Browsing by Subject "Growth"
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Item Open Access Ab initio temperature dependent studies of the homoepitaxial growth on Si(0 0 1) surface(2001) Dağ, S.; Çıracı, Salim; Kılıç, Ç.; Fong, C. Y.We performed ab initio zero temperature and finite temperature molecular dynamics calculations to investigate the homoepitaxial growth on the Si(0 0 1) surface. How do the deposited atoms (adatoms) form addimers and how do the addimers reach their favorable positions at the nucleation site of the growth process are presented. Once two epitaxial addimers, one over the dimer row and oriented perpendicular to the surface dimer bonds and the other over the adjacent trough, are aligned at high temperature, the nucleation site of the growth process is formed. The concerted bond exchange between these addimers and the reconstructed surface dimers is found to be the atomistic mechanism that leads to the homoepitaxial growth. © 2001 Elsevier Science B.V.Item Open Access Bank regulation and supervision and its welfare implications(Elsevier BV, 2012-03) Kilinc, M.; Neyapti, B.This study provides a general equilibrium model to explore the welfare implications of bank regulation and supervision (RS). The model supports the basic expectations regarding the positive effects of RS on the growth rate, output, credit, investment, wages and profits; and its negative effects on the interest rate. In addition, RS is observed to lead to a convergence effect. Furthermore, it is observed that the decision of banks to monitor and charge differentiated interest rates to firms depends on the distribution of firm-specific moral hazard rates; bank monitoring increases profits as the distribution of producer type improves. (C) 2011 Elsevier B.V. All rights reserved.Item Open Access The comparative performance of the public enterprise sector in Turkey: a Malmquist productivity index approach(Academic Press, 1997) Zaim, O.; Taskin, F.The public enterprise sector in Turkey has grown appreciably since the 1950's and has made a marked impact on aggregate production, employment, and saving. However, since the early 1980's, public enterprises have been accused of absorbing the government's financial resources and are being held responsible for Turkey's large external debt. The purpose of this study is to compare the performance of the public sector with that of the private sector for the various subsectors of manufacturing in Turkey. The Malmquist productivity index, constructed using nonparametric linear programming methods, is employed for the relevant comparisons. (C) 1997 Academic Press.Item Open Access Comparison of fully three-dimensional optical, normally conducting, and superconducting interconnections(Optical Society of America, 1999-12-10) Özaktaş, Haldun M.; Erden, M. F.Several approaches to three-dimensional integration of conventional electronic circuits have been pursued recently. To determine whether the advantages of optical interconnections are negated by these advances, we compare the limitations of fully three-dimensional systems interconnected with optical, normally conducting, repeatered normally conducting, and superconducting interconnections by showing how system-level parameters such as signal delay, bandwidth, and number of computing elements are related. In particular, we show that the duty ratio of pulses transmitted on terminated transmission lines is an important optimization parameter that can be used to trade off signal delay and bandwidth so as to optimize applicable measures of performance or cost, such as minimum message delay in parallel computation.Item Open Access Continuously tunable emission in inverted type ‐ I CdS/CdSe core/crown semiconductor nanoplatelets(Wiley, 2015-07-15) Delikanlı, S.; Güzeltürk, B.; Hernandez - Martinez, P. L.; Erdem, T.; Keleştemur, Y.; Olutas M.; Akgül, M. Z.; Demir, Hilmi VolkanThe synthesis and unique tunable optical properties of core/crown nanoplatelets having an inverted Type-I heterostructure are presented. Here, colloidal 2D CdS/CdSe heteronanoplatelets are grown with thickness of four monolayers using seed-mediated method. In this work, it is shown that the emission peak of the resulting CdS/CdSe heteronanoplatelets can be continuously spectrally tuned between the peak emission wavelengths of the core only CdS nanoplatelets (421 nm) and CdSe nanoplatelets (515 nm) having the same vertical thickness. In these inverted Type-I nanoplatelets, the unique continuous tunable emission is enabled by adjusting the lateral width of the CdSe crown, having a narrower bandgap, around the core CdS nanoplatelet, having a wider bandgap, as a result of the controlled lateral quantum confinement in the crown region additional to the pure vertical confinement. As a