Max-npv project scheduling problems with cash flow balance constraints

The Max-npv project scheduling problem with cash flow balance constraints is identified at first. Its characteristics different from the classical resource-constrained Max-npv project scheduling problem are analyzed and the basic assumptions of the study are summed up. Then a nonlinear integer-programming model of the problem is constructed. Through the cash flow balance constraints in the model, activity expenses, progress payments, and financing cost are connected together and cash outflows and cash inflows in the project may be kept balanced. Because of the combinatorial attribute owned by the model, a simulated annealing heuristic is developed. The heuristic is tested on a data set consisting of 29160 standard instances generated by ProGen. The outcome shows that the heuristic can solve all instances with an average time of 8.90 seconds, the mean relative deviation and variance parameter of the solutions are 9.79% and 0.0024 respectively. Ultimately, an illustrative example is solved by the heuristic and the influences of the key parameters on the project NPV are analyzed. Based on the results obtained, the following conclusions can be drawn: the project NPV has a negative linear correlation with the financing cost rate and the deposit rate of quality security, a positive linear correlation with the payment proportion and the advance payment proportion, and a negative exponential correlation with the quality security period and the discount rate of cash flows.