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メカノケミカル法を用いたセルロースエステルの合成戦略と材料の評価
Get PDF九州工業大学博士（学術）1 INTRODUCTION AND LITERATURE REVIEW| 2 A STUDY ON COMPARISION OF CONVENTIONAL ESTERIFICATION AND MECHANOCHEMICAL ESTERIFICATION OF CELLULOSE| 3 MECHANOCHEMICAL ESTERIFICATION OF CELLULOSE USING IONIC LIQUID AS SOLVENT SYSTEM| 4 CELLULOSE MODIFICATION AS AN EFFICIENT SYSTEM FOR RAPID TRANSESTERIFICATION| 5 ANALYTICAL OPTIMIZATION FOR MECHANOCHEMICAL REACTION THROUGH CELLULOSE TRANSESTERIFICATION WITH VINYL LAURATE| 6 EVALUATION OF CORRELATION BETWEEN THE CRYSTALLINITY, DEGREE OF SUBSTITUTION, AND MECHANICAL PROPERTIES OF CELLULOSE ESTERS AND COMPARISON WITH COMMERCIAL BIOPOLYMERS| 7 CONCLUSION AND RECOMMENDATIONSPlastic pollution has escalated into a critical environmental issue, drawing significant
attention to bioplastics as potential sustainable solutions. The detrimental effects of conventional plastics on ecosystems, particularly marine environments, have spurred the search for alternatives to mitigate this crisis. Bioplastics have emerged as promising candidates, yet their widespread adoption faces challenges. For instance, polylactic acid (PLA), a commonly used bioplastic, does not degrade effectively in seawater, diminishing its environmental benefits. Moreover, the production processes for many bioplastics involve toxic chemicals, posing further environmental and health risks.
In recent year, cellulose, the most opulent natural polymer on Earth, is increasingly recognized as an assuring raw material for developing alternatives to petroleum-based plastics.
However, cellulose inherently lacks the thermoplastic properties that are typically observed in other bioplastics. To overcome this limitation, researchers have explored the synthesis of cellulose esters. Traditional methods for producing these esters, unfortunately, rely on the use of highly irritating chemicals and involve harsh reaction conditions, which are not environmentally friendly.
Besides, the properties of cellulose esters are significantly influenced by substitution rate and the characteristic of the substituent, but systematic studies in this area are limited.
This research addresses a green approach for synthesizing cellulose esters through mechanochemical techniques, which offer a more sustainable and eco-friendly approach. Various cellulose esters were synthesized with various substituents and degrees of substitution, and their properties were rigorously evaluated to elucidate the unique characteristics of these materials. The outcomes of this study contribute valuable insights and advancements in the field of biopolymer research, paving the way for wider adoption and implementation in the industry and academia.
In Chapter 1, the fundamentals of bioplastics and cellulose, along with studies on cellulose esterification and mechanochemical approaches, are discussed. The relevant literature on the properties of cellulose esters is also outlined in this chapter. Chapter 2 provides a comparative analysis of conventional chemical esterification and mechanochemical esterification of cellulose.
This chapter emphasizes the advantages of mechanochemical esterification, particularly its potential to reduce solvent usage significantly. Additionally, it explores how this method can achieve superior mechanical performance in the modified cellulose. The chapter aims to highlight these benefits as key factors that make mechanochemical esterification a promising alternative to traditional methods.
In Chapter 3, the focus shifts from using pyridine, a toxic solvent, to employing a greener alternative: ionic liquids, for mechanochemical esterification. The chapter details the optimization process undertaken to achieve a greater substitution rate. The importance of not only reducing the amount of solvent used but also considering the toxicity of the solvent is emphasized, aiming to produce a sustainable and environmentally friendly bioplastic. Chapter 4 elucidates the effect of side chain length on the mechanochemical transesterification of cellulose esters. It highlights that long fatty acid side chains not only enhance biodegradability but also improve the reaction rate compared to conventional methods. Additionally, the transesterification process can significantly reduce the reaction time to within 5 minutes.
In Chapter 5, response surface methodology is employed to further optimize the reaction, allowing for the prediction of optimal reaction conditions. This approach enables the achievement of various DS values of cellulose ester by simply adjusting the reaction conditions as suggested by the software, thus broadening the utilization of cellulose. Additionally, cellulose can be reproduced using this simple magnetic pestle and mortar method.
Chapter 6 summarizes the mechanical properties of cellulose derivatives from different esterification methods and compares them with commercial biopolymers. It was found that low DS conserved the hydrogen bond network, while long alkyl chains significantly increased the hydrophobic properties of cellulose esters. This work provides new insights into how cellulose, a well-known but underutilized material, can be leveraged for developing materials and products through a mechanochemical approach.
