ABSTRACT. Molokai, one of Hawaii's smallest and most rural islands, faces significant energy challenges due to its isolated location and high dependence on imported oil for electricity generation. This paper presents an integrated approach to address Molokai's energy sustainability by optimizing the utilization of renewable resources and integrating electric vehicles (EVs) into the grid. The analysis encompasses Molokai's unique socio-economic and geographical characteristics, including its stable yet economically challenged population, high electricity costs, and vulnerability to climate change impacts. The optimization framework focuses on maximizing renewable energy penetration while ensuring grid stability and reliability. It considers the deployment of photovoltaic (PV) systems and lithium-ion batteries to augment the existing diesel-based generation infrastructure. Load curves and irradiance data are utilized to model energy consumption and solar generation patterns accurately. Furthermore, EV grid support services are investigated, distinguishing between rigid and flexible EV models, to harness their potential for demand response and emergency power supply.

Results indicate that integrating renewable resources, particularly PV, coupled with EV participation, can significantly enhance Molokai's energy sustainability. The optimized scenario achieves renewable generation levels of up to 94%, reducing dependency on fossil fuels and mitigating greenhouse gas emissions. Sensitivity analysis demonstrates the impact of varying renewable energy penetration targets on system performance, highlighting the importance of policy support and technological advancements.

Overall, this study offers valuable insights into designing sustainable energy systems for remote islands, emphasizing the pivotal role of renewable energy integration and EV participation in achieving energy resilience and environmental sustainability.

ABSTRACT. In this study, a vibration generator with a very narrow air-gap structure was designed and improved by analyzing the magnetic circuit of the generator based on a magnetostrictive material (Fe–Ga alloy). A MATLAB Simulink simulation model of the magnetic circuit was developed for a rapid prediction of the output performance of the generator device. A static magnetic field simulation of the device was performed using the finite element method to determine the magnetic flux in the coil and in each magnetic circuit, and to derive the leakage reluctance. The relationship between the amplitude of the vibrogenerator device and the internal stresses in the Fe–Ga alloy was determined by performing a stress simulation. A mathematical model was established to express the relationship between the amplitude and air-gap reluctance, and a lookup table module was used to characterize the nonlinear reluctance (stress–flux density–permeability) of the ferromagnetic material, thus creating a complete model of the magnetic circuit. The time waveform of the open-circuit voltage was simulated by inputting a constant-frequency sinusoidal vibration into the model. Finally, vibration experiments were conducted using a prototype. Compared with the conventional air-gap structure, an extremely narrow air-gap structure could produce a greater change in the air-gap reluctance at the same amplitude, thus effectively improving the power generation efficiency of the vibration power generator. The accuracy of the simulation model was verified by comparing the open-circuit voltages obtained in the simulation and experiment.

ABSTRACT. The objective of this work is to enhance the value of bio-succinic acid as a substrate to produce diethyl succinate (DES) and exploring its applications as a renewable fuel additive. The study employed a kinetic analysis of the succinic acid/ethanol esterification reaction, focusing on parameters such as reaction rate constant (k-value), activity coefficients (γi), activation energy (Ea), and equilibrium constant (keq). Using the pseudo-homogeneous mixture and the NRTL model, the activity coefficients for succinic acid (SA), ethanol (EtOH), monoethyl succinate (MES), DES, and water (H2O) were determined to be 0.288, 1.049, 0.854, 8.957, and 1.74, respectively. Vapor permeation (VP) was employed with the objective to remove water from the reaction resulting in an increase in the product yield. The dehydration performances of commercial ceramic and polymer membranes were evaluated. The commercial ceramic membrane showed the highest DES productivity due to superior water separation capabilities. Kinetic parameters were utilized in process simulation demonstrated that VP-assisted esterification could achieve a DES productivity of 0.27 kmol/h and a conversion yield of 93.23% from succinic acid. This research also explores the potential of DES as a renewable fuel additive and a component in bio-based chemicals for sustainable energy solutions. The findings highlight DES’s efficacy as a green solvent, a potential biofuel additive, and a material for renewable energy applications. The integration of the kinetic model with membrane-based vapor permeation technology offers a novel approach for enhancing the sustainability and efficiency of the esterification process.

