CeO2光触媒材料の改良指針と光触媒性能に関する研究

九州工業大学博士学位論文 学位記番号: 工博甲第575号 学位授与年月日: 令和5年3月24日1 Introduction of photocatalysis principle and ceria-based photocatalyst materials|2 Synthesis and mechanism investigation of enhanced photooxidation performance on broomlike (Sm, Y, La and Nd)-doped CeO2 photocatalysts|3 Improving photocatalytic activity of waxberry-like CeO2 via samarium doping and silver quantum dots anchoring|4 Preparation of Y-doped CeO2/PCN heterojunction photocatalyst with promoted photooxidation and photoreduction performance|5 Conclusions and Outlooks九州工業大学令和4年

BBR Performance over Variable Delay Paths on Multipath TCP Video Streaming

Video streaming makes most of Internet traffic nowadays, being transported over Hypertext Transfer Protocol/ Transmission Control Protocol (HTTP/TCP). Being the predominant transport protocol, TCP stack performance in transporting video streams has become paramount, specially with regard to MultiPath Transport Control Protocol (MPTCP) innovation and multiple client device interfaces currently available. An important component of MPTCP is the packet scheduler, which selects on a packet basis the transport path to inject each packet. In this paper, we provide an extensive analysis of the Bottleneck Bandwidth and Round-trip propagation time (BBR) TCP variant when transporting video streams over Long Term Evolution (LTE) and Wi-Fi access networks, comparing its performance to other available congestion control schemes and various path schedulers. We use network performance level, as well as video quality level metrics to characterize multiple path schedulers and the resulting network and application layers. We show that BBR video streaming performance degrades for challenging path delay variation scenarios.The Fifteenth International Conference on Evolving Internet, INTERNET 2023, March 13 - 17, 2023, Barcelona, Spai

BEMS architecture and service modules for online tuning

九州工業大学博士学位論文 学位記番号: 情工博甲第381号 学位授与年月日: 令和5年3月24日第1章 研究背景|第2章|第3章 マイクロサービス方式によるBEMSの開発|第4章 オンラインチューニング機構の実現|第5章 評価|第6章 結論九州工業大学令和4年

A Virtual Prototyping Technique as a Design Method of Next Generation Power Supply and Design Consideration of the Switching Power Supply for Miniaturization using the Proposed Technique

電源の小型化と高効率化を可能にするために，Si based ICとGaNパワーデバイスを3次元に積層した3次元パワーICが注目を集めている．3次元構造にすることで寄生インピーダンスが低減し，ヘテロジニアス構造によりGaNを使用できるため，高周波で高効率動作が可能になる．一方で，電源内部で発生する熱は性能に悪影響を与え，小型化することで電磁界や熱などの物理現象との相互作用がさらに大きくなる．本研究では，3次元パワーICの設計手法として，デバイスシミュレーション，回路シミュレーション，電磁界シミュレーション，熱流体シミュレーーションを組み合わせたVirtual Prototyping方法を提案する．またこれ用いた電源の小型化に向けた設計例を紹介する． / 3D power IC, which integrates Si based IC and Gallium Nitride (GaN) power devices realizes high efficiency at high frequency switching and high-power density. However, miniaturization makes 3D power IC high temperature, and the interaction of electromagnetic field and heat are increased. In this paper, we propose a virtual prototyping technique, which is coupling of thermal-device, heat conduction, thermal-electromagnetic, and thermal-circuit simulation to design the 3D power IC. In addition, we introduce an example of design for miniaturization of power supply using virtual prototyping.電子通信エネルギー技術研究会（EE）, 2023年1月19日 - 20日, 九州工業大

