Browsing by Subject "Optimality"

Now showing 1 - 6 of 6

Open Access
Discrete time/cost trade-off problem: a decomposition-based solution algorithm for the budget version
(Pergamon Press, 2010-04) Hazır, O.; Haouari, M.; Erel, E.
This paper investigates the budget variant of the discrete time/cost trade-off problem (DTCTP). This multi-mode project scheduling problem requires assigning modes to the activities of a project so that the total completion time is minimized and the budget and the precedence constraints are satisfied. This problem is often encountered in practice as timely completion of the projects without exceeding the budget is crucial. The contribution of this paper to the literatures is to describe an effective Benders Decomposition-based exact algorithm to solve the DTCTP instances of realistic sizes. Although Benders Decomposition often exhibits a very slow convergence, we have included several algorithmic features to enhance the performance of the proposed tailored approach. Computational results attest to the efficacy of the proposed algorithm, which can solve large-scale instances to optimality.
Open Access
Energy saving technological progress in overlapping generations economies with renewable and non-renewable resources
(Bilgesel Yayıncılık San. ve Tic. Ltd., 2012) Fazlıoğlu, B. A.; Sağlam, H. Ç.
We study the effects of energy saving technological progress and substitution of renewable energy resources with non-renewable resources on natural resource depletion and long run growth. We develop a growth model in two-period overlapping generations framework incorporating the presence of both renewable and non-renewable energy resources and resource augmenting technological progress. We provide an analytical characterization of the balanced growth path and analyze the conditions for the economy to exhibit positive long run growth. Then, we investigate the effects of discount factor, resource augmenting technological progress and intensity of resources in energy production on the depletion rate. We also examine whether the long run growth is sustainable or optimal. Our main finding is that the effect of an increase in the intensity of the renewable resources in producing energy on long run growth is positive. In addition although exhaustible resources are essential in production the economy can be sustained and the balanced growth path is optimal.
Open Access
Four essays on overlapping generations resource economies : optimality, sustainability and dynamics
(2012) Fazlıoğlu, Burcu
This dissertation is made up of four essays on overlapping generations resource economies. The Örst essay studies the e§ects of energy saving technological progress and substitution of renewable energy resources with non-renewable resources on natural resource depletion and long run growth. A growth model in two-period overlapping generations framework incorporating the presence of both resources and resource augmenting technological progress is developed. The e§ect of an increase in the intensity of the renewable resources in producing energy on long run growth is found to be positive. Although exhaustible resources are essential in production the economy can be sustained and the balanced growth path is optimal. In the second essay, the implications of assuming di§erent energy intensities for physical capital accumulation and the Önal good production is studied in an overlapping generations resource economy where energy is obtained from the extraction of the natural resources. Apart from the standard literature, physical capital accumulation is assumed to be relatively more energy-intensive than consumption. Multiple steady states, indeterminacy and bifurcations are obtained, without taking non-linearizing assumptions evident in the literature. For the non-renewable resources if the share of energy resources is low enough, local indeterminacy and hopf bifurcations may arise in the model. The aim of third essay is to analyze can costly resource extraction and di§erentiating energy intensities induce dynamics other than saddles in an overlapping generations resource economy. The capital accumulation sector is assumed to be more energy intensive. The energy input is extracted from the natural resources with some extraction costs. The main Önding of the essay is that both naturally evident assumptions contribute to the richness of the dynamics. Depending on the share of resources in capital accumulation dynamics other than saddle ñindeterminacy, áip and hopf bifurcationsñ can arise in the model for the non-zero steady state. In the fourth essay, a feedback mechanism between population and natural resource to a standard model of renewable resource based OLG economy is incorporated to check the stability of the dynamics. Multiple steady states and indeterminacy have been obtained even in the absence of logistic regeneration and independent of intertemporal elasticity of substitution. In particular, transcritical bifurcations may arise in the model varying the rate of constant regeneration with respect to population growth rate.
Open Access
On the optimality of stochastic signaling under an average power constraint
(IEEE, 2010-09-10) Göken, Çağrı; Gezici, Sinan; Arıkan, Orhan
In this paper, stochastic signaling is studied for scalar valued binary communications systems over additive noise channels in the presence of an average power constraint. For a given decision rule at the receiver, the effects of using stochastic signals for each symbol instead of conventional deterministic signals are investigated. First, sufficient conditions are derived to determine the cases in which stochastic signaling can or cannot outperform the conventional signaling. Then, statistical characterization of the optimal signals is provided and it is obtained that an optimal stochastic signal can be represented by a randomization of at most two different signal levels for each symbol. In addition, via global optimization techniques, the solution of the generic optimal stochastic signaling problem is obtained, and theoretical results are investigated via numerical examples. ©2010 IEEE.
Open Access
On the optimality of the window method in computational homogenization
(2013) Temizer, I.; Wu, T.; Wriggers, P.
The window method, where the microstructural sample is embedded into a frame of a homogeneous material, offers an alternative to classical boundary conditions in computational homogenization. Experience with the window method, which is essentially the self-consistent scheme but with a finite surrounding medium instead of an infinite one, indicates that it delivers faster convergence of the macroscopic response with respect to boundary conditions of pure essential or natural type as the microstructural sample size is increased to ensure statistical representativeness. In this work, the variational background for this observed optimal convergence behavior of the homogenization results with the window method is provided and the method is compared with periodic boundary conditions that it closely resembles. © 2013 Elsevier Ltd. All rights reserved.
Open Access
Optimizing foreign exchange reserves: Protection against external shocks in Ghana
(Frontiers Media S.A., 2022-11-02) Abdul-Rahaman, Abdul-Rashid; Hongxing, Yao; Alhassan Alolo Akeji, Abdul-Rasheed; Ayamba, Emmanuel Caesar; Bernard Pea-Assounga, Jean Baptiste; Alhassan, Mohammed Kamil
Using Least Square Residual Minimization techniques, this paper develops an optimal reserve model, known as the OPREM model, which is essential in optimizing the costs of reserve holding. The paper also sets-out to test and compare the relative predictions of economic trends of the OPREM model as well as the predictions of alternative models in literature. Establishing the predictive accuracy of economic trends of these models are crucial for the gradual and cost-effective accumulation of reserves. The research concludes that, the decision to optimize the cost of reserves under a stable currency environment is reliant on the gold impact factor and not on inflation or interest rates. We also found on further analysis of the OPREM that the OPREM model is better positioned to eliminate the procyclicality and perverse rush in reserve build-ups experienced in developing and emerging countries by effectively setting the reserve stock against economic trends. The research fixes the optimal reserves around a benchmark of 0.7–1.2 of previous year's optimal value. However, in the absence of past optimal values, a benchmark between 2 and 6 times of average inflows for short-term analysis or analysis with small data observations. However, for long-term analysis or analysis with large data frequency (i.e., exceeding 13 data observations), the reserve stock should be fixed on a benchmark of 2–9 times of the average inflows. Copyright © 2022 Abdul-Rahaman, Hongxing, Alhassan Alolo Akeji, Ayamba, Bernard Pea-Assounga and Alhassan.