铠装热电偶两种校准方法的比较

通过JJG 351-1996与JJF 1262-2010两种方法对8支铠装K型热电偶进行测试,分析得出后者方法的复现性更佳,不确定度更小,更符合铠装廉金属热电偶的固有特性。     

Assessment of manual assembly complexity: a theoretical and empirical comparison of two methods

There are several theoretical methods for assessment of assembly complexity but there are few practically applicable methods. One of the methods, CompleXity Index (CXI), aims at assessing operators’ perception of manual assembly complexity in running production. Another recently developed method, Basic Assembly Complexity (CXB) is intended for predictive assessment of basic manual assembly complexity in early product and production development. Both CXI and CXB aim to improve assembly conditions for operators, reduce assembly-related errors and the costs for corrective measures as well as increase assembly quality although in different ways and at different organisational levels and life cycle stages. The purpose of this study was to compare the two methods to obtain feedback and learn from operators experience in order to develop better predictive assessment criteria. The method comparison showed that about 50% of the CXB assessment approaches were similar to CXI but other covered different aspects. In comparison of the complexity values of the methods no significant results were obtained. However, some CXI issues that were not taken into account in CXB should be considered. CXB and CXI could be used in conjunction but further assessment criteria are probably needed.     

Theoretical comparison of two loading methods in fiber pull-out tests

The loading fixture influences the fiber pull-out stress in fiber-reinforced composites. Single fiber pull-out tests can be performed either by fixing the bottom surface or by restraining the top surface of the specimen. Theoretical analyses show that in comparison with the fixed-bottom tests, the restrained-top test method results in a lower stress being required for fiber pull-out. However, the difference in full-out stresses between these two test methods decreases with the increasing ratio of the radius of the matrix to that of the fiber. When this ratio is sufficiently large, the difference in pull-out stresses due to different loading methods can be ignored.     

Numerical comparison of two meshfree methods for acoustic wave scattering

Density results using an infinite number of acoustic waves allow us to derive meshless methods for solving the homogeneous and the inhomogeneous Helmholtz equation. In this paper we consider the numerical simulation of acoustic scattering problems in a bounded domain using the plane waves method and the method of fundamental solutions. We establish a link between the two methods, namely the plane waves method may be seen as the asymptotic case of the method of fundamental solutions for distant source points. Several numerical tests comparing these methods are presented.     

A comparison of two methods of analysing staircase fatigue test data

When the fatigue strength of components or material is tested by the staircase or up‐and‐down method, the data can be analysed in either the fatigue strength domain, which is the most popular approach, or the life domain, based on life regression models. In this paper we exploit a simple relationship between families of models in the two domains to obtain an estimate of the distribution of fatigue strength directly from a fitted life regression model. We use simulation to compare the two approaches, concluding that for estimating important features of the fatigue strength distribution the method of maximum likelihood is more effective if it is applied in the life domain. In particular, it is more robust to the choice of x_h, the step height of the staircase, provided x_h is in the range σ_X–2σ_X, where σ_X is the standard deviation of the log‐strengths. Most of our results are insensitive to the value of the initial stress amplitude. Copyright © 2007 John Wiley & Sons, Ltd.     

两类声速测温方法的研究与比较

声学测温是一种先进的温度测量方法，与传统方法相比，具有很多优势。而在声学测温的各种方法中，基于声波传播时间的声速测温方法又是一种比较好的、应用更广泛的方法。本文着重对气体介质中声速测温的两类测量方法进行了研究和比较，分析了其各自的优势与不足。结果表明，直接传播测量方法是一种更有潜力、应用更广泛的测温方法。     

Spin filters and supermirrors: a comparison study of two methods of high-precision neutron polarisation analysis

The precise knowledge of the neutron polarisation is needed in tests of the electroweak Standard Model using angular correlations in polarised neutron beta decay. We performed an experimental comparison study of two different methods of polarisation analysis of a cold neutron beam which are based on spin-dependent reflection, respectively, transmission. The compared devices are a supermirror analyser used in prior neutron decay studies and an opaque transmission spin filter of either polarised ³He or polarised protons. The results of the neutron polarisation measured with the supermirror analyser and with the spin filter coincided in three different experiments within 0.1–0.2%.     

