Rework Process Research Articles

A Fuzzy Inventory Model Considering Imperfect Quality Items with Receiving Reparative Batch and Order

This paper presents an inventory model for imperfect quality items with receiving a reparative batch and order overlapping in a fuzzy environment by employing fuzzy triangular numbers. It is assumed that the imperfect items identified by Screening are divided into either scrap or reworkable items. The reworkable items are kept in store until the next items are received. Afterward, the items are returned to the supplier to be reworked. Also, a discount on the purchasing cost is employed as an offer of cooperation from a supplier to a buyer to compensate for all additional holding costs incurred to the buyer. The rework process is error-free. An overlapping order scheme is employed so that the vendor is allowed to use the previous shipment to meet the demand by the inspection period. In the fuzzy model, the graded mean integration method is taken to defuzzify the model and determine its approximation of a profit function and optimal policy. In doing so, numerical examples are rendered to represent the model behavior, and, eventually, the sensitivity analysis is presented.

Mixed diatom floras in sedimentary deposits from the 2016 Kaikōura Tsunami at Little Pigeon Bay, Aotearoa-New Zealand

Abstract This study records the diatom flora from sedimentary deposits found within a coastal cottage, following the November 2016 Kaikōura earthquake and tsunami at Little Pigeon Bay, Banks Peninsula, Aotearoa-New Zealand. Unlike previous studies of diatoms from modern tsunami deposits, the sediments in this study were isolated from any previous (and subsequent) reworking of sediments. The diatom flora (n = 117 taxa) are dominated by benthic and planktonic lifeforms with preferences for marine (28%), brackish-marine (25%), fresh-brackish (19%) and fresh-water (17%) conditions. The higher abundances of benthic marine and brackish-marine diatoms are attributed to direct in-washing and reworking of open ocean-water with sandy marine sediments from the sub-tidal and inter-tidal zones. Comparatively high percentage counts of benthic fresh-brackish and freshwater diatom taxa also indicate significant freshwater sources and sediments from the stream and land adjacent to the cottage. Fractured and damaged diatom frustules within the flora, including broken sponge spicules, emphasise dynamic processes of reworking, abrasion and erosion during incoming and outgoing tsunami waves. Likelihood-based ordination analysis of the diatom flora indicates statistical differences between the flora in the back area of the cottage and the centre and front areas which we attribute primarily to the influence of different waves that inundated the cottage from the seaward and landward directions. Such a record affirms a highly mixed diatom flora from multiple sources and habitats. It also offers a first modern analogue from Aotearoa-New Zealand to assist future assessments of multi-proxy-based records of past tsunami events preserved in the geological record.

3D face modeling and rapid casting based on reverse design

This paper first obtains human body data based on a 3D scanner, combines with Geomagic Studio to obtain a 3D model; and explores three 3D printing technologies for rapid prototyping of the model. The 3D prototype is turned out of the wax mold using the silicone rubber reworking process, and finally the melting is used. Mold casting process to complete portrait casting. Practice has proved that this method realizes the entire workflow of 3D face data acquisition, rapid prototyping, and rapid casting, and has high application value and market prospects in the production of 3D portrait artwork.

The Collective Influence of Component Commonality, Adjustable-Rate, Postponement, and Rework on Multi-Item Manufacturing Decision

The present study explores the collective influence of component commonality, adjustable-rate, postponement, and rework on the multi-item manufacturing decision. In contemporary markets, customer demand trends point to fast-response, high-quality, and diversified merchandise. Hence, to meet customer expectations, modern manufacturers must plan their multiproduct fabrication schedule in the most efficient and cost-saving way, especially when product commonality exists in a series of end products. To respond to the above viewpoints, we propose a two-stage multiproduct manufacturing scheme, featuring an adjustable fabrication rate in stage one for all needed common parts, and manufacturing diversified finished goods in stage two. The rework processes are used in both stages to repair the inevitable, nonconforming items and ensure the desired product quality. We derive the cost-minimized rotation cycle decision through modeling, formulation, cost analysis, and differential calculus. Using a numerical illustration, we reveal the collective and individual influence of adjustable-rate, rework, and postponement strategies on diverse critical system performances (such as uptime of the common part and/or end products, utilization, individual cost factor, and total system cost). Our decision-support model offers in-depth managerial insights for manufacturing and operations planning in a wide variety of contemporary industries, such as household merchandise, clothing, and automotive.

