Eastern Mediterranean University
  • Famagusta, TRNC, Cyprus
Recent publications
The difficulty of the production stages of panel radiators used for heating purposes reveals the importance of determining the heat transfer performance and panel radiator weight values, which are determined depending on the design parameters. In the present work, an artificial neural network model is proposed for predicting the heat transfer and weight values of a panel radiator as outputs depending on the design parameters of convectors. In the multilayer network model developed with 78 numerically obtained data sets, 8 different design parameters were defined as input parameters and heat transfer and in the output layer panel weight values were obtained. The design parameters of the convectors, in other words, input parameters of network model were chosen as the height of convector, thickness of convector sheet, the trapezoidal height of convector, convector base length, opposing convector distance, tip width of convector, convector vertical location and distance between convectors. For the proposed neural network model, the mean squared errors obtained for the heat transfer and panel radiator weight are −1.25E-04 and -7.54E-05 respectively. In addition, an R-value of 0.99999 has been obtained, and the average deviation value has been calculated as 0.001%. The obtained results show that, depending on the design parameters, the proposed artificial neural network model can predict the rate of heat transfer and weight of the panel radiator with high accuracy. This investigation is supposed to fill a significant gap since it is the pioneer one in open sources on machine learning modeling of panel radiators. Thus, it can possibly make a crucial contribution to the related manufacturing industry.
Understanding burnout and its effects on employees’ performance and wellbeing has been studied since the 1980s. Monitoring burnout syndrome among health care professionals, such as physicians and nurses, is a critical task. On the one hand, medical staff has to be good at controlling their own emotions in confronting the health care challenges; on the other hand, they share similar emotional exhaustion, frustration, and feelings with their own patients. This can lead to medical diagnosis errors, weak performance, and lower quality of treatments. The main purpose of this study is to provide a concise literature review of research works on burnout syndrome among medical staff, including research methods, assessments, solutions, and best practices. No matter their field of expertise and responsibilities, burnout is a considerable common psychological syndrome among medical staff, ranging from 40 to 66%. The Maslach Burnout Inventory (MBI) has been the most widely used questionnaire for data collection in the literature. Factors such as age, gender, marital status, and working conditions are identified as the most contributive parameters in the severity of burnout. Furthermore, studies have found that the degree of burnout can be reduced by under-taking self-improvement techniques such as meditation, development of communication skills, peer coaching, and doing art therapy. A considerable number of medical personnel are vulnerable to burnout syndrome in various degrees and forms. This common phenomenon threatens patients’ health and lives due to a reduction in medical care quality. This review covers the best practices for protecting and overcoming the hardnesses and challenges ahead of many health care professionals in their careers.KeywordsBurnoutDepersonalizationEmotional exhaustionPersonal accomplishmentMaslach
Background Host inflammation has been studied in patients with ischemic stroke (IS) due to large vessel occlusions. Inflammatory markers were shown to correlate with large artery atherosclerosis and worse outcomes after ischemic stroke due to large vessel occlusions. However, the association between inflammation and cerebral small vessel disease (SVD) is controversial. Mostly studied are the white matter hyperintensities; however, results regarding association of white matter hyperintensities with inflammatory markers are conflicting. We aimed to investigate the association between cerebral microbleed (CMB) load, as an indicator of SVD, and inflammation indices in patients with IS. Results We identified 127 patients with IS admitted within 7 days of symptom onset. CMBs were detected in 37% ( n : 47) of patients. Patient’s age and Fazekas score were independently associated with CMB load. Inflammatory biomarkers were not associated with the presence or quantitative burden of CMBs. Conclusions White matter damage and patient’s age predicted CMB presence and number, respectively, in IS patients. However, inflammatory markers failed to show any association with such SVD signs. Prospective studies with a higher number of stroke patients are needed in order to justify our findings.
