing ,Leakage (electronics) ,Clocks ,cryptography ,Differential fault analysis ,information leakage threat ,business.industry ,fault analysis ,Circuit faults ,020206 networking & telecommunications ,Fault injection ,fault diagnosis ,Condensed Matter Physics ,on-chip fault-injection circuit ,cryptographic devices ,electromagnetic interference ,Atomic and Molecular Physics, and Optics ,IEMI ,Information leakage ,secret key analysis ,Electromagnetic (EM) information leakage ,business ,Estimation - Abstract
In this paper, we present a new information leakage threat combining intentional electromagnetic interference (IEMI) and observations of EM leakage. In previous studies, the analysis of secret key information in cryptographic modules using fault injection has led to methods whereby faults can be injected via low-voltage IEMI. However, the timing of fault injections cannot be controlled with this approach, and it is difficult to obtain faulty ciphertexts for use in secret key analysis by differential fault analysis (DFA). To overcome this problem, we propose a method for estimating the fault-injection timing by detecting characteristic fluctuations in the EM leakage from the device. As a result, it may be possible to implement a realistic secret information analysis method applicable to a wide range of devices. First, to show the feasibility of the proposed method, we describe an experiment using an on-chip fault-injection circuit that can control the injection timing. Furthermore, we apply a fault analysis method that combines the injection timing estimation method and fault injection by IEMI in a practical experimental environment. We select useful faulty ciphertexts using the proposed method, and then perform secret key analysis by DFA. Experimental results demonstrate that the secret key can be successfully analyzed.
- Published
- 2017
26. Introduction of Feature Captured Motion illusion: The interpretation and its verification by some experimental observation
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Ko Nakamura
- Subjects
business.industry ,Computer science ,Feature (computer vision) ,media_common.quotation_subject ,Illusion ,Computer vision ,Artificial intelligence ,business ,Motion (physics) ,media_common ,Interpretation (model theory) - Published
- 2017
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27. モデル予測型PID制御の一構成
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Ko Nakamura and Tohru Kawabe
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050210 logistics & transportation ,0209 industrial biotechnology ,020901 industrial engineering & automation ,Control theory ,Computer science ,0502 economics and business ,05 social sciences ,PID controller ,02 engineering and technology ,GeneralLiterature_MISCELLANEOUS - Abstract
Although PID control is still widely used in the industry, it isn't answered a high performance demand. On the other hand, the model predictive control (MPC) is paid attention as effective control but it takes much cost to introduce MPC instead of the PID control since the MPC structure quite different from the PID control. To defeat such situation, this paper proposes a model predictive PID Control method. In this method, the PID control gains are derived by solving the constrained optimization problem based on MPC algorithm without using inverse matrixes. The numerical simulations show that the proposed method is effective for various control systems.
- Published
- 2017
28. The Changing Structure of International Law on Marine Living Resources
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Ko Nakamura
- Subjects
Structure (mathematical logic) ,business.industry ,Political science ,International trade ,International law ,business - Published
- 2019
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29. Long-term Simulations of Multi-Dimensional Core-collapse Supernovae: Implications for Neutron Star Kicks
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Ko Nakamura, Tomoya Takiwaki, and Kei Kotake
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Physics ,High Energy Astrophysical Phenomena (astro-ph.HE) ,Star (game theory) ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Luminosity ,Supernova ,Stars ,Neutron star ,Space and Planetary Science ,Neutrino ,Ejecta ,Astrophysics - High Energy Astrophysical Phenomena ,Energy (signal processing) - Abstract