ABSTRACT. The spin-Seebeck effect is a phenomenon enabling the conversion of thermal energy into spin-thermoelectric (STE) voltage. An insulator-based STE generator is composed of a thin paramagnetic metal (PM) layer for generating a voltage V_STE via the inverse spin Hall effect (ISHE) and a ferrimagnetic insulator (FMI) film used for producing spin-wave spin currents under a temperature gradient ∇T. Pt, a paramagnetic heavy metal, and yttrium iron garnet (Y₃Fe₅O₁₂, YIG), an FMI, are typical substances used for the thin PM layer and the FMI film, respectively. An issue to be addressed on the STE generator is whether the generator can be utilized for the generation of electric power. A semiconductor Seebeck device is at a practical level in the generation of electrical energy. However, the stable operation of the semiconductor Seebeck device is limited to 100 °C or less. The STE generators using Bi-substituted yttrium iron garnet films that have a Curie temperature of 280 °C are expected to operate in a higher temperature range of 100-250 °C. From the measurement of load characteristics, we have confirmed that the STE generators work as a voltage source. By connecting the STE generator to an electric double layer capacitor (EDLC) that exhibits a large capacitance and a shorter charging time than a rechargeable battery, it is expected to be able to construct an energy storage system of new concept. The system proposed in our presentation is considered to have a capability of recovering the waste heat of relatively high temperatures exhausted in factories and power plants. We are aiming for observing the V_STE value of 250–500 μV at ΔT = 150–250 °C (∇T ≈ 400×10⁻³ °C/μm) by incorporating the Bi:YIG films of high Bi content into STE generators.

ABSTRACT. A dielectric elastomer generator (DEG) using a polymer material called dielectric elastomer (DE) can convert mechanical energy into electrical energy by changing the capacitance of the DE film, which has high energy conversion efficiency and high energy density. In this study, acrylic DEGs were stretched by a pure shear loading method, which is similar to the diaphragm loading method being studied for practical use. The effects of charging voltage and stretch ratio on energy conversion efficiency and energy density were investigated. Here, a "square" energy harvesting scheme that incorporates a constant-voltage charging and discharging method for the DE membrane under large deformation was employed for experiments and analyses. The results showed that the energy conversion efficiency and energy density first increased and then decreased with increasing charging voltage. In the charging voltage range of 1.5 to 2.0 kV, it was shown that 1.9 kV was the optimal charging voltage value for improving energy conversion efficiency and energy density. The energy conversion efficiency and energy density increased as the stretch ratio increased in the range of 4.5 to 5.5, with a maximum energy conversion efficiency of 18.7 % at a stretch ratio of 5.0 and a maximum energy density of 146.4 mJ/g at a stretch ratio of 5.5. These results suggest that charging voltage and elongation ratio are important factors in understanding the influence of these factors on power generation performance in the design of acrylic DEGs.

ABSTRACT. Electric current treatment has been recognized as a low-cost and efficient method for modifying the microstructure, and restoring damage or crack, in metallic materials. Many studies have demonstrated that high-density pulsed current (HDPC) can significantly improve the formability and mechanical property of metallic materials, including steels, aluminum alloys, titanium alloys, and magnesium alloys. It has been reported that HDPC can induce microstructural changes such as dislocation elimination, grain refinement, phase transformation in the materials. In this presentation, the effort of electron wind force, which is the action of electrons impacting atoms induced by HDPC, on the modulation of dislocation, grain boundary, as well as phase structure was reported and the corresponding mechanism was proposed. Due to its ability to rapidly process materials in just a few milliseconds, this technique exhibits ultra-high efficiency compared to traditional methods, offering a powerful tool for the future formation and treatment of metallic materials.

