Removal of p-xylene from an air stream in a hybrid biofilter

Biofiltration of an air stream containing p-xylene has been studied in a laboratory hybrid biofilter packed with a mixture of mature pig compost, forest soil and the packing material which was made of polyethylene (PE) and used in the moving bed biological reactor (MBBR) in wastewater treatment. Three flow rates, 9.17, 19.87 and 40.66 m(3)m(-2)h(-1), were investigated for p-xylene inlet concentration ranging from 0.1 to 3.3 g m(-3). A high elimination capacity of 80 g m(-3)h(-1) corresponding to removal efficiency of 96% was obtained at a flow rate of 9.17 m(3)m(-2)h(-1) (empty bed residence time of 132 s). At a flow rate of 40.66 m(3)m(-2)h(-1) (empty bed residence time of 30s), the maximum elimination capacity for p-xylene was 40 g m(-3)h(-1) and removal efficiencies were in the range of 47-100%. The production of carbon dioxide (P(CO(2))) is proportional to elimination capacity (EC) and the linear relation was formulated as P(CO(2))=1.65EC+15.58. Stable pH values ranging from 6.3 to 7.6 and low pressure drop values less than 0.2 cm H(2)O (19.6 Pa) of packing media in compost-based biofilter of hybrid biofilter were observed, which avoided acidification and compaction of packing media and sustained the activity of microorganism populations.     

Evaluating the impact of cannibalization on fleet performance

Organizations that utilize fleets of expensive repairable equipment are faced with numerous challenges related to the specification of maintenance policies and the allocation of maintenance resources. The associated maintenance decisions can have a drastic impact on fleet performance. Due to the significant acquisition costs associated with the components that comprise the units of equipment in the fleet, cannibalization is often used in the absence of available spare parts to enable fleet maintenance managers to satisfy fleet performance constraints such as readiness requirements. This research is focused on the development and analysis of a closed‐network, discrete‐event simulation model that is used to assess the impacts of cannibalization, small spare parts inventories and maintenance‐induced damage on a fleet of systems. Using numerical examples, we demonstrate the comparison between cannibalization and the investment in limited spare parts inventories. We evaluate fleet performance using average readiness and total maintenance cost. Specifically, we demonstrate that investments in spare parts inventories can reduce the need for and value of cannibalization. However, our results also support the use of cannibalization as a low‐cost alternative to investing in expensive spare parts. We also explore the impact of damage induced by maintenance on fleet performance. Specifically, we demonstrate that maintenance‐induced damage can reduce the benefit of cannibalization while drastically increasing maintenance expenditures. Copyright © 2006 John Wiley & Sons, Ltd.     

Evaluating the effects of capacity constraints and demand patterns on supply chain replenishment strategies

This research considers inventory replenishment in a stochastic, multi-echelon supply chain involving both production and distribution functions. Simulation is used to compare distribution/material requirements planning (DRP/MRP), re-order point (ROP) and Kanban (KBN) replenishment strategies. Additional experimental factors include the demand pattern and the existence of manufacturing capacity constraints. Trade-off curves between inventory and delivery performance are generated. Statistical techniques, including analysis of variance (ANOVA), are then used to compare the areas under the trade-off curves and determine the relative dominance among the replenishment strategies. The methodology is used to identify both main and interaction effects. With seasonal demand, DRP/MRP performance is found to be best, followed by ROP and KBN, respectively. Without seasonal demand, the relative performance ranking depends on the presence of capacity constraints. Without capacity constraints, ROP performs best, followed by DRP/MRP and KBN. With capacity constraints, the ranking is reversed. This difference in behaviour can be explained using queuing analysis.     

The impact of total quality management on supply chain management and firm's supply performance

This research investigates the relationships among total quality management practices (TQMP), supply chain management practices (SCMP) and firm's supply performance (FSP) in the automotive industry in Thailand. The measurement instruments for SCMP, TQMP and FSP were developed based on an extensive literature review and verified by experts, pilot test and various statistical techniques to ensure reliability and validity in structural equation modeling constructs. The hypothesized model was tested through a path analysis. Qualitative case studies of two large first-tier automotive suppliers were conducted to obtain more in-depth information. We found that the set of SCMP, TQMP and FSP measures are reliable and valid for Thailand's automotive industry. TQMP not only has a significant direct positive impact on SCMP and on FSP but also a significant indirect positive impact on FSP through SCMP.     