Core-collapse supernovae (CCSNe) are the final stage of massive stars, marking the birth of neutron stars (NSs). The aspherical mass ejection drives a natal kick of the forming NS. In this work we study the properties of the NS kick based on our long-term hydrodynamics CCSN simulations. We perform two-dimensional (2D) simulations for ten progenitors from a 10.8 to 20 $\, M_{\odot}$ star covering a wide range of the progenitor's compactness parameter, and two three-dimensional (3D) simulations for an 11.2 $\, M_{\odot}$ star. Our 2D models present a variety of explosion energies between $\sim 1.3 \times 10^{50}$ erg and $\sim 1.2 \times 10^{51}$ erg, and NS kick velocities between $\sim 100$ km s$^{-1}$ and $\sim 1500$ km s$^{-1}$. For the 2D exploding models, we find that the kick velocities tend to become higher with the progenitor's compactness. This is because the high progenitor compactness results in high neutrino luminosity from the proto-neutron star (PNS), leading to more energetic explosions. Since high-compactness progenitors produce massive PNSs, we point out that the NS masses and the kick velocities can be correlated, which is moderately supported by observation. Comparing 2D and 3D models of the 11.2 $\, M_{\odot}$ star, the diagnostic explosion energy in 3D is, as previously identified, higher than that in 2D, whereas the 3D model results in a smaller asymmetry in the ejecta distribution and a smaller kick velocity than in 2D. Our results confirm the importance of self-consistent CCSN modeling covering a long-term postbounce evolution in 3D for a quantitative prediction of the NS kicks., 13 pages, 10 figures, accepted for publication in PASJ
- Published
- 2019
30. One-, Two-, and Three-dimensional Simulations of Oxygen Shell Burning Just Before the Core-Collapse of Massive Stars
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Tomoya Takiwaki, Hideyuki Umeda, Takashi Yoshida, Koh Takahashi, Kei Kotake, and Ko Nakamura
- Subjects
Convection ,Physics ,High Energy Astrophysical Phenomena (astro-ph.HE) ,010504 meteorology & atmospheric sciences ,Turbulence ,FOS: Physical sciences ,Astronomy and Astrophysics ,01 natural sciences ,Computational physics ,symbols.namesake ,Stars ,Supernova ,Mach number ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,0103 physical sciences ,symbols ,Astrophysics::Solar and Stellar Astrophysics ,Neutrino ,Astrophysics - High Energy Astrophysical Phenomena ,010303 astronomy & astrophysics ,Stellar evolution ,Event (particle physics) ,Solar and Stellar Astrophysics (astro-ph.SR) ,0105 earth and related environmental sciences - Abstract
We perform two- (2D) and three-dimensional (3D) hydrodynamics simulations of convective oxygen shell-burning that takes place deep inside a massive progenitor star of a core-collapse supernova. Using one dimensional (1D) stellar evolution code, we first calculate the evolution of massive stars with an initial mass of 9-40 $M_\odot$. Four different overshoot parameters are applied, and CO core mass trend similar to previous works is obtained in the 1D models. Selecting eleven 1D models that have a silicon and oxygen coexisting layer, we perform 2D hydrodynamics simulations of the evolution $\sim$100 s until the onset of core-collapse. We find that convection with large-scale eddies and the turbulent Mach number $\sim$0.1 is obtained in the models having a Si/O layer with a scale of 10$^8$ cm, whereas most models that have an extended O/Si layer up to a few $\times 10^9$ cm exhibit lower turbulent velocity. Our results indicate that the supernova progenitors that possess a thick Si/O layer could provide a preferable condition for perturbation-aided explosions. We perform 3D simulation of a 25 $M_\odot$ model, which exhibits large-scale convection in the 2D models. The 3D model develops large ($\ell = 2$) convection similar to the 2D model, however, the turbulent velocity is lower. By estimating the neutrino emission properties of the 3D model, we point out that a time modulation of the event rates, if observed in KamLAND and Hyper-Kamiokande, would provide an important information about structural changes in the presupernova convective layer., Comment: 25 pages, 17 figures, 2 tables. Accepted for publication in ApJ
- Published
- 2019
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31. THE STUDY OF THE ARCHITECTURAL STYLE OF “SOAN” TEA HOUSE THROUGH THE MULTIVARIATE ANALYSES OF THE PHYSICAL QUANTITATIVE DATA OF ELEMENTS
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Yuta Ito, Ko Nakamura, and Kengo Kuma
- Subjects
Engineering ,Multivariate analysis ,Anthropology ,business.industry ,business ,Composition (language) ,Architectural style - Published
- 2016
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32. Short-Lived Radioisotope Tc98 Synthesized by the Supernova Neutrino Process
- Author
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Satoshi Chiba, M. D. Usang, Masa-aki Hashimoto, Ko Nakamura, Toshitaka Kajino, Toshihiko Kawano, Myung-Ki Cheoun, Alexey Tolstov, Masaomi Ono, Ken'ichi Nomoto, Motohiko Kusakabe, Grant J. Mathews, Heamin Ko, and Takehito Hayakawa
- Subjects
Physics ,010308 nuclear & particles physics ,Duration time ,General Physics and Astronomy ,Electron ,01 natural sciences ,Nuclear physics ,Supernova ,Nucleosynthesis ,0103 physical sciences ,Electron temperature ,Production (computer science) ,Neutrino ,010303 astronomy & astrophysics ,Charged current - Abstract
