Discrete Lot Research Articles

Thermal Energy Storage with PCMs in Shell-and-Tube Units: A Review

The paper presents a survey of the experimental and numerical studies of shell-and-tube systems in which phase change material (PCM) is used. Due to the multitude of design solutions for shell-and-tube systems, the emphasis is placed on double-tube (DT), triplex-tube (TT), and multi-tube (MT) units. Additionally, only single-pass systems are considered. Particular attention is paid to the method of heat transfer intensification. The analysis of the research results begins with the classification of each of the three mentioned systems. The systems are divided according to the angle of inclination, the method of heat transfer enhancement (HTE), the flow direction of heat transfer fluid (HTF), and the arrangement of tubes in the bundle. Moreover, the simplified schemes of the particular research cases are proposed. Then, the works on each of the mentioned systems, i.e., DT, TT, and MT, are discussed chronologically. Finally, in the corresponding tables, details of the discussed cases are presented, such as geometric dimensions, and the type of PCM or HTF used. A novelty in the present work is the precise classification of PCM TESUs as DT, TTH, and MTH. In the literature, there is a lot of discretion in this regard. Second, the methods of heat transfer intensification in the presented PCM TESUs are listed and discussed. Third, unified schemes of design solutions for the discussed PCM TESUs are proposed. The review shows that development directions for shell-and-tube TESUs include systems with high conductivity fins of different shapes, heights, and spacing, several PCMs, and modified shells.

Experiences of Birth during COVID-19 Pandemic in Italy and Spain: A Thematic Analysis.

Becoming parents during the pandemic of coronavirus disease 2019 (COVID-19) has been a challenge. The purpose of this study was to describe the impact of the pandemic on new and expectant parents in both Italy and Spain. A descriptive qualitative study was carried out by collecting social media posts written by parents between March 2020 and April 2021. The posts were inserted in a data collection form and assessed separately by two authors. The coding was performed manually using the long table analysis method and a thematic analysis was performed. Three main themes were identified: (1) care; (2) overcoming difficulties and problem-solving strategies; and (3) legislation and anti-COVID-19 measures. The main issues for parents were the limited access of partners to antenatal care services and mother–newborn separation. Due to restrictive measures, many parents adopted different coping skills. Some hospitals were able to maintain high standards of care; however, a lot of discretion in legislation and the application of anti-COVID-19 measures in healthcare services was perceived by parents. The COVID-19 pandemic has heavily affected the way parents experienced pregnancy and birth. Becoming parents during the pandemic has exacerbated some fears that usually characterize this event, but it has also triggered new ones, especially in the first months.

Introduction: Democratizing Global Justice

Global governance ought to uphold global justice, a purpose that various institutions and instruments of global governance acknowledge more or less explicitly. Yet, to be effectively implemented, ethical principles of justice must first be “translated” into concrete policy. This formative and interpretive exercise—of determining what justice means and practically requires—leaves a lot of discretion to those making the interpretations, thereby raising important ethical dilemmas.

“fraude da locadora” e suas implicações no direito penal

Este trabalho apresenta uma análise sobre a prática criminosa conhecida popularmente como “fraude da locadora”, ela consiste em um cliente alugar um carro de locadoras de veículos, para, a princípio, o utilizar e logo após tal veículo é dado como roubado, sendo comunicado tanto a locadora quanto a autoridade policial e não há devolução do bem. No entanto, o carro é utilizado para outros fins não legais. Assim, há dificuldades de caracterizar-se o crime, pois há muitas similaridades nos delitos de furto mediante fraude, estelionato e apropriação indébita. Foi utilizado a pesquisa bibliográfica e o estudo de julgados para a diferenciação, após análise mais aprofundada vê-se que o crime de furto mediante fraude é menos confundido. Nos outros dois crimes, há ainda muita discricionariedade do julgador. Conclui-se que tal discussão vem para facilitar o melhor direcionamento do crime imputado ao réu.

Dynamic programming algorithms and Lagrangian lower bounds for a discrete lot streaming problem in a two-machine flow shop

In this paper, we propose exact and heuristic solution approaches based on dynamic programming for an open lot streaming problem. We also present the first application of Lagrangian relaxation to compute strong lower bounds to such a problem. The application concerns the minimization of the total flow time for the discrete version of a single-job lot streaming problem from the literature in a two-machine flow shop with attached setup times. Computational results on benchmark instances illustrate the effectiveness of the proposed approaches and give evidence of the strength of the Lagrangian relaxation lower bounds.

