Diagnosing double regular systems

We consider the problem of testing sequentially the components of a multi-component system, when the testing of each component is costly. We propose a new testing policy, that can be executed in polynomial time in the input size, and show that it is cost-minimal in the average case sense, for certain double regular systems that include regular (in particular, threshold) systems with identical components. This result generalizes known results for series, parallel, and, more generally, for k-out-of-n systems. This revised version was published online in June 2006 with corrections to the Cover Date.     

TestAnt: An ant colony system approach to sequential testing under precedence constraints

We consider the problem of minimum cost sequential testing (diagnosis) of a series (or parallel) system under precedence constraints. We model the problem as a nonlinear integer program. We develop and implement an ant colony algorithm for the problem. We demonstrate the performance of this algorithm for special type of instances for which the optimal solutions can be found in polynomial time. In addition, we compare the performance of the ant colony algorithm with a branch and bound algorithm for randomly generated general instances of the problem. The ant colony algorithm is particularly effective as the problem size gets larger.     

Residual acrylic monomer content of denture base resins with different fiber systems

The conversion of monomer to its polymer may not be complete and residual monomer is left over in the polymeric matrix; this, in turn, affects the properties of the polymeric matrix. In this study, we wanted to compare residual monomer content of the unreinforced conventional heat-polymerized and microwave-polymerized acrylic resins with those of fiber-reinforced ones. High performance liquid chromatography was used for the determination of the residual monomer content. Statistical analysis of the results was carried out with a confidence level of 95%. It was observed that conventional heat-polymerized denture base resin resulted in a relatively higher residual monomer content than the microwaved one. Conventional heat-polymerized denture base resin with fiber reinforcement caused an increase in the residual monomer content. Furthermore, the change in the residual monomer content of microwave-polymerized denture base resin with fiber reinforcement was not statistically significant compared with no fiber reinforcement. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Comparative study of the mechanical properties of fiber‐reinforced denture base resin

Poly(methyl methacrylate) (PMMA) is used for removable prostheses. However, PMMA denture base resin does not meet all the mechanical requirements of prostheses. The aim of this in vitro study was to compare the transverse strength, modulus of elasticity, and impact strength values of nonreinforced heat‐polymerized and microwave‐polymerized denture base resin with those of denture base resin reinforced with continuous unidirectional E‐glass, woven E‐glass, and ultrahigh‐molecular‐weight polyethylene fibers. The mechanical properties of polymer reinforced with polyethylene fibers showed no significant increase in flexural properties. However, reinforcement with Stick fiber improved the mechanical properties. The test specimens that expressed low fracture strength values showed void spaces inside the test specimens. © 2009 Wiley Periodicals, Inc. J Appl Polym, 2009     

Mechanical,vulcametric, and thermal properties of the different 5‐ethylidene 2‐norbornene content of ethylene‐propylene‐diene‐monomer vulcanized with different types and compositions of peroxides

Ethylene‐propylene‐diene‐monomer (EPDM) rubber is an important commercial polymer. The vulcanization process significantly changes its thermal, mechanical, and vulcametric properties. This study was carried out to find optimum formulation of EPDM composite for a better application in automotive industry. Sixteen EPDM polymer samples having different 5‐ethylidene 2‐norbornene (ENB) and ethylene contents were vulcanized with different types and compositions of peroxide and coagents. The mechanical and vulcametric properties of these samples were measured and compared. The type of peroxide, coagent, and EPDM grade affected the mechanical, thermal, and vulcametric properties of the EPDM rubber to some extend. Use of aromatic peroxide and coagent increased the thermal stability slightly. Mechanical properties were changed very slightly with the change of peroxide type for the same content of peroxide and coagent. Scorch time and cure time decreased with initial increase of the peroxide content. EPDM compound vulcanized with BBPIB peroxide and TAC/S coagent has higher cure time than EPDM compound vulcanized with DMBPHa peroxide and TMPTMA coagent. Coran method was used for the modeling of experimental data. Velocity constant for the formation of peroxide radical and polymer radical were found for each case. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Optimization of the vulcanization parameters for ethylene–propylene–diene termonomer (EPDM)/ground waste tyre composite using response surface methodology

The utilization of waste tyre in a green way would definitely mitigate the possible risks of the waste tyre accumulation. A green way to solution for the waste tyre problem is recycling. However, it is necessary to optimize the recycling process parameters to come up with the optimum conditions for the effective reuse of the waste tyre. In this study, response surface methodology (RSM) was used to model and optimize the parameters of curing of EPDM and waste tyre composite for the purpose of waste tyre recycling. EPDM with different loadings of ground waste tyre composites were prepared. Mechanical, thermal, and Soxhlet extraction tests were carried out for the samples. RSM was applied and process parameters were optimized. It was seen that the most effective parameter was the curing temperature. The optimal values of the parameters were determined as curing temperature of 172.1 °C, curing pressure of 15.0 MPa and ground waste tyre content of 14.8% by weight. To test the parameters determined from optimization study, the samples were prepared under optimum conditions, and it was shown that the samples prepared according to the optimum conditions have better thermal, mechanical, and curing properties. The results were heartening to pursue the waste tyre recycling option with a considerable amount of ground waste tyre content within the final composite material.     

Using fish scales (Sardina pilchardus) within ethylene‐propylene‐diene ter monomer rubber as bio‐based filler

Proper management of waste bio‐based materials is an important subject to protect the environment in a sustainable manner. In this study, ethylene‐propylene‐diene monomer (EPDM) composites with different fish scale content were prepared and properties of these composites were investigated. Mechanical tests, gel content, curing, and thermal properties were analyzed. In addition, rheological and morphological analyses were also carried out. It was seen that EPDM rubber and fish scale composite have a good compatibility. The addition of fish scale improved the mechanical properties of the final material. Moreover, an increase in gel content and in swelling ratio was obtained for the composite samples containing fish scale. Moving die rheometer tests are concluded that fish scale has acted like an agent that improves the vulcanization process. Thermal gravimetric analysis result pointed out that the thermal stability of the composite developed is higher than neat EPDM. It was concluded that 40 phr fish scale content gives best results. The kinetic study demonstrated that fish scale is compatible with the matrix and improves the vulcanization process. The results have shown that using the fish scale as a bio‐based filler is a facile and green way to accommodate the bio‐based wastes. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46698.     

A penalty-based scaling algorithm for the multi-period multi-product distribution planning problem

Multi-period multi-product distribution planning problems are depicted as multi-commodity network flow problems where parameters may change over time. The corresponding mathematical formulation is presented for a discrete time setting, and it can also be used as an approximation for a continuous time setting. A penalty-based method which employs a cost-scaling approach is developed to solve some auxiliary penalty problems aiming to obtain an optimal solution for the original problem. The experiments on both random instances and case study problems show that the algorithm finds good-quality solutions with reasonable computational effort.