Optimal Risk Transfer:A Numerical Optimization Approach

Capital efficiency and asset/liability management are part of the Enterprise Risk Management Process of any insurance/reinsurance conglomerate and serve as quantitative methods to fulfill the strategic planning within an insurance organisation. There has been a considerable amount of work in this ample research field, but invariably one of the last questions is whether or not, numerically, the method is practically implementable, which is our main interest. The numerical issues are dependent upon the traits of the optimisation problem and therefore, we plan to focus on the optimal reinsurance design, which has been a very dynamic topic in the last decade. The existing literature is focused on finding closed-form solutions that are usually possible when economic, solvency, etc constraints are not included in the model. Including these constraints, the optimal contract can only be found numerically. The efficiency of these methods is extremely good for some well-behaved convex problems, such as the Second-Order Conic Problems. Specific numerical solutions are provided in order to better explain the advantages of appropriate numerical optimisation methods chosen to solve various risk transfer problems. The stability issues are also investigated together with a case study performed for an insurance group that aims capital efficiency across the entire organisation

Robust and Pareto Optimality of Insurance Contract

The optimal insurance problem represents a fast growing topic that explains the most efficient contract that an insurance player may get. The classical problem investigates the ideal contract under the assumption that the underlying risk distribution is known, i.e. by ignoring the parameter and model risks. Taking these sources of risk into account, the decision-maker aims to identify a robust optimal contract that is not sensitive to the chosen risk distribution. We focus on Value-at-Risk (VaR) and Conditional Value-at-Risk (CVaR)-based decisions, but further extensions for other risk measures are easily possible. The Worst-case scenario and Worst-case regret robust models are discussed in this paper, which have been already used in robust optimisation literature related to the investment portfolio problem. Closed-form solutions are obtained for the VaR Worst-case scenario case, while Linear Programming (LP) formulations are provided for all other cases. A caveat of robust optimisation is that the optimal solution may not be unique, and therefore, it may not be economically acceptable, i.e. Pareto optimal. This issue is numerically addressed and simple numerical methods are found for constructing insurance contracts that are Pareto and robust optimal. Our numerical illustrations show weak evidence in favour of our robust solutions for VaR-decisions, while our robust methods are clearly preferred for CVaR-based decisions

Investigation of hybridized bluff bodies for flow-induced vibration energy harvesting

Small-scale wind energy harvesting based on flow-induced vibration (FIV) mechanisms has attracted lots of research interest in recent years. Vortex-induced vibration (VIV) and galloping energy harvesters usually outperform each other in different wind-speed ranges. To combine the advantages of VIV and galloping harvesters, this paper explores the idea of using a hybridized bluff body constituting of two cylindrical and one cuboid segment for wind energy harvesting. The total length of the hybridized bluff body was fixed. The cuboid segment length was varied to investigate the effect on the FIV behavior of the bluff body. The results show that, when the cuboid segment is short in length, the bluff body exhibits VIV-like behavior in the low wind-speed range and galloping-like behavior in the high-speed range. In the medium wind-speed range, galloping-VIV coupling appears. However, if the cuboid segment is longer, the galloping-VIV coupling phenomenon disappears; the hybridized bluff body behaves just like a cuboid one and only exhibits a galloping motion. In addition to experiments, computational fluid dynamics (CFD) simulations are also conducted to provide more insights into the aerodynamics of the hybridized bluff body. The simulation results reveal that introducing hybridization into the bluff body changes the vorticity flow behind it and alters the vortex-shedding behavior. The vortex-shedding effect, in turn, affects the vibration of the bluff body, as well as the performance of the harvester.This work was supported by the National Natural Science Foundation of China (Grant No. 51977196) and the Henan Province Science Foundation for Youths (202300410422)

Study on Synergistic Corrosion Inhibition Effect between Calcium Lignosulfonate (CLS) and Inorganic Inhibitors on Q235 Carbon Steel in Alkaline Environment with Cl−

The synergistic corrosion inhibition effect between calcium lignosulfonate (CLS) and three kinds of inorganic inhibitors (Na2MoO4, Na2SnO3, and NaWO4) with various molar ratios on Q235 carbon steel in alkaline solution (pH 11.5) with 0.02 mol/L NaCl was investigated by cyclic potentiodynamic polarization, electrochemical impedance spectroscopy, linear polarization, scanning electron microscopy, and X-ray photoelectron spectroscopy. Molybdate and stannate in hybrid inhibitor could promote the passivation of steel and form a complex film, which could suppress the corrosion effectively. Moreover, the insoluble metal oxides in the complex film formed by three kinds of inorganic inhibitor could help the adsorption of CLS onto the steel surface. The CLS molecules could adsorb onto the steel surface and metal oxides to form an adsorption film to protect the steel from corrosion. A three-layer protection film formed by a hybrid inhibitor, including passivation film, deposition film, and adsorption film, would effectively inhibit the corrosion reactions on the steel surface. The CLS compound with molybdate with the ratio of 2:3 shows the best inhibition effect on both general corrosion and localized corrosion

