Comments on ‘vendor-managed inventory with consignment stock agreement for single vendor–single buyer under the emission-trading scheme’

Zanoni, Mazzoldi, and Jaber [Zanoni, S., L. Mazzoldi, and M. Y., Jaber. 2014. Vendor-managed inventory with consignment stock agreement for single vendor–single buyer under the emission-trading scheme. International Journal of Production Research 52 (1): 20–31] consider a joint economic lot size problem under the vendor-managed inventory with consignment stock agreement and an emission-trading scheme. They show that the total cost of the system is a jointly convex function by simply showing that every element of the Hessian is positive. Noticing this mistake, we analyse the same problem in this technical note. We first provide a closed-form solution when the production rate is given. In order to avoid a complete search over all possible production rates, we then develop an efficient continuous approximation algorithm. Computational experiment shows that the approximation algorithm is effective and efficient.     

A technical note on ‘Analysis of closed loop supply chain using genetic algorithm and particle swarm optimisation’

This study analyses the mixed-integer linear program (MILP) proposed by Kannan et al. [Kannan, G., Noorul Hag, A., and Devika, M., 2009. Analysis of closed loop supply chain using genetic algorithm and particle swarm optimization. International Journal of Production Research, 47 (5), 1175–1200] in their paper entitled ‘Analysis of closed loop supply chain using genetic algorithm and particle swarm optimisation’. Since we find inconsistencies in the model, we propose modifications to rectify the flaws. The revised model is presented and tested using a hypothetical problem.     

A note on ‘Pricing and ordering decisions in a supply chain with imperfect quality items and inspection under buyback of defective items’

Taleizadeh, Noori-daryan, and Tavakkoli-Moghaddam consider pricing and ordering decisions in a three-level supply chain with defective items and inspection processes in their paper published in 2015. They examine three scenarios for defective items at the manufacturer: disposal, rework and selling at a lower price. Unfortunately, this interesting and innovative paper suffers from some shortcomings that are addressed in our note.     

Vendor-managed inventory with consignment stock agreement for single vendor–single buyer under the emission-trading scheme

This paper presents a joint economic lot size (JELS) model for coordinated inventory replenishment decisions under the vendor-managed inventory (VMI) with consignment stock (CS) agreement and an emission-trading scheme. The paper assumes a single product that flows along a two-level supply chain system, with a single vendor and a single buyer. The total cost of the system is the performance measure, which is the sum of the vendor’s and the buyer’s total costs. The total cost includes the set-up and order costs, inventory holding costs, greenhouse gases (GHG) emissions tax and penalty costs. A mathematical model is proposed to determine: (1) the vendor’s production lot size quantity; (2) the number of shipments sent by the vendor to the buyer in a cycle; and (3) the production rate that minimises the total cost of the supply chain. Some numerical examples are carried out, as well as comparisons with the traditional JELS model for a classic two-level supply chain. Results show that the performance of the system is better when it is operated under a VMI with CS agreement, which is capable of reducing the traditional inventory holding costs and, for some values of given parameters, the GHG emissions tax and penalty costs.     

A note on ‘trade-off and compatibility between performance: definitions and empirical evidence’

This paper improves on a novel methodology advanced in order to assess deterministically (i.e., precisely) compromises and compatibilities between manufacturing capabilities in individual firms. We extend the original proposal to include more recent theoretical developments arguing that both trade-offs and compatibilities (e.g., cumulative capabilities) can be observed in a relationship between two or more competitive criteria. This means that as opposed to widely-accepted views, trade-offs and compatibilities can be complementary, and not necessarily mutually exclusive, when explaining relationships between various competitive criteria. As such, our improved methodology and rationale can assess the existence of both trade-offs and compatibilities between multiple capabilities utilising a single framework. Opportunities for novel research that uses our methodology are also offered.     

A note on ‘Single-machine scheduling for minimizing total cost with identical,asymmetrical earliness and tardiness penalties’

We point out a flaw present in a recent publication, and show how methodology can be modified to correct it.     

