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The current physiological in vitro tests of Mg degradation follow the procedure stated according to the ASTM standard. This standard, although useful in predicting the initial degradation behavior of an alloy, has its limitations in interpreting the same for longer periods of immersion in cell culture media. This is an important consequence as the alloy's degradation is time dependent. Even if two different alloys show similar corrosion rates in a short term experiment, their degradation characteristics might differ with increased immersion times. Furthermore, studies concerning Mg corrosion extrapolate the corrosion rate from a single time point measurement to the order of a year (mm/y), which might not be appropriate because of time dependent degradation behavior. In this work, the above issues are addressed and a new methodology of performing long-term immersion tests in determining the degradation rates of Mg alloys was put forth. For this purpose, cast and extruded Mg-2Ag and powder pressed and sintered Mg-0.3Ca alloy systems were chosen. DMEM Glutamax +10% FBS (Fetal Bovine Serum) +1% Penicillin streptomycin was used as cell culture medium. The advantages of such a method in predicting the degradation rates in vivo deduced from in vitro experiments are discussed. [ABSTRACT FROM AUTHOR]

As an alternative to degradable organic coatings the possibility of using layered double hydroxides (LDHs) to generate implant coatings for controlled drug delivery was evaluated in vivo and in vitro. Coatings prepared from LDH suspensions dissolved slowly and appeared compatible with cultured cells. LDH coatings loaded with an antibiotic resulted in antibacterial effects in vitro. The LDH coating prolonged the drug release period and improved the proliferation of adherent cells in comparison to pure drug coatings. However, during incubation in physiological solutions the LDH coatings became brittle and pieces occasionally detached from the surface. For stress protection porous titanium implants were investigated as a substrate for the coatings. The pores prevented premature detachment of the coatings. To evaluate the coated porous implants in vivo a mouse model was established. To monitor bacterial infection of implants noninvasive in vivo imaging was used to monitor luminescently labeled Pseudomonas aeruginosa. In this model porous implants with antibiotic-loaded LDH coatings could antagonize bacterial infections for over 1 week. The findings provide evidence that delayed drug delivery from LDH coatings could be feasible in combination with structured implant surfaces. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 103A: 2141-2149, 2015. [ABSTRACT FROM AUTHOR]

Abstract: The application of titanium (Ti) based biomedical materials which are widely used at present, such as commercially pure titanium (CP-Ti) and Ti–6Al–4V, are limited by the mismatch of Young's modulus between the implant and the bones, the high costs of products, and the difficulty of producing complex shapes of materials by conventional methods. Niobium (Nb) is a non-toxic element with strong β stabilizing effect in Ti alloys, which makes Ti–Nb based alloys attractive for implant application. Metal injection molding (MIM) is a cost-efficient near-net shape process. Thus, it attracts growing interest for the processing of Ti and Ti alloys as biomaterial. In this investigation, metal injection molding was applied to the fabrication of a series of Ti–Nb binary alloys with niobium content ranging from 10wt% to 22wt%, and CP-Ti for comparison. Specimens were characterized by melt extraction, optical microscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). Titanium carbide formation was observed in all the as-sintered Ti–Nb binary alloys but not in the as-sintered CP-Ti. Selected area electron diffraction (SAED) patterns revealed that the carbides are Ti2C. It was found that with increasing niobium content from 0% to 22%, the porosity increased from about 1.6% to 5.8%, and the carbide area fraction increased from 0% to about 1.8% in the as-sintered samples. The effects of niobium content, porosity and titanium carbides on mechanical properties have been discussed. The as-sintered Ti–Nb specimens exhibited an excellent combination of high tensile strength and low Young's modulus, but relatively low ductility. [Copyright &y& Elsevier]

