A novel approach for measuring the maximum process-loss information in multiple production line conditions

The process-loss index L_e , the expected value of the ratio of the quadratic loss function to the square value of half specification width, proposed by Johnson (1992 Johnson, T. 1992. The relationship of C_pm to squared error loss. Journal of Quality Technology, 24(4): 211–215. [Taylor &; Francis Online], [Web of Science ®] , [Google Scholar], The relationship of C_pm to squared error loss. Journal of Quality Technology, 24 (4), 211–215), has been widely used in a variety of industries to provide a numerical loss measure for assessing the performance of their production processes. However, the sampling distribution of its uniformly minimum variance unbiased estimator (UMVUE), obtained from traditional approaches involving unknown parameters, is able neither to form classical confidence intervals (CCIs) nor to provide justifiable process-loss information in practice. To tackle this disadvantage, in this paper a novel approach known as generalised confidence intervals (GCIs) is adopted. Instead of Monte Carlo simulations that were popularly utilised in implementing the GCIs method for assessing production process performance, we theoretically derive analytical forms of upper confidence bounds (L _e -GUCB) for L _e and program them to provide the maximum process-loss information for the manufacturing processes. Two common manufacturing scenarios are presented in order to work out: (1) whether the underlying production process loss is capable (or whether products received from one supplier are acceptable); and (2) whether the maximum process-loss information existing in multiple production line conditions is acceptable (or whether products received from several suppliers are acceptable). The applicability of the results is demonstrated by two examples.     

Setting planned orders in master production scheduling under demand uncertainty

For single end-product master production scheduling with time-varying demand uncertainty and supply capacity, we study approaches to set replenishment quantities over the planning horizon. We present a stochastic programming model along with a simulation-based optimisation and two traditional approaches for setting order quantities. We compare these approaches to two new methods: gamma approximation and safety stock search. Computational experiments show that the gamma approximation and safety stock search perform well in terms of holding and shortage costs, with expected total cost on average, respectively, within 0.06% and 0.66% of the optimal from the stochastic program. On average, the two traditional approaches incur 12% and 45% higher cost than optimal. We provide managerial insights on the effects of parameters such as demand coefficient of variation (cv), utilisation, and target service level on the optimal total cost, the corresponding fill rate, and the relative performance of the approaches. We find that, for finite-normal demand, on average, the impact of target service level on cost is larger than that of demand cv, whose impact is larger than utilisation, except at high utilisation. We illustrate that, when demand is not normal, the gamma approximation significantly outperforms the existing normal approximation from Bollapragada and Rao (2006 Bollapragada, R and Rao, US. 2006. Replenishment planning in discrete-time, capacitated, non-stationary, stochastic inventory systems. IIE Transactions, 38(7): 583–595.  [Google Scholar]).     

Some insights into Malakooti et al . ‘Integrated group technology,cell formation and process planning’ approach

Rajagopalan and Irani (Some comments on Malakooti et al. ‘Integrated group technology, cell formation, process planning, and production planning with application to the emergency room’. Int. J. Prod. Res., 2006, 44, 2265--2276.) provide a critique of Malakooti et al. (Integrated group technology, cell formation, process and production planning with application to the emergency room. Int. J. Prod. Res., 2004, 42, 1769–1786.) integrated cell/process/capacity formation (ICPCF) approach and suggest an improved method for solving the ICPCF problem. Rajagopalan and Irani (2006 Rajagopalan, RIrani, SA. 2006. Integrated group technology, cell formation, process planning, and production planning with application to the emergency room. Int. J. Prod. Res., 44: 2265–2276. Some comments on Malakooti[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]) attempt to solve the emergency room layout problem presented in Malakooti et al. (2004) and claim to have obtained an improved solution from their approach (hybrid flowshop layout). Although there are certain advantages of considering Rajagopalan and Irani's (2006 Rajagopalan, RIrani, SA. 2006. Integrated group technology, cell formation, process planning, and production planning with application to the emergency room. Int. J. Prod. Res., 44: 2265–2276. Some comments on Malakooti[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]) approach, we believe that their approach for solving ICPCF problems have significant shortcomings.     

