An efficient microwave-assisted Suzuki reaction using Pd/MCM-41 and Pd/SBA-15 as catalysts in solvent-free condition

Palladium catalysts, Pd/MCM-41 and Pd/SBA-15 were prepared by impregnation of an aqueous solution of [Pd(NH₃)₄]Cl₂ on MCM-41 and SBA-15. Palladium contents of Pd/MCM-41 and Pd/SBA-15 are 8.4% and 8.7%, respectively. It has been shown that these catalysts are very suitable to microwave-assisted Suzuki reactions under solvent-free condition. It is also found that the base additives for this reaction are K₂CO₃, Cs₂CO₃ or CsF. Thus, phenylboronic acid and phenyl iodide with Pd/MCM-41 produce biphenyl by microwave irradiation for 10 min in 97.4% yield. Phenyl bromide, instead of phenyl iodide, also proceeds the reaction with phenylboronic acid using Pd/MCM-41 or Pd/SBA-15 yielding biphenyl by microwave irradiation for 10 min in excellent yield. Whereas the reaction of phenyl chloride with phenylboronic acid gives poor yield in same condition. Various aryl iodides and aryl bromides are tested. In this paper our recent results of microwave-assisted Suzuki reaction using Pd/MCM-41 and Pd/SBA-15 under solvent-free condition are described.     

Interior-architectured ZnO nanostructure for enhanced electrical conductivity via stepwise fabrication process

Fabrication of ZnO nanostructure via direct patterning based on sol-gel process has advantages of low-cost, vacuum-free, and rapid process and producibility on flexible or non-uniform substrates. Recently, it has been applied in light-emitting devices and advanced nanopatterning. However, application as an electrically conducting layer processed at low temperature has been limited by its high resistivity due to interior structure. In this paper, we report interior-architecturing of sol-gel-based ZnO nanostructure for the enhanced electrical conductivity. Stepwise fabrication process combining the nanoimprint lithography (NIL) process with an additional growth process was newly applied. Changes in morphology, interior structure, and electrical characteristics of the fabricated ZnO nanolines were analyzed. It was shown that filling structural voids in ZnO nanolines with nanocrystalline ZnO contributed to reducing electrical resistivity. Both rigid and flexible substrates were adopted for the device implementation, and the robustness of ZnO nanostructure on flexible substrate was verified. Interior-architecturing of ZnO nanostructure lends itself well to the tunability of morphological, electrical, and optical characteristics of nanopatterned inorganic materials with the large-area, low-cost, and low-temperature producibility.     

Effects of amplitude modulation on perception of wind turbine noise

Wind turbine noise is considered to be easily detectable and highly annoying at relatively lower sound levels than other noise sources. Many previous studies attributed this characteristic to amplitude modulation. However, it is unclear whether amplitude modulation is the main cause of these properties of wind turbine noise. Therefore, the aim of the current study is to identify the relationship between amplitude modulation and these two properties of wind turbine noise. For this investigation, two experiments were conducted. In the first experiment, 12 participants determined the detection thresholds of six target sounds in the presence of background noise. In the second experiment, 12 participants matched the loudness of modified sounds without amplitude modulation to that of target sounds with amplitude modulation. The results showed that the detection threshold was lowered as the modulation depth increased; additionally, sounds with amplitude modulation had higher subjective loudness than those without amplitude modulation.     

Numerical modeling and simulations of active direct methanol fuel cell (DMFC) systems under various ambient temperatures and operating conditions

Direct methanol fuel cells (DMFCs) are potential candidates for portable backup power generation and auxiliary power units owing to their advantageous features, such as ease of fuel storage and delivery. Optimizing each component of a DMFC system is critical to improving the overall system performance and power density. This paper presents an active DMFC system model, in which a one-dimensional DMFC stack model is combined with major system components, including fuel and water tanks, liquid–gas separator, heat exchangers, pumps, and blowers. The model is implemented using a commercial flow-sheet simulator, ASPEN-HYSYS, and then applied to an active DMFC system to analyze the effects of the DMFC operating parameters and heat management. Special emphasis is placed on establishing active control strategies for the DMFC stack temperature, methanol crossover rate, and water recovery by optimizing the system components and operating conditions. Overall, this study helps identify innovative active DMFC system designs and configurations.     

