M. Naderi and S. A. K. Mousavi,
Volume 26, Issue 1 (7-2007)
Abstract
Deterioration of concrete, which is mainly due to ignorance of environmental and service conditions, causes considerable costs for the construction industry. With this in mind, in this paper, results of investigation into the major causes of concrete deterioration in the Urumie Lake are presented. For the purposes of this investigation, samples were obtained by mixing two types of cement (OPC types 1&2), micro silica, anti oxide, water proof and air entraining agent, with different w/c ratios and tested at the ages of 7,14, and 28 days. In addition to compression strength, tensile strength of the samples was measured. Regarding the durability studies, abrasion resistance, electrical resistivity, chloride penetration, water absorption and freeze-thaw tests were carried out under both laboratory and real conditions in the Urumieh lake. Based on our findings recommendations are made about optimum w/c ratio, most suitable types of cement, optimum percentage of micro silica content, and additive .
R. Naderi, A. Khademalrasoul,
Volume 35, Issue 1 (9-2016)
Abstract
This study shows how to create different types of crack and discontinuities by using isogeometric analysis approach (IGA) and extended finite element method (XFEM). In this contribution, two unique features of isogeometric analysis approach are utilized to create discontinuous zones. Discontinuities consist of crack and cohesive zone. In isogeometric analysis method NURBS is used to approximate both geometry and primary variable. NURBS can create quadratic shapes exactly. Also, stress intensity factors are calculated in the vicinity of the crack tips for two dimensional problems and are compared with corresponding analytical and numerical counterparts. Extended finite element method is the other numerical method which is used in this work. The enrichment procedure is utilized in extended finite element method to create discontinuities. The well-known path independent J-integral approach is used in order to calculate the stress intensity factors. Also, in mixed mode situation, the interaction integral (M-integral) is considered to calculate the stress intensity factors. Results show that isogeometric analysis method has desirable accuracy as it uses lower degree of freedoms and consequently lower computational efforts than extended finite element method. In addition, creating the internal cohesive zone as one of the most important issues in computational fracture mechanics is feasible due to the special features of isogeometric analysis. The present study demonstrates the capability of isogeometric analysis parametric space to control the inter-element continuity and create the cohesive zone.
H. Zohali, B. Naderi, M. Mohammadi,
Volume 36, Issue 2 (3-2018)
Abstract
This paper addresses the lot sizing and scheduling problem for a number of products in flexible flow shop with identical parallel machines. The production stages are in series, while separated by finite intermediate buffers. The objective is to minimize the sum of setup and inventory holding costs per unit of time. The available mathematical model of this problem in the literature suffers from huge complexity in terms of size and computation. In this paper, a new mixed integer linear program is developed for delay with the huge dimentions of the problem. Also, a new meta heuristic algorithm is developed for the problem. The results of the numerical experiments represent a significant advantage of the proposed model and algorithm compared with the available models and algorithms in the literature.
M. Bashi Varshosaz, B. Naderi, M. Mohammadi,
Volume 37, Issue 1 (9-2018)
Abstract
The purpose of this research is to deal with the problem of two-stage assembly flow shop scheduling. A number of single-item products (identical) each formed of several different parts are ordered. Each part has m operations done at the first stage with m different machines. After manufacturing the parts, they are assembled into a final product with some non-identical machines. The purpose of the problem is to find the optimal sequence of the parts in the manufacturing stage, allocation and the optimal sequence of the products in the assembly stage. A mixed integer linear programming model and two metaheuristic algorithms, which are particle swarm with local search (MPSO) and simulated annealing (SA), are presented to solve this problem. Computational experiments are conducted to evaluate the performance of the proposed model and algorithms. The results show that the MPSO algorithm performs better than the SA one.
