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Inverted fuel geometry implementation for a fast reactor: Potential improvements in neutronic and thermalhydraulic performance
No full textThis paper presents a detailed procedure for implementing the inverted fuel geometry to a fast reactor to improve its safety system and economy. The study is starting from the fuel unit cell, fuel assembly, reactor core, and burnup analysis. A proposed multivariable graph (v, Delta P, T-F(max)-D-co, V-F) introduced at the fuel unit cell level provides comprehensive thermalhydraulic and neutronic parameters in a single graph, allowing for an efficient optimization process. The fuel unit cell study reveals that the inverted fuel design has a higher fuel volume fraction and lower core pressure drop than conventional pin-typed fuel. This is beneficial for the reactor economy and enhances the reliability of the safety system. With the inverted fuel design, the primary loop can save pumping power by up to 40 % and provides an excess driving force for natural circulation. The male-female axial grid structure separating the fuel assembly potentially eliminates coolant flow path restriction and fretting issues. The core is named the Inverted Core Fast Reactor (IC-FR), an LBE-cooled fast SMR designed to generate 60 MWth for at least 40 years of full-power operation without refueling and fuel shuffling. IC-FR is a transportable reactor and has load following capability that can be deployed for many applications, including marine and land-based applications, and stand alone or mixing power grid. The burnup study of IC-FR reveals that the balance of neutron leakage and fissile inventory yields a small reactivity swing (<1$) for 40 years. This study extensively utilizes Monte Carlo (MC) code MCS for neutronic calculation. Owing to the high computational expense of MC code, the approaches to optimize the MC usage are also presented
The production scheduling problem employing non-identical parallel machines with due dates considering carbon emissions and multiple types of energy sources
No full textThis paper addresses the production scheduling problem with non-identical parallel machines in a high-mix, low-volume production environment with due dates, considering carbon emissions savings and diverse types of energy sources for machine operation. To this end, we present a bi-objective mixed-integer programming model that minimizes both the total production-related cost and the total carbon emissions in the production process to determine the optimal production strategy. For each machine, we consider various types of energy sources with different electricity generation costs and different amounts of carbon emissions. The proposed model is validated with an application to a manufacturer in Ulsan, the industrial capital of the Republic of Korea. Our results showcase the potential use of non-identical parallel machines to minimize the total cost and carbon emissions in green manufacturing. Furthermore, the results identify the trade-off between different energy sources and the total cost under different carbon emissions limits. Generally, as the carbon emissions limit increases, our proposed model tends to replace natural gas with coal to minimize the total cost. Also, we perform sensitivity analyses with respect to the energy price of different types of energy sources combined with nuclear and renewable energy sources. We find that coal provides more stability than natural gas in terms of the total cost, particularly when there are fluctuations in the price for coal and natural gas. Additionally, we determine the optimal combination of energy sources for various carbon emissions limits, aiming to minimize the total cost while simultaneously satisfying all production-related and environmental constraints
Extended Oxygen Octahedral Tilt Proximity near Oxide Heterostructures
No full textThe oxide interfaces between materials with different structural symmetries have been actively studied due to their novel physical properties. However, the investigation of intriguing interfacial phenomena caused by the oxygen octahedral tilt (OOT) proximity effect has not been fully exploited, as there is still no clear understanding of what determines the proximity length and what the underlying control mechanism is. Here, we achieved scalability of the OOT proximity effect in SrRuO3 (SRO) by epitaxial strain near the SRO/SrTiO3 heterointerface. We demonstrated that the OOT proximity length scale of SRO is extended from 4 unit cells to 14 unit cells by employing advanced scanning transmission electron microscopy. We also suggest that this variation may originate from changes in phonon dispersions due to electron-phonon coupling in SRO. This study will provide in-depth insights into the structural gradients of correlated systems and facilitate potential device applications
Dual crosslinking polymer networks: Correlation between polymer topologies and self-healing efficiency
