Resonant-Type Piezoelectric Pump Driven by Piezoelectric Stacks and a Rhombic Micro Displacement Amplifier

To obtain a high flow rate, a resonant-type piezoelectric pump is designed, fabricated, and studied in this paper. The pump consists of four parts: a piezoelectric vibrator, a pump chamber, a check valve and a compressible space. The designed piezoelectric vibrator is composed of a rhombic micro displacement amplifier, counterweight blocks and two piezoelectric stacks with low-voltage drive and a large output displacement. ANSYS software (Workbench 19.0) simulation results show that at the natural frequency of 946 Hz, the designed piezoelectric vibrator will produce the maximum output displacement. The bilateral deformation is symmetrical, and the phase difference is zero. Frequency, voltage, and backpressure characteristics of the piezoelectric pump are investigated. The experimental results show that at a certain operating frequency, the flow rate and the backpressure of the piezoelectric pump both increase with the increase in voltage. When the applied voltage is 150 Vpp, the flow rate reaches a peak of 367.48 mL/min at 720 Hz for one diaphragm pump, and reaches a peak of 700.15 mL/min at 716 Hz for two diaphragm pumps

Runoff response to climate change and human activities in a typical karst watershed, SW China.

This study aims to reveal the runoff variation characteristics of long time series in a karst region, analyse comprehensively its different driving factors, and estimate quantitatively the contribution rates of climate change and human activities to net runoff variation. Liudong river basin, a typical karst watershed in southwest China, is the study site. Statistical methods, such as linear fitting, the Morlet wavelet analysis, normalized curve and double mass curve, are applied to analyse the runoff of the watershed. Results show that the runoff in the karst watershed during the research period exhibits a three-stage change and the abrupt change points are the years 1981 and 2007: (1) 1968-1980, the runoff initially exhibited a trend of sustained decreasing and then an abrupt fluctuation. The runoff was obviously destroyed through precipitation-producing processes. Improper land utilisation and serious forest and grass destruction intensified the fluctuation variation amplitude of the runoff. (2) 1981-2006, the changing processes of runoff and precipitation exhibited good synchronism. Precipitation significantly affected runoff variation and human activities had a slight interference degree. (3) 2007-2013, the fluctuation range of runoff was considerably smaller than that of precipitation. The significant growth of forest and grassland areas and the increase in water consumption mitigated runoff fluctuation and greatly diminished runoff variation amplitude. According to calculation, the relative contribution rates of precipitation and human activities to net runoff variation with 1981-2007 as the reference period were -81% and 181% in average, respectively, during 1968-1980, and -117% and 217% in average, respectively, during 2007-2013. In general, the analysis of runoff variation trend and of the contribution rate of its main influencing factors in the typical karst watershed for nearly half a century may be significant to solve the drought problem in the karst region and for the sustainable development of the drainage basin

The interannual variations of runoff and precipitation in 46 years (a) and the annual variation curve of the average runoff and precipitation for several years (b).

<p>In Fig 6(a), blue and red bars respectively represent runoff and precipitation. And blue dotted line, red dotted line are respectively the trendline of them. In Fig 6(b), blue bars and red line respectively show the annual distribution of runoff and precipitation, and only the percentage of monthly runoff are showed in the picture.</p

Variations of annual streamflow and precipitation in Liudong River watershed.

<p>Variations of annual streamflow and precipitation in Liudong River watershed.</p

Location map of the study area.

<p>Fig 1 (a) and (b) show the location of research area in the maps of Asia and Guiyang Province, respectively. For Fig 1(a), yellow area shows location of Guizhou. For Fig 1(b), red boundary shows research watershed selected. Yellow area represents karst area and green area represents non-karst area. For Fig 1(c), hydrologic station (red triangle), rainfall station (blue polygons), study area (red line), county border (black dotted line), and river system (blue line) in the study area are presented. And Digital Elevation Model (DEM) also shows on the map. Maps in Fig 1 were generated by ArcGIS 10.2 using the free download data online of the Geospatial Data Cloud (<a href="http://www.gscloud.cn/" target="_blank">http://www.gscloud.cn/</a>) and URL link of the software is <a href="http://www.esri.com/" target="_blank">http://www.esri.com/</a>.</p

Land use transition matrix between 1990-2010(%).

<p>Land use transition matrix between 1990-2010(%).</p

Scatterplot of mean annual temperature and annual runoff.

<p>Scatterplot of mean annual temperature and annual runoff.</p

Spatial distribution maps of land use in 1990 (a), 2000 (b) and 2010 (c).

<p>Forestry, grass land, water area, arid land, paddy field and building lot were classified in maps. Overall accuracy values of three-phase land use vector diagram are 96.89%, 98.55% and 93.17%, and kappa coefficient values are 0.95, 0.97 and 0.93. Maps in Fig 11 were generated by ArcGIS 10.2 and ENVI 5.2 and the URL links of software are <a href="http://www.esri.com/" target="_blank">http://www.esri.com/</a> of both. Three-phase TM images of 1990, 2000 and 2010 from free download data of U.S. Geological Survey (<a href="http://glovis.usgs.gov/" target="_blank">http://glovis.usgs.gov/</a>) were used.</p

Time-frequency structure figure of the real part of Morlet wavelet transform coefficients of annual precipitation (a) and runoff (b).

<p>Fig 7 describe the high and low flow phase structures under different time scales by employing Matlab 7.0. And tone from warm to cold represent high values to low values of the real part of Morlet wavelet transform coefficients.</p

Normalized curve of annual runoff and annual precipitation.

<p>This figure shows the multiyear variation curve after standardization treatment of annual runoff (yellow area) and annual precipitation (green line) in study area. Time periods 1968–1980, 1981–2006 and 2007–2013 are represented by period I, II and III. Period divided on the basis of the goodness of fit between annual runoff and annual precipitation. Annual runoff and precipitation exhibit a good synchronous change relationship in the fluctuation in period II and show a clear separation in period I and III.</p