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Efficient Fe3O4 nanoparticle catalysts for depolymerization of polyethylene terephthalate
No full textPolyethylene terephthalate (PET) can be recovered as high-purity bis(2-hydroxyethyl terephthalate) (BHET) monomer by glycolysis in the presence of Fe3O4 nanoparticles (NPs). In this study, Fe3O4 NPs of various shapes, sizes, and surface areas were synthesized using different colloidal synthesis methods, and the conversion of PET glycolysis and BHET yield were compared. Spinel ferrite NPs, including Fe3O4, were synthesized using the coprecipitation (CP), thermal decomposition (TD), and the hydrothermal (H) methods. Among the NP catalysts, Fe3O4-CP exhibited the best glycolysis performance with a PET conversion of similar to 100% and BHET yield of 93.5% at 195 degrees C for 2 h owing to its high surface area (146.6 m(2) g(-1)). The larger the surface area and the better the dispersion, the higher the glycolysis activity. The glycolysis performance of the mixed spinel ferrite NPs was similar to that of the Fe3O4 NPs, indicating that replacing Fe2+ in the Fe3O4 NPs with other transition metals, M2+, did not significantly change the glycolysis performance. BHET monomers produced from commercial waste PET bottles in large quantities contained trace amounts of metal contaminants, because PET production uses various metal-based additives and catalysts. Amberlite IRC-120, a cation-exchange resin, effectively removed metal impurities from BHET. This study provides an effective strategy for producing recycled PET (r-PET) by waste PET glycolysis
Max-Min Fairness Precoding for Physical Layer Security With Partial Channel Knowledge
No full textWe propose secure max-min fairness (MMF) precoding for a downlink multi-antenna system with multiple users and eavesdroppers. Since the problem is non-convex and non-smooth and partial channel knowledge is assumed, it is highly challenging to solve. To resolve the difficulties, we first reformulate the problem with conditional average rates, allowing to exploit the partial channel knowledge. Then, we derive the original problem as an approximate smoothing problem using a LogSumExp approach. We identify the first-order optimality condition and cast it to a generalized eigenvalue problem. Solving the problem via a power iteration offers the best local optimal solution. Simulations validate the proposed secure-MMF precoding method
Relationship between PM1.0 and PM2.5 in urban and background areas of Republic of Korea
No full textSeasonal intensive measurements of atmospheric particulate matter with aerodynamic diameters less than or equal to a nominal 1.0 mu m (PM1.0) and 2.5 mu m (PM2.5) were conducted at an urban (Seoul, SL) and a background site (Baengnyeong, BN, an island about 200 km from SL) in Korea to fully understand the characteristics of PM1.0 within PM2.5, as well as the differences in PM characteristics between urban and background sites. A singlechannel particle sampler with PM1.0 and PM2.5 cyclones was used to collect the samples simultaneously. Eight ions (Cl-, NO3-, SO42-, Na+, NH4+, K+, Ca2+, and Mg2+), carbonaceous components (organic carbon (OC) and elemental carbon (EC)), and ten elements (As, Cd, Cu, Zn, Pb, Cr, Mn, Fe, Ni, and Al) were analyzed. The ratio of PM1.0 to PM2.5 mass concentration was approximately 80%, and the coefficients of determination (r(2)) between PM1.0 and PM2.5 was higher than 0.95 at both sites. PM1.0 was primarily responsible for the chemical composition of PM2.5. At both sites, OC was the most prevalent component of PM1.0 and PM2.5, followed by NO3-, SO42-, NH4+, and EC. According to source apportionment of the PMF model, PM1.0 and PM2.5 were explained from nine and eight factors at both SL and BN, respectively. At both sites, the significantly larger proportion of the factors of PM1.0 and PM2.5 were secondary inorganic aerosol and the contributions of sources for PM2.5 in SL and BN were comparable to those of PM1.0. This study confirmed that (1) PM1.0 and PM2.5 showed similar characteristics at both SL and BN and (2) PM1.0 contributed significantly to the chemical composition and sources of PM2.5 both in SL and BN, implying that PM1.0-2.5 had a minor impact on PM2.5 in these two sites. Thus, though further studies are needed, it is likely that the current air quality management direction for PM2.5 is also effective in managing PM1.0 in Korea
Advanced Tellurium-Based Threshold Switching Devices for High-Density Memory Arrays
