Scopus İndeksli Yayınlar Koleksiyonu

Bu koleksiyon için kalıcı URI

https://hdl.handle.net/20.500.13099/3

Listeleniyor 1 - 20 / 1151

Mechanical and Tribological Performance of Polypropylene/Tin Powder Composites
(Natl Inst Science Communication-Niscair, 2022) Gulesen, Mustafa; Yetgin, Salih Hakan; Unal, Huseyin
In this study, the effect of Tin powder filler content on the mechanical and tribological performance of Tin filled Polypropylene (PP) composites were investigated. Polypropylene composites were prepared in a Brabender kneading chamber. The melt was transferred to a laboratory hot press and compression molded into samples for tests. The mechanical performances of the polymer based composites were determined by tensile and notched izod impact tests. The tribological tests were carried out in dry condition using pin-on-disc at 0.5-1.5 m/s Sliding Speed (SS) and 10-30 N loads. The mechanical test results demonstrated that the incorporation of Tin powders increased the Tensile Strength (TS) (5.6%), tensile modulus (TM) (19.8%) and izod Impact Strength (IS) (41.8%) while decreased the Elongation at Break (EB) (80%) values of Tin powder filled PP composites. The Friction Coefficient (COF) and Specific Wear Rate (SWR) decreased with the increase in filler content. The COF of unfilled PP, PP-8% Tin powder, PP-16% Tin powder and PP-24% Tin powder composites decreased about 20%, 23.4%, 21.8% and 29.3% with the increase in applied load from 10 N to 30 N. The SWR of the Tin powder filled PP composites decreased by 91% compared to unfilled PP polymer at 1.5 m/s speed and 30 N load value.
Novel Schiff Base Sulfonate Derivatives as Carbonic Anhydrase and Acetylcholinesterase Inhibitors: Synthesis, Biological Activity, and Molecular Docking Insights
(Wiley-V C H Verlag Gmbh, 2025) Yasar, Umit; Demir, Yeliz; Gonul, Ilyas; Ozaslan, Muhammet Serhat; Celik, Gizem Gumusgoz; Turkes, Cuneyt; Beydemir, Sukru
Sulfonate derivatives are an essential class of compounds with diverse pharmacological applications. This study presents the synthesis and detailed characterization of six novel Schiff base sulfonate derivatives (L1-L6) through spectroscopic techniques (FT-IR and NMR). Their inhibitory potential was evaluated against human carbonic anhydrase isoenzymes (hCA I and hCA II) and acetylcholinesterase (AChE), which are crucial therapeutic targets for diseases such as glaucoma, epilepsy, and Alzheimer's disease. The KI values for the compounds concerning AChE, hCA I, and hCA II enzymes were in the ranges of 106.10 +/- 14.73 to 422.80 +/- 17.64 nM (THA: 159.61 +/- 8.41 nM), 116.90 +/- 24.40 to 268.00 +/- 35.84 nM (AAZ: 439.17 +/- 9.30 nM), and 177.00 +/- 35.03 to 435.20 +/- 75.98 nM (AAZ: 98.28 +/- 1.69 nM), respectively. Molecular docking analyses revealed key interactions within the active sites of the enzymes, including hydrogen bonding with critical residues and pi-pi stacking interactions. Notably, L3 demonstrated superior inhibition against hCA I (KI: 116.90 +/- 24.40 nM) and AChE (KI: 106.10 +/- 14.73 nM), positioning it as a promising lead compound. This comprehensive investigation contributes to the development of isoform-specific inhibitors for therapeutic use and provides valuable insights into their binding mechanisms. The findings underscore the potential of Schiff base sulfonates as scaffolds in drug discovery for neurodegenerative and metabolic disorders.
