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洞爺湖における言語景観の探索調査
Get PDFapplication/pdfThe objective of this study is to examine the state of foreign language signage in a local Hokkaido community through conducting a linguistic landscape survey of the area. This was done to explore the utility of linguistic landscape surveys as a means for evaluating and improving upon foreign language signage and to promote positive visitor experiences and tourism in local areas in Hokkaido. This exploratory survey was conducted in the Lake Toya resort area in the Iburi region of Hokkaido. Its results were based on a corpus of 418 public signs recorded in the survey area in October, 2017. The results indicated bifurcated top-down and bottom-up trends in public space language use with an overall dominance of monolingual signage and a varied state in multilingual signage. The utility, sufficiency, and suitability of the signage in this area are discussed as are future avenues for developing public spaces conducive to promoting positive tourist experiences in local Hokkaido areas.journal articl
小型超音速飛行実験機の遷音速抗力低減の試みと評価（中胴バルジ，後胴延長，およびインテークの効果）
Get PDFapplication/pdf研究成果の概要 :空力関連departmental bulletin pape
Performance Evaluation of Precast Concrete Using Microwave Heating Form
Get PDFapplication/pdfThe purpose of this study is to evaluate the temperature distribution, strength development, porosity, scanning electron microscopy observation, shrinkage, and surface properties of concrete in order to apply microwave heat curing to the precast method and to analyze the CO2 emissions and economic feasibility of microwave heat curing. The heating of a steel form by microwave heating enabled concrete to be efficiently cured at a temperature within a range of _5 _C. After the curing, demolding strength could be cleared through the densification of the concrete by decreasing the porosity of the concrete. Microwave heat curing exhibited excellent performance compared to conventional steam curing in terms of efficient temperature control, occurrence of cracks due to shrinkage, surface condition of concrete after curing, economic efficiency, and CO2 emissions. However, verification and supplementation based on actual data are necessary so that environments applicable to the various sizes and shapes of forms can be prepared.journal articl
The possibility of development of "businesses utilizing urban parks" from the viewpoint of private enterprise
Get PDFapplication/pdfThe purpose of this research is to consider the possibility of “businesses utilizing urban parks”, paying attention to the viewpoint of private enterprise. Specific research contents will clarify the motivation of private enterprise for “businesses utilizing urban parks”, the conditions of urban parks where businesses are established, etc. We will also consider the possibilities in rural areas where the population is declining. The conclusion of this research is as follows: 1) The existence of many private enterprise expecting “businesses utilizing urban parks” was confirmed, 2)The relationships has been clarified for 5types of motivations, 7types of park conditions,and,3types of business types, 3)The difference between urban and rural areas in “business utilizes urban parks” became clear.journal articl
QuickSquad: A new single-machine graph computing framework for detecting fake accounts in large-scale social networks
