Browsing by Subject "Numerical model"

Now showing 1 - 10 of 10

Open Access
Asymmetric effects of monetary policy shocks on economic performance: empirical evidence from Turkey
(Routledge, 2016) Ülke, V.; Berument, Hakan
This study investigates the asymmetric effects of monetary policy shocks on the macroeconomic variables of exchange rate, output and inflation for an emerging economy ‒ Turkey ‒ by using monthly data between 1990 and 2014. We employ the innovative nonlinear vector autoregressive model of Kilian and Vigfusson (2011), which allows us to observe the effect of different stances (tight or loose) and different sizes (small or large) of monetary policy actions. Our empirical evidence reveals that tight monetary policy, which, in this case, is captured with a positive shock to interest rate, decreases exchange rate, output and prices, as economic theory suggests. Loose monetary policy, which is captured with a negative shock to interest rate, has the opposite effect on these variables. However, the effects of loose monetary policy are weaker than the effects of tight monetary policy because loose monetary policy shocks are less effective than tight monetary policy shocks. Moreover, as the magnitude of a shock increases, the difference between the effects of tight and loose monetary policy policies also increases. © 2015 Taylor & Francis.
Open Access
Debris removal during disaster response: a case for Turkey
(Elsevier, 2016) Sahin, H.; Kara, B. Y.; Karasan, O. E.
Debris occurs from the ruin and wreckage of structures during a disaster. Proper removal of debris is of great importance because it blocks roads and prohibits emergency aid teams from accessing disaster-affected regions. Poor disaster management, lack of efficiency and delays in debris removal cause disruptions in providing shelter, nutrition, healthcare and communication services to disaster victims, and more importantly, result in loss of lives. Due to the importance of systematic and efficient debris removal from the perspectives of improving disaster victims quality of life and allowing the transportation of emergency relief materials, the focus of this study is on providing emergency relief supplies to disaster-affected regions as soon as possible by unblocking roads through removing the accumulated debris. We develop a mathematical model for the problem that requires long CPU times for large instances. Since it is crucial to act quickly in an emergency case, we also propose a heuristic methodology that solves instances with an average gap of 1% and optimum ratio of 80.83%.
Open Access
Detection of compound structures using a gaussian mixture model with spectral and spatial constraints
(Institute of Electrical and Electronics Engineers Inc., 2014) Arı, C.; Aksoy, S.
Increasing spectral and spatial resolution of new-generation remotely sensed images necessitate the joint use of both types of information for detection and classification tasks. This paper describes a new approach for detecting heterogeneous compound structures such as different types of residential, agricultural, commercial, and industrial areas that are comprised of spatial arrangements of primitive objects such as buildings, roads, and trees. The proposed approach uses Gaussian mixture models (GMMs), in which the individual Gaussian components model the spectral and shape characteristics of the individual primitives and an associated layout model is used to model their spatial arrangements. We propose a novel expectation-maximization (EM) algorithm that solves the detection problem using constrained optimization. The input is an example structure of interest that is used to estimate a reference GMM and construct spectral and spatial constraints. Then, the EM algorithm fits a new GMM to the target image data so that the pixels with high likelihoods of being similar to the Gaussian object models while satisfying the spatial layout constraints are identified without any requirement for region segmentation. Experiments using WorldView-2 images show that the proposed method can detect high-level structures that cannot be modeled using traditional techniques. © 1980-2012 IEEE.
Open Access
The development problem under embodiment
(Wiley-Blackwell Publishing Ltd., 2006) Boucekkine, R.; Martínez, B.; Saglam, C.
This paper studies technology adoption in an optimal growth model with embodied technical change. The economy consists of the final good sector, the capital sector, and the technology sector which role is the imitation of exogenous innovations. Scarce labor resources are allocated to the technology and final good sectors. The final good is allocated to consumption and to the capital sector. The authors analytically characterize the long run optimal allocations. Using a calibrated version of the model, they find that an acceleration in the rate of embodied technical change should not be responded by an immediate and strong adoption effort. Instead, adoption labor should decrease in the short run, and the optimal technological gap is shown to increase either in the short or in the long run. The state of the institutions and policies around the technology sector is key in the design of the optimal adoption timing. © 2006 The Authors; Journal compilation © 2006 Blackwell Publishing Ltd.
Open Access
Effects of laser ablated silver nanoparticles on Lemna minor
(Elsevier, 2014) Üçüncü, E.; Özkan, A. D.; Kurşungöz, C.; Ülger, Z. E.; Ölmez, T. T.; Tekinay, T.; Ortaç, B.; Tunca E.
Open Access
Hub Location Problem with Allowed Routing between Nonhub Nodes
(Wiley-Blackwell, 2015) Mahmutoğulları, A. I.; Kara, B. Y.
