Autoparametric Excitation and Self-powered SSHI for Power Enhancement in Piezoelectric Vibration Energy Harvester

© Published under licence by IOP Publishing Ltd. We proposed an autoparametric excitation harvester employing a microfabricated leaf spring for the base beam and a synchronized switch harvesting on inductor (SSHI) interface. Our harvester achieved miniaturization, low threshold acceleration of the autoparametric excitation, and increase in output power, compared with the previous work. The base beam for amplifying the excitation was microfabricated from a stainless steel film, through the photolithography followed by the wet-chemical etching. To trigger the autoparametric excitation, the main and the base beams are designed such that the resonance frequency for the base beam becomes twice higher than that for the main beam. The resonance frequencies obtained in experiment for the main and the base beams were 26.6 and 53.1 Hz, respectively. This study employed a self-powered parallel SSHI interface, which can increase the piezoelectric voltage and thus the output power, consuming only a small portion of the harvested energy. The harvester connected with the self-powered SSHI interface successfully displayed the autoparametric excitation at acceleration greater than 1.0 m/s2, and the output power showed 1.12 mW at the frequency of 53.1 Hz under the acceleration of 2.0 m/s2, which is 1.43-fold increase over the standard AC-DC interface

Numerical Investigation of Mechanically and Electrically Switching SSHI in Highly Coupled Piezoelectric Vibration Energy Harvester

© Published under licence by IOP Publishing Ltd. In aiming to increase output power for piezoelectric vibration energy harvesters, a self-powered synchronized switch harvesting on inductor (SSHI) using an electrical or mechanical switch has considerable attention. However, the advantages and disadvantages of the two switching technique for the self-powered SSHIs remains unclear. In addition, for a harvester with a high electromechanical coupling coefficient k, the piezoelectric damping force, which enhances by the SSHI's voltage increase, is likely to reduce the harvester's displacement and thus lower the output power. We developed simulation technique, and numerically investigated the performance for the electrical switch SSHI (ESS) and for the mechanical switch SSHI (MSS) harvester, considering the feedback of the piezoelectric damping force. The numerical investigation revealed that, for the ESS, the piezoelectric damping force reduces the displacement every switching on at the maximum/minimum displacement, and thus lowers the output power. In contrast, the MSS, in which the switch turns on only when the displacement exceeds the gap distance, achieved a higher output power, and exhibited intriguing phenomena that the output power continues to increase, whereas the displacement is held constant. Therefore, for a harvester with high k, the MSS can outweigh the ESS

A database of water and heat observations over grassland in the north-east of Japan

A highly valuable database of long-term hydrometeorological measurements is presented, containing in situ observations for a period of 37 years from a well-maintained grassland in the north-east of Japan. The observations include shortwave radiation, net radiation, air and dew point temperatures at three elevations, soil temperature at four depths, sensible heat flux, soil heat flux, wind speed, relative humidity, air pressure and precipitation. The heights of measurements are 1.6, 12.5 and 29.5&thinsp;m above ground, with the soil-layer observations at depths of 0.02, 0.1, 0.5 and 1&thinsp;m. This high-quality database includes four temporal resolutions of 10&thinsp;s, 0.5&thinsp;h, 1&thinsp;h and 24&thinsp;h, with the hourly data presented here. Monthly and annual statistics are presented at the database web page of the Center for Research in Isotopes and Environmental Dynamics and Prediction of the University of Tsukuba, http://doi.org/10.24575/0001.198108. We validated the data by comparing them with published data from the local meteorological agency in Tateno operated by the Japan Metrological Agency, including the average, maximum and minimum values of air temperature, shortwave radiation, wind speed, relative humidity and precipitation. We have generated a daily downward longwave radiation time series with a method developed by Kondo and Xu (1997) based on the observations from the database. This constructed time series agrees well with observations collected between 2002 and 2006, as evaluated based on the values of the Nash–Sutcliffe efficiency (=0.947) and percent bias (=1.486). For the whole database, annually averaged values show a positive trend in precipitation, air temperature, shortwave radiation, net radiation and sensible heat flux over the past 37 years, with a negative trend detected for wind speed, soil heat flux and soil temperature.</p

Imaging Oxygen Defects and their Motion at a Manganite Surface

Manganites are technologically important materials, used widely as solid oxide fuel cell cathodes: they have also been shown to exhibit electroresistance. Oxygen bulk diffusion and surface exchange processes are critical for catalytic action, and numerous studies of manganites have linked electroresistance to electrochemical oxygen migration. Direct imaging of individual oxygen defects is needed to underpin understanding of these important processes. It is not currently possible to collect the required images in the bulk, but scanning tunnelling microscopy could provide such data for surfaces. Here we show the first atomic resolution images of oxygen defects at a manganite surface. Our experiments also reveal defect dynamics, including oxygen adatom migration, vacancy-adatom recombination and adatom bistability. Beyond providing an experimental basis for testing models describing the microscopics of oxygen migration at transition metal oxide interfaces, our work resolves the long-standing puzzle of why scanning tunnelling microscopy is more challenging for layered manganites than for cuprates.Comment: 7 figure

Scaling Microseismic Cloud Shape During Hydraulic Stimulation Using In Situ Stress and Permeability

