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Yayın Tarihi [9]
Dergi Adı [19]
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Yazar Departmanı [1]
Surface plasmon-enhanced nanoantenna for localized fluorescence

Kocakarin, I. | Yegin, K.

Article | 2012 | International Journal of Antennas and Propagation2012

Surface plasmon-enhanced gold nanoantenna structures on glass substrate are studied for increased localized electric field and fluorescence at the feed gap locations of the antennas. Dipole, Archimedean balanced spiral, and bowtie and double bowtie geometries are studied for surface plasmon effect. Different flare angles for bowtie geometries are compared to each other. Double bowtie geometry with dual polarization capability exhibited superior performance with almost 56 dB field enhancement factor. We also studied the effect of substrate thickness on electric field enhancement and we found that glass thickness plays a critical role . . . for coherent addition of surface plasmons at the feed gap location. The surface plasmon effect is proven by considering perfect electric conductor model of gold instead of its modified Drude model. © 2012 Isa Kocakarin and Korkut Yegin Daha fazlası Daha az

Smart and reconfigurable antenna applications in wireless sensor networks

Yegin, K. | Kavak, A. | Cayirci, E. | Dandekar, K.

Editorial | 2014 | International Journal of Distributed Sensor Networks2014

[No abstract available]

Prompt and delayed fluorescences

Yegin, K. | Karaaslan, Ş.I. | Aslan, N.

Editorial | 2012 | International Journal of Photoenergy2012

[No abstract available]

Application of electromagnetic reciprocity principle to the computation of signal coupling to missile-like structures

Yegin, K.

Article | 2012 | Progress In Electromagnetics Research M23 , pp.79 - 91

Lorentz Reciprocity principle is often used to describe electrical networks and reception/radiation properties of antennas residing in a linear, time-invariant, and symmetric medium. In its reaction integral form, it is usually conceived as a mathematical tool to prove electromagnetic relations. However, reciprocity, more than a mathematical tool, can be used as a powerful alternative to convert a penetration problem into a radiation one for numerical computations and measurements. We review the reciprocity formulation and show simple steps on how to apply reciprocity to penetration problems. Numerical calculations for a wire probe . . .(antenna) inside missilelike structure are carried out for both radiation and its reciprocity formulated penetration problems, and it is shown numerically that results from both methods are identical. One of the advantages of this indirect formulation is that the radiation properties of the structure can be easily measured contrary to the direct measurement of the penetrated signal inside the structure Daha fazlası Daha az

Micro size detector antennas at 30 THz

Nassor, M.A. | Korkmaz, E. | Yegin, K.

Conference Object | 2014 | 2014 31th URSI General Assembly and Scientific Symposium, URSI GASS 2014 , pp.79 - 91

Planar antennas such as microstrip patch, bowtie, spiral, and modified crossed dipole are designed and simulated at 30 THz. Gains of antennas obtained directly from simulation results are verified using a different technique inspired from radar cross section measurements. Reradiated far field of an antenna when its feed point is open-circuited is obtained with a far-field probe. The proposed method is introduced as an alternative for the signal detection sensitivity measurements of IR detector antennas. © 2014 IEEE.

Gain-bandwidth product for aperture-coupled antennas

Bilgiç, M.M. | Yegin, K.

Conference Object | 2013 | 2013 Computational Electromagnetics Workshop, CEM 2013 , pp.21 - 22

Bandwidth, gain, and HPBW are the most essential design characteristics in antenna design. Other features such as cross polarization ratio, front-to-back ratio, in-band gain ripple, electrical height, and physical dimensions also play a critical role in the design. It is difficult to define a common figure-of-merit (FOM) that includes all these metrics, but we present several FOM applicable for aperture coupled antennas. Various nonresonant and resonant slot coupled stacked patches are compared to each other to identify the best configuration. Integral equation based solver is used in the computational analysis.

Simulation of an 18-vane magnetron in CST-PIC

Araz, I. | Dursun, A. | Demirci, E. | Korkmaz, E. | Yegin, K.

Conference Object | 2011 | 2011 30th URSI General Assembly and Scientific Symposium, URSIGASS 2011 , pp.21 - 22

This paper presents the simulation of a vane-type magnetron using the commercial electromagnetic software Particle-in-Cell (PIC) solver in CST. The magnetron mainly consist of 18 anode vanes without strap. The resonance frequency has been selected in X band since it has a long production history enabling a ready comparison of computed and measured results. Simulation of magnetrons has been improved by changing dimensions of cavities, optimizing voltage and applied magnetic fields values. The aim of this work is to tune the operation frequency of magnetron under the constant electric field and the magnetic field between the anode and . . . cathode. © 2011 IEEE Daha fazlası Daha az

Absorption and fluorescence spectroscopy of 1,2: 3,4-dibenzanthracene

Bayrakceken, F. | Yegin, K. | Korkmaz, E. | Bakis, Y. | Unal, B.