In this paper, a normally-OFF high voltage GaN HFETs based on the Polarization Super Junction (PSJ) concept has been presented. In this new device, threshold voltage (V TH) can be controlled by adjusting the etching depth of the recessed region without modifying on-resistance (R ON) characteristics. The threshold voltage of E-mode device increased to 2 V while the threshold voltage for experimental D-mode structure was about −4 V. The challenge of achieving high breakdown voltage (BV) with minimum on-resistance has been addressed by the lateral scaling of recessed region to achieve an improved figure of merit (FOM). The specific on-resistance of the proposed E-mode PSJ HFET is maintained low while the BV of the device increases from 560 V to 800 V of the D-mode PSJ HFET with the same dimensional parameters. • A normally-OFF high voltage GaN HFETs based on the Polarization Super Junction (PSJ) concept has been presented. • Threshold voltage (VTH) can be controlled by adjusting the etching depth of the recessed region without modifying on-resistance (RON) characteristics. • The BV of the D-mode PSJ HFET device increased from 560V to 800V. • To achieve an improved figure of merit (FOM) by the lateral scaling of recessed region. [ABSTRACT FROM AUTHOR]

One key driver of sustainable goal development is the transition to sustainable electricity resources. The sustainability impact assessment of power production evaluates all potential impacts on society, the environment, and the economy, as well as finds a reasonable solution to shift towards renewable. Given the multitude of quantitative and qualitative methodologies for sustainability analysis, alongside the absence of a unified procedure, selecting an appropriate method poses a significant challenge in conducting this task. Therefore, this paper conducts an extensive review of the methodologies employed for assessing the sustainability of power generation within the future energy mix, as reflected in scientific publications over the past decade (2013–2024). The main objective of this paper is to compare the methodologies and assess their efficiency as suitable tools for analyzing the sustainability of technologies in different geographical regions. The research methodology, following the screening process, selects 102 papers within the study's scope to undergo a critical examination based on sustainability evaluation approaches. It also provides an overview of novel dynamic methods and the application of artificial intelligence in sustainability assessment. The primary findings indicate a deficiency in a standardized approach for sustainability evaluation within electrical technology. In addressing uncertainties in impact assessment due to various parameters, dynamic methods with multiple temporal accuracies are recommended over a static life cycle. The paper includes a case study comparing methods—multi-criteria decision-making, and ranking, scoring—in the Indonesian context. Considering 15 environmental, social, and economic indicators to evaluate the sustainability in Lombok, results indicate that hydropower, gas, and solar technologies exhibit the highest sustainability scores, respectively. [ABSTRACT FROM AUTHOR]

In seal applications a solid elastic body (the seal) ensures the separation of a liquid (e.g., hydraulic oil in one chamber) from a gas (e.g., air in another chamber). In the case of a dynamic seal, the rod is moving and transports a thin liquid film from the liquid chamber into the air chamber. The seal gap consists of a converging gap, a minimum distance between seal and rod and a diverging gap, where transported liquid detaches from the seal. Between the three states of matter (gas, liquid, gas) appear the following contact conditions: liquid‐to‐solid, gas‐to‐liquid, and gas‐to‐solid. A classical fluid‐structure‐interaction is technically possible with limited effort, but is not sufficient to distinguish between the liquid and the gas. A solution can make use of the fact, that the liquid has significant dimensions only in the liquid chamber and is pressurized only there. There is a thin liquid film on the rod in the air chamber, but it has dimensions clearly lower than the air chamber and has the same pressure as the air. Therefore a simulation is possible with the "variable viscosity approach": Liquid and gas are modeled in one single fluid domain. Differences between liquid and gas are included by pressure‐dependent fluid parameters, especially viscosity and density. The resulting violation of the mass balance is very small as the low mass flow through the seal lip is low. The presented approach allows to apply a fluid‐structure simulation with special fluid properties to model a system with three states of matter. Advantages are a less complex model with less complex contact conditions and a reduced simulation time. [ABSTRACT FROM AUTHOR]

