小波突变性检测技术在变压器局部放电超声定位中的应用

利用试验装置模拟电力变压器局部放电并对传感器接收的超声信号细节进行分析,发现局部放电产生的超声信号具有多个突变点,其中首次突变点是局部放电的起始时间,应当进行标记。但是传统的时延估计方法往往将信号突变峰值作为标记,定位的精度受到影响。小波突变性检测技术可以辨识信号的首次突变点,介绍了小波突变性检测技术的原理并利用该技术对试验装置的局部放电进行定位,结果表明该方法的定位精度明显提高,与传统方法相比定位的绝对误差可以减少1～2cm。     

Flavour compounds of Lavandula angustifolia L. to use in food manufacturing: Comparison of three different extraction methods

Sixty compounds of Lavandula angustifolia L. cultivated in Friuli Venezia Giulia (North-East Italy) were identified and quantified by GC-MS and GC-FID from essential oils obtained by means of hydrodistillation, and from extracts obtained by supercritical CO₂ extraction (SFE) and ultrasound-assisted extraction (US). Using absolute calibration, a true quantification of 1-8 cineol, camphor, linalool, linalyl acetate and β-caryophyllene was carried out. The best extracts, in terms of amount of isolated compounds, flavour quality and stability were those obtained with SFE. Sonication performed at low amplitude for 5 min offered respect to high amplitude a promising alternative to hydrodistillation as a source of lavender flavouring ready to use for alcoholic beverages or/and confectionery products.     

界面层对高强度聚焦超声所致焦斑的影响

用纳米铁磁性颗粒胶合体制作界面层,用同一剂量高强度聚焦超声(HIFU)在该界面层下方不同深度定点辐照.结果显示:焦点上缘与声学界面重合时,HIFU所致焦斑/损伤点(lesion)的体积增大,说明声学界面能够提高治疗效率；当焦点距离界面层10mm时,焦点处HIFU所致焦斑/损伤点的大小和形态与对照组相似,而界面处出现另一...     

Iron determination by FAAS in fish feed and feces after ultrasound-assisted extraction

This paper proposes a method to determine iron in samples of fish feed and feces using ultrasound in the extraction of the analyte and in subsequent quantification by flame atomic absorption spectrometry. Using HCl 0.10 mol L⁻¹ as the extraction solution, the optimal conditions of extraction were found to be: granulometry of the sample <60 μm; a sonication time of five cycles of 10 s and sonication power of 136 W. The method was applied in studies of the availability of iron in four food sources used in the diet of Nile Tilapia. The results obtained with the proposed extraction method allowed us to calculate the coefficients of apparent digestibility of iron in the food sources, which was not possible when using results obtained from samples mineralized by acid digestion.     

B超定位体外震波碎石(ESWL)治疗输尿管中段结石176例分析

目的:观察B超定位行ESWL对输尿管中段结石的治疗效果及分析其技术特点。方法:对176例输尿管中段结石采用ESWL治疗进行回顾性分析。结果:176例输尿管中段结石,治愈率达到95.5%。结论:B超定位行ESWL是治疗输尿管中段结石最简便、最快捷、痛苦最少的一种有效治疗方法。     

Synthesis of Pd-Sn nanoparticles by ultrasonic irradiation and their electrocatalytic activity for oxygen reduction

Nanoparticles of Pd-Sn were prepared under various conditions by applying ultrasonic irradiation, and their electrocatalytic activity for oxygen reduction was evaluated in 0.5 M KOH. The average size of Pd-Sn nanoparticles thus prepared was about 3-5 nm. The Pd in Pd-Sn nanoparticles was found to be mostly in the metallic state. The electrocatalytic activity of the Pd-Sn nanoparticles for the oxygen reduction reaction (ORR) is greater than Pt or Pd nanoparticles in alkaline media. The molar ratio of Pd to Sn metal ions in the synthesizing solution, their initial concentrations, the concentration of ethanol, which increases primary hydrogen radicals during sonolysis, and the concentration of citric acid were found to affect the size distribution of the Pd-Sn nanoparticles, and therefore, those factors controlled the electrocatalytic activity for ORR. Particularly, the concentration of citric acid was found to be important for controlling the surface property on Pd-Sn particles to adjust the electrocatalytic activity for ORR.     

超声无损检测的应用与探讨

超声无损检测是物体无损检测的一种重要方法，几乎应用到所有工业部门。本文回顾了超声无损检测技术的发展历史，阐述了超声无损检测技术应用现状，并展望超声无损检测技术未来发展趋势。     

ULTRASOUND IN THE SUSPENSION SEPARATION METHODS

Investigations were carried out on the effect of the ultrasonic field and some selected chemical compounds on the process of preparing sludges to be dewatered by mechanical devices.

The tests; were performed in a laboratory on real sludges. The processes occurring in sludges due to presence of ultrasonic field and applied chemical reagents were determined on the basis of a commonly used method of determining the sludge dewatering, in both filtration and sedimentation.

The interdependences of value changes of the above mentioned factors and the possibilities of applying ultrasonic waves to intensifying sludge dewatering process were examined. The obtained results confirm the applicability of ultrasonic waves to the process of sludge treatment and prove that the initial assumptions concerning the use of ultrasonic field in the suspension separation methods to be valid.     

Reduction of chloroform formation potential of humic acid by sonolysis and ultraviolet irradiation

This study is concerned with the changes of chloroform formation potential during the reaction of humic acid (HA) and sodium hypochlorite caused by different oxidative pretreatments: ultraviolet (UV) irradiation, ultrasonic (US) irradiation or combined UV-US irradiations. The UV and US decomposition of a reagent HA in water was investigated. The characterization of the oxidized HA sample by UV absorptiometry, synchronous fluorescence spectroscopy and size exclusion chromatography points a synergetic effect of the combined process. The values of the chlorine demand and chloroform formation potential were conventionally determined after a 96 h reaction at neutral pH. It was found that all applied processes decreased the concentration of chloroform but the highest decrease was observed for the UV-US treatment.     

Feasibility of MRI in the diagnosis of acute diverticulitis: initial results

Purpose: The purpose of this study was to evaluate MRI as a diagnostic tool in patients with suspected acute sigmoid diverticulitis. Furthermore, we sought to develop an optimal imaging protocol in these patients.Patients and methods: Eleven patients with suspected acute diverticulitis were included in the study. All patients were imaged in a 1.0 T clinical scanner using a body-array coil. Imaging sequences were single-shot TSE, HASTE-, STIR- and TrueFisp-sequence. All were obtained in the frontal plane. The diagnosis was verified by a single experienced investigator, using ultrasound, and overall clinicopathological outcome.Results: MRI enabled visualization of signs of an acute diverticulitis in all patients. However, the diagnosis of acute diverticulitis was obtained in 10 patients only. The mean imaging time was 17.5 ± 5.5 min. STIR- and TrueFisp-sequences alone displayed all findings, e.g pericolonic exsudation, edema and segmental narrowing, whereas SSTSE and HASTE-sequences showed no additional information. Therefore, it appeared that the imaging protocol could be restricted to STIR- and TrueFisp-sequences.Conclusion: MRI is feasible as a fast, accurate and investigator-independent diagnostic tool in patients with suspected acute diverticulitis. To prove its value in comparison to computed tomography or ultrasound, further studies are needed.