The relations between null geodesic curves and timelike ruled surfaces in dual Lorentzian space $\mathbb{D}_{1}^{3}$

Yasin \"{U}nl\"{u}t\"{u}rk,S\"{u}ha Y\i lmaz,Cumali Ekici 호남수학회 2019 호남수학학술지 Vol.41 No.1

In this work, we study the conditions between null geodesic curves and timelike ruled surfaces in dual Lorentzian space. For this study, we establish a system of differential equations characterizing timelike ruled surfaces in dual Lorentzian space by using the invariant quantities of null geodesic curves on the given ruled surfaces. We obtain the solutions of these systems for special cases. Regarding to these special solutions, we give some results of the relations between null geodesic curves and timelike ruled surfaces in dual Lorentzian space.

The effects of stiffener configuration on stiffened T-stubs

Yasin Onuralp Özkılıç 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.44 No.4

The stiffeners, also known as ribs, are utilized to increase the resistance of T-stubs. The author’s previous studies showed that stiffeners can increase plastic capacity by an average of 1.71 times. A combined experimental and numerical study was undertaken to examine the effects of the stiffener configuration on the behavior of T-stubs. A total of 20 stiffened T-stubs where the shape and angle of stiffeners were considered as the main parameters were tested under monotonic loading. Rectangular, triangular and AISC types of stiffener were tested under monotonic loading. The experimental results indicated that when the height of the stiffener is equal to or higher than the length of the stiffener, the shape of the stiffener does not have an influence on the behavior. A numerical study using the finite element tool ABAQUS was carried out in order to further investigate the effects of the stiffener shapes. In this case, the height is considered less than the length of the stiffener. Moreover, the shape of the stiffeners was investigated with the different thicknesses of the stiffener. The simulation findings revealed that when the height of the stiffener is less than the length of the stiffener, the shape of the stiffener significantly affects the plastic capacity. Based on the numerical and experimental results, it is recommended to use the triangular shape of the stiffener when height is equal to or higher than the length of the stiffener while it is recommended to utilize the rectangular shape of the stiffener when height is less than the length of the stiffener.

Effect of internal pressure and gas/liquid interface area on the CO mass transfer coefficient using hollow fibre membranes as a high mass transfer gas diffusing system for microbial syngas fermentation

Yasin, M.,Park, S.,Jeong, Y.,Lee, E.Y.,Lee, J.,Chang, I.S. Elsevier Applied Science 2014 Bioresource technology Vol.169 No.-

This study proposed a submerged hollow fibre membrane bioreactor (HFMBR) system capable of achieving high carbon monoxide (CO) mass transfer for applications in microbial synthesis gas conversion systems. Hydrophobic polyvinylidene fluoride (PVDF) membrane fibres were used to fabricate a membrane module, which was used for pressurising CO in water phase. Pressure through the hollow fibre lumen (P) and membrane surface area per unit working volume of the liquid (A<SUB>S</SUB>/V<SUB>L</SUB>) were used as controllable parameters to determine gas-liquid volumetric mass transfer coefficient (k<SUB>L</SUB>a) values. We found a k<SUB>L</SUB>a of 135.72h<SUP>-1</SUP> when P was 93.76kPa and A<SUB>S</SUB>/V<SUB>L</SUB> was fixed at 27.5m<SUP>-1</SUP>. A higher k<SUB>L</SUB>a of 155.16h<SUP>-1</SUP> was achieved by increasing A<SUB>S</SUB>/V<SUB>L</SUB> to 62.5m<SUP>-1</SUP> at a lower P of 37.23kPa. Practicality of HFMBR to support microbial growth and organic product formation was assessed by CO/CO<SUB>2</SUB> fermentation using Eubacterium limosum KIST612.