To enhance renewable energy (RE) generation and maintain power balance, energy storage systems are of utmost importance. This research introduces a cutting-edge Power-to-Hydrogen (PtH) framework that harnesses hydrogen as a clean and versatile energy storage medium. The primary focus of this study lies in optimizing power flow within a microgrid (μ G) equipped with RE and energy storage systems, considering various factors, such as RE generation, power demand, battery charge cycles, and operational costs. To achieve the optimal balance between power generation and consumption, a sophisticated mathematical solution is devised. This solution governs the charging and discharging patterns for both battery and electrolyzer, ensuring a harmonious power equilibrium. The use of short-term forecasting further refines the optimization process, adapting the parameters based on anticipated RE sources and load requirements. To fine-tune the power management solution for day-to-day operations, an artificial neural fuzzy inference system (ANFIS)-based short-term prediction model is employed. The predictive analysis provides confidence intervals for crucial aspects, including power generation, demand, battery charging cycles, and hydrogen generation. This facilitates precise cost estimation across various hydrogen and heat price ranges. the proposed PtH optimization framework offers an efficient approach to balance power generation and consumption in μ Gs driven by RE sources and energy storage. To validate the proposed approach, numerical simulations are performed based on data from wind and solar farms, load requirements, and cost of energy. The results show that the proposed energy management strategy significantly reduces operational costs and optimizes PtH generation while maintaining power balance within the microgrid (μ G). The predictive approach helps fine-tune the optimization process, improving efficiency and cost-effectiveness. The research convincingly demonstrate the economic advantages of adopting hydrogen as an energy storage medium, paving the way for a cleaner and more sustainable energy future. • Innovative Power-to-Hydrogen (PtH) framework for versatile energy storage. • Analytical solution optimizes microgrid power flow with renewables, ensuring equilibrium. • Short-term forecasting refines parameters, enhances precision, and lowers costs. • Simulations validate reduced operational costs, optimized PtH, and improved microgrid efficiency. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) methods are finding more and more applications in the manufacturing of machine parts. One consequence of this method is that generated surface qualities are typically lower than in other processes. This becomes especially relevant when the surface quality is critical for the mechanical function: This is the case in dynamic sealing technologies, for example, in seals between a moving rod and a hydraulic cylinder. Between the seal lip and the polished rod, a thin lubrication film is established with the goal of minimal leakage. How well this goal is reached depends on the surface quality of the seal. For spare part production of seals, we investigate AM methods, which have a surface defined by layers from fused filament fabrication (FFF). We apply a coupled model for fluid–structure interaction of the elastic seal and the film flow. This model provides information on flow field and pressure distribution. Results change when the 'ideal' seal lip is replaced by the seal lip geometry from FFF. The continuous loss of solid body contact is replaced by a stepwise loss of contact for the FFF surface. [ABSTRACT FROM AUTHOR]

The additive manufacturing (AM) of elastomeric parts based on high-viscosity reinforced rubbers has increasingly become a topic of scientific research in recent years. In addition to the viscosity, which is several decades higher during processing than the viscosities of thermoplastics, the flowability of the compound after the printing process and the necessary chemical crosslinking of the printed component play a decisive role in producing an elastic, high-quality, and geometrically stable part. After the first technological achievements using the so-called additive manufacturing of elastomers (AME) process, the knowledge gained has to be transferred first to concrete industrial parts. Therefore, in this study, the cure kinetics of a conventional rubber compound are tailored to match the specific requirements for scorch safety in the additive manufacturing of an industrial 2-component rod seal based on an acrylonitrile butadiene rubber O-ring in combination with a thermoplastic polyurethane as the base body. Experimental tests on a test rig for rod seals demonstrate the functionality of this additively manufactured 2-component rod seal. [ABSTRACT FROM AUTHOR]

