Ground-based monitoring of pinatubo aerosols and ozone at L''Aquila, Italy I.—Evidences for ozone depletion during 1991/92 winter months

Summary Possible evidence for stratospheric ozone depletion at northern midlatitudes as a consequence of the Pinatubo aerosol cloud is presented in this work. A ten-month record of aerosol and ozone measurements taken at the lidar station of L'Aquila, Italy, is compared to the 1985–1986 SBUV and SAGE II ozone data. Ozonesonde data collected in the station of Hohenpeissenberg, Germany, and S. Pietro Capofiume, Italy, are used to validate the DIAL measurements corrected for the aerosol presence.     

Optimal interpolation method for intercomparison of atmospheric measurements

Intercomparison of atmospheric measurements is often a difficult task because of the different spatial response functions of the experiments considered. We propose a new method for comparison of two atmospheric profiles characterized by averaging kernels with different vertical resolutions. The method minimizes the smoothing error induced by the differences in the averaging kernels by exploiting an optimal interpolation rule to map one profile into the retrieval grid of the other. Compared with the techniques published so far, this method permits one to retain the vertical resolution of the less-resolved profile involved in the intercomparison.     

简捷内插方法实现实时处理

本文提出用一种简捷的频域补零的内插方法来实现实时处理。该内插法简捷、快速、精确。文中给出了计算机模拟和实际海上信号的处理结果。     

Formulas of the tight-binding interpolation method for crystals of perovskite type

The Slater-Koster interpolation method is used to find the explicit form of the matrix elements of the Hamiltonian between Bloch functions and so make possible the calculation of the energy bands in crystals with a cubic structure of perovskite type. In the nearest-neighbors approximation the energy matrix contains 23 independent parameters. The obtained formulas can be applied to a wide class of substances with the stated structure.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 34–38, February, 1973.We are indebted to R. F. Egorov for a consultation.     

旋转柔性悬臂梁动力学的Bezier插值离散方法研究

在旋转柔性梁变形场描述中,引入Bezier插值离散方法.首先构建旋转运动悬臂梁物理模型,接着采用第二类Lagrange动力学方程和Bezier插值离散方法,在计入柔性梁横向弯曲变形引起的纵向缩短的情况下,推导了旋转柔性梁的刚柔耦合动力学方程,并编制旋转柔性梁的动力学仿真软件,然后通过仿真算例对系统的动力学问题进行研究.最后将仿真结果与有限元法、假设模态法进行分析比较,验证了提出的Bezier插值离散方法的正确性,并得出Bezier插值离散法的计算效率较高;计算精度符合工程实际需要,高速时计算精度大于假设模态法;Bezier插值离散方法在处理大柔性问题时比假设模态法合理.因此在多体系统动力学领域具有优良性能和应用价值的Bezier插值离散方法将具有推广价值.     

Analysis of CV mode selected resonator based on vectorial eigenvector method

The vectorial eigenvector method was applied to compute the cylindrical vector(CV) modes of polarization-dependent resonators and multiple modes in the CV mode selected resonator were tracked. Then, the mode characteristics of CV mode selected resonator depending on the Fresnel number, geometry parameters, and polarization parameters were simulated.When the difference in reflection coefficient between radial and azimuthal polarization is greater than 0.021 for spherical semi-confocal cavity, the radially polarized TM01*mode most probably appears in the resonator due to its lowest loss,which is consistent with an azimuthal polarization-selective resonant cavity. Moreover, the appropriate phase shift factor contributes to suppress non-rotationally symmetrical modes, which promotes the selection of CV modes. The Fresnel number between 2 and 2.5 are the appropriate range of values when the value of geometry parameters g2 is 0.5, both of which decide the effective Fresnel number.     

Experimental verification of an interpolation algorithm for improved estimates of animal position

This article presents experimental verification of an interpolation algorithm that was previously proposed in Jaffe [J. Acoust. Soc. Am. 105, 3168-3175 (1999)]. The goal of the algorithm is to improve estimates of both target position and target strength by minimizing a least-squares residual between noise-corrupted target measurement data and the output of a model of the sonar's amplitude response to a target at a set of known locations. Although this positional estimator was shown to be a maximum likelihood estimator, in principle, experimental verification was desired because of interest in understanding its true performance. Here, the accuracy of the algorithm is investigated by analyzing the correspondence between a target's true position and the algorithm's estimate. True target position was measured by precise translation of a small test target (bead) or from the analysis of images of fish from a coregistered optical imaging system. Results with the stationary spherical test bead in a high signal-to-noise environment indicate that a large increase in resolution is possible, while results with commercial aquarium fish indicate a smaller increase is obtainable. However, in both experiments the algorithm provides improved estimates of target position over those obtained by simply accepting the angular positions of the sonar beam with maximum output as target position. In addition, increased accuracy in target strength estimation is possible by considering the effects of the sonar beam patterns relative to the interpolated position. A benefit of the algorithm is that it can be applied "ex post facto" to existing data sets from commercial multibeam sonar systems when only the beam intensities have been stored after suitable calibration.     

Analysis of materials selected for multilayer diffractive optical elements

An analysis model to optimize the materials selected for multilayer diffractive elements (MLDOEs) is presented with approximate Cauchy dispersion formula of refractive index and the maximum polychromatic integral diffraction efficiency (PIDE). The analysis model presents that the maximum PIDE of MLDOEs consisting of two materials with large Abbe number difference and small partial dispersion difference can be generated. The scope of application and the relationship between diffraction efficiencies of MLDOEs with different material pairs and different design wavelength pairs are presented and simulated with the analysis model of MLDOEs.     

