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Biped robots with dynamic motion control have shown strong robustness in complex environments. However, many motion planning methods rely on models, which have difficulty dynamically modifying the walking cycle, height, and other gait parameters to cope with environmental changes. In this study, a heuristic model-free gait template planning method with dynamic motion control is proposed. The gait trajectory can be generated by inputting the desired speed, walking cycle, and support height without a model. Then, the stable walking of the biped robot can be realized by foothold adjustment and whole-body dynamics model control. The gait template can be changed in real time to achieve gait flexibility of the biped robot. Finally, the effectiveness of the method is verified by simulations and experiments of the biped robot BHR-B2. The research presented here helps improve the gait transition ability of biped robots in dynamic locomotion.
Although altimeters have been widely used to monitor the spatiotemporal variation of sea-ice thickness, they are unable to separate sea-ice freeboard from snow depth. We use a floating GPS deployed on sea ice to derive the freeboard and snow depth near China's Zhongshan Station. Our results show that the standalone floating GPS can monitor freeboard with a precision of 4.2 cm. If time-varying dynamic ocean topography provided by, for example, a bottom pressure gauge is available, then the precision of GPS-derived freeboard can improve to 1.3 cm. The daily snow depth inverted by GPS interferometric reflectometry captures three precipitation events during our experiment, showing that the floating GPS can monitor the variation in snow depth and observe the freeboard variation at the same time. By studying the relationship between freeboard, snow depth and sea-ice thickness, we find that sea-ice thickness will be greatly underestimated by the negative single-point freeboard under the assumption of hydrostatic equilibrium. As a supplement to existing technologies, the GPS-derived freeboard and snow depth can be used both to evaluate the altimeter observations directly and to improve our understanding of the real-time variation of freeboard and snow depth in the experimental area.
Measurement of runaway electron beam (REB) is essential to investigate behavior of runaway electrons produced in nanosecond-pulse gas discharge. A Faraday cup is designed to measure the REB current in nanosecond-pulse discharge when the applied dV/dt is 75 kV/ns. The Faraday cup considers the impendence match with the oscilloscope and the design of the receiving part. The experimental results show that the measured REB current has a rise time of 348 ps and a full width at half maximum of 510 ps. The comparison of the measurement results by the Faraday cup and a REB collector confirm that the Faraday cup is able to measure REB current in nanosecond-pulse discharge. Furthermore, consecutive waveforms of the REB currents show stable results by using the designed Faraday cup. In addition, effects of the interelectrode gap, gas pressure, and cathode material on the REB current are investigated by the designed Faraday cup, and the measurement results provide characteristics of REB current under different conditions. The REB current decreases when the gap spacing or gas pressure increases. REB current increases with the cathode diameter. It indicates that the high-energy electrons are generated not only at the edge of the cathode but also on the side surface of the cathode.
The parameters of X-ray radiation and runaway electron beams (RAEBs) generated at long-pulse discharges in atmospheric-pressure air were investigated. In the experiments, high-voltage pulses with the rise times of 500 and 50 ns were applied to an interelectrode gap. The gap geometry provided non-uniform distribution of the electric field strength. It was founded that at the voltage pulse rise time of 500 ns and the maximum breakdown voltage Um for 1 cm-length gap, a duration [full width at half maximum (FWHM)] of a RAEB current pulse shrinks to 0.1 ns. A decrease in the breakdown voltage under conditions of a diffuse discharge leads to an increase in the FWHM duration of the electron beam current pulse up to several nanoseconds. It was shown that when the rise time of the voltage pulse is of 500 ns and the diffuse discharge occurs in the gap, the FWHM duration of the X-ray radiation pulse can reach ≈100 ns. It was established that at a pulse-periodic diffuse discharge fed by high-voltage pulses with the rise time of 50 ns, an energy of X-ray quanta and their number increase with increasing breakdown voltage. Wherein the parameter Um/pd is saved.
