Determination of Optimal Line-Heating Conditions for Flatness Control of Wind Tower Blocks Using Strain as Direct Boundary Method.

The wind tower block is welded with the flange to assemble the wind tower. The inherent strain due to local heating and cooling of the weld affects the flatness of the flange. Therefore, line heating is performed to satisfy the design criteria of the flange flatness, but the work variables depend on the operator's empirical judgment. This study proposed a method to determine the optimum linear heating conditions to control the welded flatness of wind tower blocks and flanges. A proposed method uses the inherent strain method, a simple analysis method, and the optimization is performed based on the deformation superposition method. The changes in flange flatness due to welding and single-point heating were calculated. Then, the flatness change due to single-point heating is superimposed with a scale factor, which represents the magnitude of line heating, and is added to the flatness change due to welding. Using the optimization procedure, the line heating conditions used to derive the flatness that satisfies the design criteria were derived and applied to the analytical model for verification.

Stiffener Design to Maintain Line Heating Efficiency during the Lifting Process Considering Phase Transformation.

In the shipbuilding industry, welding is the main technique used to join steel structures. There is a lifting process, post-welding, that can eliminate the correction effect of line heating. Line heating is reperformed after the lifting process. This can significantly delay the ship assembly process. Herein, we present a design method for installing a permanent stiffener to avoid the disappearance of the line heating effect during the lifting process. The change in physical properties due to heating and cooling of the line heating is calculated. The limiting stress, at which the effect of the line heating completely disappears, based on the inherent strain theory, is obtained. The phase fraction by the cooling rate is calculated using the continuous cooling transformation diagram and the Kiustinen-Marburgerm equation. Physical properties affected by the phase transformation are calculated, considering the physical properties and fraction of each phase. The square plate theory and superposition principle are used to construct a local model, with a stiffener, of the ship block. The stress caused by the shape of the stiffener and the distance between the stiffeners were calculated for the local model. The calculated stress and the limiting stress were compared to determine, for the expected line heating efficiency, the most acceptable stiffener design. Finally, to confirm the elimination of the problem, the designed stiffener is analyzed using the finite element method.

Ecotoxicity evaluation of Cu- and Fe-CNT complexes based on the activity of bacterial bioluminescence and seed germination.

The toxic effects of the composites of Fe0 and Cu0 with different percentages of CNTs were examined based on the activity of bacterial bioluminescence and seed germination. In terms of the EC50 values, the toxic effects of Cu0 on bacterial bioluminescence and seed germination were approximately 2 and 180 times greater than that of Fe0, respectively. The toxicity increased with increasing CNT content in the Cu-CNT mixtures for both organisms, whereas opposite results were observed with Fe-CNT mixtures. The mean toxic effects of Cu-CNT (6%) were approximately 1.3-1.4 times greater than that of Cu-CNT (0%), whereas the toxic effects of Fe-CNT (6%) were approximately 2.1-2.5 times lower than that of Fe-CNT (0%) for both the bioluminescence activity and seed germination. The causes of this phenomenon are unclear at this point. More research will be needed to elucidate the mechanism of the toxicity of nano-mixture materials and the causes of the different patterns of toxicity with Cu- and Fe-CNT mixtures.

Electrochemical and in vitro neuronal recording characteristics of multi-electrode arrays surface-modified with electro-co-deposited gold-platinum nanoparticles.

In order to complement the high impedance electrical property of gold nanoparticles (Au NPs) we have performed electro-co-deposition of gold-platinum nanoparticles (Au-Pt NPs) onto the Au multi-electrode array (MEA) and modified the Au-Pt NPs surface with cell adhesive poly-D-lysine via thiol chemistry based covalent binding. The Au-Pt NPs were analyzed to have bimetallic nature not the mixture of Au NPs and Pt NPs by X-ray diffraction analysis and to have impedance value (4.0 × 10(4) Ω (at 1 kHz)) comparable to that of Pt NPs. The performance of Au-Pt NP-modified MEAs was also checked in relation to neuronal signal recording. The noise level in Au-Pt NP-modified MEAs was lower than in that of Au NP-modified MEA.

Microscale tribological behavior and in vitro biocompatibility of graphene nanoplatelet reinforced alumina.