希釈された炭化水素燃料噴霧中を伝播する二相爆轟に対するEulerian-Eulerianモデル

Research on power generation or propulsive devices based on detonation gained interest in the past two decades. Indeed, detonation-based devices, such as rotating detonation engines (RDE) or pulse detonation engines (PDE), may confer a thermal efficiency of gain up to 15 % compared to conventional thermal engines. For this reason, RDE and PDE are studied worldwide, but mostly with gaseous fuel and oxidizer injection. However, under the constraint of practical applications such as engine size limitation, using liquid fuel to increase the energy density is expected. A liquid injection adds complexity to an already challenging problem. Past studies on detonation through multi-phase medium encounter complications such as droplet size effects, partial vaporization, poor fuel/oxidizer mixing, and a complex detonation front structure. Therefore, in order to achieve a stable and reliable liquid detonation engine, it is necessary to understand the mechanism occurring during the detonation process. Those mechanisms are still poorly understood due to the relatively small number of experimental or numerical studies on the subject. This thesis aims to clarify these lacunae by studying the droplet effects on detonation propagation. The analysis is divided into two parts: the first is the validation and investigation of detonation propagation through mono-dispersed and poly-dispersed droplet clouds of n-heptane in a tube. The second part is the numerical analysis of a kerosene/air/hydrogen RDE to evaluate the performance and understand the behavior of the detonation through a multiphase cross-flow injection.九州工業大学博士学位論文 学位記番号：工博甲第554号 学位授与年月日：令和4年9月26日1 Introduction|2 Mathematical modeling|3 Numerical methodology|4 Sub-Models validation|5 Validation of the sampling method for detonation simulation|6 Multi-phase rotating detonation engine|7 Conclusion九州工業大学令和4年

Partial Discharge Phenomena for Advanced Insulation Diagnostics of Oil-Filled Power Transformers

