Invited review article: measurement uncertainty of linear phase-stepping algorithms

Phase retrieval techniques are widely used in optics, imaging and electronics. Originating in signal theory, they were introduced to interferometry around 1970. Over the years, many robust phase-stepping techniques have been developed that minimize specific experimental influence quantities such as phase step errors or higher harmonic components of the signal. However, optimizing a technique for a specific influence quantity can compromise its performance with regard to others. We present a consistent quantitative analysis of phase measurement uncertainty for the generalized linear phase stepping algorithm with nominally equal phase stepping angles thereby reviewing and generalizing several results that have been reported in literature. All influence quantities are treated on equal footing, and correlations between them are described in a consistent way. For the special case of classical N-bucket algorithms, we present analytical formulae that describe the combined variance as a function of the phase angle values. For the general Arctan algorithms, we derive expressions for the measurement uncertainty averaged over the full 2π-range of phase angles. We also give an upper bound for the measurement uncertainty which can be expressed as being proportional to an algorithm specific factor. Tabular compilations help the reader to quickly assess the uncertainties that are involved with his or her technique.     

Invited review article: Single-photon sources and detectors

We review the current status of single-photon-source and single-photon-detector technologies operating at wavelengths from the ultraviolet to the infrared. We discuss applications of these technologies to quantum communication, a field currently driving much of the development of single-photon sources and detectors.     

Invited review article: The statistical modeling of atomic clocks and the design of time scales

I will show how the statistical models that are used to describe the performance of atomic clocks are derived from their internal design. These statistical models form the basis for time scales, which are used to define international time scales such as International Atomic Time and Coordinated Universal Time. These international time scales are realized by ensembles of clocks at national laboratories such as the National Institute of Standards and Technology, and I will describe how ensembles of atomic clocks are characterized and managed.     

Realization and dissemination of units in a revised SI

The General Conference of Weight and Measures (CGPM) with its Resolution 12 has officially prospected the adoption, possibly at the next General Conference of 2011, of new definitions for kilogram, ampere, kelvin and mole using fundamental constants as reference quantities. Thus, the outlines and features of the SI after that date are worthy to be considered and a general afterthought of the metrological activity in the new situation to be attempted.The future realisations of units will greatly benefit from the accelerated endeavour to determine the relevant fundamental constants with the minimum possible uncertainty before their values are fixed by definition. In fact, many of those experiments will become realisations of units when the new definitions are adopted.To define the units by reference to fundamental constants implies to abandon the identification of the unit with its primary standard, as in the old metrological tradition. To realise a unit will definitely consist in assigning a value to a primary standard, consistent with the fixed values of the reference constants, by means of an experimental procedure, independent of a specific definition, which could even not exist. The primary standard should be suitable to dissemination by direct comparison, thus essentially stable and accessible with the highest precision, while the role of the realisation experiment would be mainly related to indirect measurements, typical of scientific activity, which involves the coherence of the unit system. The two distinct roles, of unit realisation and primary standard, correspond to different uncertainty components, of which only one is implied in dissemination activity, just aiming at compatibility of measurements of a specific quantity. Each of the two uncertainty components has a different evolution from the time of the unit redefinition.These last considerations could validly contribute in critical issues, such as deciding whether the time for a unit redefinition has come or it should be preferable to wait for new and better experiments before fixing the value of a constant. This could be the case for the kilogram redefinition.     

Invited review article: a review of techniques for attaching micro- and nanoparticles to a probe's tip for surface force and near-field optical measurements

Cantilevers with single micro- or nanoparticle probes have been widely used for atomic force microscopy surface force measurements and apertureless scanning near-field optical microscopy applications. In this article, I critically review the particle attachment and modification techniques currently available, to help researchers choose the appropriate techniques for specific applications.     

