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Öğe The relationship between screen exposure and neck disability, headache, stress, depression, and anxiety in university students(Kare Publ, 2023) Yilmaz, Halil; Goz, EvrimObjectives: In recent years, with the development of technology, screen exposure among university students has increased and caused various physical and psychological effects. The aim of this study is to investigate the relationship between screen exposure and neck disability, headache, stress, depression, anxiety, and sleep disorders in university students.Methods: Two hundred and twenty-six students were evaluated online in this study. Study outcomes were headache, depression, anxiety, stress, neck disability, and sleep quality.Results: When the screen exposure was examined, it was observed that the stress, anxiety, and depression levels of the students increased as the smartphone use increased (p<0.05). Headache severity (p=0.028) in those who use smartphones for 7 h or more; It was observed that the frequency of severe neck disability increased in those who used a smartphone or computer for 7 h or more (p=0.005, p=0.026).Conclusion: To prevent physical and psychological problems that may arise due to the increase in screen use time in university students, it is necessary to monitor the frequency of screen use of the students, to organize trainings that explain the physical and psychological effects of long-term screen exposure and increase the level of awareness.Öğe Improving the Experiences of Mothers Struggling with Their Children's Misbehavior(Cukurova Univ, 2021) Kurt, S. Hulya; Dikici Sigirtmac, Ayperi; Ozsezer, Muzaffer SencerThe aim of this study was to examine the perceptions of mothers' and their children regarding the children's misbehaviour and the mothers' response to it. The research was carried out through the action research approach, which is a qualitative research methodology. The research data were collected through interviews, training evaluations, and participant diaries. The data analysis was carried out using content analysis. The study participants consisted of children attending nursery school in the Anamur district of Mersin, Turkey and the mothers of these children. The action research process began with the interview and observation data from the participating children. In light of the information obtained from these data, interviews were conducted with the mothers to determine their needs as well as identify their difficulties with their children's misbehaviour. As a result of the mothers' interviews, training was prepared utilizing expert opinion to improve the mothers' experiences who had been struggling with their children's misbehaviours. As a result of the study, it was seen that mothers used physical violence as discipline/punishment to address their children's misbehaviour. By analysing the data obtained from the participants, the needs of the mothers struggling with the children's misbehaviours were determined. An action plan was prepared in line with this needs analysis. As a result of the training according to the action plan, it was concluded that the mothers recognized their mistakes and learned from their deficiencies. It was also found that mothers noticed that their relationship with their children had changed positively. Additionally, it was concluded that the trainings should be repeated at certain intervals and that the children's fathers should also participate.Öğe Awareness of child abuse and neglect among students(Kare Publ, 2022) Uysal, Gulzade; Bozkurt, Gulcin; Duzkaya, Duygu SonmezObjectives: This descriptive study was conducted to determine the level of awareness of child abuse and neglect (CAN) among students at a private university in Istanbul, Turkey. Methods: The study sample comprised 1533 students from all faculties and colleges of the university selected using the stratified sampling method. A demographic information form and the Child Abuse and Neglect Awareness Scale (CANAS) were used to collect the study data. Results:The findings revealed that 30.5% of the students had received some instruction about CAN and 72.9% indicated that they wanted lectures on CAN to be added to the curriculum. The mean total score of the CANAS and the mean scores of the physical abuse, emotional abuse, and neglect subscales were statistically significantly higher among female students (p<0.05). The physical abuse and neglect subscale scores of students who had formal education on abuse were higher than those of students who had not (p<0.05). Conclusion:The female students and those who had received instruction about abuse had greater awareness of abuse and neglect. Broader coverage in the curriculum may increase the awareness of all students and help to enhance public understanding.