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Copula-Based Statistical Health Grade System Against Mechanical Faults of Power Transformers
Chao Hu,Pingfeng Wang,Youn, B. D.,Wook-Ryun Lee,Joung Taek Yoon IEEE 2012 IEEE transactions on power delivery Vol.27 No.4
<P>A health grade system against mechanical faults of power transformers has been little investigated compared to those for chemical and electrical faults. This paper thus presents a statistical health grade system against mechanical faults in power transformers used in nuclear powerplant sites where the mechanical joints and/or parts are the ones used for constraining transformer cores. Two health metrics-RMS and root mean square deviation of spectral responses at harmonic frequencies-are first defined using vibration signals acquired via insite sensors on 54 power transformers in several nuclear powerplants in 16 months. We then investigate a novel multivariate statistical model, namely copula, to statistically model the populated data of the health metrics. The preliminary study shows that the proposed health metrics and statistical health grade system are feasible to monitor and predict the health condition of the mechanical faults in the power transformers.</P>
Chao Li,Baihong Li,Guoming Gao,Lijun Zhang,Shu Zhang,Lei Zhang,Jun Xiang,Song Hu,Yi Wang,Xun Hu 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.125 No.-
Drying at 100 C is a common practice for processing many biomasses for their further thermochemicalconversion via the routes such as pyrolysis. The drying temperature of 100 C is low, but might not be toolow to cause any impact on pyrolytic behaviors of a biomass feedstock. In this study, varied scenarios ofthermal pretreatment of poplar sawdust (oven-drying, boiling in water and microwave heating) at 100 Cwere screened for probing their potential influence on the pyrolytic behaviors at 500 and 750 C. Comparing with oven-drying, boiling in water (cooking) and microwave heating at 100 C could removesome oxygen-containing species, increasing carbon content of the pretreated sawdust and promotingcarbonization in pyrolysis. This enhanced formation of biochar, heavy p-conjugated organics in bio-oil,but suppressed generation of gas. The cooking or microwave heating pretreatment also promoted aromatizationto form the biochar of higher thermal stability, higher crystallinity, and higher aromatic degree,due to the enhanced deoxygenation reactions in the pyrolysis. The in-situ IR characterization suggestedthat microwave pretreatment promoted generation of unsaturated ketones and also the species with olefinicC = C, favoring their further aromatization. The cooking pretreatment impacted transformationroutes of the oxygen-containing organics, thus modifying pyrolysis behaviors of the pretreated sawdust.
Chao-bin Wang,Hui Wang,Jun-shuang Zhao,Ze-jun Wu,Hao-dong Liu,Chao-jia Wang,An-rong Li,Dawei Wang,Juntao Hu 대한신경외과학회 2023 Journal of Korean neurosurgical society Vol.66 No.5
Penetrating head injury is a serious open cranial injury. In civilians, it is often caused by non-missile, low velocity flying objects that penetrate the skull through a weak cranial structure, forming intracranial foreign bodies. The intracranial foreign body can be displaced due to its special quality, shape, and location. In this paper, we report a rare case of right-to-left displacement of an airgun lead bullet after transorbital entry into the skull complicated by posttraumatic epilepsy, as a reminder to colleagues that intracranial metal foreign bodies maybe displaced intraoperatively. In addition, we have found that the presence of intracranial metallic foreign bodies may be a factor for the posttraumatic epilepsy, and their timely removal appears to be beneficial for epilepsy control.
