56016 research outputs found
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Catalyst Technology for Waste Plastic Up-cycling
No full text??????????????? ????????? ????????? ????????? ??? ?????? ?????????????????? ??????????????? ???????????? ?????? ??????????????? ??????????????? ???????????? ???????????? ??????. ??? ???????????? ?????????????????? ??????????????? ??? ??? ?????? ??????????????? ?????? ????????????. ?????????????????? ?????? ?????? ????????? ???????????? ???????????????(PE), ??????????????????(PP)??? ??????????????? ???????????? ????????? ???????????? ?????? ??? ????????? ????????? ??? ??????. ??????????????? ?????? ???????????? ?????? ??????????????? ?????????????????????(PET)??? ??????????????????(Glycolysis)??? ????????? ??????(2-?????????????????????) ?????????????????????(BHET) ???????????? ???????????? ?????? PET??? ????????? ??? ??????. ?????? ?????? ????????? ???????????? ?????????????????? ?????? ????????? ?????? ?????????(Fe3O4) ??????????????? ????????????. ?????? ???????????? ???????????? ????????? ?????? ?????????????????? ????????? ????????????????????? ???????????? ???????????? ???????????? ????????? ??? ??????. ???????????? ?????????????????? ?????? ????????? ?????? ?????? ????????? ???????????? ????????? ?????????
Expedited spark plasma sintering of high???density uranium mononitride pellet utilizing U<sub>2</sub>N<sub>3</sub> powder
No full textThe feasibility of a non-stoichiometric synthesis strategy for uranium mononitride (UN) pellet fabrication is experimentally verified with spark plasma sintering of U2N3 powder in this study. The method removes the denitride process (reduction of U2N3 to UN powder) from the conventional UN pellet fabrication, and it still successfully provided near-perfect UN stoichiometry and high density (94 %TD). During the spark plasma sintering of U2N3 powder, vacuum pressure increase and powder height, decrease were concurrently measured above ???1173 K, which indicates the nitrogen gas emission and higher density UN powder formation from the in-situ decomposition of lower-density U2N3 powder. The X-ray diffraction (XRD) analysis on the sintered pellets obtained directly from U2N3 powder showed an excellent match with the existing XRD reference data of UN. The measured density of U2N3-sintered UN pellets was higher (85 %TD) than that of UN-sintered UN pellets (79 %TD) at relatively low sintering temperature (1773 K). With a higher sintering temperature of 2073 K, high pellet densities (94 %TD) were obtained from both U2N3 and UN powders
Seismic fragility analysis of steel moment frames using machine learning models
No full textThis study develops machine learning (ML) models for seismic fragility analysis of steel moment frames. Four ML methods ??? random forest, adaptive boosting, gradient boosting regression tree (GBRT), and extreme gradient boosting (XGBoost) ??? were employed for this purpose. Probabilistic seismic demand models, each representing the relationship between the seismic response of a type of structure and ground motion intensity, were used to construct the fragility curves based on nonlinear time history analyses of 616 steel moment frames subjected to 240 ground motions. The first three natural periods of steel moment frames and a capacity limit state defined by the maximum interstory drift were selected as input variables for the ML models. Two parameters (median and logarithmic standard deviation) of a fragility function were considered as output variables for the ML models. For each steel frame, the capacity limit state values considered for maximum interstory drift cover a wide range to generalize the fragility curve outcomes. The interquartile range method was used to ensure the quality of the dataset, and consequently 56,479 data points were used for the development of ML models. Based on model performance, the GBRT (R2 = 0.9986, for the testing dataset) and XGBoost (R2 = 0.9987) models are proposed as the best models for fragility analysis of steel moment frames. Finally, a graphical user interface for fragility analysis of steel moment frames was built based on the two proposed models, for easy access by practicing engineers. This study demonstrates the applicability of ML methods in practical design
Design of Sliding Footplate Manipulation Structure for Reducing Physical Demand in an Indoor Personal Mobility Vehicle