ABSTRACT. When a laser pulse is focused on the solid target in liquid, laser ablation occurs, and bubbles are formed on its surface. The bubble usually collapses or drifted away but, when liquid PDMS is used, the formed bubble remains on the surface and keeps its shape longer than a few minutes. Scanning the laser beam, bubbles are formed in-line and adjacent bubbles merge into a tunnel-like structure. The liquid PDMS changes into solid by heating, and a microgroove which is a replica of the tunnel is formed on the surface of solidified PDMS. Using Cu target, it is found that nanoparticles of Cu are attached on the microgroove surface, indicating Cu particles formation inside the bubble. To clarify this process, we observed single-shot laser ablation of Cu in liquid PDMS directly by shadowgraph and photoluminescence movies. YAG laser with a pulse energy of 1 mJ was used for ablation. The laser-induced bubble of a few hundred micrometer diameter was generated and remained on the Cu surface over a few minutes. The bubble gradually expanded and then floated away from the surface. Fiber-like shadows bridging the bubble and the sample surface were observed and they remained on the surface after the bubble completely detached. To elucidate the particle formation in the bubble, the photoluminescence images in single-shot ablation were observed by a video using YAG:Ce target, for it emits green-yellow photoluminescence under blue-light excitation. They were observed in entire bubble up to approximately 300 seconds, then a crack appeared in the photoluminescence area, and the gas bubble finally floated-up through the crack while the shell-like photoluminescence region remained on the target. These observations revealed that the bubbles were covered with a PDMS film with particles attached on it, and this film retained the bubble on the target surface.

ABSTRACT. Micro-scale light emitting diodes (μLEDs) have been extensively investigated for their applications in augmented and virtual reality displays. Achieving high pixel density, efficiency, brightness, stable emission, and full-color capability is crucial for μLED technology. However, developing full-color μLED displays has been challenging due to the complexity of conventional mass transfer processes, which involve extracting red, green, and blue μLED chips from separate epitaxial wafers and then precisely transferring them. To address these challenges, researchers have explored various approaches. One such approach involves utilizing GaInN with different indium concentrations as luminescent layers. However, the emission wavelength of GaInN is prone to instability due to its temperature-dependent bandgap. Another promising method is the use of rare-earth (RE) doped semiconductors. These materials exhibit strong and sharp emission characteristics due to intra-4f-shell transitions in the RE ion cores, making them ideal for color display and luminescence applications. Historically, considerable effort has been devoted to achieving visible color emission using RE doped GaN. It has been noted that the inclusion of RE ions into wide bandgap hosts can significantly enhance the luminescence efficiency. Furthermore, wide bandgap semiconductors offer excellent thermal and chemical stability, further enhancing their suitability as hosts for RE ions. Our research has unveiled promising results using RE doped Ga2O3 films with a bandgap larger than that of GaN. We have observed that the normalized emission intensity of RE doped Ga2O3 films exhibits less temperature variation compared to RE doped GaN films. Additionally, our investigations reveal that the introduction of aluminum into the films can increase the bandgap, thereby enhancing overall performance. In this talk, we delve into the structural characteristics, surface morphology, and temperature-dependent photoluminescence of RE doped (AlGa)2O3 films. Furthermore, we present recent advancements in achieving full-color LEDs using Eu, Er, and Tm co-doped Ga2O3 films.

ABSTRACT. As the world's population continues to grow, the availability of arable land diminishes, and global climate change intensifies, seaweed has emerged as a nutrient-dense food source. Edible red seaweed Neopyropia spp is especially rich in bioactive compounds like proteins, vitamins, minerals, and fiber, with protein levels reaching 47% of dry weight. This study extracted proteins from Neopyropia haitanensis using acid precipitation, named Ny protein and hydrolyzed Ny protein with Alcalase and Flavourzyme enzymes. Use the ultrafiltration to get the fractions: AF>10, AF3-10, AF<3, and F>10, F3-10, F<3. This study examined the composition, antioxidant, and potential of neuroprotective and anti-aging. The protein content is around 91.1%, confirming protein richness. The hydrolysates with AF>10 demonstrated the best DPPH radical scavenging ability (IC50 = 2.95 mg/mL) and the best ABTS.+ radical scavenging ability (IC50 = 70.18 μg/mL). The Pearson correlation proved these hydrolysates get higher peptide content than Ny protein and improved in vitro antioxidant abilities, effectively scavenging ABTS.+ radicals. In the SH-SY5Y neuroprotection cell model after hydrogen peroxide oxidation stress, hydrolysates (AF>10, AF3-10, F>10, F3-10) had the highest antioxidation ability, the results were non-cytotoxicity and improved cell viability in dose-dependently. and increased intracellular antioxidant enzymes (SOD, GPX1, GST), and total antioxidant capacity (TAC), thereby reducing ROS production and DNA fragmentation. In vivo experiments with wild-type N2 Caenorhabditis elegans showed that Ny protein hydrolysates (AF>10, F>10) reduced ROS production, enhanced feeding, and locomotion in aged worms without affecting growth or development, and improved hydrogen peroxide-induced SOD activity. These findings suggest that Ny protein hydrolysates have potential as functional foods with antioxidant, neuroprotective, and anti-aging properties.

