Comparison of the frictional characteristics of aesthetic orthodontic brackets measured using a modified in vitro technique

Nursel Arici,Berat Serdar Akdeniz,Selim Arici 대한치과교정학회 2015 대한치과교정학회지 Vol.45 No.1

Objective: The coefficients of friction (COFs) of aesthetic ceramic and stainless steel brackets used in conjunction with stainless steel archwires were investigated using a modified linear tribometer and special computer software, and the effects of the bracket slot size (0.018 inches [in] or 0.022 in) and materials (ceramic or metal) on the COF were determined. Methods: Four types of ceramic (one with a stainless steel slot) and one conventional stainless steel bracket were tested with two types of archwire sizes: a 0.017 × 0.025-in wire in the 0.018-in slots and a 0.019 × 0.025-in wire in the 0.022-in slot brackets. For pairwise comparisons between the 0.018-in and 0.022-in slot sizes in the same bracket, an independent sample t-test was used. One-way and two-way analysis of variance (ANOVA) and Tukey’s post-hoc test at the 95% confidence level (α = 0.05) were also used for statistical analyses. Results: There were significant differences between the 0.022-in and 0.018-in slot sizes for the same brand of bracket. ANOVA also showed that both slot size and bracket slot material had significant effects on COF values (p < 0.001). The ceramic bracket with a 0.022-in stainless steel slot showed the lowest mean COF (m = 0.18), followed by the conventional stainless steel bracket with a 0.022-in slot (m = 0.21). The monocrystalline alumina ceramic bracket with a 0.018-in slot had the highest COF (m = 0.85). Conclusions: Brackets with stainless steel slots exhibit lower COFs than ceramic slot brackets. All brackets show lower COFs as the slot size increases.

Generalized curved beam on elastic foundation solved by transfer matrix method

Arici, Marcello,Granata, Michele Fabio Techno-Press 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.40 No.2

A solution of space curved bars with generalized Winkler soil found by means of Transfer Matrix Method is presented. Distributed, concentrated loads and imposed strains are applied to the beam as well as rigid or elastic boundaries are considered at the ends. The proposed approach gives the analytical and numerical exact solution for circular beams and rings, loaded in the plane or perpendicular to it. A well-approximated solution can be found for general space curved bars with complex geometry. Elastic foundation is characterized by six parameters of stiffness in different directions: three for rectilinear springs and three for rotational springs. The beam has axial, shear, bending and torsional stiffness. Numerical examples are given in order to solve practical cases of straight and curved foundations. The presented method can be applied to a wide range of problems, including the study of tanks, shells and complex foundation systems. The particular case of box girder distortion can also be studied through the beam on elastic foundation (BEF) analogy.

Biodiversity and technological properties of yeasts from Turkish sourdough

Arici, Muhammet,Ozulku, Gorkem,Yildirim, Rusen Metin,Sagdic, Osman,Durak, M. Zeki 한국식품과학회 2018 Food Science and Biotechnology Vol.27 No.2

In this study, yeasts were isolated and characterized from twelve traditional sourdough samples which belongs to Black Sea and Aegean regions of Turkey. Twenty six yeast species were isolated and identified by both 26S rDNA sequencing and FTIR spectroscopy. Saccharomyces cerevisiae (50%), Torulaspora delbrueckii (40%) and Kluyveromyces marxianus (10%) were found in 12 Turkish traditional sourdough samples. S. cerevisiae was found to be the most dominant species in Aegean region while T. delbrueckii was the most frequently isolated species in Black Sea region. Some technological properties of isolated yeast species such as acidity development, resistance to NaCI and potassium sorbate, and yeast effect on bread quality were investigated. Breads were prepared by S. cerevisiae TGM38 strain demonstrated the highest bread volume compared the other yeasts used in the study. This study showed the yeast diversity and technological properties of traditional Turkish sourdough breads fermented by chosen yeast species.