Get PDFapplication/pdfGraph-based approaches for fake account detection is one of the important means to fight against fake accounts' attacks on social networks. With the growth of the scale of social networks, more and more researchers begin to use the graph computing framework to boost their detection algorithms. We make detailed analyses of social networks' graph data and state-of-the-art graph computing frameworks, and find that some techniques of the current graph computing systems are overgeneralized and suboptimal, which means they only focus on how to design a graph processing framework on general graphs but miss the optimization of social networks graphs. So, in this paper we propose QuickSquad, a graph computing system on a single server which is specific to the optimization of social networks graph structures. QuickSquad uses the method of "divide and rule" instead of overgeneralization. First, we divide the graph structure data into the heavy set and the light set according to the out-degree of vertices. Then, we 1) store them with different formats, 2) process them with edge-based updating and vertex-based updating appropriately in a two-phase processing model, 3) apply two selective scheduler strategies of different level, i.e. vertex-level and file-level, and 4) provide four cache priorities when the memory is not enough to cache all data. Finally, we implement two detection methods, dSybilRank and dCOLOR, on our system, and the experiments demonstrate that our system can increase the performance up to 5.91X (from 1.14X) compared with the performance of the current graph computing systems, like GridGraph.journal articl
新規Ni含有希土類カルコゲナイドの単結晶育成と物性研究
Get PDF室蘭工業大学Muroran Institute of Technology博士（工学）application/pdfSince binary rare earth chalcogenides exhibit diverse and interesting physical properties, they have been vigorously studied about their composition and crystal structure. For example, the rare earth sulfides ?-R2S3 (R = Tb, Dy) with tetragonal crystal structure exhibit peculiar successive antiferromagnetic transitions. The rare earth tellurides RTe3 (R = Gd, Tb, Dy) with layered structure exhibit charge density wave (CDW) transition and superconducting transition under pressure. In the writer research on a series of rare earth chalcogenides, the magnetocaloric effect (MCE) of ?-R2S3 (R = Tb, Dy) and the physical properties of GdTe3 in high magnetic field and low temperature region were investigated in advance. In addition to such attractive physical properties of rare earth compounds, many characteristic physical properties have also been reported for rare earth compounds including transition metals. In these transition-metal rare earth compounds, there still exist no-studied areas and it is a possible that unknown substances may be hidden, which exhibit novel physical properties leading to materials useful for the next generation society. So in this study, we aimed to search for new rare earth chalcogenides including transition metal. As a result, I discovered new transition-metal rare earth chalcogenides R10NiTe9 (R = Gd, Tb) and investigated their magnetic and electrical properties in detail. Single crystals of R10NiTe9 were grown by heat treatment of a mixture of R, R3Ni and R2Te3. SEM-EDX analysis confirmed that the ratio of R, Ni and Te was about 10: 1: 9. XRD analysis revealed that the obtained single crystal was NaCl-type structure with space group Fm-3m at room temperature. It was concluded that in this structure Ni was randomly substituted Te in a ratio of 1 per 10. In terms of magnetism, the following points have been clarified. (A) In the case of Gd10NiTe9, (1) it exhibits a ferromagnetic transition at 168 K. It implies that I succeeded in emerging ferromagnetism at high temperature by slightly incorporating Ni into GdTe having an antiferromagnetism at a lower temperature. (2) In the magnetization process