ABSTRACT. An investigation of the seismic performance of the existing building is an urgent requirement around the world to ensure that the building is capable of resisting future earthquakes. Time history analysis (THA) is commonly used to investigate the seismic performance of buildings. However, the selection of ground motions is a discussion topic what is the suitable type of ground motion to perform THA, which are spectrally matched and scaled suite ground motions. Therefore, this study compares responses of matched and scaled suites ground motions in a reinforced concrete building, which was damaged from the previous earthquake. The results indicate that the maximum story drift ratio of the scaled suite ground motions is slightly greater than the matched ground motion, which matches the observed damage experienced during the previous earthquake to the target building. In contrast, maximum velocity, maximum acceleration, and shear force illustrate different trends when compared to the maximum story drift ratios.

ABSTRACT. Renewable energy, such as carbon neutrality, is currently receiving attention. Among them, solar panels that generate direct current (DC) voltage from sunlight are gaining prominence. To convert this DC voltage into alternating current (AC) voltage, Multi-Level Inverters (MLI) are utilized. Naturally, MLIs are desired to be compact, lightweight, highly efficient, and have low Total Harmonic Distortion (THD). This paper proposes a single-phase 7-level inverter to supply household power at 100V @ 50Hz from a single solar panel. A typical topology for a single-phase 7-level inverter is the Multiple Input Single Output (MISO), which supplies a single output voltage from multiple solar panels. While achieving high efficiency, this method requires multiple solar panels. In the proposed MLI, a Single Input Single Output (SISO) configuration is achieved by replacing solar panels with capacitors. Although the number of switches for charging increases compared to conventional circuits, it was possible to reduce the voltage sources. The proposed circuit increases the number of components compared to conventional circuits, but it enables reduction in the number of solar panels, achieving miniaturization and weight reduction. The characteristics of the proposed MLI will be clarified through simulations and experiments. Results will compare output conversion efficiency and THD between conventional and proposed circuits via simulation, and will also demonstrate measurements from the proposed circuit fabricated with discrete components.

ABSTRACT. Pulsed power technology using high-voltage pulses has been used in various settings such as medicine and industry. In recent years, the demand for high-voltage pulse power supplies has increased, and many high-voltage pulse generators have been proposed. Among them, the solid-state Marx generator has attracted the attention of many researchers due to its advantages such as high reliability, low operating costs, high power conversion efficiency, and precise control. Traditional solid-state Marx generators connect all capacitors in parallel during charging, charging all the capacitors simultaneously using the input voltage. As a result, the voltage across all capacitors in the conventional circuit is the same as the input voltage. In contrast, the proposed circuit consists of a Fibonacci module and a boost module. First, in the Fibonacci module, the capacitors are charged with voltages following the Fibonacci sequence. Next, the output voltage of the Fibonacci module is boosted by the boost circuit. This design enables the proposed circuit to achieve more than double the voltage gain compared to traditional solid-state Marx generators using the same number of components. Through circuit simulations, the proposed circuit was compared with the traditional Marx generator regarding power efficiency and output power. Furthermore, the proposed circuit with two stages was assembled with discrete circuit components. The feasibility of the proposed topology was confirmed by comparing measured result with simulated results.