Conceptual design of prestressed slab bridges through one-way flexural load balancing

Arici, Marcello,Granata, Michele Fabio Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.48 No.5

In this paper a study on prestressed concrete slab bridges is presented. A design philosophy based on the concept of load balancing through prestressing is proposed in order to minimize the effects of delayed deformations due to creep. Aspects related to the stress redistribution inside these bridges for time-dependent phenomena are analyzed and discussed, by applying the principles of aging linear visco-elasticity. Prestressing is seen as an equivalent external load which counterbalances the permanent loads applied to the bridge, nullifying the elastic deflections due to sustained loads, and thus avoiding the related delayed deformations. An optimization of the structural behavior through the use of one-way prestressing is achieved. The determination of a convenient variable depth of slab bridges and the correspondent layout of tendons is considered as a useful means for applying the load balancing concept in actual cases of structures like long cantilevers or bridge decks. A case-study related to the slab bridges built 30 years ago at Jeddah in Saudi Arabia is presented and discussed, in order to show the effectiveness of the proposed approach to the conceptual design of prestressed concrete bridges.

Conceptual design of prestressed slab bridges through one-way flexural load balancing

Marcello Arici,Michele Fabio Granata 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.48 No.5

In this paper a study on prestressed concrete slab bridges is presented. A design philosophy based on the concept of load balancing through prestressing is proposed in order to minimize the effects of delayed deformations due to creep. Aspects related to the stress redistribution inside these bridges for timedependent phenomena are analyzed and discussed, by applying the principles of aging linear visco-elasticity. Prestressing is seen as an equivalent external load which counterbalances the permanent loads applied to the bridge, nullifying the elastic deflections due to sustained loads, and thus avoiding the related delayed deformations. An optimization of the structural behavior through the use of one-way prestressing is achieved. The determination of a convenient variable depth of slab bridges and the correspondent layout of tendons is considered as a useful means for applying the load balancing concept in actual cases of structures like long cantilevers or bridge decks. A case-study related to the slab bridges built 30 years ago at Jeddah in Saudi Arabia is presented and discussed, in order to show the effectiveness of the proposed approach to the conceptual design of prestressed concrete bridges.

Influence of Secondary Torsion on Curved Steel Girder Bridges with Box and I-Girder Cross-sections

Marcello Arici,Michele Fabio Granata,Maria Oliva 대한토목학회 2015 KSCE JOURNAL OF CIVIL ENGINEERING Vol.19 No.7

Steel curved girder bridges are largely used today in motorways and railways. They are often composed of thin-walled crosssections, entirely made of steel or with an upper concrete slab. The deck may have I-girders or box cross-sections: in any case curved girders are subjected to twisting moment, associated with bending, even for dead loads. Moreover, in thin-walled sections the influence of non-uniform torsion becomes sizable with respect to Saint Venant torsion, modifying the state of tangential stresses in the section and introducing axial stresses due to warping being prevented. Open sections of I-girder bridges are especially subject to these phenomena and warping can be significant not only for curved bridges but also for eccentrically applied traffic loads in straight ones. In this paper a method for the evaluation of the effects of non-uniform torsion, based on an energetic approach, is proposed; the method is simple and fast, with a reduced computational burden with respect to finite elements. The solution of curved girder bridges is performed by the Hamiltonian Structural Analysis method, which is implemented for straight and curved girders with thin-walled cross-sections. A parametric analysis is proposed for single and multi-span bridges, with variation in type of loads applied, crosssection parameters, geometric curvature of bridge deck and stiffness ratios of the cross-section. The parametric study is presented through dimensionless diagrams of internal forces for the evaluation of the global behaviour of curved girder bridges together with indications on the stress state of the cross-section. The interpretation of the results of the analyses performed can be useful to designers for the conceptual design stages and for optimization of the geometric and mechanical parameters of I-girder and box girder cross-sections.

