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Volkan Yamacli,Kadir Abaci 한국CDE학회 2021 Journal of computational design and engineering Vol.8 No.1
Optimal control of power converters to avoid voltage instability in cases such as system loading or faults is one of the most studied nonlinear problems that affect energy quality in power systems. The optimization problem related to converter control becomes more difficult with the inclusion of renewable energy systems while trying to fulfill power system constraints and providing an adequate amount of energy. In this paper, a simple approach based on artificial neural networks (ANNs) has been proposed and applied to photovoltaic-fed high-voltage DC and high-voltage AC systems interconnection consisting of PI-controlled power converters. By using the proposed method, converter control parameters are optimized for different cases to improve steady-state and dynamic voltage stability while also avoiding any kind of system faults. In order to implement hybrid control methodology by using ANN and PI control, the network should be well trained with samples including not only global best values but also the whole possible system characteristic. For this reason, a novel optimization algorithm, differential search algorithm, is used to sample solution space and train ANN by using random and localized samples. Obtained and presented results of the proposed approach show that due to robust and fast response, ANNs can be successfully used to overcome nonlinear security and optimization problems concerning power system stability.
Mustafa Yamac,Gungor Kanbak,Melih Zeytinoglu,Gokhan Bayramoglu,Hakan Senturk,Mustafa Uyanoglu 한국식품영양과학회 2008 Journal of medicinal food Vol.11 No.3
This study reports the hypoglycemic effects of the crude exopolysaccharide (EPS) produced from submerged mycelial culture of Lentinus strigosus (Schwein.) Fr. (Family Polyporaceae) in streptozotocin (STZ)-induced diabetic rats. In a dose-dependent study, diabetic rats were treated with EPS at doses of 50–150 mg/kg of body weight for 7 days. Serum glucose and plasma insulin levels were measured in normal, STZ-induced diabetic, and EPS-treated diabetic rats. Following oral administration of EPS dosages for 7 days, the serum glucose levels in the STZ-induced diabetic rats were reduced up to 21.1% at the dose of 150 mg/kg of body weight. The results revealed that orally administered L. strigosus EPS, at the dose of 150 mg/kg, exhibited a considerable hypoglycemic effect in STZ-induced diabetic rats. Plasma insulin levels of STZ-induced diabetic rats decreased as compared to control group rats (P < .05). Although insulin levels slightly increased in the EPS-treated groups the increase was not statistically significant. The hypoglycemic potential of the EPS was further supported by histological observations of pancreatic islets of Langerhans.
Cilem YAMAC,Mert Sinan OZ,Ismail Naci CANGUL 장전수학회 2018 Proceedings of the Jangjeon mathematical society Vol.21 No.3
Energy of a graph was defined by E. Hückel as the sum of absolute values of the eigenvalues of the adjacency matrix during his search to find a method to obtain approximate solutions of Schrödinger equation for a class of organic molecules. It is an important sub-area of graph theory called spectral graph theory. Schrödinger equation is a second order differential equation which includes the energy of the corresponding system and as we can model all molecules with graphs, we can calculate the energy of a given graph. Here we obtain the exact formulae and recurrence relations for the edge-characteristic and incidency polynomials of some well-known graph classes.