Article | 2012 | International Journal of Photoenergy2012 , pp.21 - 22

Polycyclic aromatic hydrocarbon compound, 1,2: 3,4-dibenzanthracene, is spectroscopically analyzed in ethanol. Ultraviolet absorption spectra were taken and fluorescence measurements were performed. From absorption and emission spectra, Stokes' lines were clearly discernible and these shifts were recorded. Being a carcinogenic compound, the detection of 1,2: 3,4-dibenzanthracene presence in the environment as a pollutant with adverse genotoxic effects is vital. © 2012 Fuat Bayrakceken et al.

Thin films prepared from nanometer size TiOabsorbs millimeter waves

Yesil, M.A. | Yegin, K. | Çulha, Mustafa | Efeoglu, E.

Article | 2012 | International Journal of Photoenergy2012 , pp.21 - 22

Absorption of average 10 nm size TiOnanoparticles deposited on glass surfaces as a thin film using convective assembly technique and drop-casting is studied in the millimeter wave range from 26 GHz to 40 GHz. The millimeter wave responses of the fabricated samples were obtained using a vector network analyzer. Reflection properties of the prepared samples were also measured. Absorption and reflection of TiOnanoparticles were more pronounced between 35 GHz and 40 GHz compared to glass-only sample. © 2012 Mehmet Ali Yesil et al.

Optical energy transfer mechanisms: From naphthalene to biacetyl in liquids and from pyrazine to biacetyl

Bayrakceken, F. | Yegin, K. | Korkmaz, E. | Bakis, Y. | Unal, B.

Article | 2012 | International Journal of Photoenergy2012 , pp.21 - 22

Optical energy transfer from naphthalene to biacetyl in liquids at room temperature is studied. Electronically excited naphthalene with 200-260 nm ultraviolet (UV) light emits photons in its emission band and the emitted photons are absorbed by biacetyl, which, in turn, excites biacetyl phosphorescence. The resulting phosphorescence is very stable with emission peak at 545 nm for different excitation wavelengths from 200 to 260 nm. Similar optical energy transfer is also observed from pyrazine to biacetyl. The sensitization of biacetyl by several aromatic donors has been investigated in detail. An aromatic donor, pyrazine, is raised . . . to its first excited singlet state by absorption of ultraviolet radiation. Excitation wavelengths were selected in the first n-? band of pyrazine. Intersystem crossing in pyrazine is sufficiently fast to give a triplet yield of almost unity as determined by the biacetyl method. The optical excess energy in the biacetyl will be released as light, which is sensitized fluorescence. Biacetyl is the simplest molecule among a wide range of ?-dicarbonyl compounds, which is important for photophysics and photochemistry applications. © 2012 Fuat Bayrakceken et al Daha fazlası Daha az

Tapered slot antenna design for vehicular GPR applications

Biçak, E. | Yegin, K. | Nazli, H. | Dag, M.

Conference Object | 2014 | Proceedings of SPIE - The International Society for Optical Engineering9077 , pp.21 - 22

Vehicular applications of UWB GPR demand multiple GPR sensors operating in a harsh environment. One of the key elements of in the sensor is its UWB antenna which has minimal inter-element coupling, low group delay, high directivity and less prone to environmental conditions. Tapered slot antennas (TSA's) provide good impedance match, but they need to be modified for above specifications. Parasitic slot loaded TSA with balanced feed is proposed and a multi-channel antenna array structure is formed. Structural parameters are numerically analyzed and a prototype is built. Measurements show good performance for UWB GPR applications. © 2014 SPIE.

Effect of pulse fidelity on detection of landmines

Öztürk, H. | Nazli, H. | Yegin, K. | Sezgin, M. | Biçak, E. | Belikli, H. | Dag, M.

Conference Object | 2013 | Proceedings of SPIE - The International Society for Optical Engineering8714 , pp.21 - 22

Detection of landmines based on complex resonance frequencies has been studied in the past and no distinctive results have been reported. Especially for low metal content landmines buried at depths greater than 9 cm, resonant frequencies become fairly distributed in the background and no specific frequency of interest can be used. However, in a typical impulse radar, spectral energy density of the transmitted pulse can be very broad and its peak can be located anywhere. Usually, a compromise is made between penetration depth and feature resolution for spectral energy peak allocation. Pulse amplitude, duration, symmetry, its spectral . . . energy distribution, ringing level all affect depth and resolution metrics in a complicated way. Considering receiver dynamic range, we study two distinct pulses having different spectral energy density peaks and their detection ability for landmines with little or no metallic content. We carry out experiments to show that pulse shape/fidelity is critical to obtain desired contrast in post-processing of data. © 2013 SPIE Daha fazlası Daha az

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