51 research outputs found

    Experimental and numerical study of Pd/Ta and PdCu/Ta composites for thermocatalytic hydrogen permeation

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    The development of stable and durable hydrogen (H2) separation technology is essential for the effective use of H2 energy. Thus, the use of H2 permeable membranes, made of palladium (Pd), has been extensively studied in the literature. However, Pd has considerable constraints in large-scale applications due to disadvantages such as very high cost and H2 embrittlement. To address these shortcomings, copper (Cu) and Pd were deposited on Ta to fabricate a composite H2 permeable membrane. To this end, first, Pd was deposited on a tantalum (Ta) support disk, yielding 7.4 × 10−8 molH2 m−1 s−1 Pa−0.5 of permeability. Second, a Cu–Pd alloy on a Ta support was synthesized via stepwise electroless plating and plasma sputtering to improve the durability of the membrane. The use of Cu is cost-effective compared with Pd, and the appropriate composition of the PdCu alloy is advantageous for long-term H2 permeation. Despite the lower H2 permeation of the PdCu/Ta membrane (than the Pd/Ta membrane), about two-fold temporal stability is achieved using the PdCu/Ta composite. The degradation process of the Ta support-based H2 permeable membrane is examined by SEM. Moreover, thermocatalytic H2 dissociation mechanisms on Pd and PdCu were investigated and are discussed numerically via a density functional theory study

    Impact of Fatty Liver on Acute Pancreatitis Severity

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    Aim. Acute pancreatitis is typically a mild disease, but some patients develop severe courses. Fatty liver changes are seen in patients with acute pancreatitis, but its clinical significance has not been well-studied. We aimed to investigate the relationship between fatty liver and the severity of acute pancreatitis. Methods. Unenhanced CT images of patients with acute pancreatitis were retrospectively reviewed by a radiologist, and mean hepatic and splenic attenuation was measured in Hounsfield units (HU). Fatty liver was defined as mean hepatic/splenic HU<1. Results. Among 200 patients, fatty liver was found in 67 (33.5%) and nonfatty liver in 133 (66.5%). Compared with patients without fatty liver, the severity of pancreatitis and levels of serum C-reactive protein were higher in fatty liver patients. The prevalence of local complications, persistent organ failure, and mortality were also higher in patients with fatty liver. Even after adjusting for age, sex, body mass index, and cause of pancreatitis, fatty liver was significantly associated with moderately severe or severe acute pancreatitis. Conclusions. Fatty liver may play a prognostic role in acute pancreatitis. Fatty liver could be incorporated into future predictive scoring models

    Highly selective PtCo bimetallic nanoparticles on silica for continuous production of hydrogen from aqueous phase reforming of xylose

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    Hydrogen (H2) is a promising energy vector for mitigating greenhouse gas emissions. Lignocellulosic biomass waste has been introduced as one of the abundant and carbon-neutral H2 sources. Among those, xylose with its short carbon chain has emerged attractive, where H2 can be catalytically released in an aqueous reactor. In this study, a composite catalyst system consisting of silica (SiO2)-supported platinum (Pt)-cobalt (Co) bimetallic nanoparticles was developed for aqueous phase reforming of xylose conducted at 225 °C and 29.3 bar. The PtCo/SiO2 catalyst showed a significantly higher H2 production rate and selectivity than that of Pt/SiO2, whereas Co/SiO2 shows no activity in H2 production. The highest selectivity for useful liquid byproducts was obtained with PtCo/SiO2. Moreover, CO2 emissions throughout the reaction were reduced compared to those of monometallic Pt/SiO2. The PtCo bimetallic nanocatalyst offers an inexpensive, sustainable, and durable solution with high chemical selectivity for scalable reforming of hard-to-ferment pentose sugars

    Femtosecond laser driven high-flux highly collimated MeV-proton beam

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    金沢大学先端科学・社会共創推進機構Highlly collimated energetic protons whose energies are up to 4 MeV are generated by an intense femtosecond Titanium Sappheire laser pulse interacting with a 7.5, 12.5, and 25 μm-thick Polyimide tape target and 5 μm-thick copper target. We find no clear difference on the proton spectra from 7.5, 12.5, and 25 μm Polyimide tape target. The highest conversion efficiency from laser energy into protons of ∼3% is observed with a 7.5 μm thick Polyimide target. The quality of the proton beam is good enough to obtain a clear projection image of a mesh having 10 μm line and space structure, installed into the passage of the beam. We obtain clear vertical lines on the proton intensity profiles from the copper target, which are considered to be transferred from the surface of the copper target. From it, we can restrict the size of the proton emitting region to be ∼20μm. © 2008 American Institute of Physics.Embargo Period 12 month

    First-Principles Study of Pt-Based Bifunctional Oxygen Evolution &amp; Reduction Electrocatalyst: Interplay of Strain and Ligand Effects

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    We examined the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) of Pt-based Pt3M/Pt nanoalloy catalysts (where M represents a 3d transition metal) for bifunctional electrocatalysts using spin-polarized density functional theory calculations. First, the stability of the Pt3M/Pt catalyst was investigated by calculating the bulk formation energy and surface separation energy. Using the calculated adsorption energies for the OER/ORR intermediates in the modeled catalysts, we predicted the OER/ORR overpotentials and potential limiting steps for each catalyst. The origins of the enhanced catalytic reactivity in Pt3M/Pt catalysts caused by strain and ligand effects are explained separately. In addition, compared to Pt(111), the OER and ORR activities in a Pt3Ni/Ptskin catalyst with a Pt skin layer were increased by 13.7% and 18.4%, respectively, due to the strain and ligand effects. It was confirmed that compressive strain and ligand effects are key factors in improving the catalytic performance of OER/ORR bifunctional catalysts

