Performance Comparison of Zn-Based and Al–Si Based Coating on Boron Steel in Hot Stamping

The coatings of boron steels play an important role in affecting the quality of hot stamping parts, so it is important to evaluate the hot stamping performance of coatings before designing processes. Taking the U-type hot stamping part of boron steel as research objects, the surface quality, microstructure and temperature variation of samples with GA (galvannealed), GI (galvanized) and Al–Si coatings were observed and analyzed to evaluate the anti-oxidation, forming and quenching performances of different coatings. The results show that all the GA, GI and Al–Si coatings could provide good oxidation protection and also act as the lubricants for avoiding the friction damage of sample substrates and die-surface. But the different compositions of GA, GI and Al–Si coatings will contribute the different colors. Under the same deformation degree, the Al–Si coating can provide the best substrate protection and the GI coating will induce cracks in the substrate because of the liquid metal-induced embrittlement phenomenon. There is no significant difference between the quenching performances of GA, GI and Al–Si coatings, and the thermal conductivity of the GI coating is slightly better than Al–Si and GA coatings.

Bi2S3 and MoS2 Soft Coatings: A Comparative Study of Their Frictional Behavior Under Different Humidity Levels, Contact Stresses, and Sliding Speeds

Bi2S3 is a promising solid lubricant for demanding applications, such as oil extraction, heavy mining, and aerospace components. However, so far its tribological behavior has not been studied in depth. Bi2S3 soft coatings were evaluated utilizing reciprocating sliding tests under different levels of relative humidity level, contact stress, and sliding speed and the results were benchmarked against MoS2 coatings. In addition, ab initio calculations using density functional theory modeling were employed for studying the interaction between the sulfides and the steel substrates and the effect of water intercalation at an atomic level. It was found that Bi2S3 presents excellent environmental adaptability and substrate protection over a wide range of testing conditions, thanks to its characteristic crystal structure.

Effect of Copper on the Mitochondrial Carnitine/Acylcarnitine Carrier Via Interaction with Cys136 and Cys155. Possible Implications in Pathophysiology

The effect of copper on the mitochondrial carnitine/acylcarnitine carrier (CAC) was studied. Transport function was assayed as [3H]carnitine/carnitine antiport in proteoliposomes reconstituted with the native protein extracted from rat liver mitochondria or with the recombinant CAC over-expressed in E. coli. Cu2+ (as well as Cu+) strongly inhibited the native transporter. The inhibition was reversed by GSH (reduced glutathione) or by DTE (dithioerythritol). Dose-response analysis of the inhibition of the native protein was performed from which an IC50 of 1.6 µM for Cu2+ was derived. The mechanism of inhibition was studied by using the recombinant WT or Cys site-directed mutants of CAC. From the dose-response curve of the effect of Cu2+ on the recombinant protein, an IC50 of 0.28 µM was derived. Inhibition kinetics revealed a non-competitive type of inhibition by Cu2+. However, a substrate protection experiment indicated that the interaction of Cu2+ with the protein occurred in the vicinity of the substrate-binding site. Dose-response analysis on Cys mutants led to much higher IC50 values for the mutants C136S or C155S. The highest value was obtained for the C136/155S double mutant, indicating the involvement of both Cys residues in the interaction with Cu2+. Computational analysis performed on the WT CAC and on Cys mutants showed a pattern of the binding energy mostly overlapping the binding affinity derived from the dose-response analysis. All the data concur with bridging of Cu2+ with the two Cys residues, which blocks the conformational changes required for transport cycle.

SITE SUITABILITY ANALYSIS FOR COMMUNITY-BASED TROPICAL SEA CUCUMBER HOLOTHURIA SCABRA GROW-OUT IN NORTH SULAWESI WATERS

North Sulawesi, a region that has experienced a decreasing population of commercial sea cucumbers in Indonesia, has recently been designated an aquaculture development area. Recent developments of sea cucumber Holothuria scabra hatchery technology have successfully enabled the small-scale enterprise to produce hatcheryreared sandfish for restocking purposes. However, the grow-out phase requires considerable resources including ex-situ grow-out sites, labor, and distribution. This study aims to investigate the suitability of some potential grow-out sites for juvenile H. scabra in North Sulawesi waters. Three traditional sea cucumber fishing grounds in coastal areas of North Minahasa regency in North Sulawesi, i.e., Tanjung Merah, Tasikoki and Makalisung, were examined to determine their suitability as a grow-out site. Several criteria encompassing bioecological (native sea cucumber population, seagrass bed population, competitor/predator), environmental (substrate, protection to weather, water quality, tidal cycle), and technical/support (access, safety, labor) were assessed in each site. Site suitability analysis using a multi-criteria decision-making tool, Analytical Hierarchy Process (AHP), shows that Tasikoki has the highest suitability score (48.94%) followed by Tanjung Merah (27.18%) and Makalisung (23.88%). Tasikoki scores higher than the two other sites in 7 out of 11 sub-criteria, including native sandfish population, seagrass species, substrate, weather protection, safety, and community support. Our finding suggests that Tasikoki is bioecologically, environmentally, and technically the best potential site to be developed for H. scabra juvenile grow-out.

Numerical Analysis of Elastic Contact between Coated Bodies

Substrate protection by means of a hard coating is an efficient way of extending the service life of various mechanical, electrical, or biomedical elements. The assessment of stresses induced in a layered body under contact load may advance the understanding of the mechanisms underlying coating performance and improve the design of coated systems. The iterative derivation of contact area and contact tractions requires repeated displacement evaluation; therefore the robustness of a contact solver relies on the efficiency of the algorithm for displacement calculation. The fast Fourier transform coupled with the discrete convolution theorem has been widely used in the contact modelling of homogenous bodies, as an efficient computational tool for the rapid evaluation of convolution products that appear in displacements and stresses calculation. The extension of this technique to layered solids is tantalizing given that the closed-form analytical functions describing the response of layered solids to load are only available in the frequency domain. Whereas the false problem periodization can be treated as in the case of homogenous solids, the aliasing phenomenon and the handling of the frequency response function in origin require adapted techniques. The proposed algorithm for displacement calculation is coupled with a state-of-the-art contact solver based on the conjugate gradient method. The predictions of the newly advanced computer program are validated against existing results derived by a different method. Multiple contact cases are simulated aiming to assess the influence of coating thickness and of its elastic properties on the contact parameters and the strass state. The performed simulations prove that the advanced algorithm is an efficient tool for the contact analysis of coated bodies, which can be used to further understand the mechanical behavior of the coated system and to optimize its design.