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Mechanical Alloying Process Design by Using DEM Simulation and Experimental Validation
Get PDFMechanical alloying plays a crucial role in controlling and enhancing the characteristics of powder materials which in turn influence the quality and performance of thermal spray coatings. In this study, the optimal milling parameters for mechanical alloying were determined, specifically a rotational speed of 60 rpm, a milling period of 6 hours, and wet milling conditions. These settings led to the best preparation of feedstock powder, resulting in a minimal particle size of 17.5 µm and a narrow particle size dispersion. The observed extensive cataracting and impact zones at this rotational speed of 60 rpm corresponded to 65 of the % critical speed, indicating enhanced milling efficiency. Additionally, DEM modeling demonstrated good agreement with experimental findings, indicating enhanced milling efficiency. Additionally, DEM modeling demonstrated good agreement with experimental findings, highlighting that this rotational speed induced a cataracting regime characterized by a broad zone of impacted particles, yielding the highest impact velocity of 1.79 m/s and a ball indenter force interaction of 1.19 N.journal articl
Performance Evaluation of Techniques for Enhancing Memory Capacity of Reservoir Computing
Get PDF5th International Symposium on Neuromorphic AI Hardware, March 1-2, 2024, Kyushu Institute of Technologyconference pape
組込み開発向けスクリプト言語 mruby/c を対象にしたハードウェアアクセラレーションの設計と評価
Get PDF九州工業大学九州工業大学博士学位論文（要旨）学位記番号:情工博甲第398号 学位授与年月日:令和6年6月28日thesi
局所磁場制御による SiC 表面およびナノ粒子相互作用力解析に関する研究
Get PDF九州工業大学博士（情報工学）1 Introduction| 2 Fundamental theory| 3 Nano-particle movement on a 4H-SiC surface without magnetic field| 4 Development of localized remote magnetic control experimentation system| 5 Manipulability of magnetic nano-particles with localized magnetic field| 6 Action forces on buoyant nano-particle on surface measurement| 7 ConclusionSilicon carbide (SiC) material has become widely used in high-power semiconductors. Owing to its electronic properties surpassing the traditional material. However, surface finishing of SiC remains challenging to achieve an atomic surface performance with damage-free surfaces due to their extremely tough mechanical properties. Chemical Mechanical Polishing (CMP) is a surface finishing process that effectively produces atomically flat damage-free by employing an abrasive nano-particle in the chemical solution.
To improve the material removal performance of the SiC finishing process, the interaction force, a well-known Derjaguin-Landau-Verwey-Overbeek (DLVO) force, of the particle-slurry-substrate needs to be studied in situ in a wet process.
In this thesis, owing to the Brownian motion of the nano-particles, the particles are manipulated approaching the SiC surface by employing the localized magnetic field control and studying the interaction force by optical evanescent field microscopy.
In order to manipulate and measure the interaction force on the nano-particle in the wet process, the optical microscopy system was developed by consisting of two dominant parts, which are an optical microscopy system and a nano-particle manipulation system.
The optical microscopy system part is utilized to experimentally observe the manipulating phenomenon and measure the interaction force on a sample surface by applying evanescent field microscopy. The nano-particle manipulation system is used for pulling the particle approaching the surface by the magnetic field generated by a coil.
Firstly, to verify the manipulability of the particle approaching the SiC surface, iron oxide (Fe3O4) particles with a diameter size of range 50-100 nm dispersed in a slurry adjusted by KOH (pH 10) were employed. The coil was installed under the SiC substrate to generate the pulling magnetic field. The approaching particles to the surface were experimentally observed in situ in the wet process by the developed experimentation system.
Two example particles were able to be observed through their scattering light intensity, which relates to the magnetic field generating sequence wherein the particles were magnetically manipulated to approach close to and held at some height above the SiC surface in Z-direction with 17 mT of magnetic field control approximately.
During the particles pulled to the surface, the particles were tracked the movement in the X-Y directions during the approach to the surface. The Brownian motion ranges of the particles decreased when the particle approached close to the surface which would be limited by the interaction force.