Architectural evolution of a mixed-influenced deltaic succession: Lower-to-Middle Ordovician Armorican Quartzite in the southwest Central Iberian Zone, Penha Garcia Formation (Portugal)

Facies stacking patterns and stratigraphic relationships resulting from the interaction of fluvial and wave processes, along with the paleoshoreline orientation and key surfaces, are essential to understand the temporal changes in the rate of change of accommodation space (A) versus sediment supply rate (S). High-frequency sea-level fluctuations in deltaic systems are controlled by changing accommodation and accumulation, which are explained mainly by autocyclic or allocyclic mechanisms. In deltaic systems, changes in the A/S ratio can be showed by significant variations of the internal facies architecture and the external morphology of the delta complex. These criteria have been used to investigate the relationship between autocyclic and allocyclic processes on the architectural evolution of a mixed river- and wave-influenced asymmetrical delta during the Lower-to-Middle Ordovician in the southwest Central Iberian Zone, in Portugal. Relying on the sedimentary and ichnological characteristics, the herein defined Penha Garcia Formation is classified into two main groups of facies associations, which are interpreted as deposited in a mixed asymmetrical delta with a trend of along-strike variations between wave-dominated strandplain (updrift) and river-dominated deltaic settings (downdrift). The vertical stacking arrangements of parasequences led to the identification of five depositional phases (I to V). Detailed analysis of geometry and internal architecture of the depositional phases along depositional strike shows a highly variable number of shallowing-upward cycles and facies thicknesses/heterogeneity on the updrift and downdrift side due to changes in rates of accumulation and hydrodynamic processes. The stratigraphic architectural style of the depositional phases I to V, and the trend of the total regressive ascending shoreline trajectory, are evidences that the deposition of the Penha Garcia Formation likely took place under an increasing rate of accommodation due to long-term relative sea-level rise (allocyclic), and high subsidence rates coupled with an increase in sediment supply, which could have been locally amplified by compaction of the prodelta-related muddy beds (autocyclic). This study suggests that in evaluating the autocyclic mechanisms on deltaic processes in short-time scales, there is a remarkable difference in terms of its impact on the internal variability of the depositional phases, both in the updrift and downdrift regions of mixed-influenced asymmetrical deltas. The most important reasons for the different effects of autocyclic mechanisms can be related to facies-dependent differential compaction or local changes in subsidence pattern, differences in the proximity to the distributary channel system, and differences in the influence of intrinsic processes of storm and wave reworking (wave-sweeping mechanisms).

Crustal growth and reworking of Archean crust within the Rhyacian domains of the southeastern Guiana Shield, Brazil: Evidence from zircon U–Pb–Hf and whole-rock Sm–Nd geochronology