Onosma rutila (Boraginaceae) Plant Extract: Chemical Composition, Biological Analysis, and Film Forming Potential With Polymers
(Wiley-V C H Verlag Gmbh, 2025) Binzet, Riza; Binzet, Gun; Turunc, Ersan; Cevik, Pinar Kuce; Demir, Didem; Arslan, Hakan
This study aimed to integrate the ethanolic extract obtained from the aerial parts of endemic Onosma rutila as a new bioactive ingredient into polymeric films and to produce biofunctional composite thin films for use in biomedical applications. Initially, the definition of the plant extract was carried out in terms of chemical composition and biological activities. The main component of the extract was revealed as 9,12-octadecadienoic acid (15.90%). Antimicrobial activity was evaluated against a total of five microorganisms by the well diffusion method and microdilution technique. MIC99 results showed the lowest inhibition against Candida albicans, suggesting a stronger antifungal effect than antibacterial activity. Also, the 2,2-diphenyl-1-picrylhydrazyl scavenging activity of O. rutila, ascorbic acid, and butylated hydroxytoluene at 500 mu g/mL showed values of 87.63, 90.13, and 46.82%, respectively. In the next phase, the extract, which was revealed to be an effective biological agent, was incorporated into the polymer solutions prepared based on chitosan and polyvinyl alcohol at different ratios to produce a series of thin films. For application purposes, the thin films' chemical compositions, water retention capacities, and morphological properties were determined and their potential for use as wound dressing material was evaluated.
ANDClust: An Adaptive Neighborhood Distance-Based Clustering Algorithm to Cluster Varying Density and/or Neck-Typed Datasets
(Wiley-V C H Verlag Gmbh, 2024) Senol, Ali
Although density-based clustering algorithms can successfully define clusters in arbitrary shapes, they encounter issues if the dataset has varying densities or neck-typed clusters due to the requirement for precise distance parameters, such as eps parameter of DBSCAN. These approches assume that data density is homogenous, but this is rarely the case in practice. In this study, a new clustering algorithm named ANDClust (Adaptive Neighborhood Distance-based Clustering Algorithm) is propoesed to handle datasets with varying density and/or neck-typed clusters. The algorithm consists of three parts. The first part uses Multivariate Kernel Density Estimation (MulKDE) to find the dataset's peak points, which are the start points for the Minimum Spanning Tree (MST) to construct clusters in the second part. Lastly, an Adaptive Neighborhood Distance (AND) ratio is used to weigh the distance between the data pairs. This method enables this approach to support inter-cluster and intra-cluster density varieties by acting as if the distance parameter differs for each data of the dataset. ANDClust on synthetic and real datasets are tested to reveal its efficiency. The algorithm shows superior clustering quality in a good run-time compared to its competitors. Moreover, ANDClust could effectively define clusters of arbitrary shapes and process high-dimensional, imbalanced datasets may have outliers. This study proposes a new clustering algorithm named ANDClust to handle datasets with varying density and neck-typed clusters. In the proposed algorithm, an Adaptive Neighborhood Distance (AND) ratio is used to weigh the distance between the data pairs as if it differs for each data pair in the dataset. This method makes the approach support not only the varying density among clusters but also the varying density inside the cluster. image
MENTAL FATIGUE EXPERIENCES OF RESIDENT PHYSICIANS
(Nobel Ilac, 2024) Yilmaz, Necla; Yildiz, Ebru; Kutuk, Hacer Aksoy; Guvenc, Fatmanur; Celik, Omer; Kucuk, Feyza; Parlak, Seyma
Objective: This research aims to reveal the mental fatigue experiences of resident physicians while practicing their profession. Material and Method: The study was carried out with the phenomenology design, which is considered within the scope of qualitative research. Participants were reached using the homogeneous sampling technique, which is one of the purposive sampling techniques. In this context, in-depth interviews were conducted using semi -structured forms with 10 resident physicians continuing their residency training in Turkey. The data obtained by transcribing the interviews were subjected to interpretive phenomenological analysis. The data obtained were coded and gathered under themes to make the phenomenon of mental fatigue meaningful. Results: In this study, which examines the mental fatigue experienced by assistant physicians while performing their profession as a whole, it has been determined that the causes of mental fatigue are related to working life, academic life, professional life, psychological, systemic and physiological reasons. At the same time, it has been determined that the mental fatigue experienced by assistant physicians causes some individual consequences such as stress, anxiety, focusing problems, and burnout, and some social consequences such as social adaptation problems, negative effects on the patient, and difficulty in the diagnosis process. Conclusion: This study, which reveals the causes and consequences of mental fatigue experienced by resident physicians, has concluded that this situation not only has individual consequences on the physician but also causes some social consequences such as difficulty in the diagnosis process, social adaptation problem and the negative effects of this situation on the patients. To minimize this effect, it is recommended to clarify the job description of resident physicians, reduce the patient burden by shortening long working hours, and make necessary legal and systemic regulations on the subject.