The isotope $^{98}\mathrm{Tc}$ decays to $^{98}\mathrm{Ru}$ with a half-life of $4.2\ifmmode\times\else\texttimes\fi{}{10}^{6}\text{ }\text{ }\text{ }\mathrm{yr}$ and could have been present in the early Solar System. In this Letter, we report on the first calculations of the production of $^{98}\mathrm{Tc}$ by neutrino-induced reactions in core-collapse supernovae (the $\ensuremath{\nu}$ process). Our predicted $^{98}\mathrm{Tc}$ abundance at the time of solar system formation is not much lower than the current measured upper limit raising the possibility for its detection in the not too distant future. We show that, if the initial abundance were to be precisely measured, the $^{98}\mathrm{Tc}$ nuclear cosmochronometer could be used to evaluate a much more precise value of the duration time from the last core-collapse supernova to the formation of the solar system. Moreover, a unique and novel feature of the $^{98}\mathrm{Tc}$ $\ensuremath{\nu}$-process nucleosynthesis is the large contribution ($\ensuremath{\sim}20%$) from charged current reactions with electron antineutrinos. This means that $^{98}\mathrm{Tc}$ becomes a unique new $\ensuremath{\nu}$-process probe of the temperature of the electron antineutrinos.
- Published
- 2018
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33. Neutrino process with primitive meteorites and high power laser
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Tatsufumi Nakamura, M. D. Usang, Hideyuki Kotaki, K. Nomoto, Alexey Tolstov, T. Kajino, Ko Nakamura, Masaki Kando, Heamin Ko, Myung-Ki Cheoun, T. Hayakawa, M. Hashimoto, Motohiko Kusakabe, Shuntaro Chiba, Grant J. Mathews, and M. Ono
- Subjects
Physics ,Isotope ,Astrophysics::High Energy Astrophysical Phenomena ,Nuclear Theory ,High Energy Physics::Phenomenology ,Nuclear physics ,Supernova ,Stars ,Stellar nucleosynthesis ,Photodisintegration ,Excited state ,High Energy Physics::Experiment ,Nuclide ,Neutrino ,Nuclear Experiment - Abstract
A huge number of neutrinos emitted in core-collapse supernova explosions (ν process) play an important role in stellar nucleosynthesis of some rare nuclides. The study of the neutrino process can contribute to estimation of neutrino energy spectra and explosion mechanism. In the mass region heavier than iron, only three nuclides are known as the neutrino isotopes. If we can find other candidates for neutrino production, it helps to constrain precisely the neutrino energy spectra emitted from proto-neutron stars. A key input for the calculation of the neutrino process is destruction rates by photodisintegration reactions on excited nuclei at high temperature environments. We have proposed direct measurements of photon-induced reaction cross sections on nuclei excited by high power laser to simulate stellar environments.
- Published
- 2018
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34. Impact of Neutrino Opacities on Core-Collapse Supernova Simulations
- Author
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Tobias Fischer, Kei Kotake, Gabriel Martínez-Pinedo, Tomoya Takiwaki, and Ko Nakamura
- Subjects
Physics ,High Energy Astrophysical Phenomena (astro-ph.HE) ,Opacity ,010308 nuclear & particles physics ,Isotropy ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Type II supernova ,01 natural sciences ,Set (abstract data type) ,Supernova ,Space and Planetary Science ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,Neutrino ,Diffusion (business) ,Astrophysics - High Energy Astrophysical Phenomena ,010303 astronomy & astrophysics - Abstract
Accurate description of neutrino opacities is central both to the core-collapse supernova (CCSN) phenomenon and to the validity of the explosion mechanism itself. In this work, we study in a systematic fashion the role of a variety of well-selected neutrino opacities in CCSN simulations where multi-energy, three-flavor neutrino transport is solved by the isotropic diffusion source approximation (IDSA) scheme. To verify our code, we first present results from one-dimensional (1D) simulations following core-collapse, bounce, and up to ~ 250 ms postbounce of a 15 $M_{\odot}$ star using a standard set of neutrino opacities by Bruenn (1985). Detailed comparison with published results supports the reliability of our three-flavor IDSA scheme using the standard opacity set. We then investigate in 1D simulations how the individual opacity update leads to the difference from the base-line run with the standard opacity set. By making a detailed comparison with previous work, we check the validity of our implementation of each update in a step-by-step manner. Individual neutrino opacities with the largest impact on the overall evolution in 1D simulations are selected for a systematic comparison in our two-dimensional (2D) simulations. Special emphasis is devoted to the criterion of explodability in the 2D models. We discuss the implications of these results as well as the limitations and requirements for future towards more elaborate CCSN modeling., Comment: 47 pages, 19 figures, accepted for publication in ApJ
