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Catalyst geometry dependent single-walled carbon nanotube formation from polyaromatic hydrocarbon molecule: Pt(111) surface versus Pt nanoparticle
No full textThe chirality controllable synthesis of single-walled carbon nanotubes (SWCNTs) by the catalytic transformation of designed large polyaromatic hydrocarbon molecules has made significant progress in recent years, but the underlying mechanism, such as the role of the catalyst, has never been revealed at the atomic level. In this study, the energy profiles of the dehydrogenation processes from the C60H30 molecule to a (6,6) SWCNT seed on a Pt (111) surface and a Pt55 particle are calculated using first-principles calculations. Our calculations clearly demonstrate that the SWCNT formation process is catalyst geometry dependent, and that it is substantially easier on a curved catalyst surface, i.e., the Pt55 particle, than on a flat Pt(111) surface. Furthermore, catalytic reactions involving Pt adatom on the catalyst surface can considerably reduce the dehydrogenation barriers. This study reveals that employing catalyst particles to synthesize SWCNT from polyaromatic hydrocarbon molecule is a better approach for chirality-controlled SWCNT development
Bridging the Gap between Nonliving Matter and Cellular Life
No full textA cell, the fundamental unit of life, contains the requisite blueprint information necessary to survive and to build tissues, organs, and systems, eventually forming a fully functional living creature. A slight structural alteration can result in data misprinting, throwing the entire life process off balance. Advances in synthetic biology and cell engineering enable the predictable redesign of biological systems to perform novel functions. Individual functions and fundamental processes at the core of the biology of cells can be investigated by employing a synthetically constrained micro or nanoreactor. However, constructing a life-like structure from nonliving building blocks remains a considerable challenge. Chemical compartments, cascade signaling, energy generation, growth, replication, and adaptation within micro or nanoreactors must be comparable with their biological counterparts. Although these reactors currently lack the power and behavioral sophistication of their biological equivalents, their interface with biological systems enables the development of hybrid solutions for real-world applications, such as therapeutic agents, biosensors, innovative materials, and biochemical microreactors. This review discusses the latest advances in cell membrane-engineered micro or nanoreactors, as well as the limitations associated with high-throughput preparation methods and biological applications for the real-time modulation of complex pathological states
Performance of the KAGRA detector during the first joint observation with GEO 600 (O3GK)
Get PDFKAGRA, the kilometer-scale underground gravitational-wave detector, is located at Kamioka. Japan. In April 2020, an astrophysics observation was performed at the KAGRA detector in combination with the GEO 600 detector; this observation operation is called O3GK. The optical configuration in O3GK is based on a power-recycled Fabry Perot-Michelson interferometer; all the mirrors were set at room temperature. The duty factor of the operation was approximately 53%, and the displacement sensitivity was approximately 1 x 10(-18) m/root Hz at 250 Hz. The binary-neutron-star (BNS) inspiral range was about 0.6 Mpc. The contributions of various noise sources to the sensitivity of O3GK were investigated to understand how the observation range could be improved; this study is called a "noise budget". According to our noise budget, the measured sensitivity could be approximated by adding up the effect of each noise. The sensitivity was dominated by noise from the sensors used for local controls of the vibration isolation systems, acoustic noise, shot noise, and laser frequency noise. Further, other noise sources that did not limit the sensitivity were investigated. This paper provides a detailed account of the KAGRA detector in O3GK, including interferometer configuration, status, and noise budget. In addition, strategies for future sensitivity improvements, such as hardware upgrades, are discussed
Analysis of inter-layer between cathode composite and solid electrolyte layer based on the transmission-line model for all-solid-state batteries
No full textSchool of Energy and Chemical Engineering (Energy Engineering (Battery Science and Technology))As the market for electric vehicles using conventional lithium-ion batteries grows, all-solid-state batteries (ASSBs) are an attractive option for next-generation batteries due to their great safety, high energy density, and power capability. However, the increase in cell resistance caused by the poor interfacial contact between solid components results in the degradation of power characteristics. The interfacial contact can be classified into contact of the inner particle in the cathode composites and the contact of inter-layer between the cathode composites and the solid electrolyte layer. In order to deal with the interfacial contact issues, most previous studies have focused on the inner particle problems in the cathode composites, and the inter-layer issues have been overlooked. Considering the fabrication process of ASSB to which a process for a solid electrolyte layer is added, it is important to deal with the inter-layer issues between the cathode composites and the solid electrolyte layer. In this study, the formation of inter-layer between the cathode composites and the solid electrolyte layer was investigated by analyzing the impedance of the inter-layer. An equivalent circuit was devised to estimate the impedance response corresponding to the components of inter-layer contact. The equivalent circuit was modified based on the transmission-line model which describes the electrochemical
impedance response in the cathode composites.
