Micro void growth in NiSnP layer between (Cu,Ni)<Subscript>6</Subscript>Sn<Subscript>5</Subscript> intermetallic compound and Ni<Subscript>3</Subscript>P by higher reflow temperature and multiple reflow

This study examines the growth mechanism of micro void called “Kirkendall voids” within NiSnP nano-crystalline layer between (Cu,Ni)₆Sn₅ intermetallic compound (IMC) and Ni₃P formed during two double reflow processes. The micro voids in NiSnP layer formed at the first reflow grow faster under the elevated reflow temperature than under the standard lead-free reflow, during the second reflow process. Despite the diffusion barrier Ni(P), the inward diffusion flux of Sn from (Cu,Ni)₆Sn₅ into NiSnP layer is much slower than the outward flux of Sn from NiSnP layer into Ni₃P, consequently leaving voids as NiSnP thickness increases. Results show that the thermal activation energy through the elevated reflow temperature has a higher influence in micro void growth than the number of reflows for the inward and outward diffusion flux difference of Sn within NiSnP layer in electroless Ni(P)/immersion Au and SnAgCu reaction system.     

Characteristics and economic evaluation of a CO2-capturing repowering system with oxy-fuel combustion for utilizing exhaust gas of molten carbonate fuel cell (MCFC)

A scale of 2.4 MW molten carbonate fuel cell (MCFC) was taken to construct a high-efficiency and economic power generation system without CO₂ emission for utilizing its exhaust gas. A conventional steam turbine power generation system (STPS) is evaluated and the net generated power (NGP) is estimated to be only 131 kW and the STPS is not economically feasible. A CO₂-caputuring repowering system is proposed, where low temperature steam produced at heat recovery steam generator (HRSG) by using the MCFC exhaust gas is utilized as a main working fluid of a gas turbine, and the temperature of the steam is raised by combusting fuel in a combustor by using pure oxygen, not the air. It is estimated that NGP of the proposed system is 253 kW, and CO₂ reduction amount is 583 t-CO₂/y, compared to 302 t-CO₂/y for the STPS and that the proposed system becomes economically feasible if a CO₂ emission credit higher than 20 $/t-CO₂ can be granted. It is also estimated, when its turbine inlet temperature is increased from 850 °C to 1000 °C, CO₂-capturing is not cost-consuming but becomes to be profitable, owing to improved power generation characteristics.     

Growth inhibition of foodborne pathogens by kimchi prepared with bacteriocin-producing starter culture

Kimchi (starter kimchi) was prepared with Leuconostoc citreum GJ7, a bacteriocin producer, with the objective of preventing growth and/or survival of foodborne pathogens such as Escherichia coli O157:H7, Salmonella Typhi, and Staphylococcus aureus. Numbers of the pathogens inoculated to 5.41 to 5.63 log CFU/mL into the filtrate of freshly made starter kimchi remained stable for the first 12 h of incubation at 10 °C. Reductions of 2.69, 2.88, and 3.42 log CFU/mL were observed 48 h after inoculation with E. coli O157:H7, S. Typhi, and S. aureus, respectively. Use of the bacteriocin-producing starter culture for kimchi fermentation significantly reduced the numbers of pathogens in the filtrate. Reductions of 3.85, 4.45, and 5.19 log CFU/mL were observed 48 h after inoculation for E. coli O157:H7, S. Typhi, and S. aureus, respectively. Presumably, the antimicrobial activity came from the ingredients of kimchi such as sulfur-containing compounds, low pH (approximately pH 4.5) produced by the conversion of sugars into organic acids and the bacteriocins potentially produced by lactic acid bacteria (LAB), such as kimchicin GJ7. Together, these data suggest that addition of a starter culture capable of producing bacteriocins could serve as a strategy to protect the fermented product from delivering pathogens upon consumption and that the kimchi filtrate itself may be used as a food preservative. Practical Application: The adaptation of the starter fermentation into kimchi induced a faster die off of the pathogens as compared to natural fermentation. The in situ bateriocin-production by Leuc. citreum GJ7 in kimchi would act with antimicrobial kimchi ingredients in a synergistic manner to protect the fermented product from delivering pathogens upon consumption.     

Organocatalytic Asymmetric Mannich Reactions of 5H‐Oxazol‐4‐ones: Highly Enantio‐ and Diastereoselective Synthesis of Chiral α‐Alkylisoserine Derivatives

The first organocatalytic Mannich reaction of 5H‐oxazol‐4‐ones with various readily prepared aryl‐ and alkylsulfonimides has been developed. Two commercially available pseudoenantiomeric Cinchona alkaloids‐derived tertiary amine/ureas have been demonstrated as the most efficient catalysts to access the opposite enantiomers of the Mannich products with equally excellent enantio‐ and diastereoselectivities. From the Mannich adducts, important α‐methyl‐α‐hydroxy‐β‐amino acid derivatives, such as the α‐methylated C‐13 side chain of taxol and taxotere, can be conveniently prepared.     

Investigation of possibility of developing high-efficiency heat-conducting system of electrical insulation for turbo generators with air and hydrogen cooling

The results of comparative tests of the main electrophysical properties of a new type of high-efficiency heat-conducting insulation for turbo generators with air and hydrogen cooling as compared to the traditional insulation are presented. It is shown that the addition of modified varnish with a high thermal conductivity coefficient to the insulation material does not yield any deterioration of its electrical properties.     

On the lateral instability of a thin beam under periodic bending loads

The lateral instability of a thin beam under periodic bending loads was investigated. Physical evidences of the instability were observed previously by experiments. But an analytical study has not been reported. The object of this study is to demonstrate the nature and existence of dynamic lateral instability. The harmonic balance method is applied to bifurcation modes which result from the stability change of torsional mode of a beam and then compared with numerical simulations. It is found, in a certain frequency range, that a small bending load results in the lateral instability when damping is small. Inha University     

Cathode catalyst layer using supported Pt catalyst on ordered mesoporous carbon for direct methanol fuel cell

The development of a cathode catalyst layer based on a supported Pt catalyst using an ordered mesoporous carbon (OMC) for direct methanol fuel cell is reported. An OMC with a mesopore structure between hexagonally arranged carbon nanorods is prepared using a template method. Platinum nanoparticles are supported on the OMC (Pt/OMC) with high metal loading of 60 wt.%. Compositional and morphological variations are made by varying the ionomer content and by compressing the catalyst layer to detect a parameter that determines the power performance. Increase in power density with decrease in the volume fraction of ionomer in the agglomerate comprising the Pt/OMC and the ionomer indicates that mass transport through the ionomer phase governs the kinetics of oxygen reduction. Impedance spectroscopic analysis suggests that a significant mass-transport limitation occurs at high ionomer content and in the compressed cathode. The power density of the optimum cathode layer, which employs a Pt/OMC catalyst with a Pt loading of 2 mg cm⁻², is greater than that of a catalyst layer with 6 mg cm⁻² Pt-black catalyst at a voltage higher than 0.4 V. This would lead to a significant reduction in the cost of the membrane electrode assembly.     

EuroPriSe Trust Certification

Trust marks are well known arbiters of trust. To be successful, sustainable and trustworthy the underlying certification scheme ought to implement specific requirements including transparent criteria and procedures verifying the actual trustworthiness of the recipient by an independent certification authority. The concept of an explicit trust certification scheme is set forth in this article using the example of EuroPriSe, the European Privacy Seal for IT products and IT-based services.