A prediction method of the response probability distribution for arbitrary sound insulation systems

This paper describes a practical evaluation method of the response probability distribution for an arbitrary sound insulation system with a random input noise of arbitrary distribution. Here, the response probability distribution is derived in a fairly simple form using the statistical Hermite expansion-type series expression. The effect of the sound insulation system and the input fluctuation on the resultant probability distribution form is hierarchically reflected in various types of statistics such as the mean, variance and each expansion coefficient. Finally, the proposed evaluation method is experimentally confirmed by applying it to the observed data for typical examples of single- and double-wall insulation system, with white noise and music excitations.     

Evaluation of an adaptive beamforming method for hearing aids.

In this paper evaluations of a two-microphone adaptive beamforming system for hearing aids are presented. The system, based on the constrained adaptive beamformer described by Griffiths and Jim [IEEE Trans. Antennas Propag. AP-30, 27-34 (1982)], adapts to preserve target signals from straight ahead and to minimize jammer signals arriving from other directions. Modifications of the basic Griffiths-Jim algorithm are proposed to alleviate problems of target cancellation and misadjustment that arise in the presence of strong target signals. The evaluations employ both computer simulations and a real-time hardware implementation and are restricted to the case of a single jammer. Performance is measured by the spectrally weighted gain in the target-to-jammer ratio in the steady state. Results show that in environments with relatively little reverberation: (1) the modifications allow good performance even with misaligned arrays and high input target-to-jammer ratios; and (2) performance is better with a broadside array with 7-cm spacing between microphones than with a 26-cm broadside or a 7-cm endfire configuration. Performance degrades in reverberant environments; at the critical distance of a room, improvement with a practical system is limited to a few dB.     

Analysis of an immersed boundary method for three-dimensional flows in vorticity formulation

This article presents numerical analysis and practical considerations for three-dimensional flow computation using an implicit immersed boundary method. The Euler equations, or half a step of the Navier–Stokes equations when using fractional step algorithms, are investigated in their vorticity formulation. The context of flow computation around an arbitrarily shaped body is especially investigated.In conventional immersed boundary methods using vorticity, singular vortex are dispatched over the body surface. In the present study, one prefers using sources of potential velocity field, dispatched on the body, whose nature is not vorticity. Such a formulation is compatible to the Euler equations. In practice, these sources of potential flow produce a velocity through this surface, aiming in practice at cancelling a flow-through velocity.This article focuses on the use of the source-to-flow-through linear application, its properties being the key points for fast convergence. Its self-adjointness, or lack thereof, conditioning and preconditioning aspects are investigated. It follows that computing a velocity field with no-flow-through conditions in complex geometry, when using the source-to-flow-through linear application, can be achieved for 4/3 of the computational cost of standard Poisson equation in a Cartesian box.The robustness of immersed boundaries is especially interesting when used together with vortex-in-cell methods, well known for their robustness in time and their ability to compute accurately convective effects. A few examples, based on real-world geometries, illustrate the method capabilities.     

Efficient method for the extraction of the conditional probability distribution of polarization mode dispersion

A new method for obtaining the probability density function of polarization mode dispersion (PMD) conditioned on the measured PMD value at an offset optical frequency is introduced. This method is advantageous in its ability to accurately and efficiently estimate the conditional distribution far in the tails.     

Nonempirical investigation of the probability for radiationless transitions. I

The probability for radiationless T₁–S₀-transitions was investigated. An expression for the Franck-Condon factor is obtained by means of exact integration, on the basis of the theory of multiphonon transitions. This expression is utilized for the investigation of the radiation-less T₁–S₀-transition in the formaldehyde molecule. It is found that the transition mentioned does not play a large role.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 11, pp. 32–37, November, 1971.     

Nonempirical investigation of the probability for radiationless transitions. II

The dependence of the probability for radiationless transitions on the temperature and energy gap is investigated using the theory of multiphonon transitions. The temperature dependence is found to be extremely weak in the case limited to interval vibrations.Translated from Izvestiya VUZ. Fizika, No. 1, pp. 23–27, January, 1972.     

On peculiarities of the method for determining the probability of lightning striking terrestrial explosive objects

We have described a new probabilistic method for calculating and assessing lightning striking terrestrial explosive objects using a combined criterion for the emergence of upward streamer and leader discharges from the elements of the object being protected and lightning rods taking into account the probabilistic nature of the avalanche–streamer and streamer–leader transitions, the trajectories of a downward stepped lightning leader and lightning current. It has been shown that the disregard of possible formation of uncompleted streamer discharges from the elements of the object in the electric field of a downward lightning leader, which can ignite explosive emission, decreases the rated probability of the object being damaged by a lightning stroke by several times.     

米散射激光雷达剖面数据三次样条垂直水平插值法

传统的空间数据插值方法在米散射激光雷达剖面扫描数据的距离高度显示图可视化应用方面具有一定的局限性.本文分析了米散射激光雷达剖面扫描数据以仰角为基础的空间位置关系与大气参数的空间分布特性,分别在垂直与水平位置上合理选取参考数据,给出位置相关性权重,基于三次样条函数法进行数据变化趋势的平滑性修正,完成缺失数据插值.实验结果表明,该方法能够有效提高米散射大气激光雷达扫描数据空间插值的准确性,插值数据误差小,距离高度显示图图形趋势过度平滑,符合大气参数的整体变化规律.