INVESTIGATING THE IMPACT OF USING MAGNETIC-TYPE NANOFLUID ON THE THERMAL PERFORMANCE OF A SOLAR WATER COLLECTOR WITH HELICALLY COILED TUBE ABSORBER
(Begell House Inc, 2024) Aytac, Ipek; Tuncer, Azim Dogus; Variyenli, Halil Ibrahim; Khanlari, Ataollah; Satay, Ebru
In recent years, solar water collectors are commonly preferred for supplying heated water to be utilized in various processes. In the present study, a solar water collector equipped with a helically coiled absorbing surface has been manufactured and experimented under various working conditions to determine its general behavior. The main goal of using a helically coiled absorber is enhancing energy harvest in the collector by ensuring vertical angle between the absorbing area and incident radiation. In addition, for providing greater increase in thermal efficiency, magnetic type nanofluid has been used as a working fluid. In this context, NiFe(2)O(4 )nano-sized particles have been mixed with water at the ratio of 2% (wt./wt.). Accordingly, the performance of the collector has been empirically examined using both water and magnetic nanofluid at two different flow rates. The overall results of the present survey exhibited successful use of magnetic type nanofluid in a solar collector equipped with a helically coiled absorbing surface. Utilizing magnetic nanofluid in the collector as circulating fluid raised the thermal efficiency on an average of 20.29% and 23.59% at volumetric flow rates of 0.5 lpm, and 0.9 lpm, respectively. Moreover, utilizing NiFe2O4/water nanofluid in the water collector enhanced the exergy efficiency on an average of 44.53% and 40.04% at volumetric flow rates of 0.5 lpm and 0.9 lpm, respectively.
AN EXPERIMENTAL INVESTIGATION TO PREDICT OPTIMUM CHARGE OF A HEAT PUMP SYSTEM
(Begell House Inc, 2023) Afshari, Faraz; Khanlari, Ataollah; Tuncer, Azim Dogus; Soezen, Adnan
Working principles of heat pumps is an important matter from a thermodynamic point of view that has been researched from various aspects. In this study, undercharged, optimum charged, and overcharged conditions of a heat pump were investigated using R134a refrigerant. Variations in temperature, pressure, and the coefficient of performance have been evaluated and it was aimed to find out the optimum charge condition considering different parameters. According to the experimentally obtained findings, the coefficient of performance was increased by more than three times when the refrigerant amount increased from 2000 g to similar to 7300 g. The general outcomes of the present study indicated that optimum refrigerant charge amount can notably affect the performance of heat pump apparatus. It was shown that the P-h diagram of all heat pump systems depends on the working conditions and the refrigerant charge is a very important criterion that can make significant changes in the P-h diagram. It was found that, by increasing refrigerant charge, after the downtrend starts in the compressor inlet temperature, 20% refrigerant can be added to achieve the maximum COP value. Additionally, the critical point in expansion valve outlet temperature was used to find the optimum charge. It was revealed that if 140% refrigerant is added to the given refrigerant at critical point, the optimum COP value can be achieved.
