56016 research outputs found
Sort by
Nanofibrillar hydrogels outperform Pt/C for hydrogen evolution reactions under high-current conditions
No full textTo achieve efficient hydrogen production, researchers have focused on the development of various electrocatalysts using noble and certain transition metal elements; however, concerns regarding their sustainability are growing. Here, we report a new methodology???hydrogel embedding???that significantly improves the performance of Ni foam (NiF) electrodes for alkaline hydrogen evolution reaction (HER) without the addition of any electrocatalysts. Hydrogel embedment significantly lowered gas bubbles??? adhesion force and imparted extremely bubble-repellent properties (i.e., superaerophobicity) to the underlying electrodes. Consequently, superaerophobic hydrogel-embedded NiF (HG-NiF) exhibited outstanding HER performance, even superior to NiF modified with commercial Pt/C catalysts under practically meaningful high-current conditions. For example, at -0.9 V vs. reversible hydrogen electrode, the HG-NiF and Pt/C NiF allowed current densities of -1.35 and -0.84 A cm-2, respectively. We demonstrate the practical applicability of superaerophobic hydrogel for efficient hydrogen production even without electrocatalysts made of environmentally less sustainable metallic elements
?????? ????????? ????????? ??????????????? ????????? ?????? ????????? ?????? ????????? ???????????? ?????? ???????????? ??????
No full textStudy on relaxor polymer interface matrix for piezoelectric nanocomposite generators
No full textPiezoelectric nanocomposites consisting of a polymer matrix and ceramic fillers are candidate components of flexible, wearable, and self-powered electronic devices. The physical discrepancy between ferroelectric polymers and ceramics in a piezoelectric interface makes it difficult to assemble efficient hybrid piezoelectric nano-composites without polarization and extraneous artifacts. Here, we describe the effect of a relaxor ferroelectric terpolymer matrix on the piezoelectric output, which can enhance the energy harvesting or sensor performance of piezoelectric composite device of nanocomposite generators with filler nanoparticles of lead zirconium tita-nate. The dielectric property and reduced ferroelectric hindrance of the proposed terpolymer matrix provides more poling to align the polarization of piezoelectric ceramic fillers compared with a normal ferroelectric copolymer matrix. Therefore, relaxor ferroelectric polymers can be better than normal ferroelectric polymers as the matrix of hybrid polymer-ceramic piezoelectric nanocomposite. This research provides important physical information about the interface between a polymer matrix and ceramic fillers in flexible piezoelectric nano-composite applications
Spatial integration framework of solar, wind, and hydropower energy potential in Southeast Asia
Get PDFAmid its massive increase in energy demand, Southeast Asia has pledged to increase its use of renewable energy by up to 23% by 2025. Geospatial technology approaches that integrate statistical data, spatial models, earth observation satellite data, and climate modeling can be used to conduct strategic analyses for understanding the potential and efficiency of renewable energy development. This study aims to create the first spatial model of its kind in Southeast Asia to develop multi-renewable energy from solar, wind, and hydropower, further broken down into residential and agricultural areas. The novelty of this study is the development of a new priority model for renewable energy development resulting from the integration of area suitability analysis and the estimation of the amount of potential energy. Areas with high potential power estimations for the combination of the three types of energy are mostly located in northern Southeast Asia. Areas close to the equator, have a lower potential than the northern countries, except for southern regions. Solar photovoltaic (PV) plant construction is the most area-intensive type of energy generation among the considered energy sources, requiring 143,901,600 ha (61.71%), followed by wind (39,618,300 ha; 16.98%); a combination of solar PV and wind (37,302,500 ha; 16%); hydro (7,665,200 ha; 3.28%); a combination of hydro and solar PV (3,792,500 ha; 1.62%); and a combination of hydro and wind (582,700 ha; 0.25%). This study is timely and important because it will inform policies and regional strategies for transitioning to renewable energy, with consideration of the different characteristics present in Southeast Asia
Materializing International Trade of Decarbonized Hydrogen Through Optimization in Both Economic and Environmental Aspects
