The Effect of Solution Time on the Microstructure of A356.2 Aluminum Alloy Provided by Rheocasting and Squeeze Casting

The evolution of the microstructure of A356.2 alloys prepared by the rheocasting and squeeze casting during solution heat treatment was investigated. In contrast with the conventional solution heat treatment process (3 hours at 540oC), a short time solution treatment process (less than 1 hour at 540oC) is applied in this paper. The results show that the rheocastings require a shorter solution time than the squeeze-castings to obtain spheroidized Si particles. After solution for 10 min, the X-ray diffraction inspection results show that the Mg2Si phase completely is dissolved in both rheocastings and squeeze-castings. However, a small amount of Mg2Si is found at the edge of the Si particle by scanning electron microscope observation. After solution for more than 20 min, the Mg2Si phase is completely dissolved. Fe-rich phases, including AlSiFeMg and AlFeSi, exist throughout the solution process. The developed T6 heat treatment with a short solution time can effectively improve production efficiency and decrease process cost for the rheocasting process. Key words: A356.2 alloy, microstructure, short solution time, rheocasting, squeeze casting

Three-dimensional data-driven magnetostatic field computation using real-world measurement data

Purpose The purpose of this paper is to present the applicability of data-driven solvers to computationally demanding three-dimensional problems and their practical usability when using real-world measurement data. Design/methodology/approach Instead of using a hard-coded phenomenological material model within the solver, the data-driven computing approach reformulates the boundary value problem such that the field solution is directly computed on raw measurement data. The data-driven formulation results in a double minimization problem based on Lagrange multipliers, where the sought solution must conform to Maxwell’s equations while at the same time being as close as possible to the available measurement data. The data-driven solver is applied to a three-dimensional model of a direct current electromagnet. Findings Numerical results for data sets of increasing cardinality verify that the data-driven solver recovers the conventional solution. Additionally, the practical usability of the solver is shown by using real-world measurement data. This work concludes that the data-driven magnetostatic finite element solver is applicable to computationally demanding three-dimensional problems, as well as in cases where a prescribed material model is not available. Originality/value Although the mathematical derivation of the data-driven problem is well presented in the referenced papers, the application to computationally demanding real-world problems, including real measurement data and its rigorous discussion, is missing. The presented work closes this gap and shows the applicability of data-driven solvers to challenging, real-world test cases.

Primary energy saving potential of a solar-driven ejector cooling system: a case study for a Portuguese residential building

The seasonal energy performance of a cooling system based on an innovative variable-geometry ejector (VGE) is numerically investigated by using TRNSYS. The VGE-based system is mainly driven by solar energy, collected through solar thermal collectors, and is coupled to a residential building located in Porto. A biomass boiler is used as back-up heater. The energy performance of the investigated cooling system is compared with that of a conventional solution, based on a commercial air-to-water chiller. Results point out that, almost 75% of the generator heat demand can be supplied by solar collectors and about 90% of the overall energy input of the ejector-based system is satisfied by renewables. Moreover, numerical simulations confirm how the capability to vary the ejector geometry on the basis of current operating conditions allows to strongly improve the ejector seasonal efficiency. A second series of simulations aimed to further enhance the system performance. A master control logic which extends the VGE operation time in correspondence of favourable ambient conditions was introduced, in order to store additional cooling energy in the cold buffer tank. This strategy has proved to be effective, since the energy consumption of the biomass boiler could be reduced up to 35%.

A Four-Channel Gray-Code Addressing TDM Clocked-Analog LDO for Thermo-Optic Tuning in Silicon Photonics

This paper presents a Gray-code addressing time division multiplexing (TDM) clocked-analog low-dropout regulator (CLDO) that shares one controller between four output channels with only one compensation capacitor. We apply the Gray-code addressing strategy to reduce the crosstalk. We also apply the split-output amplifier structure to share the compensation capacitor for further chip area reduction. In addition, we introduce a lightweight local-generated supply to increase the dynamic range. Implemented in 130 nm CMOS process, this design has a total chip area of 0.056 mm2 , which is 67.5% smaller than the conventional solution with four identical LDOs. Post layout simulation results show that the presented four-channel TDM CLDO can simultaneously track four 1 V_pp sinusoidal signals at different frequencies with negligible crosstalk. This TDM CLDO is a promising solution for supplying multiple thermo-optic phase shifters (TOPSs) in silicon photonics

A Four-Channel Gray-Code Addressing TDM Clocked-Analog LDO for Thermo-Optic Tuning in Silicon Photonics

This paper presents a Gray-code addressing time division multiplexing (TDM) clocked-analog low-dropout regulator (CLDO) that shares one controller between four output channels with only one compensation capacitor. We apply the Gray-code addressing strategy to reduce the crosstalk. We also apply the split-output amplifier structure to share the compensation capacitor for further chip area reduction. In addition, we introduce a lightweight local-generated supply to increase the dynamic range. Implemented in 130 nm CMOS process, this design has a total chip area of 0.056 mm2 , which is 67.5% smaller than the conventional solution with four identical LDOs. Post layout simulation results show that the presented four-channel TDM CLDO can simultaneously track four 1 V_pp sinusoidal signals at different frequencies with negligible crosstalk. This TDM CLDO is a promising solution for supplying multiple thermo-optic phase shifters (TOPSs) in silicon photonics