Effect of the GFRP wrapping on the shear and bending Behavior of RC beams with GFRP encasement

Yasin Onuralp Özkılıç,Lokman Gemi,Emrah Madenci,Ceyhun Aksoylu,İlker Kalkan 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.45 No.2

The need for establishing the contribution of pultruded FRP encasements and additional FRP wraps around these encasements to the shear strength and load-deflection behavior of reinforced concrete beams is the main motivation of the present study. This paper primarily focuses on the effect of additional wrapping around the composite beam on the flexural and shear behavior of the pultruded GFRP (Glass Fiber Reinforced Polymer) beams infilled with reinforced concrete, taking into account different types of failure according to av/H ratio (arch action, shear-tension, shear-compression and pure bending). For this purpose, nine hybrid beams with variable shear span-to-depth ratio (av/H) were tested. Hybrid beams with 500 mm, 1000 mm, and 1500 mm lengths and cross-sections of 150x100 mm and 100x100 mm were tested under three-point and four-point loading. Based on the testing load-displacement relationship, ductility ratio, energy dissipation capacity of the beams were evaluated with comprehensive macro damage analysis on pultruded GFRP profile and GFRP wrapping. The GFRP wraps were established to have a major contribution to the composite beam ductility (90-125%) and strength (40-75%) in all ranges of beam behavior (shear-dominated or dominated by the coupling of shear and flexure). The composite beams with wraps were showns to reach ductilities and strength values of their counterparts with much greater beam depth.

Theoretical insight into the structure-property relationship of mixed transition metal oxides nanofibers doped in activated carbon and 3D graphene for capacitive deionization

Yasin, Ahmed S.,Mohamed, Ahmed Yousef,Mohamed, Ibrahim M.A.,Cho, Deok-Yong,Park, Chan Hee,Kim, Cheol Sang Elsevier 2019 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.371 No.-

<P><B>Abstract</B></P> <P>Over the last two decades, the capacitive deionization (CDI) technique has been developed into a high performance, low-cost, and environmental-friendly desalination technology. The development of novel advanced nanostructures via the hybridization of diverse carbon materials to improve the performance of CDI technology has attracted considerable attention. In this study, the combination of graphene hydrogel and ZrO<SUB>2</SUB>-doped TiO<SUB>2</SUB> nanofibers as efficient dopants into activated carbon (AC), has been achieved through a simple electrospinning technique followed by a post annealing process. The strong interactions between the graphene hydrogel, nanofibers and AC were found to enhance the wettability as well as the electrical conductivity of the AC. The morphology and electrochemical performance of the as-synthesized composite were characterized by field-emission scanning electron microscopy (FE-SEM), Transmission electron microscopy (TEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). What’s more, the X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and synchrotron X-ray absorption structures (XAS) are performed to investigate the atomic and electronic structure of titania and zirconia in order to understand their phase stability. We observed the appearance of anatase structure of titania and cubic structure of zirconia after doping the AC and graphene hydrogel with the nanofibers. The water contact angle of the composite was examined and found to be less than 3°. The introduced nanocomposite showed high electrosorption capacity of 9.34 mg g<SUP>−1</SUP> at the initial solution conductivity of ∼100 μS cm<SUP>−1</SUP>, which is much higher compared to the other surveyed materials; these results should be attributed to its significant hydrophilicity, high specific capacitance, and reduced charge transfer resistance.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Unique three-dimensional graphene/mixed transition metal oxides modified activated carbon was prepared and characterized. </LI> <LI> The nanocomposite electrode shows low charge transfer resistance and high specific capacitance. </LI> <LI> Analysis of synchrotron-based hard X-ray absorption spectroscopy. </LI> <LI> The fabricated nanocomposite exhibits a high electrosorption capacity of 9.34 mg g<SUP>−1</SUP>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Gender Differences in Responses towards Anti-Smoking Messages and Policy Implementation among Future Doctors in Malaysia

Yasin, Siti Munira,Ismail, Nurhuda,Noor, Norizal Mohd,Azman, Mohd Shafiq Mohd,Taib, Hanisah,Jusop, Junainah Mat,Salaudin, Nur Atirah Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.1

