A torque type full tensor gravity gradiometer based on a flexure-strip suspension.

Full tensor gravity gradiometers based on accelerometer pair combination are widely employed in earth resource explorations using gravity gradient measurements. However, the extremely high requirements of accelerometer dynamic range and the scale factor consistency of accelerometer pairs are the two main limitations to further improve their performances. In order to overcome these two extreme challenges, the torque type gravity gradiometer based on the Etövös torsion balance pendulum is re-considered. In this paper, an improved torque type full tensor gravity gradiometer with a flexure-strip suspension is proposed, which balances the mechanical sensitivity and the response time. The proposed gradiometer can be used to measure the full tensor gravity gradient by observing angle variations at three azimuths. The principle and feasibility of the torque type full tensor gravity gradiometer based on a flexure-strip suspension are introduced, and the main noise sources including mechanical thermal noise, position sensing noise, and readout noise are analyzed. A prototype gravity gradiometer with a designed resolution of 2 E/Hz1/2 at 0.1 Hz is constructed (1 E = 10-9/s2), and the experimental results indicate that its resolution comes to 3 E/Hz1/2 at 0.1 Hz, which is mainly limited by the seismic noise. This type of gravity gradiometer can be further improved due to its high potential resolution and independence of matching combination requirement, which allows it to be applied in next generation gravity resource exploration.

[Studies on function of vegetative nervous system in cardiopathic patients with heart-qi deficiency syndromes and heart-yin deficiency syndromes].

To explore the changes of the function of vegetative nervous system in the patients with the syndromes of Heart-Qi Deficiency (HQD) and Heart-Yin Deficiency (HYD), 53 cases of heart diseases were divided into HQD and HYD, the duration between heart beats, differences of blood pressure in the lying and standing position, and urine-catecholamine/24 hrs was determined separately, and compared with control group. The results showed that the duration between heart beats and heart rate in the lying position in those patients of HQD didn't manifest significant difference with control group. But in 78.9% of patients, the differences of heart rate in expiration/inspiration, surpassed 15 beats per minute, and the proportion of 30/15 was less than 1.03. Compared with control group, the difference was significant (P < 0.01). Meantime, the differences of heart rate of lying/standing position was less than 15 beats per minute, and the difference of blood pressure had an increasing tend in 47.4% of the cases. Those patients of HYD didn't show any difference in the above indexes. Urine-catecholamine/24 hrs in both of the two groups surpassed that of control group (P < 0.01). In short, this study showed that syndromes of HQD and HYD both displayed disturbed function of the vegetative nervous system, and their types and severities were correlated with the difference of Syndromes.

High resolution space quartz-flexure accelerometer based on capacitive sensing and electrostatic control technology.

High precision accelerometer plays an important role in space scientific and technical applications. A quartz-flexure accelerometer operating in low frequency range, having a resolution of better than 1 ng/Hz(1/2), has been designed based on advanced capacitive sensing and electrostatic control technologies. A high precision capacitance displacement transducer with a resolution of better than 2 × 10(-6) pF/Hz(1/2) above 0.1 Hz, is used to measure the motion of the proof mass, and the mechanical stiffness of the spring oscillator is compensated by adjusting the voltage between the proof mass and the electrodes to induce a proper negative electrostatic stiffness, which increases the mechanical sensitivity and also suppresses the position measurement noise down to 3 × 10(-10) g/Hz(1/2) at 0.1 Hz. A high resolution analog-to-digital converter is used to directly readout the feedback voltage applied on the electrodes in order to suppress the action noise to 4 × 10(-10) g/Hz(1/2) at 0.1 Hz. A prototype of the quartz-flexure accelerometer has been developed and tested, and the preliminary experimental result shows that its resolution comes to about 8 ng/Hz(1/2) at 0.1 Hz, which is mainly limited by its mechanical thermal noise due to low quality factor.