Öğe Evaluation of the Effect of Oral Motor Stimulation Exercises on Feeding Skills in Premature Infants(Kare Publ, 2023) Atay, Funda Yavanoglu; Ciftci, Hilal Berber; Sahin, Ozlem; Guran, Omer; Colak, Derya; Gok, Nazife Reyyan; Erdem, Burcu KarakolObjectives: Oral feeding in preterm infants is a complex and dynamic process involving oral motor development and interaction between the neurological, cardiorespiratory, and gastrointestinal systems. Oral motor stimulation (OMS) is defined as stimulating the oropharyngeal components such as the lips, jaw, tongue, and soft palate with fingers in preterm infants to increase their feed-ing skills. In this study, we aimed to evaluate the effect of OMS exercises on the sucking and swallowing skills of preterm infants and demonstrate the utility of objective scales to evaluate infants' readiness for oral feeding.Methods: This single-center, prospective cohort study was conducted between June 1st and December 31st, 2020, which included preterm infants born at & LE;34 weeks of gestation and admitted to the neonatal intensive care unit of our hospital. All procedures of the OMS program were performed once a day, 5 times a week by a language and speech therapist who is an expert in oral feeding skills (OFS) staging and non-nutritive sucking (NNS) scoring. All infants were followed up until discharge with a weekly evaluation of OFS staging and NNS scoring.Results: A total of 50 infants were included in this prospective cohort study. The mean birth weight was 1376.9 & PLUSMN;372 g, and the me-dian gestational age was 30 weeks (interquartile range: 25-34). The comparison of OFS stages on day 5 and day 10 of OMS revealed a significant increase (p<0.001). Similarly, there was a significant improvement in the NNS scores on days 5 and 10 compared to the baseline.Conclusion: In preterm infants, OMS during the transition from gavage feeding to oral feeding improves feeding skills.Öğe Short-term Effect of Elastic Taping on Balance and Postural Control in Patients with Early-stage Parkinson's Disease -a Non-controlled, Quasi-experimental Study(Galenos Publ House, 2023) Goz, Evrim; Donmez Colakoglu, Berril; Cakmur, Raif; Balci, BirgulObjective: Normal postural control and balance is achieved by the integration of visual, proprioceptive and vestibular sensory information. The patients with Parkinson's disease (PD), on the other hand, experience postural control disorders due to the lack of integration of these senses. Elastic taping is effective in improving expected postural adjustments by increasing proprioception and trunk muscle activation. The aim of this study was to investigate the short term effect of single session elastic taping on balance and postural control in patients with early-stage PD. Methods: Elastic tape was applied with posture correction techniques on the upper back of 23 patients with early-stage PD (18 men, 5 women) during on phase. The postural control and balance ability of patients was assessed with the limits of stability (LOS), Sit-to Stand, Walk Across and Tandem Walking Tests of NeuroCom Balance Master test device. The tests were repeated after elastic taping in all patients. Results: The maximum excursions and endpoint scores of LOS test, the speed of tandem walking test significantly increased after taping (Wilcoxon test, respectively; p=0.04, p=0.02, p<0.001). There was no significant difference between Walk Across and Sit to Stand results before and after elastic taping (Wilcoxon test, p>0.05). Conclusion: Our study is the first to investigate the short-term effects of elastic taping on balance and postural control in PD. It was concluded that the application of elastic tape in patients with PD could enhance dynamic balance and postural control parameters for a short time under challenging and complex conditions.Öğe Psychological Outcomes 1 Year After Restrictive Bariatric Surgery(Galenos Publ House, 2023) Gezer, Derya; Yurtseven, Seyma; Alptekin, Dudu; Erden, Sevilay; Arslan, SevbanObjective: To reveal the depression and body image changes observed in patients undergoing bariatric surgery. Methods: This prospective study followed a descriptivecorrelational study design. The study population consisted of patients hospitalized in the general surgery clinic of a university hospital in order to evaluate the depression symptom level and body image of patients undergoing bariatric surgery. The study sample comprised 22 patients who were admitted to the general surgery clinic of the same hospital and met the following criteria: being over 18 years of age, being fully oriented (time, person, place) and conscious, being able to see, hear, being able to read, write, speak