- Published
- 2018
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35. The effect of social anxiety for perceiving the walking direction of point-light-walkers
- Author
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Ko Nakamura
- Subjects
Point light ,Social anxiety ,Psychology ,Social psychology - Published
- 2015
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36. Recent Status of Multi-Dimensional Core-Collapse Supernova Models
- Author
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Kei Kotake, Tomoya Takiwaki, and Ko Nakamura
- Subjects
Physics ,Space and Planetary Science ,Astrophysics::High Energy Astrophysical Phenomena ,Multi dimensional ,Astronomy ,Astronomy and Astrophysics ,Type II supernova - Abstract
We report a recent status of multi-dimensional neutrino-radiation hydrodynamics simulations for clarifying the explosion mechanism of core-collapse supernovae (CCSNe). In this contribution, we present two results, one from two-dimensional (2D) simulations using multiple progenitor models and another from three-dimensional (3D) rotational core-collapse simulation using a single progenitor. From the first ever systematic 2D simulations, it is shown that the compactness parameter ξ that characterizes the structure of the progenitors is a key to diagnose the explodability of neutrino-driven explosions. In the 3D rotating model, we find a new type of rotation-assisted explosion, which makes the explosion energy bigger than that in the non-rotating model. The unique feature has not been captured in previous 2D self-consistent rotational models because the growth of non-axisymmetric instabilities is the key to foster the explosion by enhancing the energy transport from the proto-neutron star to the gain region.
- Published
- 2015
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37. THE STUDY OF THE ARCHITECTURAL STYLE OF TEA HOUSE BY THE MULTIVARIATE ANALYSIS USING THE DATA OF THE PRESENCE OR ABSENCE OF ELEMENTS
- Author
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Kengo Kuma, Ko Nakamura, and Yuta Ito
- Subjects
Multivariate analysis ,Geography ,Statistics ,Composition (language) ,Architectural style - Published
- 2015
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38. A METHOD TO DISCRIMINATE OCCLUDING EDGES RELATED TO SPATIAL DIVISION
- Author
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Kaoru Yamaoka, Ko Nakamura, and Kengo Kuma
- Subjects
Computer science ,business.industry ,Computer vision ,Artificial intelligence ,Division (mathematics) ,business - Published
- 2015
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39. Neutrino-driven supernova explosions powered by nuclear reactions
- Author
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T. Takiwaki, K. Kotake, N. Nishimura, and Ko Nakamura
- Subjects
Shock wave ,Physics ,Nuclear reaction ,SIMPLE (dark matter experiment) ,Astrophysics::High Energy Astrophysical Phenomena ,Astronomy and Astrophysics ,Astrophysics ,Type II supernova ,Luminosity ,Nuclear physics ,Supernova ,Space and Planetary Science ,Nucleosynthesis ,Neutrino ,Nuclear Experiment - Abstract
We have investigated the revival of a shock wave by nuclear burning reactions at the central region of core-collapse supernovae. For this purpose, we performed hydrodynamic simulations of core collapse and bounce for 15 M⊙ progenitor model, using ZEUS-MP code in axi-symmetric coordinates. Our numerical code is equipped with a simple nuclear reaction network including 13 α nuclei form 4He to 56Ni, and accounting for energy feedback from nuclear reactions as well as neutrino heating and cooling. We found that the energy released by nuclear reactions is significantly helpful in accelerating shock waves and is able to produce energetic explosion even if the input neutrino luminosity is low.
- Published
- 2017
40. Gravitational Wave Emission from Long-Term Self-Consistent Two-dimensional Core-Collapse Supernova Models
- Author
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Kei Kotake, Ko Nakamura, and Eishin Ikeda
- Subjects
Physics ,Gravitational wave ,Gravitational collapse ,Astronomy ,Astrophysics ,Self consistent ,Type II supernova ,Gravitational redshift ,Gravitational energy ,Term (time) - Published
- 2017
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41. Nucleosynthesis in 2D Core-Collapse Supernova Long-Term Simulations of 11.2 and 17.0 \(\text{M}_{ \odot }\) Progenitors
- Author
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Tomoya Takiwaki, Ko Nakamura, Rubén M. Cabezón, Matthias Hempel, Friedrich-Karl Thielemann, Marius Eichler, Kei Kotake, Takami Kuroda, Matthias Liebendörfer, Kubono, S., Kajino, T., Nishimura, S., Isobe, T., Nagataki, S., Shima, T., and Takeda, Y.
