Principle of stationary phase for propagating wave packets in the unidimensional scattering problem

We point out some incompatibilities which appear when one applies the stationary phase method for deriving phase times to obtain the spatial localization of wave packets scattered by a unidimensional potential barrier. We concentrate on the above barrier diffusion problem where the wave packet collision implies the possibility of multiple reflected and transmitted wave packets, which, depending on the boundary conditions, can overlap or stand in relative separation in space. We demonstrate that the indiscriminate use of the method for such a particular configuration leads to paradoxical results for which the correct interpretation, confirmed by analytical/numerical calculations, imposes the necessity of the appearance of multiple peaks as a consequence of multiple reflections by the barrier steps. Also at Instituto de Física Gleb Wataghin, UNICAMP, PO Box 6165, 13083-970 Campinas, SP, Brazil.     

Temperature and pressure dependences of Zn-doped GaN

The electroluminescence spectrum of Zn-doped GaN is independent of uniaxial pressure up to kbars and of temperature in the range 100–300 K. This work was done during a one month visit by Dr. Pankove at UNICAMP, made possible through a grant from PNUD. Financial support from TELEBRAS and FAPESP is also acknowledged.     

One-loop effective action for non-local modified Gauss–Bonnet gravity in de Sitter space

We discuss the classical and quantum properties of non-local modified Gauss–Bonnet gravity in de Sitter space, using its equivalent representation via string-inspired local scalar-Gauss–Bonnet gravity with a scalar potential. A classical, multiple de Sitter universe solution is found where one of the de Sitter phases corresponds to the primordial inflationary epoch, while the other de Sitter space solution—the one with the smallest Hubble rate—describes the late-time acceleration of our universe. A Chameleon scenario for the theory under investigation is developed, and it is successfully used to show that the theory complies with gravitational tests. An explicit expression for the one-loop effective action for this non-local modified Gauss–Bonnet gravity in the de Sitter space is obtained. It is argued that this effective action might be an important step towards the solution of the cosmological constant problem.     

Development of an algorithm for automatic detection and rating of squeak and rattle events

A new algorithm for automatic detection and rating of squeak and rattle (S&R) events was developed. The algorithm utilizes the perceived transient loudness (PTL) that approximates the human perception of a transient noise. At first, instantaneous specific loudness time histories are calculated over 1-24 bark range by applying the analytic wavelet transform and Zwicker loudness transform to the recorded noise. Transient specific loudness time histories are then obtained by removing estimated contributions of the background noise from instantaneous specific loudness time histories. These transient specific loudness time histories are summed to obtain the transient loudness time history. Finally, the PTL time history is obtained by applying Glasberg and Moore temporal integration to the transient loudness time history. Detection of S&R events utilizes the PTL time history obtained by summing only 18-24 barks components to take advantage of high signal-to-noise ratio in the high frequency range. A S&R event is identified when the value of the PTL time history exceeds the detection threshold pre-determined by a jury test. The maximum value of the PTL time history is used for rating of S&R events. Another jury test showed that the method performs much better if the PTL time history obtained by summing all frequency components is used. Therefore, rating of S&R events utilizes this modified PTL time history. Two additional jury tests were conducted to validate the developed detection and rating methods. The algorithm developed in this work will enable automatic detection and rating of S&R events with good accuracy and minimum possibility of false alarm.     

超声辅助磨削杯形砂轮变幅器设计与试验*

超声辅助磨削在硬脆材料的加工中应用广泛。为研制以杯形砂轮为加工工具的超声辅助磨削主轴附件式工具系统,建立了杯形砂轮变幅器的理论模型,推导了其频率方程,并通过Matlab开发了杯形砂轮变幅器设计软件。利用该软件结合有限元分析对杯形砂轮变幅器进行了设计。将研制的杯形砂轮变幅器与BT40刀柄一体化外套筒、导电滑环装配组成了杯形砂轮超声辅助磨削主轴附件式工具系统。对该超声振动系统进行了阻抗分析试验及超声谐振试验,结果表明,该超声振动系统阻抗性能较好,能够使杯形砂轮产生稳定的超声振动,验证了所提出的设计方法的正确性,为主轴附件式超声磨削装置的设计提供了理论参考。     

Consistency Conditions for Probabilities of Quantum Histories

In the framework of the histories approach to quantum mechanics developed by Griffiths and Omnès, we consider the question of the uniqueness of the probability assigned to the histories; the question was solved by Omnès only in special cases. We find conditions which ensure uniqueness of such probability in the general case.     