A comparison of two bibliometric methods for mapping of the research front

Summary This paper builds on previous research concerned with the classification and specialty mapping of research fields. Two methods are put to test in order to decide if significant differences as to mapping results of the research front of a science field occur when compared. The first method was based on document co-citation analysis where papers citing co-citation clusters were assumed to reflect the research front. The second method was bibliographic coupling where likewise citing papers were assumed to reflect the research front. The application of these methods resulted in two different types of aggregations of papers: (1) groups of papers citing clusters of co-cited works and (2) clusters of bibliographically coupled papers. The comparision of the two methods as to mapping results was pursued by matching word profiles of groups of papers citing a particular co-citation cluster with word profiles of clusters of bibliographically coupled papers. Findings suggested that the research front was portrayed in two considerably different ways by the methods applied. It was concluded that the results in this study would support a further comparative study of these methods on a more detailed and qualitative ground. The original data set encompassed 73,379 articles from the fifty most cited environmental science journals listed in Journal Citation Report, science edition downloaded from the Science Citation Index on CD-ROM.     

Experimental comparison of two methods for the measurement of long gauge blocks

A comparison of two methods of measurement of long gauge blocks is performed. It is shown that the relative divergence of the measurement results obtained by a method involving counting of the interference bands between the centers of gravity of the achromatic bands and a method involving matching fractional parts of the orders of interference amounts to less than 10⁻⁸. __________ Translated from Izmeritel’naya Tekhnika, No. 7, pp. 20–23, July, 2007.     

A comparison of two methods for calculating solid angle coefficients in a BIEM numerical wave tank

By taking the simulation of nonlinear numerical wave tank using the boundary integral equation method (BIEM) as an example, direct and indirect methods are used to compute solid angle coefficients (also named as free-term coefficients). The computing precision and cost are compared between these two methods. The comparisons show that the same good numerical results can be obtained for both direct and indirect methods, and the computing cost of the indirect method is greater than that of the direct method, especially for larger calculation domain.     

Particle-sizing methods: a stationary-phase-based comparison

Stationary-phase approximation is used to examine and compare the reliability and interpretability of two main methods of particle sizing. The first method, differential light scattering, regards spherical objects having different refractive indices. Theoretical expressions are obtained, enabling the derivation of optical and geometrical properties of the object from its scattering pattern. The second method, automated microscope imaging, is considered with theoretical implications for the finite aperture of the objective lens. It is shown that, besides the well known Rayleigh resolution limit, finite aperture must affect size measurement due to optical properties of the particles. Simulation and experimental results for both differential light scattering and microscope imaging of polystyrene beads are in good agreement with theory.     

两种旁路二极管结温测试方法的分析与比较

搭建了旁路二极管结温测试的两个测试平台,一个是稳态法测试平台,一个是瞬态法测试平台,并在两个平台上进行了多次试验。结果表明,旁路二极管结温测试具有较高的测试不确定性。相对而言,稳态法重复性和稳定性比较高。在保证热阻RTHjc值可靠的情况下,建议采用稳态法进行结温测试。     

A comparison of two methods for estimating the effect of a countermeasure in the presence of regression effects

The report studies the problem of estimating in a non-experimental before-and-after investigation the effect of a countermeasure on the number of traffic accidents at road junctions. The accidents are assumed to occur according to a Poisson process with different intensities at different junctions. The junctions studied in this investigation are assumed to have been selected with the blackspot-technique, i.e. junctions with high numbers of accidents during the before-period have been chosen for the investigation. In the mathematical model this has the consequence that the number of accidents occurring during the before-period at a selected junction has a truncated Poisson distribution. During the after-period the number of accidents has a Poisson distribution (without restrictions), so that the number of accidents on the average decreases between the periods even if the countermeasure has no effect. The magnitude of this regression effect is studied in the report. The observed numbers of accidents during the before and after period are used to estimate the pure effect of the countermeasure both with an intuitive method and with the maximum likelihood method. The characteristics of the two methods of estimation are illustrated with the aid of simulation studies. In general the maximum likelihood method appears preferable, mainly because it produces estimates with higher precision.     

Automated peak interpretation in low resolution SIMS spectra; a comparison of two algorithms

Low mass resolution secondary ion mass spectra from solid samples frequently exhibit multiple line interferences at integer mass numbers due to extensive clustering and molecule formation between constituent sample atoms. Two computer algorithms are described which try to address the problem of spectrum interpretation, i.e. the assignment of isotopic and molecular ion species (and their total specific ion currents) to the peaks observed in the mass spectrum. The algorithms are applied to a positive SIMS spectrum, a negative SIMS spectrum and a mass spectrum emitted from a liquid metal ion source; interpreted results are compared.     

