Experimental study of centrifugal compressor vaneless diffuser width

Seven different vaneless diffuser designs for a centrifugal compressor, varying only in diffuser width, were studied experimentally. The studied diffuser widths versus impeller exit width were 1.0, 0.903, 0.854, and 0.806. Three of the narrowed diffusers had the width reduced from the hub and shroud divided evenly, and the three others had the width reduced only from the shroud. The total and static pressures, the total temperature and the flow angles at the diffuser inlet and outlet were measured at the design rotational speed with three different mass flows. The impeller and diffuser performance was studied along with the axial distributions of flow angles and velocities in the diffuser. The results revealed that the pinch improved the compressor stage and impeller performance but deteriorated the diffuser performance. The pinch clearly decreased the secondary flow region present near the shroud. The pinch implemented in the shroud is more beneficial than pinch divided between the hub and the shroud. In order to obtain the beneficial effects of pinch, the pinch should be sufficient. However, excessive pinch deteriorates the compressor performance.     

Palladium(II)‐Catalyzed Aerobic Intermolecular Cyclization of Acrylic Acid with Alkenes to α‐Methylene‐γ‐butyrolactones

The methodology in this article is a palladium(II)/copper(II)‐ or palladium(II)‐catalyzed intermolecular cyclization of acrylic acid with alkenes to produce α‐methylene‐γ‐butyrolactone derivatives using molecular oxygen as an environmentally benign oxidant. In this system, the carboxylato, especially trifluoroacetato, or trimethylacetato ligand, plays a quite important role to afford a high catalytic activity by suppressing the deposition of palladium(0) black.     

Void Growth Behavior in ULSI Cu Interconnections by Grain-Boundary Diffusion Simulation

The behavior of void growth in ultra-large-scale integration Cu interconnections has been investigated by grain-boundary diffusion simulation to confirm the effectiveness of the high-pressure reflow process for suppressing stress-induced voiding. Void growth was simulated by combining stress analysis and atomic flux analysis. The former was calculated by the finite-element method (FEM), and the latter was calculated by an unusual FEM in which grain boundaries were defined as elements. From the results of void growth analysis, we found that voids tend to disappear during the isochronal annealing step and that the void shrinkage rate can be increased by two to three times by applying pressure of 150 MPa compared with normal-pressure annealing. From the simulation results, it can be conjectured that the high-pressure reflow process is effective for eliminating voids in via holes of Cu interconnections.     

Reflow Phenomenon Analysis of Large Scale Integrated Cu Interconnections in Via Holes by Viscoelastic Deformation Simulation

The reflow phenomenon of Cu interconnections deposited over via holes was analyzed by viscoelastic deformation simulation using a finite-element method to clarify the embedding mechanism of Cu interconnections into via holes in a novel dual-damascene fabrication technology, which combined sputter deposition and high-pressure annealing. Cu is considered to be a viscoelastic body, and the stress distribution and deformation behavior of Cu interconnections were calculated. As a result, the deformation behavior of the Cu interconnections exhibited close agreement between the calculated and the observed values. From our series of results, we inferred that Cu interconnections are embedded into via holes by the creep deformation mechanism defined in this study during the high-pressure annealing process.     

Optimal operation of a photovoltaic generation-powered hydrogen production system at a hydrogen refueling station

As the popularity of fuel cell vehicles continues to rise in the global market, production and supply of low-carbon hydrogen are important to mitigate CO₂ emissions. We propose a design for a hydrogen refueling station with a proton exchange membrane electrolyzer (PEM-EL)-based electrolysis system (EL-System) and photovoltaic generation (PV) to supply low-carbon hydrogen. Hydrogen is produced by the EL-System using electricity from PV and the power grid. The system was formulated as a mixed integer linear programming (MILP) model to allow analysis of optimal operational strategies. Case studies with different objective functions, CO₂ emission targets, and capacity utilization of the EL-System were evaluated. Efficiency characteristics of the EL-System were obtained through measurements. The optimized operational strategies were evaluated with reference to three evaluation indices: CO₂ emissions, capacity utilization, and operational cost of the system. The results were as follows: 1) Regardless of the objective function, the EL-System generally operated in highest efficiency state, and optimal operation depended on the efficiency characteristics of the EL-System; 2) mitigation of CO₂ emissions and increase in capacity utilization of the EL-System required trade-offs; and 3) increased capacity utilization of the EL-System showed two opposing effects on hydrogen retail price.     

