无缝钢轨中温度对应力非线性超声检测的影响

研究了温度与应力共同作用下的非线性超声响应规律。构建了纵波在无缝钢轨内传播的数学模型,将传统原子间势能引入非线性波动方程,得到了无缝钢轨在自由状态及受约束状态两种情况下超声非线性系数随温度变化的函数关系。在理论分析的基础上,进行了无缝钢轨受约束时内部温度应力变化的实物模拟实验,获得的非线性系数变化趋势与理论预期相一致。研究结果表明:温度和应力都对固体介质非线性影响明显,介质非线性系数随着温度的升高而增大,随着内部压应力的增加而减小。因此,当利用非线性系数检测钢轨纵向应力时,需要对温度的影响进行补偿。     

Effects of ultrasonic reactor design on sewage sludge disintegration

The impact of ultrasound (US) reactor design on cavitation intensity distribution and disintegration efficiency was studied for sewage sludge pre-treatment, using a US flatbed reactor of variable reaction chamber height (RCH, 20–100 mm). Mapping of cavitation intensity and treatment effects was conducted using (i) hydrophone measurements, (ii) aluminum foil tests, and (iii) soluble chemical oxygen demand (COD) analyses. The overall disintegration efficiency was evaluated based on average COD solubilization. The impact of flow on treatment (in)homogeneity was additionally examined using computational fluid dynamics (CFD). Results of all measurement techniques suggest that small RCHs (20 mm, for instance) enable uniform and intense treatments, while large RCHs, which are subjected to strong sound wave attenuation, entail inhomogeneous treatments where large fractions of substrate are no longer exposed to notable cavitation activity. For instance, COD solubilization (relative to alkaline hydrolysis) measured in the channel center dropped from 6.4% to zero as RCH widened from 20 mm to 100 mm. Flow-through sonication further aggravates treatment inhomogeneity due to the high flow rates in the low-cavitation channel centers. Overall disintegration efficiency declined with increasing RCH, showing a drop in average COD solubilization by 73% from RCH = 20 mm to RCH = 100 mm. The drop correlated with average cavitation noise levels (R² = 0.82), indicating that hydrophone measurements may be a suitable tool for US reactor design optimization. Overall, results suggest that reactor geometry has a critical impact on both treatment (in)homogeneity and treatment efficiency and that equal specific energy inputs do not imply equal US treatments.     

Creaming enhancement in a liter scale ultrasonic reactor at selected transducer configurations and frequencies

Recent research has shown that high frequency ultrasound (0.4–3 MHz), can enhance milkfat separation in small scale systems able to treat only a few milliliters of sample. In this work, the effect of ultrasonic standing waves on milkfat creaming was studied in a 6 L reactor and the influence of different frequencies and transducer configurations in direct contact with the fluid was investigated. A recombined coarse milk emulsion with fat globules stained with oil-red-O dye was selected for the separation trials. Runs were performed with one or two transducers placed in vertical (parallel or perpendicular) and horizontal positions (at the reactor base) at 0.4, 1 and/or 2 MHz (specific energy 8.5 ± 0.6 kJ/kg per transducer). Creaming behavior was assessed by measuring the thickness of the separated cream layer. Other methods supporting this assessment included the measurement of fat content, backscattering, particle size distribution, and microscopy of samples taken at the bottom and top of the reactor. Most efficient creaming was found after treatment at 0.4 MHz in single and double vertical transducer configurations. Among these configurations, a higher separation rate was obtained when sonicating at 0.4 MHz in a vertical perpendicular double transducer setup. The horizontal transducer configuration promoted creaming at 2 MHz only. Fat globule size increase was observed when creaming occurred. This research highlights the potential for enhanced separation of milkfat in larger scale systems from selected transducer configurations in contact with a dairy emulsion, or emulsion splitting in general.     

