Jetting Micron-Scale Droplets onto Chemically Heterogeneous Surfaces

We report experiments investigating the behaviour of micron-scale fluid droplets jetted onto surfaces patterned with lyophobic and lyophilic stripes. The final droplet shape depends on the droplet size relative to that of the stripes. In particular when the droplet radius is of the same order as the stripe width, the final shape is determined by the dynamic evolution of the drop and shows a sensitive dependence on the initial droplet position and velocity. Numerical solutions of the dynamical equations of motion of the drop provide a close quantitative match to the experimental results. This proves helpful in interpreting the data and allows for accurate prediction of fluid droplet behaviour for a wide range of surfaces.Comment: 14 pages, accepted for publication in Langmui

Control of drop positioning using chemical patterning

We explore how chemical patterning on surfaces can be used to control drop wetting. Both numerical and experimental results are presented to show how the dynamic pathway and equilibrium shape of the drops are altered by a hydrophobic grid. The grid proves a successful way of confining drops and we show that it can be used to alleviate {\it mottle}, a degradation in image quality which results from uneven drop coalescence due to randomness in the positions of the drops within the jetted array.Comment: 3 pages, 4 figure

Utensils-The Major Non-Ferrous Industry of India

Aluminium and brass domestic utensils are major products of the Indian non- ferrous industry amounting to 80 per cent of the total consumption of these metals in India. The utensils industry is thus a much more significant part of the non-ferrous metal industry in India than elsewhere in the world. The annual production of brass utensils is over 40,000 tons, of which only 7000 tons are produced in registered factories , the balance being manufactured by the cottage industries. Aluminium utensils, on the other hand, are mostly manufactured in factories, the annual production being estimated at over 12,000 tons . India is an exporter of aluminium wares and utensils ( 978 tons worth Rs. 61 lakhs in 1951 ) and brass wares and utensils ( worth Rs. 35 lakhs in 1951 ) mostly to the East African, Middle Eastern and South Asian countries. Production of aluminium and copper in India is not able at present to meet the demands of industry and has to be augmented by imports to the tune of Rs. 750 lakhs ( including zinc). Aluminium is the only non-ferrous metal production of which can be readily increased to any large extent in India ; this is being organized under the country's first Five Year Plan. From the point of view of national economics it is necessary that for utensils copper alloys be replaced by aluminium and its alloys in so far as this can be done without any prejudice to the indigenous manufacture of copper.This replacement could be easily effected if conservatism and antipathy of consumers against aluminium utensils could be eradicated by suitable publicity accompanied by improved design and manufacture of aluminium utensils. The need for technical control and standardization is emphasized

An N-port system model for multiwinding transformer based multilevel converters in DC-autotransformer configuration

This paper proposes a time-domain modelling approach for a multi-winding transformer-based multilevel DC/DC converter. Within previous research, multi-winding transformers have been modeled using cantilever models. These models, while simple, have no direct intuitive interpretation. Furthermore, they do not include currents circulating within each individual module and external load currents affecting only some of the modules at the same time. In this paper, a DC/DC converter model that includes the transformer as N-port network with magnetization and stray inductance and conduction losses is proposed. The model is verified using simulations showing both accurate predictions of both, circulating currents within each module and load currents affecting multiple modules

What does a primary care annual review for RA include? A national GP survey

Letter to the edito

The effectiveness of three types of practice in word recognition in grades II and III

Thesis (Ed.M.)--Boston Universit

Multi-active bridge based DC-link balancing of three-level NPC inverters

A common topic in multilevel converter research is the question of DC-link capacitor voltage balancing. For the three-level neutral point clamped converter the balancing is difficult due to the nonlinear nature of the DC-link capacitor voltages. Previous papers solved this problem using sophisticated controllers or additional circuitry connected in parallel to the load. Those solutions however restrict the performance of the output voltage since the controller has to provide a trade-off between output voltage performance and DC-link balancing while the load-connected balancing circuit puts limitations on the applied modulation scheme. In this paper, we connect a multi-active bridge circuit to the DC-link of the converter to overcome this problem. The proposed method is independent of the modulation scheme of the neutral point clamped converter and allows to use of all possible switching states to control the output voltage without taking the effect on the DC-link balance into account. The efficiency of the proposed method is verified using experimental results

Variable Switching Point Model Predictive Control for DC-Link Voltage Regulation of Back-to-Back Converters

In this paper, a novel control method for back-toback converters used in grid-to-motor connections is explored. To increase the robustness of low DC-link capacitances, a control method based on variable switching point model predictive control is proposed. While previous model predictive control methods for the back-to-back converter selected a certain switching state to fulfill all control goals, we use the switching time in addition to the switching state in order to minimise deviations from the target voltage. Choosing a variable switching point provides an additional degree of freedom to the control framework and allows the system to cope with the large number of control variables. In this case, the variable switching point is used to minimize the effects of low DC-link capacitances on the system. This can either be achieved by selecting a switching point that yields low DClink capacitor charging or by selecting a switching point that aims to keep the DC-link voltage close to the reference. The proposed method is verified through numerical simulations and hardware-in-the-loop (HIL) experiments and compared to existing approaches. The results show that it is possible to control the DClink using only the switching point of the converter