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Reducing the computational workload by simplifying the analysis of karst foundations into a plane strain problem can yield significant advantages. Yet, such an approach fails in reproducing the engineering situation in a rigorous manner. In this regard, this paper proposes an upper-bound method that can effectively analyze the bearing capacity of three-dimensional karst foundations. This method is utilized to investigate the impact of various pile diameters, the ratio of roof thickness to pile diameter, and the ratio of cave width to pile diameter on the stability of karst foundations. The validity of this method is established through an illustrative example. The outcomes illustrate that when subjected to both tensile and compressive horizontal stresses if the maximum horizontal stress surpasses the tensile strength of the rock mass, the roof rock mass may suffer damage. Increasing the ratio of roof thickness to pile diameter can bring down the horizontal stress value. The stability factor is largely influenced by the ratio of roof thickness to pile diameter. The most prominent growth trend of the stability factor is observed when the ratio is less than 3. If the ratio of the roof thickness to pile diameter exceeds 3, the prediction of the bearing capacity estimation for the karst foundation in three-dimensional circumstances is more conservative than that in two-dimensional circumstances. [ABSTRACT FROM AUTHOR]

Reducing the computational workload by simplifying the analysis of karst foundations into a plane strain problem can yield significant advantages. Yet, such an approach fails in reproducing the engineering situation in a rigorous manner. In this regard, this paper proposes an upper-bound method that can effectively analyze the bearing capacity of three-dimensional karst foundations. This method is utilized to investigate the impact of various pile diameters, the ratio of roof thickness to pile diameter, and the ratio of cave width to pile diameter on the stability of karst foundations. The validity of this method is established through an illustrative example. The outcomes illustrate that when subjected to both tensile and compressive horizontal stresses if the maximum horizontal stress surpasses the tensile strength of the rock mass, the roof rock mass may suffer damage. Increasing the ratio of roof thickness to pile diameter can bring down the horizontal stress value. The stability factor is largely influenced by the ratio of roof thickness to pile diameter. The most prominent growth trend of the stability factor is observed when the ratio is less than 3. If the ratio of the roof thickness to pile diameter exceeds 3, the prediction of the bearing capacity estimation for the karst foundation in three-dimensional circumstances is more conservative than that in two-dimensional circumstances.

The Critical Path Method (CPM) has failed practically for scheduling repetitive projects and Line Of Balance (LOB) has emerged as an alternative for scheduling such projects. Because of the size of most repetitive projects, efficient resource management plays a vital role in their successful implementation. However, resource levelling and allocation have not been formally investigated in repetitive projects. Heuristic methods and optimization techniques have been traditionally used to solve resource scheduling problems like the latter. Although heuristic methods can handle large-size projects, they do not guarantee optimal solutions. In this paper, resource levelling and allocation problems under LOB scheme are modelled as an optimization problem that guarantees optimal solutions. Resource continuity and logical dependency between activities are maintained where constant activity progress rate is assumed. An example project is used to demonstrate the details of model formulation. A complete solution for the range of feasible project durations is obtained as a Time-Resource Trade-Off curve. A pipeline project is used to validate the developed model revealing that the developed model is superior. The proposed model provides contractors with a complete picture for resource usage along with the range of feasible project durations from which the optimal alternative can be selected. [ABSTRACT FROM AUTHOR]

As far as uncertainty is prevalent, financial anomalies increase the complexity of financial decisions. The possible consequence of an anomaly is either an over or underreaction. This paper suggests that the use of mathematical programming can lessen the degree of complexity when planning for financing, investment and dividend decisions. The authors develop a comprehensive form of the External Financing Needed model in order to show the generic and combined relationship among the three financial decisions. The comprehensive model shows nonlinear relationships between the three financial decisions. The paper uses a simulated numerical example to illustrate how financial objective functions (e.g. targets) can be set out under certain constraints. The latter serve as a remedy for financial anomalies. The results show that financing, investment and dividend decisions can be made optimally to serve having consistent financial statements. [ABSTRACT FROM AUTHOR]