Forecasting microseismic cloud shape as a proxy of stimulated rock volume may improve the design of an energy extraction system. The microseismic cloud created during hydraulic stimulation of geothermal reservoirs is known empirically to extend in the general direction of the maximum principal stress. However, this empirical relationship is often inconsistent with reported results, and the cloud growth process remains poorly understood. This study investigates microseismic cloud growth using data obtained from a hydraulic stimulation project in Basel, Switzerland, and explores its correlation with measured in situ stress. We applied principal component analysis to a time series of microseismicity for macroscopic characterization of microseismic cloud growth in two- and three-dimensional space. The microseismic cloud, in addition to extending in the general direction of maximum principal stress, expanded in the direction of intermediate principal stress. The orientation of the least microseismic cloud growth was stable and almost identical to the minimum principal stress direction. Further, microseismic cloud shape ratios showed good agreement when compared with in situ stress magnitude ratios. The permeability tensor estimated from microseismicity also provided a good correlation in terms of direction and magnitude with the microseismic cloud growth. We show that in situ stress plays a dominant role by controlling the permeability of each existing fracture in the reservoir fracture system. Consequently, microseismic cloud growth can be scaled by in situ stress as a first-order approximation if there is sufficient variation in the orientation of existing faults

Broadly tunable, high-power terahertz radiation up to 73 K from a stand-alone Bi2Sr2CaCu2O8+delta mesa

High-power, continuous, broadly tunable THz radiation from 0.29 to 1.06 THz, was obtained from the outer current-voltage characteristic (IVC) branch of a single stand-alone mesa of the high-transition temperature T-c superconductor Bi2Sr2CaCu2O8+delta. The particular metallic film structures placed both beneath and atop the mesas resulted in more efficient heat dissipation, higher allowed applied dc voltages, larger IVC loops, wider emission temperature ranges, and much broader emission frequency tunability than obtained previously

Computed tomography image using sub-terahertz waves generated from a high-T-c superconducting intrinsic Josephson junction oscillator

A computed tomography (CT) imaging system using monochromatic sub-terahertz coherent electromagnetic waves generated from a device constructed from the intrinsic Josephson junctions in a single crystalline mesa structure of the high-T-c superconductor Bi2Sr2CaCu2O8+delta was developed and tested on three samples: Standing metallic rods supported by styrofoam, a dried plant (heart pea) containing seeds, and a plastic doll inside an egg shell. The images obtained strongly suggest that this CT imaging system may be useful for a variety of practical applications

Geochemical characteristics of back-arc basin lower crust and upper mantle at final spreading stage of Shikoku Basin: an example of Mado Megamullion

AbstractThis paper explores the evolutional process of back-arc basin (BAB) magma system at final spreading stage of extinct BAB, Shikoku Basin (Philippine Sea) and assesses its tectonic evolution using a newly discovered oceanic core complex, the Mado Megamullion. Bulk and in-situ chemical compositions together with in-situ Pb isotope composition of dolerite, oxide gabbro, gabbro, olivine gabbro, dunite, and peridotite are presented. Compositional ranges and trends of the igneous and peridotitic rocks from the Mado Megamullion are similar to those from the slow- to ultraslow-spreading mid-ocean ridges (MOR). Since the timing of the Mado Megamullion exhumation corresponds to the very end of the Shikoku Basin opening, the magma supply was subdued and highly episodic, leading to extreme magma differentiation to form ferrobasaltic, hydrous magmas. In-situ Pb isotope composition of magmatic brown amphibole in the oxide gabbro is identical to that of depleted source mantle for mid-ocean ridge basalt (MORB). In the context of hydrous BAB magma genesis, the magmatic water was derived solely from the MORB source mantle. The distance from the back-arc spreading center to the arc front increased away through maturing of the Shikoku Basin to cause MORB-like magmatism. After the exhumation of Mado Megamullion along detachment faults, dolerite dikes intruded as a post-spreading magmatism. The final magmatism along with post-spreading Kinan Seamount Chain volcanism were introduced around the extinct back-arc spreading center after the opening of Shikoku Basin by residual mantle upwelling

Dysregulated Nephrin in Diabetic Nephropathy of Type 2 Diabetes: A Cross Sectional Study

Podocyte specific proteins are dysregulated in diabetic nephropathy, though the extent of their expression loss is not identical and may be subject to different regulatory factors. Quantifying the degree of loss may help identify the most useful protein to use as an early biomarker of diabetic nephropathy.Protein expression of synaptopodin, podocin and nephrin were quantified in 15 Type 2 diabetic renal biopsies and 12 control patients. We found statistically significant downregulation of synaptopodin (P<0.0001), podocin (P = 0.0002), and nephrin (P<0.0001) in kidney biopsies of diabetic nephropathy as compared with controls. Urinary nephrin levels (nephrinuria) were then measured in 66 patients with Type 2 diabetes and 10 healthy controls by an enzyme-linked immunosorbent assay (Exocell, Philadelphia, PA). When divided into groups according to normo-, micro-, and macroalbuminuria, nephrinuria was found to be present in 100% of diabetic patients with micro- and macroalbuminuria, as well as 54% of patients with normoalbuminuria. Nephrinuria also correlated significantly with albuminuria (rho = 0.89, p<0.001), systolic blood pressure (rho = 0.32, p = 0.007), and correlated negatively with serum albumin (rho = -0.48, p<0.0001) and eGFR (rho = -0.33, p = 0.005).These data suggest that key podocyte-specific protein expressions are significantly and differentially downregulated in diabetic nephropathy. The finding that nephrinuria is observed in a majority of these normoalbuminuric patients demonstrates that it may precede microalbuminuria. If further research confirms nephrinuria to be a biomarker of pre-clinical diabetic nephropathy, it would shed light on podocyte metabolism in disease, and raise the possibility of new and earlier therapeutic targets