proof-of-concept demonstration, a white light generation is shown by using color conversion with these CdS/CdSe heteronanoplatelets having finely tuned thin crowns, resulting in a color rendering index of 80. The robust control of the electronic structure in such inverted Type-I heteronanoplatelets achieved by tailoring the lateral extent of the crown coating around the core template presents a new enabling pathway for bandgap engineering in solution-processed quantum wells.Item Open Access Corruption and economic development in energy-rich economies(Palgrave Macmillan Ltd., 2009) Kalyuzhnova, Y.; Kutan, A. M.; Yiğit, TanerWe empirically model the causes of corruption and test the economic development-corruption link in energy-rich economies, using data from 48 countries with energy resources. The results indicate that energy abundance may not necessarily hurt economic development in energy-rich countries, allowing enterprises to conduct business more effectively to reduce corruption, establishing a better political (democratic) regime improves corruption rankings, and finally while corruption reduces both the level of GDP per capita and its growth rate, economic development decreases corruption.Item Open Access Effect of egg storage duration and brooding temperatures on chick growth, intestine morphology and nutrient transporters(Cambridge University Press, 2017-10) Yalcin, S.; Gursel, I.; Bilgen, G.; Horuluoglu, B. H.; Gucluer, G.; Izzetoglu, G. T.The effects of egg storage duration (ESD) and brooding temperature (BT) on BW, intestine development and nutrient transporters of broiler chicks were investigated. A total of 396 chicks obtained from eggs stored at 18°C for 3 days (ESD3-18°C) or at 14°C for 14 days (ESD14-14°C) before incubation were exposed to three BTs. Temperatures were initially set at 32°C, 34°C and 30°C for control (BT-Cont), high (BT-High) and low (BT-Low) BTs, respectively. Brooding temperatures were decreased by 2°C each at days 2, 7, 14 and 21. Body weight was measured at the day of hatch, 2, 7, 14, 21, 28 and 42. Cloacal temperatures of broilers were recorded from 1 to 14 days. Intestinal morphology and gene expression levels of H+-dependent peptide transporter (PepT1) and Na-dependent glucose (SGLT1) were evaluated on the day of hatch and 14. Cloacal temperatures of chicks were affected by BTs from days 1 to 8, being the lowest for BT-Low chicks. BT-High resulted in the heaviest BWs at 7 days, especially for ESD14-14°C chicks. This result was consistent with longer villus and larger villus area of ESD14-14°C chicks at BT-High conditions. From 14 days to slaughter age, BT had no effect on broiler weight. ESD3-18°C chicks were heavier than ESD14-14°C chicks up to 28 days. The PepT1 and SGLT1 expression levels were significantly higher in ESD3-18°C chicks than ESD14-14°C on the day of hatch. There was significant egg storage by BT interaction for PepT1 and SGLT1 transporters at day 14. ESD14-14°C chicks had significantly higher expression of PepT1 and SGLT1 at BT-Low than those at BT-Cont. ESD14-14°C chicks upregulated PepT1 gene expression 1.15 and 1.57-fold at BT-High and BT-Low, respectively, compared with BT-Cont, whereas PepT1 expression was downregulated 0.67 and 0.62-fold in ESD3-18°C chicks at BT-High and BT-Low. These results indicated that pre-incubation egg storage conditions and BTs affected intestine morphology and PepT1 and SGLT1 nutrient transporters expression in broiler chicks.Item Open Access Empirics of economic growth in Turkey(2016-09) Doğuhan, SündalIn the empirics of growth literature method proposed by Mankiw et al. (1990) has been widely used to test the determinants of economic growth and the speed of convergence. This framework, however, considers technological progress as constant and idencital across countries and/or regions. In this study, I propose a production function that uses electricity as a factor of production to produce output and check the speed of convergence of per capita output. Electricity is regarded to be produced from clean and dirty sources given an elasticity of substitution. Electricity output is weighted by these elasticities in order to see their effect on convergence. Based on the appilication of the system GMM approach contrasted with the Within Group and OLS results, I key out conditional convergence analysis over 2002-2013 based on regional data for Turkey. Econometric results indicate overall convergence of per capita income across regions in general, noting that each development region converges to its own steady state. Results obtained from OLS and Within Group regressions fail to be significant. I have also found out that the non-thermal electricity production has a signiffcantly positive effect on growth rate when GMM method is applied, wheras