The southeastern Guiana Shield, northern Amazonian Craton, is part of a Paleoproterozoic orogenic belt that was built up during the Transamazonian orogenic cycle (2.26–1.95 Ga). This cycle includes large segments of Rhyacian juvenile crust and some reworked Archean terranes. The geology in this region consists mainly of Paleoproterozoic granulitic-migmatitic-gneissic complexes, deformed and metamorphosed metavolcanic and metasedimentary rocks, and granitoids (granitic and TTG magmatism). Three tectonic domains are distinguished in the Brazilian territory of the southeastern Guiana Shield. They are known as the Amapá Block, Lourenço Domain, and Carecuru Domain. The Amapá Block is a Meso–Neoarchean continental block that was intensely reworked during the Transamazonian orogeny. The other two domains represent Rhyacian landmasses, the evolution of which involved several stages of subduction of oceanic lithosphere in magmatic arc environments. There are also relics of reworked Archean continental crust, the formation of which was followed by a collisional stage of tectonic accretion of the magmatic arcs. Whole-rock Sm–Nd and U–Pb zircon geochronology have confirmed the juvenile character of much of this Transamazonian orogenic belt. However, for the Lourenço and Carecuru domains, Nd isotopic signatures indicate the participation of Meso–Neoarchean crustal material in the sources of the magmatic rocks. Combined zircon U–Pb and Lu–Hf isotopic analyses by LA-ICP-MS were performed on eleven Rhyacian granitoids and orthogneisses from the Lourenço and Carecuru domains. The aim was to verify the extension of the influence of the Archean continental crust in the adjacent Paleoproterozoic domains. The main magmatic episodes were identified in the Lourenço Domain (~2.17–2.18, 2.14 and 2.12–2.09 Ga) and Carecuru Domain (2.14 Ga) by U–Pb zircon geochronology. The Lu–Hf isotope data point to the predominance of crustal reworking processes (ƐHf(2.2–2.1 Ga) < 0; 67% of zircon crystals) during the formation of Lourenço and Carecuru domains. Hf model ages were found to be mostly Archean (98.4%), even for zircon grains that have positive ƐHf(2.2–2.1 Ga) values. For the terrane at the border of the Lourenço and Carecuru domains with the Amapá Block, assimilation of Archean crust of different ages and proportions in a magmatic arc environment accounts for the Hf–Nd isotopic signatures and Hf model ages of Rhyacian magmatism. In the northwestern part of the Lourenço Domain, more than 100 km north of the Amapá Block, the Hf–Nd isotopic signatures and Hf model ages indicate the participation of Archean crustal material, either as continental fragments and/or through incorporation of continental sediments in island arc environments, similar to what has been recorded for some Birimian terranes of the West African Craton in Ghana.

Data-Enabled Modeling and Analysis of Multistage Manufacturing Systems with Quality Rework Loops

In a multistage serial production line, multiple inspection stations and repair processes are typically involved to ensure high product quality. Quality rework is the activity to repair or repeat the work on the defect parts during manufacturing processes. The rework process after each inspection can add cost and cycle time to the normal process and impose negative impact on the throughput. This paper studies real-time performance of multistage serial manufacturing systems with quality rework loops and machine random failures. A production line with multiple quality rework loops is first unify by segmenting it into a set of serially connected quality rework loops. An event-based data-enabled mathematical model is developed to evaluate real-time production rate of each machine for such a system. In addition, the system properties are analyzed and permanent production loss due to quality rework loops and random machine failures are identified respectively. The permanent production loss attribution to each disruption event and machine can be used as real-time performance indicators to diagnose production system inefficiency. The mathematical model and system performance identification methodology are studied analytically and validated through numerical case studies.