Invited review article: accurate and fast nanopositioning with piezoelectric tube scanners: emerging trends and future challenges

Piezoelectric tube scanners have emerged as the most widely used nanopositioning technology in modern scanning probe microscopes. Despite their impressive properties, their fast and accurate operations are hindered due to complications such as scan induced mechanical vibrations, hysteresis nonlinearity, creep, and thermal drift. This paper presents an overview of emerging innovative solutions inspired from recent advances in fields such as smart structures, feedback control, and advanced estimation aimed at maximizing positioning precision and bandwidth of piezoelectric tube scanners. The paper presents a thorough survey of the related literature and contains suggestions for future research prospects.     

Invited review article: combining scanning probe microscopy with optical spectroscopy for applications in biology and materials science

This is a comprehensive review of the combination of scanning probe microscopy (SPM) with various optical spectroscopies, with a particular focus on Raman spectroscopy. Efforts to combine SPM with optical spectroscopy will be described, and the technical difficulties encountered will be examined. These efforts have so far focused mainly on the development of tip-enhanced Raman spectroscopy, a powerful technique to detect and image chemical signatures with single molecule sensitivity, which will be reviewed. Beyond tip-enhanced Raman spectroscopy and/or topography measurements, combinations of SPM with optical spectroscopy have a great potential in the characterization of structure and quantitative measurements of physical properties, such as mechanical, optical, or electrical properties, in delicate biological samples and nanomaterials. The different approaches to improve the spatial resolution, the chemical sensitivity, and the accuracy of physical properties measurements will be discussed. Applications of such combinations for the characterization of structure, defects, and physical properties in biology and materials science will be reviewed. Due to the versatility of SPM probes for the manipulation and characterization of small and/or delicate samples, this review will mainly focus on the apertureless techniques based on SPM probes.     

Invited article: Linearization and signal recovery in photoacoustic infrared spectroscopy

Photoacoustic (PA) infrared spectroscopy enables the characterization of a wide variety of materials, affording the spectroscopist several advantages over more traditional infrared methods. While PA spectra are readily acquired using commercial instrumentation, the quality of the data can be improved substantially through the use of specialized numerical and experimental procedures. Two of these methods are the subject of this review. Specifically, this article describes (a) linearization of PA infrared spectra, a calculation that incorporates phase and amplitude information to extend the range of linearity for strongly absorbing samples, and (b) lock-in and digital signal-recovery procedures in step-scan phase-modulation PA infrared spectroscopy. Linearization yields significant improvement in band definition, especially in the low-wavenumber region. This numerical method succeeds in situations where the PA phase of the sample is less than that of the reference (carbon black). When this criterion is not met initially, the sample or reference interferograms can be manipulated prior to the calculation. The steps involved in linearization are illustrated in detail and approximations are discussed. Lock-in demodulation of the step-scan phase-modulation signal is compared to digital (software) demodulation in this study; the lock-in technique is found to be superior in several cases. The imaginary interferograms in these experiments sometimes lack a strong central feature, a situation that necessitates the application of less commonly used methods for phase correction and spectrum calculation. These methods, which are available in commercial software, include two-quadrant and stored-phase corrections. The PA phase spectrum resembles amplitude and absorption spectra when real and imaginary PA spectra are correctly calculated.     

Invited review article: Photopyroelectric calorimeter for the simultaneous thermal, optical, and structural characterization of samples over phase transitions

The study of thermophysical properties is of great importance in several scientific fields. Among them, the heat capacity, for example, is related to the microscopic structure of condensed matter and plays an important role in monitoring the changes in the energy content of a system. Calorimetric techniques are thus of fundamental importance for characterizing physical systems, particularly in the vicinity of phase transitions where energy fluctuations can play an important role. In this work, the ability of the Photopyroelctric calorimetry to study the versus temperature behaviour of the specific heat and of the other thermal parameters in the vicinity of phase transitions is outlined. The working principle, the theoretical basis, the experimental configurations, and the advantages of this technique, with respect to the more conventional ones, have been described and discussed in detail. The integrations in the calorimetric setup giving the possibility to perform, simultaneously with the calorimetric studies, complementary kind of characterizations of optical, structural, and electrical properties are also described. A review of the results obtained with this technique, in all its possible configurations, for the high temperature resolution studies of the thermal parameters over several kinds of phase transitions occurring in different systems is presented and discussed.     

