Wireless Personal Communications - One of the main concerns at the time of production or share of information on social networking sites for scientific research and business analysis is privacy.... 相似文献
Poly(ethylene tetrasulfide) (PSP) is synthesized via interfacial polycondensation of 1,2 dichloroethane and sodium tetrasulfide, in the presence of graphene oxide (GO). This process resulted in homogeneously dispersed PSP/GO nanocomposites. Nanocomposites of 0.3 and 0.5?wt% of GO are synthesized and their morphology, chemical characteristics behavior are studied employing field emission scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction techniques. Thermal characterization of composites is performed by differential scanning calorimetry and thermogravimetry analysis. Results indicate that the addition of only small amounts (0.5?wt%) of well-dispersed GO can increase the melting point more than 16°C resulting in better thermal properties for the composite. The solubility of nanocomposite is also studied and results show that the solubility depends on solvent concentration in addition to reinforcement (GO) deals. 相似文献
Today's strict environmental laws pose significant challenges for coating's formulators to look for eco-friendly products. Powder coatings, particularly polyester/epoxy blends have demonstrated their ability as alternatives to traditional solvent-borne coatings. Recently, the use of nanoparticles such as nano-CaCO3 (nCaCO3) has been suggested as a beneficial strategy towards powder coating application with improved properties. Here, we study the effect of nCaCO3 on morphology, cure behavior, adhesion and hardness of polyester/epoxy systems. The nanoparticles shape, size and dispersion state were investigated through X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) methods. Furthermore, isothermal cure characterization of the neat and filled systems was performed using a torque rheometer. The most important finding based on the rheological studies was the catalytic effect of nCaCO3 on cure reaction of polyester/epoxy, leading to the shorter curing time. Moreover, the kinetic analyses of rheograms revealed a marked decrease in the activation energy of the cure process upon raising nCaCO3 content. Interestingly, pull-off adhesion and hardness tests showed that the hardness and adhesion strength were dramatically increased by the addition of nCaCO3 into the polyester/epoxy system compared to pure blend resin. Therefore, considering the strong competition in powder coating market, the use of nCaCO3 as a commercial and inexpensive nanofiller is necessary not only to reduce the dwell time which has benefits in terms of the energy consumption and economics, but also to improve the performance of final polyester/epoxy coating. 相似文献
In spite of the classic approaches of solution of dynamic facility layout problem, which only material handling and rearrangement costs are considered as objective function, these problems are the multi-objective problems. In this paper, a mixed integer linear programming formulation is presented for multi-objective dynamic facility layout problem concerning flexible bay structure. In addition, three current objectives in dynamic facility layout problems including minimizing material handling and rearrangement costs, maximizing adjacency rate, and minimizing shape ratio difference have been considered. Also, for solving this problem, two methods including the GAMS software and proposed parallel variable neighborhood search (PVNS) algorithm are used. So, it is worth mentioning that four test problems are solved by them, and the results show that the proposed PVNS algorithm is more efficient than the GAMS software. 相似文献
This paper addresses the problem of no-wait two-stage flexible flow shop scheduling problem (NWTSFFSSP) considering unrelated parallel machines, sequence-dependent setup times, probable reworks and different ready times to actualize the problem. The performance measure used in this study is minimizing maximum completion time (makespan). Because of the complexity of addressed problem, we propose a novel intelligent hybrid algorithm [called hybrid algorithm (HA)] based on imperialist competitive algorithm (ICA) which are combined with simulated annealing (SA), variable neighborhood search (VNS) and genetic algorithm (GA) for solving the mentioned problem. The hybridization is carried out to overcome some existing drawbacks of each of these three algorithms and also for increasing the capability of ICA. To achieve reliable results, Taguchi approach is used to define robust parameters' values for our proposed algorithm. A simulation model is developed to study the performance of our proposed algorithm against ICA, SA, VNS, GA and ant colony optimization (ACO). The results of the study reveal the relative superiority of HA studied. In addition, potential areas for further researches are highlighted. 相似文献
Currently, data centers are considered as the most important parts of internet services such as electronic commerce, social networks and mobile networks. The increasing number of mobile users on the one hand, and the use of data traffic on the other, have led LTE operators to find new methods for more optimized and faster data centers localization.
The role of data centers in LTE networks is very important because they have the task of maintaining the mobile network functions, which play a key role in processing requests and information and responding to user requests. According to the population density criterion, inaccurate location of data centers will increase the cost and time to respond to user requests. Because failing to put the data center in its proper place increases the number of requests that users send to that data center, which increases response time. Therefore, the introduction of new methods and models in this field can be of great importance. In this article, in addition to proposing a new mathematical model for data centers positioning via applying a meta-heuristic algorithm, we will search for optimized data centers positioning in a faster and more scalable way. Based on the results, the model presented in this paper has been able to show significant results in terms of scalability in the number of data centers and the number of requests as well as the response time of the users’ requests. In addition, the implementation of this model using TABU Search algorithm has optimized the results.
The performance of potassium carbonate (K2CO3) solution promoted by three amines, potassium alaninate (K-Ala), potassium serinate (K-Ser) and aminoethylethanolamine (AEEA), in terms of heat of absorption, absorption capacity and rate was studied experimentally. The experiments were performed using a batch reactor, and the results were compared to pure monoethanolamine (MEA) and K2CO3 solutions. The heat of absorption of K2CO3+additive solution was calculated using the Gibbs-Helmholtz equation. In addition, a correlation for prediction of CO2 loading was presented. The results indicated that absorption heat, absorption rate and loading capacity of CO2 increase as the concentration of additive increases. The blend solutions have higher CO2 loading capacity and absorption rate when compared to pure K2CO3. The heat of CO2 absorption for K2CO3+additive solutions was found to be lower than that of the pure MEA. Among the additives, AEEA showed the highest CO2 absorption capacity and absorption rate with K2CO3. In conclusion, the K2CO3+AEEA solution with high absorption performance can be a potential solvent to replace the existing amines for CO2 absorption. 相似文献
Aircraft aluminum alloys, such as 2024, generally present low weldability by traditional fusion welding processes. The development of friction-stir welding (FSW) has provided an improved alternative way to produce satisfactory aluminum joints in a faster and more reliable method. It has been demonstrated that the FSW process involves dynamic recrystallization, which leads to ultrafine and equiaxed grain structures due to the high temperatures and strains occurring during the process. In this study, the 2024 Al-alloy with annealed (O) and artificial aged (T6) conditions were friction-stir welded. Grain size distribution, hardness, and temperature profiles in the welded zones were determined to obtain the relationship between the base metal’s initial and final microstructures in these regions. The results showed that in both samples, the average grain sizes in the weld nugget were almost identical. The hardness of nugget zones in both samples was nearly the same due to their similar microstructures. According to the obtained results, the initial microstructure showed no considerable effect on the final microstructure and hardness of the weld nuggets. This may be attributed to the continuous dynamic recrystallization phenomenon that occurs during the FSW of aluminum alloys. 相似文献