The impact of buffering strategies on the performance of production line systems

This paper investigates the effect of different buffering strategies on the performance of production line systems. Three models of different buffering strategies are studied. Each buffering strategy represents a different degree or flexibility of the storage buffers in the system. We first prove the analytical result that system throughput increases with the degree of flexibility for the three models in this study. Simulation results are then presented to compare the performance of the three models under different system configurations. The results provide useful information for evaluating different design alternatives for a production line.     

The impact of sorting strategies on automated sortation system performance

In this paper, we develop an analytical model of an order sortation system used in automated distribution centers. In such systems, groups of orders are delivered to a recirculating conveyor system where they are sorted into shipping lanes for final preparation and loaded onto waiting trucks. We develop a model of the sorting process, which incorporates the stochastic elements of these systems, to determine the relative merits of two common categories of sorting strategies found in industry: fixed priority schemes and the next available rule. Fixed priority schemes include such popular rules as sort the largest (or smallest) orders first. We show that in systems with little lane blocking, a rule which assigns the next available order to a shipping lane will outperform any fixed priority scheme in terms of sorting time and system throughput while in systems with significant lane blocking, the sorting rule has little impact.     

The impact of sorting strategies on automated sortation system performance

In this paper, we develop an analytical model of an order sortation system used in automated distribution centers. In such systems, groups of orders are delivered to a recirculating conveyor system where they are sorted into shipping lanes for final preparation and loaded onto waiting trucks. We develop a model of the sorting process, which incorporates the stochastic elements of these systems, to determine the relative merits of two common categories of sorting strategies found in industry: fixed priority schemes and the next available rule. Fixed priority schemes include such popular rules as “sort the largest (or smallest) orders first”. We show that in systems with little lane blocking, a rule which assigns the next available order to a shipping lane will outperform any fixed priority scheme in terms of sorting time and system throughput while in systems with significant lane blocking, the sorting rule has little impact.     

A decision support framework for global supply chain modelling: an assessment of the impact of demand,supply and lead-time uncertainties on performance

We developed a decision support framework for a global manufacturer of specialty chemicals to study the relative impact of demand, supply and lead-time uncertainties on cost and customer service performance. Our approach combines optimisation and simulation methodologies as follows: mathematical models provide optimal plans via a novel approach to the supply chain planning mechanism of the Company. Simulation models execute the supply chain plans so as to allow the examination of the outcomes under the various sources of uncertainty. The iterative use of optimisation and simulation methodologies allows the user the benefit of obtaining optimal solutions while revealing the impact of uncertainties on system performance. Our results indicate that demand uncertainty has the greatest negative impact on performance for the supply chain that we modelled in this study, emphasising the importance of effective forecasting. The relative importance of supply and lead-time uncertainties varies according to the performance measures. While our results are valid for the specific supply chain and the operating environment we modelled, our study emphasises the importance of the ability to model supply chains realistically to obtain valid and useful results.     

The impact of contract parameters on the supply chain performance under different power constellations

Reporting forecast data is a common method used to improve the functioning of supply chains (SCs) and to reduce supply shortages. Customers tend to report the maximum possible demand as a forecast if restrictions are missing. Such a forecast is useless for suppliers. Hence, special contracts are needed to enhance the value of forecast data and therefore the cooperation between SC partners. In this paper, such a contract is presented. It encourages the customer to report a more realistic forecast. Deviations from the reported forecast are punished in different ways: If the customer reported too much and wants to release less than what was reported, he has to pay a penalty. On the other hand, the customer has the flexibility to purchase more than reported to meet the demand on his outlet but at the cost of an additional fee. This paper analyses how different contract parameters affect the performance of the SC, in particular when the bargaining power of customer and supplier is not equally distributed. Results show that the supplier and therefore the SC is better off if the supplier leaves the contractual cost parameters untouched but hides the true value of flexibility, especially when the customer is less powerful than the supplier.     

Assessing the impact of performance determinants in complex MTO/ETO supply chains through an extended hybrid modelling approach

In make-to-order (MTO)/engineer-to-order (ETO) business environments multiple customer-oriented projects compete for and share resources through interdependent engineering and production activities. Deep knowledge of critical dimensions that affect performance is key in this context. For this, we propose a set of determinants – workload, complexity, outsourcing, design reuse, project type, and knowledge/experience with technology, that impact performance. These determinants are input to an extended hybrid simulation model using system dynamics (SD), discrete event simulation (DES) and agent-based simulation (ABS) that tackles the needs imposed by activities of very different nature, as the project development and manufacturing/assembly operations. The hybrid model is applied to the case of an advanced manufacturing company. Through Monte Carlo sampling, the influence of different combinations of determinants in the performance variability is assessed. A correlation analysis shows evidence of association between all performance determinants and the project time and cost, while no evidence of association between the design reuse and project type determinants and the manufacturing and assembly time.     