- Subjects
Physics ,Supernova ,Accretion (meteorology) ,Nucleosynthesis ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Star (graph theory) ,Type II supernova ,Astrophysics::Galaxy Astrophysics ,Term (time) - Abstract
We perform detailed nucleosynthesis calculations for two long-term, 2D simulations of core-collapse supernovae. We find that elements are produced up to Ru (Z = 44) and observe abundance patterns that are characteristic of a νp-process. One important characteristic of the long-term simulation is that there is still accretion of matter onto the proto-neutron star and unbinding of matter in some other regions at the time when the simulations stop (around 7s). Dividing the tracer particles into different bins according to their peak temperatures enables us to study and compare the nuclear compositions of these bins for the different simulations.
- Published
- 2017
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42. Diffuse Supernova Neutrino Background from extensive core-collapse simulations of $8$-$100 {\rm M}_\odot$ progenitors
- Author
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Tobias Fischer, Kei Kotake, Alexander Summa, Hans-Thomas Janka, Ko Nakamura, Shunsaku Horiuchi, Tomoya Takiwaki, and Kohsuke Sumiyoshi
- Subjects
Physics ,High Energy Astrophysical Phenomena (astro-ph.HE) ,010308 nuclear & particles physics ,Astrophysics::High Energy Astrophysical Phenomena ,Collapse (topology) ,Astronomy ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,01 natural sciences ,Core (optical fiber) ,Black hole ,Stars ,Neutron star ,Supernova ,Space and Planetary Science ,0103 physical sciences ,Gravitational collapse ,Astrophysics::Solar and Stellar Astrophysics ,Neutrino ,Astrophysics - High Energy Astrophysical Phenomena ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics - Abstract
We revisit the diffuse supernova neutrino background in light of recent systematic studies of stellar core collapse that reveal the quantitative impacts of the progenitor conditions on the collapse process. In general, the dependence of the progenitor on the core-collapse neutrino emission is not monotonic in progenitor initial mass, but we show that it can, at first order, be characterized by the core compactness. For the first time, we incorporate the detailed variations in the neutrino emission over the entire mass range $8$-$100 {\rm M}_\odot$, based on (i) a long-term simulation of the core collapse of a $8.8 {\rm M}_\odot$ O-Ne-Mg core progenitor, (ii) over 100 simulations of iron core collapse to neutron stars, and (iii) half a dozen simulations of core collapse to black holes (the "failed channel"). The fraction of massive stars that undergo the failed channel remains uncertain, but in view of recent simulations which reveal high compactness to be conducive to collapse to black holes, we characterize the failed fraction by considering a threshold compactness above which massive stars collapse to black holes and below which the final remnant is a neutron star. We predict that future detections of the diffuse supernova neutrino background may have the power to reveal this threshold compactness, if its value is relatively small as suggested by interpretations of several recent astronomical observations., Comment: 14 pages, 8 figures, accepted for publication in MNRAS
- Published
- 2017
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43. Systematic Features and Progenitor Dependence of Core-Collapse Supernovae
- Author
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Kei Kotake, Takami Kuroda, Tomoya Takiwaki, Ko Nakamura, Kubono, S., Kajino, T., Nishimura, S., Isobe, T., Nagataki, S., Shima, T., and Takeda, Y.
- Subjects
Physics ,Core (optical fiber) ,Supernova ,Astrophysics::High Energy Astrophysical Phenomena ,Collapse (topology) ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics::Galaxy Astrophysics - Abstract
We present our latest results of two-dimensional core-collapse supernova simulations for about 400 progenitors. Our self-consistent supernova models reveal the systematic features of core-collapse supernova properties such as neutrino luminosity and energy spectrum, explosion energy, remnant mass, and yield of radioactive 56Ni. We find that these explosion characteristics tend to show a monotonic increase as a function of mass accretion rate onto a shock. The accretion rate depends on the structure of the progenitor core and its envelope, which is well described by the compactness parameter.