The association between blood pressure (BP) and short-term clinical outcome of acute ischemic stroke is inconclusive. We investigated the association between BP in the first 72 hours following admission and death in-hospital and neurologic deficiency at discharge among patients with acute ischemic stroke.
A total of 2675 acute ischemic stroke patients confirmed by a computed tomography scan or magnetic resonance imaging were included in the present study. Blood pressure in the first 72 hours after admission and other study variables were collected for all ischemic stroke patients. Neurological functions National Institute of Health Stroke Scale (NIHSS) were evaluated by trained neurologists at discharge. The study outcome was defined as death in-hospital and neurologic deficiency (NIHSS≥10) at discharge.
Systolic and diastolic BP were significantly and positively associated with odds of study outcome in acute ischemic stroke. For example, compared to those with a systolic BP<140 mmHg, multiple-adjusted odds ratio (95% confidence interval) of study outcome was 3.29(1.22, 8.90) among participants with systolic BP of 180-219 mmHg, P<0.05; compared to those with a diastolic BP<90 mmHg, multiple-adjusted odds ratio of study outcome was 7.05(1.32, 37.57) among participants with diastolic BP ≥ 120 mmHg, P<0.05.
Systolic BP≥180 and diastolic BP≥120 were significantly and positively associated with death in-hospital or neurologic deficiency at discharge among patients with acute ischemic stroke.
The aim of the study is to explore the association of serum bilirubin levels with admission severity and short term clinical outcomes among acute ischemic stroke patients.
Data were collected from 2361 acute ischemic stroke patients in four hospitals of Shangdong Province during January 2006 and December 2008. National Institutes of Health Stroke Scale (NIHSS) was used to assess admission and discharge severity. NIHSS≥10 at discharge or in-hospital death was defined as short-term clinical outcomes. Logistic regression and trend test were used to examine the association of serum bilirubin levels with admission severity and short term clinical outcomes.
Serum bilirubin levels were significantly and positively associated with admission severity (P for trend <0.05). The age-sex adjusted odds ratios (95% confidential intervals) of NIHSS≥10 associated with the second, third and fourth quartile of total bilirubin/direct bilirubin were 1.245 (0.873, 1.777)/1.276 (0.895, 1.818), 1.484 (1.048, 2.102)/1.628 (1.158, 2.289) and 2.869 (2.076, 3.966)/2.765 (1.996, 3.828), respectively, compared with the lowest quartile; the multivariate adjusted odds ratios of NIHSS≥10 associated with the second, third and fourth quartile of total bilirubin/direct bilirubin were 1.088(0.711, 1.665)/1.436(0.94, 2.193), 1.328(0.877, 2.011)/1.647(1.092, 2.485) and 2.336(1.579, 3.458)/3.079 (2.049, 4.623), respectively, compared with the lowest quartile. However, no association between serum bilirubin levels and short-term clinical outcomes was observed in our study.
Serum bilirubin levels were associated with initial stroke severity closely. Nevertheless, there is no significant relationship between serum bilirubin levels and short-term clinical outcomes among acute ischemic stroke patients.
Carbonaceous sphere@MnO2 rattle-type hollow spheres were synthesized under mild experimental conditions. The as-prepared hollow structures were characterized using scanning electron microscope, transmission electron microscope, x-ray diffraction, x-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, thermogravimetric analysis, and nitrogen adsorption techniques. The characterization data showed the formation of rattle-type hollow structures with a mesoporous MnO2 shell and a carbonaceous sphere core. The composition and shell thickness of the hollow spheres can be controlled experimentally. The capacitive performance of the hollow structures was evaluated by using both cycle voltammetry and charge–discharge methods. The results demonstrated a specific capacitance as high as 184 F/g at a current density of 125 mA/g. The good electrocapacitive performance resulted from the mesoporous structure and high surface area of the MnO2-based hollow spheres.
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