Lightning Surge Analysis for Overhead Lines Considering Corona Effect

Corona discharge characteristics are measured in a corona cage. The difference is found between the q–u curves under double exponential and damped oscillation surges. The behavior of the minor loops is revealed for the q–u curves under positive and negative damped oscillation surges. An extended improvement is made on the traditional approach for modeling of the q–u curves under damped oscillation surges. The extended approach has the capability of describing the complicated trajectory feature of the minor loops. On the basis of the extended approach, an efficient method is proposed for performing lightning surge analysis of overhead lines considering the corona effect. In the proposed method, an overhead line with corona is divided into a certain number of line segments. Each segment is converted into a circuit unit consisting of a non-linear branch and a linear circuit. With these circuit units connected in sequence, a complete equivalent circuit is constructed for the overhead line with corona. The transient responses can be obtained from the solution to the equivalent circuit. Then, the calculated results are compared with the field test results on a test overhead line.

Virtual Reality from the Standpoint of Complexity Science

An extended approach to the comprehension of virtual reality is developed in the article. Virtual reality is understood not only as a logically possible or cybernetically constructed reality but also as continuous turbulence of potencies of the complex natural and social world we live in, the wandering of complex systems and organizations over a field of possibilities, such a realization of forms and structures in which many formations remain in latent, potential forms, and are in the permanent process of making and multiplying a spectrum of possibilities, lead to the growth of the evolutionary tree of paths of development. It is shown that such an understanding of virtual reality corresponds to concepts and notions developed in the modern science of complexity. The most significant concepts are considered, such as the nonlinearity of time, the relationship of space and time, the uncertainty of the past and the openness of the future, the choice and construction of the future at the moments of passing the bifurcation points. Some cultural and historical prototypes of these modern ideas of virtual reality are given. It is substantiated that the vision of virtual reality being developed today can play the role of a heuristic tool for understanding the functioning and stimulation of human creativity.

An extended approach to value chain analysis

In the article, we propose a comprehensive methodology of value chain analysis in the international input–output framework that introduces a new measure of value chain participation and an extended typology of value chains, with the novel inclusion of domestic value chain to address the extent of fragmentation of purely domestic production. This allows for the simultaneous analysis of both global and domestic production fragmentation, the complex patterns of their evolution and their impact on economic development. The main contribution of the proposed methodology is conceptual: it permits the measurement of all value chain paths that pass through each country-sector from production to final consumption, whether the path includes downstream linkages, upstream linkages or their combination. Empirical application of this methodology shows the importance of including domestic fragmentation in value chain analysis: The fragmentation of both global and domestic levels of production has a significant positive correlation with economic growth. This implies that the effects of global production fragmentation must be analysed together with the changing structure of the fragmentation of domestic production to obtain the whole picture, one that might provide important information for policymaking and industrial policy.

A FUZZY FRONT-END PRODUCT DEVELOPMENT FRAMEWORK FOR START-UPS

Start-ups tend to form with a central idea that differentiates them from their competitors in the market. It is crucial for them to efficiently transform the idea into a marketable product. Prototyping helps to iteratively achieve a minimum viable product and plays a crucial role by enabling teams to test their ideas with limited resources early on. However, the prototyping process may have wrong focus leading to a suboptimal allocation of resources. Previously, we proposed role-based prototyping for fuzzy front-end development in small teams. It supports (1) resource allocation, (2) the definition of responsibilities, and (3) structuring the development process with milestones. In recent research this was a promising yet incomplete approach. We extend the previous work by refining the prototyping process by adding a prototyping matrix with two dimensions (purpose and lens), a prototyping cycle (plan, execute, test, reflect, assimilate), and a modified Kanban board (Protoban) for planning, managing, and reflecting cycles. This process, named PETRA was tested with a start-up developing an autonomous trash picking robot. The extended approach supported the team significantly in providing a clear idea of what to do at what time.

An Extended Approach to Predict Retinopathy in Diabetic Patients Using the Genetic Algorithm and Fuzzy C-Means

The present study is developed a new approach using a computer diagnostic method to diagnosing diabetic diseases with the use of fluorescein images. In doing so, this study presented the growth region algorithm for the aim of diagnosing diabetes, considering the angiography images of the patients’ eyes. In addition, this study integrated two methods, including fuzzy C-means (FCM) and genetic algorithm (GA) to predict the retinopathy in diabetic patients from angiography images. The developed algorithm was applied to a total of 224 images of patients’ retinopathy eyes. As clearly confirmed by the obtained results, the GA-FCM method outperformed the hand method regarding the selection of initial points. The proposed method showed 0.78 sensitivity. The comparison of the fuzzy fitness function in GA with other techniques revealed that the approach introduced in this study is more applicable to the Jaccard index since it could offer the lowest Jaccard distance and, at the same time, the highest Jaccard values. The results of the analysis demonstrated that the proposed method was efficient and effective to predict the retinopathy in diabetic patients from angiography images.

Shortcut Method for Initialization of Dividing Wall Columns and Estimating Pareto-Optimal NQ-curves

<p>In early project stages often no simulation results are available for dividing wall columns. Hence, shortcut methods are used to estimate suitable vapor and liquid splits. In a previous paper it was shown that Vmin diagrams are a suited tool to satisfy this need. However, it has turned out that it shows weaknesses for columns with finite or non-optimal stages. This contribution closes that gap and presents an extended approach to derive suited initial guesses. For this purpose, the original Vmin diagram is combined with a heuristic approach to calculate Pareto-optimal column designs resulting in a stage-adapted Vmin diagram. A comparative study shows that the new approach is a powerful tool to generate reliable guesses for multiple dividing wall column simulations with finite stage numbers.</p>

Shortcut Method for Initialization of Dividing Wall Columns and Estimating Pareto-Optimal NQ-curves

<p>In early project stages often no simulation results are available for dividing wall columns. Hence, shortcut methods are used to estimate suitable vapor and liquid splits. In a previous paper it was shown that Vmin diagrams are a suited tool to satisfy this need. However, it has turned out that it shows weaknesses for columns with finite or non-optimal stages. This contribution closes that gap and presents an extended approach to derive suited initial guesses. For this purpose, the original Vmin diagram is combined with a heuristic approach to calculate Pareto-optimal column designs resulting in a stage-adapted Vmin diagram. A comparative study shows that the new approach is a powerful tool to generate reliable guesses for multiple dividing wall column simulations with finite stage numbers.</p>

The Specific Fuel Consumption of Aircraft Engines (TSFC versus PSFC)

From a fundamental consideration of the efficiency (eta = P_out / P_in) it already follows that the power-specific fuel consumption, PSFC or c_P of an aircraft engine should be approximately constant, while c = c_P * V applies to the thrust-specific fuel consumption, TSFC or c in a first approach. Obviously, fuel is consumed already at static thrust (V=0). For this reason the thrust-specific fuel consumption needs an extended approach c = c_a + c_b * V. Breguet's range equation can certainly be described with a constant thrust-specific fuel consumption c, if c is determined for the cruise speed in question. However, this leads to an error if you want to use it to calculate an optimal flight speed in a flight performance calculation. It is recommended (for a first simple consideration) to write Breguet's range equation for jets with a constant power-specific fuel consumption c_P. This then leads to an optimal cruising speed for maximum range at minimum drag (md) V_md instead of 1.316 * V_md as it is determined with the "classic" derivation. For more detailed considerations, the "Herrmann model" should replace the simple equation c = c_a + c_b * V.