Effects of double stratification and heat flux damping on convective flows over a vertical cylinder

Unsteady free convection flows of viscous fluids over a vertical circular cylinder are investigated by taking in consideration thermal and mass stratification and the thermal memory effects. The mathematical model of thermal transport is based on the fractional generalized Fourier's law for thermal flux with the kernel of power-law kind. In this model the histories of the temperature gradient influence the thermal and mass transport process and the fluid motion. On the cylinder's surface the temperature (or the thermal flux) and solute concentration are constant. Solutions in the transformed domain for the perturbation temperature and concentration and fluid velocity are determined using the Laplace transform coupled with the classical method for the ordinary non-homogeneous differential equations. The inverse Laplace transforms are obtained numerically by employing the Stehfest's algorithm. Solutions for the case corresponding to classical Fourier's law are obtained as particular case of general solutions by taking the memory parameter equal to zero. The influence of the thermal memory and of thermal and mass stratifications is numerically and graphically analyzed by using the software Mathcad 15.     

Use of Speech Recognition Software: A Vocal Endurance Test for the New Millennium?

Speech recognition software for the personal or office computer is a relatively new area of technology. As the number of these products has increased so has use of this software. Some individuals will employ speech recognition systems due to difficulty with the conventional keyboard and mouse interface: others will use it for perceived efficiency or simply novelty. Regardless of the reason for use of this technology, the voice demands associated with extended or frequent use can be high, placing the user at risk for vocal difficulties. This paper reviews the case of an individual referred to our multidisciplinary voice care program for evaluation and treatment of vocal difficulties that began secondary to utilization of speech recognition software. We discuss medical and vocal histories, examination findings, treatment, and treatment outcomes.     

Development of a high-precision image-processing automatic measurement system for MRI visceral fat images acquired using a binomial RF-excitation pulse

Development of a rapid and accurate method for visceral fat measurement is an important task, given the recent increase in the number of patients with metabolic syndrome. In this study, we optimized the Fast Low Angle Shot (FLASH) sequence using a binominal radiofrequency excitation pulse, in which the acquisition time is short, and measured changes in the amount of visceral fat in subjects after a period of wearing clothes with a fat-reducing effect during walking. We solved the reproducibility problem associated with the number of slices, and developed automatic measurement software for high-precision separation and extraction of abdominal visceral fat images. This software was developed using intensity correction with the coil position, derivation of a threshold by histogram analysis and fat separation by template matching for abdominal images. The cross-sectional area of a single slice varies for every acquisition due to visceral organ movement, but the relative error largely converged for seven slices. The measured amount of abdominal fat tended to be consistent with changes in the body fat and waist circumference of the subjects. The correlation coefficients between automatic extraction using the measurement software and manual extraction were 0.9978 for subcutaneous fat and 0.9972 for visceral fat, showing very strong positive correlations. The consistency rates were 0.9502±0.0167 for subcutaneous fat and 0.9395±0.0147 for visceral fat, and the shapes of the regions were also extracted very accurately. These results show that the magnetic resonance imaging acquisition method and image processing system developed in this study are beneficial for measurement of abdominal visceral fat. Therefore, this method may have a major role in future diagnosis of metabolic syndrome.     

轴对称静电场的束流光学模拟与设计

为了对高压倍加器和静电加速器等低能加速器中一些具有特殊结构的轴对称静电元件进行模拟和设计,采用传输矩阵法编写了直流束的束流光学计算程序,并利用该程序对高频离子源预聚焦系统和移动式加速器中子源的束流光学系统进行了模拟和设计。程序将整个轴对称静电场区域看作厚透镜,并均分成若干个小区间,先利用其他电磁场软件计算区域内的轴上电势分布,然后根据该电势分布计算每个小区间内的束流传输情况得到束流的包络曲线。该程序可以用于计算非线性效应可忽略的复杂轴对称静电场中强流和弱流束的传输,且所需计算时间很短。     

Line narrowing effect on the retrieval of HF and HCl vertical profiles from ground-based FTIR measurements

Collision-induced line narrowing, which has been discovered in the 1950s and investigated thoroughly in the laboratory since then, has yet never been taken into account in the spectroscopic remote sensing of the atmosphere. This work investigates the effect of collision-induced line narrowing onto the retrieval of HCl and HF vertical profiles from ground-based solar absorption FTIR measurements made at the NDSC station of the Jungfraujoch (46.5^°N, 8^°E and 3580 m above see level). The retrievals are performed with the Atmosphit software, recently developed at the Université Libre de Bruxelles. It is presented in this paper for the first time and is validated against the widely used SFIT2 software. The impact of the line narrowing onto the retrieval of HCl and HF vertical profiles is examined relying on careful information content and error budget analyses. We report that the effect is relatively weak for HCl but significant for HF. Confirmation of the need to take the line narrowing into account for the retrieval of vertical profiles from ground-based FTIR spectra is given by comparison with data from the HALOE space borne instrument, rather insensitive to this spectroscopic effect.     