This is a comment on the paper [Optics and Laser Technology 128 (2020) 106233; https://doi.org/10.1016/j.optlastec.2020.106233] titled “Exact coupled solution for photothermal semiconducting beams using a refined multi-phase-lag theory”. Herein, we report a serious error in an important dimensionless parameter employed in the problem, revealing that the defined parameter is dimensional and wrong. Accordingly, all given numerical results are based on this serious mistake, and are completely erroneous.
Nonlinear forced vibration and dynamic buckling of fixed functionally graded graphene platelet-reinforced (FG-GPLRC) porous arches under impulsive loading are investigated. The porosity coefficient varies along the thickness of arch based on a power law distribution with uniform dispersion of graphene platelets (GPLs) in the whole arch. The FG-GPLRC porous arch is made of closed-cell metal foams whose effective materials properties are determined by the volume fraction distribution of materials together with Halpin–Tsai model. The nonlinear motion equations of the FG-GPLRC porous under impulsive loading are derived by employed Hamilton’s principle, and numerically solved by Runge–Kutta (RK) method combined with the differential quadrature method (DQM). Based on the Budiansky–Roth (B-R) criterion of dynamic buckling, the critical dynamic buckling load of the arch is also determined. Two case studies are conducted to show the determination of the dynamic buckling load of the arch, and good accuracy of the developed method in predicting the critical dynamic buckling load of both shallow and deep arches is also verified. Numerical results show that the nonlinear forced vibration and dynamic buckling of arches are quite sensitive to impulsive load duration. In addition, FG-GPLRC porous arches have significantly higher critical dynamic buckling load when undergoing instantaneous impact loading.
Due to the importance of examining the temperature of battery packs (BYP), a study on the temperature of a lithium-ion BYP with 9 cylindrical cells is performed in this article. The BYP is filled with phase change material (PCM) to better temperature uniformity on the battery cells. The batteries and the PCM pack are placed in an air channel with two inlets. At the inlets, 4 arc blades are supposed to guide the airflow to enhance the uniformity of cooling in the BYP. By changing the horizontal and vertical distance (VD) of the batteries inside the pack, this study is carried out in 2500 s for the charging and discharging times of the batteries (1.5C rate). The thermal analysis is done on the batteries using COMSOL software. The results show that an increment in the horizontal distance (HD) of batteries has less effect on battery temperature (T-BT) and PCM phase change compared to their VD. By enhancing the horizontal and VDs of the batteries, the value of the PCM phase change during the maximum T-BT is higher. The heat transfer coefficient (HTCT) between the PCM and the air is also decreased by increasing the distance between the batteries. The T-BTs is not significantly impacted by changing the distance between them.
In this paper, a 3D battery pack (B-PK) containing 16 battery cells (BCL) with aligned and non-aligned arrangements is simulated. The batteries are 18,650 lithium-ion cylindrical ones. The B-PK is placed in a square air duct. Air enters from the top of the B-PK and exits from the bottom of the batteries. This study is performed by changing the inlet air velocity (V-AR) to the B-PK from 0.03 to 0.09 m/s for three charging and discharging cycles within 2000 s. The findings revealed that extending the duration and charging and discharging of the B-PK up to the third cycle increased the temperature of B-PK. The effect of V-AR changes is more pronounced in the second and especially the third cycles of battery charging process. The maximum (T-MX) and average (T-AV) temperatures of the B-PK as well as the temperature of air leaving the B-PK are all reduced when the V-AR is increased. The central batteries of the B-PK have a high temperature, whereas the batteries at the B-PK corners have a low temperature, according to an analysis of BCLs. Using an aligned arrangement of batteries in the pack reduces the T-AV of B-PK compared to the non-aligned arrangement of batteries.
We study and solve linear ordinary differential equations, with fractional order derivatives of either Riemann–Liouville or Caputo types, and with variable coefficients which are either integrable or continuous functions. In each case, the solution is given explicitly by a convergent infinite series involving compositions of fractional integrals, and its uniqueness is proved in suitable function spaces using the Banach fixed point theorem. As a special case, we consider the case of constant coefficients, whose solutions can be expressed by using the multivariate Mittag–Leffler function. Some illustrative examples with potential applications are provided.
