Deep Cross-Modal Steganography Using Neural Representations

Steganography is the process of embedding secret data into another message or data, in such a way that it is not easily noticeable. With the advancement of deep learning, Deep Neural Networks (DNNs) have recently been utilized in steganography. However, existing deep steganography techniques are limited in scope, as they focus on specific data types and are not effective for cross-modal steganography. Therefore, We propose a deep cross-modal steganography framework using Implicit Neural Representations (INRs) to hide secret data of various formats in cover images. The proposed framework employs INRs to represent the secret data, which can handle data of various modalities and resolutions. Experiments on various secret datasets of diverse types demonstrate that the proposed approach is expandable and capable of accommodating different modalities.Comment: ICIP 202

Expanding Expressiveness of Diffusion Models with Limited Data via Self-Distillation based Fine-Tuning

Training diffusion models on limited datasets poses challenges in terms of limited generation capacity and expressiveness, leading to unsatisfactory results in various downstream tasks utilizing pretrained diffusion models, such as domain translation and text-guided image manipulation. In this paper, we propose Self-Distillation for Fine-Tuning diffusion models (SDFT), a methodology to address these challenges by leveraging diverse features from diffusion models pretrained on large source datasets. SDFT distills more general features (shape, colors, etc.) and less domain-specific features (texture, fine details, etc) from the source model, allowing successful knowledge transfer without disturbing the training process on target datasets. The proposed method is not constrained by the specific architecture of the model and thus can be generally adopted to existing frameworks. Experimental results demonstrate that SDFT enhances the expressiveness of the diffusion model with limited datasets, resulting in improved generation capabilities across various downstream tasks.Comment: WACV 202

Self and guided assembly of colloids at air-water and substrate -water interfaces

This dissertation presents the development and study of new techniques for fabricating functional nano/microstructures on surfaces or at interfaces by self- and guided assembly of colloids and block copolymers at the corresponding surfaces or interfaces. Fundamental issues related to four different fabrication techniques are discussed. The first method investigated utilizes polyelectrolyte multilayer (PEM) patterns created by soft lithography as surface templates for producing 2-D ordered arrays of colloidal particles with programmed symmetries. The second technique works by transferring a Langmuir monolayer of colloids initially constructed at the air-water interface onto a micro-patterned substrate by the Langmuir-Blodgett (LB) deposition technique; this novel technique developed in our laboratory allows us to fabricate 2-D colloid crystals with unprecedented precision and efficiency. The third is the formation of binary colloidal crystals by spontaneous organization of bidisperse colloid mixtures at the air-water interface under certain thermodynamic parameter conditions. The last topic concerns a new method developed in this thesis work for fabrication of polymer/polyelectrolyte brushes having grafting density gradients. Through combined experimental and theoretical investigations, the research discussed in this thesis explores how, in each of these cases, various thermodynamic and process parameters impact the quality and properties of the resultant colloid/polymer assemblies thus produced

Nanomaterials for Ion Battery Applications

Nanomaterials offer opportunities to improve battery performance in terms of energy density and electrochemical reaction kinetics owing to a significant increase in the effective surface area of electrodes and reduced ion diffusion pathways [...

Stretchable Supercapacitors Based on Carbon Nanotubes-Deposited Rubber Polymer Nanofibers Electrodes with High Tolerance against Strain

We report a new fabrication method for a fully stretchable supercapacitor based on single wall carbon nanotube (SWCNT)-coated electrospun rubber nanofibers as stretchable supercapacitor electrodes. The deposition conditions of SWCNT on hydrophobic rubber nanofibers are experimentally optimized to induce a uniform coating of SWCNT. For surfactant-assisted coating of SWCNT, both water contact angle and sheet resistance were lower compared to the cases with other surface treatment methods, indicating a more effective coating approach. The excellent electromechanical properties of this electrode under stretching conditions are demonstrated by the measurement of Young’s modulus and normalized sheet resistance. The superb tolerance of the electrode with respect to stretching is the result of (i) high aspect ratios of both nanofiber templates and the SWCNT conductors, (ii) the highly elastic nature of rubbery nanofibers, and (iii) the strong adherence of SWCNT-coated nanofibers on the elastic ecoflex substrate. Electrochemical and electromechanical measurements on stretchable supercapacitor devices reveal that the volumetric capacitance (15.2 F cm−3 at 0.021 A cm−3) of the unstretched state is maintained for strains of up to 40%. At this level of strain, the capacitance after 1,000 charge/discharge cycles was not significantly reduced. The high stability of our stretchable device suggests potential future applications in various types of wearable energy storage devices

Enhanced Cycle Stability of Zinc Sulfide Anode for High-Performance Lithium-Ion Storage: Effect of Conductive Hybrid Matrix on Active ZnS