    Effect of N‑Containing Functional Groups on CO<sub>2</sub> Adsorption of Carbonaceous Materials: A Density Functional Theory Approach

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    The amount of anthropogenic CO<sub>2</sub> emission keeps increasing worldwide, and it urges the development of efficient CO<sub>2</sub> capture technologies. Among various CO<sub>2</sub> capture methods, adsorption is receiving more interest, and carbonaceous materials are considered good CO<sub>2</sub> adsorbents. There have been many studies of N-containing carbon materials that have enhanced surface interaction with CO<sub>2</sub>; however, various N-containing functional groups existing in the carbon surface have not been investigated in detail. In this study, first-principle calculations were conducted for carbon models having various N-functional groups to distinguish N-containing heterogeneity and understand carbon surface chemistry for CO<sub>2</sub> adsorption. Among N-functional groups tested, the highest adsorption energies of −0.224 and −0.218 eV were observed in pyridone and pyridine groups, respectively. Structural parameters including bond angle and length revealed an exceptional hydrogen-bonding interaction between CO<sub>2</sub> and pyridone group. Charge accumulation on CO<sub>2</sub> during interaction with pyridine-functionalized surface was confirmed by Bader charge analysis. Also, the peak shift of CO<sub>2</sub> near Fermi level in the DOS calculation and the presence of HOMO on pyridinic-N in the frontier orbital calculation determined that the interaction of pyridinic-N is weak Lewis acid–base interaction by charge transfer. Furthermore, adsorption energies of N<sub>2</sub> were calculated and compared to those of CO<sub>2</sub> to find its selective adsorption ability. Our results suggest that pyridone and pyridine groups are most effective for enhancing the interaction with CO<sub>2</sub> and have potential for selective CO<sub>2</sub> adsorption

    Development of a new lactic acid bacterial inoculant for fresh rice straw silage

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    Objective Effects of newly isolated Lactobacillus plantarum on the fermentation and chemical composition of fresh rice straw silage was evaluated in this study. Methods Lactic acid bacteria (LAB) from good crop silage were screened by growing them in MRS broth and a minimal medium with low carbohydrate content. Selected LAB (LAB 1821) were Gram-positive, rods, catalase negative, and were identified to be Lactobacillus plantarum based on their biochemical characteristics and a 16S rRNA analysis. Fresh rice straw was ensiled with two isolated LAB (1821 and 1841), two commercial inoculants (HM/F and P1132) and no additive as a control. Results After 2 months of storage at ambient temperature, rice straw silages treated with additives were well-preserved, the pH values and butyric and acetic acid contents were lower, and the lactic acid content and lactic/acetic acid ratio were higher than those in the control (p0.05) effect on acid detergent fiber or neutral detergent fiber contents. Crude protein (CP) content and in vitro DM digestibility (IVDMD) increased after inoculation of LAB 1821 (p<0.05). Conclusion LAB 1821 increased the CP, IVDMD, lactic acid content and ratio of lactic acid to acetic acid in rice straw silage and decreased the pH, acetic acid, NH3-N, and butyric acid contents. Therefore, adding LAB 1821 improved the fermentation quality and feed value of rice straw silage

    Boosting the Transesterification Reaction by Adding a Single Na Atom into g-C<sub>3</sub>N<sub>4</sub> Catalyst for Biodiesel Production: A First-Principles Study

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    Increasing environmental problems and the energy crisis have led to interest in the development of alternative energy. One of the most promising sustainable alternatives to fossil fuel is biodiesel which is typically produced from the transesterification of refined vegetable oils using a homogeneous base catalyst. However, the current process limitations and steep production costs associated with the use of homogeneous catalysts have limited the global-wide acceptance of biodiesel. Heterogeneous catalysts have been considered suitable alternatives, but they still suffer from low catalytic activity. In this study, by using density functional theory (DFT) calculations, we examined the electronic and catalytic activity of the single Na-doped graphitic carbon nitrides (indicated by Na-doped g-C3N4) toward the efficient biodiesel (acetic acid methyl ester) production via the transesterification of triglyceride (triacetin). Our DFT calculation on reaction energetics and barriers revealed the enhancement of biodiesel productivity in the Na-doped catalyst compared to the pristine g-C3N4 catalyst. This was related to the large reduction of the barrier in the rate-limiting step. In addition, we investigated the acidity/basicity and electron distribution and density of state for the Na-doped and pristine g-C3N4 catalysts to better understand the role of the Na atom in determining the transesterification reaction. This study highlights the importance of the dopant in a g-C3N4 catalyst in determining the transesterification reaction, which may open new routes to improve biodiesel production

    Controller Design and Experiment for Tracking Mount of Movable SLR, ARGO-M

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    Controller design procedure for prototype tracking mount of Movable SLR (Satellite Laser Ranging), ARGO-M is presented. Tracking mount of ARGO-M is altitude-azimuth type and it has two axes of elevation and azimuth to control its position. Controller consists of velocity and acceleration feed-forward controller, position controller at outer loop, velocity controller at inner loop. There are two kinds of position control modes. One is the pointing mode to move from one position to the other position as fast as possible and the other one is tracking mode to follow SLR trajectory as precise as possible. Because the requirement of tracking accuracy is less than 5 arcsec and it is very tight error budget, a sophisticated controller needs to be prepared to meet the accuracy. Especially, ARGO-M is using the cross-roller bearing at each axis to increase the mechanical accuracy, which requires add-on controller DOB (Disturbance observer) to suppress friction load and low frequency disturbances. The pointing and tracking performance of the designed controller is simulated and visualized using MATLAB/ Simulink and SimMechanics and the experimental results using test are presented as well
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