and understand Turkish, being diagnosed as having obesity, being hospitalized for sleeve gastrectomy, and willing to participate in the study. The data for the study were collected using a Personal Information Form prepared by the investigators, the body cathexis scale (BCS) and the beck depression inventory (BDI) Results: Twenty two patients, 16 of whom were female, with a mean age of 31.18 +/- 7.79 years were included. The body mass index (BMI) (kg/m(2)) values recorded 1 year after the operation were significantly lower than the baseline levels (Z=-4.107; p=0.000). The mean BCS score 1 year after the operation was significantly lower than at the time of the baseline evaluation (t=3.447; p=0.002). The baseline BMI (kg/m(2)) value and BDI score were found to be positively correlated (r=0.448; p=0.036). The baseline BDI score increased with increased BMI (kg/m(2)) value, and baseline BDI score decreased with decreased BMI (kg/m(2)) value. Conclusion: The patients were found to have lost a significant amount of body weight one year after the bariatric surgery. The baseline borderline clinical depression and an intermediate level of depression were found to change toa mild depression one year after bariatric surgery. Bariatric surgery was determined to have a positive effect on body image perception.Öğe Self-Regulation in Child Development: Investigation of Preschool Education Duration and Teachers' Self-Regulation Levels(Turkish Education Assoc, 2023) Kurt, Serife Hulya; Sigirtmac, Ayperi DikiciThis study was conducted to examine the self-regulation of teachers working in preschool education institutions, their practices to support self-regulated learning, and the relationship between preschool education status and children's self-regulation skills. The sample of this study, in which the relational survey model, one of the quantitative research methods, was used, consisted of 316 teachers and 213 children working in primary school preschool classes and independent kindergartens affiliated with the Ministry of National Education in Mersin province. The demographic information of the participants was collected through the Demographic Information Form prepared by the researcher. Teachers' self-regulation was assessed with the Self-Regulation Scale, while the practices they used to support self-regulated learning were assessed with the Scale for Evaluating Preschool Teachers' Practices to Support Self-Regulated Learning (SC-SRLS). Children's self-regulation skills were assessed with the Preschool Self-Regulation Scale (PSRS), which requires face-to-face practice with each child. As a result of the study, it was found that children's self-regulation skills differed significantly in favor of children older than 68 months. In addition, it was determined that children's self -regulation and emotion regulation differed in favor of girls according to gender. In the study, the self-regulation skills of children with more than one year of preschool education were significantly higher than those of children with less preschool education. As a result of the study, it was determined that there was a positive and significant relationship between teachers' self -regulation and classroom practices to support self-regulated learning. In addition, there was a positive and significant relationship between teachers' self-regulation and the practices they used to support self-regulated learning and children's self -regulation skills.Öğe The Effect of Selected Macroeconomic Variables and Expectation Indices on the BIST 100 Index(Sosyoekonomi Soc, 2022) Ergin-Unal, Ayse; Nas, Serkan; Heybeli, MurvetIn this study, the macroeconomic factors and expectation indices affecting the BIST 100 index have been examined. The optimum Autoregressive Distributed Lag (ARDL) model has been created by utilising the Python programming language (Python) using the ARDL method. As a result of the analysis, it has been determined that long-term variables such as United States dollar Turkish lira parity (USD/TRY), Economic Confidence Index (EGE), and Consumer Price Index (TuFE) are correlated in the positive direction with the dependent variable BIST 100 index and in the negative direction with the 5-Year Bond Interest (FAIZ) and Volatility Index (VIX) variables. In contrast, Brent petrol United States dollar parity (BRENT) is not statistically significant.