Fracture resistance of upper central incisors restored with different posts and cores

Saeid Tavanafar,,Kamran Amirian Chaijan,Saeid Tavanafar 대한치과보존학회 2015 Restorative Dentistry & Endodontics Vol.40 No.3

Objectives: To determine and compare the fracture resistance of endodontically treated maxillary central incisors restored with different posts and cores. Materials and Methods: Forty-eight upper central incisors were randomly divided into four groups: cast post and core (group 1), fiber-reinforced composite (FRC) post and composite core (group 2), composite post and core (group 3), and controls (group 4). Mesio-distal and bucco-lingual dimensions at 7 and 14 mm from the apex were compared to ensure standardization among the groups. Twelve teeth were prepared for crown restoration (group 4). Teeth in other groups were endodontically treated, decoronated at 14 mm from the apex, and prepared for posts and cores. Resin-based materials were used for cementation in groups 1 and 2. In group 3, composite was used directly to fill the post space and for core build-up. All samples were restored by standard metal crowns using glass ionomer cement, mounted at 135° vertical angle, subjected to thermomechanical aging, and then fractured using a universal testing machine. Kruskal-Wallis and Mann-Whitney U tests were used to analyze the data. Results: Fracture resistance of the groups was as follows: Control (group 4) > cast post and core (group 1) > fiber post and composite core (group 2) > composite post and core (group 3). All samples in groups 2 and 3 fractured in restorable patterns, whereas most (58%) in group 1 were non-restorable. Conclusions: Within the limitations of this study, FRC posts showed acceptable fracture resistance with favorable fracture patterns for reconstruction of upper central incisors.

Evaluation of Maturity Method for Steel Fiber Reinforced Concrete

Saeid Kamkar,Özgür Eren 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.1

The evaluation of steel-fiber reinforced concrete using the maturity method was investigated in this study. There were four different volume fractions of fibers (0, 0.5, 1 and 1.5 by volume of concrete) and three different curing temperatures (8°C, 22°C and 32°C) considered. The compressive strength and flexural strength were tested at 1, 3, 7, 10, 14 and 28 days for all of the volume fractions of fibers and at the different curing temperatures. The results show that as the volume fraction of fiber increased from 0 to 1.5%, the compressive and flexural strengths increased by 14% and 35%, respectively, compared to plain concrete. The maturity method was used to predict the compressive and flexural strengths. Four different equations (linear hyperbolic, parabolic hyperbolic, logarithmic and exponential) were used to predict the compressive and flexural strengths. All of the predicted models have good correlations with the experimental results for both compressive and flexural strengths. Moreover, to predict the compressive and flexural strengths using the maturity method, the apparent activation energies were calculated.

Laboratory considerations about frictional force on pipe surface when slurry machine is used

Saeid Khazaei,Hideki Shimada,Takashi Kawai,Jyunichi Yotsumoto,Iwao Sato,Kikuo Matsui 한국암반공학회 2003 한국암반공학회 학술대회 및 세미나 자료집 Vol.- No.-

Preparation of MWCNT/PDMS Conductive Micro-Patterned Nanocomposites

Saeid Aslnejad,Morteza Nasiri,Farhang Abbasi,Hamed Abdipour 한국고분자학회 2020 Macromolecular Research Vol.28 No.8

Conductive multi-walled carbon nanotube (MWCNT)/polydimethylsiloxane (PDMS) nanocomposites were prepared via solution method and their conductive micro-patterns were made using the doctor blade technique. The prepared patterns were characterized via scanning electron microscopy (SEM), cyclic voltammetry, and four-point probe conductivity meter. SEM images of the cross-sections of micro-patterns revealed that by increasing MWCNT concentration from 5 to 10%, while the dense and smooth bulk structure converted to a brittle one, their conductivities raised from 0.07 up to 0.33 S/cm. These micro-patterns preserved their conductivities under high bending cycles except for high MWCNT loading which loses almost half of its conductivity. The cyclic voltammetry analyses showed that MWCNT/ PDMS conductive micro-patterns had supercapacitor properties. The specific capacitance of the composite containing 10 wt% of MWCNT was 0.35 F/g. These nanocomposites can be used in cochlear implants due to their high conductivities. Their low working voltages ensure the safety of the neural tissues.

DISTINGUISHING NUMBER AND DISTINGUISHING INDEX OF STRONG PRODUCT OF TWO GRAPHS

( Saeid Alikhani ),( Samaneh Soltani ) 호남수학회 2020 호남수학학술지 Vol.42 No.4

The distinguishing number (index) D(G) (D’(G)) of a graph G is the least integer d such that G has an vertex label- ing (edge labeling) with d labels that is preserved only by a triv- ial automorphism. The strong product G □ H of two graphs G and H is the graph with vertex set V (G) × V (H) and edge set {{(x₁, x₂); (y₁, y₂)}|x_iy_i ∈ E(G_i) or x_i = y_i for each 1 ≤ i ≤ 2:}. In this paper we study the distinguishing number and the distin- guishing index of strong product of two graphs. We prove that for every k ≥ 2, the k-th strong power of a connected S-thin graph G has distinguishing index equal two.