ABSTRACT. Organic bookstores, emerging as cultural and community hubs, play a crucial role in promoting sustainable living and intellectual engagement. This study explores the critical factors that stimulate consumer behavior in Taiwan’s organic bookstores, drawing insights from the Peak-End Rule (Kahneman, 1993). The Peak-End Rule, a psychological heuristic, suggests that people's overall perception of an experience is heavily influenced by the peak (the most intense point) and the end of the experience.To systematically analyze these factors, we employed the Analytic Hierarchy Process (AHP) to construct a hierarchical framework. This framework was developed through a combination of literature review and expert interviews, focusing on five key dimensions of customer experience: Experience, Cognition, Surprise, Glory, and Connection.Expert interviews, including discussions with the executives of Taiwan’s prominent organic bookstores, provided valuable insights into how these factors influence consumer behavior. The AHP methodology facilitated the prioritization of these factors by analyzing their relative weights, thereby identifying the most impactful elements. The study reveals that connection and experience are pivotal in differentiating organic bookstores from traditional ones, making them more attractive and fostering customer loyalty. This suggests that organic bookstores should emphasize creating surprising, unique experiences and nurturing a sense of community to enhance customer engagement and stimulate consumption.The findings provide a strategic framework for organic bookstores to refine their business models and marketing strategies, potentially serving as a guide for other niche retail markets aiming to enhance customer satisfaction and loyalty.

ABSTRACT. Weak degeneracy is a generalization of degeneracy introduced by Bernshteyn and Lee (JGT2023) as a natural upper bound of many coloring parameters of graphs. For a graph $G$, let $\chi(G)$, $\chi_{\ell}(G)$, $\chi_{DP}(G)$, and $wd(G)$ denote its chromatic number, list chromatic number, DP-chromatic number and weak degeneracy, respectively. It is known that $\chi(G)\le \chi_{\ell}(G)\le \chi_{DP}(G) \le wd(G)+1$. In this paper, we prove that if $G$ is a planar graph with maximum degree $\Delta$, then for its line graph $L(G)$, we have (1) $wd(L(G))= \Delta-1$, if $\Delta\geq 21$; (2) $wd(L(G))\leq \Delta$, if $\Delta\geq 9$. This extends some known results on list edge coloring and edge DP-coloring of planar graphs.

ABSTRACT. This day, the lack of efficiency in monitoring and managing waste in the environment is a prevalent issue. Traditional methods of collecting and managing waste often prove to be inefficient, leading to excessive trash accumulation, unpleasant odors, and the potential spread of diseases. Therefore, an innovative solution that integrates GPS and IoT technologies is necessary to efficiently monitor and manage waste, reduce environmental impact, and provide ease in waste management overall. The design and implementation of the Live Tracking System for Smart and Mobile Trash Bins are an innovative solution to monitor and manage waste efficiently and safely. This system employs GPS and IoT technology to monitor the real-time capacity and condition of trash bins. The Smart and Mobile Trash Bins are equipped with sensors, GPS, and IoT modules, and they are connected to an application that simplifies monitoring and displays information. The goal is to enhance efficiency and minimize environmental problems. Designing and implementing the Live Tracking System for Smart and Mobile Trash Bins is an effort to construct a cleaner and more organized environment. Thus, the waste monitoring and management process will yield more organized results through the presence of Smart Trash Bins, such as location tracking of the trash bins, access to waste-related data and weights, as well as facilitating the mobilization of these trash bins.

ABSTRACT. The room management process using traditional keys can lead to several problems, such as loss of access keys, unauthorized key duplication by irresponsible parties, and high human intervention, making the room management process unreliable. These access management issues can be addressed by utilizing smart door technology. Smart door systems with local data storage have limitations in the number of cards they can store. On the other hand, cloud-based smart door systems are dependent on the quality and availability of the internet network. To resolve these problems, the Device to Gateway (D2G) system can be employed. The gateway will perform synchronization or data replication from the cloud using the Event Driven Data Synchronization technique, which utilizes the Advanced Message Queuing Protocol (AMQP). Nodes will connect to the gateway using the ESP Mesh Network protocol for authentication. The ESP Mesh network-based system can perform authentication without an internet connection, reducing dead zones. The average time required for authentication is 1.382ms.