PASSIVE THERMAL MANAGEMENT OF PHOTOVOLTAIC PANEL BY USING PHASE CHANGE MATERIAL-FILLED ALUMINUM CANS: AN EXPERIMENTAL STUDY
(Begell House Inc, 2022) Tuncer, Azim Dogus; Khanlari, Ataollah; Aytac, Ipek; Ciftci, Erdem; Sozen, Adnan; Variyenli, Halil Ibrahim
In the recent years, researches are focused on improving the efficiency of photovoltaic (PV) panels by cooling panel surface utilizing different methods. In this work, paraffin wax-filled aluminum beverage cans have been utilized to improve the performance of photovoltaic panels. The main aims of this study are reutilizing waste materials in solar systems and increasing the performance of a PV panel by employing an unconventional approach. Modified and unmodified PV panels have been experimentally investigated simultaneously to observe and compare their performances. Experimentally attained outcomes showed that electrical efficiency was upgraded from 70.69% to 72.60%. Moreover, normalized power output efficiency was (round as 61.72% and 71.56%, respectively, for unmodified and modified PV systems. In addition to the electrical performance investigation, an exergy analysis has been performed and mean exergy efficiency values for conventional and modified PV panels were found as 2.26% and 5.73%, respectively. General outcomes of this study showed successful utilization of paraffin wax -filled aluminum cans as a thermal management and efficiency improvement technique in photovoltaic systems.
NUMERICAL INVESTIGATION OF THERMAL PERFORMANCE ENHANCEMENT POTENTIAL OF USING Al2O3-TiO2/WATER HYBRID NANOFLUID IN SHELL AND HELICALLY COILED HEAT EXCHANGERS
(Begell House Inc, 2022) Gungor, Alper; Sozen, Adnan; Khanlari, Ataollah
Shell and helically coiled tube heat exchangers (SHCTHEXs) are a special type of shell-and-tube heat exchangers and they are widely used in industry in many processes. The tubes inside the shell are curved to form a helical coil which has a positive impact on heat transfer. The main purpose of this study is to investigate thermal performance enhancement potential of using a new type of hybrid nanofluid in SHCTHEXs. In this study, two types of SHCTHEXs - one vertically oriented and the other horizontally oriented - have been designed with the same geometrical dimensions. These designs have been simulated with two types of fluid on the shell side: water and Al2O3-TiO2/water hybrid-type nanofluid at various shell-side flow rates in order to reveal the heat transfer improvement potential of using this hybrid nanofluid in SHCTHEXs. The simulations indicated that utilizing Al2O3-TiO2/water hybrid-type nanofluid on the shell side resulted in 7.7% increase in the average heat transfer rate for vertically oriented SHCTHEX and 9% increase for the horizontally oriented SHCTHEX. Calculated heat transfer rate values ranged between 3337 and 5136 W. Among the simulated designs the best performing combination has been horizontally oriented SHCTHEX with Al2O3-TiO2/water hybrid-type nanofluid on the shell side. This combination provided 2.5 degrees C better cooling at the hot fluid outlet compared to poorest performing combination: vertically oriented SHCTHEX with water (both streams at 3 lpm). Using nanofluid increased the overall heat transfer coefficient parameter in horizontally and vertically oriented heat exchangers as 17.2% and 13.7%, respectively. The achieved outcomes of this work indicate that utilizing an Al2O3-TiO2/water hybrid nanofluid provides a notable amount of increase in heat transfer rate. In addition, overall results of the study showed that horizontally oriented SHCTHEX had better performance in comparison with vertically oriented one.
THE RELATIONSHIP BETWEEN COVID-19 PERCEIVED RISK AND ATTITUDES TOWARDS COVID-19 VACCINATION IN HEALTHCARE PROFESSIONALS: AN EXAMPLE OF EASTERN TURKEY
(Medicinska Naklada, 2021) Sonmez, Tugce; Yarah, Suheyla; Turan, Gulcan Bahcecioglu
Bacground: This study aimed to examine the relationship between COVID-19 perceived risk and attitudes towards COVID-19 vaccination in healthcare professionals. Subjects and methods: This cross-sectional descriptive study included a total of 580 healthcare professionals. Results: The healthcare professionals' COVID-19 Perceived Risk Scale (CPRS) and Attitudes towards COVID-19 Vaccine Scale (ATV-COVID-19) mean scores were 31.3615.16 and 3.0010.61, respectively. A statistically significant negative correlation was found between their CPRS and ATV-COVID-19 mean scores. Conclusions: The healthcare professionals had a high COVID-19 perceived risk and moderately positive attitudes towards COVID-19 vaccine.