電力用変圧器は，電力システムにおいて主要な機器であり，その安定運用には診断技術が重要である。油入変圧器に対しては油中ガス分析による異常診断が一般的であるが，即応性やオンラインでの状態把握には課題がある。他方，ガス絶縁開閉装置 (GIS) では部分放電 (PD) によるUHF帯 (0.3~3GHz) の放射電磁波を測定するUHF法によるPD診断が普及してきていることから，変圧器でもUHF法による診断が油中ガス分析のように一般化されることが考えられる。UHF法の適用には，PD現象，特に放射電磁波と関係するPD電流の高周波特性の理解と解明が必要であるが，油中でのPD電流の広帯域計測は十分に行われていない。放電物理の観点とともに放射電磁波検出の観点からもPD電流の超広帯域測定が必要である。また，運用中の油入変圧器の絶縁油は温度上昇や経年による劣化，絶縁紙劣化によるフルフラールの生成，流動帯電防止の添加剤含有など，実験室で検討されている室温状態の新油とは異なる状態であり，それらを考慮した検討も必要である。以上のような背景に鑑み，本研究では，電力用油入変圧器の絶縁油として主に用いられる鉱油を対象に，超広帯域計測によりPD電流特性を明らかにするとともに，その放射電磁波特性を検討した。さらに実運用状態を評価できる装置を提案し構築した。以下に本論文の構成と概要を記す。第１章では，序論として，本研究の背景や変圧器の技術開発動向から取り組むべき課題について述べた。第２章では，実験装置および実験方法として，本研究で使用した超広帯域電流パルス波形測定システムの構成や仕様および試験設備等を述べた。第３章では，超広帯域計測による鉱油中電流波形の脱気状態の相違と極性効果について述べた。ガス中では超広帯域計測により負極性電流波形では数オーダの立ち上がり時間を有することなどが明らかにされているが，油中への適用はなく特性は不明であった。絶縁油は十分脱気し清純にしないと溶存しているガスや水分，異物などが絶縁性能に影響するため，超広帯域計測を適用しこれら影響を明確に理解，評価することを考えた。本章では基本となる鉱油を対象に，脱気状態および交流電圧の極性効果による電流波形の基礎特性を調べた。その結果，油中の“真性放電”だけでなく溶存ガスによる“油中ガス放電”が発生していることや電流波形に明確な極性効果があることを明らかにした。第４章では，超広帯域計測による鉱油中電流波形の経年油と新油の相違について述べた。絶縁油は長期運転に伴う経年劣化を考慮する必要がある。そこで，超広帯域計測を適用した新油と経年油での電流波形の相違を検討した。また，絶縁油種類の比較として難燃性のシリコーン油の新油についても併せて比較検討した。さらにUHF帯およびVHF帯に感度を有するアンテナを用いたPD放射電磁波の同期計測も行い，電流との関係を，正準判別分析や多変量解析などの統計解析手法を用いて議論した。その結果，各絶縁油でPD電流波形には顕著な極性効果が認められ，負極性PD電流波形の特徴量を用いて相関関係を比較すると，鉱油とシリコーン油では特性に相違が認められたが，経年油と新油では同一の特性が示された。この結果は，PD放射電磁波の振幅値と負極性PD電流波形の特徴量との関係でも同様に示された。さらに線形正準判別分析を行った結果，経年油と新油およびシリコーン油で相違がある可能性が示唆された一方で，Wilksのlambdaという統計値では有意差があるとはいえないと評価された。経年油と新油の相違有無に関しては，今後さらに測定帯域を拡張した結果による評価が待たれる。第5章では，鉱油中負極性電流の立ち上がり時間特性の電界利用率依存性と通信帯域との関係について述べた。鉱油中の電流パルスの立ち上がり時間を電界利用率を変化させて調べるとともに，それらの放射電磁波の周波数特性と通信で使用される通信帯域との関係を検討した。その結果，鉱油中の電流波形は電界利用率依存性があり利用率が増加するほど立ち上がり時間は増加した。さらに，測定結果に基づき電流波形をガウス波形でモデル化して放射電磁波の周波数特性を検討した結果，鉱油中は通信で使用されるミリ波帯にピークを示す電磁波が放射される可能性があることがわかった。第６章では，変圧器の実運用状態を模擬した試験検討の一例および試験システムの構築結果を示し，また油中放電現象への光学測定の適用結果を示した。実運用状態の変圧器絶縁診断を考えると，実器環境を模擬できる試験系の確立が必要である。また劣悪な電気的ノイズ環境では法による現象の検出が困難となるため，油中放電現象への光学測定の適用も重要である。そこで，実運用状態を模擬した試験条件の一例として，流動帯電防止の観点から鉱油へ添加されるが特性に及ぼす影響を超広帯域計測により検討した。その結果，電流の時間変化や放射電磁波強度に添加は影響がないことを明らかにした。次に油中放電現象への光学測定の適用を検討し，鉱油中放電により発生する炭化水素系分解ガスの発生種や発生タイミングを評価できることが示された。最後に変圧器の実運用状態の絶縁油を模擬できる試験システムを提案・構築した。これにより，実運用状態での絶縁油中現象だけでなく，今後適用される新たな絶縁油の放電特性や診断手法の検討・評価を可能とする装置を提示した。第７章では，総括として本研究で得られた成果をまとめた。九州工業大学博士学位論文 学位記番号: 工博甲第562号 学位授与年月日: 令和5年3月24日第1章 序論|第2章 実験装置および実験方法|第3章 超広帯域計測による鉱油中電流波形の脱気状態の相違と極性効果|第4章 超広帯域計測による鉱油中電流波形の経年油と新油の相違と統計学的手法による波形比較|第5章 鉱油中負極性電流のピコ秒立ち上がり時間特性と帯域との関係|第6章 光学測定技術の適用と実運用状態を模擬できる試験システムの提案|第7章 総括九州工業大学令和4年