The Tradeoff between Discrete Pricing and Discrete Quantities: Evidence from U.S.-listed Firms

Economists usually assume that price and quantity are continuous variables, while most market designs, in reality, impose discrete tick and lot sizes. We study a firm’s trade-off between these two discretenesses in U.S. stock exchanges, which mandate a one-cent minimum tick size and a 100-share minimum lot size. A uniform tick size favors high prices because the bid–ask spread cannot be lower than one cent. A uniform lot size favors low prices because low prices reduce adverse selection costs for market makers when they have to display at least 100 shares. We predict that a firm achieves its optimal price when its bid–ask spread is two ticks wide, when the marginal contribution from discrete prices equals that from discrete lots. Empirically, we find that stock splits improve liquidity when they move the bid–ask spread towards two ticks; otherwise, they reduce liquidity. Liquidity improvements contribute 95 bps to the average total return on a split announcement of 272 bps. Optimal pricing can increase the median U.S. stock value by 69 bps and total U.S. market capitalization by $54.9 billion.

An algorithm for general infinite horizon lot sizing with deterministic demand

We present an algorithm for solving an infinite horizon discrete time lot sizing problem with deterministic non-stationary demand and discounting of future cost. Besides non-negativity and finite supremum over infinite horizon, no restrictions are placed on single period demands. (In particular, they need not follow any cyclical pattern). Variable procurement cost, fixed ordering cost, and holding cost can be different in different periods. The algorithm uses forward induction and its essence lies in the use of critical periods. Period j following t is the critical period of t if satisfying demands in any subset of the set of periods between t and j, including j and excluding t, from an order in t is not more expensive than satisfying it from an order in a later period and j is the last period with this property. When deciding whether to place an order in period t, all demands from t to its critical period are taken into account.

Freedom of Expression: what lessons should we learn from US experience?

Abstract Freedom of Expression is becoming a theme of growing importance and visibility in Brazil. Newspapers report daily legal suits against “hate speech” concerning race and religious discrimination. Many courts are also imposing high compensation damages that are challenging the “right to ridicule” in comedy shows and newspapers cartoons. The Brazilian public opinion in general tends to be sympathetic to more restrictive rules that may threaten freedom of expression in Brazil. There is nowadays in Brazil an unexpected agreement among the right wing, religious groups, and many human rights movements that support a European model of free speech. In many ways, the “Brazilian Model” based on balancing doctrine and a vague conceptualization of Human Dignity gives a lot of discretion for courts to decide the limits of freedom of expression. Court decisions based on balancing rhetoric is becoming dominant in Brazilian Constitutional court and usually try to avoid some epistemological issues concerning objectivity and moral justification. This article advocates that Brazilian interpretation of freedom expression has a lot to learn from the US model and doctrine. The US more strict and conceptual jurisprudence on this issue offers a powerful and democratic alternative to the balancing model and represents a rich conceptual analysis still unknown by Brazilian courts.

Integrated multiproduct batch production and truck shipment scheduling under different shipping policies

The classical economic lot-scheduling problem (ELSP) involves the batch sizing and scheduling of multiple products in a single facility under deterministic conditions over an infinite planning horizon. It is assumed that the products are delivered to customers at continuous rates. In today's supply chains, however, often employing complex delivery networks, the finished goods are usually transported in discrete lots to succeeding stages along the distribution process, in order to take advantage of economies of scale in transportation. In this paper, we formulate mathematical models that attempt to integrate the production lot scheduling problem with outbound shipment decisions. The optimization objective is to minimize the total relevant costs of a manufacturer, which distributes a set of products to multiple retailers. In making the production/distribution decisions, the common cycle approach is employed to solve the ELSP, for simplicity. Two different shipping scenarios, i.e. periodic full truckload (TL) peddling shipments and less than truckload (LTL) direct shipping, are integrated with and linked to the multiproduct batching decisions. We consider these two shipment policies for both coordinated and uncoordinated scenarios. The resulting mixed-integer, non-linear programming models (MINLPs) are solved by the BONMIN solver. Finally, a set of numerical examples illustrate and evaluate the relative efficacies of these policies.

Integrated Multiproduct Batch Production and Truck Shipment Scheduling under Different Shipping Policies

The classical economic lot-scheduling problem (ELSP) involves the batch sizing and scheduling of multiple products in a single facility under deterministic conditions over an infinite planning horizon. It is assumed that the products are delivered to customers at continuous rates. In today’s supply chains, however, often employing complex delivery networks, the finished goods are usually transported in discrete lots to succeeding stages along the distribution process, in order to take advantage of economies of scale in transportation. In this paper, we formulate mathematical models that attempt to integrate the production lot scheduling problem with outbound shipment decisions. The optimization objective is to minimize the total relevant costs of a manufacturer, which distributes a set of products to multiple retailers. In making the production/distribution decisions, the common cycle approach is employed to solve the ELSP, for simplicity. Two different shipping scenarios, i.e. periodic full truckload (TL) peddling shipments and less than truckload (LTL) direct shipping, are integrated with and linked to the multiproduct batching decisions. We consider these two shipment policies for both coordinated and uncoordinated scenarios. The resulting mixed-integer, non-linear programming models (MINLPs) are solved by the BONMIN solver. Finally, a set of numerical examples illustrate and evaluate the relative efficacies of these policies.