T-NEIGHBORHOODS IN VARIOUS CLASSES OF ANALYTIC FUNCTIONS

Saeid Shams,Ali Ebadian,Mahta Sayadiazar,Janusz Sokol 대한수학회 2014 대한수학회보 Vol.51 No.3

Let A be the class of analytic functions f in the open unit disk U = {z : |z| < 1} with the normalization conditions f(0) = f′(0)−1 = 0. If f(z) = z + P∞ n=2 anzn and > 0 are given, then the T-neighborhood of the function f is defined as TN(f) = ( g(z) = z + ∞X n=2 bnzn 2 A : ∞X n=2 Tn|an − bn| ) , where T = {Tn}∞n=2 is a sequence of positive numbers. In the present paper we investigate some problems concerning T-neighborhoods of functions in various classes of analytic functions with T = { 2−n/n2} ∞ n=2. We also find bounds for ∗ T (A,B) defined by ∗ T (A,B) = inf { > 0 : B TN(f) for all f ∈ A} , where A, B are given subsets of A.

(WEAK) IMPLICATIVE HYPER K-IDEALS

Saeid, A.Borumand,Borzooei, R.A.,Zahedi, M.M. Korean Mathematical Society 2003 대한수학회보 Vol.40 No.1

In this note first we define the notions of weak implicative and implicative hyper K-ideals of a hyper K-algebra H. Then we state and prove some theorems which determine the relationship between these notions and (weak) hyper K-ideals. Also we give some relations between these notions and all types of positive implicative hyper K-ideals. Finally we classify the implicative hyper K-ideals of a hyper K-algebra of order 3.

Adsorption of 2,4-dichlorophenoxyacetic acid pesticide by graphitic carbon nanostructures prepared from biomasses

Saeid Azizian,Maryam Khoshnood 한국공업화학회 2012 Journal of Industrial and Engineering Chemistry Vol.18 No.5

Removal of a pesticide (2,4-dichlorophenoxyacetic acid) from aqueous solution by magnetic and graphitic carbon nanostructures was studied from both equilibrium and kinetic point of view. The magnetic and graphitic carbon nanostructures as adsorbents were prepared from two different biomasses, cotton and filter paper. The resultant adsorbents were characterized with TEM and N2adsorption–desorption methods. The kinetic and equilibrium data were modeled with different models. The adsorption capacities for the prepared adsorbents from filter paper and cotton are about 77 and 33 mg/g, respectively. The effect of initial pH of solution on the pesticide removal efficiency was studied too. 2012 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.

INTERVAL-VALUED FUZZY BG-ALGEBRAS

Saeid, Arsham Borumand The Kangwon-Kyungki Mathematical Society 2006 한국수학논문집 Vol.14 No.2

In this note the notion of interval-valued fuzzy BG-algebras (briefly, i-v fuzzy BG-algebras), the level and strong level BG-subalgebra is introduced. Then we state and prove some theorems which determine the relationship between these notions and BG-subalgebras. The images and inverse images of i-v fuzzy BG-subalgebras are defined, and how the homomorphic images and inverse images of i-v fuzzy BG-subalgebra becomes i-v fuzzy BG-algebras are studied.

Optimal Control of Steel Structures by Improved Particle Swarm

Saeid Aghajanian,Hadi Baghi,Fereidoun Amini,Masoud Zabihi Samani 한국강구조학회 2014 International Journal of Steel Structures Vol.14 No.2

Active control is one of the modern approaches in seismic design of steel structures. Recently, induced by economicconsiderations, especially high expenses of control systems, optimality has become an important issue. In this paper an activesystem is used to control a steel structure’s displacements by a simplified pole assignment method. To optimize the number,the locations, and the total driving force of the required actuators, an improved particle swarm algorithm is presented focusingon the parameters of the velocity equation. A Geographical neighborhood topology and an adaptive inertia weight are used toimprove the standard PSO algorithm. In addition to the local and global best solutions, the positions of the best particles inthe geographical neighborhood are mathematically represented in an additional term. The performance of the proposedalgorithm is compared with the traditional Genetic Algorithm (GA) and the standard particle swarm considering the optimalcontrol of a 12-story steel structure as a numerical example. High capabilities of the proposed method in terms of the controltarget, convergence rate, and accuracy are simultaneously clarified by the results.