154,994 research outputs found
Epitrimerus sessiliflorensis Xue & Hong 2011
No full textEpitrimerus sessiliflorensis Xue & Hong, 2011 Epitrimerus sessiliflorensis Xue & Hong, 2011: 306–309. Host. Eleutherococcus sessiliflorus (Rupr. et Maxim.) S. Y. Hu. (Araliaceae). Relation to host. Vagrant. Distribution. China (Heilongjiang).Published as part of XUE, XIAO-FENG, GUO, JING-FENG & HONG, XIAO-YUE, 2013, Eriophyoid mites from Northeast China (Acari: Eriophyoidea) , pp. 1-123 in Zootaxa 3689 (1) on page 58, DOI: 10.11646/zootaxa.3689.1.1, http://zenodo.org/record/603121
Abnormal effects of line fault location on transient stability and its mechanism
No full textIt is discovered that the transient stability degree may change with the fault location of a transmission line in a concave form, instead of commonly accepted monotonic increase, monotonic decrease or convex form. The mechanism of the concave change form is revealed by the extended equal area criterion(EEAC) theory and its analytical conditions are obtained for one-machine infinite-bus systems. Meanwhile, the abnormal form, which the transient stability margin varies with the fault location is verified in multi-machine systems by simulations. The discovery and investigation of this phenomenon not only contribute to a better understanding of the physical nature of the power system transient stability, but also present a new warning for the engineering analysis
A review of non-deterministic analysis for power system transient stability
No full textThe status of probabilistic analysis and risk assessments for transient stability is reviewed, in terms of stochastic variables, probabilistic models, probabilistic algorithms, deterministic transient stability consequence assessments of a specifically scenario and other aspects. The principle, advantages and disadvantages of various assessment methods are summarized, and the techniques capable of decreasing computation burden are discussed. The development direction of probability and risk assessments for transient stability is also explored. It is pointed out that using sensitivity analysis to reduce the number of simulation cases will considerably decrease computational burden. It is also proposed to use the optimum control cost to reflect economic loss due to the system instability, which means using controllable outages to replace the uncontrolled outages and makes risk analysis practical
Non-deterministic analysis for transient stability based on transient stability domain and conditional probability
No full textTaking the most serious value within the credible region of each stochastic variable as the basic operating condition, the transient stability domain (TSD) in continuous parameter space is estimated by using stability margin and its sensitivity analysis technologies. The probability of the non-deterministic condition that is inside (or outside) the TSD is calculated by using the joint probability density function, namely the stability (or instability) probability. The 3-dimension TSD consisting of load level, fault location on a line and fault clearing time is estimated. Meanwhile, discrete random variables including system configuration, faulted element and fault type are handled with conditional probability. The whole instability probability is then computed. A new risk index is also defined to evaluate the instability risk. Simulations on IEEE 39-bus system and 500 kV Shandong system show that the proposed method is effective and practical
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Dialoguing with the World: Xue Yiwei and His Traveling with Marco Polo
No full textThis essay introduces the author Xue Yiwei and his Traveling with Marco Polo, a creative collection that dialogues with Invisible Cities by the postmodern Italian writer Italo Calvino. While Calvino imagines a young Marco Polo describing the fantastic sights of fifty-five cities to an aging Kublai Khan, Xue Yiwei joins the conversation and provides a meticulous explication of each one of Calvino’s cities. Furthermore, Traveling with Marco Polo expands the imaginary cityscapes to include oblique commentaries on the past, present, and future of China as well as the profound meditation on the city as a microcosm of our world. The result is a daring literary experiment that is representative of Xue’s oeuvre overall: at once giving a powerful literary representation of modern Chinese history while engaging in dialogue with writers from all over the world
Adaptive optimal restoration control for interconnected grids
No full textThe model of optimal restoration control considering the income from restored loads and control cost, as well as the control risk is presented. A two-layer framework for optimizing is proposed, which uses a procedure of 'parallel optimization for subareas and dynamic coordination among subareas', to overcome the drawback of offline made restoration schemes based on fixed scenarios and fixed priority for countermeasures. Moreover, restoration strategy is extended from bottom-up one, which is widely discussed nowadays, to top-down one as well as hybrid one. Studies include the inner optimization of each strategy and coordination between different strategies. Based on a viewpoint of adaptive optimization and risk decision-making, related modules and algorithms are designed A framework of the online decision support system is presented, the three parts of which are information collecting, analysis and control. The validity and adaptiveness of the decision support system are verified by simulations
