Influence of deposited metal structures on the failure mechanisms of silicon-based components

Miniaturised silicon-based multilayer chips are nowadays widespread as semiconductor components for the mobile device technology. The use of special processing and integration procedures requires such materials to possess a definite mechanical strength to ensure the functionality of the entire device. The strength and mechanical reliability of such components can be described by the Weibull theory, and is highly influenced by the geometry of the metallisation and other near-surface functional layers. In this work, we attempt to clarify the mechanisms leading to the failure of the metallised side of Si-chip components. The combined use of Finite Elements (FE) and Focused Ion Beam (FIB) analyses allowed recognising that cracks are induced in the metal-oxide-silicon interfacial area well before complete failure of the component. Such cracks have a crucial role in the lower strength and higher Weibull modulus observed on the metallised side.     

Aliphatic 18F-Radiofluorination: Recent Advances in the Labeling of Base-Sensitive Substrates**

Aliphatic fluorine-18 radiolabeling is the most commonly used method to synthesize tracers for PET-imaging. With an increasing demand for ¹⁸F-radiotracers for clinical applications, new labeling strategies aiming to increase radiochemical yields of established tracers or, more importantly, to enable ¹⁸F-labeling of new scaffolds have been developed. In recent years, increased attention has been focused on the direct aliphatic ¹⁸F-fluorination of base-sensitive substrates in this respect. This minireview gives a concise overview of the recent advances within this field and aims to highlight the advantages and limitations of these methods.     

Enhancement of limited water supply network data for deterioration modelling and determination of rehabilitation rate

In the past decades, the main focus of water supply management has moved from construction of new water supply networks to rehabilitation and adaptation of the existing infrastructure. The decision-making process for the rehabilitation management relies heavily on the quality of the applied deterioration model. A recurring problem in the application of such models relates to the quality and availability of network data. These data are often incomplete or unreliable because building measures and damages are only documented properly recently and the recovery of older data is difficult and expensive. A key point in rehabilitation planning is therefore data collection and data reconstruction. Consequently, the aim of this paper is to present a methodology for the enhancement of the available data of water supply networks and the prognosis of the necessary rehabilitation rates under limited data availability. Results indicate that the presented data reconstruction technique has advantages as compared to traditional data extrapolation. It also allows the reconstruction of fragmentary data about existing water supply and wastewater collection systems for the operating utilities. However, it cannot be used for reconstructing failure types as well as the whole information on pipes (e.g. more than two missing information).     

Modeling the effect of a superabsorbent polymer material as desiccant in maize drying using CFD

Maize is an important foodstuff in many countries, and one of most susceptible crops to mold and aflatoxin contamination, which results in considerable postharvest losses and is a burden to consumers’ health, especially in developing countries. The timely drying of harvested maize is essential to halt mold development, ensuring safe storage. The effect of the incorporation of a superabsorbent polymer (SAP) as desiccant in a maize dryer was studied using computational fluid dynamics simulations which accounted for heat and mass transfer between maize, SAP and air. The adsorption capacity and adsorption rate of a commercial SAP material were experimentally determined at different temperature and relative humidity levels, which served as basis for the adsorption model required in the simulations. A maize bulk with SAP packages distributed in it was modeled. Results showed that the SAP material increases the drying rate substantially, particularly in the upper bulk zone where the air reaching it is dehumidified the most. The maize closer to the upper bulk surface starts drying from the beginning of the process instead of lagging for hours or days before the drying front reaches it. An inconvenience of the SAP material is the tendency of granules to swell and stick together as moisture reaches a threshold, which may reduce its performance. Thus, provided this issue is resolved or minimized, SAP materials could successfully assist the rapid drying of maize and other crops. They may also be used during storage to avoid rewetting of the crops during periods of high relative humidity.     

Fouling Detection in an Optically Accessible Microstructured Heat Exchanger

The application of highly effective microstructured devices in continuous production and industrial environments is frequently prone to fouling. A new method is presented to characterize fouling in these microstructures. Thermal fouling of aqueous solutions containing whey protein were used as a test system. Different fouling effects could be observed and distinguished. Integral fouling indicators, such as thermal fouling resistance and pressure drop, as conventional criteria for the occurrence of fouling were compared with direct local optical observation. Low thermal fouling resistances could be detected.     

An LMI approach for H ∞ analysis and control of discrete-time piecewise affine systems

In this paper we investigate some analysis and control problems for discrete-time hybrid systems in the piece-wise affine form. By using arguments from the dissipativity theory for non-linear systems, we show that H X analysis and synthesis problems can be formulated and solved via linear matrix inequalities by taking into account the switching structure of the considered system. In this paper we address the generalized problem of controlling hybrid systems whose switching structure does not depend only on the state but also on the control input.     

Annual vegetation burns across the northern savanna region of Ghana: period of occurrence, area burns, nutrient losses and emissions

This study has assessed the seasonal occurrence of annual vegetation fires and defined inter-seasonally burned area for the different vegetation cover types across Ghana and the northern region of Ghana using 10-year (2001?C2010) remote sensing data. These values were used with fire induced elemental losses to estimate greenhouse gas emissions and net plant nutrient loss due to gross bush fire nutrient transfers and annual atmospheric nutrient depositions. About 21, 68, 10 and 1?% of annual burns across the northern region of Ghana take place in the months of November, December, January and February respectively. As much as 68?±?4 thousand km² (25?C32?%) and 37?±?2.6 thousand km² (46?C60?%) of dry land are annually burned across Ghana and the northern region of Ghana respectively, with 53?C56?% of the total annual burns across the country taking place in the northern region. About 10,100?C28,400 Gg of C, comprising 215?C4,700 thousand Gg of CO₂ equivalent (CO₂, CH₄) potential global warming green house gases and 48?C324 thousand Gg of local pollutants (CO, NO_x) are estimated to be released annually through bush fire occurrence across Ghana. Net negative balance for P between fire-induced nutrient transfers and, annual wet and dry nutrient deposits is of concern given the high P-sorbing mineral content of the soils. The temporal loss of P suggest an input source than wet and dry atmospheric P depositions for the sustenance of the ecosystem or predict a long term threat to regional food production.     

Environmental Control of Triplet Emission in Donor–Bridge–Acceptor Organometallics

Carbene‐metal‐amides (CMAs) are a promising family of donor–bridge–acceptor molecular charge‐transfer (CT) emitters for organic light‐emitting diodes. A universal approach is demonstrated to tune the energy of their CT emission. A blueshift of up to 210 meV is achievable in solid state via dilution in a polar host matrix. The origin of this shift has two components: constraint of thermally‐activated triplet diffusion, and electrostatic interactions between guest and polar host. This allows the emission of mid‐green CMA archetypes to be tuned to sky blue without chemical modifications. Monte‐Carlo simulations based on a Marcus‐type transfer integral successfully reproduce the concentration‐ and temperature‐dependent triplet diffusion process, revealing a substantial shift in the ensemble density of states in polar hosts. In gold‐bridged CMAs, this shift does not lead to a significant change in luminescence lifetime, thermal activation energy, reorganization energy, or intersystem crossing rate. These discoveries offer new insight into coupling between the singlet and triplet manifolds in CMA materials, revealing a dominant interaction between states of CT character. The same approach is employed using materials which have been chemically modified to alter the energy of their CT state directly, shifting the emission of sky‐blue chromophores into the practical blue range.