효과적인 3D애니메이션 제작을 위한 리워크 프로세스 연구 - 프리비즈 레이아웃 공정 사례를 중심으로 -

애니메이션은 움직이지 않는 것을 움직이게 하는 기법이다. 이는 창의적인 생각들을 가시적인 영상으로 만드는 것에 가장 적합하지만 모든 프레임을 만들어야 하는 과정 때문에 많은 인력이 정해진 순서대로 작업해야만 하는 어려움이 있었다. 오늘날에는 하드웨어의 발전으로 실시간 3D애니메이션을 구현할 수 있게 되었고 애니메이션 작업 중에도 수정이 가능하다. 하지만 이로 인해 기획을 마쳤음에도 제작 중 다시 기획단계의 수정을 요구하는 경우가 종종 발생한다. 퀄러티를 높이기 위한 수정은 콘텐츠 경쟁력을 위해 불가피한 과정이지만 해당 공정 이전단계의 수정은 리스크를 발생시키므로 효과적인 수정 방안에 대한 논의가 필요한 시점이다.BR 리워크 프로세스는 3D 각 단계에서 발생하는 수정사항을 효율적으로 통제하는 효과적 시스템으로서 연구자가 속한 실무에서 그 동안의 여러 경험과 논의가운데 시행하고 능률 향상을 경험한 검증된 제작공정이다. 이는 본격적인 제작 이전의 기획단계에서 레이아웃 점검하고 변경하여 최대한의 기획 의도를 반영한 프리비즈를 만드는 과정으로 기획자는 카메라 구도, 캐릭터 액션, 사물배치, 편집 호흡 등 상상한 것들을 간단한 레이아웃 영상으로 만들어 확인, 수정 보완 하면서 최종 프리비즈를 확정한다. 리워크 프로세스로 만들어진 프리비즈 레이아웃은 비교적 수정이 용이한 3D 제작공정의 특성을 기획단계에서 최대한 이용하고 3D아티스트의 즉흥적인 수정을 막는 합리적이고 효율적인 커뮤니케이션 수단이라 할 수 있다.BR 프리비즈 레이아웃을 통한 구체적 연출 수정사례로는 카메라 연출 의도 변화, 캐릭터 연기 의도 변화, 사건 스토리의 구체화를 소개하였고 화면미장센 구성, 캐릭터와 배경의 관계, 캐릭터와 프랍의 관계, FX 및 시뮬레이션 가이드 제작 작업등 스테이징 작업을 통한 수정 사례도 소개하였다.BR 마지막으로 연구자는 국내 자체제작 콘텐츠는 모두 아동용 애니메이션이며 대부분 3D로 제작하므로 대학에서 3D애니메이션 교육은 매우 중요하다고 생각한다. 이에 본 연구에서 소개하는 실무 제작공정과 리워크 프로세스 사례들이 교육현장에서 학생들을 지도하는데 참고자료가 될 수 있기를 기대한다.

Sustainable inventory policy for an imperfect production system with energy usage and volume agility

A sustainable production inventory model that addresses some of the pragmatic scenarios of the production process is developed. The production process is considered imperfect which results in the production of some imperfect quality items with known distribution. The imperfect products are managed through an efficient rework process that makes the items suitable to be vended at their original markup price only. The agile nature of the manufacturing process is considered. And, the energy usage and carbon emission in the production process is also considered. Undoubtedly, the fundamental nature of demand is sensitive to price. Thus, the model incorporates the demand to be price-contingent. The objective is to maximize the overall inventory turnover by conjointly optimizing the selling price, production rate, and production time. A numerical example is included to validate the model. Further, the sensitivity analysis unfolds valuable managerial insights for decision-makers. Findings suggest that the model with the insertion of volume agility effect performs better when compared with the one without the volume agility.

General multi-state rework network and reliability algorithm

A rework network is a common manufacturing system, in which flows (products) are processed in a sequence of workstations (nodes), which often results in defective products. To improve the productivity and utility of the system, the rework network allows some of the defective products to go back to the “as normal” condition after the rework process. Since 2017 [1, 2], the traditional study proposed an algorithm to correct more than 21 archive publications regarding the rework network reliability problem, which is an important real-life problem. In addition to traditional research, we provide an accurate general model based on the novel state distribution with a smaller number of limitations. Furthermore, we propose an algorithm to calculate the reliability of the multi-state rework networks using the proposed novel state distributions.

Proterozoic tectonic evolution of the Tarim Craton: New insights from detrital zircon U-Pb and Lu-Hf isotopes of metasediments in the Kuruktag area