Some properties of topological pressure of a semigroup of continuous maps

Based on the work of Ma and Wu,[9 Ma D, Wu M. Topological pressure and topological entropy of a semigroup of maps. Discrete Contin Dyn Syst. 2011;31:545–557.[Crossref], [Web of Science ®] , [Google Scholar]] some equivalent definitions of topological pressure of a semigroup of continuous maps are given and several of their basic properties are provided by using separated sets and spanning sets. We also answer an open problem of Bi? and Urbański.[19 Bi? A, Urbański M. Some remarks on topological entropy of a semigroup of continuous maps. Cubo. 2006;8:63–71. [Google Scholar]] That is, letting f_i, i = 2, … , k, be homeomorphisms acting on a compact metric space, G₁ = {id_X, f₂, … , f_k}, G^{? 1}₁ = {id_X, f^{? 1}₂, …, f_k^{? 1}} and letting G and G^?1 denote the semigroups generated by G₁ and G^{? 1}₁, respectively, we give an example showing that the topological entropy of G does not equal the topological entropy of G^?1.     

Lagrangian relaxation based heuristic for an integrated production and maintenance planning problem

In this paper, an approach is developed to solve the joint production planning and maintenance problem. Moreover, some propositions and mathematical properties were suggested and applied in the proposed heuristic to solve this integrated problem. It is based on Lagrangian relaxation (Fisher, M.L., 1981 Fisher, M.L. 1981. Lagrangian relaxation method for solving integer programming problem. Management Science, 27(1): 1–18. [Crossref], [Web of Science ®] , [Google Scholar]. Lagrangian relaxation method for solving integer programming problem. Management Science, 27 (1), 1–18) of the capacity constraints and sub-gradient optimisation. At every step of the sub-gradient method, a smoothing procedure is applied to the solution of the Lagrangian problem to ensure the feasibility of solution and to improve it. Computational experiments are carried out to show the results obtained by our approaches and are compared to those of a commercial solver.     

Non-Newtonian Fluids in Spout-Fluid Beds: Mass Transfer Coefficient at Low Reynolds Numbers

Following on from the work of Anabtawi et al. (2003) Anabtawi, M. Z., Hilal, N. and Al Muftah, A. E. 2003. Volumetric mass transfer coefficient in non-Newtonian fluids in spouted-fluid beds: Part I. Chem. Eng. Technol., 26: 759–764.  [Google Scholar], this study examined how the volumetric liquid-phase mass transfer coefficient, k _L a, of oxygen in air in three-phase spout-fluid beds was affected by varying the system parameters of bed height, bed diameter, gas velocity, and liquid velocity. The liquid used was 0.1% CMC solution, displaying a pseudo-plastic rheology, with 1.75 mm glass spheres as packing. The values of the Sherwood number were lower than in previous studies (Anabtawi et al., 2003 Anabtawi, M. Z., Hilal, N. and Al Muftah, A. E. 2003. Volumetric mass transfer coefficient in non-Newtonian fluids in spouted-fluid beds: Part I. Chem. Eng. Technol., 26: 759–764.  [Google Scholar]), in the range 9,000–186,000. Gas velocity had a similar effect on k _L a as in a bubble column, with results also giving good agreement with previous work on two-phase and three-phase spouted bed systems. The correlation obtained for the effect of liquid velocity on k _L a compared well with that of Schumpe et al. (1989) Schumpe, A., Deckwer, W. and Nigam, K. D. P. 1989. Gas-liquid mass transfer in three- phase fluidized beds with viscous pseudoplastic liquids. Can. J. Chem. Eng., 67: 873–877. [Crossref] , [Google Scholar]. An increase in the height of packing increased k _L a to the power of 0.319, with an increase in column diameter also causing an increase in k _L a, which is in agreement with the results of Akita and Yoshida (1973) Akita, K. and Yoshida, F. 1973. Gas hold-up and volumetric mass transfer coefficient in bubble columns. Ind. Eng. Chem. Process Des. Dev., 12: 76–80. [Crossref] , [Google Scholar].     

