We investigated a variant of the customer order scheduling problem taking into consideration due dates to minimize the total tardiness. Since the problem under study is NP-hard, we propose an efficient size reduction algorithm (SR). We perform an extensive computational experience and compare our proposition with JPO-20 matheuristic, the best existing algorithm for the problem under study. We use the Relative Deviation Index (RDI) and the Success Rate (SRa) as the statistical indicators for the performance measure. We must emphasize that SR presented the lowest average RDI (around 15.5 %), whereas the JPO-20 presented an average RDI approximately three times higher (around 52.5 %). Furthermore, the proposed SR presented a higher average SRa (around 66.9%), whereas the JPO-20 presented a lower average success (around 25.7%). Our proposal used a lower computational effort, resulting in a reduction for the computation times of approximately 22%. The obtained results point to the superiority of the proposed SR in comparison with the JPO-20.

The no-wait flow shop scheduling problem (NWFSP) plays a crucial role in the allocation of resources in multitudinous industries, including the steel, pharmaceutical, chemical, plastic, electronic, and food processing industries. The NWFSP consists of n jobs that must be processed in m machines in series, and no job is allowed to wait between consecutive operations. This project deals with NWFSP with sequence-dependent setup times for minimizing earliness and tardiness. From the literature review of the last five years in NWFSP, it is noticeable that only around 1.92% of the researchers have studied that multi-objective function, which could help to improve the productivity of industries where methods such as just in time are considered. Besides, there is no information about previous researchers that have solved this problem with sequence-dependent setup times. Firstly, a MILP model is proposed to solve small instances, and secondly, a genetic algorithm (GA) is developed as a solution method for medium and large instances. Compared with the mathematical model for small instances, the GA obtained the optimal solution in 100% of the cases. For medium and large instances, the GA improves in an average of 31.54%, 38.09%, 44.58%, 47.72%, and 37.33% the MDD, EDDP, ATC, SPT, and LPT dispatching rules, respectively.

The main aim of this paper is to present a novel multi-objective gray wolf optimization (MOGWO) by utilizing the Kriging meta-model. To this end, surrogate models are used in Multi-Objective Gray Wolf Optimizer as the fitness function. The meta-model is obtained based on exact analysis and numerical simulations. Inheritable Latin Hypercube Design (ILHD) is used as the design of experiments for generation and testing the Kriging model. Then, sensitivity analysis is done to evaluate the effect of design parameter on system responses. The sensitivity analysis leads to appropriate selection of optimization design variables. Hence, the MOGWO algorithm is applied to the problem, the set of non-dominated optimal points are obtained as Pareto Front and one optimal point is selected based on the minimum distance approach. The most important purpose of the methodology is to improve the time consuming in multi-objective optimization problems. In conclusion, for the design of hydrazine catalyst bed was utilized from the proposed methodology. In case, design variables are catalyst bed pellet diameter, loading factor, thrust chamber pressure and Reaction efficiency and objective functions are increasing performance and reducing mass and pressure drop. The results of optimal catalyst bed parameters and also corresponding value of objective functions are shown the performance of methodology in the space propulsion system applications.

This work presents a stress-strain state analytical estimation of restored tooth hard tissues with consideration of their contact interactions with a monolithic filling or a dental onlay. The tooth with a defect is simulated as a continuous isotropic cylindrical body with a non-through hole, and the filling or onlay is simulated as an elastic deformable cylinder. The contact between the tooth and the fillings (onlay) is simulated as the ideal contact. The final strength estimation of the restored tooth is carried out according to the energy criterion. The authors suggest a linear index of tooth damage for practical application of the obtained results. This index can be easily obtained by direct measurement. The differential approach is developed to select a restoring method of the tooth with the defect to provide a reliable restoration of the anatomical crown of the tooth.

Composite materials show different mechanical properties in different directions which leads to complications in the prediction of their behavior. In addition to being inhomogeneous, behavior of composite materials is highly dependent on the curing process and many studies have tried to address these issues. Residual stress can induce high errors in prediction of composite material properties and leads to a difference between theoretical and experimental results. It has been observed that the humidity of environment and the chemical properties of composite materials are also important. Fewer studies have addressed thick layer composites and no damage theory has been developed for these materials. In this paper residual stress in thick layer composites have been studied. Using numerical analysis, the curing process has been modeled and mechanical properties of a thick layer composite are obtained and the induced residual stress in these composites has been assessed. Unlike thin layer composites, the stress in each layer is not specific and a tensile and compressive stress field can exist simultaneously in thick layer composites.

