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Ice accumulated on conductor in transmission line can cause severe damage to the network. Various de-icing methods are introduced in details. According to the types of transmission lines, ice melting methods are classified into ac line de-icing and dc line de-icing. Different methods are described as many as possible. Then advantages and disadvantages of various de-icing methods are compared and the scope of application is presented.

BackgroundMany challenges are encountered in both teaching and learning veterinary obstetrics. This may be due to outdated teaching materials, as the main model of content transmission remains centred around text and images.MethodsVisualisation methods such as three-dimensional (3D) and Graphics Interchange Format (GIF) tools were applied in an attempt to improve obstetrics education outcomes in the third-year class. Traditional teaching methods were utilised in the fourth-year and fifth-year students.ResultsThese supplementary tools significantly increased the third-year students’ final examination results compared with the results of fourth-year and fifth-year students (P<0.05). These examinations were designed to evaluate comprehension of the subject matter. Self-assessment questionnaire results further indicated that 3D animation and GIF promoted learning efficiency.ConclusionIncorporation of 3D animation learning tools into the veterinary curriculum is predicted to better prepare students for the management of obstetrical cases after graduation.

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Droughts, considered one of the most dangerous and costly water cycle expressions, always occurs over a certain region, lasting several weeks or months, and involving multiple variables. In this work, a multivariate approach was used for the statistical characterization of hydrological droughts in Shaying River Basin with data from 1959–2008. The standard runoff index (SRI) and the run theory were employed to defined hydrological drought character variables (duration, severity, and intensity peak). Then, a multivariate joint probability analysis with four symmetric and corresponding asymmetric Archimedean Copulas was presented; and the multivariate frequency analysis with the joint return periods (Tand and Tor) were estimated. The results showed that the hydrological droughts have a severity of 4.79 and 5.09, and the drought intensity peak is of 1.35 and 1.50 in Zhoukou station and Luohe station, respectively; the rank correlation coefficients τ are more than 0.5, which means multivariate copulas can effectively describe the joint frequency distributions among multivariate variables. Drought risk shows a spatial variation: the downstream observed at Zhoukou station is characterized by a higher multivariate drought risk. In general, multivariate copulas provide a reliable method when constructing a comprehensive drought index and evaluating multivariate drought characteristics. Thus, this paper can provide useful indications for the multi-dimensional droughts’ risks assessment in Shaying River Basin.

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