Next, to measure this interaction force, the optical microscopy system was developed by applying the multi-wavelength evanescent fields. The height Z of the approaching particle to the surface was experimentally measured and used to calculate the interaction force at that stable height Z. Owing to the crystal structure of SiC affecting the low image contrast observation, the φ50-100 nm-sized Fe3O4 particles slurry was also employed to manipulate and measure on a silica glass substrate surface because it is higher observed image contrast and zeta potential is also similar to the SiC in an alkane solution.
The particles were magnetically pulled approach close to and held on the surface at the height Z of approximately 20 – 30 nm by the pulling magnetic field value of 40 mT approximately. At this height Z, the interaction force would be 1.4 – 5.4 pN approximately depending on the particle size and the uncertainty of height Z measurement, which summation of the interaction force and the external magnetic force should be equal to 0 N (at Σ ⃑ () = 0 N). To determine the minimum requirement of the external force for contacting the particle on the surface being finished, numerical simulation was employed to model the relationship between the Brownian motion of the particle and the interaction force.
The required minimum external force ( ⃑minex) for contacting particles on the surface is related to the particle size by φ2, namely ⃑mixex ∝ φ2. The magnetic field is inversely proportional to the particle size, namely Z ⃑ [mT] ∝ φ-1[nm-1].
The outcome of this study would be able to be applied to estimate interaction forces on various hard materials, such as diamond, gallium nitride (GaN), etc., to determine the required minimum external force to improve the material removal performance in traditional finishing processes.
Moreover, this proposed measurement method should be a novel surface interaction measurement method, such as zeta potential, for surface science in the future.九州工業大学博士学位論文 学位記番号: 情工博甲第394号 学位授与年月日:令和6年3月25日令和5年度doctoral thesi
ブタトロポエラスチン配列中のオリゴペプチドによる酵素阻害活性の研究
Get PDF九州工業大学博士（工学）第1章 Introduction| 第2章 アンジオテンシンⅠ変換酵素阻害ペプチドの探求と評価| 第3章 チロシナーゼ阻害ペプチドの探求と評価| 第4章 アンジオテンシン変換酵素2阻害ペプチドの探求と評価| 第5章 総括九州⼯業⼤学博⼠学位論⽂ 学位記番号：生工博甲第480号 学位授与年⽉⽇: 令和6年3⽉25⽇令和5年度doctoral thesi
色素増感太陽電池の光電変換性能に及ぼすスクアリン酸色素の中心置換の影響に関する研究
Get PDF九州工業大学博士（学術）1 Introduction| 2 Experimental| 3 Computational molecular design of dyes with varying electron acceptors| 4 Influence of electron acceptors introduced at the central squaric acid core| 5 Fine tuning of dye molecular structure bearing 1,3-indandione as electron acceptor| 6 Enhancing the electron injection efficiency by employing cyanoacrylic acid anchoring group| 7 General conclusions and future outlook of researchAmong the next-generation solar cells, dye-sensitized solar cells (DSSCs), has garnered significant interest from the scientific community because of their cheaper fabrication cost, inherent transparency, variable colors, and higher light harvesting ability especially under low light conditions. The breakthrough research in the field of DSSCs was carried out by Gratzel and O’Regan in 1991, where they reported a photoconversion efficiency (PCE) of 7.9%. Since then, extensive research and optimizations across various DSSC components have enhanced efficiency to 14.2%, surpassing amorphous silicon solar cells. However, this high efficiency is achieved from effective photon harvesting within the visible region only. Moreover, a perusal of the solar spectrum reveals that more than 50% of solar energy emanates from the photon flux beyond 700 nm. This provides hope for enhancing efficiency further by designing novel near-infrared (NIR)- sensitive sensitizers. However, achieving a significant efficiency enhancement for single dye based DSSCs requires wide wavelength photon harvesting (300 – 900 nm) while preserving the energetic balance among the dye, the semiconductor and the electrolyte. The energetics of a sensitizer can be fine-tuned through the incorporation of suitable electron acceptors, that also facilitates wide wavelength photon harvesting.
