Toward Wafer Scale Fabrication of Graphene Based Spin Valve Devices

Avsar, Ahmet,Yang, Tsung-Yeh,Bae, Sukang,Balakrishnan, Jayakumar,Volmer, Frank,Jaiswal, Manu,Yi, Zheng,Ali, Syed Rizwan,Gü,ntherodt, Gernot,Hong, Byung Hee,Beschoten, Bernd,Ö,zyilmaz, Barb American Chemical Society 2011 Nano letters Vol.11 No.6

<P>We demonstrate injection, transport, and detection of spins in spin valve arrays patterned in both copper based chemical vapor deposition (Cu-CVD) synthesized wafer scale single layer and bilayer graphene. We observe spin relaxation times comparable to those reported for exfoliated graphene samples demonstrating that chemical vapor deposition specific structural differences such as nanoripples do not limit spin transport in the present samples. Our observations make Cu-CVD graphene a promising material of choice for large scale spintronic applications.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2011/nalefd.2011.11.issue-6/nl200714q/production/images/medium/nl-2011-00714q_0001.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl200714q'>ACS Electronic Supporting Info</A></P>

Seismic vulnerability assessment criteria for RC ordinary highway bridges in Turkey

Avsar, O.,Yakut, A. Techno-Press 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.43 No.1

One of the most important and challenging steps in seismic vulnerability and performance assessment of highway bridges is the determination of the bridge component damage parameters and their corresponding limit states. These parameters are very essential for defining bridge damage state as well as determining the performance of highway bridges under a seismic event. Therefore, realistic damage limit states are required in the development of reliable fragility curves, which are employed in the seismic risk assessment packages for mitigation purposes. In this article, qualitative damage assessment criteria for ordinary highway bridges are taken into account considering the critical bridge components in terms of proper engineering demand parameters (EDPs). Seismic damage of bridges is strongly related to the deformation of bridge components as well as member internal forces imposed due to seismic actions. A simple approach is proposed for determining the acceptance criteria and damage limit states for use in seismic performance and vulnerability assessment of ordinary highway bridges in Turkey constructed after the 1990s. Physical damage of bridge components is represented by three damage limit states: serviceability, damage control, and collapse prevention. Inelastic deformation and shear force demand of the bent components (column and cap beam), and superstructure displacement are the most common causes for the seismic damage of the highway bridges. Each damage limit state is quantified with respect to the EDPs: i.e. curvature and shear force demand of RC bent components and superstructure relative displacement.

Seismic vulnerability assessment criteria for RC ordinary highway bridges in Turkey

Ö. Avsar,A. Yakut 국제구조공학회 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.43 No.1

One of the most important and challenging steps in seismic vulnerability and performance assessment of highway bridges is the determination of the bridge component damage parameters and their corresponding limit states. These parameters are very essential for defining bridge damage state as well as determining the performance of highway bridges under a seismic event. Therefore, realistic damage limit states are required in the development of reliable fragility curves, which are employed in the seismic risk assessment packages for mitigation purposes. In this article, qualitative damage assessment criteria for ordinary highway bridges are taken into account considering the critical bridge components in terms of proper engineering demand parameters (EDPs). Seismic damage of bridges is strongly related to the deformation of bridge components as well as member internal forces imposed due to seismic actions. A simple approach is proposed for determining the acceptance criteria and damage limit states for use in seismic performance and vulnerability assessment of ordinary highway bridges in Turkey constructed after the 1990s. Physical damage of bridge components is represented by three damage limit states: serviceability,damage control, and collapse prevention. Inelastic deformation and shear force demand of the bent components (column and cap beam), and superstructure displacement are the most common causes for the seismic damage of the highway bridges. Each damage limit state is quantified with respect to the EDPs: i.e. curvature and shear force demand of RC bent components and superstructure relative displacement.

Bimorph piezoelectric energy harvester structurally integrated on a trapezoidal plate

Ahmet Levent Avsar,Melin Sahin 국제구조공학회 2016 Smart Structures and Systems, An International Jou Vol.18 No.2

A bimorph piezoelectric energy harvester is developed for harvesting energy under the vortex induced vibration and it is integrated to a host structure of a trapezoidal plate without changing its passive dynamic properties. It is aimed to select trapezoidal plate as similar to a vertical fin-like structure which could be a part of an air vehicle. The designed energy harvester consists of an aluminum beam and two identical multi fiber composite (MFC) piezoelectric patches. In order to understand the dynamic characteristic of the trapezoidal plate, finite element analysis is performed and it is validated through an experimental study. The bimorph piezoelectric energy harvester is then integrated to the trapezoidal plate at the most convenient location with minimal structural displacement. The finite element model is constructed for the new combined structure in ANSYS Workbench 14.0 and the analyses performed on this particular model are then validated via experimental techniques. Finally, the energy harvesting performance of the bimorph piezoelectric energy harvester attached to the trapezoidal plate is also investigated through wind tunnel tests under the air load and the obtained results indicate that the system is a viable one for harvesting reasonable amount of energy.

