Collapse of steel cantilever roof of tribune induced by snow loads

Ahmet C. Altunışık,Şevket Ateş,Metin Hüsem,Ali F. Genç 국제구조공학회 2017 Steel and Composite Structures, An International J Vol.23 No.3

In this paper, it is aimed to present a detail investigation related to structural behavior of laterally unrestrained steel cantilever roof of tribune with slender cross section. The structure is located in Tutak town in A&$287;rı and collapsed on October 25, 2015 at eastern part of Turkey is considered as a case study. This mild sloped roof structure was built from a variable I beam, and supported on steel columns of 5.5 m height covering totally 240 m² closed area in plan. The roof of tribune collapsed completely without any indication during first snowfall after construction at midnight a winter day, fortunately before the opening hours. The meteorological records and observations of local persons are combined together to estimate the intensity of snow load in the region and it is compared with the code specified values. Also, the wide/thickness and height/thickness ratios for flange and web are evaluated according to the design codes. Three dimensional finite element model of the existing steel tribune roof is generated considering project drawings and site investigations using commercially available software ANSYS. The displacements, principal stresses and strains along to the cantilever length and column height are given as contour diagrams and graph format. In addition to site investigation, the numerical and analytical works conducted in this study indicate that the unequivocal reasons of the collapse are overloading action of snow load intensity, some mistakes made in the design of steel cantilever beams, insufficient strength and rigidity of the main structural elements, and construction workmanship errors.

Stamping-Based Planarization of Flexible Substrate for Low-Pressure UV Nanoimprint Lithography

Altun, Ali Ozhan,Jeong, Jun-Ho,Jung, Sung-Un,Kim, Ki-Don,Choi, Dae-Geun,Choi, Jun-Hyuk,Shim, Jong-Youp,Lee, Dong-II,Lee, Eung-Sug American Scientific Publishers 2008 Journal of Nanoscience and Nanotechnology Vol.8 No.11

<P>Patterning flexible substrates in nano scale is an important and challenging issue in the fabrication of next-generation devices based on a non-silicon substrate. Step and Flash imprint lithography (S-FIL<SUP>®</SUP>) which is a room temperature and low pressure process offers several important advantages, such as the use of a smaller and therefore cheaper stamp or the possibility of the overlay imprinting, as a transparent stamp is utilized. However, it is very difficult to perform S-FIL on a flexible substrate successfully due to the high waviness. The waviness of a flexible substrate is not a constant value in contrast to a rigid substrate. It depends on the imprint pressure applied onto the substrate. In this paper, in section two, the effect of the imprint pressure on the waviness of the surface of the flexible substrate is examined. It is proved that the waviness of the surface of the flexible substrate could not be reduced sufficiently to assure a successful imprint at low imprint pressures. In the third section, a method of patterning polymer substrates using ultra-violet nanoimprint lithography (UV-NIL) is presented. The method consists of two stages, stamping-based planarization and S-FIL. In stamping-based planarization, a planarization layer of transparent polymer is formed onto the flexible substrate. Waviness of the blank stamp (in this study, glass wafer) is transferred to the planarization layer. S-FIL is performed with the nanoimprint tool IMPRIO100 directly onto the planarization layer employing a 1 × 1 in.<SUP>2</SUP> quartz stamp. Optical microscope and SEM images of the successfully imprinted patterns were also presented.</P>

Boron nitride stamp for ultra-violet nanoimprinting lithography fabricated by focused ion beam lithography

Altun, Ali Ozhan,Jeong, Jun-Ho,Rha, Jong-Joo,Kim, Ki-Don,Lee, Eung-Sug IOP Pub 2007 Nanotechnology Vol.18 No.46