An analysis of manufacturers’ supply and demand uncertainty based on the dynamic customisation degree

Diverse demands regarding products are common; however, manufacturers usually cannot respond immediately to meet such changes upon demand, and thus, customer satisfaction tends to be reduced. Notebook computer manufacturers adopt a production mode of mass customisation; hence, a certain degree of dynamic customisation measurements, inherent in different supply chain models, allow manufacturers to evaluate costs and profits in advance. The application of the model, as proposed in this study, indicates that the most important factor of the customisation degree is product price. The dynamic customisation degree is adjusted based on monitoring indicators, which requires less total cost and produces greater accuracy in forecast results regarding the prediction model of customer demands. This study develops a dynamic customisation model for total product profits, inventory cost of semi-manufactured products, shortage costs and buffer inventory costs, which are affected by the degree of dynamic customisation of the products. It also analyses the supply and demand uncertainties of the Direct Shipment of the Manufactured Model, as well as the Door-to-Door Direct Shipment of the End User Model in the notebook computer industry, as the criteria with respect to a firm's customisation degree, costs, and profits in different supply chain mode operations.     

A distribution free newsvendor model with consignment policy and retailer’s royalty reduction

Reducing the system cost and achieving significant profit are the key factors for every successful business sector. A consignment contract under distribution-free approach may be a fruitful combination to achieve a profitable business. This model deals with a single-period newsvendor problem with a consignment policy. The consignment policy is an agreement between any two parties, named as the consignor and the consignee. Under Stackelberg approach, firms act as leader and follower. Both parties carry some parts of the holding cost instead of one. A new policy for paying the fixed fee to the consignee is introduced. This paper considers no specific probability distribution for customer’s demand except a known mean and standard deviation. An efficient approach is proposed to reduce the retailer’s cost and building a sustainable consignment contract. The solution of this model is obtained using distribution free approach. A comparison between the traditional supply chain policy and the consignment policy is established. The price-sensitivity on demand is analysed. Some numerical examples and graphical representations are given for both traditional and consignment policy. Result proves that consignment policy is dominating over the traditional policy and a significant reduction of retailer’s royalty is found.     

A note on ‘balancing printed circuit board assembly line systems’

In a recent paper of (Lapierre, S.D., Debargis, L. and Soumis, F., Balancing printed circuit board assembly line systems. Int. J. Prod. Res., 2000, 38, 3899–3911.), the authors considered the balancing of a PCB assembly line consisting of several pick-and-place machines. The authors claimed that, for the particular machine type they considered, the component placement time is independent of the placement sequence of the components and then concentrated on allocating component types to machines and configuring the feeders on each machine to balance the line. We show that, the placement time is actually dependent on the placement sequence and thus, it needs to be accounted for if a more accurate line balance is looked for.     

A note on ‘A bivariate optimal replacement policy for a repairable system’

An error appearing in equation (3) of Y.L. Zhang (J. Appl. Prob., 1994, 31, 1123–1127) has been pointed out by S.H. Sheu (Eur. J. Oper. Res., 1999, 112, 503–516) and the correct expressions (25)–(27) given accordingly on pp. 510–511. However, the derivation of the key expression (27), the long-run expected loss rate, was not presented. The purpose of this note is threefold. First, since a monotone process (e.g. an arithmetic, geometric, or arithmetic–geometric process) approach, as discussed by K.N.F. Leung (Eng. Optimiz., 2001, 33, 473–484), is considered to be relevant, realistic, and appropriate to the modelling of a deteriorating system maintenance problem, it is worth explicitly developing this expression, which is of benefit to the subsequent studies. Secondly, equation (3) in Zhang (1994) Zhang, Y. L. 1994. A bivariate optimal replacement policy for a repairable system. J. Appl. Prob., 31: 1123–1127. [Crossref], [Web of Science ®] , [Google Scholar] is shown to be fundamentally correct and so it can be viewed as an alternative method of formulating similar bivariate cases. Thirdly, although equations (4) and (5) in Zhang (1994) Zhang, Y. L. 1994. A bivariate optimal replacement policy for a repairable system. J. Appl. Prob., 31: 1123–1127. [Crossref], [Web of Science ®] , [Google Scholar] have been logically and correctly derived, both can be readily reduced to their simplest forms which are derived here.     