Celebrity Endorsement on Gender-Based Conspicuous Consumption
(Gadjah Mada Univ, Master Management Program, Fac Economics & Business, 2025) Tor-Kadioglu, Cansu; Bozyigit, Sezen
This study explores the irrational aspects of consumer behavior, focusing on conspicuous consumption driven by the pursuit of status and self-expression. It examines how consumers emulate celebrities based on key dimensions of celebrity endorsement- attractiveness, expertise, and credibility-and how these factors vary between genders. The research presents a conceptual framework that integrates conspicuous consumption with celebrity endorsement dimensions, supported by an extensive literature review. Data were collected from 403 participants belonging to the Y and Z generations through online surveys and analyzed using SPSS and AMOS software. The results reveal gender-specific differences in the influence of celebrity endorsement dimensions on conspicuous consumption. For female consumers, celebrity attractiveness and credibility significantly enhance conspicuous consumption, whereas expertise has a mitigating effect. In contrast, male consumers are primarily influenced by celebrity attractiveness. The study concludes that the allure of celebrities, as reflected in their attractiveness and credibility, promotes conspicuous consumption, while their expertise can diminish it. These findings provide valuable insights for businesses leveraging celebrity endorsements, particularly in gender-targeted marketing strategies, highlighting the importance of tailoring approaches based on consumer gender to maximize impact.
COMPARISON OF THE FEAR LEVELS AND SLEEP PROBLEMS OF NURSES WORKING IN WARDS WHERE PATIENTS WITH AND WITHOUT COVID-19 ARE HOSPITALIZED: A STUDY FROM TURKEY
(Medicinska Naklada, 2021) Celik, Asli Sis; Sonmez, Tugce
Background: This study was carried out to compare the fear levels and sleep problems of nurses working in wards where patients with COVID-19 are hospitalized and nurses working in wards without COVID-19 patients. Subjects and methods: This descriptive, cross-sectional research was conducted on 211 nurses using a web-based online survey in Turkey (including 104 nurses working in wards where patients with COVID-19/107 nurses working in wards where patients without COVID-19). Results: When the COVID-19 Fear Scale mean scores of the nurses working in wards where patients with/without COVID-19 were compared, it was determined that the difference between the groups was statistically significant (p<0.05). When the sleep problems experienced were compared according to the Post-Sleep Inventory, it was determined that the difference between the groups was not statistically significant (p>0.05). There was a moderately significant and positive correlation between the nurses' mean scores for the COVID-19 Fear Scale and Post-Sleep Inventory. Conclusions: It was determined that as the fear levels of nurses increased, they experienced more sleep problems.
Handling Quality-Oriented Tuning Procedure of a Dynamic Inversion Control Law via a Robust Control Technique
(Amer Inst Aeronautics & Astronautics, 2024) Resit, Demirkiran; Hasan, Isci; Ercument, Turkoglu
The robustness of a flight control law has played an important role. Designers can achieve this objective by using different techniques; however, if the target platform has a wide range of the flight envelope and desired behavior is demanding (e.g., fighter aircraft), completing a robust design becomes a challenging task while requested high performance capability. Using both the dynamic inversion philosophy and robust control design methodology can be a good choice in terms of meeting the essential requirements of flight control law design. Enhancing the handling qualities while not losing robustness is a common trade-off in the classic a flight control law development process. In order to improve the handling quality, tuning the feed-forward term instead of feedback terms is a valuable approach to preserve the robustness of the closed loops. Tuning procedure according to the proposed idea is explained in detail throughout the paper. The control design steps and the results of comprehensive set of stability, robustness and handling qualities by considering the proposed flight control law with additional terms are addressed. Besides, the achieved entire results indicate that the requirements of stability, handling qualities, and robustness is met by offered control law development strategies.
