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Study on design of pressure vessels with composite structure
Get PDF横浜国立大学博士（工学）Doctor of Engineeringこの学位論文の全文は、中央図書館で平日17時までに申請することで閲覧が可能です。The full text of this thesis is available for viewing at the Central Library upon request by 5:00 p.m. on weekdays
Research on Persistence of the Antibacterial and Antiviral Effects after Handwashing Utilizing Coacervation Technology
Get PDF横浜国立大学博士（工学）Doctor of Engineerin
Transient complex refractive index spectroscopy with doubleattosecond- pulses-based spectral interferometry
Get PDF横浜国立大学博士（理学）Doctor of Scienc
Structural Effects of Solvents on Li-Ion-Hopping Conduction in Highly Concentrated LiBF4/Sulfone Solutions
Get PDFLi-ion-hopping conduction is known to occur in certain highly concentrated electrolytes, and this conduction mode is effective for achieving lithium batteries with high rate capabilities. Herein, we investigated the effects of solvent structure on the hopping conduction of Li ions in highly concentrated LiBF4/sulfone electrolytes. Raman spectroscopy revealed that Li+ ion forms complexes with sulfone and anion, and contact ion pairs and ionic aggregates are formed in the highly concentrated electrolytes. Li+ exchanges ligands (sulfone and BF4 −) rapidly to produce unusual hopping conduction in highly concentrated electrolytes. The structure of the solvent significantly influences the hopping conduction process. We measured the self-diffusion coefficients of Li+ (DLi), anions (Danion), and sulfone solvents (Dsol) in electrolytes. The ratio of the self-diffusion coefficients (DLi/Dsol) tended to be higher for cyclic sulfones (sulfolane and 3-methylsulfolane) than for acyclic sulfones, which suggests that cyclic sulfone molecules facilitate Li-ion-hopping. The hopping conduction increases the Li+ transference number (tLi+ abc) under anion-blocking conditions, and tLi+ abc of [LiBF4]/[cyclic sulfone] = 1/2 is as high as 0.8.Title of the accepted manuscript is 'Structural Effects of Solvent on Li Ion Hopping Conduction in Highly Concentrated LiBF4/Sulfone Solutions'
Enhanced Electric Double-Layer Capacitance of 1,10-Phenanthroline-Derived Mesoporous Carbon CMK-1 Electrodes via Selective Elimination of Pyridinic Nitrogen during Carbonization
Get PDF1,10-Phenanthroline was carbonized in the wide pores of ordered mesoporous silica (MCM-48; hard template) at different temperatures to yield nitrogen-doped ordered mesoporous carbon CMK-1. Carbonization at 550 °C resulted in inadequate carbon network formation, whereas nitrogen-doped carbons with ordered mesoporous structures and low and high electrical conductivities were obtained at 750 and 900 °C, respectively. When used as an electrode in an electric double-layer capacitor, the high-conductivity carbon delivered a gravimetric capacitance of ∼100 F g−1 and a specific areal capacitance (Cs) of 9.2 μF cm−2, thus breaking the limit of 6.0 μF cm−2 established for conventional activated-carbon electrodes. Advanced temperature-programmed desorption and X-ray photoelectron spectroscopy analyses revealed that heating at 750−900 °C caused the selective elimination of pyridinic nitrogen and initiated recombination reactions within the carbon network to generate a carbon surface with highly adsorptive sites for electrolyte ions, which resulted in a high electric double-layer capacitance
Physical Layer Security for Integrated Sensing and Communication: A Survey
Get PDFIntegrated sensing and communication (ISAC) has become a crucial technology in the development of next-generation wireless communication systems. The integration of communication and sensing functionalities on a unified spectrum and infrastructure is expected to enable a variety of emerging use cases. The introduction of ISAC has led to various new challenges and opportunities related to the security of wireless communications, resulting in significant research focused on ISAC system design in relation to physical layer security (PLS). The shared spectrum usage poses a risk, exposing confidential messages embedded in probing ISAC signals to potentially malicious sensing targets. This situation creates a tradeoff between sensing performance and security performance. The sensing functionality of ISAC offers a unique opportunity for PLS by utilizing sensing information regarding potential eavesdroppers to design secure PLS schemes. This study examines PLS methodologies to tackle the specified security challenge associated with ISAC. The study begins with a brief overview of performance metrics related to PLS and sensing, as well as the optimization techniques commonly utilized in the existing literature. A thorough examination of existing literature on PLS for ISAC is subsequently presented, with the objective of emphasizing the current state of research. The study concludes by outlining potential avenues for future research pertaining to secure ISAC systems
Omnidirectional crack detection in welded structures using a Rotating Three-Pole Magnetization system with a flexible coil array sensor