Background: Medical students' views may provide some direction for future policy considerations. Aim: The aim of this study was to assess gender differences in future doctors' receptiveness to currently implemented anti-smoking messages and the effectiveness of those messages. Materials and Methods: We administered a questionnaire to all students at a medical university in Malaysia, asking how frequently they noted anti-smoking policies, anti-smoking campaigns, and anti-smoking messages in schools. In addition, the questionnaire investigated most effective methods to convey these messages. Results: A total of 522 (59.7%) students responded. Students were least likely to approve of total bans on cigarettes and increasing the price of cigarettes, and most likely to approve of bans on use of cigarettes in public places and sales to individuals less than 16 years old. Approval of total bans on cigarettes was more common in female students than in males OR=0.39 (95%CI: 0.18-0.86). Furthermore, compared to the female students, the male students thought that printed media; OR=2.32 (95%CI: 1.31-4.10), radio; OR=1.93 (95%CI: 1.15-3.22) and the internet; OR=1.96 (95%CI: 1.15-3.33) were very effective at delivering anti-smoking messages. Conclusions: Gender differences existed in the future doctors' perception of the effectiveness of anti-smoking initiatives. Taking this gender difference into account may increase the receipt of anti-smoking messages in adolescents.

THE RELATIONS BETWEEN NULL GEODESIC CURVES AND TIMELIKE RULED SURFACES IN DUAL LORENTZIAN SPACE D³₁

( Yasin Unluturk ),( Suha Yilmaz ),( Cumali Ekici ) 호남수학회 2019 호남수학학술지 Vol.41 No.1

In this work, we study the conditions between null geodesic curves and timelike ruled surfaces in dual Lorentzian space. For this study, we establish a system of differential equations characterizing timelike ruled surfaces in dual Lorentzian space by using the invariant quantities of null geodesic curves on the given ruled surfaces. We obtain the solutions of these systems for special cases. Regarding to these special solutions, we give some results of the relations between null geodesic curves and timelike ruled surfaces in dual Lorentzian space.

A new description of spherical images associated with minimal curves in the complex space $\mathbb{C}^{4}$

Yasin Unluturk,Suha Yilmaz 호남수학회 2022 호남수학학술지 Vol.44 No.1

In this study, we obtain the spherical images of minimal curves in the complex space in $\mathbb{C}^{4}$ which are obtained by translating Cartan frame vector fields to the centre of hypersphere, and present their properties such as becoming isotropic cubic, pseudo helix, and spherical involutes. Also, we examine minimal curves which are characterized by a system of differential equations.

A NEW MODELLING OF TIMELIKE Q-HELICES

( Yasin Ünlütürk ),( Cumali Ekici ),( Doǧan Ünal ) 호남수학회 2023 호남수학학술지 Vol.45 No.2

In this study, we mean that timelike q-helices are curves whose q-frame fields make a constant angle with a non-zero fixed axis. We present the necessary and sufficient conditions for timelike curves via the q-frame to be q-helices in Lorentz-Minkowski 3-space. Then we find some results of the relations between q-helices and Darboux q-helices. Furthermore, we portray Darboux q-helices as special curves whose Darboux vector makes a constant angle with a non-zero fixed axis by choosing the curve as one of the types of q-helices, and also the general case.

Effects of Mn Content on Microstructure, Mechanical and Dry Sliding Wear Properties of Eutectic Al–Si–Cu Alloy

Yasin Alemdag,Murat Beder 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.12

In the present study, effects of Mn content on microstructure, hardness, tensile and dry sliding wear properties of eutecticAl–Si–Cu alloy in as cast-state were investigated. Mn addition to the eutectic alloy results in the formation of α-Al15Mn3Si2phase in its microstructure. It was found that hardness of eutectic alloy increases continuously with increasing Mn contentwhile its tensile strength and percentage elongation values decrease. It was also found that the friction coefficient and volumeloss of eutectic alloy decrease as Mn content increases. Amongst the alloys, the lowest friction coefficient is obtained withAl–12Si–3Cu–2Mn alloy yet the Al–12Si–3Cu–1Mn alloy exhibits the highest wear resistance. Formation of adhesion layer,its oxidation and delamination were observed to be main wear mechanisms of Al–12Si–3Cu–(0–2)Mn alloys. These findingsare explained in terms of formation of α-Al15Mn3Si2 phase, and its cracking tendency effect.