Effect of sand mold models on the simulated mold restraint force and the contraction of the casting during cooling in green sand molds

In this work, the JIS AD12.1 (almost the same as A383.1) aluminum alloy was cast in a green sand mold. The restraint force from the sand mold and the contraction of the casting were measured dynamically from the solidifying temperature to the shake-out temperature using a dedicated device. Then, FEM (Finite Element Method) thermal stress analyses of the experiment were performed. The analyses adopted four types of representative constitutive equations and the mechanical properties of the green sand mold, which were quoted from previous research articles. As verification, this study dynamically compared the simulated restraint force and the contraction of casting with measured results and examined which mechanical properties are important for expressing the restraint force of the sand mold. This verification is the first attempt in the world. As a result, the simulated restraint force was estimated to be over ten times as large as the measured result in each type of equation because the yield stress of the sand mold used in our experiment was lower than those quoted from previous studies. The yield stress measured by a uniaxial compression test was 1/20 of the quoted values. When the measured yield stress was adopted in the simulation, the simulated restraint force and contraction approached the measured results. The yield stress of the sand mold was a dominant factor in the restraint force simulated by the thermal stress analyses. The yield stress of the green sand mold used in the casting process should be measured to predict the residual stress using FEM thermal stress analyses.     

Decay rate and l2 gain analysis for the particle swarm optimization algorithm

The behavior of the particle swarm optimization (PSO) algorithm is analyzed by regarding its dynamics as a system with multiplicative noise and applying control‐theoretic analysis methods. In order to evaluate the convergence and diversity of the PSO algorithm, two new measures related to the decay rate and l² gain of the PSO dynamics are introduced. These measures are characterized by linear matrix inequalities and are therefore efficiently computed by convex optimization tools. Numerical experiments suggest that the measures are effective enough to evaluate the convergence and diversity of the PSO algorithm, which can lead to better understanding of the PSO algorithm from the viewpoints of exploitation and exploration abilities. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

Carbon black texture evolution during catalytic methane decomposition

Catalytic characteristics of carbon black (CB) during methane decomposition have been known to vary according to the amount of produced carbon. Evolution of the surface properties of CB during the reaction was investigated to elucidate the mechanism of the variation in the catalytic activity and evaluate the carbon deposited on CB as a potential carbonaceous product. Kinetic analysis successfully quantified the variation in the catalytic activity by using the relative modification coefficient to consider the degree of carbon deposition. Elemental analysis revealed that the variation in the catalytic characteristics was not influenced by oxygen-containing functional groups except during the initial stage of the reaction. Textural evolution during the reaction was measured by nitrogen adsorption isotherms, and surface microstructural development was observed by transmission electron microscopy. The change in the surface area exposed in the reaction field correlated well with the varying catalytic behavior after the initial deactivation stage. A hypothesis concerning the correlation between the variation in the catalytic activity and the textural properties was proposed. Furthermore, development of a remarkable mesoporous surface structure on CB during the reaction was demonstrated.     

Pendulum testing as a means of assessing the crash performance of longitudinal barrier with minor damage

Longitudinal barriers such as w-beam guardrails are subjected to a series of full-scale crash tests to determine their impact performance before being considered acceptable for use on the nation’s highways. Once longitudinal barriers are installed along a roadway, however, they often sustain minor damage in various ways. Since barriers are exclusively tested in an undamaged condition, there is very little known regarding the crash performance of barriers that have sustained minor damage. Transportation agencies responsible for deploying and maintaining these barrier systems need a better understanding of damaged barrier performance to make timely and cost-effective barrier maintenance decisions under the constraints of limited resources. This study is believed to be the first evaluation of the crash performance of strong post w-beam barrier that has sustained minor damage. A pendulum impact testing methodology was developed for the evaluation of two-post sections of strong post w-beam barrier. Pendulum tests were then conducted on barrier sections with five types of damage: (1) vertical tear, (2) horizontal tear, (3) splice damage, (4) twisted blockout, and (5) missing blockout. Based on these tests, vertical tears were found to be a significant threat to the structural adequacy of the barrier section with a high likelihood for rail rupture. A missing blockout at the splice location was found to result in marginal performance with one test resulting in a large rail tear at the splice. Mid-span horizontal tears and splice damage, with one of eight bolts lacking bearing capacity, were found to have a less significant threat on the structural adequacy of the barrier. Twisted blockout damage was found to have no effect on the structural crash performance of the strong post w-beam barrier.     

Chiral separation with polyurea membrane consisting of L‐lysinyl residue: Proposal of facile method for prediction of permselectivity

Novel chiral polyureas were prepared from L ‐lysine‐4‐nitroanilide and 2,4‐toluene diisocyanate. The polyurea thus prepared gave a durable self‐standing membrane that can be directly converted into molecular recognition membranes by applying an alternative molecular imprinting. The Z‐D ‐glutamic acid (D ‐Glu) molecularly imprinted membrane adsorbed D ‐Glu in preference to L ‐glutamic acid (L ‐Glu) from racemic mixture of Glu and vice versa. Those two types of molecularly imprinted membrane showed optical resolution ability, adopting a concentration gradient as a driving force for membrane transport. A facile method to predict permselectivity of racemic mixture of charged permeant was proposed. From the observed membrane resistance, the permselectivity was predicted. The predicted permselectivity coincided with the observed one. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Survival of a probiotic, Lactobacillus casei strain Shirota, in the gastrointestinal tract: selective isolation from faeces and identification using monoclonal antibodies.

Lactobacillus casei strain Shirota (LCS) is a probiotic bacterium used in the production of fermented milk products and lactic acid bacteria preparations. To investigate the survival of LCS in the gastrointestinal tract, we have developed a selective medium and specific monoclonal antibodies to isolate and identify this strain. Selective LLV agar medium was prepared by modifying LBS medium, a selective medium for lactobacilli, through the replacement of glucose with lactitol as a carbon source and vancomycin as a selective antibiotic. Culture in LLV agar medium followed by ELISA using monoclonal antibodies specific for LCS was able to detect the organism in faeces. Using this method, we studied the faecal recovery of LCS in individuals who drank 125 ml of fermented milk which contained 10(10) live LCS for 3 days. The mean recovery was about 10(7) live bacteria per gram of faeces, indicating that LCS survived transit through the gastrointestinal tract after ingestion of the fermented milk.