The Proterozoic is the longest Eon in geological history and witnessed the assemblies and breakups of the Columbia and Rodinia supercontinents. The Tarim Craton has been proposed to be a building block of these supercontinents. However, its tectonic evolution during late Paleoproterozoic to earliest Neoproterozoic (ca. 1.8–0.8 Ga) has been poorly understood, due to the paucity of geological record. In this paper, we present U-Pb and Lu-Hf isotopic data for detrital zircons from the metasediments of the early Neoproterozoic Paergangtag Group and the Paleoproterozoic Xinditag Group in the Kuruktag area, northern Tarim Craton.Although formed approximately 1 billion years later, the Paergangtag Group contains detrital zircons almost identical to those inthe Xinditag Group. LA-ICP-MS U-Pb dating yields a ca. 2.0 Ga age peak, as well as a group of older zircons of ca. 2.5 Ga in six samples from these two groups. Lu-Hf data show that the ca. 2.0 Ga zircons have variableεHf(t) values (−28.1 to 0.1), indicating the detritus were mostly derived from reworked continental crusts. The older zircons around 2.5 Ga have both negative and positiveεHf(t) values (−28.5 to 9.5), indicating a prolonged and complicated crustal growth and reworking process in the source area. It is inferred that the zircons in these samples were likely derived from southeastern Tarim Craton, where a ca. 2.0 Ga orogenic event has been documented.The fact that the Neoproterozoic Paergangtag Group contains only Paleoproterozoic and older zircons suggests that the Tarim Craton was not involved in the Grenville Orogeny, which developed between the colliding continents in the interior of the Rodinia Supercontinent. In contrast, the Tarim Craton was probably on the periphery of the Rodinia Supercontinent and was involved in the peripheral subduction zone of the supercontinent shortly after the deposition of the Paergangtag Group. Our new data imply that the Tarim Craton might have been a tectonically stable continent for nearly 1 billion years from ca. 1.8 to 0.9 Ga.

Solution of an EPQ model for imperfect production process under game and neutrosophic fuzzy approach

This article deals with an Economic Production Quantity (EPQ) deteriorating inventory model for non-random uncertain environment. It includes rework process, screening of imperfect items and partial backlogging. The items are partially serviceable, because at the time of production some items are found to be defective which cannot be recoverable or serviceable. At first, we develop a cost minimization problem under several assumptions related to imperfect items and rework process under certain linear constraints. We solve the crisp model (primal nonlinear problem) first, and then we convert this model into equivalent game problem taking the help of the theories related to strong and weak duality theorem. However, this game problem consists of the Lagrangian function that correspond a nonlinear objective function subject to some linear constraints. The main objective of the study is to develop a solution procedure of the problem associated to an imperfect process where all unit cost components might increase or decrease neutrosophically. Thus, according to the experiences gained by the decision maker (DM) we fuzzify all cost components as sub-neutrosophic offset. To defuzzify the model we have utilized the sine cuts of neutrosophic fuzzy numbers followed by a solution procedure developed in solving the matrix game exclusively. To validate the model, a numerical example is studied then we have compared the optimal results among the original problem, the equivalent game problem and the game problem under neutrosophic environment explicitly. Our findings reveal that under negative α-cuts the value of the objective function assumes lower and higher values. Finally, sensitivity analysis, graphical illustrations, conclusions and scope of future works have been discussed.

Petrography and Mapping of the Gwal Melange of Khanozai Region, Balochistan, Pakistan

Abstract The Gwal mélange is mapped on a large scale and is divided into the lithological units such as ultramafic, mafic, volcanic, volcanoclastic rocks, pelagic sediments and ophicarbonates. Petrographically, the mapped rocks are classified as harzburgite, dunite, wehrlite, serpentinite, gabbro, basalt, and andesite. These rocks are quite deformed and altered into the secondary minerals. Harzburgite is a layered mantle peridotite consists of olivine and orthopyroxene while dunite lacks the presence of any pyroxene. Serpentinite is the secondary product after peridotite is the product of post magmatic stages. The mesh structure is usually observed when olivine is completely altered to serpentine. The volcanic rocks are structurally sheeted and pillow type while the volcanoclastic rocks are essentially hyaloclastites associated with pelagic sediments. The Ophicarbonate is composed of serpentinite fragments and carbonate minerals, most probably calcite. Minor to trace amounts of opaque minerals are also present in association with major components. The gabbros may be a fragment of the main crustal rocks and have been formed in a magma chamber by fraction crystallization. The origin of ophicarbonate may be due to gas seeps originated by mantle or as the surficial process where ultramafic rocks and carbonates are mixed through processes of gravity, tectonic crushing and sedimentary reworking. The Gwal mélange may the southern extension of Bagh Complex found beneath the Muslim Bagh Ophiolite. The mantle peridotite of the mélange is much like that of the Khanozai peridotite and may represent its detached blocks. Volcanic and volcanoclastic rocks may be the representatives of the uppermost part of ophiolite crust which might have trimmed off from subducting slab and are, now, part of the Gwal accretionary wedge. The mélange may have tectonically emplacement over the Indian platform sediments along with overlying the ophiolite sheet during the Late Cretaceous.