After their assembly, dynamic seals operate in a highly deformed and, therefore, pre‐tensioned configuration. The geometrically enforced elastic pre‐stress is essential for the sealing effect, which minimises the fluid passing through the seal gap. When moving, a thin film of the fluid is transported through the seal gap to the opposite side of the seal. The mechanics of this fluid film can be described, for instance, using the Reynolds equation for thin‐film flow. However, the Reynolds equation is limited to the thin gap and can hardly be applied outside; the "thin gap assumption" is avoided here. Additionally, the geometry penetration of the undeformed seal leads to a system that cannot be meshed at the start of a coupled fluid‐structure simulation. We provide a method for solving this type of system using COMSOL Multiphysics. In the first step, solid body contact builds up the elastic pretension. In the following step, the solid body contact is incrementally replaced by fluid pressure induced by an increasing rod movement. The developed model is capable of describing the full loss of solid body contact. It can be applied to simulate local fluid backflow in the vicinity of the seal gap. [ABSTRACT FROM AUTHOR]

Sintering behavior, microstructure and mechanical properties of a Ti–16Nb alloy processed by metal injection molding (MIM) technology using elemental powders were investigated in this work by optical microscopy, X-ray diffraction (XRD), dilatometer, scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). It was found that from 700 °C to 1500 °C the homogenization and densification process of MIM Ti–16Nb alloy consisted of three steps, i.e., Ti-diffusion-controlled step, Ti–Nb-diffusion step and matrix-diffusion step. Titanium carbide formation was observed in the samples sintered at 1300 °C and 1500 °C, but not in the ones sintered at 900 °C and 1100 °C. The MIM Ti–16Nb specimens sintered at 1500 °C exhibited a good combination of high tensile strength and low Young’s modulus. However, the titanium carbide particles led to poor ductility. [ABSTRACT FROM AUTHOR]

• Reactive power control of micro-grids during asymmetrical voltage sags to comply with modern grid code requirements. • Sharing requested reactive power among the grid connected sources in the secondary layer. • Restoring the PCC voltage by independently controlling each phase of the grid connected sources in the primary layer. • Implementing a nonlinear robust fractional-order sliding mode controller in the primary control layer. • Keeping the power quality indexes such as total harmonic distortion (THD) and voltage imbalance factor in acceptable range during LVRT conditions. Application of micro-grids (MGs) as a solution for future energy systems are significantly increasing in recent years. On the other hand, more stringent requirements are added to grid codes (GCs) of low-voltage distribution networks. Accordingly, this paper proposes a low-voltage ride-through (LVRT) control scheme for four-wire multi-source MGs. The novel strategy is composed of two layers for controlling each phase of the grid-connected sources independently. The primary layer contains a reverse-droop function for each phase and fractional-order sliding-mode-control (FOSMC). The secondary layer determines the total requested reactive power for each phase during symmetrical and asymmetrical voltage drops. Then, the mentioned power is shared among the phases of each inverter based on the reactive power-sharing strategy and GC requirements. Based on the proposed grid-following controller, the voltage of faulty phases is compensated by reactive power injection. In addition, power quality indexes are kept in acceptable ranges during abnormalities, and the FOSMC performs better than the conventional methods. The effectiveness of the proposed scheme is verified through offline simulations in MATLAB/Simulink as well as validation by real-time results. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Ongoing research has proven that Mg alloys can be introduced into the metal injection moulding process for the production of small parts in high quantities and of complex shape for medical as well as lightweight applications. Previously, development studies have been conducted using Mg and Mg-Ca alloys intended for medical application. However, progress towards the implementation of a process for technical and lightweight applications alloys with higher strength is needed. Therefore, in this study processing of conventional AZ81 alloy by MIM was successfully developed. Using this alloy, a yield strength of approximately 120 MPa and an ultimate tensile strength of approximately 255 MPa with elongation at fracture of approximately 7% was achieved. T4 heat treatment at 420 °C for 10 h does not reveal a positive influence on the mechanical properties this could be caused by an observed grain growth effect. This is in contrast to conventional material for example as cast, where T4 heat treatment is known to improve the mechanical properties especially elongation at fracture. [ABSTRACT FROM AUTHOR]