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。     

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.     

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%.     

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.     

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.     

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.     

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.     

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。     

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.     

A comparison of Crandall and Crank–Nicolson methods for solving a transient heat conduction problem

A comparison is made of the Crandall and Crank–Nicolson methods applied to a transient heat conduction problem with a convective boundary layer on its surface for a range of values of Nusselt modulus and Fourier modulus. A new equation is derived to handle the convective boundary condition. For reasonable accuracy requirements the Crank–Nicolson method gives superior performance with respect to accuracy.     

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 skyshine computational methods

A variety of methods employing radiation transport and point-kernel codes have been used to model two skyshine problems. The first problem is a 1 MeV point source of photons on the surface of the earth inside a 2 m tall and 1 m radius silo having black walls. The skyshine radiation downfield from the point source was estimated with and without a 30-cm-thick concrete lid on the silo. The second benchmark problem is to estimate the skyshine radiation downfield from 12 cylindrical canisters emplaced in a low-level radioactive waste trench. The canisters are filled with ion-exchange resin with a representative radionuclide loading, largely 60Co, 134Cs and 137Cs. The solution methods include use of the MCNP code to solve the problem by directly employing variance reduction techniques, the single-scatter point kernel code GGG-GP, the QADMOD-GP point kernel code, the COHORT Monte Carlo code, the NAC International version of the SKYSHINE-III code, the KSU hybrid method and the associated KSU skyshine codes.     

Evaluation and comparison of a moist granulation technique to conventional methods

In the moist granulation technique (MGT), a minimum amount of liquid is used to activate a binder in a planetary mixer. Then, any excess moisture is absorbed by the addition of a moisture-absorbing substance. In the experiments described below, acetaminophen (APAP) was the model drug; polyvinylpyrrolidone (PVP) and microcrystalline cellulose (MCC) served as the binder and moisture-absorbing material, respectively. Water was used as the granulating fluid. Comparison of the MGT with direct compression (DC) and wet granulation (WG) methods was accomplished by sieve analysis (particle size) and density measurements. Moist granulation yielded an increase in particle size compared to direct compression; these results are comparable to those from the traditional wet granulation after drying and screening. Based only on the particle size, moist granulation appears comparable to conventional wet granulation for this formula. The moist granulation technique appears to have potential for the development of controlled-release formulations.     

Optimization methods for advanced design of aircraft panels: a comparison

Advanced nonlinear analyses developed for estimating structural responses for recent applications for the aerospace industry lead to expensive computational times. However optimization procedures are necessary to quickly provide optimal designs. Several possible optimization methods are available in the literature, based on either local or global approximations, which may or may not include sensitivities (gradient computations), and which may or may not be able to resort to parallelism facilities. In this paper Sequential Convex Programming (SCP), Derivative Free Optimization techniques (DFO), Surrogate Based Optimization (SBO) and Genetic Algorithm (GA) approaches are compared in the design of stiffened aircraft panels with respect to local and global instabilities (buckling and collapse). The computations are carried out with software developed for the European aeronautical industry. The specificities of each optimization method, the results obtained, computational time considerations and their adequacy to the studied problems are discussed.