A robust ion-exchange resin wafer electrodeionization technology was used to demonstrate the energy efficiency of impaired water desalination. The loose ion exchange resin beads used in conventional electrodeionization were immobilized and molded to form a porous resin wafer material. In this study, the energy efficiency of brackish water desalination using resin wafer electrodeionization was evaluated along with salt removal ratio, current efficiency and productivity. Several key operating factors, including treatment time, applied electrical energy and feed flow rate were selected through experimental design. In addition, the removal rate constant in resin wafer electrodeionization was determined via a pseudo first-order kinetic model, and then correlated with operation parameters. Furthermore, the prediction models of the productivity and energy consumption were established using response surface methodology. Results suggest that resin wafer electrodeionization can improve energy efficiency to greater than 35% in comparison to reverse osmosis (normally ∼12%) for impaired water desalination. The energy consumption of resin wafer electrodeionization was found to be 0.35–0.66 kWh/m 3 with productivity of 20.1–44.7 L/hr/m 2 (i.e., 5.3–11.8 gal/hr/m 2 ) for brackish water desalination. Furthermore, a preliminary economic evaluation on impaired water desalination using resin wafer electrodeionization comparable to commercial reverse osmosis process was provided. It suggests that resin wafer electrodeionization offers the potential for an abundant source of fresh water from impaired water desalination at a cost-effective manner, which should be viewed as a crucial component in the portfolio of water supply options. [ABSTRACT FROM AUTHOR]

Basic oxygen furnace slag (BOFS) exhibits highly alkaline properties due to its high calcium content, which is beneficial to carbonation reaction. In this study, accelerated carbonation of BOFS was evaluated under different reaction times, temperatures, and liquid-to-solid (L/S) ratios in a slurry reactor. CO 2 mass balance within the slurry reactor was carried out to validate the technical feasibility of fixing gaseous CO 2 into solid precipitates. After that, a multiple model approach, i.e., theoretical kinetics and empirical surface model, for carbonation reaction was presented to determine the maximal carbonation conversion of BOFS in a slurry reactor. On one hand, the reaction kinetics of BOFS carbonation was evaluated by the shrinking core model (SCM). Calcite (CaCO 3 ) was identified as a reaction product through the scanning electronic microscopy and X-ray diffraction analyses, which provided the rationale of applying the SCM in this study. The rate-limiting step of carbonation was found to be ash-diffusion controlled, and the effective diffusivity for carbonation of BOFS in a slurry reactor were determined accordingly. On the other hand, the carbonation conversion of BOFS was predicted by the response surface methodology (RSM) via a nonlinear mathematical programming. According to the experimental data, the highest carbonation conversion of BOFS achieved was 57% under an L/S ratio of 20 mL g −1 , a CO 2 flow rate of 0.1 L min −1 , and a pressure of 101.3 kPa at 50 °C for 120 min. Furthermore, the applications and limitations of SCM and RSM were examined and exemplified by the carbonation of steelmaking slags. [ABSTRACT FROM AUTHOR]

Abstract: A nonlinear, purely kinematic approach with the finite element implementation is developed to perform shakedown analysis for materials obeying a general yield condition with non-associated plastic flow. The adopted material model can be used for both isotropic materials (e.g. von Mises''s, Mohr–Coulomb and Drucker–Prager criteria) and anisotropic materials (e.g. Hill''s and Tsai-Wu criteria) with both associated and non-associated plastic flow. Nonlinear yield criterion is directly introduced into the kinematic shakedown theorem without linearization and instead a nonlinear, purely kinematic formulation is obtained. By means of mathematical programming techniques, the finite element model of shakedown analysis is formulated as a nonlinear programming problem subject to only a small number of equality constraints. The objective function corresponds to plastic dissipation power which is to be minimized and an upper bound to the shakedown load of a structure can then be obtained by solving the minimum optimization problem. A direct, iterative algorithm is proposed to solve the resulting nonlinear programming problem, where a penalty factor based on the calculation of the plastic dissipation power is used to overcome the numerical difficulty caused by the non-differentiability of the objective function in elastic areas. The calculation is entirely based on a purely kinematical velocity field without calculation of stresses. Meanwhile, only a small number of equality constraints are introduced into the nonlinear programming problem. So the computational effort is very modest. Numerical applications prove that the developed algorithm has a very good numerical stability and computational efficiency. The proposed approach can capture different plastic behaviours of materials and therefore has a very wide applicability. [Copyright &y& Elsevier]

