Analysis of concentration polydispersity in mixed liquid–liquid systems

Inter-phase mass transfer for each chemical component is typically modelled with one material balance for the continuous and one for the dispersed phase. This approach contains inherently an assumption that the phases are well mixed at least locally. For the dispersed phase, this assumption requires that breakage and coalescence are significantly faster compared to the mass transfer, which is not necessarily true. It is important to carry out preliminary assessment whether the dispersed phase segregation is important and should be considered in subsequent modelling efforts, before embarking heavy multidimensional simulations where all possible dispersed phase variations are considered. In this work, relevant time scales are first defined and used for analyzing dispersed phase mixedness in liquid–liquid systems with mass transfer between the phases. Then appropriate dispersed phase modelling tools for the purpose are evaluated. Simple droplet number density based analysis is shown to estimate mixedness reasonably well. Furthermore, the drop number density approach is also shown to predict the average drop sizes with almost comparable accuracy than the full population balances.     

Energy harvesting with a cymbal type piezoelectric transducer from low frequency compression

In this paper a piezoelectric energy harvester based on a Cymbal type structure is presented. A piezoelectric disc ?35?mm was confined between two convex steel discs ?35?mm acting as a force amplifier delivering stress to the PZT and protecting the harvester. Optimization was performed and generated voltage and power of the harvester were measured as functions of resistive load and applied force. At 1.19?Hz compression frequency with 24.8?N force a Cymbal type harvester with 250?μm thick steel discs delivered an average power of 0.66?mW. Maximum power densities of 1.37?mW/cm³ and 0.31?mW/cm³ were measured for the piezo element and the whole component, respectively. The measured power levels reported in this article are able to satisfy the demands of some monitoring electronics or extend the battery life of a portable device.     

Process cycle optimization in press forming of paperboard

Three‐dimensional forming of paperboard is commonly done by a press forming process, which has been widely researched. However, the process cycle of the press forming of paperboard trays has not yet been completely optimized due to limited adjustability and unsophisticated mechanical structure of commonly used forming equipment. The object of this study is to optimize the force curve of stroke to improve product quality without compromising the production rate using LUT Adjustable Packaging Line prototype for practical evaluation of formability and multibody dynamics software MSC Adams for simulation. Several process parameters were investigated with different process cycles to study their effect on the quality of the formed products. With optimized male mould speed, acceleration and speed of the blank could be reduced, which led to significantly reduced rupturing tendency without compromising the production speed. It was also found that a constant blank holding force should be used to achieve acceptable tray quality, although this results in a significantly increased surface pressure applied to the formed substrate. It was also discovered that a novel male mould attachment, which included a pressing force adjustment system that utilized a spring set with an adjustable preload, made it possible to control the force distribution between different forming tools during the dwelling phase of the process cycle in an improved way. Utilization of the method used in this paper leads to a better tray quality without compromising the production efficiency. Furthermore, this can increase the number of possible package applications for sustainable materials, such as paperboard.     

Ion-implanted capacitively coupled silicon strip detectors with integrated polysilicon bias resistors processed on a 100 mm wafer

Double-sided silicon strip detectors with integrated coupling capacitors and polysilicon resistors have been processed on a 100 mm wafer. A detector with an active area of 19 × 19 mm² was connected to LSI readout electronics and tested. The strip pitch of the detector is 25 μm on the p-side and 50 μm on the n-side. The readout pitch is 50 μm on both sides. The number of readout strips is 774 and the total number of strips is 1161. On the p-side a signal-to-noise of 35 has been measured using a ⁹⁰Sr β-source. The n-side has been studied using a laser.     

Vertical external-cavity surface-emitting laser for dual-wavelength generation

We report an optically pumped vertical external-cavity surface-emitting laser that is designed for emission at two wavelengths simultaneously. Single transverse mode continuous-wave (CW) operation is demonstrated at the wavelengths of 984 and 1042 nm. The device produces a CW optical power of 140 mW for the 984-nm component and 115 mW for the 1042-nm component, exhibiting over 10% efficiency. At a high pump power, self-pulsation of the components appeared on top of the CW-mode components. The maximum total output of 1 W was obtained at the pump power of 9 W.     

Pressure profiles measured within lubricated contacts in presence of dented surfaces. Comparison with numerical models

In this paper, dented contacts have been studied in an EHL ball on disk device under pure sliding conditions. Dents with diameter of half the Hertzian contact radius were positioned in the center of the contact. The measured pressure profiles, obtained from Raman microspectrometry, are very different from those expected. A huge pressure peak is observed at the place where the lubricant leaves the dent, leading to very high pressure gradients. The effect of the dent shoulders is also visible. These results are discussed and compared to numerical ones. Finally, some consequences on life prediction of dented surfaces are presented.     

Self‐Propelling and Positioning of Droplets Using Continuous Topography Gradient Surface

A radial pattern with continuous topography gradient is presented, which induces a continuous inward wettability gradient and enables self‐propelling and accurate positioning of droplets to the pattern center. The effect of droplet size and wettability gradient of the pattern on the self‐mobility of droplets is investigated. The wettability gradient is found to increase towards the pattern center, enhancing the self‐motion of droplets at the inner area of the pattern. Moreover, larger droplets give rise to a larger solid‐liquid contact diameter, which helps to satisfy the self‐motion criteria that the advancing contact angle at front edge is smaller than the receding contact angle at rear edge. Consequently, a larger droplet size favors self‐motion initiated from the outer area of the pattern. The continuous topography gradient employed here allows the flexible dispensing of droplets at any place within a certain range, and avoids potential pinning defects to droplets at geometrical discontinuities. An average self‐motion velocity up to 4.0 cm/s for microliter‐sized droplets is achieved on the resultant patterned surface.     

Stacked GaAs quantum dots fabricated by refilling of self-organized nanoholes: optical properties and post-growth annealing

We study the photoluminescence and impact of post-growth annealing of stacked, strain-free GaAs quantum dots fabricated by refilling of self-organized nanoholes using molecular beam epitaxy. Temperature- and power-dependent photoluminescence studies reveal an excellent optical quality of the quantum-dot stack. After high-temperature post-growth annealing only slight blueshifts and an increase in full width at half-maximum of the photoluminescence peak are observed, indicating very high-temperature stability and crystalline quality of the stacked GaAs quantum-dot structure.