Graphene nanoplatelets were added as reinforcement to alumina ceramics in order to enhance microscale tribological behavior, which would be beneficial for ceramic-on-ceramic hip implant applications. The reduction in microscale wear is critical to hip implant applications where small amounts of wear debris can be detrimental to patients and to implant performance. The addition of the GNPs lead to improvements in fracture toughness and wear (scratch) resistance of 21% and 39%, respectively. The improved wear resistance was attributed to GNP-induced toughening, which generates fine (~100nm) microcracks on the scratch surface. In addition, active participation of GNPs was observed in the scratch subsurface of GNP-reinforced samples through focused ion beam sectioning. Friction coefficients are not significantly influenced by the addition of GNPs, and hence GNPs do not act as solid state lubricants. In vitro biocompatibility with human osteoblasts was assessed to evaluate any possible cytotoxic effects induced by GNPs. Osteoblast cells were observed to survive and proliferate robustly in the GNP-reinforced samples, particularly those with high (10-15vol%) GNP content.

In vitro extracellular recording and stimulation performance of nanoporous gold-modified multi-electrode arrays.

OBJECTIVE: Nanoporous gold (Au) structures can reduce the impedance and enhance the charge injection capability of multi-electrode arrays (MEAs) used for interfacing neuronal networks. Even though there are various nanoporous Au preparation techniques, fabrication of MEA based on low-cost electro-codeposition of Ag:Au has not been performed. In this work, we have modified a Au MEA via the electro-codeposition of Ag:Au alloy, followed by the chemical etching of Ag, and report on the in vitro extracellular recording and stimulation performance of the nanoporous Au-modified MEA. APPROACH: Ag:Au alloy was electro-codeposited on a bilayer lift-off resist sputter-deposition passivated Au MEA followed by chemical etching of Ag to form a porous Au structure. MAIN RESULTS: The porous Au structure was analyzed by scanning electron microscopy and tunneling electron microscopy and found to have an interconnected nanoporous Au structure. The impedance value of the nanoporous Au-modified MEA is 15.4 ± 0.55 kΩ at 1 kHz, accompanied by the base noise V rms of 2.4 ± 0.3 µV. The charge injection limit of the nanoporous Au-modified electrode estimated from voltage transient measurement is approximately 1 mC cm(-2), which is comparable to roughened platinum and carbon nanotube electrodes. The charge injection capability of the nanoporous Au-modified MEA was confirmed by observing stimulus-induced spikes at above 0.2 V. The nanoporous Au-modified MEA showed mechanical durability upon ultrasonic treatment for up to an hour. SIGNIFICANCE: Electro-codeposition of Ag:Au alloy combined with chemical etching Ag is a low-cost process for fabricating nanoporous Au-modified MEA suitable for establishing the stimulus-response relationship of cultured neuronal networks.

Characterization of multiwalled carbon nanotube-reinforced hydroxyapatite composites consolidated by spark plasma sintering.

Pure HA and 1, 3, 5, and 10 vol% multiwalled carbon nanotube- (MWNT-) reinforced hydroxyapatite (HA) were consolidated using a spark plasma sintering (SPS) technique. The relative density of pure HA increased with increasing sintering temperature, but that of the MWNT/HA composite reached almost full density at 900°C, and then decreased with further increases in sintering temperature. The relative density of the MWNT/HA composites increased with increasing MWNT content due to the excellent thermal conductivity of MWNTs. The grain size of MWNT/HA composites decreased with increasing MWNT content and increased with increasing sintering temperature. Pull-out toughening of the MWNTs of the MWNT/HA composites was observed in the fractured surface, which can be used to predict the improvement of the mechanical properties. On the other hand, the existence of undispersed or agglomerate MWNTs in the MWNT/HA composites accompanied large pores. The formation of large pores increased with increasing sintering temperature and MWNT content. The addition of MWNT in HA increased the hardness and fracture toughness by approximately 3~4 times, despite the presence of large pores produced by un-dispersed MWNTs. This provides strong evidence as to why the MWNTs are good candidates as reinforcements for strengthening the ceramic matrix. The MWNT/HA composites did not decompose during SPS sintering. The MWNT-reinforced HA composites were non-toxic and showed a good cell affinity and morphology in vitro for 1 day.

Variation of nephrotoxicity biomarkers by urinary storage condition in rats.