<P>Cubic boron nitride (c-BN) is one of the hardest known materials (second after diamond). It has a high level of chemical resistance and high UV transmittance. In this study, a stamp for ultra-violet nanoimprint lithography (UV-NIL) was fabricated using a bi-layered BN film deposited on a quartz substrate. Deposition of the BN was done using RF magnetron sputtering. A hexagonal boron nitride (h-BN) layer was deposited for 30 min before c-BN was deposited for 30 min. The thickness of the film was measured as 160 nm. The phase of the c-BN layer was investigated using Fourier transform infrared (FTIR) spectrometry, and it was found that the c-BN layer has a 40% cubic phase. The deposited film was patterned using focused ion beam (FIB) lithography for use as a UV-NIL stamp. Line patterns were fabricated with the line width and line distance set at 150 and 150 nm, respectively. The patterning process was performed by applying different currents to observe the effect of the current value on the pattern profile. The fabricated patterns were investigated using AFM, and it was found that the pattern fabricated by applying a current value of 50 picoamperes (pA) has a better profile with a 65 nm line depth. The UV transmittance of the 160 nm thick film was measured to be 70–86%. The hardness and modulus of the BN was measured to be 12 and 150 GPa, respectively. The water contact angle of the stamp surface was measured at 75°. The stamp was applied to UV-NIL without coating with an anti-adhesion layer. Successful imprinting was proved via scanning electron microscope (SEM) images of the imprinted resin.</P>

Three Dimensional Stamp for Multilayer Nanoimprint Lithography

Ali Ozhan Altun(알리알툰),Ki-don Kim(김기돈),Dae-guen Choi(최대근),Jun-Hyuk Choi(최준혁),Jun-ho Jeong(정준호),Jihye Lee(이지혜) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.5

UV 나노임프린트 리소그래피를 위한 불화 함유 다이아몬드 상 탄소 스탬프의 제작

알툰 알리(Altun Ali Ozhan),정준호(Jun-ho Jeong),나종주(Jong-joo Rha),최대근(Dae-geun Choi),김기돈(Ki-don Kim),이응숙(Eung-sug Lee) 한국정밀공학회 2006 한국정밀공학회 학술발표대회 논문집 Vol.2006 No.5월

A fluorine-doped diamond-like carbon (F-DLC) stamp which has high contact angle, high UV-transmittance and sufficient hardness, was fabricated using the following direct etching method: F-DLC is deposited on a quartz substrate using DC and RF magnetron sputtering, PMMA is spin coated and patterned using e-beam lithography and finally, O2 plasma etching is performed to transfer the line patterns having 100 ㎚ line width, 100 ㎚ line space and 70 ㎚ line depth on F-DLC. The optimum fluorine concentration was determined after performing several pre-experiments. The stamp was applied successfully to UV-NIL without being coated with an anti-adhesion layer.

Explanation of difenoconazole removal by chitosan with Langmuir adsorption isotherm and kinetic modeling

Altun Şükran,Kadak Ali Eslem,Küçükgülmez Aygül,Gülnaz Osman,Çelik Mehmet 한국독성학회 2023 Toxicological Research Vol.39 No.1

In this study, the adsorption of toxic difenoconazole pesticide was investigated by using chitosan. In the first phase of the study, chitosan was extracted from deep-water pink shrimp (Parapenaeus longirostris) shells, by deacetylation of the chitin, which is separated and disposed of after meat extraction in processing facilities in Turkey. The deacetylation degree, molecular weight, viscosity, moisture, and crude-ash values of the extracted chitosan were determined. Chitosan, having a high deacetylation degree (90.21%), was used as the adsorbent. In the second phase of the study, the effects of pH, temperature, and pesticide concentration on the adsorption were investigated. The optimum pH level for pesticide adsorption was determined as 5. It was observed that the adsorption increases as the temperature increases. A rapid increase was observed within the first 5 min of the 60-minute adsorption process in difenoconazole concentrations of 5, 15, and 25 μg/L, and after 10 min, the adsorption rate was stable. The Langmuir isotherm parameters regarding the adsorption were determined as aL = 0.635, kL = 15.10, and the Qmax value was calculated as 23.77 mg/g. In the evaluation of overall study results, it was determined that the chitosan biopolymer is a suitable adsorbent for difenoconazole pesticide adsorption.

Some Properties of S-metric Spaces and Fixed Point Results

Sedghi, Shaban,Altun, Ishak,Shobe, Nabi,Salahshour, Mohammad Ali Department of Mathematics 2014 Kyungpook mathematical journal Vol.54 No.1

In this paper, we introduce S-metric spaces and give their some properties. Also we present a common fixed point theorem for multivalued maps on complete S-metric spaces. The single valued case and an illustrative example are given.

