Large‐area spatial atomic layer deposition of amorphous oxide semiconductors at atmospheric pressure

Indium gallium zinc oxide (IGZO) is deposited using plasma‐enhanced spatial atomic layer deposition (sALD) on substrates as large as 32 × 35 cm². Excellent uniformity and thickness control leads to high‐performing and stable coplanar top‐gate self‐aligned (SA) thin‐film transistors (TFTs). The integration of a sALD‐deposited aluminum oxide buffer layer into the TFT stack further improves uniformity and stability. The results demonstrate the viability of atmospheric sALD as a novel deposition technique for the flat‐panel display industry.     

An automatic optimization method for minimizing supporting structures in additive manufacturing

The amount of supporting structure usage has been a major research topic in layer-based additive manufacturing (AM) over the past years as it leads to increased fabrication time and decreased surface quality. Previous studies focused on deformation and topology optimization to eliminate the number of support structures. However, during the actual fabrication process, the properties of shape and topology are essential. Therefore, they should not be modified casually. In this study, we present an optimizer that reduces the number of supporting structures by identifying the prime printing direction. Without rotation, models are projected in each direction in space, and the basis units involved in the generation of support structures are separated. Furthermore, the area of the supporting structures is calculated. Eventually, the prime printing direction with minimal supporting area is obtained through pattern-searching method. The results of the experiment demonstrated that the printing area was reduced by up to 60% for some cases, and the surface quality was also improved correspondingly. Furthermore, both the material consumption and fabrication time were decreased in most cases. In future work, additional factors will be considered, such as the height of the supporting structures and the adhesion locations to improve the efficiency of this optimizer.The full text can be downloaded at https://link.springer.com/content/pdf/10.1007%2Fs40436-019-00277-y.pdf     

Design of experiments (DoE) in pharmaceutical development

At the beginning of the twentieth century, Sir Ronald Fisher introduced the concept of applying statistical analysis during the planning stages of research rather than at the end of experimentation. When statistical thinking is applied from the design phase, it enables to build quality into the product, by adopting Deming’s profound knowledge approach, comprising system thinking, variation understanding, theory of knowledge, and psychology.

The pharmaceutical industry was late in adopting these paradigms, compared to other sectors. It heavily focused on blockbuster drugs, while formulation development was mainly performed by One Factor At a Time (OFAT) studies, rather than implementing Quality by Design (QbD) and modern engineering-based manufacturing methodologies.

Among various mathematical modeling approaches, Design of Experiments (DoE) is extensively used for the implementation of QbD in both research and industrial settings. In QbD, product and process understanding is the key enabler of assuring quality in the final product. Knowledge is achieved by establishing models correlating the inputs with the outputs of the process. The mathematical relationships of the Critical Process Parameters (CPPs) and Material Attributes (CMAs) with the Critical Quality Attributes (CQAs) define the design space. Consequently, process understanding is well assured and rationally leads to a final product meeting the Quality Target Product Profile (QTPP).

This review illustrates the principles of quality theory through the work of major contributors, the evolution of the QbD approach and the statistical toolset for its implementation. As such, DoE is presented in detail since it represents the first choice for rational pharmaceutical development.     

Suitability of VVC and HEVC for Video Telehealth Systems

Video compression in medical video streaming is one of the key technologies associated with mobile healthcare. Seamless delivery of medical video streams over a resource constrained network emphasizes the need of a video codec that requires minimum bitrates and maintains high perceptual quality. This paper presents a comparative study between High Efficiency Video Coding (HEVC) and its potential successor Versatile Video Coding (VVC) in the context of healthcare. A large-scale subjective experiment comprising of twenty-four non-expert participants is presented for eight different test conditions in Full High Definition (FHD) videos. The presented analysis highlights the impact of compression artefacts on the perceptual quality of HEVC and VVC processed videos. Our results and findings show that VVC clearly outperforms HEVC in terms of achieving higher compression, while maintaining high quality in FHD videos. VVC requires upto 40% less bitrate for encoding an FHD video at excellent perceptual quality. We have provided rate-quality curves for both encoders and a degree of overlap across both codecs in terms of perceptual quality. Overall, there is a 71% degree of overlap in terms of quality between VVC and HEVC compressed videos for eight different test conditions.     

Designing social commerce platforms based on consumers’ intentions

Social commerce has been gaining momentum over the last few years as a novel form of e-commerce, creating substantial changes for both businesses and consumers. However, little is known about how consumer behaviour is influenced by characteristics on social commerce platforms. The purpose of this research is to elucidate how user intentions to purchase and to spread word-of-mouth (WOM) are influenced by characteristics present on social commerce platforms. More specifically, we adopt a uses-and-gratifications perspective and examine the influence of socialising, personal recommendation agents, product selection, and information availability. Partial least squares structural equation modelling analysis is performed on a sample of 165 social commerce users. Outcomes of the analysis indicate that socialising and personal recommendation agents positively influence purchase and WOM intentions, while product selection is found to only enhance purchase intentions. Interestingly, our findings reveal that information availability has no significant effect on purchase and WOM intentions. Finally, we find that when purchase intentions are triggered, they will tend increase consumers’ intentions to WOM.     

