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11.
Chris P. Pantelides Justin Nadauld Larry Cercone 《Canadian Metallurgical Quarterly》2003,7(2):118-126
Transportation departments have been using aluminum overhead sign structures since the 1950s. It is well documented that cracks develop in the welds between diagonal and chord members due to fatigue stresses from wind-induced vibration of the slender members. The cracks propagate to complete failure of the members, which can cause collapse of the truss and inflict injuries. The original design of overhead sign structures did not consider fatigue as a limit state. In addition, field welding of aluminum structures for any possible repairs is prohibited. A repair method for the cracked aluminum welded connections between diagonals and chord members using glass fiber reinforced polymer composites (GFRPs) is proposed. The static load carrying capacity of the welded connection, and the cracked connection repaired with GFRP composites are established. The paper describes the surface preparation of the aluminum tubular members, and the architecture and application sequence of the GFRP composite to retrofit the connection. Experimental results are presented from static tests of welded aluminum connections, welded aluminum connections retrofitted with GFRP composites, and new aluminum connections that depend only on GFRP composite elements for their strength. The results from monotonic static tests carried out on cracked welded specimens from actual sign structures show that the retrofitted connection with GFRP reinforcement achieved 1.17 to 1.25 times the capacity of the welded aluminum connection without any visible cracks. This result, and the minimal traffic disruption anticipated in the actual field application, makes this retrofit method a good candidate for implementation. 相似文献
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10月19日,历经5年的等待,姗姗来迟的InternetExplorer7正式版终于出现在世人面前。有别于以往渐近式的改进,本次的IE7不管是外观,还是内涵,都发生了翻天覆地的变化。不过,资源占用情况依然不容乐观,本文将带你了解这一切。 相似文献
14.
A Weibull process/non-homogeneous Poisson process is commonly used to analyze the failure behavior of repairable systems. The object of the present study is to obtain exact estimates of the failure intensity of this model at the time of n failures. The resulting MLE estimate is biased and the corrected version for biasedness along with some approximate estimates is given. An analytical and numerical comparison of the relative efficiencies of the MLE of the exact biased, approximated biased, exact unbiased and approximated unbiased of the intensity function is presented. It will be shown that for small n (n < 30) there is quite a large relative difference between the mean squared errors of the exact and approximate estimates of the intensity function. Real failure data are used to illustrate the difference between the exact and approximate estimates of the intensity function. 相似文献
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Bradley Brendan P.; Gossop Michael; Brewin Chris R.; Phillips Grania; Green Lynette 《Canadian Metallurgical Quarterly》1992,60(3):470
Investigated whether attributions of opiate addicts would predict both their ability to abstain from future use and their reactions to abstinence violations. Measures of generalized beliefs about responsibility for positive and negative outcomes and specific attributions about relapse episodes were elicited from 80 addicts at the time of admission for inpatient detoxification and treatment. Addicts who at admission attributed to themselves greater responsibility for negative outcomes and who attributed relapse episodes to more personally controllable factors were subsequently (at 6-mo follow-up) more likely either to be completely abstinent or to contain the effects of temporary lapses into opiate use. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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Optical scattering in beef steak to predict tenderness using hyperspectral imaging in the VIS-NIR region 总被引:1,自引:0,他引:1
Kim Cluff Govindarajan Konda Naganathan Jeyamkondan Subbiah Renfu Lu Chris R. Calkins Ashok Samal 《Sensing and Instrumentation for Food Quality and Safety》2008,2(3):189-196
The objective of this research is to develop a non-destructive method for predicting cooked beef tenderness using optical
scattering of light on fresh beef muscle tissue. A hyperspectral imaging system (λ = 496–1,036 nm) that consists of a CCD
camera and an imaging spectrograph, was used to acquire beef steak images. The hyperspectral image consisted of 120 bands
with spectral intervals of 4.54 nm. Sixty-one fresh beef steaks, including 44 strip loin and 17 tenderloin cuts, were collected.
After imaging, the steaks were cooked and Warner-Bratzler shear (WBS) force values were collected as tenderness references.
The optical scattering profiles were derived from the hyperspectral images and fitted to the modified Lorentzian function.
Parameters, such as the peak height, full scattering width at half maximum (FWHM), and the slope around the FWHM were determined
at each wavelength. Stepwise regression was used to identify 7 key wavelengths and parameters. The parameters were then used
to predict the WBS scores. The model was able to predict WBS scores with an R = 0.67. Optical scattering implemented with hyperspectral imaging shows limited success for predicting current status of tenderness
in beef steak. 相似文献
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日益精密且成本逐渐下降的的显示技术使人们对下一代户内、户外广告的"数字化"充满了期待。然而运行显示网络必不可少的"大脑"是不容忽略的。下面综述了成功的数字广告系统的软件需求,以及这些系统的工作方式。 相似文献
20.
Environmentally responsive hydrogels have become attractive research subjects for many applications. In this work, a series of pH‐sensitive and color‐changing nanoparticles (nanogels) with core–shell structures were synthesized. The cores were blue latex particles synthesized by a miniemulsion technique with styrene and methacrylic acid as monomers and Neozapon Blue 807 as a dye. The shell was a pH‐sensitive polymer that was precipitation‐polymerized onto the core from 2‐(diethylamino) ethyl methacrylate with N,N′‐methylenebisacrylamide, poly(propylene glycol) diacrylate, and divinylbenzene as crosslinking agents. In the resultant latexes, the color was observed to change from deep blue to pale blue as the pH of the system was changed from a high of 10 to a low of 3. The synthesized latexes and particles (gels) were then characterized with an ultraviolet–visible spectrometer, dynamic light scattering, Fourier transform infrared, and nuclear magnetic resonance. Atomic force microscopy was also used to investigate the different morphologies of the particles after the synthesized latexes were dried at different pH values. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献