In the present work, a study has been performed on increasing the heat transfer of parabolic solar collectors through modeling of twisted tapes inside the absorber tube containing nanofluid, using ANSYS19.2 software with Finite Volume Method (FVM). In this regard, two specimens of twisted tape with different number of channels is installed in the absorber tube having a constant wall heat flux (1200 W) in the range of Re numbers (25,000–5000) flows with different volume fractions (2–6%). Performance Evaluation Criterion (PEC), Nusselt Number (Nu) and solar collector efficiency (η) have been defined and their changes have been investigated. And achieve high efficiency (2.18) at Re=25,000, φ=2%. Therefore, model two turbulator is more desirable from the point of view of thermal fluid dynamics. The exergy efficiency of the liquid containing nanoparticles with a volume fraction of 2% declined for Cases 2, and 1 by about 0.023% and 0.026%, respectively, with increasing velocity. The neural network was used to trend the effects of perturbation on Nu, PEC, and exergy efficiency. The neural network trended three parameters with high accuracy so that the maximum error was estimated below 3.8%.
This paper presents a continuous terminal sliding mode controller (CTSMC) for single-phase dynamic voltage restorers (DVRs). The presented controller can substantially eliminate the chattering compared to the first-order sliding mode counterpart while achieving faster convergence speed compared to the super twisting counterpart. Moreover, the continuous control signal enables the voltage source inverter to operate at constant switching frequency. As the reference compensation voltage generator, an enhanced single-phase self-tuning (SP-STF) filter is also proposed. The SP-STF has excellent band-pass filtering property, can completely attenuate DC offset and has fast dynamic response. The SP-STF has been made frequency-adaptive through unknown grid frequency estimation under a delayed-based linear regression framework. Comprehensive stability analysis of the controller and filter are presented. Experimental studies are performed to demonstrate the effectiveness of the proposed comprehensive control solution. Comparative simulation studies are also provided to highlight the advantages of the proposed approach. Results show that the proposed technique can quickly detect and compensate for any grid voltage fluctuations and helps to maintain constant voltage at the load side despite voltage sag/swell and distortions.
By the increase of population and development of technology in recent years, energy demand has also increased. Due to the limitedness of energy resources, new research works and inventions are needed to ensure the continuity and efficient consumption of these sources and addressing economic problems. It is important to provide low-cost energy in living, industrial and commercial spaces with zero emission. Solar energy is an unlimited, clean and abundant energy source. However, the conditions of taking full advantage of sun vary seasonally. With the storage and conversion of solar energy, the sun, which is abundant in the summer period, can be used in the winter period. In this case, energy storage and conversion performance is extremely important to obtain the highest rate and efficiency from solar energy. The application and development of nanomaterials are popular issues in all fields, especially in energy storage and conversion applications, and play key roles in storage efficiency. Furthermore, phase change materials (PCMs) have successful and potential applications in the storage and conversion of solar thermal energy. In this study, research on efficient nanomaterials used in solar energy storage and conversion has been reviewed and discussed. According to the reviewed studies, efficiency was increased with the use of nanomaterials in solar energy storage and conversion systems. Particular attention was paid to the high charge and discharge rates of graphene and graphite-containing nanomaterials, as well as nanoparticles and composite materials added to PCMs. In addition, it has been stated that thermal energy is stored efficiently by the application of PEG support to composite materials. According to previous studies, the size, concentration, shape, and phase change of materials had critical effects on the storage efficiency of composite materials.
In this paper, airflow around 16 cylindrical lithium-ion cells placed in a square battery pack (BTP) is numerically examined. Laminar airflow enters the BTP from the top of the battery cells (BTC) and exits from the bottom of the BTP. In this three-dimensional analysis, the effect of the air inlet and outlet cross-sections on the temperature of the battery (T-BT) cells and the maximum and average T-BT pack is evaluated. The finite element method is used to solve the equations of battery and airflow. The results show that the upper part of the BTCs is at a lower temperature than the lower parts. The BTCs located in the middle of the BTP have a higher temperature than the ones located around the BTP. An increment in the air inlet cross-section reduces the average and the maximum T-BT pack. Enhancing the air outlet cross-section has little effect on the T-BT cells. The T-BT cells is enhanced until 1500 s, after which it is reduced because the airflow is diminished due to that the battery charging stops.
