Air-coupled, focused ultrasonic dispersion spectrum reconstruction in plates

This paper presents and demonstrates a noncontact method for measuring the Lamb wave dispersion spectrum of a plate. Noncontact air-coupled source and receive transducers are used with line-focus mirrors and 50–700 kHz broadband apparatus for simultaneous measurement over a broad spectrum of refractive angles and multiple guided modes. Broadband, wide-angle wave forms are measured as a function of position. The Fourier transform of these wave forms from the t – x domain to the v – k domain gives an approximate spectrum of the dispersion relation. We measure the dispersion spectra of Lucite™, aluminum, balsa wood, and a carbon fiber epoxy laminate, and show that the measured spectra agree well with the dispersion relation calculated from Lamb wave theory

Real Wage and Nominal Shock: Evidence from Pacific-Rim Countries

This paper examines aggregate real-wage responses to nominal shocks in four Pacific-rim countries utilizing a vector autoregression (VAR) framework. In this study, positive real-wage responses are found in Japan and New Zealand whereas negative responses are found in Australia and Korea. In the transmission of nominal shocks to real economic activities, the findings show a sticky-price model to be more important in Japan and New Zealand, while a sticky-wage model plays the more dominant role in Australia and Korea. Copyright International Atlantic Economic Society 2005E4, E5,

Unionization, Unemployment, and Growth in Korea: A Cointegration Approach

Thanks to numerous empirical research studies, a general consensus has been reached on the effects of labor unionization on the economy such as unemployment and economic growth (GDP). However, most of the previous research examines the effects of labor unionization on the U.S. and U.K. labor markets using multiple regression models. By applying different statistical tools (multivariate cointegration analysis and vector error correction model) to Korean data, this paper finds: (1) there is a long-run equilibrium linkage among unionization, unemployment and economic growth; and (2) unionization unidirectionally and significantly Granger-causes unemployment and economic growth. Copyright International Atlantic Economic Society 2005J, J3,

The Impact of Age and Health on Vehicle Choices among Elders

Age, Driving, Family burden, Health, Vehicle types,

Nickel nanoparticles in hydrogen transfer reactions

The transfer hydrogenation of organic compounds is a much safer and more environmentally benign process than reduction reactions involving molecular hydrogen, metal hydrides, or dissolving metals. In transfer hydrogenation, 2-propanol is often preferred as the source of hydrogen because it is cheap, easy to remove, and environmentally friendly. This class of transformation has been mostly pursued through the use of expensive noble metals, such as Ru, Pd, and so forth; research involving cheaper catalytically active metals has been relatively neglected. On the other hand, alcohols have recently emerged as desirable alkylating agents, a useful alternative to organic halides, in reactions of hydrogen autotransfer, also known as the “borrowing of hydrogen” methodology. For instance, the α-alkylation of ketones with alcohols is an atom-efficient process that produces water as the only byproduct in the presence of a noble metal catalyst. Hydrogen autotransfer is also successful in the synthesis of amines through a reductive aza-Wittig reaction, which involves an iminophosphorane and primary alcohol under iridium catalysis. The in situ oxidation−Wittig olefination of primary alcohols with stabilized phosphorus ylides is a commonly practiced method in organic synthesis that precludes the necessity of handling aldehydes. These reactions are normally performed in one pot but sequentially; thus the course of the alcohol oxidation needs monitoring before the ylide addition. In this Account, we describe the development of our discovery that nickel(0), in the form of nanoparticles, can replace the more expensive noble metals in both transfer hydrogenation and hydrogen autotransfer reactions. These nanoparticles were found to catalyze the transfer hydrogenation of olefins and carbonyl compounds, as well as the reductive amination of aldehydes, with 2-propanol as the hydrogen donor. All reactions proceeded in the absence of base, and the catalyst could be easily and successfully reutilized in the case of the carbonyl compounds. The catalyst was fully characterized, and the reaction mechanism, kinetics, and heterogeneous nature of the process were established through a variety of experiments. Moreover, the nickel nanoparticles enabled the activation of primary alcohols for the α-alkylation of ketones and reductive aza-Wittig reaction, with the latter leading to secondary amines. For the first time, these two reactions were achieved with a catalyst that was not one of the noble metals. We also observed that nickel nanoparticles can activate alcohols in the presence of phosphorus ylides. In this case, although the autotransfer of hydrogen failed, the reaction could be used as a key tool to construct carbon−carbon double bonds. In this respect, we describe the one-pot synthesis of stilbenes from alcohols through a Wittig-type olefination reaction promoted by nickel nanoparticles. We report a wide range of polymethoxylated and polyhydroxylated stilbenes, including the naturally occurring polyphenol resveratrol. The utility of the nickel nanoparticles was exceptional in all of the aforementioned reactions when compared with other forms of nickel, including Raney nickel.This work was generously supported by the Spanish Ministerio de Ciencia e Innovación (MICINN; Grant No. CTQ2007-65218 and Consolider Ingenio 2010-CSD2007-00006) and the Generalitat Valenciana (Grant No. PROMETEO/2009/039 and FEDER)