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51.
M. O. Pekguleryuz H. Kaplan R. Neelameggham J. Hryn E. Nyberg B. Powell G. Cole J. F. Nie 《JOM Journal of the Minerals, Metals and Materials Society》2002,54(8):18-21
Conclusion It is expected that the research in high-temperature alloy development will reach a critical mass in about five years. This
will not only raise the materials science of magnesium to a higher level but will also increase the confidence of the industry
in magnesium as a structural performance material. Currently, applications are being actively pursued in United States Council
for Automotive Research power train programs and European Council for Automotive R&D engine block programs to develop the
technology for elevated-temperature magnesium. More research is still needed in this interesting materials field. 相似文献
52.
This research, funded by the British National Bibliography Research Fund, examined how publishers’ websites are causing changes in relations in the book industry in order to gain further understanding of the implications of the impact of the Internet on the publishing chain. The paper is set within the context of the development of electronic commerce and how business to consumer commerce is now being overtaken by the activity in business to business trading. Publishers have followed the main business trends in using their websites to develop relationships directly with the consumer, but have been rather slower in developing their business to business activity through the Internet. This study investigated what changes were taking place as a result of current publisher activity on the Web and how these changes were affecting the traditional lines of communication in the book industry. An analysis of a range of consumer publishers’ websites was carried out to see what facilities they were offering both to the general public and to business partners within the industry. Questionnaires and interviews were then conducted to establish how publishers, booksellers and wholesalers were using publishers’ websites and whether these sites were beneficial to the industry as a whole. Facilities found on the websites were examined and analysed in order to determine their usefulness and how they might be developed to aid business to business commerce. Additionally, several issues relating to online sales, changes in sales patterns and changes in working methods were discussed. Although an amount of quantitative data is included in the report, many of the issues raised relied on the perceptions and opinions of practitioners in the book trade. 相似文献
53.
Rivilis I Van Eerd D Cullen K Cole DC Irvin E Tyson J Mahood Q 《Applied ergonomics》2008,39(3):342-358
The objective of this study was to conduct a systematic review of the literature on the effectiveness of participatory ergonomic (PE) interventions for improving workers' health. The search strategy targeted six electronic databases and identified 442 potential articles. Each article was examined by pairs of reviewers for relevance (assessed a participative ergonomic workplace intervention, with at least one health outcome, published in English in peer reviewed literature). Twenty-three articles met relevance criteria and were then appraised for methodological strength. Using a best evidence synthesis approach, 12 studies that were rated as 'medium' or higher provided partial to moderate evidence that PE interventions have a positive impact on: musculoskeletal symptoms, reducing injuries and workers' compensation claims, and a reduction in lost days from work or sickness absence. However, the magnitude of the effect requires more precise definition. 相似文献
54.
Matthew O.T. Cole Author Vitae Theeraphong Wongratanaphisan Author Vitae 《Automatica》2008,44(11):2876-2883
Model-based feedback control of vibration in flexible structures can be complicated by the possibility that interaction with an external body occurs. If not accounted for, instability or poor performance may result. In this paper, a method is proposed for achieving robust vibration control of flexible structures under contact. The method uses robust linear state feedback, coupled with a state estimation scheme utilizing contact force measurement. Uncertain contact characteristics are modelled by a sector-bounded non-linear function, such that state feedback gains can be synthesized using a matrix inequality formulation of the Popov stability criterion. A separation theorem is used to establish a robust H2 cost bound for the closed loop system. Experimental results from a multi-mode flexible structure testbed confirm that vibration attenuation and stability can be maintained over a broad range of contact characteristics, in terms of compliance and clearance. 相似文献
55.