In this study, we relax one of the general assumptions in the hub location literature by allowing routed flows between nonhub nodes. In hub networks, different flows are consolidated and routed via collection, interhub, and distribution arcs. Due to consolidation, some flows travel long paths despite closeness of their origin and destination. In this study, we allow direct flows by penalizing by a scalar factor of original cost of transshipment between these arcs. We present mathematical models for median, center, and set covering versions of the problem for single- and multi-allocation cases. We test the models with the CAB and TR data sets. We discuss the properties of established direct connections for different models by using another mathematical model where the number of direct flows is bounded and interpret the effect of changes in problem parameters.
Open Access
In the presence of climate change, the use of fertilizers and the effect of income on agricultural emissions
(M D P I AG, 2017) Erbas, B. C.; Solakoglu, E. G.
This study looks into the factual link between nitrogen fertilizer use and the land annual mean temperature anomalies arising from climate change, incorporating the effect of income and agriculture share to understand better their impact on emissions from agricultural activities along climate indicators. The study unearths causalities associated with this link by employing the Vector Error Correction Model (VECM) with back-dated actual panel data specifically constructed for this study by combining four datasets from 2002 to 2010. In the long-run, the causality is significant and unidirectional, indicating that income, agriculture share, and land temperature anomalies cause agricultural emissions, and that disequilibrium from such emissions is not eliminated within a year. In the short-run, the effective use of nitrogen fertilizers and other associated agricultural practices can be achieved as countries approach per capita income of 7000 USD. Changes in the structure of economies have an expected effect on agricultural emissions. Temperature anomalies increase agricultural emissions from nitrogen fertilizers, possibly due to the fact that the potential negative impacts of these anomalies are mitigated by farmers through changes in crop production inputs. Therefore, as part of adoption strategies, to avoid the excessive and inefficient use of nitrogen fertilizers by farmers, economic incentives should be aligned with the national and global incentives of sustainability. © 2017 by the authors.
Open Access
Numerical study on the dispersion and deposition of particles in evaporating sessile droplets
(2022-09) Erdem, Ali Kerem
Evaporating sessile droplets including dispersed particles are utilized in the coating, printing, and biomedical applications. Modeling this problem is a challenging process, therefore diﬀerent assumptions are used in the literature. It is important to have a model which covers both pinned and moving contact line regimes for the droplet, thus whole evaporation process and deposition proﬁle can be understood. Therefore, in this work, a numerical and mathematical model is derived to simulate two-dimensional symmetric thin evaporating sessile droplets whose contact line is ﬁrstly pinned and then moving. This model is derived by combining diﬀerent models in literature with the help of lubrication theory and rapid vertical diﬀusion assumption. This model includes a temporal change in the droplet’s surface height, contact line dynamics, particle dispersion, and deposition. The ﬁnite diﬀerence method is used in the numerical solution. Cases including pinned and moving contact lines in the literature are solved separately by diﬀerent numerical algorithms developed in this work and these algorithms were combined. This new algorithm ﬁrst solves a mathematical model in the pinned contact line regime. When the contact angle goes below the deﬁned limit, the second part of the algorithm solves the mathematical model in the moving contact line regime until 95 percent of the total particle mass is deposited. A parametric study has been done with the developed algorithm. A set of parameters is deﬁned and chosen parameters are changed to see their eﬀects. It is observed that increasing the Marangoni number and Capillary number, increased particle accumulation near the center. Decreasing evaporation number and increasing Damkohler number result in more uniform particle deposition.
Open Access
Outsourcing and wage inequality in a dynamic product cycle model
(Wiley-Blackwell Publishing Ltd., 2006) Sayek, S.; Şener, F.
This paper constructs a dynamic North-South trade model with outsourcing and endogenous innovation. Production of high quality goods is first performed in the North (Northern phase), then split between the North and the South (Outsourcing phase), and finally shifted to the South (Southern phase). This cycle is reignited whenever a Northern firm innovates a higher quality product. We find that an increase in the fraction of outsourced production raises the Northern skill premium unambiguously, while raising the Southern skill premium if and only if the skill intensity of outsourced production is higher than that of local Southern production. © 2006 The Authors; Journal compilation © 2006 Blackwell Publishing Ltd.
Open Access
Strategic interaction and catching up
(Wiley-Blackwell Publishing, 2016) Özer, M.; Sağlam, Ç.
In this study, we prove that the strategic interaction among agents differing in initial wealth levels leads the poor to be able to catch up with the rich, which is not the case for the standard Ramsey model where the initial wealth differences perpetuate. Extending the analysis to account for relative wealth concern and the adjustment cost of consumption, the strategic interaction among agents is shown to affect not only the distribution of wealth in the long run but also the transitional dynamics substantially. In particular, we show that structurally very simple frameworks may lead to limit cycles thanks to the strategic interaction among agents in the economy. © 2015 Board of Trustees of the Bulletin of Economic Research and John Wiley & Sons Ltd.