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81.
徐创文 《郑州轻工业学院学报(自然科学版)》1998,13(2):10-13
介绍了一种用于发电机组、电机等设备在线故障检测和保护报警的控制系统.该系统采用以8098单片机为核心的控制器件及其外围电路,通过对电压、电流采样并对检测到的参数进行处理,实现了自动检测、故障自诊断、保护报警以及在线设置参数等功能.它可以降低成本,减少组装和调试工作,缩小控制屏体积,减少内部构件,效益明显. 相似文献
82.
83.
Li Fucai He Zhengjia Zi Yanyang School of Mechanical Engineering Xi''''an Jiaotong University Xi''''an P. R. China 《国际设备工程与管理》2000,(4)
1IntroductionThemachineryinfactoryisalwaysthekeyequipment,soOn-lineConditionMonitoringandDiagnosticSystemCMDS)isveryimportant.Usingthissy000000stem,engineerscanknowtherunningconditionclearlyandanalyzethepossiblefaultswhenthesemachinesetscannotrunnormally.Computerscience,numericsignalprocessing,sensorandnetworktechnologyarethekeytechnologiesofnetworkbaseddistributedon-lineCMDS,anddevelopmentofthesetechnologiesmakeCMDSplayamoreimportantroleinindustry.NetworkstructureandfunctionofCMDSare… 相似文献
84.
Evaluation of the Metricheck device and the gloved hand for the diagnosis of clinical endometritis in dairy cows 总被引:2,自引:0,他引:2
S. Pleticha 《Journal of dairy science》2009,92(11):5429-5435
The objective of this study was to compare 2 surrogate vaginal examination methods (i.e., gloved hand and a vaginal device) with vaginoscopy as a reference method for diagnosing clinical endometritis in dairy cows. Holstein-Friesian cows (n = 1,002) in 2 commercial dairy herds in Germany were examined for endometritis at 21 to 27 d in milk (DIM) by using 1 of 3 vaginal diagnostic methods. Vaginal examinations were performed either with a speculum (reference method), a vaginal device (Metricheck, Simcro, New Zealand), or a gloved hand. Vaginal discharge adhering to the diagnostic tool was classified according to a vaginal discharge score ranging from 0 to 3 (where 0 = translucent mucus, 1 = mucus containing flecks of white or off-white pus, 2 = less than 50% white or off-white mucopurulent material, and 3 = greater than 50% white or yellow pus that may be sanguineous). Cows with vaginal discharge scores of 1 to 3 received 500 μg of cloprostenol after examination and again 14 d later (35 to 41 DIM). The prevalence of endometritis in both herds was 40.6 and 40.3%, respectively. With the Metricheck device, significantly more cows were diagnosed as affected with endometritis than by examination with a speculum or a gloved hand (47.5 vs. 36.9 and 36.8%). Binary logistic regression for the risk of conception after first AI as an outcome variable, with vaginal discharge score, diagnostic method, and farm as covariates, revealed a significant effect of degree of endometritis, but not of the diagnostic methods. Survival analyses for the hazard of insemination and pregnancy within 200 DIM, respectively, revealed a significant effect of degree of endometritis, herd, and parity, but not of the diagnostic tool. It can be concluded that any one of the 3 vaginal examination methods can be used interchangeably, without a negative effect on reproductive performance. 相似文献
85.
Shovonlal Roy Shubha Sathyendranath Trevor Platt 《Journal of the Royal Society Interface》2011,8(58):650-660
The absorption coefficient of a substance distributed as discrete particles in suspension is less than that of the same material dissolved uniformly in a medium—a phenomenon commonly referred to as the flattening effect. The decrease in the absorption coefficient owing to flattening effect depends on the concentration of the absorbing pigment inside the particle, the specific absorption coefficient of the pigment within the particle, and on the diameter of the particle, if the particles are assumed to be spherical. For phytoplankton cells in the ocean, with diameters ranging from less than 1 µm to more than 100 µm, the flattening effect is variable, and sometimes pronounced, as has been well documented in the literature. Here, we demonstrate how the in vivo absorption coefficient of phytoplankton cells per unit concentration of its major pigment, chlorophyll a, can be used to determine the average cell size of the phytoplankton population. Sensitivity analyses are carried out to evaluate the errors in the estimated diameter owing to potential errors in the model assumptions. Cell sizes computed for field samples using the model are compared qualitatively with indirect estimates of size classes derived from high performance liquid chromatography data. Also, the results are compared quantitatively against measurements of cell size in laboratory cultures. The method developed is easy-to-apply as an operational tool for in situ observations, and has the potential for application to remote sensing of ocean colour data. 相似文献
86.
The authors address conceptual and methodological foundations of incremental validity in the evaluation of newly developed clinical assessment measures. Incremental validity is defined as the degree to which a measure explains or predicts a phenomenon of interest, relative to other measures. Incremental validity can be evaluated on several dimensions, such as sensitivity to change, diagnostic efficacy, content validity, treatment design and outcome, and convergent validity. Indices of incremental validity can vary depending on the criterion measures, comparison measures, and individual differences in samples. The authors review the rationale for, principles, and methods of incremental validation, including the selection of comparison and criterion measures, and address data analytic strategies and the conditional nature of incremental validity evaluations in the selection of measures. Incremental validity contributes to, but is different from, cost-benefits, which reflect the cost of acquiring the data and the benefits from the data. The impact of an incremental validity index on whether a measure is selected will be moderated by the cost of acquiring the new data, the importance of the measured phenomenon, and the clinical utility of the new data. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
87.
Since the XIV century the Pio Palace in Carpi (MO, Italy) has been subjected to many additions and rearrangements and, in the last decades, to wide restoration works. Nevertheless the XVII century main portal has not been restored yet, due to its complex and peculiar surface alteration forms in comparison with the other parts of the building, and still suffers a deep decay and degradation by complex chemical-physical processes. 相似文献
88.
Abstract. This paper obtains the joint limiting distribution of residuals and squared residuals of a general time‐series model. Based on this, we propose a mixed portmanteau statistic for testing the adequacy of fitted time‐series models. In some cases, it is shown that this statistic can be simply approximated by the sum of well‐known portmanteau statistics. The finite‐sample performance of the new test is compared with those of well‐known tests through simulations. 相似文献
89.
Wheel-flat diagnostic tool via wavelet transform 总被引:3,自引:0,他引:3
Vittorio Belotti Francesco Crenna Rinaldo C. Michelini Giovanni B. Rossi 《Mechanical Systems and Signal Processing》2006,20(8):1953-1966
The detection and acknowledgement of signatures, for condition monitoring and fault diagnostics by wavelet transform, deserves increased attention, due to its property of variable time–frequency resolution, which overcomes limitations of classical time–frequency approaches.In the paper, a diagnostic tool is presented, based on the wavelet transform, able to detect and to quantify the wheel-flat defect of a test train at different speeds and to measure the train speed with proper accuracy. The designed diagnostic tool minimises the hardware requirements, since only one accelerometer is needed, and provides results in real time.The results, achieved by an exhaustive experimental campaign, permit to validate the effectiveness of the diagnostic tool and to demonstrate the advantages of wavelet-based detection of signatures. 相似文献
90.