For a nonlinear programming problem with equality constraints in a Hilbert space, a dual-type algorithm is constructed that is stable with respect to input data errors. The algorithm is based on a modified dual of the original problem that is solved directly by applying Tikhonov regularization. The algorithm is designed to determine a norm-bounded minimizing sequence of feasible elements. An iterative regularization of the dual algorithm is considered. A stopping rule for the iteration process is given in the case of a finite fixed error in the input data. [ABSTRACT FROM AUTHOR]

Abstract: Structural health monitoring of fatigue-cracked aircraft structural panels repaired with bonded FRP composite patches for extending the service life of aging aircraft has received wide attention. In this paper a method for identifying the locations and shapes of crack and disbond fronts in aircraft structural panels repaired with bonded FRP composite patches is presented. The identification is performed by minimizing the residual norm between the measured in-plane strain range on a strain measurement plane in the FRP composite patches and the calculated in-plane strain range. Several numerical examples of identification of the locations and shapes of crack and disbond fronts are examined. The effects of the number of strain measurement points, position of the strain measurement plane, and measurement errors of the in-plane strain ranges on the identification results are discussed. The validity of this identification method is verified by comparing the identification results with the exact ones. [Copyright &y& Elsevier]

This paper is devoted to a new numerical technique for the approximation of a free boundary transient flow problem. The stationary problem, obtained from a time discretization of the original transient problem, is formulated as a shape optimal design one [C.R. Acad. Sci., Paris, Ser. I, Math. 331 (12) (2000) 1005]. The discretized optimal problem, obtained via boundary element discretization, is considered as nonlinear mathematical programming where the state of the system and the design variable are taken as independent variables. To solve this nonlinear mathematical programming we use the sequential quadratic programming (SQP). Numerical results for illustrative earth dam problems are discussed. [Copyright &y& Elsevier]

This paper considers the case study of a smart microgrid district at Graciosa Island in the Canary Islands. The smart energy microgrid district consists of several households and a public use building (school) that includes renewable energy sources (photovoltaic), Li-ion batteries for electric energy storage, domestic hot water heaters acting as thermal energy storage, a pool for balancing energy consumption and supplies, and the connection to the electric grid. We have modelled such a problem as a nonlinear mathematical programming model that is linearly approximated using special ordered sets of type 2. The linear approximation is solved using Gurobi optimization software, providing close-to-optimum solutions within an interval of 15 min that allows near-real-time operation of the smart energy district. The obtained results allow advancement of the net-zero energy neighbourhood concept in all the evaluated scenarios within a daily horizon and a positive energy balance in wider horizons. Obviously, these results are obtained in part due to the magnificent insolation conditions of the Canary Islands, but they allow justifying that the appropriate use of renewable energy resources and energy storage systems together with a balancing mechanism at the district level (such as the pool in our case study) may also lead to near-net-zero energy neighbourhoods in other geographical locations. [ABSTRACT FROM AUTHOR]

This work presents optimization results obtained for a double-effect H2O-LiBr absorption refrigeration system considering the total cost as minimization criterion, for a wide range of cooling capacity values. As a model result, the sizes of the process units and the corresponding operating conditions are obtained simultaneously. In this paper, the effectiveness factor of each proposed heat exchanger is considered as a model optimization variable which allows (if beneficial, according to the objective function to be minimized) its deletion from the optimal solution, therefore, helping us to determine the optimal configuration. Several optimization cases considering different target levels of cooling capacity are solved. Among the major results, it was observed that the total cost is considerably reduced when the solution heat exchanger operating at low temperature is deleted compared to the configuration that includes it. Also, it was found that the effect of removing this heat exchanger is comparatively more significant with increasing cooling capacity levels. A reduction of 9.8% in the total cost was obtained for a cooling capacity of 16 kW (11,537.2 $·year−1 vs. 12,794.5 $·year−1), while a reduction of 12% was obtained for a cooling capacity of 100 kW (31,338.1 $·year−1 vs. 35,613.9 $·year−1). The optimization mathematical model presented in this work assists in selecting the optimal process configuration, as well as determining the optimal process unit sizes and operating conditions of refrigeration systems. [ABSTRACT FROM AUTHOR]