Steady Free Surface Flow of a Fluid-Solid Mixture Down an Inclined Plane

The present work is an extension of the investigations performed by Massoudi and Anand (2001) Massoudi, M. 2001. On the flow of granular materials with variable material properties. Inl. J. Non-linear Mech., 36: 25–37.  [Google Scholar]. The free surface flow problem is studied here. Numerical solutions for steady free surface flow of a solid-fluid mixture down an inclined plane are presented. The problem is formulated using the mixture theory framework. The resulting set of three coupled nonlinear differential equations is nondimensionalized. A parametric study is conducted to understand the influence of the dimensionless numbers on the velocity and volume fraction. The maximum fluid velocity is found to decrease with increase in the ratio of the drag force to the viscous forces within the fluid phase (D₁). The fluid phase velocity was found to decrease with increase in the ratio of the drag force to viscous force within the solid component (D₂), and the corresponding solid phase velocity was found to increase.     

A new model for the viscosity of highly concentrated multi-sized particulate Bingham slurries

Bench scale tests were carried out to investigate the rheological properties of multi-sized particulate Bingham slurries at high solid concentrations ranging from 50% to 70% by weight. In addition, rheological data from Biswas et al. (2000 Biswas, A., B. K. Gandhi, S. N. Singh, and V. Seshari. 2000. Characteristics of coal ash and their role in hydraulic design of ash disposal pipelines. Indian Journal of Engineering and Materials Sciences 7:1–7.[Web of Science ®] , [Google Scholar]) and Chandel et al. (2009, 2010) have also been considered. Based on these extensive amount of rheological data, an empirical model is proposed for viscosity as a function of solid volume fraction (?), maximum solid volume fraction (?_m), median particle diameter (d₅₀), and coefficient of uniformity (C_u) using optimization and nonlinear least-square curve-fitting technique. The proposed model shows good agreement with the experimental data considered in the present study and is found to be much better than the previously developed models in predicting the viscosity of multi-sized particulate Bingham slurries at high solid concentrations.     

Understanding why firms should invest in sustainable supply chains: a complexity approach

This paper explores why firms should include sustainable development considerations in supply chains as a means of improving social and environmental impacts of production systems. The recognition of financial, social and environmental elements however creates greater complexity, which makes optimisation approaches to sustainable supply chain problems infeasible. We frame our analysis using Kauffman's (1993) NK theory, with interactions among financial, social and environmental elements identified through empirical research conducted in Brazilian oil and gas, sugarcane ethanol and biodiesel supply chains. We use a matrix of interactions (Baldwin and Clark 1999 Baldwin, C and Clark, K. 1999. Design rules: the power of modularity, Cambridge, MA: The MIT Press.  [Google Scholar]) as a template, allowing for the identification of key financial, social and environmental elements and their interconnections within and between supply chains. We contribute by arguing that firms focusing on individual sustainable development elements independently are unlikely to find satisfactory solutions to their sustainable supply chain problems. We further argue that certain sectors have a propensity to be socially exclusive, whereas others are potentially socially inclusive; in such cases, firms operating in exclusive sectors may be able to find satisfactory solutions to their broader sustainability strategies by investing in the social and environmental performance of other supply chains.     