In addition, the effects of the fabrication process on the inter-layer formation was also investigated. The electrochemical characterization was carried out by controlling the compaction process of the cathode composites and the solid electrolyte layer. The compaction process of the cathode composites was demonstrated to have a significant effect on the inter-layer formation by changing the surface roughness of the cathode composites. The rough surface of the cathode composites obtained without the compaction process leads to the intimate inter-layer contact by increasing the contact area between solid electrolytes and decreasing the void volume at the inter-layer. On the other hand, the effect of the compaction process of the solid electrolyte layer was insignificant to the inter-layer formation. Based on the results, it was possible to suggest the fabrication process of ASSB to form the intimate interlayer formation by adjusting the compaction process of cathode composites.clos
A Recurrence Plot based Graph Convolutional Network for Time Series Classification
No full textDepartment of Industrial Engineeringclos
Cluster analysis of cryptocurrencies via deep clustering
No full textDepartment of Industrial EngineeringThe cryptocurrency market has evolved into an attractive investment destination as the number of cryptocurrency assets has increased rapidly and the amount of money invested has become significant. On the other hand, no clear method has been established for how to classify the individual cryptocurrencies. To this end, there is an attempt to divide cryptocurrencies into several sectors using clustering methodology such as k-means with dynamic time warping as a distance measure, which is commonly used in financial time series. However, the non-linear characteristics of the cryptocurrency time series cannot be effectively captured by conventional statistical methods. Deep learning models are known to capture non-linear relationships of data well. This study groups the cryptocurrency time series into four clusters by deep clustering combining an autoencoder, manifold learning technique, and traditional clustering method. We discover that deep clustering can distinguish a stablecoin cluster which other existing models did not capture well. Cluster analysis is attempted to show that deep clustering generates mutually exclusive clusters. Financial properties such as log return distribution, volatility and maximum drawdown of cryptocurrencies in each cluster are investigated. Lastly, the study shows that these clusters are helpful in risk management as a building block for asset allocation in cryptocurrency investment, achieving diversification.clos
Compiler/Accelerator Co-Design Method for Binarzied Neural Networks
No full textGraduate School of Artificial IntelligenceThe binarized neural networks (BNNs) is one of the most promising approaches to deploy deep neural network model on resource-constrained environment such as edge devices. However, actual implemen tations of BNNs do not store weights in the binary format and cannot use bit-wise operations (xnor and popcount) to perform binary convolution and fully connected layers. Therefore, in order to obtain real BNN performance, additional efforts of user must be accompanied. In this paper, we analyze the limitations of existing open source BNN inference frameworks, and propose end-to-end optimization techniques for state-of-the-art BNN models. Compared to the recent BNN frameworks, our framework is 3.6x - 5.5x faster on BiRealNet-18.clos
Development of Large-Scale Seawater Battery Cells for High Energy Density
Get PDFSchool of Energy and Chemical Engineering (Energy Engineering (Battery Science and Technology))Lithium-ion batteries (LIBs) are the most widely used rechargeable energy storage systems. However,
the future expanding of the LIB technology is limited due to the high cost and scarcity of both core
elements of lithium and cobalt. The use of cheap earth-abundant metals such as sodium, aluminum,
potassium, calcium, and magnesium in their corresponding metal-based batteries which working on the
same principle as LIBs, would greatly reduce the cost of battery technology. Nevertheless, despite the
economic advantage of production process, the large-scale production of these metal-based batteries
have been limited by their lower gravimetric and volumetric energy densities.
Rechargeable seawater batteries (SWBs) are regarded as sustainable alternatives to Li-ion batteries due
to the use of an unlimited and free source of Na ion active materials. Although many approaches
including the introduction of new catalysts have successfully improved the performance of SWBs,
reconsidering the cell design is an urgent requirement to improve the performance and scale up the
production of practical batteries.