at low temperature, it has been found that there is a region where the magnetization decreases with increasing the magnetic field. It was also concluded to be cooperative phenomenon between the rare earth element Gd and the transition metal element Ni. (B) For Tb10NiTe9, (1) Two peaks suggesting successive magnetic transitions were found below 120 K in the temperature dependence of magnetization. (2) A remarkable FC / ZFC effect was found below a temperature at which the high temperature side magnetic transition occurs. As for electrical conductivity, the followings were clarified. In both compounds Gd10NiTe9 and Tb10NiTe9, (1) electrical resistivity is about 104 times greater than conventional metal at room temperature. (2) Temperature dependence of electrical resistivity is extremely weak, and the value of electric resistivity hardly changes down to about 50 K. (3) Temperature dependence of electrical resistivity shows a sharp rise below about 50 K. As mentioned above, single crystals of Gd10NiTe9 and Tb10NiTe9 were successfully grown, as new rare earth chalcogenides including Ni, and exhibited novel physical properties on magnetism and electrical conductivity. This result seems to open up a new way to study deepened physical properties of the present compounds, research on physical properties in new compound group R10NiTe9 and develop new materials.二元系希土類カルコゲナイドは多様で興味深い物性を示すので、その組成・結晶構造とともに精力的に研究されてきた。例えば、直方晶系の結晶構造を有する希土類硫化物α-R2S3（R = Tb、Dy）は、特異な逐次的反強磁性転移を示す。層状構造を有する希土類テルル化物RTe3（R = Gd、Tb、Dy）は、電荷密度波（CDW）転移や圧力下での超伝導転移を示す。筆者の一連の希土類カルコゲナイドに関する研究の中で、α-R2S3（R = Tb、Dy）の磁気熱量効果（MCE）と高磁場・低温域におけるGdTe3の物性を先行的に調べた。希土類化合物のこの様な魅力的な物性に加えて、遷移金属を含有した化合物についても多くの特徴的物性が報告されている。この遷移金属含有希土類化合物には、未開の領域が広く存在しており、次世代社会に有益な材料に繋がる新奇物性を発現する未知物質が潜んでいる可能性があるため、本研究では、遷移金属を含有した新しい希土類カルコゲナイドを探索することを目的とした。その結果、筆者は新しい遷移金属含有希土類カルコゲナイドR10NiTe9（R = Gd、Tb）を発見し、これらの磁性と伝導について詳細に調べた。R10NiTe9の単結晶は、R、R3NiおよびR2Te3の混合物の熱処理によって育成された。SEM-EDX分析により、R、NiおよびTeの比が約10：1：9であることが確認された。XRD分析より、得られた単結晶が室温で空間群Fm-3mを有するNaCl型構造のR10NiTe9であることを明らかにした。この構造中でNiはTe10個につき1個の割合で置換する形でランダムに入っていると結論した。磁性の面では次のことを明らかにした。（A）Gd10NiTe9に関して、（1）168 Kで強磁性転移を示す。この意義深い点は、より低温で反強磁性転移を示すGdTeにわずかにNiを含有させたことにより、高温での強磁性を発現させることに成功したことである。さらに、（2）低温における磁化過程において、磁場の増加に対して磁化が減少する領域が存在するという希有な現象を見出した。これに関しても希土類元素Gdと遷移金属元素Niとの協力現象であると結論した。（B）Tb10NiTe9に関しては、（1）120 K以下で二段の逐次磁気転移を示唆する二つのピークを磁化の温度依存性に見出した。また（2）高温側転移点より低温で顕著なFC/ZFC効果も見出した。導電性に関しては、次のことを明らかにした。Gd10NiTe9, Tb10NiTe9両化合物において、（1）電気抵抗率は室温で通常の金属より10 4倍程度以上大きい。（2）その温度依存性は極めて弱く、電気抵抗率の値は50 K 程度までほとんど変化しない。（3）50Kより低温で電気抵抗率が急激な上昇を示す。以上のように新規Ni含有希土類カルコゲナイドGd10NiTe9, Tb10NiTe9の単結晶育成に成功し、磁性と伝導における新奇物性を見出した。この結果は同化合物におけるさらなる深化した物性研究、また新規の化合物群R10NiTe9における物性研究ならびに新材料開発への新たな途を開くと考えられる。doctoral thesi
Structural optimal design with beam propagation method for optical waveguide devices
Get PDF室蘭工業大学Muroran Institute of Technology博士（工学）application/pdf近年、インターネットの総通信量が増加傾向にあり、光通信システムのさらなる高速・大容量化を達成するため、光通信システムの最も基本的な要素である光導波路デバイスの極限までの小型化、低損失化が要求されている。従来、様々な光導波路デバイスは、設計者の電磁気現象に関する深い理解や、これまでに提案されてきた動作原理の知識等に基づいて設計が行われてきた。計算機の計算処理能力の向上や電磁界シミュレーション技術の発展によって、近年は光導波路デバイスの設計に数値シミュレーションを活用した構造最適化手法が積極的に利用されており、その中で、特にトポロジー最適化は非常に高い設計自由度持ち、デバイスの大幅な性能改善および新たな動作原理を持つデバイスの創生の可能性があるとして注目を集めている。従来の光導波路デバイスの感度解析に基づく構造最適化において、数値解析手法として有限要素法（ＦＥＭ）や時間領域有限差分法（ＦＤＴＤ法）等が利用されてきた。光導波路解析において、平面光波回路（ＰＬＣ）デバイス等、波長に対して長手方向のデバイス長が非常に長い場合に対しては、ビーム伝搬法（ＢＰＭ）が効率的な数値解析手法として幅広く利用されている。ＢＰＭを解析手法として用いた感度解析に基づく形状最適設計あるいはトポロジー最適設計例はこれまで報告されておらず、この最適化法が実現できれば感度解析に基づく構造最適化の計算コストが低減可能となり、ＦＥＭやＦＤＴＤ法等では計算コスト上困難な設計問題への応用が期待できる。本論文では、ＢＰＭを活用した光導波路素子の感度解析に基づくトポロジー最適化法の実現を新たに行っており、具体的に２次元ＢＰＭ、３次元セミベクトルＢＰＭ、３次元フルベクトルＢＰＭ、２次元時間領域ＢＰＭを光波伝搬解析手法として利用した場合のトポロジー最適化手法を実現している。本論文では特に、ＢＰＭとして横方向の離散化方法に有限差分法を用いるＦＤ?