This dissertation provides an overview of a green and efficient (short reaction time) modification method. Additionally, the use of an automated mortar and pestle enables the production of functional cellulose esters with enhanced biodegradability. This method not only lowers the Tg, thereby improving processability, but also enhances the reproducibility of the product. Overall, this approach offers a simple and effective way to produce cellulose derivatives.九州⼯業⼤学博⼠学位論⽂ 学位記番号：生工博甲第511号 学位授与年⽉⽇: 令和7年3⽉25⽇令和6年度doctoral thesi
Temperature Suppression of Transformer Windings for Current Resonant Converter with High Power Density and Wide Input Voltage Rang
Get PDF電流共振コンバータには、広入力電圧範囲と高電力密度を同時に満たすことが要求されている。しかし、トランスの巻き線温度が著しく上昇する問題が発生する。この問題の発生メカニズム及び解決手法はこれまでの研究で明らかにされている。しかし、その手法の適用により、軽負荷時の制御性が著しく悪化するという新たな問題が発生している。本稿では、この問題を解決するため、ギャップ広くすることなく比較的大きな漏れインダクタンスを発生させるトランス構造について電磁界シミュレーションにより検討する。A current resonant converter satisfying both of wider input voltage range and higher power density is required. It has been found that the drastic increasing of the transformer winding temperature becomes a severe problem, and the mechanism and its solution has been also clarified so far. However, the additional problem has been found which becomes significantly worse the control characteristics. This paper investigates the transformer structure without wide air gap based on electromagnetic field simulation in order to mentioned above problem.journal articl
Identification of lung nodules based on combining multi-slice CT images and clinical information
Get PDFAlthough chest CT scans are an effective means of diagnosing lung cancer, there are still problems such as the heavy burden on physicians. To solve this problem, computer-aided diagnosis (CAD) systems are being introduced. Conventional CAD systems are based on a method that uses only image information. In this study, we propose a method for identifying nodular shadows that integrates a composite image created from multi-slice CT images and clinical information such as the patient's age, sex, and medical history in the medical record. The proposed method extracts features from the multi-section CT and clinical information, respectively, integrates the features, and then performs binary classification of nodules and vessels using a classifier. The proposed method achieved a very high accuracy of Accuracy=0.983, TPR=0.987, and FPR=0.018.conference pape
Scattering Medium Removal Using Adaptive Masks for Scatter in the Spatial Frequency Domain
Get PDFTo address this issue, this paper presents an adaptive method for removing scattering media using a mask based on wireless communication fading models. We hypothesize a similarity between light propagation and wireless communication systems, which incorporates scattering estimates through models such as the Rayleigh and Rician fading models, which are applied to process the captured images and mitigate scattering effects. Our proposed method incorporates two systems: the Scattered Image Model and the Scattering Media Model. The conventional dehazing method requires processing sequences’ approximated depth map or specific background. However, the proposed method functions regardless of the image’s depth and specific background colors. To validate the proposed method, we conducted optical experiments and tested outdoor images. The results were compared with conventional haze-removal methods, such as dark channel prior and Peplography, using various image quality metrics, e.g., the Peak Signal-to-Noise ratio, Structural Similarity Index Measurement, Tone Mapped Image Quality, and Feature Similarity Index Measurement extended to color imagery. The experimental results demonstrated significant improvements over the conventional methods across all metrics.journal articl
色素増感太陽電池におけるコスト削減と耐久性向上に向けたアプローチ
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: 生工博甲第503号 学位授与年月日:令和7年3月25日thesi
Development of a Time-Synchronized Projector-Camera System for High-Clarity Underwater Imaging
Get PDFWe developed a time-synchronized projectorcamera system (SyncProCam) for high-clarity underwater imaging. The proposed system uses a rolling shutter camera and a laser projector, synchronized via a custom-designed digital circuit to capture only direct light reflected from the target. The timesynchronous circuit was implemented using an FPGA, which includes an IIR filter to remove noise and irrelevant signal components from the projector's MEMS mirror signal and a digital circuit to detect the projector's scanning start timing. These components enabled the successful generation of temporally precise camera trigger signals. Experimental results in turbid water environments demonstrate that the standalone SyncProCam enhances image clarity compared to generalpurpose cameras.journal articl
Polyvinylpyrrolidone Influences the Sol–Gel Preparation and Heat Generation Ability of Zinc–Cobalt Ferrite Nanoparticles Designed for Hyperthermia
Get PDFMagnetic nanoparticles generate heat when exposed to an alternating magnetic field, making them useful as thermoseeds for efficient hyperthermia treatment of deep-seated cancer inside the body. Among them, the Curie point of zinc–cobalt ferrite can be tuned within the 40°C range by controlling the composition, thereby suppressing excessive temperature increases in the body during treatment. These nanoparticles are also expected to have antibacterial effects. During synthesis, the microstructure and properties can be regulated by adding organic substances. Herein, zinc–cobalt ferrite nanoparticles were synthesized using sol–gel methods with varying amounts of polyvinylpyrrolidone (PVP), and the effects of the synthesis conditions on the microstructure, magnetic properties, and heat generation behavior were investigated. The highest temperature increase of around 60°C was observed for samples prepared with 6 wt% PVP, but it decreased when the concentration was increased to 9 wt%. This was attributed to aggregation and the formation of nonmagnetic compounds.journal articl