No full textHigh-density crossbar arrays based on storage class memory (SCM) are ideally suited to handle an exponential increase in data storage and processing as a central hardware unit in the era of AI-based technologies. To achieve this, selector devices are required to be co-integrated with SCM to address the sneak-path current issue that indispensably arises in such crossbar-type architecture. In this perspective, we first summarize the current state of tellurium-based threshold-switching devices and recent advances in the material, processing, and device aspects. We thoroughly review the physicochemical properties of elemental tellurium (Te) and representative binary tellurides, their tailored deposition techniques, and operating mechanisms when implemented in two-terminal threshold switching devices. Lastly, we discuss the promising research direction of Te-based selectors and possible issues that need to be considered in advance
Global existence of unique weak solutions and decay rates of Active model B with the logarithmic Cahn-Hilliard equation in Wiener space
No full textIn this paper, we deal with Active model B with the logarithmic Cahn-Hilliard equation. Under some smallness assumptions to initial data, we prove that there is a unique global-in-time solution which decays exponentially in time
SO2 resistance of V-based catalyst for Selective Catalytic Reduction of NOx with NH3 from WS2 Hydrogen-Reducing
No full text
Thrap3 promotes non-alcoholic fatty liver disease by suppressing AMPK-mediated autophagy
No full textHeavy-tailed Linear Bandit with Huber Regression
No full textLinear bandit algorithms have been extensively studied and have shown successful in sequential decision tasks despite their simplicity. Many algorithms however work under the assumption that the reward is the sum of linear function of observed contexts and a sub-Gaussian error. In practical applications, errors can be heavy-tailed, especially in financial data. In such reward environments, algorithms designed for sub-Gaussian error may underexplore, resulting in suboptimal regret. In this paper, we relax the reward assumption and propose a novel linear bandit algorithm which works well under heavy-tailed errors as well. The proposed algorithm utilizes Huber regression. When contexts are stochastic with positive definite covariance matrix and the (1 + ??)-th moment of the error is bounded by a constant, we show that the high-probability upper bound of the regret is O(???dT 1+ 1 ?? (log dT) 1+ ?? ?? ), where d is the dimension of context variables, T is the time horizon, and ?? ??? (0, 1]. This bound improves on the state-of-the-art regret bound of the Median of Means and Truncation algorithm by a factor of ???log T and ???d for the case where the time horizon T is unknown. We also remark that when ?? = 1, the order is the same as the regret bound of linear bandit algorithms designed for sub-Gaussian errors. We support our theoretical findings with synthetic experiments
Evaluations of patient-specific bolus fabricated by mold-and-cast method using computer numerical control machine tools
No full textThe patient-specific bolus fabricated by a mold-and-cast method using a 3D printer (3DP) and silicon rubber has been adopted in clinical practices. Manufacturing a mold using 3DP, however, can cause time delays due to failures during the 3D printing process. Thereby, we investigated an alternative method of the mold fabrication using computer numerical control (CNC) machine tools. Treatment plans were conducted concerning a keloid scar formed on the ear and nose. The bolus structures were determined in a treatment planning system (TPS), and the molds were fabricated using the same structure file but with 3DP and CNC independently. Boluses were then manufactured using each mold with silicone rubbers. We compared the geometrical difference between the boluses and the planned structure using computed tomography (CT) images of the boluses. In addition, dosimetric differences between the two measurements using each bolus and the differences between the measured and calculated dose from TPS were evaluated using an anthropomorphic head phantom. Geometrically, the CT images of the boluses fabricated by the 3DP mold and the CNC mold showed differences compared to the planned structure within 2.6 mm of Hausdorff distance. The relative dose difference between the measurements using either bolus was within 2.3%. In conclusion, the bolus made by the CNC mold benefits from a stable fabricating process, retaining the performance of the bolus made by the 3DP mold