- Published
- 2017
44. IDENTIFICATION OF STREET AFFORDANCES BY EVALUATING STREET ELEMENTS IN SHANGHAI
- Author
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Kengo Kuma, Ko Nakamura, and Yao Chen
- Subjects
World Wide Web ,Identification (information) ,Geography ,Advertising ,Affordance - Published
- 2014
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45. Reconstruction of IrO2/(Pb, La)(Zr, Ti)O3 (PLZT) interface by optimization of postdeposition annealing and sputtering conditions
- Author
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Ko Nakamura, Kazuaki Takai, Hideshi Yamaguchi, Takashi Eshita, Satoru Mihara, Manabu Kojima, Hitoshi Saito, Yuji Kataoka, Soichiro Ozawa, Yukinobu Hikosaka, Kenji Nomura, and Wensheng Wang
- Subjects
010302 applied physics ,Materials science ,Annealing (metallurgy) ,Ferroelectric ceramics ,Nucleation ,Analytical chemistry ,General Physics and Astronomy ,02 engineering and technology ,Coercivity ,Sputter deposition ,021001 nanoscience & nanotechnology ,Lead zirconate titanate ,01 natural sciences ,Ferroelectricity ,chemistry.chemical_compound ,chemistry ,Sputtering ,0103 physical sciences ,0210 nano-technology - Abstract
We reconstruct the interface between ferroelectric (FE) lanthanum-doped lead zirconate titanate (PLZT) and an iridium oxide (IrOx) top electrode (TE), taking advantage of the interdiffusion of Ir and Pb during postdeposition annealing. The tetragonal perovskite phase with a low c/a axis ratio at the IrOx/PLZT interface is observed by X-ray diffraction. It is suggested that the low c/a axis ratio in the interfacial layer is due to the effect of diffusion of Ir from the TE-IrOx. It is also considered that the low c/a axis ratio interfacial layer functions as a nucleation layer for reversal of polarization, thereby achieving a low coercive electric field. The formation of the interfacial layer is very sensitive to the O2 content of the Ar/O2 atmosphere during TE-IrOx deposition. Although an optimized Ar/O2 ratio achieves excellent polarization characteristics (high polarization value and low coercive field), the optimum Ar/O2 region is very narrow at around 36% O2. In other Ar/O2 regions, a pyrochlore phase is formed at the interface owing to interdiffusion of the TE and FE films, and polarization characteristics deteriorate.
- Published
- 2019
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46. THREE-DIMENSIONAL SIMULATION OF A ROTATING CORE-COLLAPSE SUPERNOVA
- Author
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Kei Kotake, Takami Kuroda, Ko Nakamura, and Tomoya Takiwaki
- Subjects
Physics ,Neutron star ,Supernova ,Angular momentum ,Three dimensional simulation ,Astrophysics::High Energy Astrophysical Phenomena ,Perpendicular ,Polar ,General Medicine ,Astrophysics ,Neutrino ,Type II supernova - Abstract
Multi-dimensionality in the inner working of core-collapse supernovae has long been considered one of the most important ingredients to understand the explosion mechanism. We perform a series of numerical experiments to explore how rotation impacts the 3-dimensional hydrodynamics of core-collapse supernova. We employ a light-bulb scheme to trigger explosions and a three-species neutrino leakage scheme to treat deleptonization eects and neutrino losses from the neutron star interior. We nd that the rotation can help the onset of neutrino-driven explosions for models in which the initial angular momentum is matched to that obtained from recent stellar evolutionary calculations ( 0:3 - 3 rad s 1 at the center). For models with larger initial angular momenta, a shock surface deforms to be oblate due to larger centrifugal force. This makes a gain region, in which matter gains energy from neutrinos, more concentrated around the equatorial plane. As a result, the preferred direction of the explosion in 3-dimensional rotating models is perpendicular to the spin axis, which is in sharp contrast to the polar explosions around the axis that are often obtained from 2-dimensional simulations.
