DSpace Arşivi :: Ana Sayfa

İstanbul Gelişim Üniversitesi Kurumsal Açık Erişim Arşivi

DSpace@Gelişim, İstanbul Gelişim Üniversitesi tarafından doğrudan ve dolaylı olarak yayınlanan; kitap, makale, tez, bildiri, rapor, araştırma verisi gibi tüm akademik kaynakları uluslararası standartlarda dijital ortamda depolar, Üniversitenin akademik performansını izlemeye aracılık eder, kaynakları uzun süreli saklar ve yayınların etkisini artırmak için telif haklarına uygun olarak Açık Erişime sunar.

WoS Yayınları

Scopus Yayınları

TR-Dizin Yayınları

PubMed Yayınları

Makaleler

Kitaplar

Bildiriler

Tezler

Güncel Gönderiler

Performance Analysis of Energy-Harvesting Amplify-and-Forward Relaying with Fluid Antenna Systems
(Multidisciplinary Digital Publishing Institute (MDPI), 2026) Yahya, Khalid; Aldababsa, Mahmoud; Arashloo, Banafsheh Alizadeh; Al Dawsari, Saleh; Khan, Sajjad Ahmad
This paper studies a cooperative wireless system in which a single-antenna base station (BS) communicates with a destination user (U) via a half-duplex energy-harvesting amplify-and-forward relay, while the direct BS–U link is unavailable. The destination (U) is equipped with a fluid antenna system (FAS) comprising multiple closely spaced receive ports, enabling spatial reconfigurability through instantaneous port selection. A power-splitting architecture is adopted at the relay to support simultaneous energy harvesting and information forwarding. All wireless links are modeled as flat Rayleigh fading, and the spatial correlation among the FAS ports is explicitly incorporated. To analytically characterize the impact of correlated port selection, a Gaussian copula framework is employed to model the joint distribution of the FAS-channel power gains. Exact integral expressions for the cumulative distribution function of the end-to-end signal-to-noise ratio are derived, from which the outage probability is obtained. For the special case of uncorrelated FAS ports, closed-form expressions are further developed using order statistics and special functions. In addition, asymptotic analysis is carried out to provide further insight into system performance in the high-signal-to-noise-ratio region. Numerical and Monte Carlo simulation results validate the analytical derivations and demonstrate that FAS-based receiver selection yields significant gains in outage performance, even in the presence of strong spatial correlation and energy-harvesting constraints.
Integrating Observational Datasets and CMIP6 Projections for Multi-Scale Drought Characterization: Evidence from Western Türkiye
(Multidisciplinary Digital Publishing Institute (MDPI), 2026) Aydemir, Sena; Hocalar, Çağlar; Şekerci, Kürşat; Paşa, Yasin; Çelik, Mehmet Ali
Although drought is recognized as one of the major hydroclimatic hazards affecting the Mediterranean Basin, local-scale assessments to support planning for its agricultural, hydrological, and food security impacts remain limited. This study investigates historical and future drought dynamics in Manisa (Western Türkiye) using a multi-scale framework integrating the Standardized Precipitation Index (SPI) and the Standardized Precipitation Evapotranspiration Index (SPEI) with CMIP6 climate projections. A comprehensive dataset including ERA5-Land, CHIRPS, TerraClimate, and station observations was evaluated, revealing strong agreement in temperature but higher uncertainty in precipitation. SPI results indicate recurrent short-term droughts with extreme events reaching −2.5 in 2007–2008, alongside intensified long-term hydrological droughts since the early 1990s, while SPEI reveals a stronger temperature-driven drought signal, peaking near −2.0 during 2020–2024 as the most severe cumulative drought period in the past 40 years. Rapid wet–dry transitions have increased since 2000, indicating a more unstable hydroclimatic regime. Future projections (2025–2100) under a high-emission scenario suggest a progressive intensification of thermally driven drought conditions, with SPEI trends declining more steeply than SPI, indicating that evapotranspiration-driven water deficits may increasingly outweigh precipitation deficits as a driver of future drought risk. These findings offer localized, data-driven evidence relevant to climate adaptation and water resource planning in semi-arid Mediterranean agricultural regions.
Relationship Between Fluid Control and Symptom Severity in Hemodialysis Patients
(SAKARYA UNIV, KEMALPASA MAHALLESI UNIV CADDESI ESENTEPE KAMPUSU, SAKARYA, SERDIVAN 54050, Turkiye, 2024) Demiralp, İkbal; Yılmaz, Feride Taşkın
