Browsing by Author "Sahin, A."
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Item Open Access The choice of monetary policy tool(s) and relative price variability: evidence from Turkey(A N S I Network, 2009) Berument, Hakan; Sahin, A.; Saracoglu, B.The aim of this study is to assess any regularity relative price dispersion for the effect of monetary policy tool selection. Central banks use tools such as interbank rate and exchange rate when pursuing their (monetary) policies. The selected tools affect economic variables differently. By using Turkish monthly data for the 1988:2-2008:2 period, this study suggests that pure policies (such as interbank rate only or exchange rate only) increase relative price variability more than mixed policies, where the monetary authorities use the above tools simultaneously. © 2009 Asian Network for Scientific Information.Item Open Access Day of the week effect on foreign exchange market volatility: evidence from Turkey(Elsevier Inc., 2007) Berument, Hakan; Coskun, M. N.; Sahin, A.This paper assesses the day of the week effect of the daily depreciation of the Turkish lira (TL) against the US dollar (USD) and its volatility. The empirical evidence from Turkey presented here suggests that Thursdays are associated with higher and Mondays with lower depreciation rates compared to those of Wednesdays. Moreover, Mondays and Tuesdays are associated with higher volatility than Wednesdays. © 2006 Elsevier B.V. All rights reserved.Item Open Access Design of dynamically adjustable anamorphic fractional Fourier transformer(Elsevier BV * North-Holland, 1997-03-01) Erden, M. F.; Özaktaş, Haldun M.; Sahin, A.; Mendlovic, D.We form optical systems by using only free space portions and cylindrical lenses, and consider these systems as anamorphic fractional Fourier transformers. We dynamically adjust the transform order, scale factor and field curvature of both orthogonal dimensions of anamorphic fractional Fourier transformation by just changing the focal lengths of cylindrical lenses used in the proposed setups. Here, we also consider two approaches for implementing cylindrical lenses with dynamically adjustable focal lengths. There may also be some other methods to obtain cylindrical lenses having adjustable focal lengths which can successfully be used in these proposed setups.Item Open Access Effectiveness of the reserve option mechanism as a macroeconomic prudential tool: evidence from Turkey(Routledge, 2015) Sahin, A.; Dogan, B.; Berument, HakanThis article assesses the effectiveness of a novel macroprudential tool – the reserve option mechanism (ROM) – which Turkey’s central bank developed during the post-2008 period and has employed to control the risk associated with excessive capital flows. We assess how capital flows have affected economic variable changes since the introduction and usage of the ROM. Empirical evidence gathered from Turkey suggests that the tool decreases the effect of capital flow on capital flow (positive shock to capital flow dies out faster or becomes less persistent) and diminishes the effects of capital flow shocks on exchange and interest rates. © 2015 Taylor & Francis.Item Open Access Identfying the liquidity effects of monetary policy shocks for a small open economy: Turkey(Springer New York LLC, 2011) Berument, Hakan; Togay, S.; Sahin, A.This paper proposes a new liquidity measure for a small open economy. The new measure includes the net liquidity provided to the system by a central bank after accounting for the central bank's involvement in the foreign exchange market. Empirical evidence gathered from Turkey suggests that a positive innovation in liquidity increases output temporarily and that its effect on prices, exchange rate and money are permanently higher.Item Open Access Isolated subcutaneous abscess: A rare presentation of extrapulmonary tuberculosis(Lippincott Williams & Wilkins, 2023-08-01) Sahin, A.; Kara-Aksay, A.; Bicmen, C.; Belkaya, Serkan; Kaya, A.; Yilmaz, D.Item Open Access Nonseperable two-dimensional fractional Fourier transform(Optical Society of America, 1998) Sahin, A.; Kutay, M. A.; Özaktaş, Haldun M.Previous generalizations of the fractional Fourier transform to two dimensions assumed separable kernels. We present a nonseparable definition for the two-dimensional fractional Fourier transform that includes the separable definition as a special case. Its digital and optical implementations are presented. The usefulness of the nonseparable transform is justified with an image-restoration example.Item Open Access Optical implementation of the two-dimensional fractional Fourier transform with different orders in the two dimensions(Elsevier BV * North-Holland, 1995-10-15) Sahin, A.; Özaktaş, Haldun M.; Mendlovic, D.Previous optical implementations of the two-dimensional fractional Fourier transform have assumed identical transform