Analysis of excess water impact on the structural performance of flexible pavements

Excess water in pavement foundations is one of the major factors contributing to pavements deterioration. In recent years, a number of research studies have been carried out to understand the water movement into pavements and to assess its detrimental effects on the mechanical response of the foundations. However, these studies do not quantify the impact of suction reduction or pore pressure buildup in the foundations on the pavement response. In this paper, coupled finite element analyses are carried out to investigate the effect of the excess water in the granular foundations on the structural performance of flexible pavements. The coupled analyses simulate critical features governing the foundations' hydromechanical response including the transient unsaturated flow and porous nonlinear behaviour of the foundations under moving wheel loads. Furthermore, a parametric study that examines the influences of various loading and foundation parameters on the performance of pavements subjected to excessive moisture scenarios is carried out. The numerical analysis results obtained in this paper are qualitatively in line with the empirical observations reported in the literature.     

The impact of supply chain analytics on operational performance: a resource-based view

This study seeks to better understand the role of supply chain analytics (SCA) on supply chain planning satisfaction and operational performance. We define the architecture of SCA as the integration of three sets of resources, data management resources (DMR), IT-enabled planning resources and performance management resources (PMR), from the perspective of a resource-based view. Based on the data collected from 537 manufacturing plants, we test hypotheses exploring the relationships among these resources, supply chain planning satisfaction, and operational performance. Our analysis supports that DMR should be considered a key building block of manufacturers’ business analytics initiatives for supply chains. The value of data is transmitted to outcome values through increasing supply chain planning and performance capabilities. Additionally, the deployment of advanced IT-enabled planning resources occurs after acquisition of DMR. Manufacturers with sophisticated planning technologies are likely to take advantage of data-driven processes and quality control practices. DMR are found to be a stronger predictor of PMR than IT planning resources. All three sets of resources are related to supply chain planning satisfaction and operational performance. The paper concludes by reviewing research limitations and suggesting further SCA research issues.     

受控堆肥生物降解法测定全生物降解塑料(PBS)性能

依据GB/T 19277-2003/ISO 14855:1999,对降解塑料聚丁二酸丁二醇酯(PBS)、丁二酸对苯二甲酸丁二醇共聚酯(PBST)进行堆肥化条件下生物降解能力的测定.试验结果,用此方法评价塑料生物降解性能是可行的.PBS、PBST具有良好的生物降解性.建立了高分子材料测定方法的操作系统.     

The performance impact of supply chain agility and supply chain adaptability: the moderating effect of product complexity

Even though research has suggested that supply chain agility and supply chain adaptability are distinct capabilities, little is known about their performance effects and about the contextual conditions under which they are effective. Based on a sample of 143 German firms, we empirically investigate the effects of supply chain agility and supply chain adaptability on cost performance and operational performance using hierarchical regression analysis. We ground our investigation in the dynamic capabilities view and contingency theory. We find that supply chain agility and supply chain adaptability positively affect both cost performance and operational performance. We further find evidence for a mediating role of supply chain agility in the links between supply chain adaptability and performance. Product complexity positively moderates the links between supply chain adaptability and cost performance, and supply chain adaptability and operational performance. The results contribute to the literature by offering a more nuanced understanding of the performance implications of supply chain agility and supply chain adaptability, thereby addressing the crucial question of why their benefits may or may not materialise under varying levels of product complexity.     

The impact of strategic inventory and procurement strategies on green product design in a two-period supply chain

This study analyses the impact of power structures and strategic inventory on the development-intensive and marginal-cost-intensive green product types under three procurement strategies. The results suggest that (i) in the manufacturer-Stackelberg game, the retailer retains strategic inventory to earn higher profits. The retailer's decision improves profit for the manufacturer and greening level of the product; (ii) for the marginal-cost-intensive green product, the power structures and procurement strategies cannot make any impact on the greening level and the retailer cannot build up strategic inventory under retailer-Stackelberg game; (iii) under the Nash game, the procurement decision creates conflict between the supply chain members for marginal-cost-intensive green products; (iv) if the retailer does not maintain strategic inventory or procures product in a single lot, then the manufacturer prefers to produce marginal-cost-intensive products and retailer prefers to sale development-intensive products to receive maximum profits under manufacturer-Stackelberg game. The optimal preferences are concurrent under retailer-Stackelberg game, but not under the Nash game; (v) single-period equilibrium solutions may exhibit sub-optimal characteristics, but two-period planning can lead to exemplary outcomes in the perspective of the greening level and profits of the supply chain members.     