ＢＰＭ、材料分布の表現手法として密度法、感度解析手法として随伴変数法を適用する場合の感度計算方法を述べている。また、設計変数空間の探索手法には最速降下法を適用している。本手法を曲がり導波路の２次元近似設計問題および３次元設計問題へと適用し、いずれの問題においても提案するトポロジー最適設計手法によって特性が改善するように最適化計算が進むことを確認している。また、パワー分岐導波路、モード次数変換素子、導波路型反射器、偏波回転素子の設計を通して、提案するトポロジー最適化法の汎用性を明らかにしており、本設計アプローチが今後も発展が予想される石英系平面光波回路素子だけではなく、シリコンフォトニックデバイスのさらなる小型化・低損失化に貢献できる可能性を見出した。In recent years, more compact and higher performance optical waveguide devices, which is a fundamental component in optical communication networks, are required in order to deal with the rapid increasing of internet traffic. The optical waveguide devices have been developed based on designer’s experience and profound understanding of guided-wave optics so far. Recently, the structural optimization based on numerical simulation has been used in the design of optical waveguide devices owing to the recent development of computer technology and simulation techniques. Topology optimization has possibility that the device performance is largely improved and a novel operation principle is discovered, because this optimal design method has particular high design of freedom among structural optimization methods. In conventional topology optimization, a finite element method (FEM), or a finite difference time domain (FDTD) method, etc. is utilized as a numerical simulation method of guided-wave in optical waveguides. A beam propagation method (BPM) has been widely used in the field of guided-wave optics, and it can efficiently analyze a long-length device which is difficult to address using the FEM or the FDTD, such as a planner light-wave circuit (PLC) device. It can be expected that the performance of such devices is highly enhanced with very low computational cost if the gradient-based topology optimization utilizing the BPM is realized. In this paper, new topology optimal design approaches utilizing the BPM for optical waveguide devices are realized. In this research, use of the 2DFD-BPM, the semi-vectorial FD-BPM based on alternative direction implicit method (ADIM), the full-vectorial FD-BPM (FV-FD-BPM) based on ADIM, and the time domain FD-BPM based on ADIM is studied. The density method as a representation method of the refractive index distribution in the design region, the adjoint variable method as a sensitivity analysis method are employed to the proposed design approaches, and how to calculate the sensitivity is described in the case of using these methods. In the design example, the steepest descent method is employed as a gradient-based optimization algorithm for finding the minimum point of the objective function. The figure of merit is improved with increasing iteration count in 2D and 3D design problems of the bending waveguide using the proposed design approach, thus the validity of the proposed design approaches is confirmed. Moreover, the usefulness is also considered by designing the optical power splitters, mode order converter, waveguide reflector, and polarization rotator. It is shown that there is possibility that the proposed design approaches enhance the figure of merit of not only PLC devices but also the optical components in silicon on insulator (SOI) platform which is expected to be next-generation optical devices.doctoral thesi
A Study on Design of Tapered Polarization Splitter Using Beam Propagation Method Based on Coordinate Transformation
Get PDFapplication/pdfだ円空孔コア円形空孔ホーリーファイバ(EC-CHFs)を用いたクロストークフリーな偏波分離素子が提案されている．しかしながら，以前の議論では一様な方向性結合器構造が仮定されており，入出力結合は議論されていなかった．本論文では実際の応用を考慮し，結合部において導波路の結合を強め，入出力端において導波路を十分に分離するためにテーパ化した偏波分離素子の設計を行っている．有限要素ビーム伝搬法(FE-BPM)を用いて長手方向に構造が変化する導波路を効率的に解析するために，座標変換により長手方向に不変な導波路構造として解析するFE-BPMの検討も行っている．journal articl