Combining SAT Solvers with Computer Algebra Systems to Verify Combinatorial Conjectures

We present a method and an associated system, called MathCheck, that embeds the functionality of a computer algebra system (CAS) within the inner loop of a conflict-driven clause-learning SAT solver. SAT+CAS systems, à la MathCheck, can be used as an assistant by mathematicians to either find counterexamples or finitely verify open universal conjectures on any mathematical topic (e.g., graph and number theory, algebra, geometry, etc.) supported by the underlying CAS. Such a SAT+CAS system combines the efficient search routines of modern SAT solvers, with the expressive power of CAS, thus complementing both. The key insight behind the power of the SAT+CAS combination is that the CAS system can help cut down the search-space of the SAT solver, by providing learned clauses that encode theory-specific lemmas, as it searches for a counterexample to the input conjecture (just like the T in DPLL (T)). In addition, the combination enables a more efficient encoding of problems than a pure Boolean representation. In this paper, we leverage the capabilities of several different CAS, namely the SAGE, Maple, and Magma systems. As case studies, we study three long-standing open mathematical conjectures, two from graph theory regarding properties of hypercubes, and one from combinatorics about Hadamard matrices. The first conjecture states that any matching of any d-dimensional hypercube can be extended to a Hamiltonian cycle; the second states that given an edge-antipodal coloring of a hypercube there always exists a monochromatic path between two antipodal vertices; the third states that Hadamard matrices exist for all orders divisible by 4. Previous results on the graph theory conjectures have shown the conjectures true up to certain low-dimensional hypercubes, and attempts to extend them have failed until now. Using our SAT+CAS system, MathCheck, we extend these two conjectures to higher-dimensional hypercubes. Regarding Hadamard matrices, we demonstrate the advantages of SAT+CAS by constructing Williamson matrices up to order 42 (equivalently, Hadamard up to order \(4\times 42=168\)), improving the bounds up to which Williamson matrices of even order have been constructed. Prior state-of-the-art construction was only feasibly performed for odd numbers, where possible.     

Characterization of Pd–Cu membranes fabricated by surfactant induced electroless plating (SIEP) for hydrogen separation

Pd–Cu composite membranes on microporous stainless steel (MPSS) substrate were fabricated using surfactant induced electroless plating (SIEP). In the SIEP method, dodecyl trimethyl ammonium bromide (DTAB), a cationic surfactant, was used in Pd- and Cu-baths for the sequential deposition of metals on MPSS substrates. The SIEP Pd–Cu membrane performance was compared with membranes fabricated by conventional electroless plating (CEP). The pre- and post-annealing characterizations of these membranes were carried out by SEM, XRD, EDX and AFM studies. The SEM images showed a significant improvement of the membrane surface morphology, in terms of metal grain structures and grain agglomeration compared to the CEP membranes. The SEM images and helium gas-tightness studies indicated that dense and thinner films of Pd–Cu can be produced with shorter deposition time using SIEP method. From XRD, cross-sectional SEM and EDS studies, alloying of Pd–Cu was confirmed at an annealing temperature of 773 K under hydrogen environment. These membranes were also studied for H₂ perm-selectivity as a function of temperature and feed pressure. SIEP membranes had significantly higher H₂ perm-selectivity compared to CEP membranes. Under thermal cycling (573 K – 873 K – 573 K), the SIEP Pd–Cu membrane was stable and retained hydrogen permeation characteristics for over three months of operation.     

Template-assisted synthesis of high packing density SrLi2Ti6O14 for use as anode in 2.7-V lithium-ion battery

SrLi₂Ti₆O₁₄ has been prepared by using mesoporous TiO₂ brookite as a template and reactant. The prepared particles retained the rounded shape of the precursor, leading to high dispersivity and high packing density. The material has been further electrochemically characterized in both half and full cells. It shows good cycling stability and rate capability. A 2.7-V cell has been built by combining a SrLi₂Ti₆O₁₄ anode with a 4-V spinel cathode of LiMn₂O₄. This cell has a higher voltage compared to the 2.5-V LiMn₂O₄/Li₄Ti₅O₁₂ system.     

A simple cost-effective sputtering-based method for micropatterning and materials microstructuring

Patterning of semiconductors results in the fabrication of micro- and nano-structures, which are desired in modern technologies. Such a patterning is usually realized with the help of e-beam-, high-energy ion-, X-ray- or laser-assisted techniques, which demand expensive equipments. In this work we present a simple cost-effective method realized via a radio-frequency driven magnetron-sputtering head in high vacuum. The target is a silicon wafer masked with metallic grids. If the grid is magnetic, e.g., nickel, it is attracted by the magnetic forces of the magnetron, otherwise, magnetic clamps are used. Soft sputtering conditions, i.e., 30-100 Watts are used and the result is a well-ordered micropatterning of the surface with nicely formed pits the size of which is entirely determined by the grid size and the depth by the sputtering power and time. The pits are monitored with the help of Optical and Atomic Force Microscopy. If the masked micropatterned silicon wafer is then used as a substrate, the pits may be partially filled by a material. As a first example we present square-like Co microstructures. The magnetic signal of these Co microstructures is recorded with the help of a computer-driven magneto-optic Kerr effect home-made magnetometer. This patterned material may be used in magnetic recording technology. More examples include the formation of Cu-microcolumns and Pt film microframeworks. For the latter ones, an etching process is applied to prepare porous silicon networks with photoluminescence, which may be used in optoelectronics.