Essays on Risk Management of Insurance Companies

This dissertation is devoted to studying the risk management of insurance companies. It focuses on risk management behaviors such as investment, portfolio management, and derivative use. The risk involved in the study includes the risk caused by adverse selection, investment risk, and interest rate risk. It also compares the risk-taking attitude among insurers with different ownership statuses. The first chapter studies competitive equilibria of an insurance market with adverse selection where insurers\u27 investments are risky. It characterizes the incentive-efficient allocations of the economy. Competitive equilibria are not incentive-efficient because of the externality imposed by agents\u27 incentive constraints that cannot be completely internalized in the Walrasian economy. Specifically, the equilibrium allocations achieved in the market can only be ones with restricted subsidization although incentive-efficient allocations feature unrestricted subsidization when the proportion of low-risk insurees is large. Finally, it demonstrates incentive-efficient allocations in the new economy with investment risk can be successfully decentralized in the Walrasian market affiliated with consumption rights that internalize the externality imposed by agents\u27 incentive constraints. The second chapter studies duration-matching behavior by life insurers in response to interest rate movements. Previous literature finds evidence that the duration gap between assets and liabilities is negatively correlated to interest rates, which is interpreted as ex post duration adjustment. It further hypothesizes that value-maximizing life insurers have incentives to make pre-emptive matching in anticipation of future interest rates. It uses the term spread of the yield curve as the indicator of the expected change in interest rates and shows that U.S. life insurers actively shorten the durations of their asset portfolios reacting to an increasing in both the interest rate level and expected future interest rates proxized by the term spread. To identify the causal relation, it exploits the monetary policy shock associated with 2013 taper tantrum in the difference-in-differences analysis. Consistent with the hypotheses, there is a negative impact of the tape tantrum on the asset duration of highly exposed life insurers comparing with insurers with low interest rate risk exposure. The last chapter is derived from the study about duration matching behaviors. It investigates the role that the ownership status of life insurers plays in the attitude of risk-taking. Mutual ownership is of interest because of the dramatic evolution of the mutual market and its large market share. Following previous studies of capital advantage in different ownership types, the paper suggests that mutual insurers are more conservative in taking interest rate risk relative to stock insurers. Evidence from the U.S. life insurance industry shows that U.S. life insurers maintain a smaller duration gap and react more intensively to interest rate risk. After considering different corporate structures, the argument remains consistent in that mutual corporations take less interest rate risk than two types of stock corporations, mutual holding corporations, and stock corporations

Task-oriented Dialogue System for Automatic Disease Diagnosis via Hierarchical Reinforcement Learning

In this paper, we focus on automatic disease diagnosis with reinforcement learning (RL) methods in task-oriented dialogues setting. Different from conventional RL tasks, the action space for disease diagnosis (i.e., symptoms) is inevitably large, especially when the number of diseases increases. However, existing approaches to this problem employ a flat RL policy, which typically works well in simple tasks but has significant challenges in complex scenarios like disease diagnosis. Towards this end, we propose to integrate a hierarchical policy of two levels into the dialogue policy learning. The high level policy consists of a model named master that is responsible for triggering a model in low level, the low level policy consists of several symptom checkers and a disease classifier. Experimental results on both self-constructed real-world and synthetic datasets demonstrate that our hierarchical framework achieves higher accuracy in disease diagnosis compared with existing systems. Besides, the datasets (http://www.sdspeople.fudan.edu.cn/zywei/data/Fudan-Medical-Dialogue2.0) and codes (https://github.com/nnbay/MeicalChatbot-HRL) are all available now

Design and implementation of a low-power low-cost digital current-sink electronic load ‡

Electronic load (e-load) is essential equipment for power converter performance test, where a designated load profile is executed. Electronic load is usually implemented with the analog controller for fast tracking of the load profile reference. In this paper, a low-power low-cost electronic load is proposed. MOSFETs (metal-oxide-semiconductor field-effect transistors) are used as the power consumption devices, which are regulated to the active region as controlled current-sink. In order to achieve fast transient response using the low-cost digital signal controller (DSC) PWM peripherals, the interleaving PWM method is proposed to achieve active current ripple mitigation. To obtain the system open-loop gain for current-sink operation, an offline digital system identification method, followed by model reduction, is proposed by applying Pseudo-Random Binary Sequence (PRBS) excitation. Pole-zero cancelation method is used in the control system design and later implemented in a DSC. The prototype is built and tested, in which meaningful testing scenarios under constant current-sink mode, pulse current sink mode, and double line-frequency current mode are verified. The experimental results indicate that the proposed e-load can sink pre-programmed current profile with well-attenuated ripple for static and dynamic load testing, and is applicable to fully digitalized power testing equipment

