Heavy metal resistance of microorganisms from petroleum hydrocarbon contaminated soils located in Mersin, Turkey

European Biotechnology Congress -- MAY 25-27, 2017 -- Dubrovnik, CROATIAWOS: 000413585400193…Ahi Evran Univ. BAP [PYO-Fen.4003/2.14.009 (2015)]This work was supported in part by a grant from Ahi Evran Univ. BAP No: PYO-Fen.4003/2.14.009 (2015)

A stochastic model for contact surfaces at polymer interfaces subjected to an electrical field

Morphology of the contact area between solid insulation materials ultimately determines the short- and long-term electrical properties of the complete insulation system. The main purpose of this paper is to propose a statistical model to examine the real area of contact between solid dielectric surfaces and secondly to verify and correlate the model outputs with experiments. The model computes the real area of contact, number of contact spots and average cavity size at the interface as a function of elasticity, contact force, and surface roughness. Then, using the average cavity size and the Paschen's law, the discharge inception field of the cavity (CDIE) is estimated. AC breakdown strength (BDS) testing of solid-solid interfaces was carried out, where cross-linked polyethylene (XLPE) samples with four different surface roughnesses were tested at various contact pressures. Following the increased contact force, the calculated average cavity size decreased by a factor of 4.08-4.82 from the roughest to the smoothest surface, corresponding to increased CDIEs by a factor of 2.01-2.56. Likewise, the experimentally obtained BDS values augmented by a factor of 1.4-1.7 when the contact pressure was elevated from 0.5 MPa to 1.16 MPa. A linear correlation between the CDIE and BDS was assumed, yielding a correlation coefficient varying within 0.8-1.3. When the 90% confidence intervals were considered, the range reduced to 0.86-1.05. This correlation suggests that interfacial breakdown phenomenon is strongly related to the interfacial cavity discharge. Hence, the proposed model is verified with experiments.A stochastic model for contact surfaces at polymer interfaces subjected to an electrical fieldsubmittedVersio

Use of Data-Driven Approaches for Defect Classification in Stator Winding Insulation

Partial discharges (PD) in the high voltage insulation systems are both a symptom and cause of terminal and impending failures. The use of data-driven methods based on PD measurements will enable predictive strategies to replace traditional maintenance strategies. This paper employs machine learningbased classification models to identify and characterize PD signals originating from lab-made artificial defects in epoxy-mica material samples. Three different PD sources were studied: surface discharges in air, corona discharges, and discharges caused by internal cavities/delaminations. To generate high-quality datasets for the training, validation, and testing of classification models, Phase-Resolved PD (PRPD) data for each test object was obtained at room temperature under 50 Hz AC excitation at 10 % above the PD inception voltage (PDIV) of each sample. Relevant statistical and deterministic features were extracted for each observation and were labeled based on the defect type (supervised learning). Finally, the trained and validated ML models were used to identify PD sources in the service-aged stator winding insulation. Support vector machines (SVM), ensemble, and k-nearest neighbor (kNN) algorithms achieved significantly high accuracy (≥ 95 %) of defect identification.publishedVersio

Offshore wind farm site selection in Norway : using a fuzzy trigonometric weighted assessment model

Maximising the energy potential of offshore wind farms requires an in-depth assessment of technological, economic, sociopolitical, and environmental aspects. Given the large economic impact of large-scale projects, a robust site selection procedure is critical for limiting financial risks while supporting informed investments. This research uncovers a novel and multidisciplinary approach for boosting the efficacy of Norwegian and global offshore wind farm siting investments. The proposed method uses a two-stage fuzzy mathematical model that considers technical, economic, logistical, and environmental factors. It combines the Ordinal Priority Approach (F-OPA) and Trigonometric Weighted Assessment (TRWA) technique by using an in-depth techno-economic assessment. An alternative reactive power compensation model, power loss calculations, and associated techno-economic analysis were performed for the investigated offshore wind farm locations. Furthermore, the energy economic calculations are carried out to provide support for the proposed decision-making framework. The proposed methodology was tested through a case study, focusing on ranking Norwegian offshore wind farm sites selected from potential locations announced by The Norwegian Water Resources and Energy Directorate (NVE). Within the Norwegian offshore wind farm sites, the approach demonstrated a versatile and efficient decision-making process at both individual and collective levels, identifying the Sandskallen-Sørøya Nord project as a pivotal investment priority and providing valuable managerial insights to enhance Norway’s offshore wind initiatives. The model’s stability was affirmed through a sensitivity analysis, underscoring its potential to enhance renewable energy policy and decision-making globally