Strategic management in a port system is complex since the Port Community has to coordinate actions and generate synergy among all the private actors that integrate the export and import logistics chains, trade associations and trade unions. Based on the opinion of the port experts and the analytical network process (ANP), the research identifies the relevant criteria for strategic, business and operational decision-making in the Port Community, in the technological and risk contexts. With the criteria found and considering the strategic alignment that is required, management indicators are constructed. Based on a generic model, a new strategic conceptual model (PORTGD) of ANP for decision management is designed for the Port Community, a cause and effect analysis is carried out and a sensitization study is performed on the nodes. The discussion of the results and conclusions highlights the importance of technological investment, control of port security and good practices for the port system investigated.

This study aims to understand the uncertainty about the optimum or best pin position (Dp) for friction stir lap welding (FSLW) of Al-Cu. Tensile shear testing is used to determine the Mechanical strength of FSL welds under static loading. Fracture strength (σLap) corresponding to the maximum load in a test over the sample width is used as the strength value. Interface microstructures differ depending on whether the tool pin penetrates the lapping interface. It has been found that σLap values of the defect free weld samples vary quite significantly and in general are significantly higher than those reported in the literature. When the pin penetration is close to zero no intermetallic layers were formed, hence the value of σLap was zero. When the pin penetration is 0.4mm, the commonly observed a thin Al–Cu interface layer forms and this layer does not grow beyond 3µm. It is shown that the thin interfacial layer can withstand a high tensile-shear load and thus the adjacent Al material shears to fracture. When the pin penetrates more than 0.4mm, the commonly observed mix stir zone (MSZ) forms and values of σLap are lower than that of 0.4mm pin penetration welds but remain quite high.

Risk response planning is a widely concerned issue. Project managers usually struggle to control different kinds of risks. In project risk management, after evaluating risks, the final process relates to choosing desirable responses to the risks. In this paper, a comprehensive framework confronts the issue in three main phases. In the first phase, all the risks, responses and their relations in a geothermal drilling project are detected. These relations imply there are inner dependent and outer dependent relations. In the second phase, ANP, DEMATEL and fuzzy theory play important roles in weighting risks and responses. In the third phase, to enable a more realistic solution, a zero-one integer programming reflects a budget constraint and other required constraints. After obtaining the optimal responses, the effect of budget is analyzed. In addition, the influences of risks on each other are discussed more deeply. Collectively, this study offers a new perspective on how to handle project risks and choose their responses

The concept of a deformable body point is taken in the form of a continuum point and an elementary volume connected with it. The continuum point determines the spatial position of the deformable body point, and the elementary volume is the carrier of its material properties and stress-strain state characteristics. Based on this representation, restrictions on the state parameters at the edge points (singular points) of an isotropic body are constructed. These restrictions become preset conditions in singular points. The study covers possible interactions of the edge-forming surfaces with the external environment. It is shown that the restrictions formed at the edge points are usually more numerous than the restrictions at the regular point on the surface of a deformable body. This circumstance leads to a non-classical formulation of the mechanics problem for bodies with singular points. The combinations of geometric and material parameters of a structural component are discovered that determine the singular stresses behavior in elementary volumes with edge points. The load restrictions ensuring the compatibility of parameters defined at singular points are formulated. The attained results will apply to studying stress concentration in the vicinity of 3D-edges of structural components.

The purpose of this study is to develop a fuzzy Analytic Network Process (ANP) model that has the ability to evaluate employee performance in different strategies. A team of experts in the field of strategic human resource management and senior management of an organization engaged in steel production were involved in the study. The data collection tool was a questionnaire that was designed based on the criteria of organization's performance appraisal system. The results showed that in cost leadership strategy, compliance of work hierarchy, quantity of work and the ability to make important decisions constituted the highest coefficients, while in the focus strategy, participate in group work, power of supervision and administration and decision making ability had the highest importance. In differentiation strategy, innovation and creativity, quality and offering constructive suggestions received higher ratings than other criteria. Finally, the developed model was used to evaluate the performance of a sample employee.