Advances in tribology: the materials point of view

The application of advanced materials in various areas of contemporary technology can lead to improvements in the function, quality and performance of engineering components and systems. In this paper, an overview of the developments in high performance materials, both organic and inorganic based, is given. This includes thin hard coatings because of their increasing importance in tribological improvements. For these types of materials the requirements for tribo-engineering applications are analysed. Research results from BAM concerning ceramics and ceramic composites, polymers and polymer composites as well as hard coatings illustrate the friction and wear behaviour of these materials and their potential for tribo-engineering applications.     

Electron inelastic scattering and anisotropy: The two-dimensional point of view

The measurement of the electronic structure of anisotropic materials using energy loss near edge structure (ELNES) spectroscopy is an important field of microanalysis in transmission electron microscopy. We present a novel method to study the angular dependence of electron inelastic scattering in anisotropic materials. This method has been applied to the study of 1s-->pi* and sigma* transitions on the carbon K edge in pyrolitic graphite. An excellent agreement between experimental and theoretical two-dimensional scattering patterns has been found. In particular, the need of a fully relativistic calculation of the inelastic scattering cross-section to explain the experimental results is demonstrated.     

Invited article: a [corrected] unified evaluation of iterative projection algorithms for phase retrieval

Iterative projection algorithms are successfully being used as a substitute of lenses to recombine, numerically rather than optically, light scattered by illuminated objects. Images obtained computationally allow aberration-free diffraction-limited imaging and the possibility of using radiation for which no lenses exist. The challenge of this imaging technique is transferred from the lenses to the algorithms. We evaluate these new computational "instruments" developed for the phase-retrieval problem, and discuss acceleration strategies.     

Invited article: Vector and Bragg Magneto-optical Kerr effect for the analysis of nanostructured magnetic arrays

Experimental and theoretical aspects of obtaining the magnetic information carried by laser beams diffracted from an array of micro- or nanosized magnetic objects are reviewed. We report on the fundamentals of vector magneto-optic Kerr effect (MOKE), Bragg-MOKE, and second-order effects in the Kerr signal in longitudinal Kerr geometry as well as on an experimental setup used for vector and Bragg-MOKE experiments. The vector and Bragg-MOKE technique in combination with micromagnetic simulation is a reliable tool for measuring the complete magnetization vector and for characterizing the reversal mechanism of lateral magnetic nanostructures. We discuss the Bragg-MOKE effect for three standard domain configurations during the magnetization reversal process and present the expected behavior of the magnetic hysteresis loops.     

Invited article: A materials investigation of a phase-change micro-valve for greenhouse gas collection and other potential applications

The deleterious consequences of climate change are well documented. Future climate treaties might mandate greenhouse gas (GHG) emissions measurement from signatories in order to verify compliance. The acquisition of atmospheric chemistry would benefit from low cost, small size/weight/power of microsystems. In this paper, we investigated several key materials science aspects of a phase-change microvalve (PCμV) technology with low power/size/weight/cost for ubiquitous GHG sampling. The novel design, based on phase-change material low-melting-point eutectic metal alloys (indium-bismuth, InBi and tin-lead, SnPb), could be actuated at temperatures as low as 72 °C. Valve manufacturing was based on standard thick and thin-film processes and solder technologies that are commonly used in industry, enabling low-cost, high-volume fabrication. Aging studies showed that it was feasible to batch fabricate the PCμVs and store them for future use, especially in the case of SnPb alloys. Hermetic sealing of the valve prototypes was demonstrated through helium leak testing, and Mil spec leak rates less than 1 × 10(-9) atm cm(3)/s were achieved. This confirms that the sample capture and analysis interval can be greatly expanded, easing the logistical burdens of ubiquitous GHG monitoring. Highly conservative and hypothetical CO(2) bias due to valve actuation at altitude in 1 cm(3) microsamplers would be significantly below 1.0 and 2.2 ppmv for heat-treated InBi and SnPb solders, respectively. The CO(2) bias from the PCμV scales well, as a doubling of sampler volume halved the bias. We estimated the shelf life of the SnPb PCμVs to be at least 2.8 years. These efforts will enable the development of low cost, low dead volume, small size/weight microsystems for monitoring GHGs and volatile organic compounds.     