ABSTRACT. To increase chemical reaction rates, general solutions include increasing the concentration/temperature and introducing catalysts. In this study, the rate constant of an electrophilic metal coordination reaction is accelerated 23-fold on the surface of layered aluminosilicate (LAS), where the reaction substrate (ligand molecule) induces dielectric polarization owing to the polar and anionic surface. According to the Arrhenius plot, the frequency factor (A) is increased by almost three orders of magnitude on the surface. This leads to the conclusion that the collision efficiency between the ligands and metal ions is enhanced on the surface due to the dielectric polarization. This is surprising because one side of the ligand is obscured by the surface, so the collision efficiency is expected to be decreased. This unique method to accelerate the chemical reaction is expected to expand the range of utilization of LASs, which are chemically inert, abundant, and environmentally friendly. The concept is also applicable to other metal oxides which have polar surfaces, which will be useful for various chemical reactions in the future.

ABSTRACT. MgH2 is one of the most investigated solid-state hydrides as promising hydrogen storage materials due to its large hydrogen capacity of 7.6 mass% and the high abundance of Mg in Earth's crust. The high thermodynamics (-75 kJ/mol H2) of MgH2 originated from the strong Mg-H binding energy results in the serious issue of high dehydrogenation temperature, i.e. above 300°C for pure MgH2. Alloying with a hydride non-forming transition metal has been approved to be a feasible approach to thermodynamically destabilize MgH2. For example, when alloying with Ni to form a binary Mg2Ni, the hydride transforms from MgH2 to Mg2NiH4, and the enthalpy is reduced from -75 to -64 kJ/mol H2. However, it is hard to produce an Mg-based ternary alloy with a homogeneous elemental distribution by melting process because of the thermodynamic immiscibility of Mg in many systems. This technical issue may be solved by the application of severe plastic deformation. In this study, a new Mg-rich ternary alloy Mg4NiPd was designed and prepared successfully by using high-pressure torsion. Preliminary results indicate hydrogen absorption and desorption can proceed at room temperature, suggesting a feasible approach to design and prepare Mg-based alloys exceeding the scope of known equilibrium phase diagrams for hydrogen storage close to room temperature.

ABSTRACT. The frequency of major earthquakes worldwide has increased in recent years, leading to heightened interest among researchers in the seismic behavior of buildings in long-period ground motion-type earthquakes, one of typic major earthquakes in Japan. While ductile reinforced concrete (RC) structures have proven highly effective in resisting seismic activity, the excessive residual deformation of RC structural components hinders post-earthquake repairability. This paper aimed to elucidate the hysteretic behavior of rectangular-section RC columns using ultra-high-strength steel bars as the first step towards developing RC columns that exhibit stable hysteretic response even during severe earthquakes. Multiple reversed cyclic (MRC) loading tests were conducted to compare the resilience of columns using ultra-high-strength steel bars with low bond or partly-debonded high-strength steel rebars under long-period seismic ground motion and typical seismic motion. The results show that RC columns with low bond and partly debonded high-strength reinforcements demonstrated excellent resilience and self-centering capacity even during large deformations without axial loads. The residual drift ratio and peak lateral force were nearly equivalent. It was revealed that all specimens tended to maintain their lateral force or continue to rise till the drift ratio of 0.05%, indicating a stable hysteretic behavior with small residual deformation.

ABSTRACT. Austenitic steels, due to their excellent heat resistance and oxidation resistance properties, are widely used in industry. As is well known, some austenitic steels undergo a phase transition from FCC to BCC structure at a certain service conditions. Such phase transition phenomenon is generally considered to be a martensite transformation which is associated with elemental depletion or stress-induced reasons. In this study, we observed the presence of a distinct intergranular interlayer near the grain boundaries in a TP347H austenitic steel. This interlayer consists of oxide layers on both sides and a polycrystalline BCC phase in the middle region. It revealed that there were no element depletion during the formation of the BCC phase but resulted in random polycrystalline grain-orientation, with a different mechanism from typical martensite transformation. After carefully examination, it confirmed that the current BCC phase formation induced by a so-called “massive transformation”, and the reason and procedure of the intergranular interlayer were discussed.