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Previous studies have acknowledged the role of Six Sigma in productivity improvement, but the implication of absorptive capacity (ACAP) has yet to be fully addressed. Accordingly, this paper investigates the mediating effect of AC...
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Previous studies have acknowledged the role of Six Sigma in productivity improvement, but the implication of absorptive capacity (ACAP) has yet to be fully addressed. Accordingly, this paper investigates the mediating effect of ACAP on the link between Six Sigma's critical success factors and productivity improvement. The hypothesised relationships were tested with data collected from quality managers in 167 manufacturing companies in Saudi Arabia. The result of PLS-SEM indicates that ACAP significantly mediates the influences of training and education, top management commitment and involvement, project selection and prioritisation and organisation resources on productivity improvement. However, the mediating effect of ACAP was not supported for the path between linking Six Sigma to business strategy and productivity improvement. Moreover, ACAP was significantly related to productivity improvement. The implications of our findings on the firm's productivity improvement and operation management literature were discussed, and the relevant suggestions were offered for future research.
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This paper addresses the problem of capacity estimation and improvement of a multi-stage, multi-product production line where workstations are subject to random failure and repair. The production line can process a variety of prod...
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This paper addresses the problem of capacity estimation and improvement of a multi-stage, multi-product production line where workstations are subject to random failure and repair. The production line can process a variety of products in a batch production environment. Products are processed according to a predefined sequence. A linear programming model is used and modified by taking into account the random behaviour of unreliable stations. Station's downtime is modelled as a fictive product added to the production sequence at appropriate positions. A general procedure for the insertion of fictive products is presented. The procedure considers the states up and down that a station may experience while processing the product mix. It consists of two main steps. Firstly, enumerate the station's states and insert fictive products where appropriate. Secondly, find the best buffer size that minimizes the cycle time. The proposed approach considers more parameters than the Markovian models and the approximation methods where multi-product production lines longer than 2-station 1-buffer can be studied. Numerical examples are presented to show all the steps involved to compute the expected cycle time. Buffer contribution to minimize the cycle time of the production line is also addressed. Simulation is used to validate the results obtained.
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The lean manufacturing seeks to ensure the quality of the service and the supplier?s products by the companies that implement this methodology, through the improvement of the research environment and the elimination of the classic...
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The lean manufacturing seeks to ensure the quality of the service and the supplier?s products by the companies that implement this methodology, through the improvement of the research environment and the elimination of the classic wastes present in any process. The research was developed in a metalworking company which presents as main problem the delay in the delivery of the finished product (rolling doors), generating complaints and nonconformities. For this reason, the need arises to make a proposal for improvement in its production process which allows to reduce the delivery time of the product to its customers and to guarantee its efficiency and productivity, using the tools and techniques of lean manufacturing. The methodology assumed in the study, corresponds to the philosophy of lean thinking to develop an improvement proposal where the following tools were used: value stream mapping, 9?S, single minute exchange of die, total productive maintenance, Kanban which provided the following possible results: total production process time would improve by 6.10%, value added time by 2.13%. The production increases from 24-26 doors per month, giving an improvement of 7.4% and mainly, the delivery time would decrease 590-554 min with a reduction of 6.10%, all these results lead to faster and more efficient deliveries to the customer. A case study was carried out in the metalworking company in Ibarra, Ecuador. The results also indicate that lean thinking contribute substantially to the operating performance of company is decreased about 7% of the time in operational performance.
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The aim of the present work was to study the possibility of coculture of the two halophytes Sesuvium portulacastrum-Sulla carnosa under saline and non-saline conditions with a special focus on plant vigour and phytodesalination po...
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The aim of the present work was to study the possibility of coculture of the two halophytes Sesuvium portulacastrum-Sulla carnosa under saline and non-saline conditions with a special focus on plant vigour and phytodesalination potential. Plants were grown for 2 months in unperforated pots filled with agricultural soil added or not with 1.5 g NaCl. kg~(-1) . Thereafter, shoots were harvested for growth, water status, and mineral composition. Soil samples were also analysed. Plant productivities and phytodesalination potentials were estimated based on shoot dry weights and sodium contents as well as soil soluble sodium contents. As grown for only 2 months in monoculture, S. carnosa could not desalinate the slightly saline soil, unlike S. portulacastrum, which extracted a quarter of the added sodium quantity. Nevertheless, such a noticeable phytodesalination capacity of S. portulacastrum did not reduce soil salinity and soluble sodium content. S. carnosa growth and productivity were enhanced by both salinity and coculture under non-saline conditions, which can be explained respectively by S. carnosa halo-phytic behaviour and probably a positive allelopathy exerted by S. portulacastrum. By contrast, a negative allelopathy seems exerted by S. carnosa under both saline and non-saline conditions. Under moderately saline conditions, both halophytes should be grown in monoculture. The stimulatory effect of S. portulacastrum on S. carnosa under non-saline conditions needs further investigations.