A change from warm/humid to cold/dry climate conditions recorded in lower Barremian clay-dominated continental successions from the SE Iberian Chain (NE Spain)

A combined facies and clay mineralogy analysis of the continental succession recorded in the lower part of the Blesa Formation (early Barremian, Oliete subbasin, NE Spain) allowed us to specify the palaeoclimatic and palaeoenvironmental conditions under which this sedimentary record originated. Six outcrops including clays, clays/marls and dm-thick interbedded palustrine-lacustrine limestone levels were logged and sampled for X-ray diffraction and optical and electron microscopy analysis. The lower levels consist of red clays with abundant ferruginous pisoids (1–5 mm in size) and macropisoids (>5 mm), whereas the intermediate and upper levels are ochre and violet clays/marls with few or no pisoids. The pisoids normally consist of a nucleus and a cortex made up of several layers. Some pisoids have a fragment of a previous pisoid acting as a nucleus, indicating local re-working processes. Both the nucleus and the cortex are formed by hematite, goethite, variable contents of kaolinite, and minor proportions of ilmenite. Their texture and mineralogy show an in-situ growth. Interbedded limestone beds within the clay- and clay/marl-dominated levels are formed by micrite, microsparite and sparite. These limestones are cemented by kaolinite and they also have pisoids, indicating the occurrence of edaphic processes. The red clays have the lowest calcite content and the highest hematite, anatase, diaspore, goethite and kaolinite content. By contrast, the ochre and violet clays/marls have higher illite content. Smectite is only detected in the ochre clays/marls. This mineral association is characteristic of lateritic palaeosols, formed under warm and humid conditions. Kaolinite and smectite textures indicate that they are authigenic, whereas illite may be of detrital origin. The upward decrease in kaolinite, hematite, anatase, diaspore and goethite content, along with the increase in quartz content and the presence of smectite and illite, reflect a change from warm and humid conditions to drier and colder conditions during the early Barremian in the studied area.

Geology and geochemical constraints on the origin of the Mesoarchean granitoids from Carajás province, Amazonian craton

The Carajás province (CP) is the largest preserved Archean core of the Amazonian craton. In this paper we present a detailed work about the Tucumã area located in the northwestern portion of the Rio Maria domain of the CP, where more detailed studies had not yet been carried out. The new geological and geochemical data obtained allowed the identification of Mesoarchean granitoids of different natures that resemble typical late-Archean granitoids (TTG, leucogranites, sanukitoids and hybrid granites) identified in several cratons around the world. The most extensive unit in the Tucumã area is the Leucomonzogranitic batholith which is intrusive in a tonalite crust of TTG affinity, that exhibits an older N-S structural pattern commonly found in oldest rocks (greenstone belt sequence). The batholith is coeval with small granitoid intrusions that occur as lenses controlled by NE-SW and E-W direction anastomosed shear zones. Apart from the tonalite, these granitoids show affinity with the calc-alkaline series and are individualized in four units. The porphyritic granodiorite is a magnesium-rich unit that has moderate K2O/Na2O ratio and higher levels of Ba, K and Th, indicating similarities with the Transitional TTG suites (Yilgarn craton). Equigranular granodiorites are equivalent of sanukitoid suites; they show enrichment in Sr and compatible elements (Mg, Cr, and Ni) and depletion in HREE. Hybrid granitoids were identified as High-HFSE granites (medium- and high-Ba) that share some geochemical affinities with Closepet granite of the Dharwar craton. The Leucomonzogranite is enriched in LILE and exhibit negative Eu anomalies, which indicate crustal reworking processes. This granitoids are syntectonic bodies that underwent a progressive deformation processes that started before the magma crystallization was complete, under high temperatures (>500 °C) conditions compatible with those of the amphibolite facies. Two phases of magmatism are recorded in the RMD, which would be responsible for the formation of these granitoids. The first phase (2.98-2.92 Ga) is related to formation of a thick TTG crust from parcial melting of an oceanic plateau or a thickened mafic crust. The second magmatism phase (~2.87 Ga) initiated due to thermal events in a collisional setting, where both crustal rework processes and generation of juvenile magmatism occurred at the same time, resulting in the formation of heterogeneous plutons, at different crustal levels that were emplaced by mechanisms analogous to diapirs.