Öğe The Impacts of Financial Resource Management on Financial Worries(Eskisehir Osmangazi Univ, Fac Education, 2024) Ozbilge, Gokhan; Canatan, Behice; Ipek, OzlemThis study aims to investigate the possible causes of totalfinancial worryand COVID-19 induced financial worries, which include all of these in addition to the four common forms of financial worries arising from old age, payments, health, and education, for the Turkish sample. The empirical bases of financial behavior, financial resilience, social assistance, and socioeconomic factors, which are discussed and explained within the Family Resource Management Model framework, are obtained from the 2021 Global Findex dataset using an ordered logit model. The findingsindicate that reducing financial worries in Turkey is associated not only with income growth but also with financial behavior and resilience, which require financial resource managementÖğe The Dynamics of Household Food Insecurity in Turkey(Sosyoekonomi Soc, 2022) Ipek, OzlemFundamental needs such as adequate food, clothing, and shelter are the foundation of social well-being. With the increasing world population, the number of undernourished people is also gradually increasing. This situation triggers increased concern that groups with different socioeconomic characteristics in developing countries will not have sufficient access to the food necessary for a healthy life. Consequently, the food insecurity issue has become a global topic of interest. Identifying the determinants of household food insecurity is important to develop policies to eliminate or reduce the significant inequalities in households' access to food. This study seeks to identify the dynamics of households' food insecurity in Turkey through Income and Living Conditions Longitudinal Microdata applying the random effects logit model. We found that as education level, health status, and income increase, the likelihood of food insecurity significantly decreases. The probability of food insecurity for males is 4% higher than for females. Education and income are the most influential variables of food insecurity. We also measured the average increase in food insecurity over the years compared to the reference year of 2014. Food insecurity has increased by more than 1.5 over the years in Turkey.Öğe A Socioeconomic Analysis in Terms of Household Digital Technology Ownership(Sosyoekonomi Soc, 2023) Canatan, Behice; Ozbilge, Gokhan; Ipek, EgemenIn this study, individuals may be willing to have digital technology ownership for purposes such as employment, personal development, and/or e-commerce, as well as their income and sociodemographic characteristics. In this direction, the study aims to investigate the effects of preferred technology applications in the household and income and sociodemographic factors that impact digital technology ownership in Turkiye. For this purpose, Turkstat 2021 Household Information Technologies Usage Research Micro Data Set and generalised ordered logit method were used. The findings indicate that more than income alone is needed to expand digital technology ownership, and related factors such as e-commerce, e-skills, and online course taking should also be addressed.Öğe Revealed Preferences Theory: An Experimental Approach(Sosyoekonomi Soc, 2021) Ipek, Ozlem; Akyazi, HaydarIn this study, the validity of the revealed preference axioms is tested by experimental data using non-parametric methods. In the experimental setup established to determine the preference structures of the consumers under different price and quantity scenarios, the subjects are asked to choose between two goods first and then eight different goods representing the multi-goods situation under different budgets. The results of the experiments show that, for both scenarios, all of the 107 people who participated in the experiment provided the GARP axiom and the WARP and SARP axioms. This result indicates that the preferences of all subjects consistent with the revealed preferences theory, which means that the subjects have rational preferences.Öğe The Impact of Carbon Emissions on Corporate Cost of Debt (COD): A Research on Borsa İstanbul (BIST) Sustainability Index(Sosyoekonomi Soc, 2024) Ozsahin-Koc, Filiz; Deran, AliThis study examines the influence of carbon emissions of companies traded on the BIST Sustainability Index on the cost of debt for 2017-2021. In other words, the study aims to guide decisionmakers towards carbon emissions reduction by showing a significant impact between the cost of debt and carbon emissions. The data were obtained from the Public Disclosure Platform, companies ' financial statements, annual reports, sustainability reports, integrated reports, and the DataStream database and were subjected to statistical analysis. Panel data pooled OLS method was used in the study. The study found a significant impact of total carbon emissions, carbon emission intensity, leverage, and structure variables on the cost of debt. However, it was concluded that the size, return on assets, growth, and cash flow variables did not significantly impact the cost of debt.