Parallel LQP alternating direction method for solving variational inequality problems with separable structure

In this paper, we propose a logarithmic-quadratic proximal alternating direction method for structured variational inequalities. The predictor is obtained by solving series of related systems of nonlinear equations, and the new iterate is obtained by a convex combination of the previous point and the one generated by a projection-type method along a new descent direction. Global convergence of the new method is proved under certain assumptions. Preliminary numerical experiments are included to verify the theoretical assertions of the proposed method.Qatar University Start-Up Grant: QUSG-CAS-DMSP-13/14-8.Scopu

Research on closed-loop supply chain network equilibrium with two-type suppliers, risk-averse manufacturers and capacity constraints

Purpose: the aim of this paper is to investigate the closed-loop supply chain (CLSC) network equilibrium wiht the consideration of three practical factors: two complementary types of suppliers, risk-averse character of the manufacturer and capacity constraints of the suppliers. Design/methodology/approach: The equilibrium of various decision makers including the suppliers, the manufacturers, the retailers, the collectors and the demand markets are modeled via finite-dimensional variational inequality, respectively. Then the governing CLSC network equilibrium model is established. The logarithmic-quadratic proximal prediction-correction algorithm is designed to solve the variational inequality model. Numerical examples are given to analyze the impact of return rate, risk-averse degree and capacity constraints on the network equilibrium under different product BOMs. Findings: with the increase of return rate, the profits of various channel members and the performance of the CLSC system will improve. There is a contradiction between profit maximization and risk minimization for the manufacturers. Moreover, the economic behavior of the CLSC is likely to be limited by the capacity constraints of the suppliers. Originality/value: Prior to this paper, few papers have addressed with the CLSC network equilibrium considering some practical factors. They assume all the suppliers are identical and all the decision-makers are risk neutral. Furthermore, the production capacities of all suppliers are assumed to be infinite or large enough. To fill the gap, this paper examines the influences of two-type suppliers, risk aversion and capacity constraints upon the CLSC network equilibrium.Peer Reviewe

Analysis of the supply chain design and planning issues: Models and algorithms

Ph.DDOCTOR OF PHILOSOPH

Aircraft load alleviation by specifying its closed-loop eigenstructure

Reduction of aircraft loads, arising as a result of manoeuvre commands or atmospheric turbulence, by means of active control is an important problem in flight control. A variety of methods of designing appropriate control systems to achieve such reduction are available, but not every method is effective. A feature of this research work is the use of an eigenvalue/eigenvector assignment method using full state variable feedback, to design aircraft load alleviation control systems. [Continues.

Grid integration of variable renewable energies in Ghana: assessment of the impact on system stability

This research analyses the impact of renewable energies (RE) generation in Ghana’s national interconnected transmission system (NITS) and how its stability is affected. Integrating RE, particularly solar and wind in Ghana’s power system has been discussed at the national level with the intention to diversify the energy mix and reduce the dependency on thermal energy. RE integration introduces operational and infrastructural challenges in Ghana’s network, to which novel measures are required. Using the DIgSILENT PowerFactory simulation tool and MATLAB, simulation scenarios are created to capture diverse network conditions including different RE penetration levels, load demand and infrastructural expansion for three separate years. The ‘optimum’ penetration level of RE in the NITS considering voltage and loading limits is also identified using optimization techniques. The simulation results show that the target scenario is the most prone to both static and dynamic voltage instability. The transient stability analysis however reveals the post-target scenario to be unstable. Furthermore, methods of optimization are used to determine the reactive power deficient nodes in the NITS, which serve as the basis for the stability enhancement measures. The simulations and analysis additionally indicate that implementing the proposed measures indeed enhances the stability of the NITS. Finally, this research shows that RE integration is ‘technically’ feasible in Ghana if the required network reinforcements and operational changes are accordingly considered