高层大气中的气晖扰动

大气密度在对流层和热层之间的变化相当大，本文通过对陕西天文台夜气晖观测仪测量结果的分析，证实声重波在高层大气中的存在，对青藏高原气象激发声重波进行了初步分析、同时讨论了背景光对夜气晖观测结果的影响。

Impacts of Power Density on Heavy Metal Release During Ultrasonic Sludge Treatment Process

The impact of ultrasonic power density on changes of heavy metals during sludge sonication was inves-tigated. Results showed that ultrasound could release heavy metals from sludge into the supernatant. There existed an effective power density range of 0.8-1.6 W·ml?1 for the release of the total heavy metal; there was little release below 0.8 W·ml?1 and too high power density was adverse to the release. Furthermore, sonication showed selective release of heavy metal from sludge to the supernatant; copper, cadmium and lead were not released by sonication, while arsenic and nickel were released easily and their release ratio could reach 40%. The effective energy range for each heavy metal was also different that 0.8-1.2 W·ml?1 for arsenic, 0.5-1.6 W·ml?1 for nickel, and 0.8-1.6 W·ml?1 for mercury and chrome. The differences among heavy metal release during sonication might be explained by the different distribution of chemical fractions of each metal in sludge. Such selectivity could be used to control heavy metal release during sludge treatment.

Simulation study on ultrasonic tomography for grouted reinforced concrete by finite element

A finite element reconstruction algorithm for ultrasound tomography based on the Helmholtz equation in frequency domain is presented to monitor the grouting defects in reinforced concrete structures.In this algorithm,a hybrid regularizations-based iterative Newton method is implemented to provide stable inverse solutions.Furthermore,a dual mesh scheme and an adjoint method are adopted to reduce the computation cost and improve the efficiency of reconstruction.Simultaneous reconstruction of both acoustic velocity and attenuation coefficient for a reinforced concrete model is achieved with multiple frequency data.The algorithm is evaluated with numerical simulation under various practical scenarios including varied transmission/receiving modes,different noise levels,different source/detector numbers,and different contrast levels between the heterogeneity and background region.Results obtained suggest that the algorithm is insensitive to noise,and the reconstructions are quantitatively accurate in terms of the location,size and acoustic properties of the target over a range of contrast levels.

Outcome prediction in severe traumatic brain injury with transcranial Doppler ultrasonography

Objective: To investigate the value of transcranial Doppler (TCD) ultrasonography in evaluating the outcome of severe traumatic brain injury and to correlate the TCD values with intracranial pressure (ICP) and cerebral perfusion pressure (CPP) monitoring. Methods: A prospective study was conducted to evaluate the contribution of TCD ultrasonography to neurological outcome in a series of 96 severe traumatic brain injury patients. The quantitative variables of TCD ultrasonography included the mean blood flow velocity of the middle cerebral artery (MCA) and pulsatility index within the first 24 hours of admission. The ICP and CPP values were also recorded. Outcome in 6 months postinjury was evaluated using the Glasgow Outcome Scale (GOS 4 5 was considered as "good" and GOS 1 3 as "poor"). Results: The mean blood flow velocity of the MCA was larger than 40 cm/s in 30 (51%) patients with good outcome whereas it was less than 40 cm/s in 27 (73%) patients with poor outcome (P< 0.025 ). The mean PI in cases of good outcome (34 patients, 57%) was lower than 1.5 whereas in poor outcome (30 patients, 83%) was higher than 1.5 (P< 0.001 ). The correlations of ICP and CPP to pulsatility index were statistically significant (P< 0.01 ). Conclusions: TCD ultrasonography is valid in predicting the patients outcome of 6 months and correlates significantly with ICP and CPP values when it is performed in the first 24 hours of severe traumatic brain injury.

Science Letters:A new coding scheme in coded ultrasound using staggering repetition interval

The increase of frame rate,though with the potential in a coded ultrasound system,is generally concomitant with the simultaneous transmission of a number of apertures,and in consequence leads to increased cross-talks between different apertures.In view of this,a new coding scheme using staggering repetition interval was proposed.The transmitting signals were constructed by repeating the two(or more) modulated codes using staggering repetition interval,and then allocated to and transmitted simultaneously among different apertures.The decoding process was based on the subsection-matched filter under the assistance of different matched filters for different apertures.At last the outputs of subsection-matched filtering were added together.Staggering changed the positions of cross-correlation(CC) peaks from coinciding,which resulted in an effective reduction of CC.Our theoretical analysis and simulations showed that,the coding scheme can be used to reduce cross-talk,and a good cross-talk reduction will be achieved if the staggering delay is kept in an appropriate range.

Preparation and characterization of Al/B/Fe_2O_3 nanothermites

A sol-gel synthetic approach combined with an ultrasonic method was utilized to prepare Al/B/Fe2O3 nanothermites.The structure and properties of the prepared nanothermites were characterized by thermogravimetric analysis,differential scanning calorimetry,scanning electron microscopy,X-ray diffraction,and an impact sensitivity test.The results verified that the nano-aluminum and the micro-boron were uniformly dispersed in the pores of the iron oxide gel.The heat of the prepared Al/B/Fe2O3 nanothermites was 1.3 times that of the simple physically mixed sample.In addition,the heat of the combustion test showed that these materials were indeed energetic.Small-scale safe experiments also showed that the prepared materials through sol-gel were relatively insensitive to standard impact.

Observation and analysis of whistler-mode wave and electrostatic solitary waves within density depletion near magnetic reconnection X-line

The PWI/WFC data onboard Geotail during one burst time interval when Geotail is skimming a magnetic reconnection diffusion region in the near-Earth magnetotail is carefully analyzed.Both the whistler-mode wave and the electrostatic solitary wave are found within the region with density depletion on the boundary layer near the magnetic reconnection X-line.The whistler-mode wave is electromagnetic whistler wave propagating quasi-parallel to the ambient field with a small angle between the wave vector and the ambient magnetic field.The whistler-mode wave associated with ESWs suggests that enhanced electromagnetic whistler-mode fluctuations can also be generated after the decay of the ESWs,which is different from the 2-D PIC simulation results.