- Published
- 2015
- Full Text
- View/download PDF
47. Circular Polarizations of Gravitational Waves from Core-Collapse Supernovae: A Clear Indication of Rapid Rotation
- Author
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Ko Nakamura, Shoichi Yamada, Kazuhiro Hayama, and Takami Kuroda
- Subjects
High Energy Astrophysical Phenomena (astro-ph.HE) ,Physics ,Rotation period ,Gravitational wave ,Astrophysics::High Energy Astrophysical Phenomena ,FOS: Physical sciences ,General Physics and Astronomy ,Astronomy ,General Relativity and Quantum Cosmology (gr-qc) ,Astrophysics ,01 natural sciences ,General Relativity and Quantum Cosmology ,Galaxy ,Accretion (astrophysics) ,Supernova ,0103 physical sciences ,Astrophysics - High Energy Astrophysical Phenomena ,010306 general physics ,010303 astronomy & astrophysics ,Rapid rotation ,Circular polarization - Abstract
We propose to employ the circular polarization of gravitational waves emitted by core-collapse supernovae as an unequivocal indication of rapid rotation deep in their cores. It has been demonstrated by three dimensional simulations that non-axisymmetric accretion flows may develop spontaneously via hydrodynamical instabilities in the post-bounce cores. It is not surprising then that the gravitational waves emitted by such fluid motions are circularly polarized. We show in this letter that a network of the second generation detectors of gravitational waves worldwide may be able to detect such polarizations up to the opposite side of Galaxy as long as the rotation period is shorter than a few seconds prior to collapse., 5 pages, 3 figures
- Published
- 2016
- Full Text
- View/download PDF
48. A STUDY ON THE SYSTEM OF HAWKER'S ASSEMBLY AND SPONTANEOUS MARKET FORCE FROM MALAYSIA'S COFFEESHOP AND SINGAPORE'S HAWKER CENTRE
- Author
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Nobuaki Furuya and Ko Nakamura
- Subjects
Engineering ,Coffee shop ,business.industry ,Advertising ,business - Abstract
The Coffee Shop called Kopi Tiam in Malaysia is an interesting system of eating house as assembly of hawkers. The independent hawkers with each special meal are assembled by the shop's owner, and the owner provides drink stall and tables for eat. It is similar to Hawker Centre in Singapore or modern food court, but It seems to became a spontaneous system to sustain the quality of foods. The Coffee Shop in Malaysia is analyzed by compared with Hawker Centre in Singapore to clarify the system and know a type of the plan.
- Published
- 2011
- Full Text
- View/download PDF
49. A Derivation Method for System Design Model of a Heat Conduction Plant
- Author
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Ko Nakamura and Tohru Kawabe
- Subjects
Computer science ,Control theory ,Systems design ,Derivation method ,Thermal conduction ,Delay time - Published
- 2011
- Full Text
- View/download PDF
50. Ferroelectric random access memory with high electric properties and high production yield realized by employing an AlOx underlying layer of Pt bottom electrode for a La-doped lead zirconate titanate capacitor
- Author
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Hideshi Yamaguchi, Kenji Nomura, Yukinobu Hikosaka, Takashi Eshita, Soichiro Ozawa, Hitoshi Saito, Yuji Kataoka, Manabu Kojima, Kazuaki Takai, Wensheng Wang, Ko Nakamura, Junichi Watanabe, and Satoru Mihara
- Subjects
010302 applied physics ,Materials science ,Physics and Astronomy (miscellaneous) ,business.industry ,Doping ,General Engineering ,General Physics and Astronomy ,Lead zirconate titanate ,01 natural sciences ,Ferroelectricity ,law.invention ,chemistry.chemical_compound ,Capacitor ,chemistry ,law ,0103 physical sciences ,Electrode ,Surface roughness ,Optoelectronics ,business ,Polarization (electrochemistry) ,Layer (electronics) - Abstract
Although ferroelectric random access memory (FRAM) has superior electric properties, its downside is that it has a relatively larger cell area in comparison other non-volatile memories. We tried to apply TiOx, and AlOx to an underlying layer (TiOx-UL, AlOx-UL) instead of our previously used Ti underlying layer (Ti-UL) for the La-doped lead zirconate titanate (PLZT) capacitor to obtain a high polarization value aiming to a lowering cell area. The failed bit ratio of the FRAM with TiOx-UL was found to be higher than that with AlOx-UL even though polarization values of the PLZT capacitor with both underlying layers are almost the same and much higher than that with Ti-UL. It is strongly suggested that the imprint induced in PLZT by charged defect is a main cause of bit failure by fail-bit analysis. X-ray diffraction and atomic force microscopy observations shows that charged defect density in PLZT over TiOx-UL is possibly higher than that in PLZT over AlOx-UL due to surface roughness of underlying layers.
- Published
- 2018
- Full Text
- View/download PDF
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