Dynamic simulation of a peristaltic micropump considering coupled fluid flow and structural motion

This paper presents lumped-parameter simulation of dynamic characteristics of peristaltic micropumps. The pump consists of three pumping cells connected in series, each of which is equipped with a compliant diaphragm that is electrostatically actuated in a peristaltic sequence to mobilize the fluid. Diaphragm motion in each pumping cell is first represented by an effective spring subjected to hydrodynamic and electrostatic forces. These cell representations are then used to construct a system-level model for the entire pump, which accounts for both cell- and pump-level interactions of fluid flow and diaphragm vibration. As the model is based on first principles, it can be evaluated directly from the device's geometry, material properties and operating parameters without using any experimentally identified parameters. Applied to an existing pump, the model correctly predicts trends observed in experiments. The model is then used to perform a systematic analysis of the impact of geometry, materials and pump loading on device performance, demonstrating its utility as an efficient tool for peristaltic micropump design

Do the technical indicators reward chartists? A study on the stock markets of China, Hong Kong and Taiwan

This paper studies the profitability of applying technical analysis that signals the entry and exit from the stock market in three Chinese stock markets - the Shanghai, Hong Kong and Taiwan Stock Exchanges. The Simple Moving Average (MA) and its extensions, Exponential MA, Dual MA, Triple MA, MACD and TRIX for both long and short strategies are examined. Applying the trading signals generated by the MA family to the Greater China markets, significantly positive returns are generated, which outperform the buy-and-hold strategy. The cumulative wealth obtained also surpasses that of the buy-and-hold strategy regardless of transaction costs. In addition, we study the performance of the MA family before and after the 1997 Asian Financial Crisis and find that the MA family works well in both sub-periods and in different market conditions of bull runs, bear markets and mixed markets. That technical analysis can forecast the directions of these markets implies that the three China stock markets are not efficient.Technical analysis, Moving Average, buy-and-hold strategy

Surface micromachined electrostatically actuated micro peristaltic pump

An electrostatically actuated micro peristaltic pump is reported. The micro pump is entirely surface micromachined using a multilayer parylene technology. Taking advantage of the multilayer technology, the micro pump design enables the pumped fluid to be isolated from the electric field. Electrostatic actuation of the parylene membrane using both DC and AC voltages was demonstrated and applied to fluid pumping based on a 3-phase peristaltic sequence. A maximum flow rate of 1.7 nL min^–1 and an estimated pumping pressure of 1.6 kPa were achieved at 20 Hz phase frequency. A dynamic analysis was also performed with a lumped-parameter model for the peristaltic pump. The analysis results allow a quantitative understanding of the peristaltic pumping operation, and correctly predict the trends exhibited by the experimental data. The small footprint of the micro pump is well suited for large-scale integration of microfluidics. Moreover, because the same platform technology has also been used to fabricate other devices (e.g. valves, electrospray ionization nozzles, filters and flow sensors), the integration of these different devices can potentially lead to versatile and functional micro total analysis systems (µTAS)

Enhanced Gas-Flow-Induced Voltage in Graphene

We show by systemically experimental investigation that gas-flow-induced voltage in monolayer graphene is more than twenty times of that in bulk graphite. Examination over samples with sheet resistances ranging from 307 to 1600 {\Omega}/sq shows that the induced voltage increase with the resistance and can be further improved by controlling the quality and doping level of graphene. The induced voltage is nearly independent of the substrate materials and can be well explained by the interplay of Bernoulli's principle and the carrier density dependent Seebeck coefficient. The results demonstrate that graphene has great potential for flow sensors and energy conversion devices

Non-financial hurdles for human capital accumulation : landownership in Korea under Japanese rule

This paper suggests that inequality in landownership is a nonfinancial hurdle for human capital accumulation. It is the first to present evidence that inequality in landownership had an adverse effect on the level of public education in the Korean colonial period. Using a fixed effects model, the present research exploits variations in inequality in land concentration across regions in Korea and accounts for the unobserved heterogeneity across these regions. The analysis establishes a highly significant adverse effect of Land inequality on education in the Korean colonial period