THE COSTS OF MEDICAL CARE FOR COVID-19 PATIENTS: A CASE STUDY IN TURKEY
(Australian Coll Health Service Management, 2021) Teker, Cenk; Cavmak, Dogancan; Avci, Hakan
OBJECTIVE: This study aims to calculate the medical costs of Covid-19 patients for hospitals based on the severity of clinical care. DESIGN: The study was conducted in a hospital in Istanbul/Turkey. A micro-costing approach was performed using historical cost data for one year. All direct and indirect medical inputs were determined in quantities and monetary values for four types of Covid-19 patients in the hospital. RESULTS: The analysis calculated the unit cost of an outpatient to be 459,99 , while the cost per day for inpatient to be 1.184,63 , for non-intubated in intensive care unit to be 1.938,11, for intubated in the intensive unit to be 2.393,99. The study also indicates that the total cost of a non-intubated patient in intensive care units is 1,54 times higher than the total cost per inpatient. An intubated patient's cost is 2,08 times higher than an inpatient's cost. CONCLUSION: This study indicates that Covid-19 patients incur significantly high costs for hospitals. The findings of the study provide empirical data for different types of patients which can be used in clinical management and can help all related governing bodies to plan their actions and make the decisions.
EXPERIMENTAL ANALYSIS OF A QUADRUPLE-PASS SOLAR AIR HEATER WITH EXTENDED HEAT TRANSFER SURFACES AND NANO-ENHANCED ABSORBER COATING
(Begell House Inc, 2023) Khanlari, Ataollah; Tuncer, Azim Dogus
In recent years, selective solar absorber surface coating applications have become quite popular in terms of enhancing the thermal performance of solar-thermal systems. Generally, nano-sized particles with high thermal conductivity values are preferred to be utilized in this type of modifications. In this study, nanoparticle-enhanced absorber coating material was applied to a quadruple-pass solar air heater to improve the thermal performance. In this regard, copper oxide nanoparticles with 38-nm average particle size and 32.9 W/m K thermal conductivity were mixed with industrial matte-black paint (2% wt./wt.). The obtained mixture was then applied to the heater and the developed heater has been experimented at three flow rate values. Embedding nanoparticles to the pure paint improved the average thermal conductivity as 0.033 W/m K (from 0.6392 W/m K to 0.6722 W/m K). According to the experimentally attained outcomes, mean thermal efficiency values were obtained in the range of 71.27-79.63%. Improving the flow rate from 0.007 kg/s to 0.013 kg/s enhanced the sustainability index value from 1.1696 to 1.2123. Moreover, maximum instantaneous thermal efficiency was found to be 4.05% higher in comparison with the system without nano-enhanced modification which was tested in a previous work.
AN INTEGRATED FUZZY MULTI CRITERIA DECISION MAKING METHOD FOR SUSTAINABLE (GREEN) PACKAGING MATERIALS SELECTION: AN APPLICATION IN TURKEY
(Parlar Scientific Publications (P S P), 2020) Gulsun, Bahadir; Mic, Pinar
The packaging protects the products from external factors and often represents the product. To a decision-maker with inadequate knowledge about the structure and properties of a packaging material, it may be difficult to determine the most applicable one for a given product. In some cases, the defect levels can be so high that the choice of packaging material and other related units can make a product difficult to sell. This may leave the material's selector in a problematic situation. Although packages are mandated to protect the goods inside them, they also need to be easy to store and transport, while being attractive for the consumer market. To be sustainable, packaging waste must be kept at a minimum and should not require any additional cost to be destroyed. To mitigate this, recyclable material should also be evaluated during its construction phase. Considering these significant points, a method to select materials for sustainable packaging is proposed in this paper. In this approach, an integrated DELPHI and fuzzy-Preference Ranking Optimization Method for Enrichment Evaluations approach is employed. Numerical examples are specified in the paper to stimulate an improved understanding of the methodology used, and the experimental results are evaluated through a sensitivity analysis.