Toward elucidating the full spectrum of mite allergens--state of the art

Our research has focused on the molecular design of immunotherapeutic vaccines and the advancement of mite-allergy diagnosis. Here, we describe the research history of the major group 1 and group 2 allergens, immunoelectrophoretic analyses covering the complete spectrum of mite allergens, our results on allergens with distinctive characteristics (a conjunctival congestion-eliciting antigen [LM2], an immunotherapeutic antigen [HM2] with high efficacy and without definite adverse reactions, and a potent T-cell stimulatory antigen [HM1] with secretion of IFN-gamma), the full spectrum and immunochemical properties of the major and other important mite allergens (including our newly described allergens: a pan-allergen [tropomyosin, group 10], a potent T-cell stimulatory allergen [M-177, apolipophorin, group 14] and its peptide fragments Mag1 and Mag3, a moderate IgE-binding allergen [gelsolin/villin, group 16], an EF-hand Ca2+-binding allergen [group 17], and a less IgE-binding allergen [heat shock protein 70]), and prospects for the development of immunotherapeutic and diagnostic agents.     

Positive Effect of Constant Leading Power Factor Operation of PV in Power System

A voltage rise problem in distribution networks has been discussed as the foremost concern with respect to the spread of large numbers of photovoltaic systems. We focus on the latent ability of the present distribution network and photovoltaic systems to find a low‐cost solution to the problem and consider a solution to mitigate the voltage rise using the photovoltaic system's constant leading power factor operation. Previously, based on simulations using an aggregated model of a real distribution network, we proposed that a combination of a photovoltaic system's constant leading power factor operation and LDC makes it possible to maintain the line voltage and LTC tap position adequately. In this paper, additionally, we confirm some effects of the proposed method in an aggregated model of a distribution network and a trunk power system. One of them is that the proposed method reduces the frequency of restricting output power from photovoltaic systems and changing the LTC and SVR tap position, although photovoltaic systems rapidly fluctuate. Another is that the proposed method cannot make a significant impact on a trunk power system in a voltage class exceeding 6.6 kV.     

Regulation of Polyunsaturated Fatty Acid Biosynthesis by Seaweed Fucoxanthin and Its Metabolite in Cultured Hepatocytes

The effects of a seaweed carotenoid, fucoxanthin, and its physiological metabolite, fucoxanthinol, on the biosynthesis of polyunsaturated fatty acids (PUFA) were investigated using cultured rat hepatoma BRL‐3A. The metabolism of α‐linolenic acid (18:3n‐3) was suppressed by the addition of these carotenoids, resulting in a decrease in the content of eicosapentaenoic acid (20:5n‐3), which suggested a down‐regulation of metabolic enzymes such as fatty acid desaturase and elongase. An increase in the content of docosahexaenoic acid (22:6n‐3), as observed in previous studies in vivo, might be a buffering action to maintain the membrane fluidity. The suppressive effect of fucoxanthinol on ?6 fatty acid desaturase was not at the level of gene expression but due to specific modifications of the protein via a ubiquitin–proteasome system. A proteomic analysis revealed several factors such as phosphatidylethanolamine‐binding protein that might be involved in the observed action of fucoxanthin. These findings will contribute to studies on the elucidation of the precise molecular mechanisms underlying the regulation of PUFA biosynthesis by fucoxanthin.     

Computing quadratic entropy in evolutionary trees

We note here that quadratic entropy, a measure of biological diversity introduced by C.R. Rao, is a variant of the weighted Wiener index, a graph invariant intensively studied in mathematical chemistry. This fact allows us to deduce some efficient algorithms for computing the quadratic entropy in the case of given tip weights, which may be useful for community biodiversity measures. Furthermore, on ultrametric phylogenetic trees, the maximum of quadratic entropy is a measure of pairwise evolutionary distinctness in conservation biology, introduced by S. Pavoine. We present an algorithm that maximizes this quantity in linear time, offering a significant improvement over the currently used quadratic programming approaches.     

XAFS and XRD Analysis of Ceria–Zirconia Oxygen Storage Promoters for Automotive Catalysts

Three types of CeO₂–ZrO₂ (Ce:Zr = 1:1 molar ratio) compounds with different oxygen storage/release capacity (OSC) were characterized by means of the Ce K-edge and Zr K-edge XAFS. In order to investigate the relationship between the OSC and local structure, the quantitative EXAFS curve-fitting analysis was applied. By enhancing the homogeneity of the Ce and Zr atoms in the CeO₂–ZrO₂ solid solution, the OSC performance increased. Additionally, from the XRD analysis, the homogeneous CeO₂–ZrO₂ solid solution has an ordered cation arrangement, and exhibits the highest OSC. The crystal structure of this CeO₂–ZrO₂ solid solution is usually termed as “κ-CeZrO₄ phase”. However, the OSC performance of κ-CeZrO₄ degrades upon a high-temperature treatment under an oxidative atmosphere. The fresh κ-CeZrO₄ was aged at 973, 1,273 and 1,473 K under an oxidative atmosphere, respectively. The OSC performance deteriorated as: the fresh sample ≈973 > 1,273 > 1,473 K-aged samples. We also found that, if the temperature was beyond 1,273 K, the Ce/Zr ordered arrangement would collapse and the local structure around Ce and Zr ions would also changed remarkably. These results indicated that OSC was strongly dependent on its atomic structure.