Interest rate is an important macrofactor that affects asset prices in the financial market. As the interest rate in the real market has the property of fluctuation, it might lead to a great bias in asset allocation if we only view the interest rate as a constant in portfolio management. In this paper, we mainly study an optimal investment strategy problem by employing a constant elasticity of variance (CEV) process and stochastic interest rate. The assets of investment for individuals are supposed to be composed of one risk-free asset and one risky asset. The interest rate for risk-free asset is assumed to follow the Cox–Ingersoll–Ross (CIR) process, and the price of risky asset follows the CEV process. The objective is to maximize the expected utility of terminal wealth. By applying the dual method, Legendre transformation, and asymptotic expansion approach, we successfully obtain an asymptotic solution for the optimal investment strategy under constant absolute risk aversion (CARA) utility function. In the end, some numerical examples are provided to support our theoretical results and to illustrate the effect of stochastic interest rates and some other model parameters on the optimal investment strategy.

Purpose – This paper aims to identify key dimensions of brand value co-creation activities and empirically examine the impacts of different dimensions of brand value co-creation upon brand performance among Chinese industrial services firms. Design/methodology/approach – Key dimensions of brand value co-creation activities are identified and a research framework is presented based on qualitative interviews with three industrial services firms. Then, the conceptual model and 14 research hypotheses addressing the impacts of different dimensions of brand value co-creation activities upon brand performance are tested by conducting a questionnaire survey among 258 pairs of Chinese B2B services providers and their client companies. Findings – The research results show that: on the whole, integration of brand value chain and service-dominant logic (SDL) can lead to stronger theoretical explanation about the industrial services brand value and brand performance. In other words, value co-creation activities among multiple stakeholders can help customers perceive brand value in a favorable way and finally improve brand performance; branding process involves eight kinds of value co-creation activities on four interfaces between firm-employees, firm-customers, employees-customers, and firm-other stakeholders, indicating that the cultivation of industrial services brand needs a broader stakeholder perspective; value co-creation activities on the firm-employees interface is original driver of brand development by impacting brand value and brand performance via value co-creation on other interfaces. Originality/value – This paper is the first kind of research that empirically explores the formation mechanism of industrial brand value from the perspective of SDL and also provides insightful implications for managers by pointing out that B2B service providers need to consider the interactive value co-creation behaviors in the social network constructed by different stakeholders in order to improve brand management performance.

According to most countries' norms, and to find the effect of the bridge collision the equivalent static method was designed for bridge-ship collision, ignoring the dynamic effects of shocks. It is sharply different from actual situation. So based on the theory of Winkler foundation, shearing strain theory of Timoshenko and potential energy variation functional principle of Hamilton, the simulation models of bridge piers was built considering the pile-soil interaction. Lateral transient vibration equation of bridge piers was concluded. Based on the theory of integral transform, the differential equation of the collision system and the boundary conditions were transformed with Laplace transformation; the analytical solution of the stress wave in frequency domain was concluded. And then the inversion of solution in frequency domain was carried out using Matlab based on the Crump inverse transformation. Finally the dynamic response law of displacement, normal stress and the shear stress of bridge piers were obtained.

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In this paper, we consider the problem of investment and reinsurance with time delay under the compound Poisson model of two-dimensional dependent claims. Suppose an insurance company controls the claim risk of two kinds of dependent insurance businesses by purchasing proportional reinsurance and invests its wealth in a financial market composed of a risk-free asset and a risk asset. The risk asset price process obeys the geometric Brownian motion. By introducing the capital flow related to the historical performance of the insurer, the wealth process described by stochastic delay differential equation (SDDE) is obtained. The extended HJB equation is obtained by using the stochastic control theory under the framework of game theory. Under the reinsurance expected premium principle, optimal time-consistent investment and reinsurance strategy and the corresponding value function are obtained. Finally, the influence of model parameters on the optimal strategy is explained by numerical analysis.

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<p style='text-indent:20px;'>We study the optimal investment-reinsurance strategies for insurer, who is assumed to be ambiguous about factors related to the stock process and surplus process. In the financial market, the stock and derivatives are traded freely, the optimal investment-reinsurance strategies are obtained under the worst-case scenario with or without derivative trading. We find the evidence that the optimal exposures to different risks of the stock are significantly affected by the ambiguity aversion to the corresponding risk factors. Insurer who ignores model uncertainty always incur welfare losses, which can be proved to be strictly positive. Furthermore, we find that volatility ambiguity has a smaller impact in incomplete markets and surplus process ambiguity has a great impact on reinsurance strategies. Numerical experiments are provided to demonstrate the impact of the optimal exposure and utility loss with different parameters.</p>

The optimal investment problem is a hot field of financial risk control. The analytical solution of investment strategy can be obtained with the power function utility and exponential function utility when the stock price obeys the constant elasticity of variance (CEV) model. However, different investors have different risk preferences; it means that different investors have different utility functions. In this paper, we propose an asymptotic analysis method to obtain the asymptotic solution of investment strategy with the general utility function. The value function is expanded in the form of series, the expressions of the zero-order term and first-order term of the series expansion are derived, respectively, and the error between the asymptotic approximation and the optimal value function is calculated. Finally, the numerical examples provide comparative analysis between the analytical solution and the asymptotic solution to verify the effectiveness of the proposed method.