Bioinspired bubble design for particle generation

In this study, we devise a method to generate homogeneous particles from a bubble suspension, with the capability to control loading and the structure of bubbles. Ideally, a process such as this would occur at the interface between daughter bubble formation (instant) and gaseous diffusion (gradual). Interestingly, the budding mechanism in micro-organisms is one that demonstrates features of the desired phenomena (although at a much slower rate), as viruses can eject and evolve structures from their membranes. With these natural concepts, a bubble''s surface can also be made to serve as a platform for particle generation, which transfers significant elements from the initial bubble coating to the newly generated structures. Here, we illustrate this by preparing coated bubbles (approx. 150 µm in diameter) using a hydrophobic polymer, which may be comparable to naturally occurring bubble coatings (e.g. organic matter forming part of bubble coatings in the sea), and dye (which can demonstrate entrapment of smaller quantities of a desired moiety) and then observe particle generation (approx. 500 nm). The process, which may be driven by a polymerosome-forming mechanism, also illustrates how additional uniform sub-micrometre-scale structures may form from a bubble''s surface, which may have also previously been attributed to gas diffusion. In addition, such methods of particle formation from a bubble structure, the incorporation of chemical or biological media via an in situ process and subsequent release technologies have several areas of interest across the broad scientific community.     

Hydration and microstructure of ultra high performance concrete incorporating rice husk ash

Rice husk ash (RHA) and silica fume (SF) have a similar chemical composition and a very high specific surface area, but RHA is not an ultra-fine material like SF. The high specific surface area of RHA originates from its internal porosity. For this reason RHA can be expected to behave differently from SF in terms of the hydration and the resulting microstructure of concrete. This still remains unclear in Ultra High Performance Concrete (UHPC). The objective of this research was to study the effect of RHA on the hydration and microstructure development of UHPC. The results are compared to those obtained with a control sample and a sample made with SF.The results show that the addition of RHA can increase the degree of cement hydration in UHPC at later ages. RHA can also refine the pore structure of UHPC and reduce the Ca(OH)₂ content, but less significantly than SF. The thickness of the interface transition zone (ITZ) between sand particles and cement matrix of all samples is very small at the age of 28 days. The compressive strength of the sample made with RHA after 7 days was higher than that of the control sample and the sample made with SF. It is suggested that the porous structure of RHA and the uptake of water in this porous structure results in a kind of is attributable to the internal water curing of the RHA modified mixture.     

Component reduced all-pass filter with a grounded capacitor and high-impedance input

In the literature, opportunities of the current conveyors with reduced current gains are not adequately emphasised for filter designs. In this study, we show a new all-pass filter (APF) possibility using a current conveyor with half current gain. Although many first-order voltage mode APFs were proposed, most of them either cannot provide high input impedance and grounded capacitor features together or they provide these features with components more than necessary. The presented circuit provides both of these features using reduced number of elements. Spice simulation and experimental results are given to verify the theoretical results.     

All-pass filter for rich cascadability options easy IC implementation and tunability

This paper presents two current-mode all-pass sections, employing only grounded components, which is important from the integrated circuit (IC) implementation point of view. The use of the grounded capacitor allows the IC implementation with standard CMOS technologies. The circuits can be made electronically tunable due to grounded resistors that can be realized by using voltage controlled MOS based resistors. In addition, the circuits have both low input impedance and high output impedance for easy cascadability. The stability analysis proves that the circuits are stable. SPICE simulations and experimental results are in close agreement with the theory.     

New resistorless tunable voltage-mode universal filter using single VDIBA

To increase the universality of the recently introduced voltage differencing inverting buffered amplifier (VDIBA), this letter presents a new voltage-mode (VM) multi-input–single-output (MISO) universal filter. The proposed filter contains only single VDIBA, two capacitors, and one nMOS transistor, operated in triode region, and is used for resonance angular frequency tuning. Since in the structure no resistors are needed the filter can be classified as resistorless. The VM MISO filter compared with other active building block-based counterparts is very simple, it contains only few transistors, and has the smallest size area. Moreover, no component matching is required and it shows low sensitivity performance. The theoretical results are verified by SPICE simulations using TSMC 0.18 μm level-7 SCN018 CMOS process parameters with ±0.9 V supply voltages. In addition, the behavior of the proposed VM filter was also experimentally verified using commercially available integrated circuits OPA660 and AD830.     

Composites of bovine hydroxyapatite (BHA) and ZnO

Composites of calcinated bovine bone-derived hydroxyapatite (BHA), doped with 2.5, 5, and 10 wt.% ZnO were produced by sintering. Scanning electron microscopy (SEM) and X-ray diffraction analysis together with measurements of density, compressive strength, and Vickers microhardness were carried out in the sintered samples. The experimental results showed that the best mechanical properties were achieved in the samples with 5% addition of ZnO. The highest value of compression strength was achieved after sintering at 1200 °C (72 MPa) and of microhardness at 1300 °C (548 HV). Prolong heat treatment at 1300 °C results in vulnerable BHA–ZnO composites to over-firing effect.     

High output impedance current-mode multifunction filter withminimum number of active and reduced number of passive elements

A new current-mode multifunction filter with a single input and three outputs employing only three positive type CCIIs and five passive elements is presented. The proposed filter realises three filter functions simultaneously all at high impedance outputs. No component matching is required and all passive sensitivities are low     

Design of Polarization- and Incident Angle-Independent Perfect Metamaterial Absorber with Interference Theory

A perfect metamaterial absorber is realized and its properties are theoretically, numerically and experimentally investigated at microwave frequencies. In addition, polarization and incident angle independencies are also tested for the structure. Theoretical, numerical and experimental results show that the proposed model has many advantages compared to those in the literature, such as perfect absorption, polarization and incident angle independencies, very simple design, and operation over a sufficiently wide band. A simple configuration is chosen for the proposed model so that it can be easily tuned for other frequency regimes to realize new absorbers for applications such as sensors and stealth technology.     

A novel floating lossy inductance realization topology with NICs using current conveyors

A negative-impedance converter (NIC) is a useful component in the circuit synthesis theory especially for active RC filter design. In this brief, usefulness of the NIC is shown in a floating inductance realization topology that is an alternative application area for the component. A new floating parallel RL realization topology employing two NICs and three passive components is presented.