Prediction model for surface temperature of roller and densification of iron powder during hot roll pressing

The hot roll pressing of iron powder with several rotating speeds was carried out on a pilot-plant scale. From these experiments, it was confirmed that the surface temperature of roller was increased with increasing its rotating speed. It was also known that the heat transfer coefficient between the iron powder and the roller surface is closely related with the rotating speed of roller. These results were quantitatively described by using a mathematical model which was derived based on the steady-state heat transfer during hot roll pressing. In addition, the densification behavior of iron powder during the hot roll pressing was simulated by a finite element model based on the arbitrary Lagrangian and Eulerian (ALE) method and a yield criterion for metal powder. From these models, the maximum critical rotating speed of roller during the hot roll pressing, in which the roller could hold out against the thermal fracture, could be determined.     

Quantitative models on corrosion fatigue crack growth rates in metals: Part II. application of fatigue crack growth rate modeling for nickel-based superalloys at elevated temperatures

Approaches to predict da/dN-àK for environmental situations; including empirical interpolative equations, linear superposition of mechanical fatigue and time-based environmental cracking, and mechanism-based models; are presented. For several material-environment systems, these models were incorporated in fracture mechanics life prediction methods, and successes have been reported in evaluating the corrosion fatigue contribution. Considerable uncertainties are, however, associated with these models. The linear superposition analysis is emphasized; material-environment systems that are severely environment-sensitive should be adequately described by this method. Direct and indirect methods exist to define time-based crack growth rates for use in linear superposition predictions of da/dN. The linear superposition approach is effective, but only for those cases where K_ISCC is high relative to typical flawed component stress intensity levels. Empirical curve-fit models require an extensive environmental crack growth rate data base, which are costly to develop, and are effective for interpolations but not predictions of fatigue crack growth data. Mechanism-based models for broad predictions of cycle-time dependent da/dN versus àK, and other variables such as frequency or hold time, are in an infant state.     

Sensitivities of input parameters for predicting stability of soil slope

Bulletin of Engineering Geology and the Environment - The infinite slope stability model is the basis for predicting the slope stability; however, the fundamental theory requires various input...     

Fracture toughness of CFRP laminated plates according to resin content

CFRP(carbon fiber reinforced plastic) has recently found wide use in different industries. The material, however, is very prone to damage from collision with foreign objects. This study aims at finding Ĵ-integral in mode II for CFRP laminated plates based on classical bar theory for dynamic conditions in consideration of inertia forces and eventually to finding dynamic inter-layer fracture toughness. Dynamic inter-layer fracture toughness was observed using an in-house ENF (End Notched Flexure) experimental facility using Split Hopkinson’s Bar (SHPB). Also the variation of the fracture toughness depending on different resin contents and fiber arrangement in the CFRP specimen ([0°3/90°3/0°6/90°3/0°3], [0°20], [0°5/90°10/0°5]) was observed. It was established that under both quasi-static and dynamic load conditions, the critical load and the inter-layer fracture toughness increased sharply following the extension of the resin content. Thus, it may be concluded that the resin content is the major factor determining the inter-layer fracture toughness in the CFRP laminated plate.     

Different types of multiple‐synapse boutons in the cerebellar cortex between physically enriched and ataxic mutant mice

Experience‐dependent synapse remodeling is associated with information storage in the nervous system. Neuronal synapses show alteration in various neurological and cognitive disorders in their structure and function. At the ultrastructural level, parallel fiber boutons contacting multiple spines of Purkinje cells in the cerebellar cortex are commonly observed in physiologically enriched animals as well as pathological ataxic mutants. However, the dendritic origin of those spines on parallel fiber multiple‐synapse boutons (MSBs) has been poorly understood. Here, we investigated this issue by 3‐dimensional ultrastructural analysis to determine synaptic connectivity of MSBs in both mice housed in physically enriched environment and cerebellar ataxic mutants. Our results demonstrated that environmental enrichment selectively induced MSBs to contact spines from the same parent dendrite, indicating focal strengthening of synapse through the simultaneous activation of two adjacent spines. In contrast, ataxic mutants displaying impaired motor coordination had significantly more MSBs involving spines originating from different neighboring dendrites compared to both wild‐type and environmentally enriched animals, suggesting that compromising multiple synapse formation may lead to abnormal motor behavior in the mutant mice. These findings propose that environmental stimulation in normal animals mainly involves the refinement of preexisting synaptic networks, whereas pathological ataxic conditions may results from less‐selective but compromising multiple synaptic formation. This study underscores that different types of multiple synapse boutons may have disparate effects on cerebellar synaptic transmission.     

FMEA for the reliability of hydroformed flanged part for automotive application

Tube hydroforming technology is widely used in the automotive industries due to its advantages such as weight reduction, increased strength, improved quality, and reduced tooling cost compared to conventional manufacturing technology. The hydroformed parts often have to be structurally joined at some point. Therefore, the hydroformed automotive parts which have a localized attachment flange are useful. In many cases, the parts formed by hydroforming process are directly related with structural safety, reliability of hydroformed parts must be considered. In this study, hydroforming process of flanged rectangular parts was designed and process reliability was investigated. Finite element analysis was performed to optimize tool geometry considering process parameters such as die aspect ratio and pressure conditions with Dynaform 5.5. Hydroforming experiments to fabricate a flanged rectangular part were performed with optimized tool geometry. The relationship between process parameters and defect was analyzed by FMEA (failure modes and effects analysis). The result shows that process condition was optimized and reliability of rectangular part was increased.     

Selective catalytic NOx reduction on Antimony promoted V2O5-Sb/TiO2 catalyst

Quantum chemical calculation was carried out to choose a promoter which can reduce the poisoning of V2O5/TiO2 catalysts by SO2.Several atoms were chosen as candidates and new catalysts were synthesized by impregnation method.The NOx conversion rate was measured at temperatures between 100 and 400 ℃ and poisoning effect was investigated.The most promising candidate promoter, Se, was excluded because of its high vapor pressure.On the other hand, Sb shows best promoting properties.Sb promoted catalyst reaches the maximum NOx conversion rate at 250 ℃.It also shows considerably enhanced resistance to poisoning of V2O5/TiO2 catalysts by SO2.     

A two-photon fluorescent probe for lipid raft imaging: C-laurdan

The lipid-rafts hypothesis proposes that naturally occurring lipid aggregates exist in the plane of membrane that are involved in signal transduction, protein sorting, and membrane transport. To understand their roles in cell biology, a direct visualization of such domains in living cells is essential. For this purpose, 6-dodecanoyl-2-(dimethylamino)naphthalene (laurdan), a membrane probe that is sensitive to the polarity of the membrane, has often been used. We have synthesized and characterized 6-dodecanoyl-2-[N-methyl-N-(carboxymethyl)amino]naphthalene (C-laurdan), which has the advantages of greater sensitivity to the membrane polarity, a brighter two-photon fluorescence image, and reflecting the cell environment more accurately than laurdan. Lipid rafts can be visualized by two-photon microscopy by using C-laurdan as a probe. Our results show that the lipid rafts cover 38 % of the cell surface.     

Effects of walking speed and age on the directional stride regularity and gait variability in treadmill walking

Journal of Mechanical Science and Technology - In Inertial measurement unit (IMU) based gait analysis systems, the shoe-type sensor is not commonly used, unlike trunk attached sensors. The purpose...