イオン注入したPtおよび擬二次元電子ガスベースのヘテロ構造における電流からスピン流への変換現象

Spin Hall effect (SHE), initially predicted by Dyakonov and Perel in 1971 and later revisited by Hirsch in 1999 [1], is the generation of spin current density js from a charge current density jc. The conversion of jc to js via SHE, can exert a damping-like spin-orbit torque (SOT) tDL on the magnetization of a ferromagnetic (FM) layer attached to the heavy metal (HM). The charge-to-spin conversion is quantified by the damping-like torque efficiency theta DL, which is given by the relation js = (ℏ/2e)theta DL(jc×sigma), where ℏ is the reduced Planck constant, e is electronic charge and sigma is polarization of spin current. Typically, 4d and 5d transition metals (such as Pt, Ta and W) are used as the HM, and their corresponding theta DL are found to be ≈0.1. This intrinsic mechanism depends on the Berry curvature of the material, in which an anomalous velocity arises from a momentum-space Berry phase [2]. An increase in theta DL has been found by alloying the HM with Au, Pd and also by incorporating non-metallic elements (with smaller atomic number Z) into the HM. However, in these materials, a complete understanding of the mechanism responsible for the increase in sigma DL remains elusive. Another phenomenon, the Rashba-Edelstein effect (REE), leads to the generation of nonequilibrium spins at the interface of an inversion asymmetry, in a metal oxide heterostructure [3]. The oxygen vacancies created at the interface lead to mobile conduction electrons forming a quasi-two dimensional electron gas (q-2DEG). An electron having momentum p, in the presence of an electric field E, experiences an effective magnetic field along (p×E). This field leads to spin polarization of the electrons and subsequently a spin current flows from the metal oxide heterostructure to the FM and exerts a tDL on the magnetization of the FM [4]. Similar to SHE, we can define a charge-to-spin conversion efficiency theta DL. So far, a relation between the number of oxygen vacancies and theta DL is yet to be found. Overall, a high theta DL as well as an investigation of its mechanism for the origin of SHE and REE is important in switching the magnetization for writing operation in next generation based magnetic random access memory (MRAM). In this thesis, we perform ion implantation in Pt, using different nonmetallic elements, namely sulfur (S), oxygen (O), nitrogen (N), and phosphorus (P) and study the theta DL via spin-torque ferromagnetic resonance (ST-FMR) measurements [5]. Additionally, we incorporate O in Pt via sputtering, PtOx to compare the sputtering and ion implantation methods. We also compare the q-2DEG created at the interface of SrTiO3/AlN and SrTiO3/Al2O3 in terms of theta DL and a detailed investigation of the angular symmetry of spin-orbit torque (SOT) [6], as well as the calculation of theta DL as a function of temperature and implantation dose (oxygen vacancy) is carried out, revealing the mechanism responsible for enhancement of the SHE (REE). We use a low energy of 12 keV to implant S in Pt, Pt(S) at a dose of 01016-51016 ions/cm2. Next, we use an energy of 20 keV to implant O and N in Pt, Pt(O) and Pt(N), respectively at a varying dose of 01016-11017 ions/cm2. Finally, we move to a moderate energy of 30 keV to implant P in Pt in a wide range of 01016-91016 ions/cm2. For Pt(S), we achieve a high theta DL≈0.50 at 10 K, which is 8-times higher than the theta DL or pure Pt at 10 K. We observe a highly monotonic dose dependence in theta DL of Pt(O) from 0.064 to 0.230 at 293 K, with a smaller trade-off in beta xx from 55.4 to 159.5 mu Ω cm, respectively as we increase the dose from 01016-11017 ions/cm2. For Pt(N), we attain a high theta DL≈at 293 K for a particular dose of 51016 ions/cm2. Finally, for the Pt(P), we obtain a giant theta DL≈ at 293 K, which makes it an ideal candidate of spintronics based MRAM. For PtOx, we also report a high theta DL≈ 0.40 attesting that O in Pt enhances the SHE via both ion implantation and sputtering method. Finally, we explore REE of the q-2DEG created at the interface of SrTiO3/amorphous oxides, namely the SrTiO3/AlN and SrTiO3/Al2O3. We observe a very high theta DL ≈ 2.44 for SrTiO3/AlN than theta DL ≈1.01 for SrTiO3/Al2O3 due to a higher oxygen vacancy enabled REE for the former. The high theta DL is an order higher than the theta DL of 5d transition