Analysis of the effects of main design parameters variation on the vibration characteristics of a vehicle sub-frame

In the design process of an automobile part, several analysis methods are usually used to evaluate the performance of the part. However, most automobile design engineers do not directly use CAE (computer aided engineering) tools since specific skills are required to obtain practical results. Moreover, CAE requires a huge amount of computation time and cost. To resolve these problems, a new design approach, termed first order analysis (FOA), has been proposed. In this paper, the FOA technique is employed to design a vehicle sub-frame. An equivalent model of the vehicle subframe which only consists of beam elements is proposed and the modal properties obtained with the model are compared to those obtained with a full scale finite element model. The effects of some parameter variations on the modal characteristics of the vehicle sub-frame are investigated by employing the FOA equivalent model. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Hong Hee Yoo graduated from the Department of Mechanical Design and Production Engineering at Seoul National University in 1980 and received his Master’s degree from the same department in 1982. He received his Ph.D. degree in 1989 from the Department of Mechanical Engineering and Applied Mechanics at the University of Michigan at Ann Arbor, U.S.A. He is currently working as a professor in the School of Mechanical Engineering in Hanyang University, Seoul, Korea.     

Characteristics of test and maintenance human errors leading to unplanned reactor trips in nuclear power plants

The test and maintenance (T&M) human errors involved in unplanned reactor trip events in Korean nuclear power plants were analyzed according to James Reason's basic error types, and the characteristics of the T&M human errors by error type were delineated by the distinctive nature of major contributing factors, error modes, and the predictivity of possible errors. Human errors due to a planning failure where a work procedure is provided are dominated by the activities during low-power states or startup operations, and human errors due to a planning failure where a work procedure does not exist are dominated by corrective maintenance activities during full-power states. Human errors during execution of a planned work sequence show conspicuous error patterns; four error modes such as ‘wrong object’, ‘omission’, ‘too little’, and ‘wrong action’ appeared to be dominant. In view of a human error predictivity, human errors due to a planning failure is deemed to be very difficult to identify in advance, while human errors during execution are sufficiently predictable by using human error prediction or human reliability analysis methods with adequate resources.     

Effect of grain size and density of spray-pyrolyzed hydroxyapatite particles on the sinterability of hydroxyapatite disk

The effect of grain size and density of hydroxyapatite particles, which were prepared by different spray-pyrolysis temperatures, on the sinterability of hydroxyapatite disk was investigated. Calcium phosphate solution (Ca/P ratio of 1.67 and 0.1 M concentration) was prepared by reacting calcium nitrate tetrahydrate and diammonium hydrogen phosphate solutions, and adding nitric acid. Spray-pyrolysis was carried out at 900 °C, 1200 °C, and 1500 °C at a carrier gas flowing rate of 10 L/min. The particles synthesized at 900 °C were large, hollow spheres with a hole at the outer surface, a broad size distribution, but had small grain sizes. Conversely, the particles synthesized at 1500 °C were small, solid spheres with a narrow size distribution, but had large grain sizes. The particles synthesized at 1200 °C had intermediate properties. A sinterability test conducted at 1100 °C for 1 h demonstrated that small and dense particles with large grain sizes showed a higher relative sintered density compared with large and hollow particles with small grain sizes. The results were explained in terms of the grain size and density of a particle, which were inversely and proportionally affected to sinterability. The practical implication of these results is that highly sinterable hydroxyapatite powders can be synthesized through spray-pyrolysis at a high temperature under a fixed initial concentration of calcium phosphate solution and flow rate of carrier gas.     

Scanning tunneling microscopy and tunneling spectroscopy studies of niobium-containing H6+xP2W18?xNbxO62 (x=0, 1, 2, 3)Wells-Dawson heteropolyacid catalysts to probe their redox property and oxidation catalysis

Niobium-containing H_6+x P₂W_18−x Nb _x O₆₂ (x=0, 1, 2, 3) Wells-Dawson heteropolyacids (HPAs) were investigated by scanning tunneling microscopy (STM) and tunneling spectroscopy (TS) in order to elucidate their redox properties. The HPAs formed two-dimensional well-ordered monolayer arrays on graphite surface and exhibited a distinctive current-voltage behavior called negative differential resistance (NDR) in their tunneling spectra. NDR peak voltage measured on HPA molecule was correlated with reduction potential and absorption edge energy determined by electrochemical method and UV-visible spectroscopy, respectively. NDR peak voltage of H_6+x P₂W_18−x Nb _x O₆₂ Wells-Dawson HPAs appeared at less negative voltage with increasing reduction potential and with decreasing absorption edge energy. Oxidative dehydrogenation of isobutyraldehyde was also carried out as a model reaction to probe oxidation catalysis of the HPAs. The trend of NDR peak voltage of H_6+x P₂W_18−x Nb _x O₆₂ Wells-Dawson HPAs was well consistent with the trend of yield for methacrolein.     

Utilisation possibility of Enterococcus faecalis isolates from neonate's faeces for production of fermented sausages as starter cultures

This study aimed at assessing the utilisation possibility of Enterococcus faecalis as starter cultures for production of fermented sausages. The E. faecalis isolates isolated from faeces samples of 5‐day‐old healthy newborn babies, identified by 16SrDNA sequencing and free from virulence determinants as proven by genomic sequencing, were used for fermented sausages production as starter culture. Six treatments (four inoculated with four different E. faecalis isolates, one with commercial starter culture and one control) were prepared. The inoculation with E. faecalis showed a stronger acidification compared with the control. The treatments with E. faecalis showed significantly higher flavour and acceptability scores in comparison with the control or commercial starter culture. Both of commercial starter culture and E. faecalis were positive with tyramine. Apart from the amine production, the inoculation with E. faecalis generally improved the acidifying activity and flavour of the products, suggesting their application potentials in fermented sausages production as starter cultures.     

Biosynthetic approach for the production of new aminoglycoside derivative

Aminoglycoside antibiotics can be classified into two major groups; streptamine containing and 2-deoxystreptamine containing antibiotics. Here, we report a biosynthetic approach for the fusion of spectinomycin and kanamycin biosynthetic gene clusters to yield the new aminoglycoside derivative, oxykanamycinC, in a non-aminoglycoside producing heterologous host.     

Mechanical and moisture-dependent swelling properties of compressed Japanese cedar

In this research, five groups of compressed wood specimens were investigated, four made from compressed Japanese cedar (Cryptomeria japonica D. Don) with compression ratios (CR) of 33%, 50%, 67% and 70%, and one without compressing for control purpose. The measurements of moisture-dependent swelling of the specimens were carried out in the R, T and L directions, with typical strain values of 10%, 1.5% and 0.1% respectively corresponding to the CR = 67%. Mechanical property tests of the compressed wood were also undertaken. Material properties obtained cover radial and tangential swelling strain rates, shear moduli in LR, LT and RT planes, Young’s moduli in the L, R, T directions and Poisson ratios in all planes. The Young’s moduli along the longitudinal and radial directions have been increased by over 300% in relation to the CR of 70%.