THERMAL ANALYSIS OF BI-DIRECTIONAL FUNCTIONALLY GRADED PLATES SUBJECTED TO HEAT GENERATION
(Begell House Inc, 2024) Yarimpabuc, Durmus; Eker, Mehmet; Yildirim, Ramazan
The two-dimensional steady-state heat transfer problem is analyzed under the most general boundary conditions in a heterogeneous environment. It is assumed that the internal heat generation varies arbitrarily in two directions, while the thermal conductivity coefficient of the material is bi-directly (thickness-length) graded with the Mori-Tanaka model. The linear inhomogeneous partial differential equations produced under these conditions may not be solved by conventional methods. The governing equation of the system is numerically solved with high accuracy using the 2D pseudospectral Chebyshev method. Benchmark problems are used to check the accuracy of the method. It has been observed that the effect of volumetric heat generation on the temperature distribution is more than the heat transmission coefficient. Besides, this method is simple and effective and can be easily applied to such problems.
APPLICATION OF SIMULATED ANNEALING ALGORITHM FOR THE MAGNETIC FILTRATION PROCESS
(Yildiz Technical Univ, 2019) Yildiz, Zehra; Yuceer, Mehmet
The optimization of the magnetic filtration processes parameters on the separation performance of corrosion particles from waste-water suspensions by magnetic filter have been discussed. By using the magnetic filter performance formulas presented in the literature, a base model for magnetic filter performance is selected and the magnetic filter cleaning coefficient is optimized by changing several selected filter process parameters. The magnetic field intensity, diameter of the matrix elements (balls), filter length and filtration velocity are chosen as the inputs parameters and cleaning coefficient as output parameter. The Simulated Annealing (SA) Algorithm was applied to the model. Four variables were successfully optimized.
A novel Flip-OFDM optical communication system based on lazy lifting wavelet transform for intensity modulated direct detection
(Natl Inst Optoelectronics, 2023) Temurtas, Sinem; Toprakci, Gamze; Ozen, Ali
In this article, a novel optical OFDM (LLWT Flip-OFDM) waveform based on Lazy Lifting wavelet transform (LLWT) is recommended to enhance the success of Flip-OFDM communication system, which is one of the optical OFDM methods used in visible light communication systems. In the proposed scheme, superior advantages of LWT transform such as ICI and ISI suppression capabilities because of its good time-frequency localization properties and orthonormal structure are utilized, unlike fast Fourier transform (FFT). In order to confirm the success of the proposed waveform through the bit error rate (BER) achievement benchmark, computer simulation studies are executed in the indoor multipath optical channel and underwater multipath optical channel environment. It is perceived from the acquired results that with the suggested LLWT Flip-OFDM communication scheme, 7.5 dB SNR gain is achieved against the Flip-OFDM communication system and 22.5 dB SNR improvement is performed versus the VLC-OFDM communication system.
INVESTIGATION OF MECHANICAL AND METALLOGRAPHIC PROPERTIES OF TWO DIFFERENT ALUMINUM ALLOYS JOINED WITH FRICTION STIR WELDING METHOD USING DIFFERENT WELDING PARAMETERS
(Yildiz Technical Univ, 2020) Ocalir, Seref; Esme, Ugur; Boga, Cem; Kulekci, Mustafa Kemal
In this study two aluminum alloy materials of EN AW-5083-H111 and EN AW-6082-T651 were joined with Friction Stir Welding considering the parameters as the tool shoulder diameter, spindle speed and feed rate. The mechanical properties of the weld joints such as yield strength, tensile strength and micro-hardness and metallographic properties were investigated comparatively with the use of these welding parameters. The yield strength of the weld joints were determined to be between 136-217 MPa while the tensile strengths were between 159-230 MPa and the percent elongations were between 2.28-5.44 %. The hardness values measured in weld areas were higher in the EN AW-6082 base metal side compared with EN AW-5083 base metal side.

Güncel Gönderiler