Ultrastrong Medium‐Entropy Single‐Phase Alloys Designed via Severe Lattice Distortion

Severe lattice distortion is a core effect in the design of multiprincipal element alloys with the aim to enhance yield strength, a key indicator in structural engineering. Yet, the yield strength values of medium‐ and high‐entropy alloys investigated so far do not substantially exceed those of conventional alloys owing to the insufficient utilization of lattice distortion. Here it is shown that a simple VCoNi equiatomic medium‐entropy alloy exhibits a near 1 GPa yield strength and good ductility, outperforming conventional solid‐solution alloys. It is demonstrated that a wide fluctuation of the atomic bond distances in such alloys, i.e., severe lattice distortion, improves both yield stress and its sensitivity to grain size. In addition, the dislocation‐mediated plasticity effectively enhances the strength–ductility relationship by generating nanosized dislocation substructures due to massive pinning. The results demonstrate that severe lattice distortion is a key property for identifying extra‐strong materials for structural engineering applications.     

Dry sol-gel polycondensation of hydrosilanes to organosilicas catalyzed by colloidal nickel nanoparticles

The dry sol-gel polycondensation at toluene in ambient air atmosphere of p-X-C6H4SiH3 (X = H, CH3, CH3O, F, Cl) to silica p-X-C6H4SiO15 in high yield, catalyzed by colloidal nickel nanoparticles in-situ generated from nickelocene(II), nickel(II) acetate, and bis(1,5-cyclooctadiene)nickel(0), is described. Similar catalytic activities were observed for the catalysts. Similarly, the dry sol-gel polyco-condensation p-X-C6H4SiH3 (X = CH3, CH3O, F, Cl):C6H4SiH3 (9:1 mole ratio) at toluene in ambient air atmosphere of was performed to yield co-silicas (p-X-C6H4SiO1.5)9(p-X-C6H4SiO1.5)1 in high yield using nickelocene. The co-gels with higher molecular weights and TGA residue yield were obtained when compared to the homogels. The highest yield, molecular weight, polydispersity index, and TGA residue yield were obtained for p-Cl-C6H4SiH3. Some degree of unreacted Si-H bonds still remained in the gel matrix because of steric bulkiness. All the insoluble gels adopt an amorphous structure with a smooth surface. A plausible mechanism for the dry sol-gel reaction was suggested.     

Cloning and functional characterization of the SUR2/SYR2 gene encoding sphinganine hydroxylase in Pichia ciferrii

Saccharomyces cerevisiae sphinganine C4-hydroxylase encoded by the SUR2 gene catalyses the conversion of sphinganine to phytosphingosine. We isolated the SUR2 gene from Pichia ciferrii using nucleotide sequence homology to S. cerevisiae SUR2 to study hydroxylation of sphinganine in the sphingoid base overproducing yeast P. ciferrii. A positive clone was confirmed by nucleotide sequencing. A syringomycin-E resistance phenotype of a S. cerevisiae sur2-null mutant was complemented by expression of the cloned P. ciferrii SUR2 gene. Restoration of phytosphingosine production in the complemented strain was also confirmed, indicating that the cloned gene is a functional homologue of S. cerevisiae SUR2. .     

Study on side collision reconstruction using database based on deformed shape information

A side collision reconstruction algorithm using a database based on the deformed shape information from experiments is suggested. A deformation index related to the deformed shape is developed to set the database for the side collision reconstruction algorithm. Two small-sized model cars are developed to carry out the side collision test. Several side collision tests according to velocities and collision angles are performed for establishing side collision database. A high speed camera with 1000fps is used to capture the motion of the car. Side collision reconstruction algorithm is developed and applied to find the collision conditions before the accident occurred. Several collision cases are tested to validate the database and the algorithm. A database from computer simulation is verified with experiments. According to comparing errors between simulation and experiment, it is satisfied within 6.6%. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Dr. Jeong-Hyun Sohn received his B.S. degree from Pusan National University (1995), M.S. from PNU (1999), and Ph.D. from PNU (2002). He is currently an associate professor in the department of Mechanical Engineering at Pukyong National University in Busan, Korea. He is currently serving as a board member of dynamics and control division, KSME. His major area is vehicle dynamics and flexible multibody dynamics. Dr. Wan-Suk Yoo received his B.S. degree from Seoul National University (1976), M.S. from KAIST (1978) and Ph.D. from University of Iowa(1985). He is professor at Pusan National University, and currently serving as a vice president in KSME. His major area is vehicle dynamics and flexible multibody dynamics.     

Development and comparative study on tire models in the AutoDyn7 program

In this paper, several tire models (Magic formula, Carpet plot, UA tire, DADS tire and STI tire) are implemented and compared. Since the STI (System Technology Inc.) tire model in the AutoDyn7 program is in a good agreement to NADSdyna STI tire model and experiment, it is selected as a reference tire model for the comparison. To compare tire models, input parameters of each tire model are extracted from the STI tire model to preserve the same tire properties. Several simulations are carried out to compare performances of tire models, i. e., bump simulation, lane change simulation, and pulse steering simulation. The performances in vehicle maneuverability are also compared with the four parameter evaluation method.     

The intrinsic thermal decomposition kinetics of SrCO3 by a nonisothermal technique

The kinetics of the decomposition of SrCO₃ in argon to SrO and CO₂ were studied in the temperature range 1000 to 1350 K. The thermal decomposition was followed simultaneously by thermogravimetric analysis (TGA) and differential thermal analysis (DTA) during linear heating. By using a nonisothermal method, the complete rate expression was determined from a relatively small number of experimental runs. Shallow beds of fine synthetic powder as well as thin flakes of pressed powder were employed to obtain the kinetics of decomposition in the absence of heat- and mass-transfer effects. The thermal decomposition started at about 1000 K. The recommended rate expression for the SrCO₃ decomposition is