Measures of problem uncertainty for scheduling with interval processing times

The paper deals with scheduling under uncertainty of the job processing times. The actual value of the processing time of a job becomes known only when the schedule is executed and may be equal to any value from the given interval. We propose an approach which consists of calculating measures of problem uncertainty to choose an appropriate method for solving an uncertain scheduling problem. These measures are based on the concept of a minimal dominant set containing at least one optimal schedule for each realization of the job processing times. For minimizing the sum of weighted completion times of the $n$ jobs to be processed on a single machine, it is shown that a minimal dominant set may be uniquely determined. We demonstrate how to use an uncertainty measure for selecting a method for finding an effective heuristic solution of the uncertain scheduling problem. The efficiency of the heuristic $O(n\log n)$ -algorithms is demonstrated on a set of randomly generated instances with $100 \le n \le 5{,}000.$ A similar uncertainty measure may be applied to many other scheduling problems with interval processing times.     

Balancing and sequencing of parallel mixed-model assembly lines

In this paper, a simulated annealing approach is developed for the parallel mixed-model assembly line balancing and model sequencing (PMMAL/BS) problem which is an extension of the parallel assembly line balancing (PALB) problem introduced by Gökçen et al. (2006 Gökçen, H and A?pak, K. 2006. A goal programming approach to simple U-line balancing problem. European Journal of Operational Research, 171(2): 577–585. [Crossref], [Web of Science ®] , [Google Scholar]). In PALB, the aim is to balance more than one assembly line together. Balancing of the lines simultaneously with a common resource is very important in terms of resource minimisation. The proposed approach maximises the line efficiency and distributes the workloads smoothly across stations. The proposed approach is illustrated with two numerical examples and its performance is tested on a set of test problems. The computational results show that the proposed approach is very effective for PMMAL/BS.     

Some comments on Malakooti et al. ‘Integrated group technology,cell formation,process planning,and production planning with application to the emergency room’

In this technical note, we suggest an alternative to the cellular layout for the emergency room problem discussed in Malakooti et al. (Malakooti, B., Malakooti, N.R. and Yang, Z., Integrated group technology, cell formation, process planning, and production planning with application to the emergency room. Int. J. Prod. Res., 2004, 42(9), 1769–1786). The alternative layout—hybrid flowshop layout—belongs to a class of hybrid cellular layouts that can be designed using the integrated suite of algorithms available in the production flow analysis and simplification toolkit (PFAST) software (Irani, S.A., Zhang, H., Zhou, J., Huang, H., Tennati, K.U. and Subramanian, S., Production flow analysis and simplification toolkit (PFAST). Int. J. Prod. Res., 2000, 38(8), 1855–1874). These layouts are intermediate between the traditional layout extremes—process layout and cellular layout—for a high-variety low-volume (HVLV) manufacturing facility. Our results indicate that the hybrid flowshop layout is superior to the cellular layout since it eliminates/reduces the duplication of procedures1 ¹?A ‘procedure’ and a ‘patient’ in the emergency room layout problem are analogous to ‘machines (or work centres)’ and ‘parts (or products)’, respectively, in a typical manufacturing facility layout problem. , backtrack flows between non-adjacent procedures and by-pass flows between procedures.     

A cuckoo search algorithm by Lévy flights for solving reliability redundancy allocation problems

A new metaheuristic optimization algorithm, called cuckoo search (CS), was recently developed by Yang and Deb (2009 Yang, X.S. and Deb, S., 2009. Cuckoo search via Lévy flights. In: Proceedings of world congress on nature &; biologically inspired computing (NaBIC 2009), 9–11 December 2009, Coimbatore, India. Piscataway, NJ: IEEE Press, 210–214.[Crossref] , [Google Scholar], 2010 Yang, X.S. and Deb, S., 2010. Engineering optimisation by cuckoo search. International Journal of Mathematical Modelling and Numerical Optimisation, 1, 330–343. doi: 10.1504/IJMMNO.2010.035430[Crossref] , [Google Scholar]). This article uses CS and Lévy flights to solve the reliability redundancy allocation problem. The redundancy allocation problem involves setting reliability objectives for components or subsystems in order to meet the resource consumption constraint, e.g. the total cost. The difficulties facing the redundancy allocation problem are to maintain feasibility with respect to three nonlinear constraints, namely, cost, weight and volume-related constraints. The redundancy allocation problems have been studied in the literature for decades, usually using mathematical programming or metaheuristic optimization algorithms. The performance of the algorithm is tested on five well-known reliability redundancy allocation problems and is compared with several well-known methods. Simulation results demonstrate that the optimal solutions obtained by CS are better than the best solutions obtained by other methods.     