In-Situ Monitoring and Analysis of the Pitting Corrosion of Carbon Steel by Acoustic Emission

The acoustic emission (AE) technique was applied to monitor the pitting corrosion of carbon steel in NaHCO3 + NaCl solutions. The open circuit potential (OCP) measurement and corrosion morphology in-situ capturing using an optical microscope were conducted during AE monitoring. The corrosion micromorphology was characterized with a scanning electron microscope (SEM). The propagation behavior and AE features of natural pitting on carbon steel were investigated. After completion of the signal processing, including pre-treatment, shape preserving interpolation, and denoising, for raw AE waveforms, three types of AE signals were classified in the correlation diagrams of the new waveform parameters. Finally, a 2D pattern recognition method was established to calculate the similarity of different continuous AE graphics, which is quite effective to distinguish the localized corrosion from uniform corrosion

Design,Fabrication,and Testing of Single-Side Alignment of 16×0.8nm Arrayed-Waveguide Grating

A novel design of 100GHz-spaced 16channel arrayed-waveguide grating (AWG) based on silica-on-silicon chip is reported.AWG is achieved by adding a Y-branch to the AWG and arranging the input/output channel in a neat row,so the whole configuration can be aligned and packaged using only one fiber-array.This configuration can decrease the device's size,enlarge the minimum radius of curvature,save time on polishing and alignment,and reduce the chip's fabrication cost

New Advances in Fluid–Structure Interaction

Fluid–structure interactions (FSI) play a crucial role in the design, construction, service and maintenance of many engineering applications, e [...

Theoretical and experimental investigation of magnet and coil arrays optimization for power density improvement in electromagnetic vibration energy harvesters

Power density is a critical evaluation indicator of electromagnetic vibration energy harvesters and has become one of the research hotspots. Therefore, it is of great significance to establish a simple and accurate theory to optimize and guide the design of an energy harvester for power density enhancement. Indeed, an alternating magnet array has a high flux gradient, which is one of the key factors for power enhancement. Under volume constraints, the coil output power is highly related to the magnet configuration, as the latter determines the magnitude of the flux gradient as well as the total flux mutation. Motivated by this, in this paper, an electromagnetic vibration energy harvester based on a coil array and a magnet array is proposed. The magnetic field distribution of rectangular magnets is analyzed. Then, a theoretical model based on Faraday's law of electromagnetic induction is derived to efficiently calculate the open-circuit voltage of coils with different numbers of magnets. After that, the optimal magnetic configuration is obtained based on the developed model without the need of measuring the parasitic damping of the energy harvester. Simulations and experiments verify the correctness of the theory. The results show that at an acceleration of 1 g and frequency of 41.2 Hz, the output power and power density reach a maximum of 3.71 mW and 106.6

New Advances in Fluid–Structure Interaction

Fluid–structure interactions (FSI) play a crucial role in the design, construction, service and maintenance of many engineering applications, e [...

On the investigation of ash deposition effect on flow-induced vibration energy harvesting

This paper proposes harnessing the aerokinetic energy in flue systems and it explores the ash deposition effect on flow-induced vibration energy harvesting performance. Bell-shaped and horn-like bluff bodies are designed to simulate different ash depositions on a conventional elliptic cylinder bluff body. Wind tunnel experiments were conducted to investigate the energy harvesting performance using different ash depositions distributed over the bluff bodies. The experimental results show that compared to the baseline model of a conventional elliptic cylinder bluff body, the bell-shaped bluff body suppresses the flow-induced vibration and deteriorates the energy harvesting performance. In contrast, the horn-like bluff body can benefit energy harvesting by reducing the galloping cut-in wind speed and increasing the voltage output. The voltage output of an optimal prototype using the horn-like bluff body is increased by 516%. Computational fluid dynamics (CFD) simulations were carried out to unveil the physical mechanisms behind the phenomena. The CFD analysis results indicate that the appearance of the small-scale secondary vortices (SV) widens the wake flow and increases the aerodynamic force produced by the horn-like bluff body. The flow-induced vibration of the harvester using the horn-like bluff body transforms from VIV to galloping. Therefore, it has been preliminarily demonstrated that the unfavorable ash deposition phenomenon in flue systems has the potential for promoting flow-induced vibration energy harvesting.This work was supported by the National Natural Science Foundation of China (Grant No. 51977196), the China Postdoctoral Science Foundation (Grant No. 2020 T130557), the Natural Science Foundation of Excellent Youth of Henan Province (Grant No. 222300420076), and the State Key Laboratory of Structural Analysis for Industrial Equipment, Dalian University of Technology, China (GZ21114)