非均匀激光辐照下硅镜热变形对光束传输特性的影响

 使用有限元法计算了硅镜在DF化学激光器非稳腔输出的中空非均匀激光辐照下镜面温升和反射面面形随时间变化的特性,使用65阶Zernike多项式对镜面面形进行了曲面拟合,使用光线追迹的方法计算了平行光束经不同数量硅镜反射后的光束波前分布PV值、Strehl比和Zernike像差系数随时间变化的特性。计算结果表明：在典型的DF激光器输出的中空方形光束辐照下,硅反射镜的热变形将使反射光束产生波前畸变,波前畸变中,y方向像散项占据主要地位,其次是离焦项;随着激光系统中反射镜面数量的增加,高阶像差系数将逐渐增大,且波前PV值与反射次数成线性关系。     

Sonoluminescence intensity and ultrasonic cavitation temperature in organic solvents: Effects of generated radicals

Ultrasonic cavitation in organic solvents remains poorly understood in contrast with aqueous systems, largely because of complexities related to solvent decomposition. In this study, we sonicated different types of organic solvents (i.e. linear alkanes, aliphatic alcohols, aromatic alcohols, and acetate esters) under argon saturation. The average temperature of the cavitation bubbles was estimated using the methyl radical recombination method. We also discuss the effects of the physical properties of the solvents, such as vapor pressure and viscosity, on the cavitation temperature. The average cavitation bubble temperature and sonoluminescence intensity were higher in organic solvents with lower vapor pressure; for aromatic alcohols, these values were particularly high. It was found that the specific high sonoluminescence intensities and average cavitation temperatures exhibited in aromatic alcohols are caused by the highly resonance-stable generated radicals. The results obtained in this study are very useful for acceleration of sonochemical reaction in organic solvents, which are indispensable for organic synthesis and material synthesis.     

Effects of ultrasonic irradiation on crystallization kinetics,morphological and structural properties of zeolite FAU

In this work, NaX zeolite was synthesized and the effect of ultrasound irradiation on reaction kinetics, morphological and structural properties was investigated. Ultrasound was applied, by using a plate transducer (91.8 kHz), for the first time during the crystallization of zeolite NaX, at high temperature, varying the irradiation moment and its duration. Furthermore, ultrasound was applied after the crystallization by a horn-type transducer (20–24 kHz) at low temperature. The effects of irradiated volume (100–300 mL), sonication time (2–10 min) and ultrasound power (10–200 W) were studied with a power intensity up to 100 W/cm². It was found that the application of ultrasound during the first hour of crystallization resulted in 20% reduction of reaction time compared to a standard crystallization. Ultrasound can also reduce the agglomeration degree of the final powder by combining high power and long sonication time. After 5 min sonication time at 0.3 W/mL, the tapped density of the powder was increased by 10%, from 0.37 to 0.41 g/mL. Finally, by scanning electron microscopy (SEM) it was demonstrated that ultrasound can disrupt the agglomerates without affecting the morphology of individual crystals.     

Study on degradation of dimethoate solution in ultrasonic airlift loop reactor

In this work, the degradation of dimethoate solution in ultrasonic airlift loop reactor (UALR) assisted with advanced oxidation processes was studied. The effects of O₃ flow rate, ultrasonic intensity, pH value and reaction temperature on the degradation rate were investigated. UALR imposed a synergistic effect combining sonochemical merit with high O₃ transfer rate. Under the optimal operation conditions: ultrasonic irradiation time was 4 h, O₃ flow rate was 0.41 m³ h⁻¹, ultrasonic intensity was 4.64 W cm⁻², pH value was 10.0, reaction temperature was 25 °C, and initial concentration of dimethoate was 20 mg L⁻¹, degradation rate of dimethoate increased to 90.8%. The experimental results indicated that the method of UALR degradation of organic pollutants in the presence of gas could reduce reaction time and improve degradation rate. UALR was an advisable choice for treating organic waste waters and this device could be easily scale up. Thus this process has wide application prospect in industry.     

Helium effects on the microstructural evolution of reactor irradiated ferritic and austenitic steels

Abstract

Microstructural evolution in neutron irradiated austenitic stainless steels and Cr-Mo ferritic steels is reviewed. Important highlights are: (1) there is a strong correlation between precipitation and void evolution in austenitic steels; (2) helium affects precipitate evolution in austenitic steels, but observations indicate no effect on precipitation in ferritic steels; (3) helium has a pronounced effect on the cavity evolution of the two steel types. Helium effects are explained in terms of the interrelationship between microstructural evolution and point-defect annihilation processes. In stainless steel, three relative regimes of microstructural behavior for different helium generation rate-displacement rate ratios are recognized: (1) “low” He/dpa ratio, where helium effects on the radiation-induced microstructural evolution are negligible or develop slowly, (2) “medium” He/dpa ratio, where helium effects strongly enhance the microstructural changes, and (3) “high” He/dpa ratio, where helium effects are limited to the early development of a high density of fine bubbles which interfere with other radiation-induced microstructural changes, but allow enhanced thermal microstructural evolution to take place instead. The extensive data on austenitic steels fall within these regimes. Ferritic steels are known to be highly resistant to void swelling without helium. It is suggested that enhanced cavity formation due to helium in ferritic steels makes higher swelling a potential concern for fusion reactor applications.     