Get PDFDepartment of DesignThis paper aims to explore methods for improving the usability and operation demand of the indoor personal mobility vehicle AngGo and propose an enhanced design. While foot-operated controls have been studied in various interaction domains, research on foot-based operation in personal mobility vehicles is limited, with most personal mobility vehicles adopting hand-operated methods. The shared indoor smart mobility (SISM), AngGo features scenarios involving both autonomous and manual driving, with foot-operated controls incorporated in the manual driving mode. However, during various experiments and demonstrations conducted with AngGo, issues regarding physical demand associated with footplate manipulation were identified. To determine the improvement direction for AngGo, evaluations and interviews were conducted with a small group of designers to identify the factors that contribute to physical demand. Based on the interview results, modifications to the mobility vehicle???s size and footplate design were adopted as approaches to reduce physical demand. Ergonomic specifications suitable for seated mobility vehicles were investigated, and an improved design was proposed, along with the design of a compact internal mechanical structure. A usability evaluation was conducted, comparing the revised design with the original design through experiments using a functional prototype, aiming to validate whether the user experience is enhanced. The results demonstrated that the revised design significantly reduced physical demand and effort. This study enhances the usability of AngGo through the improved design and provides reference data for ergonomic specifications in seated personal mobility vehicles. Additionally, the compact internal structure enables more diverse form designs for AngGo.clos
Study of genomic integrity and related diseases using zebrafish
No full textDepartment of Biological Sciencesclos
Functional study of PACSIN2 and DDX41 in hematologic malignancy
No full textDepartment of Biological Sciencesclos
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Get PDFDepartment of Mathematical SciencesThe topic of our study is stability and instability of vortex solutions of the incompressible Euler equations in various settings.
In the first section, we introduce the incompressible Euler equations in 2D, the flow map, vorticity, and the vorticity form of theEuler equations. Then we list conserved quantities of a smooth solution of the Euler equations. After that, we briefly mention about global well-posedness of smooth solutions, weak solutions.
The next section is based on the work in [Calc. Var., vol. 61, p. 120, 2022.], where we are interested in vorticity solutions of the vorticity form in the whole plane . We are considering the situation where the non-negative initial data in L^{\infty}(\mathbbR^{2}) is radial and decreasing. The fact that any radial function is a steady solution of the vorticity form is well-known, and we prove that the monotonicity makes such radial function stable in some norm involving the angular impulse. For example, it includes vortex patches of disc-type and Gaussian functions. Our stability result is free from the supremum or the size of support of perturbations. The main idea of the proof is that the angular impulse of functions with same measure for each level set is uniquely minimized by the radial and monotone function.
The last section contains results from [J. Nonlinear Sci., vol. 32, no. 6, p. Paper No. 97, 2022.]. Here, we are considering the vorticity form in the half cylinder \mathbbR_{>0}\times\mathbbT . In this case, if a vorticity does not depend on , then it is a steady solution of the vorticity form. Moreover, if such steady state is non-negative and decreasing in the -direction, then it has a non-linear stability in a -norm with weight including the -impulse. A cylindrical patch can be its example. Similarly as in \mathbbR^{2} , the main idea of this result is that the -impulse of functions whose measures of every level set are the same is uniquely minimized by the -independent and monotone function. Using this stability, we construct a vortex patch in this domain that shows infinite growth of perimeter for infinite time.clos
Controllable Growth of 2D Materials with Adjustable Intrinsic Properties toward High-Performance Functional Devices
No full textDepartment of Materials Science and Engineeringclos
Synthesis of Large Grain Two-dimensional Transition Metal Dichalcogenides for Electrical Applications