Texts and Readers in the Age of Marvell. Edited by Christopher D’Addario and Matthew C. Augustine. Manchester: Manchester University Press, 2018. Pp. xiv+255.

<i>Texts and Readers in the Age of Marvell</i>. Edited by Christopher D’Addario and Matthew C. Augustine. Manchester: Manchester University Press, 2018. Pp. xiv+255.

Integrated vendor–buyer strategies for imperfect production systems with maintenance and warranty policy

Collaboration has evolved as a key component of many modern supply chains, supporting the competitive advantages of companies in a range of operations from manufacturing to sales. With this viewpoint, the present paper develops an integrated inventory model in which manufacturing is carried out at the vendor’s end so as to fulfill demand at the buyer’s doorway. As the production process is presumed to be imperfect it shifts from an “in-control” state to “out-of-control” state at any random time and yields non-conforming items. The vendor uses regular preventive maintenance actions for the efficient operation of the production system and offers free minimal repair warranty on the products sold to the buyer. Along with preventive maintenance actions the vendor also uses the rework process and restoration process as effective steps towards minimizing the imperfections of the production system. The proposed model solves the non-linear cost minimization problem through a generalized reduced gradient method by using Lingo 15.0. The aim is to jointly optimize the order size, backorder size and the number of shipments in order to minimize the integrated cost of the vendor and the buyer. Numerical analysis and sensitivity analysis is performed on key parameters that render some important supervisory insights.

A Constrained Production System Involving Production Flexibility and Carbon Emissions

The proposed study presents an economic lot size and production rate model for a single vendor and a single buyer setup. This model involves greenhouse gas (GHG) emissions from industrial sources. The carbon emissions in this model are considered as two types: direct emissions and indirect emissions. The production rate affects carbon emissions generation in production, i.e., generally, higher production rates result in more emissions, which is governable in many real-life cases. The production rate also impacts the process reliability and quality. Faster production deteriorates the production system quickly, leading to machine failure and defective items. Such reliability and quality problems increase energy consumptions and supply chain (SC) costs. This paper formulates a vendor-buyer SC model that tackles these issues. It considers two decision-making policies: integrated or centralized as well as decentralized, where the aim is to obtain the optimal values of the decision variables that give the minimum total SC cost. It includes the costs of setup, holding inventory, carbon emissions, order processing, production, reworking, and inspection processes. The decision variables are the production rate, lead time, order quantity, the number of shipments, and the investments for setup cost reduction. In the later sections, this paper compares the numerical outcomes of the two centralized and decentralized policies. It also provides sensitivity analysis and useful insights on the economic and environmental execution of the SC.

A deterministic production inventory model with defective items, imperfect rework process and shortages backordered

The basic assumption of the conventional inventory models is that all items produced are of perfect quality. In practice, some defective items are produced due to process deterioration or other factors. This paper develops a mathematical model for an imperfect production inventory system. It is assumed that the defective items produced in the regular production process consist of scrap, imperfect quality and reworkable items. The rework process is accomplished immediately when the regular production process ends, and the rework process produces scrap, imperfect quality and as-good-as perfect items. A numerical example is provided to illustrate the developed model, and a sensitivity analysis is carried out. It was found that producing scrap and imperfect quality items through the reworking is crucial, since this assumption effects optimal policy. Managerial insights are also presented based on the numerical examples.

A two-level supply chain with price sensitive random demand, random yield, inspection, and rework process

A two-level supply chain with price sensitive random demand, random yield, inspection, and rework process