Methodology for calculating rope drums for stability

. The problems of the stability of rope drums are quite urgent. The rope drum is in most cases a thin-walled shell, which, under the influence of external pressure from the rope, can lead to loss of stability. The stability issues of the drum shell, which is loaded with rope turns, are very important, because the safety and reliability of the rope hoist is directly related to them The studies carried out made it possible to obtain a new method for calculating the stability of cylindrical shells, which takes into account not only the length of the shell, but also the rigidity of the connection with the head. In addition, a calculation formula was obtained to determine the critical pressure of the oval shell, which gives a fairly good agreement with the experiments of American scientists. The work also considered the effect of the difference in wall thickness on the critical load of the drum. The studies carried out made it possible to conclude that the parameters of the rope drums make it possible to completely eliminate the need to install rings and stiffeners. Also as a result of research it was found that the shell of the crane drum under the influence of a radial load cannot lose stability. Studies have shown that in all cases the stability margin of the rope drum shell is greater than the strength margin. In this case, the load created by the rope wound on the drum is considered, with the ratios of the radius of the drum and the rope typical for crane construction. In addition, a coefficient was established that takes into account the elasticity of the shell-head joint. The studies carried out have shown that such initial deviations of the drum shell shape as ovality do not give a significant increase in the critical load. The results obtained are quite important, since they allow reducing the metal consumption of the rope drum shell and at the same time ensuring its reliable operation. A decrease in metal consumption is achieved by reducing the thickness of the shell and the absence of the need to install rings and stiffeners. This will lead to a decrease in metal consumption and energy consumption of the crane itself, and also simplifies the technology of manufacturing a rope drum.

Sensitivity-Based Non-Linear Model Predictive Control for Aircraft Descent Operations Subject to Time Constraints

The ability to meet a controlled time of arrival while also flying a continuous descent operation will enable environmentally friendly and fuel efficient descent operations while simultaneously maintaining airport throughput. Previous work showed that model predictive control, a guidance strategy based on a reiterated update of the optimal trajectory during the descent, provides excellent environmental impact mitigation figures while meeting operational constraints in the presence of modeling errors. Despite that, the computational delay associated with the solution of the trajectory optimization problem could lead to performance degradation and stability issues. This paper proposes two guidance strategies based on the theory of neighboring extremals that alleviate this problem. Parametric sensitivities are obtained by linearization of the necessary conditions of optimality along the active optimal trajectory plan to rapidly update it for small perturbations, effectively converting the complex and time consuming non-linear programming problem into a manageable quadratic programming problem. Promising results, derived from more than 4000 simulations, show that the performance of this method is comparable to that of instantaneously recalculating the optimal trajectory at each time sample.

A Combined RMS Simulation Model for DFIG-Based and FSC-Based Wind Turbines and Its Initialization

Reconstructable dynamic simulation models of modern variable-speed wind turbines (WTs), which are integrable into any simulation software, are crucial to the scientists investigating the contribution of WTs to counteracting the current power system stability issues. The structural similarity between a doubly fed induction-generator-based (DFIG-based) WT model and a full-scale-convertor-based (FSC-based) WT model using induction generator offers the possibility of integrating them into a combined modular model with little effort and the same used parameter set. This article presents a combined root mean square (RMS) WT model, which contains a DFIG-based WT and a FSC-based WT using induction generator. The model is designed based on fundamental machine and converter equations and can be applied for classical network stability analyses. Furthermore, analogous well-performing initialization procedures for both DFIG-based and FSC-based WT models are also introduced. As an example, to demonstrate the performance of the WT model in frequency stability studies, the model is extended with a droop-based fast frequency response (FFR) controller and is implemented in a MATLAB-based RMS simulation tool. The results of the case studies confirmed a solid functionality of initialization procedures. Furthermore, they illustrate feasible and comparable general behavior of both WT models as well as their plausible responses in the event of a frequency drop in a 220 kV test system.