A corrected formulation for the double row layout problem

This paper presents a corrected formulation to the mixed integer programming model of the double-row layout problem (DRLP), first proposed by Chung and Tanchoco (2010 Chung, J and Tanchoco, J. 2010. The double row layout problem. International Journal of Production Research, 48(3): 709–727. [Taylor &; Francis Online], [Web of Science ®] , [Google Scholar], The double row layout problem. International Journal of Production Research, 48 (3), 709–727). In the DRLP, machines are placed along two rows of a corridor, where the objective is to minimise the total cost of material handling for products that move between these machines. We highlight the errors in the original formulation, propose corrections to the formulation, and provide an analytical validation of the corrections.     

Integrated model for determining the optimal initial settings of the process mean and the optimal production run assuming quadratic loss functions

Chen and Chung (1996 Chen, SL and Chung, KJ. 1996. Determining the optimal production run and the most profitable process mean for a production process. International Journal of Production Research, 34: 2051–2058.  ) addressed the problem of the joint determination of the optimal process mean and production run for an industrial process. Their study considered a product with an upper and a lower specification limit. The optimal process mean and optimal production run were obtained by balancing the profit of meeting and not meeting the specification limits. However, Chen and Chung did not consider the quality cost for the product within the specification limits. The present paper revisits the problem and incorporates the quality cost by introducing a Taguchi loss function for determining simultaneously the optimal process mean and production run. As per Chen and Chung, the present paper assumes a 100% inspection scheme. It also investigates the differences between Chen and Chung's approach and the Reward Theorem approach. A sample inspection scheme is also proposed. Numerical examples are provided to demonstrate the application of the model. A sensitivity analysis of the model is provided. Some new directions for further research are also outlined.     

An objective function to address production sequencing with minimal tooling replacements

A strategy is presented to obtain production sequences resulting in minimal tooling replacements. An objective function is employed to distribute the tool wear as evenly as possible throughout the sequence. This objective function is an extension of Miltenburg's earlier work (1989 Miltenburg, J. 1989. Level schedules for mixed-model assembly lines in just-in-time production systems. Manage. Sci., 35: 192–207. [Crossref], [Web of Science ®] , [Google Scholar]) concerned with obtaining production sequences while evenly distributing the satisfaction of demand. Smaller problems are solved to optimality, while larger problems are solved as close as possible to optimality. The production sequences are simulated to estimate required tooling replacements. The methodology presented here consistently results in fewer tooling replacements when compared with earlier published work (McMullen et al. 2002 McMullen, PR, Clark, M, Bell, J and Albritton, D. 2002. A correlation and heuristic approach to production sequences with uniformity of tool wear. Comp.?&;?Op. Res., 30: 435–454.  [Google Scholar], McMullen 2003 McMullen, PR. 2003. Sequencing for minimal tooling replacements via a variety of objective functions. Int. J. Prod. Res., 41: 2183–2199. [Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]).     

Measuring production yield for processes with multiple quality characteristics

Process yield is an important criterion used in the manufacturing industry for measuring process performance. Methods for measuring yield for processes with single characteristic have been investigated extensively. However, methods for measuring yield for processes with multiple characteristics have been comparatively neglected. In this paper, we develop a generalized yield index, called TS _pk,PC , based on the index S_pk introduced by Boyles (Journal of Quality Technology, 23, 17–26, 1991 Boyles, RA. 1991. The Taguchi capability index. J. Qual. Technol., 23: 17–26. [Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]) using the principal component analysis (PCA) technique. We obtained a lower confidence bound (LCB) for the true process yield. The proposed method can be used to determine whether a process meets the preset yield requirement, and make reliable decisions. Examples are provided to demonstrate the proposed methodology.     