In order to investigate the shear behaviors of high-strength friction-grip bolts (HSFGBs) under combined shear and tensile forces in steel-SFRC composite beams, eight pull-out specimens with HSFGBs were fabricated and tested. Initial slip force, initial shear stiffness, post slipping stiffness, ultimate shear strength and ultimate slipping of HSFGBs were reasonably defined to quantitatively evaluate the shear behaviors of HSFGBs. Then, finite element models were carefully established and calibrated against test data using ABAQUS software. The influence of tensile force on the shear performance of HSFGBs was also discussed. Load transfer and failure mechanisms of HSFGBs and their influences on the shear behavior of HSFGBs under different tensile forces were analyzed. An improved interaction equation was derived for the calculation of HSFGB ultimate strength under combined shear and tensile forces. The obtained results indicated that both shear deformation and necking phenomenon of HSFGBs occurred under combined shear and tensile forces. Initial slip force, initial shear stiffness, post slipping stiffness and ultimate shear strength of HSFGBs were found to decrease with the increase of tensile force. HSFGB axial stress was first increased and then decreased with the increase of tensile force. In addition, HSFGB shear stress was only slightly changed under different tensile forces. Furthermore, improved interaction expression accurately predicted shear strength of HSFGBs under combined shear and tensile forces.
In recent years, mechanical characteristics including vibration, bending, buckling and postbuckling, stability and instability, etc. of small-scaled structures (such as micro/nanowires, micro and nano plates, micro and nano tubes, micro and nano beams, carbon micro/nano-tubes, micro and nano shells, micro and nano probes, etc.) have been broadly investigated, because of recent advances in nanotechnologies and due to their astonishing characteristics. Also, these small-scaled structures are extensively applied in several areas. However, comprehending the mechanical characteristics of these small-scaled structures is of great prominence and yet a daunting task. To understand the mechanical behaviors and capture the effects (including small-scale effect) of these different advanced small-scaled structures (at micro and nano levels), it is very essential to implement them into classical/nonclassical continuum elasticity based on a suitable classical/nonclassical elasticity formulation or theory. Thus, this work searches the literature and hereby presents an ample literature review study with a special focus primarily on the novel progress of vibration analyses of microplates and nanoplates using nonlocal/nonclassical continuum theories of elasticity. Scopus and web of science databases were used as the primary scholarly-databases to acquire the documents reviewed in the current research. Furthermore, several perspectives of classifications are considered while reviewing and grouping these acquired documents. The main purpose was to illustrate existing research trends in the vibrational analysis of small-scaled plate-based structures utilizing nonlocal plate-based theories and nonclassical continuum elasticity theories, and to provide a foundation and guidance for future research on the mechanics of small-scaled plate-based structures.
Numerical simulation and artificial neural network modeling of turbulent flow inside a pipe equipped with two spring turbulator samples with two different scales and a segmental cross-section have been investigated. Increased heat transfer rate (HTR) due to the use of a spring turbulator is predicted for the TiO2Cu-Water hybrid nanofluid based on the single-phase model, feed-forward artificial neural network (ANN) and fitting method. The role of Reynolds number (Re), scale and volume fraction (ϕ) on Nusselt number (Nu), pressure drop (ΔP), performance evaluation coefficient (PEC), solar collector efficiency (η), and the field synergy principle (FSP), compared to simple pipe, is considered using the finite volume method. The results show that increasing the spring turbulator scale increased the contact surface of the working fluid and the spring turbulator. As a result, the flow turbulence is increased, which leads to better mixing of the nanofluid as the operating fluid of the solar collector absorber pipe. Finally, ANN outputs and fitting results are compared, and it has been observed that the obtained ANN could predict the targets accurately.