Recently, there has been an increase in the use of several nephrotoxicity biomarkers in preclinical experiments. In addition, it has been indicated that the result may have been influenced by secondary factors, such as sample storage condition or storage period. In this study, we have assessed the variation in urinary nephrotoxicity biomarkers as a result of urine storage conditions and storage period of the urine. Urine was sampled from specific pathogen-free Sprague-Dawley rats (19 weeks old), which were housed individually in hanged stainless steel wire mesh cages. Urine was stored at 20℃, at 4℃, or at -70℃ after sampling. The levels of the biomarkers such as beta-2 microglobulin (B2M), cystatin-C (Cys-C), N-acetyl-ß- D-glucosaminidase (NAG), micro albumin (MA), micro protein (MP) were measured at 6, 24, 48 and 144 hr after sampling. The B2M level was significantly decreased at 6, 24, 48, and 144 hr compared to 0 hr at -70℃ (p < 0.05, p < 0.01, p < 0.05, and p < 0.05, respectively) and 24 and 144 hr at 20℃ (p < 0.01, p < 0.01, respectively). The Cys-C level was significantly decreased at 144 hr compared to 0 hr at 4℃ (p < 0.01), at 20℃ (p < 0.05) and at 70℃ (p < 0.01). MP and MA levels were not different for 144 hr in all storage conditions. Taken together, B2M and Cys-C levels were modulated by storage temperature and period. For the enhancement of test accuracy, it is suggested that strict protocols be established for samples to minimize the effects of the storage conditions on the detected levels of biomarkers.

Fine neurite patterns from photocrosslinking of cell-repellent benzophenone copolymer.

We have synthesized photocrosslinkable benzophenone copolymer, Poly(St-co-MBz), and fabricated cell-repellent patterns of Poly(St-co-MBz) on covalently bound poly-D-lysine (PDL) layer via the photocrosslinking. We have successfully obtained fine grid line pattern with line width of 3 µm and fine neurite, presumably axon, patterns with excellent pattern fidelity. We found that benzophenone unit can be crosslinked under the exposure of UV (with the intensity of ∼77 mW/cm² at 280 nm and ∼60 mW/cm² at 365 nm) without photo-oxidative damage to PDL, poly-L-lysine, and polyethyleneimine.

Enhancement of neuronal cell adhesion by covalent binding of poly-D-lysine.

We have prepared the poly-d-lysine (PDL) bound surfaces for neuron cell culture by covalent binding between the poly-d-Lysine and substrates and investigated neuronal cell adhesion properties and cell growth morphology. The number of neuronal cell and the number of neurite per neuronal cell on PDL bound surfaces was much more than those on PDL coated surfaces and also the neuronal cells on PDL bounded surfaces survived a longer time. On the pattern of covalently bound PDL, neuronal cells and their neurites are confined within the grid line leading to patterned neuronal networks with the long-term survival.

One-pot fabrication of various silver nanostructures on substrates using electron beam irradiation.

The one-pot fabrication of various silver nanostructures on substrates is achieved through electron beam irradiation of the surface of silver dodecanethiolate (Ag(I)- SC(12)). The Ag(I)-SC(12) films are simply prepared by spin-coating silver salt and dodecanethiol solution. Various silver nanostructures such as particles, rods, cubes, and networks are prepared from the Ag(I)- SC(12) film with an electron beam voltage from 0.3 to 2 MV, current from 0.06 to 0.24 mA, and/or irradiation time from 30 to 80 s. The morphology and chemical composition of the irradiated samples are characterized by scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), and x-ray diffraction (XRD).

Improved enzymatic hydrolysis yield of rice straw using electron beam irradiation pretreatment.

Rice straw was irradiated using an electron beam at currents and then hydrolyzed with cellulase and beta-glucosidase to produce glucose. The pretreatment by electron beam irradiation (EBI) was found to significantly increase the enzyme digestibility of rice straw. Specifically, when rice straw that was pretreated by EBI at 80 kGy at 0.12 mA and 1 MeV was hydrolyzed with 60 FPU of cellulase and 30 CBU of beta-glucosidase, the glucose yield after 132 h of hydrolysis was 52.1% of theoretical maximum. This value was significantly higher than the 22.6% that was obtained when untreated rice straw was used. In addition, SEM analysis of pretreated rice straw revealed that EBI caused apparent damage to the surface of the rice straw. Furthermore, EBI pretreatment was found to increase the crystalline portion of the rice straw. Finally, the crystallinity and enzyme digestibility were found to be strongly correlated between rice straw samples that were pretreated by EBI under different conditions.

Size controlled miniscale synthesis of silver nanoparticles using TEM electron beam.

A method for one-pot size-controlled synthesis of silver nanoparticles is proposed and described. The synthesis is based on the reduction of silver-alkanethiolates complexes having highly ordered supramolecular structures through electron beam irradiation in transmission electron microscope (TEM). The method allows synthesis of silver nanoparticles of diameters between 1.9 nm and 5.9 nm. Different diameters within this range can be selected for by varying the acceleration voltage in TEM, alkyl chain length, and structure of the silver-alkanethiolates complexes.