Stability Analysis for Linear Uncertain Switched Systems in Infinite-time Domain

In this work, an uncertain switched system expressed as a series of uncertain differential equations is considered in depth. Stability issues have been widely investigated on switched systems while few results related to stability analysis for uncertain switched systems can be found. Due to such fact, three different stabilities, including stability in measure, almost sure stability and stability in mean, are comprehensively studied for linear uncertain switched systems in infinite-time domain. Internal property of the systems is able to be illustrated from different perspectives with the help of above stability analysis. By employing uncertainty theory and the feature of switched systems, corresponding judgement theorems of these stabilities are proposed and verified. An example with respect to stability in measure is provided to display the validness of the results derived.

Polymeric Membranes for H2 and N2 Separation

H2 and N2 separations are of paramount importance to the global development of clean energy and environment. While the traditional thermal-driven processes are often deemed overly energy-intensive, the polymeric membrane technology presents an energy-efficient and potentially cost-effective alternative that comes with many operational and environmental advantages to offer. However, a variety of key challenges revolving around the membrane performance and stability issues require new material innovations in order to be eventually overcome. This chapter provides the background for polymeric gas separation membranes and also a detailed evaluation on state-of-the-art polymeric membrane materials for H2 and N2 separations. Performance enhancement strategies will also be discussed in the later parts.

Low-rank tensor approximation of singularly perturbed boundary value problems in one dimension

We derive rank bounds on the quantized tensor train (QTT) compressed approximation of singularly perturbed reaction diffusion boundary value problems in one dimension. Specifically, we show that, independently of the scale of the singular perturbation parameter, a numerical solution with accuracy $$0<\varepsilon <1$$ 0 < ε < 1 can be represented in the QTT format with a number of parameters that depends only polylogarithmically on $$\varepsilon $$ ε . In other words, QTT-compressed solutions converge exponentially fast to the exact solution, with respect to a root of the number of parameters. We also verify the rank bound estimates numerically and overcome known stability issues of the QTT-based solution of partial differential equations (PDEs) by adapting a preconditioning strategy to obtain stable schemes at all scales. We find, therefore, that the QTT-based strategy is a rapidly converging algorithm for the solution of singularly perturbed PDEs, which does not require prior knowledge on the scale of the singular perturbation and on the shape of the boundary layers.

Judicial Dictatorship: Potential Institutionalisations of the Constitutional Review Process

<p>This paper concerns constitutional review of legislation, a widely discussed issue within comparative constitutional law. Specifically, this paper addresses the issue of the lack of democratic legitimacy that U.S. style judicial review has and the potential lack of stability that other weak form constitutional review mechanisms have. Three constitutional review procedures are proposed in this paper, with the commonly overlooked executive branch playing a central role in each review mechanism. These proposed procedures aim to solve democratic legitimacy and stability issues. While all three arguably accomplish the mentioned goal, the paper addresses the issues each proposed mechanism has before defending the leading mechanism. The paper offers a possible solution to the seemingly unresolvable tension within constitutional review of parliamentary sovereignty and judicial supremacy. The described mechanisms and the outcomes they produce seems to show that democratically based constitutional review is possible and it is not necessary to rely on unelected judges to ensure that constitutional rights are maintained. Ultimately, this paper aims to show that a redistribution of constitutional review power among all state organs is the best way to ensure that legislation conforms to constitutional norms.</p>

Judicial Dictatorship: Potential Institutionalisations of the Constitutional Review Process