2D Materials Graphene related materials for thermal management Graphene related materials for thermal management

International audienceAlmost 15 years have gone ever since the discovery of graphene as a single atom layer. Numerous papers have been published to demonstrate its high electron mobility, excellent thermal and mechanical as well as optical properties. We have recently seen more and more applications towards using graphene in commercial products. This paper is an attempt to review and summarize the current status of the research of the thermal properties of graphene and other 2D based materials including the manufacturing and characterization techniques and their applications, especially in electronics and power modules. It is obvious from the review that graphene has penetrated the market and gets more and more applications in commercial electronics thermal management context. In the paper, we also made a critical analysis of how mature the manufacturing processes are; what are the accuracies and challenges with the various characterization techniques and what are the remaining questions and issues left before we see further more applications in this exciting and fascinating field. TOPICAL REVIE

Photoredox-catalyzed reaction as a powerful tool for rapid natural product Gem -dimethylation modification: discovery of potent anti-cancer agents with improved druggability

Tylophorine has diverse biological activities; however, the stability, solubility, and central nervous system toxicity have severely limited use of tylophorine. The gem -dimethyl group is an organic chemistry functional group that consists of two methyl groups bonded to the same carbon atom. This feature has gained significant attention in medicinal chemistry due to its unique properties and potential applications in drug design. We applied a new photoredox methodology to tylophorine modification, resulting in a series of gem-dimethyl tylophorine analogues. Among the analogues, compound 4b demonstrated promising activity against a wide range of tumor cell lines and exhibited significantly improved drug-like properties, including enhanced solubility and stability. Compound 4b showed an exceptional inhibitory effect (7.8 nM) against a C481S mutation-induced ibrutinib-resistant non-Hodgkin’s lymphoma cell line, as well as primary tumor cell lines obtained from patients. Importantly, compound 4b exhibited significantly reduced anti-proliferative activity against the normal cell line tested, indicating the potential for an enhanced therapeutic window for compound 4b . Based on these early-stage data, we believe that our study provides a solid foundation for the development of new therapeutic agents for potential drug-resistant cancer treatment in the near future

Wall effects on a rotating sphere

The flow induced by a spherical particle spinning in the presence of no-slip planar boundaries is studied by numerical means. In addition to the reference case of an infinite fluid, the situations considered include a sphere rotating near one or two infinite plane walls parallel or perpendicular to the axis of rotation and a sphere centred within a cube. The hydrodynamic force and couple acting on the sphere exhibit a complex behaviour under the sometimes competing, sometimes cooperating action of viscous, inertial and centrifugal effects

Eliminating the Influence of Axle Parameters in Influence Line Identification

Accurate and rapid acquisition of the strain influence line of continuous beam plays a positive role in promoting the wide application of structural health monitoring. The structural response obtained from the sensors is used to estimate the strain influence line. However, most estimation methods ignore the influence of axle parameters on the structural response, resulting in a large error in identifying the strain influence line. This paper presents a method for eliminating the influence of axle parameters of moving vehicles on strain responses to estimate the strain influence line of continuous beams based on the long-gauge strain sensing technology. By analysing the mechanical characteristics of the multi-span continuous beam, a theoretical strain influence line expression is first established to obtain the strain influence line of the continuous beam accurately. The structural response only caused by axle weight, obtained by eliminating the influence of axle parameters, is then estimated for calibrating the theoretical strain influence line. Finally, different lane tests are also considered to solve the influence of different transverse position relations on the proposed method between the monitoring unit and the lane. Finally, numerical simulations are adopted to illustrate the effectiveness of the proposed identification method by simulating the strain time histories induced by a multi-axle vehicle. A field test also demonstrates the validity and feasibility of this method