Invited article: design techniques and noise properties of ultrastable cryogenically cooled sapphire-dielectric resonator oscillators

We review the techniques used in the design and construction of cryogenic sapphire oscillators at the University of Western Australia over the 18 year history of the project. We describe the project from its beginnings when sapphire oscillators were first developed as low-noise transducers for gravitational wave detection. Specifically, we describe the techniques that were applied to the construction of an interrogation oscillator for the PHARAO Cs atomic clock in CNES, in Toulouse France, and to the 2006 construction of four high performance oscillators for use at NMIJ and NICT, in Japan, as well as a permanent secondary frequency standard for the laboratory at UWA. Fractional-frequency fluctuations below 6 x 10(-16) at integration times between 10 and 200 s have been repeatedly achieved.     

Flexible media — recent developments from the tribology point of view

With the increase in the recording density of hard disk systems, the demand on the increase in the data recording capacity of tape drive systems as back-up systems is increasing. One of the advantages of the tape drive systems is high volumetric recording density, which is obtained by high areal recording density and thin tapes. The areal recording density can be increased by introducing high performance tapes, such as metal evaporated tapes, with superior magnetic characteristics and smooth magnetic surface to reduce the spacing loss. However, a smoother surface often produces a higher friction coefficient, which could cause tape damage by rotary heads and unstable tape runnability in the tape drives. Adoption of MR heads to tape drive systems is also effective in increasing the areal recording density. However, the wear allowance of the MR heads (shield type) is much smaller than that of the inductive heads. Thinner tapes show lower mechanical stiffness in general, which could cause damage to tape edges easily during tape transportation. In the second or later generation of tape drive systems, a thinner tape is often introduced. These thinner tapes should also have the interchangeability of the original thickness tape. New materials for a base film, such as PEN (polyethylene naphthalate) or aramid in which the elastic moduli are larger than those of PET, are required for thinner tapes. It was found that these side effects by the increase in the volumetric recording density can be improved by tribology. The tribological improvements from the drive design side is very important, as well as from the tape design side.     

The finite screw systems associated with a prismatic-revolute dyad and the screw displacement of a point

A linear representation of the finite motion of a prismatic-revolute dyad is presented. This representation shows that all screws associated with the finite displacements of the outermost body of a prismatic-revolute dyad form a screw system of the third order (a 3-system). The screw system associated with infinitesimal displacements of the outermost body of the prismatic-revolute dyad is shown to be a limiting case of the 3-system. The analytic expression of the screw system of displacement of a point of a body is also derived from the 3-system.     

从对产品质量的控制看技术标准与管理标准之间的关系

随着企业内部的改革发展和外部市场化环境的形成,企业的生产计划、产品营销都处在不断发展变革之中。为了保证产品质量的稳定,各个企业不仅制定了较高的技术标准,还通过对计划、生产、营销、成本等信息的调查,制定了许多管理标准,使管理者能更有效地对产品生产的全过程进行控制。可以说,管理标准和技术标准对产品质量的影响已经越来越引起我们的重视。下面笔者以我厂解决康明斯发动机总成零公里堵喷油嘴的问题为例,具体分析一下技术标准和管理标准对产品质量的影响。在“康明斯发动机燃油系统零部件清洁度标准”制定以前,由于在装配…