Öğe Predictive equivalent consumption minimization strategy for power-split hybrid electric vehicles using Monte Carlo algorithm(Gazi Univ, Fac Engineering Architecture, 2023) Gul, Merve Nur; Yazar, Ozan; Coskun, Serdar; Zhang, Fengqi; Li, Lin; Kaya, Irem ErsozPurpose: The underlying research goal of this article is to put forward a reliable fuel saving performance based on the forecasted velocities of drive cycles for a power-split hybrid electric vehicle. Theory and Methods: The power distribution between energy sources is devised by utilizing the P-ECMS for the power-split hybrid electric vehicle using the uncertain drive cycle velocity estimation based on MC algorithm. Results: The effectiveness and accuracy of the method are evaluated under seven drive cycles. The MC provides good prediction results of the velocities. On the basis of it, the P-ECMS method decreases fuel consumption up to 6.01% under NEDC, up to 9.09% under WLTP, up to 6.33% under UDDS, up to 5.14% under HWFET, up to 1.96% under NYCC, up to 11.47% under LA-92, and up to 7.92% under ALL-CYC compared to a standard ECMS method. Conclusion: It is seen from the analysis results that battery SOC decreases slightly using the P-ECMS since the electric motor is actively used to meet power demand instead of the engine over the predicted speed profiles. In the end, the MC algorithm-based P-ECMS strategy can verify the optimal power distribution based on fuel-saving potentials as compared to the baseline ECMS strategy while keeping the battery SOC at a reasonable interval.Öğe Improving the BER and PAPR performances of conventional OFDM waveform with sequential LLWT-PTS-AC method(Gazi Univ, Fac Engineering Architecture, 2024) Tengizler, Bekir; Caliskan, Efe Kaan; Gulbaz, Alihan; Ozen, AliPurpose: In this study, it is suggested to combine PTS and AC methods with LWT transform using Lazy wavelet to reduce PAPR in wireless communication systems using classical OFDM waveform. A new method combining the PAPR improvement provided by PTS and AC techniques on multi-carrier Communication systems and the BER performance provided by LWT is presented in this study. Theory and Methods: The proposed method is given in Figure A. In Figure A, randomly generated serial input data is modulated in the M-Ary Modulation Block. It is then propagated by applying the inverse Lifting wavelet transform to the data modulated in the ILWT Block. Next, in the PTS Block, the phases of emittedsymbols are changed. Then the phase-changed signals are subjected to IFFT processing. After the IFFT process, the signal with the lowest PAPR value is selected and transmitted to the AC Block by adding CP in the CP+ Block. The produced waveform after clipping processes in the AC Block is sent from the frequency selective channel and reaches the receiving side after the AWGN is distorted. The desired performance criteria are calculated by using the data obtained at the output of the M-Ary De-Modulation Block by applying the opposite of the operations on the transmitter side on the receiver side. Results: When the obtained PAPR results are analyzed, it is understood that the suggested waveform for the 1E-3 PAPR value is 0.5 dB better than the PTS-AC-OFDM waveform and 8 dB better than the K-OFDM waveform. In addition, when the BER performances are examined, it is observed that the suggested waveform for the 1E-4 BER level is 6 dB better than the PTS-AC-OFDM and K-OFDM waveforms. Conclusion: In this article, significant gains were obtained in both BER performances and PAPR performances thanks to the proposed method. Thus, despite the slightly increased computational complexity, the proposed LLWT-PTS-AC-OFDM method has yielded a high-performance next-generation OFDM waveform in this study.Öğe A novel optical OFDM waveform design for visible light communication system(Gazi Univ, Fac Engineering Architecture, 2024) Maras, Meryem; Ozen, AliIn this study, a new spread-based optical OFDM waveform is proposed for IM/DD communication systems. The proposed waveform is a combination of the spreading technique and the Flip OFDM waveform. Simulation studies are carried out to evaluate the performance of the proposed s-Flip-OFDM waveform and compare it with optical OFDM waveforms such as Flip OFDM, DCO-OFDM and VLC-OFDM. Figure A. The block diagram of the proposed spread optical OFDM waveform Purpose: The aim of this study is to combine optical OFDM waveforms with the spreading technique previously used in RF systems. The use of the spreading technique in the Flip-OFDM waveform, one of the multi-carrier optical wireless communication schemes, and in other optical OFDM waveforms such as DCO-OFDM and VLC-OFDM is proposed this study for the first time in the literature. Theory and Methods: The