In this work, novel far-red to NIR-sensitive unsymmetrical squaraine dyes possessing different electron acceptors in their central core were computationally designed. The electron acceptors were judiciously selected to extend the π-conjugation and fine-tune the energetics of the sensitizers with respect to TiO2 and I− /I3 − redox electrolyte. The designed dyes were then subjected to quantum chemical calculations for structural optimization, prediction of their absorption spectra, energetics and the electron density distribution in the HOMO and the LUMO. The theoretical absorption spectra demonstrated that all the core-substituted dyes exhibited the potential of wide wavelength photon harvesting. From the theoretical energy band diagram, it was concluded that the dyes possess a good energetic matching with TiO2 and the I− /I3 − redox electrolyte. The LUMO of the designed dyes exhibit a good diversion of electron density towards the anchoring group thus facilitating a good electronic coupling between the anchoring group and the TiO2. Hence, the theoretical calculations established the potential of these dyes to function as sensitizers in DSSC.
Based on the results of theoretical calculations, the dyes exhibiting the suitable energetics and wide-wavelength photon harvesting, were synthesized, characterized and subjected to photophysical and photovoltaic characterizations. The effect of electron acceptors on the photophysical and photovoltaic performance of the dyes were comprehensively studied. The photophysical results demonstrated that the introduction of electron acceptors led to the emergence of a secondary absorption band in the visible region complementing the primary absorption band in the NIR region, thus facilitating wide wavelength photon harvesting. The introduction of electron acceptors also led to lowering of dye’s HOMO energy level, thus facilitating easy dye regeneration. SQ-223, possessing 1,3-indandione as electron acceptor, exhibited the best PCE (4.67%) attributed to its wide wavelength photon harvesting and lower HOMO energy level.
Although the presence of 1,3-indandione led to a substantial efficiency enhancement, the absorption maximum (λmax) of the dye was not sufficiently red-shifted for effectively harvesting NIR photons. Additionally, the dyes also did not exhibit optimum open-circuit voltage (Voc). Hence, benzo(e)indole donor moiety as well as longer alkyl chains were incorporated in the molecular framework of SQ-258 and SQ-259 to extend the π-conjugation for inducing a red-shift and prevent recombination for improving the Voc, respectively. The incorporation of benzo(e)indole donor moiety led to a significant red-shift in the λmax and the longer alkyl chains led to a reasonable improvement in Voc. However, the overall enhancement in the PCE for SQ-258 was not substantial. Further, there was no improvement in the PCE of SQ-259. This has been attributed to the higher aggregation of the dyes due to the presence of π-conjugated benzo(e)indole moiety as well as hindered electron injection from the LUMO of the dye to the CB of TiO2.
Therefore, in order to facilitate efficient electron injection cyanoacrylic acid anchoring group was introduced in the molecular framework of SQ-260 and SQ-261. The results of theoretical calculations showed that the introduction of cyanoacrylic acid anchoring group led to a maximum diversion of electron density towards the anchoring group in the LUMO of the dye thus displaying the potential of increasing the electron injection efficiency. In addition to this, cyanoacrylic acid also led to a substantial increase in the visible photon harvesting thus facilitating wide wavelength photon harvesting resulting in a maximum PCE of 5.48% for SQ-260. SQ-261 exhibited the most red-shifted λmax at 701 nm due to the presence of both 1,3-indandione and cyanoacrylic acid in its molecular framework. However, SQ-261 exhibited a PCE of only 3.92% attributed to its very low driving force for electron injection as a result of its low energy band gap (Eg). Both SQ-260 and SQ-261 exhibited a huge potential for wide wavelength photon harvesting. Further, it is interesting to note that the onset wavelength in the IPCE spectrum of SQ-261 extended until 840 nm.九州⼯業⼤学博⼠学位論⽂ 学位記番号：生工博甲第491号 学位授与年⽉⽇: 令和6年3⽉25⽇令和5年度doctoral thesi
Global-Local Consistency for Cost-Effective Anomaly Localization with Point Annotations