Analysis of retailers’ coalition stability for supply chain based on LCS and stable set

To attain the general form of stable coalition structure, this paper addressed the problem of retailers’ coalition stability in a two-stage supply chain consisting of one supplier and multiple retailers. A profit gain function was established via introducing market gain coefficient and coalition cost coefficient for different coalition structures. Based on the function, the profit of each retailer in all kinds of coalition structures was analysed, and the general feature of a stable coalition structure was attained by the largest consistent set method and the stable set method. Furthermore, some insights were obtained. For example, stable coalition structures are equidistributed or approximate equidistributed; with supplier’s cost increasing, the size of the retailers’ coalition increases. Finally, the above conclusions are verified by numerical simulation. The results of this paper provide a reference for retailers’ coalition in a supply chain, such as automobile or Information Technology supply chain.     

A note on ‘The exponentiated power Lomax distribution and its applications'

Abd El-Monsef, Sweilam and Sabry [Quality and Reliability Engineering International, 2020, doi: 10.1002/qre.2780] proposed a four-parameter exponentiated power Lomax distribution, derived its properties and illustrated three data applications. In this note, we show that several properties expressed in terms of infinite sums can be simplified to a known special function. We also show that certain one-parameter distributions can provide better fits to at least two of the data sets considered.     

A note on ‘Economic manufacturing quantity in a just-in-time delivery system’

This comment is made on a paper by Golhar and Sarker who showed that it is economically advantageous for a supplier to participate in the just-in-time delivery system. Although the general conclusions are correct, one of the conditions under which the results are obtained is not necessary. Also, the optimal production quantity is not independent of delivery quantity though their interdependency is in a rather indirect manner.     

A note on “Modelling an industrial strategy for inventory management in supply chains: the ‘Consignment Stock’ case”

Braglia and Zavanella [2003, Modeling an industrial strategy for inventory management in supply chains: the ‘consignment stock’ care, International Journal of Production Research, 41 (16), 3793–3808] proposed an analytic formulation of consignment stock (CS) policy and made a comparison with Hill [1999, The optimal production and shipment policy for a single-vendor, single-buyer integrated production-inventory problem. International Journal of Production Research, 37 (11), 2463–2473] model. Through dividing per unit holding cost into a financial and a storage one the present note extends their conclusion and shows whether the CS model offers lower costs depends on the comparative result of buyer's and vendor's storage costs.     

Towards optimal configuration of a manufacturer’s supply network with demand flexibility

Demand flexibility exhibits the degree to which customers are often willing to compromise on product features or performance levels for budgetary (reflected in price) or schedule (reflected in delivery) reasons. It is essential for a manufacturer to map demand flexibility into the supply side and investigate its impact on supply network configuration to maximise its total profit. This paper is among the first contributions that seek to address the challenge of optimal configuration of a manufacturer’s supply network that consists of raw material suppliers and contract manufacturers, considering demand flexibility and commonality among different product families. A new mixed integer programming model is developed to describe the characteristics of this problem. The objective was to maximise the manufacturer’s total profit subject to various operating constraints of the supply chain. In view of the complexity and non-deterministic polynomial-time (NP)-hard nature of the problem, a hybrid constraint programming and simulated annealing algorithm is proposed to solve the problem optimally. Extensive numerical studies are conducted to validate the effectiveness of the proposed model and the hybrid algorithm.     

A note on the paper ‘Demonstrating Johnson’s algorithm via resource constrained scheduling’

In this paper, we demonstrate that the relation between two jobs defined by min{a_i, b_j} ≤ min{b_i, a_j}, used in Johnson’s theorem, is not transitive. However, both the theorem and Johnson’s algorithm are correct.     

A note on ‘A multigoal heuristic for facilities desiǵn problems: MUGHAL’

We compare the performance of a set of rectangular layout heuristics on the basis of their packing densities and time performance, with a view to increase their applicability in manufacturing situations. Among the techniques is a class of heuristics introduced by the authors in an earlier work (Israni And Sanders, 1982). The experimental comparison is made over two attributes defined for the bill of materials; the area and the aspect ratio distributions of the pieces. In addition, some of the heuristics considered permit limited human intervention. Our study shows that the two attributes play a significant part in determining the performance of a heuristic. Length-sorted heuristics are found to perform differently as a class from height-sorted heuristics. The study shows that human intervention, even in limited amounts, usually improves the quality of a solution substantially. The heuristics' worst case time complexities are presented. For certain specific regions of the attributes, the best heuristic has been identified.