Quantitative comparison of tympanic membrane displacements using two optical methods to recover the optical phase

The study and quantification of the tympanic membrane (TM) displacements add important information to advance the knowledge about the hearing process. A comparative statistical analysis between two commonly used demodulation methods employed to recover the optical phase in digital holographic interferometry, namely the fast Fourier transform and phase-shifting interferometry, is presented as applied to study thin tissues such as the TM. The resulting experimental TM surface displacement data are used to contrast both methods through the analysis of variance and F tests. Data are gathered when the TMs are excited with continuous sound stimuli at levels 86, 89 and 93 dB SPL for the frequencies of 800, 1300 and 2500 Hz under the same experimental conditions. The statistical analysis shows repeatability in z-direction displacements with a standard deviation of 0.086, 0.098 and 0.080 μm using the Fourier method, and 0.080, 0.104 and 0.055 μm with the phase-shifting method at a 95% confidence level for all frequencies. The precision and accuracy are evaluated by means of the coefficient of variation; the results with the Fourier method are 0.06143, 0.06125, 0.06154 and 0.06154, 0.06118, 0.06111 with phase-shifting. The relative error between both methods is 7.143, 6.250 and 30.769%. On comparing the measured displacements, the results indicate that there is no statistically significant difference between both methods for frequencies at 800 and 1300 Hz; however, errors and other statistics increase at 2500 Hz.     

Assessment and comparison of surface chemical composition and oxide layer modification upon two different activation methods on a cocrmo alloy

This study investigated the effect of two different activation methods on the surface chemical composition of a CoCrMo-alloy. The activation was performed with oxygen plasma (OP) or nitric acid (NA). The surface physical–chemical properties were thoroughly characterized by means of several analytical techniques: X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), zinc-complex substitution technique, contact angle, and interferometry. The surface modification was evaluated by assessing contamination removal, the “active” hydroxyl groups (OH-act) present at the surface, the metal oxide ratio (Co_yO _x ^? /Cr_yO _x ^? ) and changes in the chemical composition and topography of the oxide layer. XPS experimental data showed for both methods (OP and NA) a significant decrease of the carbon contents (C 1s) associated with contaminants and at the same time changes in the atomic composition of the oxide layer (O 1s). In addition, the O 1s XPS spectra showed differences between the percentage of OH^? before and after OP or NA treatment, leading to the conclusion that both methods are effective for surface “cleaning” and activation. These results were further investigated and corroborated by ToF-SIMS analysis and zinc complex substitution technique. The general conclusion was that NA is more efficient in terms of contaminants removal and generation of accessible OH-act present at the surface and without altering the native metal oxide ratio (Co_yO _x ^? /Cr_yO _x ^? ) considered to be essential for biocompatibility.     

Fatigue damage repair: a comparison of some possible methods

When a fatigue crack is discovered in an engineering component, some expeditious temporary repair may be needed before more thorough treatment is available. Conventional repair methods, such as grinding removal of the crack and stop drilling, are often employed. In this work, the method of drilling crack-flank holes near to but not at the crack tip has been studied. It was found that retardation still occurred. Moreover, if the holes were drilled a small distance ahead of the tip, the crack was likely to grow into the hole, achieving a considerable amount of life extension. The effects of inducing artificial crack closure by infiltrating epoxy resin, alumina powder and a mixture of both have also been investigated. These were compared with the effect of overload-induced retardation. In all the methods studied, different degrees of crack growth retardation have been achieved, and they have the potential to be developed into practical fatigue crack repair methods.     

A comparison of modelling methods for polydispersed wet‐steam flow

Spontaneous nucleation of water droplets in moist air or steam may result in droplet spectra which are complex in shape and which span a broad range of sizes. This is particularly true if the flow is transonic or supersonic with shock waves present, or if an already droplet‐laden flow re‐expands to give secondary or tertiary nucleations. Computation of such flows requires careful modelling of the size distributions if two‐phase behaviour is to be accurately predicted. In this paper, three methods are presented for treating size distributions and growth of the liquid phase in condensing steam: a mixed Eulerian–Lagrangian method, a fully Eulerian method, and a method based on moments of the droplet spectra. These are compared by computing condensing flow within a one‐dimensional supersonic nozzle under conditions that yield very different types of size spectra. Copyright © 2003 John Wiley & Sons, Ltd.