Ablation behavior of organoclay‐NBR insulator: Modeling and experimental

Nitrile‐based nanocomposite heat insulators are very attractive materials compared with their similar nonelastomeric counterparts, due to their higher deformation bearing capacity in special applications. Modeling of these ablative nanocomposites enables us to determine the exact required thickness of the insulator and temperature distribution across it at predetermined thermal conditions. The complete form of the ablation equation is a transient nonlinear second‐order differential equation with variable temperature‐dependent thermo‐physical properties, which must be determined during thermal degradation. In this work, in addition to experimental investigation of ablative elastomeric nanocomposites based on NBR, the ablation process is modeled analytically with perturbation theory in the Lagrangian coordinate system because of surface recession and moving boundaries. Kirchhoff transformation was used to get rid of the temperature dependence of k in each zonal of virgin and char. The theoretical results were confirmed by experimental data obtained from the oxyacetylene flame test. The results proposed a competitive nitrile‐based nanocomposite heat insulator with superior ablation properties: mass ablation rate 0.014 g s^?1, linear ablation rate 0.012 mm s^?1, and insulating index number 6800 s m^?1, under a standard test with a heat flux of 2500 kW m^?2 for 15 seconds.     

Occurrence and distribution of leachate in a solid waste landfill: A field‐scale study

A field‐scale analysis for leachate flow was done for Sections 1/9 and 6/7 of the Fresh Kills landfill at Staten Island, New York. The leachate monitoring programme included field data collection of the leachate mound level for a six‐month period. The monitoring points consisted of discretely screened piezometers and wells set at various depths down to the bottom of the landfill. The position of the iso‐leachate mound head lines, derived from the field data, represented and delineated the shape of the leachate mound inside the landfill. The field data of the leachate mound head were used in the analysis of the hydraulic properties of the refuse and leachate flow rates through Sections 1/9 and 6/7 of the landfill. Piezometers and wells installed near the existing leachate collection line in Section 1/9 helped establish the gradients from which a refined estimate of the hydraulic conductivity was made. From the leachate mound head contours and flow gradients, contributions of flow from different sections of the mound were identified. Finally, the leachate flow rates were computed using Darcy's law.     

Control of the Interfacial Reactions in Nb-Toughened MoSi2

Toughening of MoSi₂ for high-temperature applications can be achieved by incorporating ductile refractory-metal reinforcements, provided that a coating is applied to prevent interdiffusion and reaction between the matrix and the reinforcements. In the present study, three different coating techniques for applying a thin Al₂O₃ film on Nb reinforcements as a diffusion barrier have been studied. The techniques consisted of (i) sol-gel coating; (ii) physical vapor deposition (PVD); (iii) hot dipping in molten Al, followed by anodizing Al to form Al₂O₃. The processing parameters for the techniques were evaluated and the effectiveness of each coating as a diffusion barrier was assessed. For the present MoSi₂ matrix which contains SiO₂, PVD coatings provided the most effective diffusion barrier for processing MoSi₂/Nb composites.     

Multi-criteria Decision Making for Integrated Urban Water Management

The city of Zahedan, in South-eastern Iran, has high population growth, limited local freshwater resources and inadequate water distribution system resulting in water supply failures in recent years. This paper will investigate integration of several demand management measures such as leakage detection on water distribution network, water metering and low volume water fixtures as well as the conjunctive use of surface and groundwater resources of this city. For integration of water management criteria, compromise programming will be used as a multi-objective decision making method. The criteria include minimizing the cost, maximizing water supply and minimizing the social hazards due to the water supply operations. This model will derive optimum long-term plans for implementation of water resources. The results will show that demand management can delay a water transfer project for Zahedan city up to 10 years. Compromise programming is as an efficient tool for integrated water resources management in urban areas and the method is capable to being used by decision-makers in other cases.     

Reliability-based maintenance scheduling of hydraulic system of rotary drilling machines

Hydraulic system has a critical and important role in drilling machines. Any failure in this system leads to problems in power system and machine operation. Since the failure cannot be prevented entirely, it is important to minimize its probability. Reliability is one of the most efficient and important method to study safe operation probability of hydraulic systems. In this research, the reliability of hydraulic system of four rotary drilling machines in Sarcheshmeh Copper Mine in Iran has been analyzed. The data analysis shows that the time between failures (TBF) of Machines A and C obey the Weibull (2P) and Weibull (3P) distribution, respectively. Also, the TBF of Machines B and D obey the lognormal distribution. With regard to reliability plots of hydraulic systems, preventive reliability-based maintenance time intervals for 80% reliability levels for machines in this system are 10 h.     

A Fuzzy Variable Least Core Game for Inter-basin Water Resources Allocation Under Uncertainty

In this paper, a new solution concept, called Fuzzy Variable Least Core (FVLC), is developed for fuzzy cooperative games. The FVLC is able to incorporate fuzzy input variables and result in fuzzy benefit shares of players participating in a coalition. This solution concept is used for water and benefit allocation to water users in inter-basin water transfer systems considering the uncertainties associated with their benefit coefficients. In the proposed water allocation methodology, an Integrated Stochastic Dynamic Programming (ISDP) model is developed to obtain the water rights of players and economic water allocation policies. In the next step, the total net fuzzy benefit of the system is reallocated to water users in an equitable and rational way using a FVLC-based model. In this model, a new algorithm is proposed for converting a multilateral cooperative game with fuzzy variables to some fuzzy bilateral cooperative games, which are solved using the FLVC solution concept. The applicability and efficiency of the proposed methodology is examined by applying it to a large scale inter-basin water transfer project in Iran.