Get PDFCreating pixel-level ground-truth (GT) masks is quite costly for deep learning-based image segmentation. Specialists in areas such as anomaly detection and medical diagnostics face difficulties in producing many GT masks due to limited resources. To reduce this burden, we propose a cost-effective image segmentation framework with point annotations (CoSPA) that performs image segmentation with only point annotations. Point annotations refer to the partial and sparse labeled coordinates in an image. The key idea is to ensure consistency between the predictions for the same coordinates from the two different networks of CoSPA. This new consistency enables the CoSPA to improve segmentation performance and extend to semi-supervised learning. For the MVTec AD dataset, we verified the cost-effectiveness of CoSPA through an anomaly detection task. We demonstrated that the point annotating costs were reduced by 80% compared to creating GT masks. Subsequently, the CoSPA realized by 87% of the mean Intersection over Union (mIoU) achieved using the fully supervised method, DeepLabV3+. Moreover, the mIoU of CoSPA using only 30% of all point annotations defeated that of the unsupervised method, PaDiM. This study offers a new direction for economic anomaly localization.16th IIAI International Congress on Advanced Applied Informatics, IIAI AAI 2024, July 6-12, 2024, Takamatsu, Japanjournal articl
アジン環を含む有機光触媒による過酸化水素の生成と反応機構の解明
Get PDF九州工業大学博士（工学）1 Introduction| 2 A single atom photocatalyst co-doped with potassium and gallium
for enhancing photocatalytic hydrogen peroxide synthesis| 3 Cobalt derivative loaded covalent organic frameworks for highly
efficient photocatalytic hydrogen peroxide generation under infrared light| 4 Conclusion and outlook九州工業大学博士学位論文 学位記番号:工博甲第597号 学位授与年月日:令和6年9月25日令和6年度doctoral thesi
Drivers of rising monthly water temperature in river estuaries
Get PDFRiver estuaries are habitats for a variety of organisms, including many temperature-sensitive species; water temperatures in estuaries are affected by several factors as they are influenced by both terrestrial and marine environments. Therefore, understanding the factors that influence river estuaries are essential for environmental management. However, no information exists on temperature change at high temporal resolution and over a wide area; moreover, the relationship with environmental factors has not yet been clarified. Here, we have described the actual status of water temperature change in riverine estuaries and its relationship with environmental factors for a wide area of the Japanese archipelago. Our results indicated that 217 of 294 rivers showed a significant monthly increase in water temperature. The average annual change in rates of water temperature increase was the highest in October at 0.090°C yr−1 and lowest in February at 0.068°C yr−1. Furthermore, snowfall, air temperature increase, sea water temperature, and land use were identified as factors increasing the rate of water temperature increase. Factors influencing the increase in river estuarine water temperature varied from month to month—with meteorological factors being the strongest influencers from spring to fall, and anthropogenic factors in winter. Our findings emphasize the importance of considering not only meteorological and oceanographic phenomena, but also anthropogenic influences and topographic features to understand the pattern of water temperature changes in river estuaries.journal articl
Fish fauna and environmental factors in river estuaries of small and medium-sized rivers on islands significantly influenced by warm currents
Get PDFRiver estuaries are influenced by terrestrial and marine areas, and have a unique environment that is constantly fluctuating. They are also important habitats for biodiversity conservation. Tanegashima Island is significantly influenced by the Kuroshio Current. Although nearby Yakushima Island has been recognized as a World Natural Heritage site and information on many species has been collected, there is little information on species inhabiting the river estuaries of Tanegashima Island. In this study, the river estuarine ichthyofauna of 26 small and medium-sized rivers on Tanegashima Island was surveyed and a total of 2758 individuals of 29 species and one genus belonging to 15 families were collected. The fish fauna of the river estuaries of Tanegashima Island were classified into three groups, namely the river estuaries where coastal terraces are underdeveloped and drowned valleys are formed, the river group where the riverbed gradient at the mouth is high, and other river groups. Environmental factors selected as being important for ordination of fish fauna were the altitude of the headstreams at the watershed scale, the gradient of the river estuarine area, and the presence or absence of rapids in the estuary. The importance of the geohistorical factor of drowned valley formation, in addition to habitat and watershed scale environmental factors, as a factor on river estuarine fish fauna is an important finding for future conservation of local biota diversity.journal articl