Zinc sulfide (ZnS) nanocrystallites embedded in a conductive hybrid matrix of titanium carbide and carbon, are successfully fabricated via a facile high-energy ball-milling (HEBM) process. The structural and morphological analyses of the ZnS-TiC-C nanocomposites reveal that ZnS and TiC nanocrystallites are homogeneously distributed in an amorphous carbon matrix. Compared with ZnS-C and ZnS composites, the ZnS-TiC-C nanocomposite exhibits significantly improved electrochemical performance, delivering a highly reversible specific capacity (613 mA h g−1 over 600 cycles at 0.1 A g−1, i.e., ~85% capacity retention), excellent long-term cyclic performance (545 mA h g−1 and 467 mA h g−1 at 0.5 A g−1 and 1 A g−1, respectively, after 600 cycles), and good rate capability at 10 A g−1 (69% capacity retention at 0.1 A g−1). The electrochemical performance is significantly improved, primarily owing to the presence of conductive hybrid matrix of titanium carbide and amorphous carbon in the ZnS-TiC-C nanocomposites. The matrix not only provides high conductivity but also acts as a mechanical buffering matrix preventing huge volume changes during prolonged cycling. The lithiation/delithiation mechanisms of the ZnS-TiC-C electrodes are examined via ex situ X-ray diffraction (XRD) analysis. Furthermore, to investigate the practical application of the ZnS-TiC-C nanocomposite, a coin-type full cell consisting of a ZnS-TiC-C anode and a LiFePO4–graphite cathode is assembled and characterized. The cell exhibits excellent cyclic stability up to 200 cycles and a good rate performance. This study clearly demonstrates that the ZnS-TiC-C nanocomposite can be a promising negative electrode material for the next-generation lithium-ion batteries

Gallium-Telluride-Based Composite as Promising Lithium Storage Material

Various applications of gallium telluride have been investigated, such as in optoelectronic devices, radiation detectors, solar cells, and semiconductors, owing to its unique electronic, mechanical, and structural properties. Among the various forms of gallium telluride (e.g., GaTe, Ga3Te4, Ga2Te3, and Ga2Te5), we propose a gallium (III) telluride (Ga2Te3)-based composite (Ga2Te3-TiO2-C) as a prospective anode for Li-ion batteries (LIBs). The lithiation/delithiation phase change mechanism of Ga2Te3 was examined. The existence of the TiO2-C hybrid buffering matrix improved the electrical conductivity as well as mechanical integrity of the composite anode for LIBs. Furthermore, the impact of the C concentration on the performance of Ga2Te3-TiO2-C was comprehensively studied through cyclic voltammetry, differential capacity analysis, and electrochemical impedance spectroscopy. The Ga2Te3-TiO2-C electrode showed high rate capability (capacity retention of 96% at 10 A g−1 relative to 0.1 A g−1) as well as high reversible specific capacity (769 mAh g−1 after 300 cycles at 100 mA g−1). The capacity of Ga2Te3-TiO2-C was enhanced by the synergistic interaction of TiO2 and amorphous C. It thereby outperformed the majority of the most recent Ga-based LIB electrodes. Thus, Ga2Te3-TiO2-C can be thought of as a prospective anode for LIBs in the future

Ga₂Te₃-Based Composite Anodes for High-Performance Sodium-Ion Batteries

Recently, metal chalcogenides have received considerable attention as prospective anode materials for sodium-ion batteries (SIBs) because of their high theoretical capacities based on their alloying or conversion reactions. Herein, we demonstrate a gallium(III) telluride (Ga2Te3)-based ternary composite (Ga2Te3–TiO2–C) synthesized via a simple high-energy ball mill as a great candidate SIB anode material for the first time. The electrochemical performance, as well as the phase transition mechanism of Ga2Te3 during sodiation/desodiation, is investigated. Furthermore, the effect of C content on the performance of Ga2Te3–TiO2–C is studied using various electrochemical analyses. As a result, Ga2Te3–TiO2–C with an optimum carbon content of 10% (Ga2Te3–TiO2–C(10%)) exhibited a specific capacity of 437 mAh·g−1 after 300 cycles at 100 mA·g−1 and a high-rate capability (capacity retention of 96% at 10 A·g−1 relative to 0.1 A·g−1). The good electrochemical properties of Ga2Te3–TiO2–C(10%) benefited from the presence of the TiO2–C hybrid buffering matrix, which improved the mechanical integrity and electrical conductivity of the electrode. This research opens a new direction for the improvement of high-performance advanced SIB anodes with a simple synthesis process

Zn Metal Anodes for Zn-Ion Batteries in Mild Aqueous Electrolytes: Challenges and Strategies

Over the past few years, rechargeable aqueous Zn-ion batteries have garnered significant interest as potential alternatives for lithium-ion batteries because of their low cost, high theoretical capacity, low redox potential, and environmentally friendliness. However, several constraints associated with Zn metal anodes, such as the growth of Zn dendrites, occurrence of side reactions, and hydrogen evolution during repeated stripping/plating processes result in poor cycling life and low Coulombic efficiency, which severely impede further advancements in this technology. Despite recent efforts and impressive breakthroughs, the origin of these fundamental obstacles remains unclear and no successful strategy that can address these issues has been developed yet to realize the practical applications of rechargeable aqueous Zn-ion batteries. In this review, we have discussed various issues associated with the use of Zn metal anodes in mildly acidic aqueous electrolytes. Various strategies, including the shielding of the Zn surface, regulating the Zn deposition behavior, creating a uniform electric field, and controlling the surface energy of Zn metal anodes to repress the growth of Zn dendrites and the occurrence of side reactions, proposed to overcome the limitations of Zn metal anodes have also been discussed. Finally, the future perspectives of Zn anodes and possible design strategies for developing highly stable Zn anodes in mildly acidic aqueous environments have been discussed