transmitter-receiver block diagram of the optical OFDM system using the proposed spreading method is shown in Figure A. In the transmitter side of the optical OFDM system shown in Figure A, randomly generated serial input data is subjected to propagation in the Spreading Block. The spreaded data is then modulated with BPSK modulation in the M-ary Modulator Block. The desired optical OFDM data packets are then generated in the Optical OFDM Modulator Block. In this study, Flip-OFDM waveform, one of the most important optical OFDM waveforms in the literature, is used. The generated flip OFDM data packets are transmitted via LEDs over a multipath fading optical channel and reach to the receiver after being corrupted by additive white Gaussian noise (AWGN). After the distorted signals reaching the receiver are restored with appropriate time domain or frequency domain equalizers, the reverse process is applied at the transmitter to obtain the signals decided at the output of the M-ary De-ModulatorBlock. Finally, the desired performance metrics such as BER and PAPR are calculated using the de-spreading data. Results: When the obtained simulation results are analyzed, from the numerical results, it is observed thatthe spreading technique provides SNR gains in the range of 5 to 10 dB to the performance of optical OFDM waveforms. It is found that the proposed s-Flip-OFDM waveform is approximately 10 dB better than the s-DCO-OFDM waveform and 15 dB better than the s-VLC-OFDM waveform in AWGN channel environment and diffuse multipath optical channel environments. Conclusion: In this article, significant gains were obtained in BER performances in all optical channel environments thanks to the proposed method. The hardware complexity of the proposed waveform is negligible compared to other waveforms. It can be concluded that the proposed s-Flip OFDM waveform may be one of the best waveform schemes for optical wireless communication systems for future 6G and beyond applicationsÖğe A bicriteria approach for the semi-desirable facility location problem(Gazi Univ, Fac Engineering Architecture, 2024) Duran, Fatma Ersoy; Ozturk, Diclehan TezcanerSemi-desirable facilities have both desirable and undesirable effects on the demand points in their vicinity, which necessitates them to be located both close to and far away from those points. In this study, a bi-objective semi-desirable facility location problem with both desirable and undesirable effects is considered. The first objective minimizes the total transportation cost between the facility and the demand points and tends to locate the facility closer to these points. Assuming that the transportations are made on road maps, the rectilinear distance metric is used to compute the first criterion. The second objective function minimizes the maximum undesirable effect of the facility on the demand points, and it thus tends to locate the facility farther from the demand points. The undesirable effect of the facility on a demand point is represented with a function based on the distance between them. The undesirable effect stays constant within a close proximity of the facility, beyond this proximity it decreases linearly and becomes zero. Assuming that the undesirable effects spread radially from the facility, the Euclidean distance metric is used to compute the second criterion. We first develop a mixed integer nonlinear programming model for the problem. As a second approach, the Big Square Small Square (BSSS) algorithm that searches for a solution by dividing the solution area into sub-regions is adapted to the problem. A mathematical model with low computational requirements is developed to effectively evaluate whether there is an efficient solution in the sub-regions or not. The approach is demonstrated on two large problem instances, in which efficient solutions are obtained quickly by reducing the solution area.Öğe A comparison of tree data structures in the streaming data clustering issue(Gazi Univ, Fac Engineering Architecture, 2024) Senol, Ali; Kaya, Mahmut; Canbay, YavuzProcessing streaming data is a challenging issue because of the limitation of time and resources. Clustering data streams is an efficient technique to analyze this kind of data. This study proposes two new streaming data clustering algorithms, BT-AR Stream and VP-AR Stream, inspired by the KD-AR Stream clustering algorithm [32]. Our algorithms used Ball-Tree and Vintage Tree data structures instead of KD-Tree. To reveal the efficiency of the proposed algorithms, we tested the algorithms on 18 benchmark datasets in terms of clustering qualities and runtime complexities. Then we compared obtained results with the results of the KD-AR Stream algorithm. According to the results, the BT-AR