No full textThe topologies of polymers can impact the performance of polymeric materials, including their chemical and physical properties. In this work, a dynamic covalent bond of boronate ester was introduced by the addition of 4-vinylphenylboronic acid to the rich hydroxyl groups of polyglycidols (PGs) with different topologies, including branched cyclic, hyperbranched, and linear PGs. The formation of the dual crosslinked polymer networks, which consisted of dynamic covalent bonds (B???O) and static covalent bonds, was confirmed by thermogravimetric analysis and a swelling test. In addition, the mechanical properties of the cured materials were evaluated using a rheometer, dynamic mechanical analysis, and nanoindentation. Scratch tests and tensile tests were used to determine the self-healing effectiveness of polymer topologies. Intriguingly, based on the polymer topologies, the crosslinked network with a branched cyclic structure (bc-cPGB) exhibited a greater self-healing efficiency and modulus than hyperbranched networks (hb-cPGB). These findings indicate that the physical properties of polymer networks are influenced by the network mesh space and preferred intermolecular crosslinking of the branched cyclic structure. In addition, to maximize the benefits of the dual crosslinking system, the dynamic B???O bonds were utilized for recycling cured materials, and the PG prepolymer was successfully recovered from cPGB by adding pinacol to THF with a yield of 99.5%. These findings demonstrate the significance of topology control in highly adaptable advanced functional materials
Topological Characteristics of Entangled Short-Chain Branched Polymers in Comparison to the Linear Analogs under Shear Flow
No full textEfficient Generation of Reactive Oxygen Species and Their Protein Dysfunction Mechanism for Photodynamic Therapy
No full textA study on miscibility properties of polyacrylonitrile blending films with biodegradable polymer, shellac
No full textPolyacrylonitrile (PAN) films blended with shellac, biodegradable polymer, were prepared via simple solution casting method. The miscibility of PAN with shellac polymer was investigated and the optimal concentration of shellac in terms of hydrogen bonding between shellac and PAN chain was determined to be used as a novel biomass carbon precursor. Shellac and PAN chain could exert interaction and the interaction facilitates to loose the crystalline structure of the PAN chain, suggesting that the decrease of the oxidation temperature of the PAN chain in the PAN/shellac blends film by the introduction of shellac segments. The optimal PAN/shellac blends film exhibited outstanding mechanical performances (73.8% higher tensile strength, 60% higher storage modulus compared with control PAN film) showing homogeneous blending state
Toward Sustaining Bioplastics: Add a Pinch of Seasoning
No full textModern society can no longer sustain accumulating plastic pollution without intervention; plastic waste has even found its way into the food that we consume. Unfortunately, biodegradable alternatives lack sound commercial and economic distinctiveness because mechanical strength and biodegradability are typically mutually exclusive. Inspired by fine cuisine, we introduce a novel synthetic method, referred to as "seasoning", which consists of adding a minimal amount of a biobased multifunctional monomer to pinch the amorphous domains of poly(butylene succinate). Seasoning with only 0.03 mol % of a biobased monomer led to a significantly improved oxygen barrier, high strength (86 MPa), and excellent elongation at break (654%). To the best of our knowledge, this "seasoning" approach with the significant property improvement provided is unique in the bioplastics research field. The proposed approach is highly scalable, relies on existing industrial production, and has the potential to expand current biodegradable plastic applications through its simplicity
High temperature phases of borophene: borophene glass and liquid
No full textBorophene is a family of two-dimensional (2D) boron materials containing many isomers with different hole concentrations and distributions in a triangular lattice. Although it has been widely studied theoretically and some have been synthesized experimentally, their thermodynamic properties are still unexplored. Based on density functional theory (DFT), we developed an accurate potential for the kinetic Monte Carlo (kMC) simulations of borophene. Through extensive kMC simulations, new phases were discovered, such as the glass state of borophene, liquid borophene and borophene with large holes. A phase diagram of borophene is constructed to guide future experiments on borophene materials at high temperature
Small molecules based on 6,7-difluoroquinoxaline and thieno[3,2-b]thiophene for solution-processed solar cells
No full textFluorinated quinoxaline-based small molecules, SM1, SM2, and SM3, were developed as the donor materials for photovoltaic cells. The small molecules containing a 2,3-didodecyl-6,7-difluoroquinoxaline as the electron-deficient unit and thienothiophene as the electron rich units were synthesized by Stille coupling. The small molecules exhibit satisfactory thermal stability and a broad absorption band from 400 to 700 nm. The HOMO/LUMO energy levels of SM1, SM2, and SM3 were -5.70/-3.48, -5.57/-3.42, and -5.66/-3.59 eV, respectively. SM3 with the alkyl group at 4-position in terminal thiophene units has lower HOMO energy levels to increase the V-OC value