Modeling and experimental validation of hydrodynamics in an ultrasonic batch reactor

Simulation of hydrodynamics in ultrasonic batch reactor containing immobilized enzymes as catalyst is done. A transducer with variable power and constant frequency (24 kHz) is taken as source of ultrasound (US). Simulation comprises two steps. In first step, acoustic pressure field is simulated and in second step effect of this field on particle trajectories is simulated. Simulation results are compared with experimentally determined particle trajectories using PIV Lab (particle image velocimetry). Effect of varying ultrasonic power, positioning and number of ultrasonic sources on particle trajectories is studied. It is observed that catalyst particles tend to orientate according to pattern of acoustic pressure field. An increase in ultrasonic power increases particle velocity and also brings more particles into motion. Simulation results are found to be in agreement with experimentally determined data.     

Experimental and modelling study of gasoline surrogate mixtures oxidation in jet stirred reactor and shock tube

The oxidation of several mixtures of surrogate for gasoline was studied using a jet stirred reactor and a shock tube. One representative of each classes constituting gasoline was selected: iso-octane, toluene, 1-hexene and ethyl tert-butyl ether (ETBE). The experiments were carried out in the 800-1880 K temperature range, for two different initial pressures (0.2 and 1 MPa), with an initial fuel molar fraction of 0.001. The equivalence ratio varied from 0.5 to 1.5. Each hydrocarbon sub-mechanism was validated using shock tube data. The full mechanism describing the surrogate fuel oxidation is constituted of the sub-mechanisms for each fuel components and by adding interaction reactions between different hydrocarbon fragments. Good agreement between the experimental results and the computations was observed under JSR and shock tube conditions.     

Effects of various factors of ultrasonic treatment on the extraction recovery of drugs from fish tissues

In the present research, a combined extraction method of ultrasound-assisted extraction (UAE) in conjunction with solid phase extraction (SPE) was applied to isolation and enrichment of selected drugs (metoprolol, ticlopidine, propranolol, carbamazepine, naproxen, acenocumarol, diclofenac, ibuprofen) from fish tissues. The extracted analytes were separated and determined by ultra-high performance liquid chromatography with UV detection (UHPLC–UV) technique. The selectivity of the developed UHPLC–UV method was confirmed by comparison with ultra-high performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS) analysis.The important parameters, such as composition of type and pH of extraction solvent, solid/liquid rate volume of extraction solvent and number of extraction cycles were studied. The ultrasonic parameters, such as time, power and temperature of the process were optimized by using a half-fraction factorial central composite design (CCD). The mixture of 10 mL of methanol and 7 mL of water (pH 2.2) (three times) was chosen for the extraction of selected drug from fish tissues. The results showed that the highest recoveries of analytes were obtained with an extraction temperature of 40 °C, ultrasonic power of 300 W, extraction time of 30 min.Under the optimal conditions, the linearity of method was 0.12–5.00 μg/g. The determination coefficients (R²) were from 0.979 to 0.998. The limits of detection (LODs) and limits of quantification (LOQs) for the extracted compounds were 0.04–0.17 μg/g and 0.12–0.50 μg/g, respectively. The recoveries were between 85.5% and 115.8%.     

Changes in MR signal intensity and contrast enhancement of therapeutically irradiated soft tissue

Increased MR signal intensity was observed on T₂-weighted, STIR, and Gadolinium-DTPA-enhanced T₁-weighted images of subcutaneous and muscular soft tissue in 9 of 10 children treated with combination chemotheraphy and radiation therapy (RT) for malignancy in the pelvis or an extremity. Total radiation doses ranged from 59.5 to 65 Gy. Eight of the patients with these changes received hyperfractionated RT (seven for Ewing sarcoma and one for perineal rhabdomyosarcoma); one was treated for pelvic hemangiopericytoma with once-daily fractions. Evidence of soft tissue damage became apparent as early as the sixth week of RT and was seen for up to 69 wk post-RT. There was no clear MR evidence of RT-induced soft tissue damage in one patient, who underwent hyperfractionated RT for pelvic rhabdomyosarcoma. Other MR findings in this group included evidence of bladder wall thickening in three of the seven patients given pelvic RT and increased T₁-weighted signal of irradiated marrow in nine patients. All patients had clinical evidence of skin, soft tissue, or epithelial radiation effects. Increased MR signal intensity secondary to RT-induced damage can be differentiated from widespread tumor by geometric borders that conform to the margins of the radiation field.     