Stream algorithm was the most successful in terms of clustering quality and runtime complexity, as illustrated in Figure A.Purpose: This study aims to analyze and compare the efficiency of tree data structure in data stream clustering issues. We aim to reveal the efficiency of tree data structures in both clustering quality and runtime performance.Theory and Methods: To compare the efficiency of tree data structures in data stream clustering, we proposed two stream clustering algorithms inspired by KD-AR Stream. For this reason, we used Ball-Tree and Vintage-Tree data structures instead of KD-Tree and proposed two new stream clustering algorithms named BT-AR Stream and VP-AR Stream. To compare the success of algorithms, we tested them on 18 benchmark datasets and compared them in aspects of clustering quality and runtime complexity.Results: According to the results obtained in the experimental study, the BT-AR Stream algorithm, which uses Ball-Tree, was the most successful in both clustering quality and runtime complexity on the KDD, which is a high-dimensional dataset. On the other hand, the clustering quality of all algorithms was good on the other datasets. Conclusion: Although the clustering quality of all three algorithms was good, the BT-AR Stream algorithm was the most successful because KDD is high-dimensional. Furthermore, it is the fastest algorithm compared to the others.Öğe Effect of operating parameters on the performance of rotary desiccant wheel energized by PV/T collectors(Yildiz Technical Univ, 2023) Olmus, Umutcan; Guzelel, Yunus Emre; Cerci, Kamil Neyfel; Buyukalaca, OrhanThe main energy input of a desiccant air conditioning system is the low-quality thermal energy required for regeneration, which can be obtained from waste heat, geothermal resources or solar energy. Regeneration thermal energy can be produced as well as energizing components such as fans, pumps, auxiliary air heaters, and control elements of the system by using photovoltaic-thermal solar collectors (PV/T). In this study, parametric analyzes were performed to investigate the effect of regeneration temperature and air frontal velocity on the temperature and dehumidification performance of a solid silica-gel desiccant wheel and on the water-cooled PV/T collectors used to provide the regeneration thermal energy. The regeneration temperature was varied between 50 and 70 degrees C, and air frontal velocity between 1.3 and 4.1 m/s. The analyzes show that the dehumidification efficiency increases from 13.94% to 33.04% as regeneration temperature increased from 50 degrees C to 70 degrees C at 1.3 m/s air frontal velocity at which dehumidification efficiency is maximum. At 4.1 m/s air frontal velocity, the required regeneration thermal energy is maximum and increases from 49.64 kW to 132.48 kW at the same regeneration temperature change. The low regeneration temperature resulted in desirable latent performance and undesirable sensible heat transfer performance in DEW. Finally, considering the whole system, it was concluded that the optimum regeneration air temperature for the performance parameters is 60 degrees C.Öğe Investigation of ignition advance effects for CNG usage in a sequential dual ignition gasoline engine by using in-cylinder combustion cfd analysis(Gazi Univ, Fac Engineering Architecture, 2019) Yontar, Ahmet Alper; Dogu, YahyaIn this study; for a sequential dual ignition gasoline engine, the effects of ignition advance on engine characteristics and in-cylinder flame propagation have been numerically investigated for CNG usage with an in-cylinder combustion model. A CFD model for a single cylinder of the four-cylinder Honda L13A4 i-DSI engine with a sequential dual spark ignition is constructed in STAR-CD software for CNG usage by considering all components related to the combustion chamber (intake-exhaust manifold connections, intake-exhaust valves, cylinder, cylinder head, piston, spark-plugs, etc.). By using the CFD analyses for CNG usage, the optimum ignition advance is determined for the prescribed engine operating conditions of 3000-rpm engine speed, 10.8:1 compression ratio, and 1.2 air-fuel ratio. Analyzes are performed by varying the ignition advance in a wide range (60 degrees-10 degrees CAD and 55 degrees-5 degrees CAD ignition advance for the lst-2nd spark plugs, respectively). For engine operating conditions examined, it has been determined that the 30 degrees-25 degrees CAD advance value for the 1st-2nd spark plug from the top dead point is the optimum ignition advance in terms of engine performance and emission balance. For CNG, ignition advances have increased compared to gasoline. The in-cylinder flame propagation is visualized and evaluated for all investigated conditions.