Comparison of Stab Incision and Eyelid Crease Incision Techniques in Children with Revision Frontalis Sling Surgeries Using Silicone Rods

Ceyhun Arici,İbrahim Bulent Buttanri 대한안과학회 2024 Korean Journal of Ophthalmology Vol.38 No.1

Purpose: To compare stab and eyelid crease incision techniques in revision frontalis sling surgeries using silicone rods. Methods: This retrospective study involved 52 eyes in 48 consecutive pediatric patients who underwent revision frontalis sling surgery between 2008 and 2019. All primary surgeries were performed by making eyelid crease incisions and suturing of silicone rods onto the tarsal plates. The revision surgeries were performed by either making stab incisions over the eyelid through which to pass the silicone rods (group A), or by refixing the same or a new silicone rod to the tarsal plate (group B). The surgical results were compared. Results: The mean follow-up period was 22.4 months (range, 6–62 months) and the mean age of the patients was 6.1 years (range, 1–16 years). There were 28 female and 20 male patients. Surgical success was achieved in 23 of 28 patients (82.1%) in group A, and 12 of 24 patients (50.0%) in group B. The difference between the groups was statistically significant (p = 0.012). Superficial punctate epithelial defects were detected in six group A patients (21.4%) and seven group B patients (29.1%). In group B, lid hematoma occurred in three patients (12.5%) and entropion occurred in three patients (12.5%). The silicone rods were removed from two eyes, and entropion spontaneously resolved in one eye with close follow-up. Conclusions: Using the stab incision technique increases revision frontalis sling surgery success rates when primary surgeries are performed using eyelid crease incisions and suturing silicone rods to the tarsal plates in children.

Biodiversity and technological properties of yeasts from Turkish sourdough

Muhammet Arici,Gorkem Ozulku,Rusen Metin Yildirim,Osman Sagdic,M. Zeki Durak 한국식품과학회 2018 Food Science and Biotechnology Vol.27 No.2

In this study, yeasts were isolated and characterized from twelve traditional sourdough samples which belongs to Black Sea and Aegean regions of Turkey. Twenty six yeast species were isolated and identified by both 26S rDNA sequencing and FTIR spectroscopy. Saccharomyces cerevisiae (50%), Torulaspora delbrueckii (40%) and Kluyveromyces marxianus (10%) were found in 12 Turkish traditional sourdough samples. S. cerevisiae was found to be the most dominant species in Aegean region while T. delbrueckii was the most frequently isolated species in Black Sea region. Some technological properties of isolated yeast species such as acidity development, resistance to NaCI and potassium sorbate, and yeast effect on bread quality were investigated. Breads were prepared by S. cerevisiae TGM38 strain demonstrated the highest bread volume compared the other yeasts used in the study. This study showed the yeast diversity and technological properties of traditional Turkish sourdough breads fermented by chosen yeast species.

Generalized curved beam on elastic foundation solved by transfer matrix method

Marcello Arici,Michele Fabio Granata 국제구조공학회 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.40 No.2

A solution of space curved bars with generalized Winkler soil found by means of Transfer Matrix Method is presented. Distributed, concentrated loads and imposed strains are applied to the beam as well as rigid or elastic boundaries are considered at the ends. The proposed approach gives the analytical and numerical exact solution for circular beams and rings, loaded in the plane or perpendicular to it. A well-approximated solution can be found for general space curved bars with complex geometry. Elastic foundation is characterized by six parameters of stiffness in different directions: three for rectilinear springs and three for rotational springs. The beam has axial, shear, bending and torsional stiffness. Numerical examples are given in order to solve practical cases of straight and curved foundations. The presented method can be applied to a wide range of problems, including the study of tanks, shells and complex foundation systems. The particular case of box girder distortion can also be studied through the beam on elastic foundation (BEF) analogy.

Size effect in concrete blocks under local pressure

Ince, R.,Arici, E. Techno-Press 2005 Structural Engineering and Mechanics, An Int'l Jou Vol.19 No.5

Numerous tests on concrete structure members under local pressure demonstrated that the compressive strength of concrete at the loaded surface is increased by the confinement effect provided by the enveloping concrete. Even though most design codes propose specific criteria for preventing bearing failure, they do not take into consideration size effect which is an important phenomenon in the fracture mechanics of concrete/reinforced concrete. In this paper, six series of square prism concrete blocks with three different depths (size range = 1:4) and two different height/depth ratios of 2 and 3 are tested under concentrated load. Ultimate loads obtained from the test results are analysed by means of the modified size effect law (MSEL). Then, a prediction formula, which considers effect of both depth and height on size effect, is proposed. The developed formula is compared with experimental data existing in the literature. It is concluded that the observed size effect is in good agreement with the MSEL.