Effect of etoricoxib on experimental oxidative testicular ischemia–reperfusion damage in rats induced with torsion– detorsion

Turgut Yapanoglu,Fatih Ozkaya,Ali Haydar Yilmaz,Renad Mammadov,Ferda Keskin Cimen,Erkan Hirik,Durdu Altuner 대한약리학회 2017 The Korean Journal of Physiology & Pharmacology Vol.21 No.5

Etoricoxib features antioxidant and anti-inflammatory properties concomitantly, suggesting that it may be beneficial in testicular ischemia reperfusion (I/R) damage. Our aim is to investigate the effects of etoricoxib on testicular I/R damage induced with torsion-detorsion (TD). The etoricoxib + torsion-detorsion (ETD) groups of animals were given etoricoxib in 50 and 100 mg/kg of body weight (ETD- 50 and ETD-100), while the testes torsion-detorsion (TTD) and sham operation rat group (SOG) animals were given single oral doses of distilled water as a solvent. TTD, ETD-50 and ETD-100 groups were subjected to 720o degrees torsion for four hours, and detorsion for four hours. The SOG group was not subjected to this procedure. Biochemical, gene expression and histopathological analyses were carried out on the testicular tissues. The levels of malondialdehyde (MDA), myeloperoxidase (MPO), interleukin-1 beta (IL-1β) and tumor necrosis factor alpha (TNF-α) were significantly higher, and the levels of total glutathione (tGSH) and glutathione reductase (GSHRd) were significantly lower in the TTD group, compared to the ETD-50, ETD-100 and SOG groups. Etoricoxib at a dose of 100 mg/kg better prevented I/R damage than the 50 mg/kg dose. Etoricoxib may be useful in clinical practice in the reduction of I/ R damage on testes caused by torsion-detorsion.

Assessment of the effect of sulfate attack on cement stabilized montmorillonite

Kalipcilar, Irem,Mardani-Aghabaglou, Ali,Sezer, Gozde Inan,Altun, Selim,Sezer, Alper Techno-Press 2016 Geomechanics & engineering Vol.10 No.6

In this study, aiming to investigate the effects of sulfate attack on cement stabilized highly plastic clay; an experimental study was carried out considering the effects of cement type, sulfate type and its concentration, cement content and curing period. Unconfined compressive strength and chloride-ion penetration tests were performed to obtain strength and permeability characteristics of specimens cured under different conditions. Test results were evaluated along with microstructural investigations including SEM and EDS analyses. Results revealed that use of sulfate resistance cement instead of normal portland cement is more plausible for soils under the threat of sulfate attack. Besides, it was verified that sulfate concentration is responsible for strength loss and permeability increase in cement stabilized montmorillonite. Finally, empirical equations were proposed to estimate the unconfined compressive strength of cement stabilized montmorillonite, which was exposed to sulfate attack for 28 days.

Pattern-definable and low cost fabrication of nanopatterned conducting polymer film on flexible substrates.

Lee, Jihye,Choi, Dae-Geun,Altun, Ali Ozhan,Kim, Ki-Don,Choi, Jun-Hyuk,Lee, Eung-Sug,Jeong, Jun-Ho American Scientific Publishers 2010 Journal of Nanoscience and Nanotechnology Vol.10 No.9

<P>This study reports the pattern definable and low cost fabrication of nanopatterned conducting polymer film on flexible substrates. Noble nanopatterned polymer hard template was fabricated by using nanoimprint lithography (NIL) and used for electropolymerization of conducting polymer. Conducting polymer was electrochemically deposited on the template and transferred over to flexible substrates. Eventually conducting polymer films with various nanopatterns were fabricated on flexible substrates. High pattern definability was achieved by nanoimprinted polymer template, which was molded from lithographically fabricated stamp. Low cost fabrication was accomplished due to low cost NIL, reusable polymer templates, and low material consumption of electrodeposition. The electrodeposited films were transferred using double sided tape. Because the templates are made of flexible polymer, the transfer bonding method applied in this study is adaptable to both wafers and flexible polymer substrates. The fabricated nanopatterned conducting polymer film can be applied to gas sensors, super capacitors, super wetting films, and neuron interfaces due to its characteristic of high surface to volume. For an illustrative application, the gas sensing properties of films were tested. The result showed enhanced sensing characteristic with nanopatterned film, which are attributed to the high surface to volume ratio of nanopatterned films.</P>