An augmented EDA with dynamic diversity control and local neighborhood search for coevolution of optimal negotiation strategies

In this paper, we present an estimation of distribution algorithm (EDA) augmented with enhanced dynamic diversity controlling and local improvement methods to solve competitive coevolution problems for agent-based automated negotiations. Since optimal negotiation strategies ensure that interacting agents negotiate optimally, finding such strategies—particularly, for the agents having incomplete information about their opponents—is an important and challenging issue to support agent-based automated negotiation systems. To address this issue, we consider the problem of finding optimal negotiation strategies for a bilateral negotiation between self-interested agents with incomplete information through an EDA-based coevolution mechanism. Due to the competitive nature of the agents, EDAs should be able to deal with competitive coevolution based on two asymmetric populations each consisting of self-interested agents. However, finding optimal negotiation solutions via coevolutionary learning using conventional EDAs is difficult because the EDAs suffer from premature convergence and their search capability deteriorates during coevolution. To solve these problems, even though we have previously devised the dynamic diversity controlling EDA (D²C-EDA), which is mainly characterized by a diversification and refinement (DR) procedure, D²C-EDA suffers from the population reinitialization problem that leads to a computational overhead. To reduce the computational overhead and to achieve further improvements in terms of solution accuracy, we have devised an improved D²C-EDA (ID²C-EDA) by adopting an enhanced DR procedure and a local neighborhood search (LNS) method. Favorable empirical results support the effectiveness of the proposed ID²C-EDA compared to conventional and the other proposed EDAs. Furthermore, ID²C-EDA finds solutions very close to the optimum.     

A planar catalytic combustion sensor using nano-crystalline F-doped SnO2 as a supporting material for hydrogen detection

A planar catlytic combustion gas sensor based on Pd/Pt catalyst supported on F-doped SnO₂ nano-crystalline materials has been designed and fabricated for hydrogen detection. The sensor consists of platinum heaters on an alumina plate coated with a catalytic layer and compensating layer. This sensor exhibited better performance than that of the sensors employing sensing material of Pd/Pt catalyst on γ-Al₂O₃ and of Pd/Pt catalyst on nano-crystalline SnO₂. The detection limit of the sensor at 370 °C is in the concentration range of 0.5–5% (v/v), with an excellent linearity of signal voltage to the hydrogen gas concentration.     

Soldering method using longitudinal ultrasonic

An efficient ultrasonic soldering method of inserting the metal bumps into the solder is investigated in this work for electronic packaging. The effects of the process parameters such as the ultrasonic frequency, amplitude, dimensions of the metal bump and solder are analyzed through the viscoelastic modeling. The ultrasonic soldering was conducted using the Cu and Au bumps, and the acceptable bonding condition was determined from the tensile strength. Localized heating of the solder was achieved and the stirring action due to the ultrasonic influences the bond strength and microstructure of the eutectic solder. Since higher temperature is obtained with smaller solder, the proposed ultrasonic soldering method appears to be applicable to the high-density electronic packaging.     

Ruthenium(II)‐ or Rhodium(III)‐Catalyzed Grignard‐Type Addition of Indolines and Indoles to Activated Carbonyl Compounds

The ruthenium(II)‐ or rhodium(III)‐catalyzed pyrimidinyl‐directed Grignard‐type C−H additions of N‐heterocycles with activated aldehydes and ketones are described. A cationic ruthenium catalyst and sodium acetate additive in dichloroethane as solvent were found to be optimal catalytic system for the construction of C‐7 alkylated indolines. In sharp contrast, a cationic rhodium complex allows the generation of C‐2 alkylated indoles and pyrroles as well as C‐1 alkylated carbazoles. The site‐selective C−H functionalization of these heterocyclic scaffolds could be an important asset towards the development of novel bioactive compounds.

     

Combined Application of Antibrowning,Heat Treatment and Modified‐Atmosphere Packaging to Extend the Shelf Life of Fresh‐Cut Lotus Root

This work aimed to determine the effects of different concentrations of antibrowning treatments (that is, distilled water [DW], 1% ascorbic acid [AA], 0.5% chamomile [CM], and 1% AA + 0.5% CM) and heat‐treatment (55 °C for 45 s) combined with packaging under 4 different modified‐atmosphere gas compositions (that is, air, vacuum, 100% CO₂, 50% CO₂/50% N₂) on the quality and microbiological characteristics of fresh‐cut lotus root. The quality characteristics (that is, color, weight loss, texture, pH, polyphenoloxidase activity, and total phenolic content) of the AA + CM‐dipped sample in 100% CO₂ packaging were maintained significantly better than those of the other samples (P < 0.05). The microbiological counts observed in the DW‐dipped sample during storage were higher than those of the AA, CM, and AA + CM samples, and heat‐treatment retarded the microbiological deterioration of fresh‐cut lotus root. Therefore, the results revealed that dipping in an antibrowning treatment (AA + CM), and 100% CO₂ MAP with heat treatment effectively extend the shelf life of fresh‐cut lotus root to 21 d at 5 °C.