metal such as Pt. For the dominant underlying mechanism for the ion implanted samples, we confirm a linear dependence of spin Hall resistivity from impurities, beta SH imp with the square of resistivity from impurities, beta 2 imp, i.e., beta SH imp ∝ beta imp [7], implying an extrinsic origin of side-jump scattering as the dominant origin of SHE for the Pt(S), Pt(O), Pt(N) samples studied as a function of implantation and temperature. On the other hand for the PtOx, we do not get a linear beta SH imp ∝ beta 2 mp especially for the lower concentration (n %) of O in Pt, suggesting an intrinsic mechanism while we obtain an extrinsic side-jump for higher n %. In order to disentangle the dominant extrinsic side-jump from the intrinsic SHE, we express the spin Hall conductivity, sigma xy SH as the sum of intrinsic and extrinsic SHE (skew scattering/side-jump) and study it as a function of square of conductivity, sigma 2 xx [8]. We exclude skew scattering as a possible extrinsic mechanism due to the ion-implanted samples not lying in higher of sigma xx of super clean metals (10 6 < sigma xx < 10 8 Ω-1cm-1) [2]. Then, we show that a sudden decrease in intrinsic spin Hall conductivity, sigma int SH is counterbalanced by the increase in side-jump induced SHE, theta sj SH due to the increase in residual resistivity from impurities, beta xx,0. Hence, for all ion implanted samples, Pt(S), Pt(O), Pt(N), Pt(P), we find that higher the beta xx,0, higher is the theta sj SH, and lower is the sigma int SH. We obtain a simple model that theta DL via SHE can be enhanced by simply increasing beta xx,0 in a 5d transition metal. Moreover, we find a crossover of intrinsic to extrinsic side-jump SHE as we increase the dose of S, O, N, P ions in Pt from ≈ 01016-11017 in a wide energy range of 12-30 KeV. Overall, the contribution of the extrinsic side jump induced SHE to the increase in theta DL is clearly identified through our studies on the ion implanted samples. To gain insight into the overlooked contribution of oxygen vacancy to the theta DL via REE in q-2DEG, we find that the higher oxygen vacancy created at SrTiO3/AlN in comparison to SrTiO3/Al2O3, not only plays a role in enhancing the electronic transport, but may also lead to a higher theta DL. To confirm the high theta DL in SrTiO3/AlN, we observe a large direct current modulation of resonance linewidth via direct current biased ST-FMR measurements [5] which is 1-2 order higher than Pt. For understanding the angular symmetry of SOT, which is crucial in estimation of theta DL, via ST-FMR lineshape analysis, we study the ST-FMR spectrum as a function of phi (where phi is the angle between microwave current in device and external magnetic field). In our Pt(S), Pt(O), Pt(N), Pt(P), and PtOx, we observe no breaking of the two-fold and mirror symmetry of SOT due to the 100 % sin2 phi cos phi dependence of symmetric(S) and antisymmetric (A) component of ST-FMR spectrum leading to simple estimation of theta DL. Whereas for q-2DEG, we observe a broken symmetry of SOT and develop an analysis protocol by filtering out the sin2 phi cos phi from S and A arising from tDL and reliably estimate the thata DL. In conclusion, we report that theta DL can be enhanced in host Pt by incorporating non-metallic impurity such as S, O, N, and P in Pt due to the extrinsic side-jump scattering induced SHE from impurities. We obtain a high theta DL for Pt(S) at 10 K and Pt(P) at 293 K. For the q-2DEG, we observe a high theta DL ≈2.44 for SrTiO3/AlN than theta DL ≈1.01 for SrTiO3/Al2O3, which is an order higher than Pt. We explicitly probe the overlooked contribution of oxygen vacancy to the theta DL enabled by REE. These results suggest that the SHE and REE materials could help us in the development of not only MRAM but also in various spintronic based memory devices utilizing the high charge-to-spin conversion in future.九州工業大学博士学位論文 学位記番号: 情工博甲第374号 学位授与年月日: 令和5年3月24日1. Introduction and theory|2. Experimental methods|3. Enhanced spin Hall effect in S-implanted Pt|4. Dose dependent spin Hall effect in O-implanted Pt and Ox sputtered Pt|5. Disentanglement of intrinsic and extrinsic side-jump scattering induced spin Hall effect in O and N-implanted Pt|6. Giant spin Hall effect in P-implanted Pt layers|7. Beyond Ion-implanted Pt: Room temperature charge-to-spin conversion from q-2DEG-based interfaces九州工業大学令和4年