Objective: This study was conducted to determine fluid control and symptom severity in hemodialysis patients, to reveal related factors, and to determine the relationship between fluid control and symptom severity. Methods: The descriptive and correlational study was conducted with 150 patients receiving treatment in a private hemodialysis center in Istanbul between 01-30 April 2022. Data were obtained using a patient identification form, the Fluid Control Scale in Hemodialysis Patients and the Dialysis Symptom Index. Results: The mean Fluid Control Scale in Hemodialysis Patients score of the patients was 50.75 +/- 8.13. The mean Dialysis Symptom Index score of the patients was 19.09 +/- 17.08. In addition, it was found that there was a weak negative correlation between the mean scores of the Fluid Control Scale in Hemodialysis Patients and the Dialysis Symptom Index (r=-0.349; p<0.05). Conclusion: It has been determined that the fluid control of hemodialysis patients is generally at a moderate level, the symptom severity is quite low, and the symptom level may decrease as the level of knowledge, behavior, and attitude toward fluid control increases. It is recommended that nurses should regularly educate and counsel hemodialysis patients about the importance of fluid control and closely monitor the patient's compliance with fluid control.
Qualitative Analysis of Non-Local Fractional Sturm–Liouville–Langevin Differential Equation and Inclusion With Time Delays
(ELSEVIER, RADARWEG 29, 1043 NX AMSTERDAM, NETHERLANDS, 2026) Serrai, Hacen; Tellab, Brahim; Thabet, Sabri T. M.; Abdeljawad, Thabet; Mukheimer, Aiman; Abdalla, Bahaaeldin; Kedim, Imed
We introduce time delays into the fractional Sturm–Liouville–Langevin framework to model hereditary effects and reaction lags in both single-valued and multivalued formulations. The problems are formulated using the generalized 𝜅-Caputo fractional derivative, and we establish existence and uniqueness results. For the singlevalued case, uniqueness is first obtained by applying the Banach fixed-point theorem with a 𝜅-Bielecki norm. The effectiveness of this norm lies in its capability to relax the strong sufficient hypothesis commonly imposed in the application of Banach’s fixed point theorem under the classical supremum norm — specifically, the contraction constant condition — by treating it in a more flexible and efficient manner through the use of this norm. In a special case, by subdividing the time interval and applying Burton’s progressive contraction method, we obtain uniqueness under the relaxed Lipschitz assumption, thus extending beyond the strict hypothesis required by Banach’s theorem — specifically, the contraction Lipschitz condition —. For the multivalued case, the Leray–Schauder nonlinear alternative is employed, which significantly broadens the existence theory by accommodating noncompact operators under 𝐿1 -Carathéodory conditions. Finally, illustrative examples validate the theoretical results.
Dielectric Relaxation and Electrical Transport Mechanism of NiFe2O4/MnPrxFe2−xO4 (x≤0.10) Nanocomposites
(Springer, 2026) Almessiere, Munirah Abdullah; Baykal, Abdulhadi; Ünal, Bayram; Slimani, Yassine Abdelhamid; Demir Korkmaz, Ayşe
In this study, the dielectric relaxation and electrical transport mechanism of MnPrxFe2−xO4/NiFe2O4 (x ≤ 0.10) nanocomposites (NFO/MnPrxFe2−xO4 (x ≤ 0.10 NCs)) were systematically investigated as a function of the Praseodymium (Pr) substitution ratio (x ≤ 0.10) and temperature (20–120 °C). MFO nanoparticles (NPs), NFO NPs, and NFO/MnPrxFe2−xO4 (x ≤ 0.10) NCs were created via a one-pot sol–gel route. XRD (X-ray powder diffraction) analyses confirmed the purity of MFO NPs, NFO NPs, and NFO/MnPrxFe2−xO4 (x ≤ 0.10) NCs (with the presence minor amount of α-Fe2O3 for x = 0.08 and 0.1). The DXRD (crystallite size) of NCs was estimated between 24 and 57 nm. The characterization was performed using impedance spectroscopy and the electric modulus formalism to deconvolve the contributions from grain and grain boundary effects. All NCs exhibited semiconductor-like behavior with a negative temperature coefficient of resistance (NTCR), governed by a thermally activated hopping mechanism. A non-monotonic dependence of dc resistance on the substitution ratio was observed, with a minimum value, corresponding to maximum conductivity, identified at x = 0.06. Conversely, electric modulus analysis revealed that the bulk (grain) dielectric structure becomes maximally complex at x = 0.04, characterized by the emergence of multiple, well-resolved relaxation mechanisms. This differential influence of the dopant on the grain and grain boundary properties highlights a pathway for selectively engineering the overall conductivity and internal dielectric response of ferrite-based nanostructures for targeted electronic applications.