An efficient imperialist competitive algorithm for scheduling in the two-stage assembly flow shop problem

This paper considers a two-stage assembly flow shop problem where m parallel machines are in the first stage and an assembly machine is in the second stage. The objective is to minimise a weighted sum of makespan and mean completion time for n available jobs. As this problem is proven to be NP-hard, therefore, we employed an imperialist competitive algorithm (ICA) as solution approach. In the past literature, Torabzadeh and Zandieh (2010 Torabzadeh, E., and M. Zandieh. 2010. “Cloud theory-based Simulated Annealing Approach for Scheduling in the Two-stage Assembly Flow Shop.” Advances in Engineering Software 41: 1238–1243.[Crossref], [Web of Science ®] , [Google Scholar]) showed that cloud theory-based simulated annealing algorithm (CSA) is an appropriate meta-heuristic to solve the problem. Thus, to justify the claim for ICA capability, we compare our proposed ICA with the reported CSA. A new parameters tuning tool, neural network, for ICA is also introduced. The computational results clarify that ICA performs better than CSA in quality of solutions.     

Creeping Flow of Viscoelastic Fluid Through a Packed Bed: Effect of Particle Shape and Porosity

Experiments were conducted to elucidate the effect of particle shape and porosity on frictional pressure drop for the flow of viscoelastic fluids through a packed bed under creeping flow regime. Extensive pressure drop-flow rate data were generated using different packing materials such as cylinders of different aspect ratios, square plates, triangles, and spheres covering a wide range of sphericity, 0.546 ≤ φ ≤ 1. Effect of bed porosity has been determined using uniform-size spheres of different diameters (4.38 mm, 5.76 mm, and 6.78 mm), covering column to particle diameter ratio in the range of 13.96–21.62; while porosity varies in the range of 0.345–0.375. The experimental results indicate that the modified Ergun correlation, proposed by Sobti and Wanchoo (2014 Sobti, A., and R. K. Wanchoo. 2014. Creeping flow of viscoelastic fluid through a packed bed. Industrial & Engineering Chemistry Research 53:14508–14518.[Crossref], [Web of Science ®] , [Google Scholar]), can adequately be applied for the nonspherical particles, provided the equivalent volume mean diameter (D_eq) together with sphericity (φ) is used instead of the diameter of the spherical particle (D_p), i.e., D_p = D_eqφ. Further, an attempt has been made to suitably define a packing structure parameter, [(1 ? ?)/(? φ)], which could well capture the balancing effect between porosity and sphericity.     

A membership function approach for aggregate production planning problems in fuzzy environments

This paper proposes a novel approach for the aggregate production planning (APP) problem with fuzzy parameters. Different from the results of previous studies, in this paper the membership function of the fuzzy minimal total cost is constructed based on Zadeh's extension principle and fuzzy solutions are provided. A pair of mathematical programs parameterised by possibility level α is formulated to calculate the lower and upper bounds of the fuzzy total cost at α. By enumerating different values of α, the membership function of the fuzzy total cost is constructed. To illustrate the validity of the proposed approach, the example studied by Lai and Hwang (1992 Lai, YJ and Hwang, CL. 1992. Fuzzy mathematical programming: methods and applications, Berlin: Springer.  [Google Scholar]) using Chanas's approach is investigated. Since the objective value is expressed by a membership function rather than by a crisp value, the proposed approach can represent APP systems more accurately, thus obtained solutions which contain more information can offer more chance to achieve the feasible disaggregate plan, and it is beneficial to the decision-maker in practical applications. The proposed approach can also be applied to APP problems with other characteristics.