An implantable mixed-signal CMOS die for battery-powered in vivo blowfly neural recordings

© 2018 A mixed-signal die containing two differential input amplifiers, a multiplexer and a 50 KSPS, 10-bit SAR ADC, has been designed and fabricated in a 0.35 μm CMOS process for in vivo neural recording from freely moving blowflies where power supplied voltage drops quickly due to the space/weight limited insufficient capacity of the battery. The designed neural amplifier has a 66 + dB gain, 0.13 Hz-5.3 KHz bandwidth and 0.39% THD. A 20% power supply voltage drop causes only a 3% change in amplifier gain and 0.9-bit resolution degrading for SAR ADC while the on-chip data modulation reduces the chip size, rendering the designed chip suitable for battery-powered applications. The fabricated die occupies 1.1 mm2 while consuming 238 μW, being suitable for implantable neural recordings from insects as small as a blowfly for electrophysiological studies of their sensorimotor control mechanisms. The functionality of the die has been validated by recording the signals from identified interneurons in the blowfly visual system

Permafrost Hydrology of the Qinghai-Tibet Plateau : A Review of Processes and Modeling

Permafrost extends 40% of the Qinghai-Tibet Plateau (QTP), a region which contains the headwaters of numerous major rivers in Asia. As an aquiclude, permafrost substantially controls surface runoff and its hydraulic connection with groundwater. The freeze–thaw cycle in the active layer significantly impacts soil water movement direction, velocity, storage capacity, and hydraulic conductivity. Under the accelerating warming on the QTP, permafrost degradation is drastically altering regional and even continental hydrological regimes, attracting the attention of hydrologists, climatologists, ecologists, engineers, and decision-makers. A systematic review of permafrost hydrological processes and modeling on the QTP is still lacking, however, leaving a number of knowledge gaps. In this review, we summarize the current understanding of permafrost hydrological processes and applications of some permafrost hydrological models of varying complexity at different scales on the QTP. We then discuss the current challenges and future opportunities, including observations and data, the understanding of processes, and model realism. The goal of this review is to provide a clear picture of where we are now and to describe future challenges and opportunities. We concluded that more efforts are needed to conduct long-term field measurements, employ more advanced observation technologies, and develop flexible and modular models to deepen our understanding of permafrost hydrological processes and to improve our ability to predict the future responses of permafrost hydrology to climate changes

Under-measured daily maximum precipitation from manual gauge observations over the northern regions

Extreme precipitation is a major issue for regional climate, hydrology, and safety of society. Our knowledge of extreme precipitation is poor because of difficulties in gauge observations and biases in regional and global datasets, in particular over the snow dominated regions. Here we investigate and report the distribution and magnitude of under-measured of the maximum daily total precipitation (herein daily maximum precipitation) due to biases in manual gauge observations in the high latitudes (over 45°N), using historical data during 1973–2004. We find remarkable patterns in under-measured of the long-term mean daily maximum precipitation and their association to regional climatic regimes. In contrast to relatively small and large-scale under-measured (less than 5 mm) of daily maximum rainfall, the biases in daily maximum snowfall are very serious, with the regional high values over 15 mm along the Ural Mountains and the coasts of east Asia, Greenland, in particular northern Eurasia coasts. The frequency distribution of observed daily maximum snowfall underestimate significantly the higher risk events over the high latitudes. Furthermore, defining the phase of extreme precipitation should be cautious over the northern regions, in particular the coasts. These results clearly demonstrate the urgent need to review and update precipitation datasets including recent automatic gauge observations and the knowledge of climate regimes and extremes over the broader northern regions

Effects of stratified active layers on high-altitude permafrost warming:A case study on the Qinghai-Tibet Plateau

Seasonally variable thermal conductivity in active layers is one important factor that controls the thermal state of permafrost. The common assumption is that this conductivity is considerably lower in the thawed than in the frozen state, λt=λf 1.5 m) active layers with strong seasonal total water content changes in the regions with summer-monsoon-dominated precipitation pattern. The conductivity ratio can be further increased by typical soil architectures that may lead to a dry interlayer. The unique pattern of soil hydraulic and thermal dynamics in the active layer can be one important contributor for the rapid permafrost warming at the study site. These findings suggest that, given the increase in air temperature and precipitation, soil hydraulic properties, particularly soil architecture in those thick active layers must be properly taken into account in permafrost models

Disturbance-observer-based U-control (DOBUC) for nonlinear dynamic systems

U-model, which is a control-oriented model set with the property of generally facilitate nonlinearity dynamic inversion/cancellation, has been introduced to the Disturbance Observer-Based control (DOBC) methods to improve the performance of the nonlinear systems in this paper. A general DOB based U-Control (DOBUC) framework is proposed to improve the disturbance attenuation capability of U-controller for both linear and nonlinear systems combined with (based on) the U-model-based dynamic inversion which expands the classical linear disturbance observer control to general nonlinear systems. The proposed two-step DOBUC design procedures in which the design of DOB and U-controller are totally independent and separated, enables the establishment of global exponential stability without being subject to disturbances and uncertainties. Comparative simulation experiments with Nonlinear DOBC in controlling Wind Energy Conversion Systems (WECS) and Permanent Magnet Synchronous Motors (PMSM) demonstrated the proposed method