Get PDFThis study introduces a novel Alternating Current Field Measurement (ACFM) probe based on a Rotating Three-Pole Magnetization (RTPM) configuration integrated with a flexible magnetic coil array sensor. Conventional Eddy Current Testing (ECT) and Magnetic Flux Leakage (MFL) techniques face inherent limitations. ECT is highly sensitive to lift-off and coating thickness, while MFL requires strong magnetization and is restricted to ferromagnetic materials. In contrast, ACFM requires only a small alternating magnetic field to induce surface currents, enabling non-contact and coating-tolerant inspection with direct measurement of magnetic field perturbations (Bz) caused by surface-cracks. However, conventional ACFM systems lose sensitivity to cracks parallel to the induced current direction. To overcome this limitation, the proposed RTPM design generates a uniform in-plane rotating magnetic field, enabling orientation-independent crack detection. Three-dimensional finite element simulation confirm homogeneous induced currents and a clear Bz response at defect sites. Experimental validation on aluminum and steel specimens demonstrates reliable detection of surface cracks as small as 1 mm in any orientation, with stable signals maintained at lift-off distances up to 2 mm. Moreover, the system effectively identifies defects in weld zones, where conventional ACFM, ECT, and MFL methods often struggle due to magnetic and conductivity variations. These results highlight the superior sensitivity, robustness, and practical applicability of the proposed RTPM-based ACFM system for rapid non-destructive inspection of complex industrial structures
Mechanism of Li Ion Desolvation at the Interface of Graphite Electrode and Glyme–Li Salt Solvate Ionic Liquids
Get PDFLi+ intercalation into graphite electrodes was investigated in electrolytes consisting of triglyme (G3) and Li[TFSA] [TFSA: bis(trifluoromethanesulfonyl)amide]. Li+-intercalated graphite was successfully formed in an equimolar molten complex, [Li(G3)1][TFSA]. The desolvation of Li+ ions took place at the graphite/[Li(G3)1][TFSA] interface in the electrode potential range 0.3‒0 V vs Li. In contrast, the cointercalation of G3 and Li+ (intercalation of solvate [Li(G3)1]+ cation) into graphite occurred in [Li(G3)x][TFSA] electrolytes containing excess G3 (x > 1). This cointercalation took place in the voltage range 1.5–0.2 V of the [Li | [Li(G3)x][TFSA] | graphite] cell. X-ray diffraction showed that the [Li(G3)1]+- intercalated graphite forms staged phases in the voltage range 1.5–0.3 V. However, exfoliation of the graphite is caused by further intercalation at voltages lower than 0.3 V. [Li(G3)1]+ intercalation was reversible in the voltage range 1.5–0.4 V. The cointercalation process was studied using cyclic voltammetry, and it was found that the electrode potential for cointercalation depends on the [Li(G3)1]+ activity, irrespective of the presence of free (uncoordinated) G3. In contrast, the electrode potential for the formation of Li+-intercalated graphite (desolvation of solvate [Li(G3)1]+ cation) changes greatly, depending on the activities of not only the solvate [Li(G3)1]+ cation but also free G3 in the electrolyte. In extremely concentrated electrolytes, the activity of the free solvent becomes very low. Raman spectroscopy confirmed a very low concentration of free G3 in [Li(G3)1][TFSA]. Consequently, the electrode potentials for the formation of Li+-intercalated graphite were higher than that for cointercalation, and the cointercalation of G3 was inhibited in [Li(G3)1][TFSA]
Thermal and Electrochemical Stability of Tetraglyme–Magnesium Bis(trifluoromethanesulfonyl)amide Complex: Electric Field Effect of Divalent Cation on Solvate Stability
Get PDFPhase behavior of binary mixtures of tetraglyme (G4) and Mg[TFSA]2 (TFSA: bis(trifluoromethanesulfonyl)amide) was investigated. In a 1:1 molar ratio, G4 and Mg[TFSA]2 formed a stable complex with a melting point of 137 °C. X-ray crystallography of a single crystal of the complex grown from a G4-Mg[TFSA]2 binary mixture revealed that the G4 molecule wraps around Mg2+ to form a complex [Mg(G4)]2+ cation and the two [TFSA]− anions also participate in the Mg2+ coordination in the crystal. The thermal stability of [Mg(G4)][TFSA]2 was examined by thermogravimetry and it was found that the complex is stable up to 250 °C. Above 250 °C, desolvation of the Mg2+ ion takes place and G4 evaporates. On the other hand, the weight loss starts at around 140 °C in solutions containing excess G4 (n > 1 in Mg[TFSA]2:G4 = 1:n) due to the evaporation of free (uncoordinated) G4. The suppression of G4 volatility in the [Mg(G4)][TFSA]2 complex is attributed to strong electrostatic and induction interactions between divalent Mg2+ and G4. In addition, complexation of G4 with Mg2+ is effective in enhancing the oxidative stability of G4. Linear sweep voltammetry revealed that the oxidative decomposition of [Mg(G4)][TFSA]2 occurs at electrode potentials >5 V vs. Li/Li+, while the oxidation of uncoordinated G4 occurs at around 4.0 V. This oxidative stability enhancement occurs because the HOMO energy level of G4 is reduced by complexation with Mg2+, which is supported by the ab initio calculations