No full textAs deviations in H-2 production capacity by countries become a considerable barrier to the realization of the global H-2 economy, international trade between countries with abundant resources and those with limited resources is required. In line with this trend, numerous supply chains between several countries have been planned, and associated studies have been conducted. However, the study which treats international overseas H-2 trade chains considering numerous major importing and exporting countries has rarely been conducted before. In this study, a comprehensive optimization for the overseas H-2 supply chain considering the three major importing countries including Korea, Japan, and Germany was conducted with mixed-integer linear programming considering both economic and environmental aspects simultaneously. Through the optimization study, the most feasible H-2 supply chains for each importing country could be verified according to years and case scenarios. Blue H-2 from Qatar turns out to be the most feasible supply chain for Japan in 2030, while green H-2 from South Africa is the most feasible one for other importing countries. In 2040, green H-2 from South Africa and Australia becomes the best one for Asian importers, and Australia finally dominates all the supplies after 2050. In the case of Germany, green H-2 from Spain is considered the best after 2040. Depending on the scenario, the difference in the selected countries and supply amounts is not significant, though the costs are varied. Ammonia turns out to be the most feasible carrier for H-2, and the total cost including the carbon tax ranges from 2.15 to 3.43 $ kgH(2)(-1), which is a range from the current green H-2 to the blue H-2 price
Thermal stability studies of alternating current poled Pb(Mg1/3Nb2/3)O-3-PbTiO3 single crystals grown by solid-state crystal growth
Get PDFThermal stabilities of relaxor-PbTiO3 single crystals are of great importance due to their limited operational temperatures in devices. Herein, to elucidate how poling conditions influence thermal stabilities, we investigated direct current (DC) and alternating current (AC) poled Pb(Mg1/3Nb2/3)O-3-0.29PbTiO(3) (PMN-29PT) crystals grown by solid-state crystal growth, which guarantees more compositional uniformity. Our experiments show that the dielectric permittivity of the DC and AC poled crystals are 3560 and 4970, respectively, after annealing at 99.6 & DEG;C, implying AC-poling prevails in enhancing thermal stabilities of relaxor-PbTiO3 single crystals. The mechanism behind the dissimilar thermal stabilities can be attributed to different domain configurations. IMPACT STATEMENTAlternating-current poling is of useful for not only enhancing piezoelectric and dielectric properties but also improving the thermal stabilities of relaxor-PbTiO3 single crystals
Ckb and Ybx2 interact with Ribc2 and are necessary for the ciliary beating of multi-cilia
No full textBackground
Motile cilia in a vertebrate are important to sustaining activities of life. Fluid flow on the apical surface of several tissues, including bronchial epithelium, ependymal epithelium, and fallopian tubules is generated by the ciliary beating of motile cilia. Multi-ciliated cells in ependymal tissue are responsible for the circulation of cerebrospinal fluid (CSF), which is essential for the development and homeostasis of the central nervous system, and airway tissues are protected from external contaminants by cilia-driven mucosal flow over the top of the airway epithelium.
Objective
A previous study reported that reduction of Ribc2 protein leads to disruption of ciliary beating in multi-ciliated cells. However, knowledge regarding the molecular function of Ribc2 is limited, thus currently available information is also limited. Therefore, we evaluated the importance of proteins involved in the interaction with Ribc2 in the process of ciliary beating.
Methods
Immunoprecipitation and mass spectrometry analysis was performed for the discovery of proteins involved in the interaction with Ribc2. Expression of the target gene was inhibited by injection of antisense morpholinos and measurement of the fluid flow on the embryonic epidermis of Xenopus was performed using fluorescent beads for examination of the ciliary beating of multi cilia. In addition, the flag-tagged protein was expressed by injection of mRNA and the changes in protein localization in the cilia were measured by immunostaining and western blot analysis for analysis of the molecular interaction between Ribc2 and Ribc2 binding proteins in multi-cilia.
Results
The IP/MS analysis identified Ckb and Ybx2 as Ribc2 binding proteins and our results showed that localization of both Ckb and Ybx2 occurs at the axoneme of multi-cilia on the embryonic epithelium of Xenopus laevis. In addition, our findings confirmed that knock-down of Ckb or Ybx2 resulted in abnormal ciliary beating and reduction of cilia-driven fluid flow on multi-cilia of Xenopus laevis. In addition, significantly decreased localization of Ckb or Ybx2 in the ciliary axoneme was observed in Ribc2-depleted multi-cilia.