The effects of using hybrid nanofluids and of helical coil pitch (λ) in a 3D shell and tube heat exchanger (STHE) are investigated. The algorithm used in this study is Phase Coupled SIMPLE and the method used is Eulerian. Nanofluid flow with Reynolds (Re) numbers of 10,000, 15,000, and 20,000, nanoparticles with volume fractions (ϕ) of 2 and 4%, and λ = 20, 25, 40, and 50 mm are investigated. The highest numbers related to the thermal index (Nu) and effectiveness occurred in the λ = 20 mm and the maximum ϕ and Re. In the case of λ = 20 mm, the maximum Nusselt number is 15.8%, 26%, and 45.3% more than that of 25, 40, and 50 mm, respectively. However, in the same case, in comparison between the ϕ = 4% and ϕ = 0, the Nu increases by 45.7%, 61.7%, and 76%. The present study shows that combining using hybrid nanofluids and changing the geometry of STHE, as an innovative approach can positively increase efficiency. Finally, the results are used for training an artificial neural network (ANN). In this regard, for finding the optimum neuron numbers in the hidden layer, the optimum feed-forward network is obtained to predict the efficiency of the material.
In this article, we consider an Itô stochastic semilinear differential equation with unknown initial state and a linear observation system. It is proved that under a certain condition on the observability Gramian, the initial state of the equation can be recovered. This result is demonstrated by an example.
The building walls are composed of several layers to protect the building from temperature fluctuations of the external environment. Increasing the number of layers in a building certainly strengthens the wall's ability to reduce heat transfer. But on the other hand, it increases the thickness of the walls and thus reduces the useful floor area of the building, which has no economic reason. In this study, the effect of reinforcing building walls against heat transfer using PCM was discussed. At constant PCM thickness, the installation location of this material varies from the outermost to the innermost. At the best location, the installation of PCM inside the wall/roof resulted in energy savings by 14.9 kWhmwall2 19.6 kWhmroof2 and taking into account their area, for the whole building, energy-saving was 15.9 kWhmroof2+mwall2. The effectiveness of ANN on PCM applications was amazing. Annual energy consumption for the building is 64.236 kWhm2. The neural network, by establishing a connection between the data predicts the annual energy consumption of 64.209 kWhm2. Therefore, the error was less than 0.04%. The monthly analysis also shows that for monthly EC, the error was less than 1.5%.
We investigate the Hilfer-type operator within the topic of tempered fractional calculus with respect to functions. This operator, the tempered Ψ-Hilfer derivative, is defined for the first time here, and its fundamental properties are studied, such as composition properties, function space mappings, and other functional analysis properties. We also consider fractional differential equations involving these operators, and establish existence, uniqueness, well-posedness, and stability results for such equations under suitable conditions.
We introduce the delayed Mittag-Leffler type matrix functions, delayed fractional cosine, and delayed fractional sine and use the Laplace transform to obtain an analytical solution to the IVP for a Hilfer type fractional linear time-delay system D 0 , t μ , ν z t + A z t + Ω z t − h = f t of order 1 < μ < 2 and type 0 ≤ ν ≤ 1 , with nonpermutable matrices A and Ω . Moreover, we study Ulam-Hyers stability of the Hilfer type fractional linear time-delay system. Obtained results extend those for Caputo and Riemann-Liouville type fractional linear time-delay systems with permutable matrices and new even for these fractional delay systems.
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3,008 members
İzzet Sakallı (I.Sakalli)
  • Department of Physics
Fatma Guven Lisaniler
  • Department of Economics
Adnan Acan
  • Department of Computer Engineering
Onsen Toygar
  • Department of Computer Engineering
Famagusta T.R. North Cyprus via Mersin 10, Turkey , 99628, Famagusta, TRNC, Cyprus
Head of institution
Prof.Dr. Aykut Hocanın