<p>This paper concerns constitutional review of legislation, a widely discussed issue within comparative constitutional law. Specifically, this paper addresses the issue of the lack of democratic legitimacy that U.S. style judicial review has and the potential lack of stability that other weak form constitutional review mechanisms have. Three constitutional review procedures are proposed in this paper, with the commonly overlooked executive branch playing a central role in each review mechanism. These proposed procedures aim to solve democratic legitimacy and stability issues. While all three arguably accomplish the mentioned goal, the paper addresses the issues each proposed mechanism has before defending the leading mechanism. The paper offers a possible solution to the seemingly unresolvable tension within constitutional review of parliamentary sovereignty and judicial supremacy. The described mechanisms and the outcomes they produce seems to show that democratically based constitutional review is possible and it is not necessary to rely on unelected judges to ensure that constitutional rights are maintained. Ultimately, this paper aims to show that a redistribution of constitutional review power among all state organs is the best way to ensure that legislation conforms to constitutional norms.</p>

Cascade Approaches Towards the Synthesis of Daphnioldhanin A Alkaloid

<p>Daphnioldhanin A 1.6 is a recent alkaloid obtained from Daphyniphyllum plants. The core structure as shown consists of a 5,5,7 tricyclic ring system, which is a challenging ring system and to date has not been reported in any other natural product. This project focussed on using two cascade approaches in forming this ring system, namely radical addition and cyclisation cascade and carbene cycloaddition cyclisation cascade CCCC. Using the radical approach would require a 5-endo trig cyclisation, which is disfavoured by Baldwin's rules, but has been reported in systems which have an hetereoatom (carbonyl, nitrogen or sulfur) incorporated in the ring. In our case, the 5-endo trig cyclisation is needed in an all carbon containing ring, and preliminary modelling studies have shown that the energy for the 4-exo trig cyclisation product is higher than that of the 5-endo trig cyclisation product. Therefore, the radical approach if successful will eventuate in a novel 5-endo trig cyclisation in an all carbon system. However, due to stability issues with the radical precursors this method had to be abandoned and attention focused on the CCCC approach. For the CCCC approach, rhodium catalysed cascade cyclisation is intended on diazo compound 1.22. The presence of the intramolecular double bond enhances the second cyclisation to occur which will form the 5 and 7-membered ring simultaneously along with oxo-bridge resulting in the functionalised pentacyclic ring system which would be very similar to the proposed 5,5,7 core of Daphnioldhanin A. The desired diazo compound could not synthesised due to failure in forming the anhydride for the acid and future work would be focussed on forming acid derivatives in order to form the diazo compound 1.22 before using rhodium catalysed cyclisation to form the functionalised pentacyclic compound.</p>

Cascade Approaches Towards the Synthesis of Daphnioldhanin A Alkaloid

<p>Daphnioldhanin A 1.6 is a recent alkaloid obtained from Daphyniphyllum plants. The core structure as shown consists of a 5,5,7 tricyclic ring system, which is a challenging ring system and to date has not been reported in any other natural product. This project focussed on using two cascade approaches in forming this ring system, namely radical addition and cyclisation cascade and carbene cycloaddition cyclisation cascade CCCC. Using the radical approach would require a 5-endo trig cyclisation, which is disfavoured by Baldwin's rules, but has been reported in systems which have an hetereoatom (carbonyl, nitrogen or sulfur) incorporated in the ring. In our case, the 5-endo trig cyclisation is needed in an all carbon containing ring, and preliminary modelling studies have shown that the energy for the 4-exo trig cyclisation product is higher than that of the 5-endo trig cyclisation product. Therefore, the radical approach if successful will eventuate in a novel 5-endo trig cyclisation in an all carbon system. However, due to stability issues with the radical precursors this method had to be abandoned and attention focused on the CCCC approach. For the CCCC approach, rhodium catalysed cascade cyclisation is intended on diazo compound 1.22. The presence of the intramolecular double bond enhances the second cyclisation to occur which will form the 5 and 7-membered ring simultaneously along with oxo-bridge resulting in the functionalised pentacyclic ring system which would be very similar to the proposed 5,5,7 core of Daphnioldhanin A. The desired diazo compound could not synthesised due to failure in forming the anhydride for the acid and future work would be focussed on forming acid derivatives in order to form the diazo compound 1.22 before using rhodium catalysed cyclisation to form the functionalised pentacyclic compound.</p>