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Traveling with Marco Polo: Selected Excerpts
No full textPublished in 2012, Chinese writer Xue Yiwei’s Traveling with Marco Polo is a creative collection that dialogues with Invisible Cities by the postmodern Italian writer Italo Calvino. While Calvino imagines a young Marco Polo describing the fantastic sights of fifty-five cities to an aging Kublai Khan, Xue Yiwei joins the conversation and gives meticulous explication of each one of Calvino’s cities. The following excerpts were translated from the Chinese version of Traveling with Marco Polo by Hu Ying
A review on restorative control in interconnected grids under electricity market environment
No full textRequirements of modern inter-connected grids on restorative control are first clarified, followed by a summary on state-of-the-art of researches on the bottom-up, top-down and hybrid restoration strategies. From both technical and economic prospects, functions of a decision support system are pointed out. Based on risk analysis, an adaptive decision support system is proposed, influence of electricity market environment on blackstar-t service analyzed, and coordination between risk management and technical optimization discussed. In addition, it is emphasized that the technical performance of the startup service and the risk cost of blackout can be expressed by quantitative indices and added into the objective function for the optimization
The etiology of esophageal cancer in high- and low- risk areas of Jiangsu province, China
No full text [Background]Esophageal cancer (EC) remains one of the most common and fatal malignancies worldwide. The geographic variation in EC occurrence is striking, and China is an area with one of the highest incidences of EC. A number of epidemiological studies have been conducted toward EC in the past decades, results suggested that tobacco smoking, alcohol drinking, unhealthy dietary factors and chronic injuries of the esophageal mucosa are important in the development of this disease. Genetic polymorphisms in enzymes involved in metabolism of carcinogens may also influence individual susceptibility. However, the effects of major lifestyle and hereditary risk factors on the development of EC remain poorly understood in China. Moreover, little attention has been paid to the etiological heterogeneity between similar areas with great risk gradient. [Methods]From 2003 to 2007, a large population-based case-control study of EC has been conducted in a selected high-risk area and a selected low-risk area of Jiangsu Province, one of the highest cancer incidence areas in China. In total, 1,520 cases and 3,879 controls were recruited. In this thesis, we evaluated the role of major lifestyle factors such as tobacco smoking, alcohol drinking and dietary factors, as well as inherited determinants including family history of cancer and genetic polymorphisms of alcohol-metabolizing related genes on the risk of EC. In addition, we investigated how much of the risk gradient between two areas could be explained by variation in the distributions of major risk factors. [Results] Tobacco smoking and alcohol drinking moderately increased the risk of EC, while the positive associations were only found among men but not among women. Dietary factors were observed to play important roles in the development of EC. Specific dietary habits i.e., fast eating speed, and hot eating and/or drinking substantially elevated EC risk and could explain more than 20% of EC cases each. High intake of salty foods and fried foods, low consumption of raw garlic were also observed to increase the risk of EC. In addition to environmental and lifestyle factors, we confirmed that a positive family history can significantly increase EC risk, and found the inheritance may modify the effect of some unhealthy lifestyles. Moreover, we further explored the relationship between EC and single nucleotide polymorphismsof ADH1B, ADH1C and ALDH2 genes. Results showed that the slow metabolizing ADH1B G allele, ADH1C G allele and ALDH2 A allele significantly increased EC risk among moderate-to-heavy alcohol drinkers, and a significant interaction was observed between ALDH2 gene and alcohol consumption. Lastly, we found that more than 60% of EC cases could be attributable to major lifestyle risk factors in the study population; furthermore, dissimilar distribution of several lifestyle factors, together with variations of hereditary factors may be largely responsible for the incidence difference between two study areas. [Conclusion]The findings in this thesis confirm that unhealthy lifestyles including smoking, alcohol drinking and some dietary factors are the predominant risk factors of EC in China, and a large proportion of incidence difference between regions at varying risk could be attributed to the different prevalence of lifestyle factors. As most of the identified risk factors are modifiable, these could be translated into risk reduction prevention programs in China, and a substantial proportion of new EC cases are expected to be prevented by eliminating or avoiding these risk factors in the population. </p
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