基于Geant4的反应堆临界及动态计算方法

Geant4是一款基于C++面向对象技术的蒙特卡罗开发程序包,可以模拟各种已知粒子与物质之间的相互作用。然而该程序包没有提供临界源功能,无法直接用于反应堆物理计算。因此,利用Geant4提供的基础物理模型和粒子跟踪控制等功能,用两种不同方法实现了临界源的设置,实现了基于Geant4的反应堆静态计算程序G4-RSM和反应堆动态计算程序G4-RDM。两个程序均可用于反应堆临界计算,与MCNP计算结果相对误差在5%以内。G4-RDM程序除可用于临界计算外,还可用于模拟堆内事故工况下的中子学瞬态变化。     

基于Geant4的反应堆临界及动态计算方法

Geant4是一款基于C++面向对象技术的蒙特卡罗开发程序包,可以模拟各种已知粒子与物质之间的相互作用。然而该程序包没有提供临界源功能,无法直接用于反应堆物理计算。因此,利用Geant4提供的基础物理模型和粒子跟踪控制等功能,用两种不同方法实现了临界源的设置,实现了基于Geant4的反应堆静态计算程序G4-RSM和反应堆动态计算程序G4-RDM。两个程序均可用于反应堆临界计算,与MCNP计算结果相对误差在5%以内。G4-RDM程序除可用于临界计算外,还可用于模拟堆内事故工况下的中子学瞬态变化。     

超声波防除积垢节能技术及设备开发

传热设备的积垢问题一直是人们急于解决的一大难题，不仅影响热能利用和生产正常运转，而且会降低产品质量，增加生产成本。通过机理研究、室内试验和工厂试验，揭示了超声波防除积垢的机理，筛选出最佳的声场参数，研制出一种新型的超声波防除积垢设备，室内试验和工厂试验结果表明，超声波技术不但可以防止新垢的产生，而且可以有效地去除已有积垢，显著地提高蒸发系统传热系数和生产能力，可停止使用化学清洗剂，从而延长传热设备使用寿命，避免污染环境，该技术有可能广泛地应用于制糖工业、化肥工业、制浆造纸工业等诸多领域。     

The comparison of ultrasonic disintegration in laboratory and technical scale disintegrators

The study was aimed at finding the impact of the construction of two disintegration instruments (laboratory and technical scale) on the effects of ultrasonic disintegration. The tests were carried out on excess sewage sludge and an increase in soluble COD in the sludge after ultrasonic disintegration was determined. In both types of disintegrators, the sludge was subjected to ultrasounds at the same level of energy density, but the disintegration effects were about three times higher in the case of the technical module application.     

Effect of the luminol signal enhancer on the chemiluminescence intensity and kinetics

The novel p-phenol derivatives, 4-(1-imidazolyl)-phenol, 4-hydroxybiphenyl, 4-hydroxy-4′-iodobiphenyl were employed as highly potent signal enhancers of luminol-hydrogen peroxide (H₂O₂)-horseradish peroxidase (HRP) chemiluminescence (CL) system. The CL reaction conditions were optimized, and the enhancement characteristics of these enhancers were compared with each other. The employment of these molecules greatly affected important assay parameters. Practically, the use of a novel enhancer, even a slightly change of the structure (or concentration) of 4-substituted phenol derivative, could affect assay properties quite dramatically. Furthermore, the use of different enhancers in the luminol–H₂O₂–HRP system can affect not only the intensity of the CL signal, which is well known, but also its kinetics. The experiment data indicated that the stronger intensity was combined with a more rapid decrease of the CL signal.     

The use of peak intensity in diffraction measurements of growth kinetics on surfaces

It is shown that the peak intensity in a diffracted beam can be related to growth kinetics on surfaces only if scaling is obeyed. When scaling is obeyed, the peak intensity is in general related to the square of the average domain size, and not to the fourth power. The finite resolving power of the instrument distorts growth kinetics measurements, giving an apparent growth rate that is less than the actual one.