orders in both dimensions. We let the orders in the two orthogonal dimensions to be different and present general design formulae for optically implementing such transforms. This design formulae allows us to specify the two orders and the input, output scale parameters simultaneously.Item Open Access Optical implementations of two-dimensional fractional Fourier transforms and linear canonical transforms with arbitrary parameters(Optical Society of America, 1998-04-10) Sahin, A.; Özaktaş, Haldun M.; Mendlovic, D.We provide a general treatment of optical two-dimensional fractional Fourier transforming systems. We not only allow the fractional Fourier transform orders to be specified independently for the two dimensions but also allow the input and output scale parameters and the residual spherical phase factors to be controlled. We further discuss systems that do not allow all these parameters to be controlled at the same time but are simpler and employ a fewer number of lenses. The variety of systems discussed and the design equations provided should be useful in practical applications for which an optical fractional Fourier transforming stage is to be employed.Item Open Access The relative effects of crude oil price and exchange rate on petroleum product prices: evidence from a set of Northern Meditteranean countries(Elsevier, 2014) Berument, Hakan; Sahin, A.; Sahin, S.This paper provides a set of empirical evidence from five Northern Mediterranean countries that are subject to similar refinery reference prices regarding the relative sensitivity of crude oil prices and exchange rate on (pre-tax) petroleum product prices. The empirical evidence reveals that a one percent increase in exchange rate (depreciation) increases petroleum product prices less than a one percent increase in crude oil prices does in the long run. In the short run, however, a one percent increase in exchange rate increases petroleum product prices more than a one percent increase in crude oil prices does. © 2014 Elsevier B.V. All rights reserved.Item Open Access RuO2 supercapacitor enables flexible, safe, and efficient optoelectronic neural interface(Wiley-VCH Verlag GmbH & Co. KGaA, 2022-08-01) Karatum, O.; Yildiz, E.; Kaleli, H. N.; Sahin, A.; Ulgut, Burak; Nizamoglu, S.Optoelectronic biointerfaces offer a wireless and nongenetic neurostimulation pathway with high spatiotemporal resolution. Fabrication of low-cost and flexible optoelectronic biointerfaces that have high photogenerated charge injection densities and clinically usable cell stimulation mechanism is critical for rendering this technology useful for ubiquitous biomedical applications. Here, supercapacitor technology is combined with flexible organic optoelectronics by integrating RuO2 into a donor–acceptor photovoltaic device architecture that facilitates efficient and safe photostimulation of neurons. Remarkably, high interfacial capacitance of RuO2 resulting from reversible redox reactions leads to more than an order-of-magnitude increase in the safe stimulation mechanism of capacitive charge transfer. The RuO2-enhanced photoelectrical response activates voltage-gated sodium channels of hippocampal neurons and elicits repetitive, low-light intensity, and high-success rate firing of action potentials. Double-layer capacitance together with RuO2-induced reversible faradaic reactions provide a safe stimulation pathway, which is verified via intracellular oxidative stress measurements. All-solution-processed RuO2-based biointerfaces are flexible, biocompatible, and robust under harsh aging conditions, showing great promise for building safe and highly light-sensitive next-generation neural interfaces.Item Open Access Seasonal patterns of inflation uncertainty for the US economy: an EGARCH model results(IUP Publications, 2010) Berument, Hakan; Kose, N.; Sahin, A.The purpose of this paper is to assess the seasonal inflation uncertainties for a big open economy, the US, for the period from January 1947 to April 2008. The paper uses EGARCH model which includes volatility in the conditional mean equation capturing the short-term and long-term volatility forecasts and leverage effects. The results indicate that seasonal inflation uncertainty increases in January, April and September and decreases in May, June, July and August.Item Open Access Seasonality in inflation volatility: evidence from Turkey(Universidad del CEMA, 2010) Berument, Hakan; Sahin, A.This paper assesses the presence of seasonal volatility in price indexes where a similar type of pattern has been reported in asset prices in financial markets. The empirical evidence from Turkey for the monthly period from 1987:01 to 2007:05 suggests the presence of seasonality in the conditional variance of inflation. Thus, inferences for the models that do not account for the seasonality in the conditional variance will be misleading.