Newly Synthesized Nonvacuum Processed High-k Polymeric Dielectrics with Carboxyl Functionality for Highly Stable Operating Printed Transistor Applications

Solution-processed polar hydroxyl containing polymers such as poly(4-vinylphenol) are widely utilized in organic filed-effect transistors (OFETs) due to their high dielectric constant (k) and excellent insulating properties owing to the crosslinking through their hydroxyl groups. However, hydroxyl functionalities can function as trapsites, and their crosslinking reactions decrease the k value of materials. Hence, in this study, new solution-processable copolymers containing both carboxyl and hydrophobic functionalities are synthesized. A fluorophenyl azide (FPA) based UV-assisted crosslinker is also employed to promote the movement of polar carboxyl groups toward the bulk region and the hydrophobic functionalities to the surface region, thereby maintaining the high-k characteristics and hydrophobic surface in thin film. Thus, the addition of an FPA crosslinker eliminates the trapsites on the surface, allowing a stable operation and efficient charge transport. Additionally, the solution-processability enables the production of uniform and thin films to yield OFETs with stable and low-voltage driving characteristics. The printed layers are also applied as gate dielectrics for floating gate memory devices and in integrated one-transistor-one-transistor based memory cells, displaying their excellent memory performance. The synthesis and fabrication strategies employed in this study can become useful guidelines for the production of high-k dielectrics for stable OFETs and other applications.     

Speciation of selected trace elements in three Ethiopian Rift Valley Lakes (Koka, Ziway, and Awassa) and their major inflows

The Ethiopian Rift Valley Lakes (ERVLs) are water resources which have considerable environmental, economic and cultural importance. However, there is an increasing concern that increasing human activities around these lakes and their main inflows can result in increased contamination of these water bodies. Information on total concentrations of some trace elements is available for these lakes and their inflows; however, data on the trace element speciation is lacking. Therefore, the objective of this study was to determine the low molecular mass (LMM) trace element species and also, evaluate the influence of flooding episodes on the LMM trace element fractions. At-site size and charge fractionation system was used for sampling of water from the lakes Koka, Ziway and Awassa and their main inflows during the dry and wet seasons. The results showed that chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), and lead (Pb) in Lake Koka and its inflows as well as in Lake Ziway were predominantly present as HMM (high molecular mass, i.e., > 10 kDa) forms, while arsenic (As), selenium (Se), cadmium (Cd) were more mobile during the dry season. In Lake Awassa, all except Cr and Mn were predominantly found as LMM species (low molecular mass, i.e. < 10 kDa) which can be attributed to the high concentrations of LMM DOC (dissolved organic carbon). During the wet season, results from the Lake Koka and its inflows showed that all trace elements were predominantly associated with HMM forms such as colloids and particles, demonstrating that the mobility of elements was reduced during the wet season. The colloidal fraction of elements such as Cr, Ni, and Cd was also correlated with dissolved Fe. As the concentration of LMM trace element species are very low, the mobility, biological uptake and the potential environmental impact should be low.     

Statistical evaluation of High Resolution satellite precipitation products in arid and semi‐arid parts of Ethiopia: a note for hydro‐meteorological applications

The prime objective of this study was evaluating six satellite precipitation products by using standard statistical techniques to assess its capability to provide reliable rain rate (amount) and detect rainfall event correctly. High‐resolution precipitation products, Climate Hazards Group InfraRed Precipitation with Station (CHIRPS), Tropical Applications of Meteorology using Satellite data and ground‐based observations (TAMSAT), Tropical Rainfall Measuring Mission (TRMM 3B42RT v7), Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks (PERSIAN CDR), African Rainfall Climatology (ARC v2) and Climate Prediction Center Morphing technique (CMORPH v1.0) were utilized. Evaluation includes both numerical and categorial metrices. Results indicated that in terms of rainfall amount estimation, TAMSAT has relatively better capability whilst for detecting rain event, ARC v2 was found capable in Eastern Ethiopian landscape. All precipitation products underestimate precipitation amount with profound bias level. These needs a thorough bias correction before utilization of these satellite precipitation products.     

Natural Carbon By‐Products for Transparent Heaters: The Case of Steam‐Cracker Tar

Steam‐cracker tar (SCT) is a by‐product of ethylene production that is in massive quantities globally (>150 × 10⁶ tons per year). With few useful applications, the production of unwanted SCT leads to the need for its costly disposal or burning at the boiler plant. The discovery of new uses for SCT would therefore bring both economic and environmental benefits, although, to date, efforts toward employing SCT in diverse applications have been limited, and progress is further hampered by a lack of understanding of the material itself. Although complex and highly heterogeneous in nature, the molecular composition of SCT has the potential to serve as a diverse and tunable feedstock for wide‐ranging applications. Here, a simple solution‐processing method for SCT that allows its conductivity and optical properties to be controlled over orders of magnitude is reported. Here, by way of example, the focus is on the production of transparent conductive thin films, which exhibit a wide range of transparencies (23–93%) and sheet resistances (2.5 Ω □^–1 to 1.2 kΩ □^–1) that are tuned by a combination of solution concentration and thermal annealing. As transparent Joule heaters, even without optimization, these SCT devices show competitive performance compared to established technologies such as those based on reduced graphene oxide, and surpass the temperature stability limit of other materials. Furthermore, it is demonstrated that laser annealing can be used to process the SCT films and directly pattern transparent heaters on an arbitrary substrate. These results highlight the potential of SCT as a feedstock material for electronic applications and suggest that broader classes of either naturally occurring carbon or produced carbonaceous by‐products could prove useful in a range of applications.     