Conclusion
Ckb and Ybx2 are involved in the interaction with Ribc2 and are necessary for the ciliary beating of multi-cilia
#taggenerator: How an Online Community Designs an Interface for Text Prompt Inputs Using a NovelAI???s Diffusion Model
No full textSuperoxide dismutase mimics as disproportionation catalysts for oxygen reduction reaction in organic solvents
Get PDFSchool of Energy and Chemical Engineering (Chemical Engineering)Superoxide dismutase (SOD) is a kind of natural antioxidant enzyme which protects cells and internal organs by inhibiting undesired reactions caused by reactive oxygen species or superoxide (O2-). SOD catalyzes disproportionation of two highly reactive O2- into less reactive H2O2 and O2 in biological systems: 2 O2- ??? O22- + O2 (dismutation or disproportionation). In the same vein, artificial energy storage devices such as lithium-oxygen batteries (LOBs) or lithium ion batteries (LIBs) based on high-voltage cathode materials also suffer from the reactive oxygen species. In this study, organic or inorganic materials mimicking the roles of SOD or SOD mimics (SODm) are presented as electrolyte additives to stabilize the reactive oxygen species and improve performances of energy storage systems.
LOBs have received considerable attentions due to their high theoretical energy densities (~1700 Wh kg-1 for LOBs versus 100 to 300 Wh kg-1 for LIBs). LOBs use O2 as electron acceptors during discharge process. The ORR proceeds along O2??? O2- ???O22-. The highly reactive intermediate O2- causes undesired side reactions. Even if redox mediators and high-donor-number solvent molecules improved the ORR performances in organic electrolyte, the instability issues caused by O2- have not yet been satisfactorily solved. From the lesson of SOD in biological systems, the superoxide-triggered side reaction pathways could be detoured by adopting SODm. Malonic acid-functionalized C60 fullerene (MA-C60) has been reported as SODm to catalyze the superoxide disproportionation. Since the preferred adsorption of O2-, the generated O2- diffuse into the electrolyte and captured by MA-C60.
In this dissertation, SODm additives were developed to have multifunctionality or different functional mechanism. In addition to the SODm function, TEMPO (2,2,6,6-tetramethylpiperidine 1-oxyl) derivatives (4-carboxy-TEMPO, 4-acetamido-TEMPO) were presented as superoxide dismutase mimetic bifunctional mobile catalyst soluble in electrolytes for improving LOB performances. Unlike MA-C60, TEMPO is electrochemically active species which has a reduction potential of about 3.8 V versus Li+/Li. It can function as charge redox mediator in addition to the function of SODm. From the DFT calculation shows the interaction between O2- and TEMPO derivatives reduce the thermodynamic energy barrier of O2- disproportionation step. The addition of the TEMPO-derivatives increased cycle life of the LOB cells by suppressing O2- triggered side reaction. The promoted O2- disproportionation reduce the chance to react O2- with other cell components. In addition to the side-reaction suppression resulting in more durable operation, interestingly, the possibility that the SODm-catalyzed disproportionation brings additional gains in terms of capacity was confirmed. The capacity of the LOB cells was increased by interaction between O2- and TEMPO derivatives promoting solution mechanism.
Not only electrostatic interaction between O2- and SODm, but electron transfer mediation between O2- also can facilitate O2- disproportionation. Redox activity of 2,5-Di-tert-butyl-1,4-benzoquinone (DBBQ or DB-p-BQ), one of the representative discharge redox mediator, was possibly used for
facilitating superoxide disproportionation reaction by tuning the isomeric configuration of the carbonyl groups of the substituted quinone to change its reduction potential. The ortho- form of the DB-p-BQ, 3,5-Di-tert-butyl-o-benzoquinone (DB-o-BQ), promote O2- disproportionation by facilitating electron transfer between O2-, while the SODm-O2- interaction lowers the thermodynamic energy barrier of O2- disproportionation step in the presence of MA-C60 or TEMPO derivatives. MA-C60 or TEMPO derivatives are redox inactive within the range of discharge potential (< 3 V vs. Li+/Li) but, the redox potential of DB-o-BQ is located between O2/O2- (2.75 V vs. Li+/Li) and O2-/O22- (3.17 V vs. Li+/Li). DB-o-BQ accept electron from O2- and the DB-o-BQ- donate the electron to O2- to from O22- and returns to DB-o-BQ. Also, the second redox potential of DB-o-BQ below 2.75 V vs. Li+/Li, acting as discharge redox mediator, increased the capacity and overpotential of LOB cell during discharge.
