Simple model of Na D-line shape in sonoluminescence spectra

Technical Physics Letters - A model explaining the Na D-line shape in sonoluminescence (SL) spectra is proposed, which is based on the hypothesis that a complicated profile of this line (involving...     

用声致发光记录脉冲声场中的空化峰

采用频率为1.1MHz的脉冲声波,在声强≤0.5W/cm^2的条件下引发溶液中的声致发光,发现在脉冲宽度为200us-400us的区间内声致发光出现峰值。由于声致发光由超声波空化效应引发,因此,空化效应出现峰值。该实验结果不同于Hill和Flynn等人的实验结论。     

Relationship between the cavitation threshold and maximum sonoluminescence intensity

A phenomenological rule establishing a relationship between the cavitation threshold and the maximum intensity of sonoluminescence (SL) induced by ultrasound is formulated on the basis of experimental data for various liquid media. According to this, the maximum SL intensity attained by varying the intensity of ultrasound within broad limits is always greater in a medium characterized by a higher cavitation threshold.     

单泡声致发光中声压与气泡最大半径的关系

1引言: 当一定幅度的超声波作用于水中时,水中的微小气泡会在声压的驱动下膨胀和塌缩,并不断成长为肉眼可见的气泡,这种现象就是声空化.当超声波的幅度继续增大,水中气泡的膨胀、塌缩更加激烈,会产生短暂发光,这就是声致发光.早期的观察到的声致发光都是来自大量空化泡的集体效应,所以称为多泡声致发光.1992年,Gaitan等人将超声波作用于除气水,实现了单个气泡在水中的悬浮、膨胀、塌缩和发光,发明了单泡声致发光[1],使得人们可以对发光的单个气泡的参数进行具体的研究.     

General expression for the peak asymmetry factor in amplitude spectra

Translated from Izmeritel'naya Tekhnika, No. 10, pp. 55–56, October, 1989.     

Correction of pulse-height spectra for peak pileup effects using periodic and random pulse generators

Peak pileup decrease the counting efficiency and distorts the recorded spectral shape in a pulse-height spectroscopy system. To correct for counting efficiency, it is common to estimate the photon detector input count rate by adding a pulse generator peak, wth known count rate, to a spectrum. A rigorous set of equations is developed to predict the number of piled up counts when either a periodic or a random pulser is used. Using these equations and an empirical treatment of ADC dead-time, expressions for the input count rate are derived for two cases: (1) “sparse” spectra dominated by one or a small number of photon peaks, and (2) “dense” spectra in which photon events occupy most of the spectral channels. Only the first has been treated previously. We provide formulae for the second case both for the situation where the pulser peak is superimposed on the photon region, and where it is separate from the photon region. The pileup equations are incorporated in an iterative routine which corrects for spectral distortion. The analysis has been applied to spectra of ^99mTc and medical bremsstrahlung, measured with a high-purity germanium spectroscopy system.     

Changes in the shape of atomic lines of alkali metals in sonoluminescence spectra of solutions of surfactants and halogenides

The multibubble sonoluminescence spectra of aqueous solutions of sodium dodecyl sulfate, of the mixture of sodium dodecyl sulfate with lithium and potassium chlorides, and of sodium and potassium halogenides were measured near the lines of metals at an ultrasonic frequency of 20 kHz. The Na, Li, and K lines in spectra of surfactant solutions are noticeably narrower than those obtained in solutions of metal chlorides. The width of Na lines in spectra of metal fluorides, chlorides, and iodides remains constant, while that of the K line increases with increasing atomic weight of a halogen. The results are discussed in the context of the effect that the bonding strength of an atom possibly has on the formation of metal lines in sonoluminescence spectra.     

Nonmonotonic behavior of the maximum collapse pressure in a cavitation bubble

Calculations which are relevant to the determination of the maximum collapse pressure generated inside a microbubble as a function of peak pressure in the driving ultrasonic pulse are presented. It is found that above the threshold for transient cavitation, the maximum collapse pressure has a nonmonotonic variation. This result is explained on the basis of phase differences between the external applied acoustic pulse and the resulting bubble response.     

Study of the peak shape in alpha spectra measured by liquid scintillation

Liquid-scintillation counting allows the measurement of alpha and beta activities jointly or only of the alpha-emitting nuclides in a sample. Although the resolution of the alpha spectra is poorer than that attained with semiconductor detectors, it is still an attractive alternative. We describe here attempts to fit a peak shape to experimental liquid-scintillation alpha spectra and discuss the parameters affecting this shape, such as the PSA (pulse-shape analyser) level, vial type, shaking the sample, etc. Spectral analysis has been applied for complex alpha spectra.     