In this study, by adjusting the maximum space efficiency, a rectangular cell is developed which due to
its unique architecture, benefits from optimized contact to improve the overall charge transfer in the
system.
In view of the rigidity of the solid electrolyte, the novel cell model is intended to have adequate
flexibility to be easily transported and practically utilized. At the same time as the development of the
cell platform, energy efficiency was also improved by improving the materials and assembly methods
for each part of the seawater battery, which will be an indicator for future battery development.
Furthermore, the enhanced efficiency of the parallel stacked modules, indicates the capability of this
cell in practical use.
The seawater battery module was actually operated in the ocean to prove its potential, and an automated
pilot design for uniform cell production was also carried out. The designed catalyst-free cell system
shows a record capacity of 3.8 Ah (47.5 Ah kg???1), energy of 11 Wh (137.5 Wh kg???1), and peak power
of 523 mW for individual unit cell, while it also retains performance up to 100 cycles. This design paves
the way for commercializing rechargeable seawater batteries.ope
Development of microgel-based 3D tumor tissue model to investigate chemotherapeutic effects
No full textDepartment of Materials Science and EngineeringIn vitro cell study has been widely used as the smallest structural and functional unit of living organisms in bio-field industry to develop a variety of biomaterial and drug products. Also, most of cell studies has been carried out as in vitro 2D assay on a plastic well-plate due to simple and low-cost advantages. However, as an in vitro test model to represent the human organ and tissue systems, 2D assay has critical limitations such as environmental difference from the natural 3D organ system, and the restricted interactions between cellular and extracellular matrix. These mismatches could lead cost waste in the bio-field industry because in vitro cell study could not play the subjected role to support much higher-cost in vivo animal test. In this light, the direction of cell test platform needs to head toward increasing in vitro data reliability, while it could be commercially used in bio-field company.
Herein, using two types of hepatocellular carcinoma cells (HepG2 or Hep3B), we fabricate 'cell laden microgel' as a size and component tunable 3D cell culture platform through microfluidics technology, which can generate cell laden microgels in a monodisperse and high-throughput manner. With this microgel model, we adjust various gel-stiffness and hyaluronic acid (HA) component, which composes liver extracellular matrix as bioactive glycosaminoglycans, to mimic the natural human liver tissue modulus and composition, as well as to compare 3D-cultured cell behaviors within various kinds of microgel so that we can analyze each variable effect on the cell fate up to 21 days, not affected by non-uniform diffusion issue. Lastly, we utilize this cell laden microgel as a high-throughput drug screening platform to investigate chemotherapeutic effect since microgel is a constant drug diffusion platform due to micro-sized hydrogel layer.clos
??? ????????? ?????? Target-Ligand Switchable Lactate Oxidase System ??????
No full textDepartment of Biological SciencesThe aggressive tumor formation often causes excessive anaerobic glycolysis leading to the massive production of lactate and its accumulation to the tumor microenvironment (TME). Therefore, it is important to control the lactate concentration in TME to properly modulate surrounding tumor cells and suppress tumor growth. Lactate Oxidase (LOX) is a tetrameric enzyme converting lactate to pyruvate and H2O2 in the presence of oxygen and target-ligand (vSIRP??, EGFRAfb, HER2Afb) is a ligand that interacts with receptor frequently overexpressed on the surface of cancer cells. To control locally accumulated lactate properly, LOX and target-ligand were used as a potential therapeutic enzyme and a tumor cell targeting ligand, respectively, and LOX/ target-ligand conjugates were constructed through a SpyTag/SpyCatcher protein ligation system. LOX/target-ligand selectively bound to the specific receptor overexpressing tumor cells and effectively consumed lactate produced by tumor cells generating adequate amounts of H2O2, which induce drastic necrotic tumor cell death. Local treatments of B16-F10 tumor-bearing mice with LOX/vSIRP?? significantly suppressed tumor growth without any severe side effects. Tumor-targeting vSIRP?? may allow longer retention of LOX onto tumor sites effectively consuming surrounding lactate in TME and locally generating adequate amounts of H2O2 to
suppress tumor growth. The approach controlling the local lactate concentration and H2O2 in TME using LOX and various target-ligand would offer new opportunities for developing enzyme/target-ligand conjugate-based therapeutic tools for tumor treatment.clos