electricity production by thermal sources has no significant effect on the growth rate. Finally, I have also found that the share of specialized lending in credit demand tends to increase the growth rate.Item Open Access Essays on growth and macroeconomic dynamics(2015-09) Özer, MehmetThis dissertation is composed of four essays on economic growth and macro- economic dynamics. The first essay analyzes how the dynamic strategic in- teractions among agents a¤ect the long-run distribution of wealth in terms of catching up and the transitional dynamics. It is shown that incorporating the strategic behavior among agents leads to the wealth level of the initially poor and the rich households to be the same at the stationary state. Extending the model by incorporating relative wealth concern; the resulting equilibria depends the valuation of relative wealth concern by each individual and it is proved that under some plausible conditions the catching up occurs thanks to the strategic interaction in the form of open-loop. The stability of these two models are carried out for arbitrary number of people in the economy. In the second essay studies the e¤ects of above mentioned strategic interac- tion in Ramsey model with "Easterlin hypothesis". It is shown that strategic interaction among agents in the economy leads to a change not only in the distribution of wealth but also in the transitional dynamics substantially. The obtained complex dynamics is in the form of Hopf bifurcation which is one of the main tool to explain the economic fluctuations. Third essay of this thesis introduces Stone-Geary Preferences with an endoge- nous reference level of consumption in an Ak model in which reference level of consumption is an increasing function of the capital. It is shown that the result- ing equilibrium presents richer dynamics under such a Stone-Geary preferences. It is proved that endogenous reference level leads to global and local indetermi- nacy: economies starting with di¤erent initial conditions does not necessarily converge to the same steady state and also economies starting with the same initial conditions does not necessarily follow the same transition path. The aim of the fourth essay is to analyze the e¤ects of a pure public good that reduces the subsistence level of consumption on the long run equilibrium and the optimal tax rate. It is shown that although the steady state amount of public good is higher for the first best allocation, the subsistence level of consumption is the same with that of the second best equilibrium. On the other hand, the capital stock and the consumption of the private good are higher for the first best equilibria. Another important result of the essay is the "government revenue-tax rate" locus with a dynamic threshold which depends on the total factor productivity (TFP). The optimal amount of tax rate that maximizes the revenue of the government is an increasing function of the TFP and thus revenue maximizing tax rate varies across countries.Item Open Access European integration, productivity growth and real convergence(Elsevier BV, 2007) Kutan, A. M.; Yigit, T. M.This paper derives a stochastic endogenous growth model to investigate the impact of European Union (EU) integration on convergence and productivity growth. The theoretical model implies both temporary and permanent positive effects of the integration process. The empirical part of the analysis uses structural break tests and data envelopment analysis to examine the accession process of five recent members to the EU15. The results show (i) endogenously identified accession dates as structural breaks, (ii) improved rates of productivity growth after accession over and above the Union benchmark level, and (iii) increased pace of overall growth due to capital accumulation as a result of institutional features of the Union such as Structural and Cohesion Funds. These findings support the theoretical model, implying that economic integration is beneficial for member countries, especially from a long-run perspective, and Cohesion and Structural funds help the new members catch up with the core-EU members' standard of living. (c) 2006 Elsevier B.V. All rights reserved.Item Open Access Field-effect-assisted photoconductivity in PbS films deposited on silicon dioxide(American Institute of Physics, 2002-05-01) Pintilie, L.; Pentia, E.; Matei, I.; Pintilie, I.; Özbay, EkmelLead sulfide (PbS) thin films were deposited from a chemical bath onto SiO2/Si (n-type) substrates. Pseudo-metal-oxide-semiconductor devices were obtained by evaporating source and drain gold electrodes on a PbS surface and aluminum gate electrode on a Si substrate. Field-effect-assisted photoconductivity in the PbS layer was investigated at room temperature, in the 800-2700-nm-wavelength