Get PDFDepartment of Materials Science and EngineeringThe use of alkali metal halide catalysts, such as sodium chloride (NaCl), in chemical vapor deposition (CVD) has recently enabled the two-dimensional (2D) growth of transition metal dichalcogenides (TMDs). Despite this remarkable advancement, further exploration is necessary to optimize the process and fully comprehend the underlying growth mechanisms. In our study, we applied thermal evaporation to deposit simultaneously a metal source, molybdenum trioxide (MoO3), and NaCl. As a result, we observed remarkable growth characteristics, including en-hanced 2D growth, easy patterning processes, and increased diversity in potential target materi-als. Through step-by-step spectroscopy and complemented by morphological analysis, we can observe the reaction pathway for the growth of MoS2. This pathway involves NaCl inde-pendently reacting with S and MoO3. These reactions result in the formation of two intermedi-ates, Na2SO4 and Na2Mo2O7, respectively. The intermediates provide an ideal environment for two-dimensional growth. This is achieved through an increased supply of source materials and a liquid medium that facilitates growth. As a result, large monolayer grains of MoS2 are formed by self-assembly involving the merging of small equilateral triangular grains on the liquid interme-diates. Moreover, we successfully synthesized a vertical heterostructure of large monolayer MoS2 and hexagonal hafnium disulfide (HfS2) using AMHs-assisted CVD method. Using this heterostructure, photocurrents were measured across various wavelength regions, and the direc-tion of the photocurrent (Iph) on/off was determined by the barrier formed by the hetero-junction depending on the drain voltage. Furthermore, we observed low dark current (Idark) and high Ilight/Idark, responsivity (R), and detectivity (D*) values. The MoS2/HfS2 heterostructure forms a type-II band alignment, leading to the formation of interlayer excitons that are not observed in single-layer structures. This phenomenon allowed for the measurement of photocurrent (Iph) in the IR region. In conclusion, our research not only deepens the understanding of 2D growth and salt catalysis in TMDs but also pushes the boundaries of the field by demonstrating the fabrica-tion of heterostructures with distinctive properties. This could lead to new applications and uses of these materials in various technological fields.clos
Tailoring Government as a System Toolkit for Sustainability Transition of Gwacheon National Science Museum (GNSM)
Get PDFDepartment of Creative Design EngineeringAs sustainability issues gain increasing global importance, the demand for efforts extends beyond governments to include art museums and cultural institutions. In Korea, museums and related organizations are striving to address these issues. However, their focus is primarily limited to operational and facility aspects, making it challenging to grasp the broader policy perspectives. The National Museum of Modern and Contemporary Art (MMCA) in Korea had a successful opportunity to engage in discussions on specific policy ideas that encompassed not only resource usage and technical solutions but also the acceptability of change and the aspirations of citizens.
This project, titled "A Carbon Neutral Art Museum through speculation with future citizens," utilized a toolkit called "Government as a System" developed by the UK Policy Lab. The toolkit encompasses 56 government actions and aids policymakers in connecting specific policy ideas with corresponding actions. Using this toolkit, policy ideas from citizens were mapped, and MMCA played a pivotal role in this endeavor. Inspired by MMCA's success, the Gwacheon National Science Museum (GNSM), a renowned science museum, expressed an interest in adopting a similar approach to assess the suitability of the toolkit within their own context and role.
This research, conducted as part of the GNSM project, aims to identify the key areas of focus for Gwacheon National Science Museum in Korea and determine which areas require greater attention concerning sustainability issues. The "Government as a System" toolkit serves as the primary instrument for achieving this objective. Through interviews conducted with 10 employees involved in sustainability or long-term planning, qualitative insights were obtained. These insights clarified the actions necessary for sustainability and highlighted the areas where the museum seeks to expand its role as a prominent science museum. The "Government as a System" toolkit was employed to organize and distribute these actions effectively.
The research conducted at Gwacheon National Science Museum enables the identification and prioritization of areas requiring attention for sustainability. Furthermore, similar institutions can adopt this model to assess their current status and develop future plans. Given that museums and cultural institutions are greatly influenced by higher-level governments, the establishment of policies and evaluation criteria based on this model becomes imperative for driving long-term changes.ope