Virginia County Builds Consensus to Keep Mentally Ill Out of Jail

“Slow but steady” is the watchword as one county tackles the problem of too many people with mental illness in jail.

Synchronization, cross-docking, and decoupling in supply chain networks

At any distribution centre (DC), the decision of whether to synchronise inbound and outbound flows for cross-docking, or to decouple these flows by maintaining inventory, has a significant impact on supply chain performance. Key drivers of this decision, in turn, are the sizes of the discrete lots that comprise the flows. Thus, we formulate an original optimisation model that determines order lot-sizing decisions to minimise, for given constant arc flows, the sum of ordering cost and pipeline inventory cost on arcs and buffer inventory at DCs. The model employs an average throughput as a surrogate to estimate buffer inventory at facilities at which synchronisation is not economical and therefore serves to decouple inbound and outbound flows. Perfect lot-for-lot matching of shipments would impose very restrictive constraints on supply chain operations, but equality of average throughput indicates an innovative, relaxed mode of synchronisation. This mode is practicable for cross-docking by means of bulk-breaking or consolidation of shipments. A heuristic approach based on the Lagrangian relaxation and subgradient optimisation is developed for the non-linear mixed-general integer optimisation model, which is illustrated by numerical examples and tested using a benchmark data set.

Formulations for a problem of petroleum transportation

Oil tankers play a fundamental role in every offshore petroleum supply chain and due to its high price, it is essential to optimize its use. Since this optimization requires handling detailed operational aspects, complete optimization models are typically intractable. Thus, a usual approach is to solve a tactical level model prior to optimize the operational details. In this case, it is desirable that tactical models are as precise as possible to avoid too severe adjustments in the next optimization level. In this paper, we study tactical models for a crude oil transportation problem by tankers. We did our work on the top of a previous paper found in the literature. The previous model considers inventory capacities and discrete lot sizes to be transported, aiming to meet given demands over a finite time horizon. We compare several formulations for this model using 50 instances from the literature and proposing 25 new harder ones. A column generation-based heuristic is also proposed to find good feasible solutions with less computational burden than the heuristics of the commercial solver used.

A constrained multi-products EPQ inventory model with discrete delivery order and lot size

This paper proposes an alternative heuristic algorithm for a multi-product Economic Production Quantity (EPQ) vendor–buyer integrated model with Just in Time (JIT) philosophy and a budget constraint. This type of problem is usually solved by a Mixed Integer Non Linear Problem (MINLP), which is complex and computationally expensive. The proposed heuristic algorithm involves less computation and therefore it is less expensive than the previously published algorithms. Furthermore, the heuristic algorithm is simpler as it derives the integer values for all discrete variables in a straightforward manner. Through empirical experimentation, it is demonstrated that the heuristic algorithm provides solutions closer to the lower bound in a very short time.

Discrete lot sizing and scheduling problem under batch processing constraints in the semiconductor manufacturing

Highly advanced technology products are manufactured on the series of equipment having various characteristics and requirements. The deposition process of organic light emitting diode, for example, is performed in chambers for a long manufacturing time, while various product devices belonging to the same family can be processed in sequence before the preventive maintenance schedule or the refill of chemical gas required. The deposition process plays as a bottleneck, and its productivity of the schedule is critical to the upstream low-temperature poly silicon process and the downstream encapsulation and module processes as well. The batch family scheduling problem is formulated using the mixed-integer programming (MIP) in consideration of the family setups, lot sizing, supplementary mask tools requirements, and material exhaustion requirements. It is shown that the planning and scheduling decisions can be made simultaneously in an integrated model, and that it can be implemented in the actual manufacturing line. Through the optimized model analysis, the capacity can be enhanced by 20∼30 % without losing the throughput and demand satisfaction as well.