A meso-scale approach to modeling thermal cracking of concrete induced by water-cooling pipes
Chao Zhang,Wei Zhou,Gang Ma,Chao Hu,Shaolin Li 사단법인 한국계산역학회 2015 Computers and Concrete, An International Journal Vol.15 No.4
Cooling by the flow of water through an embedded cooling pipe has become a common and effective artificial thermal control measure for massive concrete structures. However, an extreme thermal gradient induces significant thermal stress, resulting in thermal cracking. Using a mesoscopic finite-element (FE) mesh, three-phase composites of concrete namely aggregate, mortar matrix and interfacial transition zone (ITZ) are modeled. An equivalent probabilistic model is presented for failure study of concrete by assuming that the material properties conform to the Weibull distribution law. Meanwhile, the correlation coefficient introduced by the statistical method is incorporated into the Weibull distribution formula. Subsequently, a series of numerical analyses are used for investigating the influence of the correlation coefficient on tensile strength and the failure process of concrete based on the equivalent probabilistic model. Finally, as an engineering application, damage and failure behavior of concrete cracks induced by a water-cooling pipe are analyzed in-depth by the presented model. Results show that the random distribution of concrete mechanical parameters and the temperature gradient near water-cooling pipe have a significant influence on the pattern and failure progress of temperature-induced micro-cracking in concrete.
Hui-Chao Hu,Hui-Jun Jin,Xin-Sheng Chai 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.1
This paper reports an improved headspace gas chromatographic (HS-GC) technique for thedetermination of oxalate content in bleaching effluents. The method is based on the redox reactionbetween potassium iodate and oxalate, from which the carbon dioxide is generated and measured by HSGC. The results showed that the reaction in a sulfuric acid solution (0.05 mol/L) was complete in 35 minat 95 ℃. The RSD of the method in the repeatability testing was less than 4.5%, the LOQ was 0.35 mg, andthe recovery ranged from 95 to 103%. The present method is simpler, more reliable, and more practicalcompared to the methods reported previously.
Hui-Chao Hu,Xin-Sheng Chai,Ying-Xin Tian,Wei-Feng Si,Gang Chen 한국공업화학회 2013 Journal of Industrial and Engineering Chemistry Vol.19 No.3
This paper reports on a headspace gas chromatographic method (HS-GC) for the determination of residual formaldehyde in formaldehyde related polymer latexes. The method is based on the reaction between formaldehyde and borohydride in a sodium hydroxide solution (1 mol/L), in which formaldehyde is quantitatively converted to methanol within 30 min at 90 8C and then determined by HS-GC. The results showed that the repeatability of the method had a relative standard deviation of less than 5.0%; the limit of quantification (LOQ) was 17.3 mg, and the recovery ranged from 96.2–102%. The present method is simple, rapid, and accurate.
Modification of a Smoking Motivation Questionnaire for Chinese Medical Students
Jiang, Chao,Sun, Wen-Jie,Wan, Yan-Chun,Wei, Ming-Wei,Mu, Yong-Ping,Tarver, Siobhan L.,Gao, Yong-Qing,Hu, Tian,Xu, Chao,Gordon, James,Feng, Cindy Xin,Wen, Yu-Feng Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.6
Introduction: Smoking prevalence among the medical students is high in China. Therefore, understanding the smoking motivations of medical students is crucial for smoking control, but currently there are no scales questionnaires customized for probing the smoking motivations of medical students. This aim of study was to test and modify a questionnaire for investigating smoking motivations among medical students. Methods: A cross-sectional survey was conducted among 1,125 medical students at Xuzhou Medical College in China in 2012.The model fit and validity was assessed by confirmatory factor analysis (CFA) and the reliability was tested by single-item reliability, composite reliability, and item-total correlation. Results: The prevalence of smoking was 9.84 % among study population. In the modified scales, the global fit indices identified a CFI value of 0.96, TLI was 0.96, and the RMSEA was 0.063. CFA supported the two dimensional structure of the instrument. The average variance extracted ranged from 0.45 to 0.62. All single-item reliability scores were greater than 0.20, and the composite reliability ranged from 0.74 to 0.91. Conclusion: Modified scales could be the preliminary instrument used in evaluating the smoking motivations of medical students. However, it should be further assessed using other forms and methods of validity and reliability, additional motivations of smoking, and the survey of other medical colleges in China.