This paper presents a wideband integrated dielectric sensor with read-out circuit at 207-257 GHz in SiGe BiCMOS technology. The sensing element is equipped by a resonator that provides a bandpass frequency response which is varied in accordance to the carried permittivity change of the device under test. This variation can be sensed and recorded as the change of output voltage of an integrated 207-257 GHz 2 port vector network analyzer readout circuit. The demonstration of aforementioned readout system is verified by measuring the output of mixers as the reference, reflected and measured channel, and the uncalibrated S parameters of readout with different samples.
This article presents a fully differential power-tuning heterodyne on-chip sensing readout system at 240 GHz. The chip enables the measurement of not only the transmission parameter but also the reflection parameter to sense the permittivity of different materials by using four heterodyne mixer-based receiving channels connected to a dielectric sensing element. To facilitate the operation and characterization, three frequency multiplier chains are included to generate the required two identical radio frequency (RF) and one local oscillator (LO) subterahertz signals. RF frequency multiplier chain is configured to enable a tunable power level of the RF signal by using a variable attenuator. A chip prototype using 130-nm silicon–germanium (SiGe) BiCMOS is implemented with a size of 11 mm 2 and dc power consumption of 2.7 W. The measured 10-dB bandwidth of 20.8% is achieved in a frequency range from 207 to 257 GHz with 14-dB measured power-tuning range. The transmission and reflection parameters’ measurements for copper and gummi show a differentiated value in terms of magnitude and phase, which demonstrates the sensing function of the proposed readout system.
Abstract Silicon and oxygen are potential light elements in Earth's core because their stronger affinity to metal observed with increasing temperature posits that significant amounts of both can be incorporated into the core. It was proposed that an Fe–Si–O liquid alloy could expel SiO2 at the core-mantle boundary during secular cooling, leaving the core with either silicon or oxygen, not both. This was recently challenged in a study showing no exsolution but immiscibility in the Fe–Si–O system. Here we investigate the liquidus field of Fe–Si and Fe–O binaries and Fe–Si–O ternaries at core-mantle boundary pressures and temperatures using ab initio molecular dynamics. We find that the liquids remain well mixed with ternary properties identical to mixing of binary properties. Two-phase simulations of solid SiO2 and liquid Fe show dissolution at temperatures above 4100 K, suggesting that SiO2 crystallization as well as liquid immiscibility in Fe–Si–O is unlikely to occur in Earth's core.
In order to analyze the creep behavior of shale rocks, nanoindentation, a common and widely used method was employed in this study. During the experiments, an abnormal displacement behavior was observed in the holding stage which has rarely been reported. It was observed that the displacement increases with holding time followed by a decrease. Further analysis of the results showed that the reduction in the displacement could be due to elastic recovery during the holding period. The dynamic mechanical properties such as storage modulus and hardness were found to first decrease and then increase after the holding time exceeds a certain value which is inferred to elastic recovery. These findings indicate that at the beginning of the holding period, creep behavior would dominate the process while as the holding time proceed, the elastic recovery plays a more important role. Finally, we proposed a new model which includes elastic recovery to quantify the changes in displacement, storage modulus and hardness as a function of holding time.
Accumulating evidence suggests that short- and long-term exposure to ambient fine particulate matter <= 2.5 mu m (PM2.5) during pregnancy is associated with preterm births, yet the results are inconsistent, and the shape of the exposure-response curve is unclear, partially due to the limited studies conducted in areas with high air pollution. Our study evaluated the association between ambient PM2.5 concentration and preterm births in Beijing, China.Daily preterm birth data were collected from a hospital in Beijing during 2006 to 2013; a time-series of daily PM2.5 concentrations during the same period is assembled with measured data at three monitoring sites in Beijing. An extension of the Poisson regression and a time-series model were applied to simultaneously estimate the acute and chronic effects of exposure to PM2.5, with mutual adjustment for short- and long-term exposure as well as for confounders.During the study period, the PM2.5 concentration was 70.4 +/- 60.6 mu g/m(3) and was found to be associated with an increased risk of preterm birth. In the study cohort, a 0.52% (95% confidence interval, CI: 0.09%, 0.96%) and 3.13% (95% CI: 1.92%, 4.35%) increase in preterm births was estimated for each 10-mu g/m(3) increase in short-and long-term exposure, respectively. This association was significantly modified by season (p < 0.05). With mutual adjustments for short- and long-term exposure, a more robust association (3.16%, 95% CI: 1.95%, 4.39%; per 10-mu g/m(3) increment in PM2.5) was observed for chronic effects. The exposure-response relationships for both short- and long-term exposure were linear, without a threshold, over the relatively low exposure range and flattened out at higher concentration levels. The maximum effect for long-term exposure to PM2.5 (33.6%) was much greater than that for short-term exposure (19.9%). These findings indicate that air quality improvements over a long period could yield significant health benefits. (C) 2018 Published by Elsevier B.V.