Corruption, Bureaucratic Failure and Social Policy Priorities

This article argues that bureaucratic capacity – the competence and reliability of the national bureaucracy – matters to the allocation of public spending among welfare state programmes since it is difficult for governments to justify high levels of spending on programmes that require bureaucrats to make case-by-case decisions, on a discretionary basis, if the bureaucracy is incompetent, corrupt or both. We expect bureaucratic capacity to have a positive effect on programmes that involve bureaucratic discretion, but weak or no effects on programmes that are more straightforward to implement. In order to test these hypotheses, we analyse public spending on active labour market programmes (which involve a lot of discretion) and parental leave benefits (which involve less discretion). Relying on data for twenty advanced democracies from the mid-1980s to the mid-2000s, we find that high bureaucratic capacity does have a positive effect on active labour market policy spending, but not on parental leave benefits.

Performance evaluation of proposed Differential Evolution and Particle Swarm Optimization algorithms for scheduling m-machine flow shops with lot streaming

We consider n-job, m-machine lot streaming problem in a flow shop with equal size sub lots where the objective is to minimize the makespan and total flow time. Lot streaming (Lot sizing) is a technique that splits a production lot consisting of identical items into sub lots to improve the performance of a multi stage production system by over lapping the sub lots on successive machines. There is a scope for efficient algorithms for scheduling problems in m-machine flow shop with lot streaming. In recent years, much attention is given to heuristics and search techniques. To solve this problem, we propose a Differential Evolution Algorithm (DEA) and Particle Swarm Optimization (PSO) to evolve best sequence for makespan/total flow time criterion for m-machine flow shop involved with lot streaming and set up time. In this research, we propose the DEA and PSO algorithms for discrete lot streaming with equal sub lots. The proposed methods are tested and the performances were evaluated. The computational results show that the proposed algorithms are very competitive for the lot streaming flow shop scheduling problem.

Animals in the administrative zoo: organizational change and agency autonomy in Germany

Although Germany does not figure among the ‘forerunners’ of managerial reforms of the public sector, it has a long tradition of agencies and non-departmental bodies at the federal level. Over time, the federal administration has developed into a highly differentiated ‘administrative zoo’ with a large number of species, questioning the image of a well-ordered German bureaucracy. The article addresses organizational changes among non-ministerial agencies during the past 20 years and ministry—agency relations, drawing on data from a comprehensive survey of the federal administration. The structural changes we observe are neither comprehensive nor planned; they are much more evolutionary than revolutionary, driven by sectoral policies and not by any overall agency policy, supported more by regulatory than by managerial reforms, and most of the changes are horizontal mergers or successions of existing organizations, while we find almost no evidence for hiving-off from ministries to agencies. At the same time, federal agencies report a lot of bureaucratic discretion, whereas they perceive substantial levels of ‘red tape’ due to administrative regulations. We also find that traditional, hierarchical modes of ministerial oversight are still dominating; only few agencies have performance agreements with measurable goals.Points for practitionersThe article will be of interest to practitioners concerned about the nature and direction of organizational change within government, especially about processes of horizontal and vertical differentiation and steering. It demonstrates that even in a highly developed and classical bureaucratic administrative system such as Germany there is and has for a long time been a large variety of governmental agencies that enjoy a considerable amount of autonomy. At the same time there is continuous change and adaptation to new circumstances, even though all this has very little to do with international modernization trends such as New Public Management or comprehensive agencification.

An integrated production–distribution model for a deteriorating inventory item

We develop an integrated production–distribution model for a deteriorating item in a two-echelon supply chain. The supplier’s production batch size is restricted to an integer multiple of the discrete delivery lot quantity to the buyer. Exact cost functions for the supplier, the buyer and the entire supply chain are developed. These lead to the determination of individual optimal policies, as well as the optimal policy for the overall, integrated supply chain. We outline a procedure for determining the optimal supply chain decisions with the objective of minimizing the total system cost. Our approach is illustrated through a numerical example.

Determining the adaptive decision zone of discrete lot sizing model with changes of total cost

The Economic Order Quantity (EOQ) zone is beneficial for giving some latitude in picking the lot sizes in a continuous time inventory problem, but it is not suitable for a discrete time inventory problem, the discrete lot sizing (DLS) problem. In this paper, a novel enumeration method is proposed and coded as a user-friendly computerized scheduling system to “visualize” the complex DLS problems by projecting the entire feasible solutions on a two dimension space, where setup frequency and total cost are placed on the horizontal and the vertical axis respectively. First, the zone around the optimal solution in the DLS problem is demonstrated always smooth and this phenomenon is defined as DLS zone in which giving a small penalty cost from the optimal solution brings several alternative solutions for picking the lot sizes. Second, even if the penalty costs are changed, the computerized scheduling system is able to determine the adaptive decision zone and find the included alternative solutions. The flexibility in picking the lot sizes for discrete time inventory problems is significantly enhanced since decision makers are enabled to choose a preferable solution from the DLS zone.