From a single-function SODm as a starting point, it was developed into a multi-functioning SODm and a different mechanism of SODm. It should be notified that the O2- interaction and redox potential of SODm concerning the electron transfer between O2- significantly affect the O2- disproportionation reaction. It will provide more opportunities on extending the SODm candidates for superoxide management in energy storage and generation system.ope
Three Essays on The Changes in Global Seafood Market and Export Competitive Advantage
Get PDFDepartment of Management Technology and Innovation ManagementIn the first essay entitled ???What drives a country???s fish consumption? Market growth phase and the causal relations among fish consumption, production, and income growth???, we investigate the main drivers of fish consumption growth in 96 countries over the past 50 years. We categorize the world market for fish consumption into four growth phases: Introduction, Growth, Maturity and Decline. Each country???s fish consumption is estimated using the growth curve model, clustered by dynamic time warping (DTW) together with those countries sharing similar characteristics. Analyzing the relations among the annual growth rates of fish consumption, production, and real GDP using a panel vector autoregressive model (PVAR), we find that the main drivers of fish consumption growth vary across the growth phases. In the introduction phase, fish consumption growth is mainly driven by the growth of RGDP. In the growth phase, RGDP and fish production growth become the main drivers, while in the maturity phase, these drivers do not play a significant role despite their positive coefficients. However, in the decline phase, fish production growth generates a significantly negative impact on fish consumption growth. Identifying the fish consumption market growth phase for policymakers would be the first step toward devising the right policy tools before prioritizing fish consumption management strategies.
In the second essay entitled ???Emerging issue analysis for the seafood industry based on text mining???, we utilize keyword analysis targeting NEWS API (80,000 news sources and blogs) to investigate emerging issues in the global seafood industry from 2019 to 2022. While a variety of topics were identified by year and country in the keyword analysis, in general, the seafood market function as well as health and tariff issues were mainly mentioned in 2019, and COVID-19-related issues were primarily mentioned between 2020 and 2021. After 2022, the role of the market is being emphasized again, and various issues are surfacing. In order to discover emerging issues, dynamic time warping was used and keywords that have recently become issues were derived. The growth model identified 11 representative emerging keywords, including Urbanization, Food safety, WTO (World Trade Organization), Ketones, Cuisines, Wastewater treatment, Seafood alcohol, Consumables, Coercion, Logistics, and Plastic ingestion. Considering high interest in food safety, coexistence with the changing natural environment, preparing countermeasures for trade conflict, and improving the nutritional value of seafood, a policy response was determined to be necessary.
In the third essay entitled ???Determinants of global seafood export???s competitive advantage based on Porter???s diamond model, we employ Porter???s diamond model, a comprehensive and systematic national evaluation model, to analyze the determinants of competitive advantage in the global seafood export market. This study analyzes the determinants of seafood export competitive advantage across five countries with a similar seafood export structure as Korea, from the period of 2000 to 2017. While several diverse determinants have been shown to impact the competitive advantage of seafood exports, efficiency in the form of upscaling fishing boats has a greater influence on seafood export competitiveness than technologically advanced factors. Additionally, it was found that along with the inflow of labor into the fishery industry, the quality improvement of products through the growth of the domestic consumption market and environmental improvement of related industries are also important. Finally, a key characteristic of the seafood export industry is that the government???s role is pivotal. The government needs to consider diversifying trading partners and efforts to prevent the country from becoming one that violates the regulations for illegal, unreported, and unregulated (IUU) fishing.ope