Structural decomposition of technological domain using patent co-classification and classification hierarchy

Scientometrics - This paper proposes a new method for decomposing a technological domain (TD). Specifically, the method identifies sub-TDs at the different levels of technological hierarchy within...     

Variation in Crystallographic Orientation and Twinning Activation with Size of Individual Grains in Rolled Magnesium Alloy

Metals and Materials International - This study demonstrates that the size of an individual grain in a rolled AZ31 alloy is significantly related to the crystallographic orientation of the grain...     

A study on comparisons of composite and conventional steel bogie frames

In this study, the dynamic characteristics of three different bogie configurations, a conventional Steel bogie (SB), a composite bogie without primary suspension (CB1), and a composite bogie with primary suspensions of conical rubber type (CB2), were compared. The CB1 shows the highest critical speed while the CB2 shows the lowest. The SB configuration showed the highest ride index value while the CB2 showed the lowest. Both of the composite configurations showed better ride comfort index than that of the steel configuration. The trend of the derailment index was opposite to that of the critical speed. In the derailment index measuring test, the CB1 bogie configuration had a 12.3 % higher derailment index than that of the SB. These results show good agreement in overall trends with the simulation results.     

Hypoxia Suppresses Spontaneous Mineralization and Osteogenic Differentiation of Mesenchymal Stem Cells via IGFBP3 Up-Regulation

Hypoxia has diverse stimulatory effects on human adipose-derived stem cells (ASCs). In the present study, we investigated whether hypoxic culture conditions (2% O₂) suppress spontaneous mineralization and osteogenic differentiation of ASCs. We also investigated signaling pathways and molecular mechanisms involved in this process. We found that hypoxia suppressed spontaneous mineralization and osteogenic differentiation of ASCs, and up-regulated mRNA and protein expression of Insulin-like growth factor binding proteins (IGFBPs) in ASCs. Although treatment with recombinant IGFBPs did not affect osteogenic differentiation of ASCs, siRNA-mediated inhibition of IGFBP3 attenuated hypoxia-suppressed osteogenic differentiation of ASCs. In contrast, overexpression of IGFBP3 via lentiviral vectors inhibited ASC osteogenic differentiation. These results indicate that hypoxia suppresses spontaneous mineralization and osteogenic differentiation of ASCs via intracellular IGFBP3 up-regulation. We determined that reactive oxygen species (ROS) generation followed by activation of the MAPK and PI3K/Akt pathways play pivotal roles in IGFBP3 expression under hypoxia. For example, ROS scavengers and inhibitors for MAPK and PI3K/Akt pathways attenuated the hypoxia-induced IGFBP3 expression. Inhibition of Elk1 and NF-κB through siRNA transfection also led to down-regulation of IGFBP3 mRNA expression. We next addressed the proliferative potential of ASCs with overexpressed IGFBP3, but IGFBP3 overexpression reduced the proliferation of ASCs. In addition, hypoxia reduced the osteogenic differentiation of bone marrow-derived clonal mesenchymal stem cells. Collectively, our results indicate that hypoxia suppresses the osteogenic differentiation of mesenchymal stem cells via IGFBP3 up-regulation.     

Effects of amplitude modulation on perception of wind turbine noise

Wind turbine noise is considered to be easily detectable and highly annoying at relatively lower sound levels than other noise sources. Many previous studies attributed this characteristic to amplitude modulation. However, it is unclear whether amplitude modulation is the main cause of these properties of wind turbine noise. Therefore, the aim of the current study is to identify the relationship between amplitude modulation and these two properties of wind turbine noise. For this investigation, two experiments were conducted. In the first experiment, 12 participants determined the detection thresholds of six target sounds in the presence of background noise. In the second experiment, 12 participants matched the loudness of modified sounds without amplitude modulation to that of target sounds with amplitude modulation. The results showed that the detection threshold was lowered as the modulation depth increased; additionally, sounds with amplitude modulation had higher subjective loudness than those without amplitude modulation.     

Capillary action: enrichment of retention and habitation of cells via micro-channeled scaffolds for massive bone defect regeneration

The development of a biomaterial substitute that can promote bone regeneration in massive defects has remained as a significant clinical challenge even using bone marrow cells or growth factors. Without an active, thriving cell population present throughout and stable anchored to the construct, exceptional bone regeneration does not occur. An engineered micro-channel structures scaffold within each trabecular has been designed to overcome some current limitations involving the cultivation and habitation of cells in large, volumetric scaffolds to repair massive skeletal defect. We created a scaffold with a superior fluid retention capacity that also may absorb bone marrow cells and provide growth factor-containing body fluids such as blood clots and/or serum under physiological conditions. The scaffold is composed of 3 basic structures (1) porous trabecular network (300–400 μm) similar to that of human trabecular bones, (2) micro-size channels (25–70 μm) within each trabecular septum which mimic intra-osseous channels such as Haversian canals and Volkmann’s canals with body fluid access, diffusion, nutritional supply and gas exchange, and (3) nano-size pores (100–400 nm) on the surface of each septum that allow immobilized cells to anchor. Combinatorial effects of these internal structures result in a host-adapting construct that enhances cell retention and habitation throughout the 3 cm-height and 4 cm-length bridge-shaped scaffold.     

Interlaminar Fracture Testing Method for CFRP Using Tensile Loading with Acoustic Emission Analysis

A method is described to characterize the uniformity of interlaminar fracture toughness of laminated carbon-fiber-reinforced polymer (CFRP) composites fabricated by the modified vacuum assisted resin transfer molding process. To prepare specimens for Mode I fracture toughness tests, pieces were sectioned from the inlet and vent regions of a CFRP plate ([+30/-30]₆), with a starter crack inserted. The specimens were packed between two rectangular epoxy plates to apply a load using a universal testing machine. Acoustic energy signals were monitored using two sensors attached to the epoxy plates during tensile loading. The difference between the material properties of specimens from the inlet and vent regions of the CFRP plate were statistically compared using one-way analysis of variance (ANOVA); we show that the specimens showed no statistically significant differences in the interlaminar fracture characteristics depending on the part of the mold from which they were taken.