Hengfei Gu Fei Zhang Shinjae Hwang Anders B. Laursen Xin Liu So Yeon Park Mengjin Yang Rosemary C. Bramante Hussein Hijazi Leila Kasaei Leonard C. Feldman Yao-Wen Yeh Philip E. Batson Bryon W. Larson Mengjun Li Yifei Li Keenan Wyatt James L. Young Krishani Teeluck Kai Zhu Eric Garfunkel G. Charles Dismukes 《Advanced functional materials》2023,33(25):2301196
The rapidly increasing solar conversion efficiency (PCE) of hybrid organic–inorganic perovskite (HOIP) thin-film semiconductors has triggered interest in their use for direct solar-driven water splitting to produce hydrogen. However, application of these low-cost, electronic-structure-tunable HOIP tandem photoabsorbers has been hindered by the instability of the photovoltaic-catalyst-electrolyte (PV+E) interfaces. Here, photolytic water splitting is demonstrated using an integrated configuration consisting of an HOIP/n+silicon single junction photoabsorber and a platinum (Pt) thin film catalyst. An extended electrochemical (EC) lifetime in alkaline media is achieved using titanium nitride on both sides of the Si support to eliminate formation of insulating silicon oxide, and as an effective diffusion barrier to allow high-temperature annealing of the catalyst/TiO2-protected-n+silicon interface necessary to retard electrolytic corrosion. Halide composition is examined in the (FA1-xCsx)PbI3 system with a bandgap suitable for tandem operation. A fill factor of 72.5% is achieved using a Spiro-OMeTAD-hole-transport-layer (HTL)-based HOIP/n+Si solar cell, and a high photocurrent density of −15.9 mA cm−2 (at 0 V vs reversible hydrogen electrode) is attained for the HOIP/n+Si/Pt photocathode in 1 m NaOH under simulated 1-sun illumination. While this thin-film design creates stable interfaces, the intrinsic photo- and electro-degradation of the HOIP photoabsorber remains the main obstacle for future HOIP/Si tandem PEC devices. 相似文献
56.
57.
The
4
He wetting transition on a Cs surface is for the first time studied by Path Integral Monte Carlo simulation. Numerical results for a system of 64
4
He atoms are qualitatively consistent with a wetting transition at a temperature T 2 K. 相似文献
58.
Membrane extractors comprising a membrane house inside of a valve have been developed to separate compounds of interest from a sample matrix and introduce these compounds into a mass spectrometer. Experimental control over parameters that affect permeability or that may damage the membrane, such as the membrane temperature, is provided with the valve. The valve was tested for response and response times with the valve separated from the mass spectrometer by various interface tube lengths. Data for steady state response measurements showed no significant change with the valve at different distances from the ion source. Polar compounds show a strong response time dependency on the interface tube length. This adsorption phenomenon is minimized by simply heating the interface tube. Other factors affecting the performance of the device are discussed. 相似文献
59.
Solutions of numerically ill-posed least squares problems for A∈Rm×n by Tikhonov regularization are considered. For D∈Rp×n, the Tikhonov regularized least squares functional is given by where matrix W is a weighting matrix and is given. Given a priori estimates on the covariance structure of errors in the measurement data , the weighting matrix may be taken as which is the inverse covariance matrix of the mean 0 normally distributed measurement errors in . If in addition is an estimate of the mean value of , and σ is a suitable statistically-chosen value, J evaluated at its minimizer approximately follows a χ2 distribution with degrees of freedom. Using the generalized singular value decomposition of the matrix pair , σ can then be found such that the resulting J follows this χ2 distribution. But the use of an algorithm which explicitly relies on the direct solution of the problem obtained using the generalized singular value decomposition is not practical for large-scale problems. Instead an approach using the Golub-Kahan iterative bidiagonalization of the regularized problem is presented. The original algorithm is extended for cases in which is not available, but instead a set of measurement data provides an estimate of the mean value of . The sensitivity of the Newton algorithm to the number of steps used in the Golub-Kahan iterative bidiagonalization, and the relation between the size of the projected subproblem and σ are discussed. Experiments presented contrast the efficiency and robustness with other standard methods for finding the regularization parameter for a set of test problems and for the restoration of a relatively large real seismic signal. An application for image deblurring also validates the approach for large-scale problems. It is concluded that the presented approach is robust for both small and large-scale discretely ill-posed least squares problems. 相似文献
60.