Flexibility from Combined Heat and Power: A Techno-Economic Study for Fully Renewable Åland Islands

As energy systems globally are transitioning into renewable energy, simultaneous targets of high self-sufficiency have led to complex system design proposals. While conventional technology solutions would reduce the complexity in theory, limitations in the potential outcome may exist. To address this dilemma, the work quantified the systemic value provided by a conventional solution; biomass combined heat and power (CHP) production, in terms of economic feasibility, provided flexibility and energy self-sufficiency. The analysis focused on the renewable energy integration of the Åland Islands, where the synergetic island energy system is heavily increasing the wind power capacity. While considering local fuel resource availability, multiple alternative energy system scenarios were constructed. To evaluate the scenarios, the work developed and validated a combined dispatch and investment optimization model. The results showed that the studied conventional approaches limited the achievable self-sufficiency in the power sector (80.6%), however, considerably increasing the value from the present state (18.5%). Second, compared to previous studies, the results indicated a low value from biomass CHP in the wind-based energy system. Instead, the combination of high wind capacity and power-to-heat enabled the best economic feasibility and high self-sufficiency, which could be further improved by lower electricity taxation.

FORMULATION AND EVALUATION OF FLOATING IN SITU GEL OF OMEPRAZOLE MAGNESIUM FOR ORAL DRUG DELIVERY SYSTEM

Objective: Omeprazole magnesium is indicated for the treatment of erosive esophagitis associated with gastroesophageal reflux disease. It is one of the highly prescribed proton pump inhibitor in the management of peptic ulcer diseases. The therapeutic concentration of a drug in blood can be maintained for a prolonged period of time by administering it in the form of in situ floating gel dosage form. Omeprazole magnesium undergoes degradation at a low pH of the esophagus and stomach; it is therefore given as in situ gel, so, there is minimum contact with acidic pH. Methods: Omeprazole magnesium suspension prepared using various polymers and floating agents in varying concentrations. Several evaluation tests including dissolution test to ensure the release of the drug from formulation by in vitro technique, color and homogeneity, in vitro floating duration, in vitro gelling capacity, drug content determination, pH of the formulation, and floating lag time were studied. Results: All formulations demonstrated good Fourier-transform infrared compliance and no interaction between drug, polymer, and other excipients. The study’s findings show that the formulation F6 showed the best results. Conclusion: The developed formulation was a viable alternative conventional solution by virtue of its ability to enhance bioavailability through its longer gastric residence time and ability to sustain drug release as well as the advantage of floating and pH which minimize the degradation of omeprazole magnesium which is easily degraded by acidic environment.

Residue-resolved monitoring of protein hyperpolarization at sub-second time resolution

We propose a method for real-time nuclear magnetic resonance (NMR) spectroscopy of hyperpolarized proteins at residue resolution. The approach is based on dissolution dynamic nuclear polarization (d-DNP), which enables the use of hyperpolarized buffers that selectively boost NMR signals of backbone amides that incur magnetization fast from their surroundings. Capitalizing on the resulting spectral sparseness and simultaneous signal enhancement, we obtained residue-resolved NMR spectra at a sampling rate of 2 Hz. We could thus track the evolution of hyperpolarization at different protein residues simultaneously with time. This was achieved under near-physiological conditions, i.e., in aqueous solution at physiological salt concentration and at 37° C. With this development, two often encountered limitations of conventional solution-state NMR can be addressed: 1) NMR experiments are typically performed under conditions that increase sensitivity but are physiologically not relevant (low pH, low temperature) and; 2) signal accumulation over long periods impedes the determination of fast (on the order of seconds) real-time monitoring. Both limitations are of equal fundamental relevance: interaction studies under non-native conditions are of limited pharmacological relevance, and the key to the function of proteins often resides in their interaction kinetics. The proposed technique possibly opens new routes towards residue and temporally resolved spectroscopy at the atomistic level by overcoming the need for signal averaging in residue-resolved protein biomolecular NMR.

Large-area patterning of full-color quantum dot arrays beyond 1000 pixels per inch by selective electrophoretic deposition

Colloidal quantum dot (QD) emitters show great promise in the development of next-generation displays. Although various solution-processed techniques have been developed for nanomaterials, high-resolution and uniform patterning technology amicable to manufacturing is still missing. Here, we present large-area, high-resolution, full-color QD patterning utilizing a selective electrophoretic deposition (SEPD) technique. This technique utilizes photolithography combined with SEPD to achieve uniform and fast fabrication, low-cost QD patterning in large-area beyond 1,000 pixels-per-inch. The QD patterns only deposited on selective electrodes with precisely controlled thickness in a large range, which could cater for various optoelectronic devices. The adjustable surface morphology, packing density and refractive index of QD films enable higher efficiency compared to conventional solution-processed methods. We further demonstrate the versatility of our approach to integrate various QDs into large-area arrays of full-color emitting pixels and QLEDs with good performance. The results suggest a manufacture-viable technology for commercialization of QD-based displays.