Load Compensation by DSTATCOM with LCL-Filter by Comparing Different Resonance Damping Methods

acceptedVersio

Yenilenebilir enerji sistemlerinin şebeke arayüzü için LCL tipi süzgeçli PWM çevirici tasarım ve denetimi.

This thesis involves the PWM and control unit design and simulation for three-phase PWM converter widely used for grid-interface of renewable energy systems, motor drives, etc. The study involves selecting the LCL filter parameters, switching frequency, the PWM method, the cost-effective feedback controlled algorithm, etc. for the converter. The design is verified by means of detailed computer simulations. The study considers the normal and unbalanced grid conditions, which may occur in the grid operating conditions. Several power ratings and operating conditions are considered to provide a thorough performance evaluation of the designed system.M.S. - Master of Scienc

A Deterministic Model for Contact Surfaces at Dielectric Interfaces Subjected to an Electrical Field

This paper presents theoretical and experimental studies aiming to explore the effects of the elastic modulus and surface roughness on tangential AC breakdown strength (BDS) of interfaces between polymers. Four different polymers with different elastic moduli were tested. The interfaces were formed between identical specimens and were AC breakdown tested at various contact pressures. In addition, interface surfaces were polished using four different sandpapers of different grit sizes to study the effect of surface roughness. A deterministic model based on the tribology of solid surfaces was proposed to simulate the deformation of the surface asperities in 3D as a function of the contact pressure, surface roughness, elastic modulus, and hardness of an interface. The simulation results were correlated with the results of the AC breakdown experiments, and they elucidated how cavities were linked at solid-solid interfaces and enabled the estimation of the gas pressure inside the cavities under different circumstances (roughness, elasticity, and pressure)

Mechanisms Governing Longitudinal AC Breakdown at Solid-Solid Interfaces

Insulation systems incorporating multilayer dielectrics are commonly used in many high-voltage applications where the interfaces between the dielectric layers are the most vulnerable regions. The primary purpose of this paper is to elucidate the mechanisms theoretically and experimentally that govern the AC breakdown of solid-solid interfaces. Two different polymers with different elastic moduli were tested. The interfaces were formed between the same specimens and were AC breakdown tested at various contact pressures. In addition, interface surfaces were polished using two different sandpapers of different grit sizes to study the effect of surface roughness. A comprehensive interface breakdown model was employed to scrutinize morphologies of solid-solid interfaces in relation to the measured interfacial AC breakdown and PD inception field strengths. PD activity in the cavities and electrical tracking resistance of contact spots between the cavities were found to be significantly affecting the interfacial breakdown phenomenon

Dielectric Strength of Polymeric Solid–Solid Interfaces under Dry-Mate and Wet-Mate Conditions

One of the most important causes of insulation system failure is the breakdown of the interface between two solid dielectrics; understanding the mechanisms governing this breakdown phenomenon is therefore critical. To that end, investigating and reviewing the practical limitations of the electrical breakdown strength of solid–solid interfaces present in insulating components is the primary objective of this work. The published literature from experimental and theoretical studies carried out in order to scrutinize the effects of the presence of solid–solid interfaces is investigated and discussed, considering macro, micro, and nano-scale characteristics. The reviewed literature suggests that solid–solid interfaces in accessories have non-uniform distributions of electrical fields within them in comparison to cables, where the distribution is mostly radial and symmetrical. Many agree that the elastic modulus (elasticity), radial/tangential pressure, surface smoothness/roughness, and dielectric strength of the ambient environment are the main parameters determining the tangential AC breakdown strength of solid–solid interface

Effects of Frequency and Temperature on Partial Discharge Characterization of Stator Windings

acceptedVersio