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This paper aims to show the development and design changes that have been done in SWRO Las Palmas III to achieve improvements in energy savings from the start-up in 1996 until today. We want to present the evolution of the differe...
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This paper aims to show the development and design changes that have been done in SWRO Las Palmas III to achieve improvements in energy savings from the start-up in 1996 until today. We want to present the evolution of the different energy recovery systems and new technologies that have been adapted to this facility in operation for the last 20 years. The plant began working with a production of 36,000 m~3/day with 45% recovery and six trains in two stages, with 300 ft~2-surface membranes and Francis turbine as energy recovery device, getting a specific energy consumption of 6.16kWh/m~3. In 1999, the plant increased production to 39,000 m~3/day maintaining recovery and the number of trains, mainly due to changes of membranes with an area of 315 ft~2. Besides it got a specific consumption decreased to 5.18kWh/m~3 due to the installation of a new energy recovery system, Pelton wheels. In the year 2000, Emalsa installed for first time in the world interstage pumps (so called booster pumps), increasing production to 44,000 m~3/day and recovery to 48%, reducing the specific consumption to 5.10kWh/m~3. At 2001 and 2002, production is increased to 57,000 m~3/day with the installation of a new RO train and with the addition of a new row of pressure vessels and membranes in all trains that increased recovery to 50% and decreased the specific consumption to 4.95kWh/m~3. From 2002 to 2007 plant increases production to 81,000 m~3/day, adding new more efficient trains increasing global recovery to 52% and reducing specific consumption to 4.6kWh/m~3. Since 2008, the company began to replace the Pelton wheels for isobaric energy recovery systems, replacing in 2008 the first two Pelton wheels with a single isobaric system of two trains, reducing the specific consumption of these two trains more than 20%. In 2009, two new isobaric systems were installed, one per train, getting the plant a total of 86,000 m~3/day and a total specific consumption of 4.15kWh/m~3. Currently, the company made a new train design, which improves the operating conditions when Pelton wheels are replaced for isobaric systems. This project will be operational in November 2010 and it has been predicted a decrease in specific consumption below 4kWh/m~3. With all this improvements, it can be said that Las Palmas III SWRO plant has been a pioneer in the world of desalination and a lively look at the history of energy recovery in SWRO plants.
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Purpose of this paper is to explore the possibility of increasing manufacturing capacities in the short run through battery management of automated guided vehicles (AGVs). The paper investigates how the duration of battery chargin...
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Purpose of this paper is to explore the possibility of increasing manufacturing capacities in the short run through battery management of automated guided vehicles (AGVs). The paper investigates how the duration of battery charging for AGVs can be varied to increase flexibility of a manufacturing system. The key concept is that a lead acid battery, the most widely used battery type for AGVs, receives most of its charge during the initial phase (time) of charging as opposed to the later phase. Consequently, more productive hours can be obtained from the AGVs by reducing the duration of each charging occurrence (i.e., by recharging the batteries to less than full capacity). In this approach, an AGV needs to be recharged more frequently, but the total productive hours available from the AGVs can increase. Simulation models were developed to investigate the effect of this approach. Results show that productivity of a manufacturing system increases significantly through this approach. This approach can be quite helpful for a firm if AGVs are the bottleneck in its manufacturing plant and the firm needs to have a significant improvement of its productivity in the short-run. Also, this approach does not require a firm to make a large investment to add more AGVs to its facility.
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The robust control over open pit mining is validated. It is shown that the current coupling of production systems based on equality of averaged capacities of mining and transportation equipment ensures no operational stability in ...