Structural repairing of damaged reinforced concrete beam-column assemblies with CFRPs

Yurdakul, Ozgur,Avsar, Ozgur Techno-Press 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.54 No.3

Depending on the damage type as well as the level of damage observed after the earthquake, certain measures should be taken for the damaged buildings. In this study, structural repairing of two different types of damaged RC beam-column assembly by carbon fiber-reinforced polymer sheets is investigated in detail as a member repairing technique. Two types of 1:1 scale test specimens, which represent the exterior RC beam-column connection taken from inflection points of the frame, are utilized. The first specimen is designed according to the current Turkish Earthquake Code, whereas the second one represents a deficient RC beam-column assembly. Both of the specimens were subjected to cyclic quasistatic loading in the laboratory and different levels of structural damage were observed. The first specimen displayed a ductile response with the damage concentrated in the beam. However, in the second specimen, the beam-column joint was severely damaged while the rest of the members did not attain their capacities. Depending on the damage type of the specimens, the damaged members were repaired by CFRP wrapping with different configurations. After testing the repaired specimens, it is found that former capacities of the damaged members were mostly recovered by the application of CFRPs on the damaged members.

Influence of natural organic matter (NOM) coatings on nanoparticle adsorption onto supported lipid bilayers

Bo, Zhang,Avsar, Saziye Yorulmaz,Corliss, Michael K.,Chung, Minsub,Cho, Nam-Joon Elsevier 2017 Journal of hazardous materials Vol.339 No.-

<P><B>Abstract</B></P> <P>As the worldwide usage of nanoparticles in commercial products continues to increase, there is growing concern about the environmental risks that nanoparticles pose to biological systems, including potential damage to cellular membranes. A detailed understanding of how different types of nanoparticles behave in environmentally relevant conditions is imperative for predicting and mitigating potential membrane-associated toxicities. Herein, we investigated the adsorption of two popular nanoparticles (silver and buckminsterfullerene) onto biomimetic supported lipid bilayers of varying membrane charge (positive and negative). The quartz crystal microbalance-dissipation (QCM-D) measurement technique was employed to track the adsorption kinetics. Particular attention was focused on understanding how natural organic matter (NOM) coatings affect nanoparticle-bilayer interactions. Both types of nanoparticles preferentially adsorbed onto the positively charged bilayers, although NOM coatings on the nanoparticle and lipid bilayer surfaces could either inhibit or promote adsorption in certain electrolyte conditions. While past findings showed that NOM coatings inhibit membrane adhesion, our findings demonstrate that the effects of NOM coatings are more nuanced depending on the type of nanoparticle and electrolyte condition. Taken together, the results demonstrate that NOM coatings can modulate the lipid membrane interactions of various nanoparticles, suggesting a possible way to improve the environmental safety of nanoparticles.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Interaction of Ag and C<SUB>60</SUB> nanoparticles with charged lipid membranes was studied. </LI> <LI> Quartz crystal microbalance experiments measured the adsorption kinetics. </LI> <LI> Natural organic matter (NOM) either inhibited or promoted nanoparticle adsorption. </LI> <LI> Adsorption profile depended on nanoparticle type, electrolyte condition, and NOM. </LI> </UL> </P>

Evaluating the effects of an online marketing program: The case of Mexico’s national tourism promotion board

Oliver Cruz-Milán,Veysel Avsar 한국마케팅과학회 2021 마케팅과학연구 Vol.31 No.4

Given some of the limitations of survey-based methodologies to assess tourism advertising and promotional programs, the objective of this research is to evaluate the effectiveness of Mexico’s tourism promotion board campaigns executed through digital media channels between 2012 and 2017 using a quasi-experimental, longitudinal design. A difference-in-difference model is estimated to compare the tourism inflow from countries before and after receiving the online promotion (treatment) with a control group of countries that did not receive it, controlling for demographic and economic variables that influence tourism inflow. The study results and return on investment estimations demonstrate that the digital advertising campaign has a significant effect on annual international visitor arrivals, underscoring the importance of employing cost-effectiveness metrics to determine the impact of marketing investments.