Full-duplex Distributed Massive MIMO System with Optimal Beamforming and Resource Allocation for WPCN

This paper proposes a joint beamforming and resource allocation scheme to maximize the minimum capacity for wireless powered communication network (WPCN) designed for multi-user distributed massive multi-input multi-output (DM-MIMO) system with full-duplex radio remote heads (RRHs), which enable simultaneous uplink (UL) and downlink (DL) communications. The minimum capacity is maximized by a proposed algorithm based on the non-negative matrix theory. The simulation results have demonstrated that the achievable max-min capacity of the DM-MIMO is considerably higher compared to that of the CMMIMO system. It has also showed that the convergence speed of the proposed algorithm is so fast.     

Regional energy system optimization – Potential for a regional heat market

Energy supply companies and industrial plants are likely to face new situations due to, for example, the introduction of new energy legislation, increased fuel prices and increased environmental awareness. These new prerequisites provide companies with new challenges but also new possibilities from which to benefit. Increased energy efficiency within companies and increased cooperation between different operators are two alternatives to meet the new conditions. A region characterized by a high density of energy-intensive processes is used in this study to find the economic potential of connecting three industrial plants and four energy companies, within three local district heating systems, to a regional heat market, in which different operators provide heat to a joint district heating grid. Also, different investment alternatives are studied. The results show that the economical potential for a heat market amounts to between 5 and 26 million EUR/year with payback times ranging from two to eleven years. However, the investment costs and the net benefit for the total system need to be allotted to the different operators, as they benefit economically to different extents from the introduction of a heat market. It is also shown that the emissions of CO₂ from the joint system would decrease compared to separate operation of the systems. However, the valuation of CO₂ emissions from electricity production is important as the difference of emitted CO₂ between the accounting methods exceeds 650 kton/year for some scenarios.     

Preparation of a chelating poly(β-diketone) resin from poly(vinyl alcohol) and its use in the reversible complexing of metal ions

Summary A water-insoluble poly (-diketone) chelating resin has been prepared by the controlled oxidation of poly(vinyl alcohol) with chromic acid. The polymer forms stable complexes with divalent and trivalent cations, such as Co⁺², Cu⁺², Mn⁺², Ni⁺², Fe⁺³, Au⁺³, and UO₂ ⁺², and removes them completely from dilute aqueous solution. The ions may be recovered quantitatively from the resin complex by elution with dilute aqueous acid and the resin is reusable     

Adding clicks to bricks: a case study of e-commerce adoption by a Catalan small retailer

This paper explores why and how one small business adopted e-commerce. Understanding the importance of a chronological perspective, the paper first develops a conceptual model that explicitly incorporates both different stages of e-commerce functionality and the different phases of the e-commerce adoption process. It relates these to a set of adoption factors classified into contextual, organisational, managerial, and e-commerce-specific categories. The paper explores and illustrates the model with the case history of a wine retailing microenterprise based in Catalonia, Spain that ultimately failed. The presented model is found to provide a workable basis for analysis, and the findings demonstrate the way in which different factors affect different phases of the adoption process. More generally, it finds expected contextual factors such as competitors or customers to have little impact on adoption, which is affected more by informal processes and social relations. The paper ends by questioning the simplicity of progressive e-commerce models that fail to incorporate abandonment of the technology, and fail to account for the lack of business value that some e-commerce projects deliver. The case's chronological approach also identifies the path-dependent manner in which earlier decisions impact later e-commerce trajectories, with short-term, subjective decisions potentially constraining e-commerce in the longer term.     

Large area nanopatterning of alkylphosphonate self-assembled monolayers on titanium oxide surfaces by interferometric lithography

We demonstrate that interferometric lithography offers a fast, simple route to nanostructured self-assembled monolayers of alkylphosphonates on the native oxide of titanium. Exposure at 244 nm using a Lloyd's mirror interferometer caused the spatially periodic photocatalytic degradation of the adsorbates, yielding nanopatterns that extended over square centimetre areas. Exposed regions were re-functionalised by a second, contrasting alkylphosphonate, and the resulting patterns were used as templates for the assembly of molecular nanostructures; we demonstrate the fabrication of lines of polymer nanoparticles 46 nm wide. Nanopatterned monolayers were also employed as resists for etching of the metal film. Wires were formed with widths that could be varied between 46 and 126 nm simply by changing the exposure time. Square arrays of Ti dots as small as 35 nm (λ/7) were fabricated using two orthogonal exposures followed by wet etching.