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The robust control over open pit mining is validated. It is shown that the current coupling of production systems based on equality of averaged capacities of mining and transportation equipment ensures no operational stability in an open pit mine. The article presents an optimization model and the modeling procedure for scheduling equipment repair halts such that to gain sustainable productivity due to uniformly distributed capacity of operational shoveling and haulage equipment. The authors have set stability limits, which imparts robustness to a controlled system and moves management to a new level.
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The warehouse problem with deterministic production cost, selling prices, and demand was introduced in the 1950s and there is a renewed interest recently due to its applications in energy storage and arbitrage. In this paper, we c...
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The warehouse problem with deterministic production cost, selling prices, and demand was introduced in the 1950s and there is a renewed interest recently due to its applications in energy storage and arbitrage. In this paper, we consider two extensions of the warehouse problem and develop efficient computational algorithms for finding their optimal solutions. First, we consider a model where the firm can invest in capacity expansion projects for the warehouse while simultaneously making production and sales decisions in each period. We show that this problem can be solved with a computational complexity that is linear in the product of the length of the planning horizon and the number of capacity expansion projects. We then consider a problem in which the firm can invest to improve production cost efficiency while simultaneously making production and sales decisions in each period. The resulting optimization problem is non-convex with integer decision variables. We show that, under some mild conditions on the cost data, the problem can be solved in linear computational time. (c) 2016 Wiley Periodicals, Inc. Naval Research Logistics 63: 367-373, 2016
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Seiichi Nakajima provided overall equipment effectiveness (OEE) to measure productivity and perform diagnostics at the equipment level. However, a literature review indicates that such metrics are lacking at the factory level. In ...
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Seiichi Nakajima provided overall equipment effectiveness (OEE) to measure productivity and perform diagnostics at the equipment level. However, a literature review indicates that such metrics are lacking at the factory level. In order to address this gap, an overall throughput effectiveness (OTE) metric is developed. The purpose of OTE is twofold: it measures factory-level performance and can also be used for performing factory-level diagnostics such as bottleneck detection and identifying hidden capacity. The task of coming up with such a metric was achieved by defining a set of commonly occurring predefined subsystems including series, parallel, assembly and expansion. OTE was developed for each of these predefined subsystems. It also accounts for subsystems processing multiple products and performing rework. Any factory layout can be modelled using a combination of the predefined subsystems, which allows determination of the overall factory effectiveness (OFE). More importantly, OTE has the potential to automate the entire factory-level performance diagnostics, hence drive continuous productivity improvement quantitatively. This paper explains the OTE development methodology, validates the developed OTE metrics and demonstrates its diagnostic ability. Application of OTE to a wafer fab and glass manufacturing case study showed that productivity bottleneck and opportunities for improvement can be identified quantitatively.
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Greenhouse vegetable production (GVP) has become an important source of public vegetable consumption and farmers' income in China. However, various pollutants can be accumulated in GVP soils due to the high cropping index, large a...
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Greenhouse vegetable production (GVP) has become an important source of public vegetable consumption and farmers' income in China. However, various pollutants can be accumulated in GVP soils due to the high cropping index, large agricultural input, and closed environment. Ecological toxicity caused by excessive pollutants' accumulation can then lead to serious health risks. This paper was aimed to systematically review the current status of soil environmental quality, analyze their impact factors, and consequently to propose integrated management strategies for GVP systems. Results indicated a decrease in soil pH, soil salinization, and nutrients imbalance in GVP soils. Fungicides, remaining nutrients, antibiotics, heavy metals, and phthalate esters were main pollutants accumulating in GVP soils comparing to surrounding open field soils. Degradation of soil ecological function, accumulation of major pollutants in vegetables, deterioration of neighboring water bodies, and potential human health risks has occurred due to the changes of soil properties and accumulation of pollutants such as heavy metals and fungicides in soils. Four dominant factors were identified leading to the above-mentioned issues including heavy application of agricultural inputs, outmoded planting styles with poor environmental protection awareness, old-fashion regulations, unreasonable standards, and ineffective supervisory management. To guarantee a sustainable GVP development, several strategies were suggested to protect and improve soil environmental quality. Implementation of various strategies not only requires the concerted efforts among different stakeholders, but also the whole lifecycle assessment throughout the GVP processes as well as effective enforcement of policies, laws, and regulations. (C) 2016 Elsevier Ltd. All rights reserved.
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