Flexible Human-Robot Interaction in Domestic Environment Using Semantic Map

We propose an efficient semantic map to realize flexible human-robot interaction (HRI) in domestic environments. Our proposed map is created from an output of Simultaneous Localization and Mapping and already-known environmental information such as furniture and room. In this study, we evaluated the effectiveness of our proposed method on two benchmark tests for HRI in RoboCup@Home held in Bangkok in 2022. In the RoboCup@Home, we employ 3D human recognition to apply our proposed map to HRI, such as "find and offer an empty seat." Our proposed method had the best score of all teams on both tests. The results of our experiments are available at https://youtube.com/playlist?list=PLfbN50Mwh2DG3OPDeCHo4TNuyrU4qYCrJ.The 2023 International Conference on Artificial Life and Robotics (ICAROB 2023), February 9-12, 2023, on line, Oita, Japa

Explicit Description of Contact Transformations of Second Order

The aim of this note is to explicitly describe contact transformations on the 2-jet space with one dependent variable using the canonical coordinate system

極低照度状況と高密度散乱媒体状況下での3D画像可視化技術

Recently, three-dimensional (3D) image visualization has become an essential topic in image processing researches. Significantly, the 3D depth information acquisition and visualization under the low light condition or dense scattering media situation are needed in various industrial fields such as unmanned cameras and autonomous vehicles. To visualize the object under harsh conditions, radar and LiDAR have been used. LiDAR can visualize the object shape with discrete point clouds under a dark situation. However, LiDAR may not provide accurate 3D depth information well under inclement weather conditions, such as dense scattering media conditions. To compensate for these shortcomings, it is used with radar in various industries. Radar calculates the depth information using electromagnetic waves, but it only provides the grayscale depth map of the 3D object without object color information. Therefore, it cannot produce sufficient information to recognize the object accurately. On the other hand, the conventional camera can visualize the object with full color and calculate the 3D depth information using integral imaging. Integral imaging is a passive 3D reconstruction method that utilizes elemental images, which have different perspectives of 3D object. Moreover, photon counting has been used to acquire 3D object information under harsh conditions. It can measure the 3D object photons under a dark situation using a photon detector with high sensitivity performance. In addition, it can be used as the feature extractor to visualize the object under the deep scattering media condition. It also can be used for an optical encryption algorithm to keep the data securely. However, photon counting integral imaging has critical issues such as poor visualization performance by significantly sparing photon information and low 3D image visual quality, as explained below. First, photon counting integral imaging reconstruction process may not provide sufficient information in the severely dark situation. It utilizes the maximum likelihood estimation to visualize the object but can reduce the photon intensities. Therefore, it can cause information loss by reconstructing the 3D scene according to the depth. Second, photon counting image contains the measurement error and photon intensity fluctuations through the detector. The photon detector should have a high sensitivity sensor to detect the photons under the low luminance situation. High sensitivity performance is appropriate to detect the photons in the dark situation but can also generate errors and intensity fluctuations.These noises may decrease the 3D image quality under the dark and dense scattering media conditions. To solve these problems, we propose a novel photon counting integral imaging reconstruction method which can visualize the 3D scene even under the severely low-light situation. In addition, we figure out the noise photons and measurement error removal technique by analyzing the photon signal characteristic through the wavelet transform. Chapter 1 introduces the research background and needs for 3D visualization under photon-starved or deep scattering media conditions. We represent various methods to visualize the 3D scene and points out the related problems. Then, we briefly propose our solutions to enhance the 3D image visual quality. Chapter 2 briefly reviews integral imaging and photon counting technique utilized in this thesis. We present the basis of integral imaging technique and photon counting using equations and figures in detail. Then, we highlight the critical issues of photon counting integral imaging technique. Chapter 3 introduces a new reconstruction method that can effectively visualize 3D objects using the small number of photons and apply it to optical encryption, which can encrypt data more securely than conventional methods. We implement optical experiments to demonstrate our proposed method’s superiority and evaluate the image quality using image quality metrics. Chapter 4 presents the noise photons and error removal technique by using wavelet transform. We explain the photon characteristics and show the photon signal analysis result using wavelet transform. Then, we utilize it in photon counting integral imaging and scattering media removal techniques. To prove our noise removal technique and applications, we implement optical experiments and evaluate image quality metrics. Finally, we summarizes our research and presents the achieved objectives through research briefly and suggest the future research plan and objectives in chapter 5.九州工業大学博士学位論文 学位記番号: 情工博甲第376号 学位授与年月日: 令和5年3月24日1 Introduction|2 Conventional 3D visualization under photon-starved and dense scattering media conditions|3 Enhancing 3D image visual quality through the proposed reconstruction method|4 Enhancing 3D Image Visual Quality by Photon Signal Analysis|5 Conclusions九州工業大学令和4年