关于声致发光机理研究

1　引　言　　近年来声致发光已成为热门课题 ,其机理研究已取得重要进展。由于其马赫数较大 ,微扰法无法利用 ,故借助于数值方法来求解。在求解实际气泡内的方程组的过程中 ,将气泡表面的振动方程作为动态边界条件 ,而用得最多的是 Rayleigh- Plesset方程 ,简称 R- P方程。本文将就此方程的可靠性作一探讨。此外 ,还对高温粘滞及热传导系数及等离子体物理问题作一些讨论。2　气泡的有限振幅振动　　流体中的欧拉体系的方程组为　　ρjdudt=-△ p (ζ 43η) .u η 2 u　　 dρjdt ρj .u=0　　 p =p(ρj,s,xi)式中 ζ,η是流…     

Features of cavitation and cavitation erosion of waveguides of powerful ultrasonic units at higher-than-average pressure of the media

The features of the acoustic effects of cavitation created by the rod waveguides of powerful ultrasonic magnetostriction units in different liquid media at a pressure to 5 MPa have been investigated. It has been established that, under the conditions of maximum acoustical activity of cavitation realized at the medium's higher-than-average pressure, the erosion damage to the waveguides is of an unusual structurized character and develops from the central part of the end to its periphery. A result of the erosion damage may be the total loss of operating capacity by the waveguides manufactured from the most erosion-resistant materials (stainless steel and titanium alloys) even after a few hours of tests. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 4, pp. 690–696, July–August, 2008.     

Significant G peak temperature shift in Raman spectra of graphene on copper

Linear G peak position temperature dependence in Raman spectra of graphene synthesized by chemical vapor deposition from decane on copper (220) with a shift factor of ?(5.4 ± 0.4) × 10^?2 cm^?1K^?1 was observed. The obtained value substantially exceeds values previously obtained for graphene by other authors, and was associated with the substrate interaction effects.     

Re-examination of the shock wave’s peak pressure attenuation in soils

The paper investigates the problem of a charge exploding in soil and focuses on the characteristics of the shock wave’s peak pressure attenuation. Analysis of existing empirical data observes different attenuation factors for apparently similar certain types of soils whereas for other types of soils there is no significant difference. It was also observed that prediction of the shock wave’s peak pressure with existing power law empirical formulas yields a large discrepancy in comparison to test data. The discrepancy is significant even in case where the specific tested soil parameters are used. These observations among others motivated this study. The power law relationship has been investigated through numerical simulations of the shock wave propagation in different soils. The soil is modeled as a bulk irreversible compressible elastic plastic medium, including full bulk locking and dependence of the current deviatoric yield stress on the pressure. The Lagrange approach and the modified variational difference methods are used to simulate the process. The study shows that the shock wave’s peak pressure attenuation for certain types of soils may be well presented by a power law with a constant exponent, whereas other types of soils may be presented by a power law for a limited distance range and their behavior for a wide distance range is poorly described by a linear relationship on a logarithmic scale but is well represented by a bi-linear or a tri-linear realtionship. These findings explain some of the above mentioned observations.     

Reduction of chemical formulas from the isotopic peak distributions of high-resolution mass spectra

A method has been developed for the reduction of the chemical formulas of compounds in complex mixtures from the isotopic peak distributions of high-resolution mass spectra. The method is based on the principle that the observed isotopic peak distribution of a mixture of compounds is a linear combination of the isotopic peak distributions of the individual compounds in the mixture. All possible chemical formulas that meet specific criteria (e.g., type and number of atoms in structure, limits of unsaturation, etc.) are enumerated, and theoretical isotopic peak distributions are generated for each formula. The relative amount of each formula is obtained from the accurately measured isotopic peak distribution and the calculated isotopic peak distributions of all candidate formulas. The formulas of compounds in simple spectra, where peak components are fully resolved, are rapidly determined by direct comparison of the calculated and experimental isotopic peak distributions. The singular value decomposition linear algebra method is used to determine the contributions of compounds in complex spectra containing unresolved peak components. The principles of the approach and typical application examples are presented. The method is most useful for the characterization of complex spectra containing partially resolved peaks and structures with multiisotopic elements.     

溶液的杂质含量对单泡声致发光的影响

1引言: 在适当除气的液体中,单一气泡可以悬浮在超声驻波场的波腹处,并随声场的频率作周期性的膨胀和收缩,在收缩时将声能量高度集中,会产生发光的现象,称为单泡声致发光(Single Bubble Sonoluminecence)[1].这个现象的发现距今才十几年,还有许多地方需要探索和改进.     

Influence of the structure on the regularities of cavitation wear of eutectic coatings

We analyze the influence of the structure and the main physicomechanical characteristics of eutectic coatings obtained using concentrated sources of energy on the mechanism and kinetics of their cavitation wear. We establish a correlation between the rate of cavitation wear, the size of the structural components, and the mechanical characteristics of the coating. Ukrainian National Technical University “Kiev Polytechnic Institute,” Kiev. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 34, No. 2, pp. 69–74, March–April, 1998.     

Low-threshold cavitation in water using IR laser pulse trains

The low-temperature cavitational disruption by trains of laser pulses was demonstrated in water. The trains used in the experiment were generated by a Raman laser at a wavelength of 1626 nm. The mean value of the fragmentation threshold energy density per pulse in a train was estimated to be equal to 7.2x10(6) J/m(3). The corresponding amplitude of the negative pressure had the order of 6-7 bars at a temperature jump of only about 2 degrees C. This result opens up prospects for developing precision nonthermal cavitational laser surgery.