domain for different values and polarities of the drain and gate voltages. The best results were obtained for a positive gate, when both semiconductors are in depletion. An enhancement of about 25% of the photoconductive signal is obtained compared with the case when the gate electrode is absent or is not used. A simple model is proposed that explains the behavior of the dark current and photoconductive signal in PbS film with changing the gate voltage. (C) 2002 American Institute of Physics.Item Open Access Finite temperature studies of Te adsorption on Si(0 0 1)(Elsevier, 2002) Sen, P.; Çıracı, Salim; Batra, I. P.; Grein, C. H.; Sivananthan, S.We perform first principles density functional calculations to investigate the adsorption of Te on the Si(0 0 1) surface from low coverage up to a monolayer coverage. At low coverage, a Te atom is adsorbed on top of the Si surface dimer bond. At higher coverages, Te atoms adsorption causes the Si-Si dimer bond to break, lifting the (2 × 1) reconstruction. We find no evidence of the Te-Te dimer bond formation as a possible source of the (2 × 1) reconstruction at a monolayer coverage. Finite temperature ab initio molecular dynamics calculations show that Te covered Si(0 0 1) surfaces do not have any definitive reconstruction. Vibrations of the bridged Te atoms in the strongly anharmonic potentials prevent the reconstruction structure from attaining any permanent, two-dimensional periodic geometry. This explains why experiments attempting to find a definite model for the reconstruction reached conflicting conclusions. © 2002 Elsevier Science B.V. All rights reserved.Item Open Access Free-standing ZnO-CuO composite nanowire array films and their gas sensing properties(IOP Publishing, 2011-07-19) Wang, J. X.; Sun, X. W.; Yang, Y.; Kyaw, A. K. K.; Huang, X. Y.; Yin, J. Z.; Wei, J.; Demir, Hilmi VolkanA modified hydrothermal method was developed to synthesize ZnO-CuO composite nanostructures. A free-standing film made of ZnO-CuO nanostructures was assembled on the surface of the hydrothermal solution with a smooth surface on one side and a spherical surface on the other side. The structure, growth mechanism and the optical properties of the composite nanostructures were studied. Structural characterizations indicate that the composite nanostructure mainly consisted of two single-crystal phases of CuO and ZnO. The sensitivity for CO gas detection was significantly improved for the composite CuO-ZnO nanostructure film. This method offers a possible route for the fabrication of free-standing nanostructure films of different functional composite oxides.Item Open Access Inflation and growth: Positive or negative relationship?(A N S I Network, 2008) Berument, Hakan; Inamlik, A.; Olgun, H.This study has been motivated by two developments. Firstly, by the vast literature on the relationship between inflation and growth which is abundantly endowed with diverse theoretical explanations and contradictory evidence and by the unique experience of the Turkish economy with inflation and growth. A preliminary examination of the Turkish data pointed to a negative relation between inflation and growth. Moreover, there is a unanimous agreement among the students of the Turkish economy that many factors have contributed to inflation in this country. In view of these facts this paper employs a VAR model which will enable us to identify the sources of the shocks and control for external factors. In addition VAR models have a high predictive power and enable the researcher to observe the impulse response functions. The study employs Generalised Impulse Response analysis. In the empirical experiments oil prices, money supply, government spending and taxes have been taken as the most likely determinants of inflation. The study shows that there is a negative relationship between inflation and output growth in Turkey and that the underlying explanatory factor is the real exchange rate. This result is robust. © 2008 Asian Network for Scientific Information.Item Open Access Modeling institutional evolution(2013) Neyapti, B.This paper proposes a formal framework to analyze the process of institutional evolution in relation with economic progress. Institutions have both formal (F) and informal (N) aspects that may exhibit varying processes of change. N is hypothesized to evolve with the level of capital stock, as in learning by doing, whereas F is chosen optimally by a government that maximizes output subject to social and political costs. F and N together define the production technology and affect the income level. Consistent with evidence, simulations of the model's solution reveal that optimum F exhibits a punctuated pattern.Item Open Access Nominal and real stochastic convergence of transition economies(Academic