Development of Matlab filtering techniques in digital speckle pattern interferometry

In interferometric fringe pattern analysis, specular and speckle fringe patterns are the two main divisions. While specular fringes are characterized by quality fringes, speckle (that obtains due to the diffuse scattering of the coherent radiation from an optically rough surface) fringe patterns are characterized by noisy fringes. This paper concentrates on this aspect and the Matlab based filtering methods to improve the quality of speckle fringe patterns by developing the appropriate software. Further, the newly developed software “Macurv” will be presented which can give the second order derivative (curvature) fringe information. A software with several functions is written using Matlab. The objective of the software is to provide a more effective way for the post-processing of speckle interferometric fringes. The algorithm and functions of the developed software “Macurv” will be explained.     

软件化脉冲序列程序器

在核磁共振谱仪中, 射频发射通道、接收机以及数据采集等的实时控制是由“脉冲序列器 ”来完成的. 本文提出了一套可设计任意脉冲序列、由全软件构成的“脉冲序列程序器”,该软件用Delphi 5 实现,用户界面简洁直观. 由其产生的脉冲的最小脉宽为1.3 μs,分辨率为12 ns（CPU工作在333 MHz）.     

Measurements of the diffusion coefficient of nanoparticles by selective plane illumination microscopy

A laser-based selective plane illumination microscope is developed for the visualization of polystyrene nanospheres about 100 nm in diameter in water at a distance more than 600 μm from microcell walls. The contrast and brightness of particle images are high enough to record them by a video camera with a frame rate of up to 60 frames per second without using an image intensifier. The diffusion coefficients of monodisperse polystyrene nanospheres obtained using this microscope and the image processing software developed by the authors are presented. The measured diffusion coefficients provide the possibility to determine nanosphere diameters with a relative error not exceeding 5%.     

Consistent histories and operational quantum theory

In this work a generalization of the consistent histories approach to quantum mechanics is presented. We first critically review the consistent histories approach to nonrelativistic quantum mechanics in a mathematically rigorous way and give some general comments about it. We investigate to what extent the consistent histories scheme is compatible with the results of the operational formulation of quantum mechanics. According to the operational approach, nonrelativistic quantum mechanics is most generally formulated in terms of effects, states, and operations. We formulate a generalized consistent histories theory using the concepts and the terminology which have proven useful in the operational formulation of quantum mechanics. The logical rule of the logical interpretation of quantum mechanics is generalized to the present context. The algebraic structure of the generalized theory is studied in detail.     

自制微成像系统的Spiral快速成像实现

自制了一种核磁共振微成像系统,本系统只需4根通用的I/O并行口线,就可以利用常规的NMR谱仪进行核磁共振微成像实验. 文中给出了相关的控制软件、螺旋（Spiral）快速成像相关软件以及实现过程,最后给出实验结果.     

Analysis of digital recordings of noise levels using a programmable calculator

The system used at the Building Research Station for analysing digital recordings of noise levels is described. A suite of programs has been developed which analyses the noise recordings and gives values of selected noise units. Time histories of the noise may be plotted using some of the programs.     

Indirect measurement of dynamic force transmitted by a nonlinear hydraulic mount under sinusoidal excitation with focus on super-harmonics

Direct measurement of forces is not practical in many real-life applications since the interfacial conditions may change. Thus indirect force estimation methods must be developed though they pose special difficulty for nonlinear mounts or isolators. The hydraulic engine mount is examined as an illustrative example in this article since it exhibits spectrally varying and amplitude-sensitive parameters. First, we propose linear time-invariant, nonlinear and quasi-linear fluid and mechanical system models. Second, models are utilized to predict the transmitted force time history under sinusoidal excitation conditions given measured (or calculated) motion and/or internal pressure time histories. Experimental data from the non-resonant dynamic stiffness test is investigated in both time and frequency domains. In particular, the super-harmonic contents in fluid chamber pressure and force time histories are investigated using both measurements and mathematical models. This paper examines several alternate indirect schemes for estimating dynamic forces and highlights their strengths. The quasi-linear model with effective system parameters, say in terms of force to pressure or force to motion transfer functions, is found to correlate well with measured dynamic forces though linear and nonlinear models could be employed as well.     

对称相位函数掩模化的研究

本文对各种连续对称相位函数及其特性进行了分析,讨论了相位函数的2π调制、2^N和N-1法量化等问题及数据处理过程,提出二元衍射元件CIF(Caltech Intermediate Form)格式掩模数据的生成方法,并建立了实用软件,为激光直写技术实现二元衍射光学元件制作提供了有效的手段.     

Jet Impingement Cooling of a Hot Moving Steel Plate: An Experimental Study

In the current study, a hot moving steel plate of 6 mm thickness with an initial temperature of 900°C has been considered for jet impingement cooling. The experiment has been designed with the help of Design of Expert software to optimize the process parameters based on the highest cooling rate. The various subsurface transient temperature histories have been measured during the cooling process. The surface heat flux and surface temperature were calculated with the help of a commercial inverse heat transfer solver called INTEMP. The experimental result has been presented in terms of cooling rate and critical heat flux.