Cardiac Autonomic Function Evaluated by the Heart Rate TurbulenceMethod was not Changed in Obese Patients without Co-morbidities

Gursel Acarturk,Celal Kilit,Ersel Onrat,Alaettin Avsar,Mehmet Melek,Atac Celik 대한의학회 2007 Journal of Korean medical science Vol.22 No.4

Effectiveness of seismic repairing stages with CFRPs on the seismic performance of damaged RC frames

Duran, Burak,Tunaboyu, Onur,Kaplan, Onur,Avsar, Ozgur Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.67 No.3

This study aims at evaluating the performance of repairing technique with CFRPs in recovering cyclic performance of damaged columns in flexure in terms of structural response parameters such as strength, dissipated energy, stiffness degradation. A 2/3 scaled substandard reinforced concrete frame was constructed to represent the substandard RC buildings especially in developing countries. These substandard buildings have several structural deficiencies such as strong beam-weak column phenomenon, improper reinforcement detailing and poor material properties. Flexural plastic hinges occurred at the columns ends after testing the substandard specimen under both constant axial load and reversed cyclic lateral loading. Afterwards, the damaged columns were externally wrapped with CFRP sheets both in transverse and longitudinal directions and then retested under the same loading protocol. In addition, ambient vibration measurements were taken from the undamaged, damaged and the repaired specimens at each structural repair steps to identify the effectiveness of each repairing step by monitoring the change in the natural frequencies of the tested specimen. The ambient vibration test results showed that the applied repairing technique with external CFRP wrapping was proved to recover stiffness of the pre-damaged specimen. Moreover, the lateral load capacity of the pre-damaged substandard RC frame was restored with externally bonded CFRP sheets.

Atrial Septal Defect Closure: Comparison of Vertical Axillary Minithoracotomy and Median Sternotomy

Huseyin Hakan Poyrazoglu,Mustafa Kemal Avsar,Şerafettin Demir,Zeynep Karakaya,Tayfun Güler,Funda Tor 대한흉부외과학회 2013 Journal of Chest Surgery (J Chest Surg) Vol.46 No.5

Background: This study aims to evaluate whether or not the method of right vertical axillary minithoracotomy (RVAM) is preferable to and as reliable as conventional sternotomy surgery, and also assesses its cosmetic results. Methods: Thirty-three patients (7 males, 26 females) with atrial septal defect were admitted to the Cardiovascular Surgery Clinic of Cukurova University from December 2005 until January 2010. The patients’ ages ranged from 3 to 22. Patients who underwent vertical axillary minithracotomy were assigned to group I, and those undergoing conventional sternotomy, to group II. Group I and group II were compared with regard to the preoperative, perioperative and postoperative variables. Group I included 12 females and 4 males with an average age of 16.5±9.7. Group II comprised 14 female and 3 male patients with an average age of 18.5±9.8 showing similar features and pathologies. The cases were in Class I–II according to the New York Heart Association (NYHA) Classification, and patients with other cardiac and systemic problems were not included in the study. The ratio of the systemic blood flow to the pulmonary blood flow (Qp/Qs) was 1.8±0.2. The average pulmonary artery pressure was 35±10 mmHg. Following the diagnosis, performing elective surgery was planned. Results: No significant difference was detected in the average time of the patients’ extraportal circulation, cross-clamp and surgery (p>0.05). In the early postoperative period of the cases, the duration of mechanical ventilator support, the drainage volume in the first 24 hours, and the hospitalization time in the intensive care unit were similar (p>0.05). Postoperative pains were evaluated together with narcotic analgesics taken intravenously or orally. While 7 cases (43.7%) in group I needed postoperative analgesics, 12 cases (70.6%) in group II needed them. No mortality or major morbidity has occurred in the patients. The incision style and sizes in all of the patients undergoing RVAM were preserved as they were at the beginning. Furthermore, the patients of group I were mobilized more quickly than the patients of group II. The patients of group I were quite pleased with the psychological and cosmetic results. No residual defects have been found in the early postoperative period and after the end of the follow-up periods. All of the patients achieved functional capacity per NYHA. No deformation of breast growth has been detected during 18 months of follow-up for the group I patients, who underwent RVAM. Conclusion: To conclude, the repair of atrial septal defect by RVAM, apart from the limited working zone for the surgeon in these pathologies as compared to sternotomymay be considered in terms of the outcomes, and early and late complications. And this has accounted for less need of analgesics and better cosmetic results in recent years.