Press, 2004) Kutan, A. M.; Yigit, T. M.To investigate the sensitivity of real and nominal economic convergence of transition economies to model specification and restrictions, we extend the work of Kocenda [J. Compar. Econ. 29 (2001) 1] by considering a more stable, post-1993 period and by adopting a more recent panel estimation approach. This new technique involves less restrictive assumptions than previous panel unit root techniques by allowing heterogeneity in convergence rates. Our results show less nominal and real economic convergence than those of Kocenda.Item Open Access On the effect of N-GaN/P-GaN/N-GaN/P-GaN/N-GaN built-in junctions in the n-GaN layer for InGaN/GaN light-emitting diodes(Optical Society of America, 2014-01-07) Kyaw, Z.; Zhang, Z. H.; Liu, W.; Tan, S. T.; Ju, Z. G.; Zhang, X. L.; Ji, Y.; Hasanov, N.; Zhu, B.; Lu, S.; Zhang, Y.; Sun, X. W.; Demir, Hilmi VolkanN-GaN/P-GaN/N-GaN/P-GaN/N-GaN (NPNPN-GaN) junctions embedded between the n-GaN region and multiple quantum wells (MQWs) are systematically studied both experimentally and theoretically to increase the performance of InGaN/GaN light emitting diodes (LEDs) in this work. In the proposed architecture, each thin P-GaN layer sandwiched in the NPNPN-GaN structure is completely depleted due to the built-in electric field in the NPNPN-GaN junctions, and the ionized acceptors in these P-GaN layers serve as the energy barriers for electrons from the n-GaN region, resulting in a reduced electron over flow and enhanced the current spreading horizontally in the n-GaN region. These lead to increased optical output power and external quantum efficiency (EQE) from the proposed device. (C) 2014 Optical Society of AmericaItem Open Access Risk and return in a dynamic general equilibrium model(Elsevier, 2000) Akdeniz, L.In this paper we examine the relationship between risk and return on productive assets using the intertemporal general equilibrium model of Brock (1982, Asset Prices in a Production Economy, the University of Chicago Press, Chicago, pp. 1-42) as a basis for a simulation study. Current computational techniques are used to solve the growth model of Brock (1979, An Integration of Stochastic Growth and the Theory of Finance - Part I: The Growth Model, Academic Press, New York, pp. 165-192) in order to analyze the underlying financial model. Contrary to recent empirical findings, we find that there is a theoretical basis for the linear relationship between risk and return. This apparent contradiction is due in part to the fact that the dynamic relationship between risk and return depends on the level of output.Item Open Access Role of macroeconomic developments on total factor productivity in the Turkish economy (1972-2003)(2005) Can, RaifIn this thesis, by using regression analysis method, I investigated the role of macroeconomic variables on Total Factor Productivity (TFP) growth in the Turkish economy over the period of 1972-2003. Empirical findings of this study are that instabilities in foreign exchange and real exchange rate appreciation has negative role on TFP growth, on the other hand, growth of export of goods, imports of intermediate goods as a share of GDP, growth of public real infrastructure investments and current account deficit as a share of GDP have positive impacts on TFP growth. Inflation rates, interest rates, public sector borrowing requirement and foreign direct investment inflow insignificant variables to determine TFP growth in the Turkish economy. Also, in this thesis, the Turkish economy is investigated in the context of import-substituting industrialization period, export-led growth period and post-financial liberalization period.Item Open Access Tailoring insoluble nanobelts into soluble anti-UV nanopotpourris(Royal Society of Chemistry, 2011) Wang, J.; Sun, X. W.; Jiao, Z.; Khoo, E.; Lee, P. S.; Ma, J.; Demir, Hilmi VolkanSoluble, transparent and anti-UV nanopotpourris have been prepared by tailoring long nanobelts. The strains and layered structures facilitate the breaking of the as-synthesized nanobelts under an applied mechanical action. The developed tailoring process of nanobelts is a general top-down secondary processing of layered nanostructures at the nanoscale level, which can be expended to the modifications of layered nanowires, nanotubes and hierarchical nanostructures. By tailoring, the size, morphology and solubility are modified, which may open up an area of advanced processing of nanomaterials and hint at some potential applications. Because of the excellent solubility of the tailored nanopotpourris, they are easily dispersed in cosmetics or polymer films, which are quite useful for some anti-UV protection applications, such as anti-UV sunscreen creams and anti-UV window films for vehicles and buildings.