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51.
Bakeman Roger; McArthur Duncan; Quera Vincen?; Robinson Byron F. 《Canadian Metallurgical Quarterly》1997,2(4):357
On the basis of recent work by W. Gardner (1995), implications of fallible observers for observational research are discussed. Analysis shows that for identically fallible observers, values for kappa are lower when codes are few and their simple probabilities variable than when codes are many and roughly equiprobable; thus no one value of kappa can be regarded as universally acceptable. Additional analysis shows that fallible measurement degrades indices of sequential pattern more when codes are few and their simple probabilities variable. Finally, a simulation study establishes likely values for intraclass correlation reliabilities for sequential indices generated by various circumstances and suggests principled ways to select both lengths of sequences and acceptable levels of kappa for observational studies. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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Selection bias can be the most important threat to internal validity in intervention research, but is often insufficiently recognized and controlled. The bias is illustrated in research on parental interventions (punishment, homework assistance); medical interventions (hospitalization); and psychological interventions for suicide risk, sex offending, and juvenile delinquency. The intervention selection bias is most adequately controlled in randomized studies or strong quasi-experimental designs, although recent statistical innovations can enhance weaker designs. The most important points are to increase awareness of the intervention selection bias and to systematically evaluate plausible alternative explanations of data before making causal conclusions. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
54.
Raul Jimenez Zambrano Francisco A. Rubinelli Wim M. Arnoldbik Jatindra K. Rath Ruud E. I. Schropp 《Solar Energy Materials & Solar Cells》2004,81(1):73-86
A new band gap profile (exponential profile) for the active layer of the a-SiGe:H single junction cell has been designed and experimentally demonstrated. By computer simulations we show how bending the grading of the band gap in the i-layer contributes to the enhancement of the carrier collection, improving the fill factor and efficiency. The differences observed between experiments and simulations are studied using Rutherford Backscattering Spectrometry (RBS). The results highlight weak points during the deposition process, whose control enables us to bring together experimental and computational results. 相似文献
55.
Experimental Investigations of Response of Suction Caissons to Transient Vertical Loading 总被引:1,自引:0,他引:1
Suction caissons are a relatively new design being considered for use as foundations in a wide variety of offshore applications. They are unusual in that, in contrast with the development of offshore piling, there is no onshore experience that can be used as the basis for the development of designs. It is therefore essential to identify key behavioral patterns and mechanisms that govern capacity under a wide variety of loading regimes, particularly those derived from the cyclic wave loading. The object here is to establish a broad framework of response. More detailed work specific to a site or project would be required for detailed design. This paper describes experimental investigations into the vertical loading response of a suction caisson foundation. The experiments are carried out on the laboratory floor using a sophisticated three-degree-of-freedom loading rig. The caissons are embedded in sand saturated with viscous silicon oil so that modeled drainage times are representative of typical offshore conditions. The experiments involve cyclic loading about different mean loads, including cycling into tension and monotonic loading at different rates. The relationship between the cyclic loading and monotonic loading is explored. One of the key conclusions from the results is that serviceability requirements will dictate design rather than capacity. Perhaps surprisingly, for the experiments undertaken, the rate of loading had little effect on the response. 相似文献
56.
Amplification of picosecond pulses from an actively mode-locked semiconductor diode laser in an erbium-doped fibre amplifier pumped at 532 nm is demonstrated. Peak emission was centred on 1.536 mu m and a saturated amplifier gain of 13 dB yielded less than 10 ps pulses with a peak power of 0.58 W at 600 MHz. Optimisation of the mode-locked oscillator allowed amplified peak pulse powers greater than 3 W to be generated.<> 相似文献
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58.
Technology and Roles: A Tale of Two TVs 总被引:2,自引:0,他引:2
59.
O Byron 《Canadian Metallurgical Quarterly》1997,72(1):408-415
Computer software such as HYDRO, based upon a comprehensive body of theoretical work, permits the hydrodynamic modeling of macromolecules in solution, which are represented to the computer interface as an assembly of spheres. The uniqueness of any satisfactory resultant model is optimized by incorporating into the modeling procedure the maximal possible number of criteria to which the bead model must conform. An algorithm (AtoB, for atoms to beads) that permits the direct construction of bead models from high resolution x-ray crystallographic or nuclear magnetic resonance data has now been formulated and tested. Models so generated then act as informed starting estimates for the subsequent iterative modeling procedure, thereby hastening the convergence to reasonable representations of solution conformation. Successful application of this algorithm to several proteins shows that predictions of hydrodynamic parameters, including those concerning solvation, can be confirmed. 相似文献
60.
Electroflotation studies on sphalerite fine particles, conducted under careful pH control using buffer electrolytes, reveal that for either H2 or 02 electrolytic gases there exists an optimum pH range at which electroflotation is most effective. This can be explained by the observed dependence of electrolytic gas bubble size on the pH of the electrolyte. 相似文献