Adoption of green supply chain management practices and their impact on performance: an exploratory study of Indian manufacturing firms

Research on green supply chain management (GSCM) or sustainable supply chain management (SSCM) has attracted increased attention in recent years. Although GSCM/SSCM has been studied for developed and developing countries, there has been little information about the adoption of GSCM/SSCM practices in India. This article presents one of the earliest surveys on GSCM practices in Indian manufacturing firms. The items for the survey were developed based on the extant literature and feedback from corporates. Some of the major findings of the survey are as follows. We found that the state of adoption of GSCM practices by Indian firms was still in its infancy, the awareness of environmental sustainability was quite low among consumers, and the regulatory framework was also lacking in terms of promoting environmental sustainability. Results of data analysis showed that supplier collaboration for environmental sustainability had a positive impact on environmentally sustainable product design and logistics, which in turn was positively related to competitiveness and economic performance of the firm. We compared the results with the observations made by other researchers for developed and developing countries and provided managerial implications for the government and manufacturers as to what steps need to be taken to generate awareness towards environmental sustainability and facilitate the adoption of GSCM practices among Indian firms to a greater extent. We conclude the paper by indicating directions for future research on GSCM/SSCM.     

Spatial distribution of water supply reliability and critical links of water supply to crucial water consumers under an earthquake

This paper describes a process to characterize spatial distribution of water supply reliability among various consumers in a water system and proposes methods to identify critical links of water supply to crucial water consumers under an earthquake. Probabilistic performance of water supply is reflected by the probability of satisfying consumers’ water demand, Damage Consequence Index (DCI) and Upgrade Benefit Index (UBI). The process is illustrated using a hypothetical water supply system, where direct Monte Carlo simulation is used for estimating the performance indices. The reliability of water supply to consumers varies spatially, depending on their respective locations in the system and system configuration. The UBI is adopted as a primary index in the identification of critical links for crucial water consumers. A pipe with a relatively large damage probability is likely to have a relatively large UBI, and hence, to be a critical link. The concept of efficient frontier is employed to identify critical links of water supply to crucial water consumers. It is found that a group of links that have the largest UBI individually do not necessarily have the largest group UBI, or be the group of critical links.     

Anaerobic biodegradation of an organic by-products leachate by interaction with different mine tailings

Deinking by-products from paper recycling have been used as cover materials on acid-producing tailings. Due to residual cellulose, anaerobic degradation leads to the production of an organic-rich leachate, which may percolate through the tailings. This study aims at describing the influence of the tailings’ characteristics on the attenuation of organic matter in leachate and at discussing the degradation mechanisms. To this end, leachate was mixed with different types of tailings, including three unoxidized tailings with varying acid generation potentials and one tailing in three states of oxidation. Regularly, selected biochemical parameters were analyzed to access the evolution of organic components. The results show that when leachate from deinking by-products was placed in contact with tailings, phase and acid–base balance reactions took place in the beginning. Subsequently, oxidation–reduction reactions dominated the chemistry of the system. The type, the constituents, and the state of oxidation of the mine tailings condition the mechanisms of biodegradation of organic components. Methanogenesis was predominant in the control sample (pure organic leachate) but was absent in all leachate-tailings mixtures. No biodegradation was observed in the liquid phase for oxidized tailings and the organic concentration remained constant for unoxidized tailings, independently of the acid-generation potential. The biodegradation efficiency was optimal when the leachate was in contact with a mixture of oxidized and unoxidized tailings due to sulfate-reduction.     

A socio-technical view of performance impact of integrated quality and sustainability strategies

This research seeks to examine the direct effects of social and technical integration on deployment of quality and sustainability management programmes and the indirect effect of those on quality and sustainability performance. We also seek to test the spillover effects of quality and sustainability management programmes on sustainability and quality performance, respectively. Socio-technical systems (STSs) theory is used to test the role of social and technical integration on quality and sustainability management programmes. The framework of integrated management system, as supported by both STSs and complementarity theory, is used to test the direct and spillover effects of quality and sustainability management programmes. A large multi-country sample is used to empirically test our theory-induced hypotheses. The findings support that social and technical integration are indeed significant enablers for the positive relationships that quality and sustainability programmes have on quality performance and sustainability performance. Specifically, the results show that while social integration has both direct and indirect effects on quality and sustainability performance, technical integration impacts quality and sustainability performance only through the mediation effect of the respective programmes. The results do not support the spillover effects of quality and sustainability management programmes on sustainability and quality performance. Implications of the findings on academic knowledge and managerial practice are offered.     

Theoretical and experimental study of the processes of water purification in a biofilter

This paper presents the results of experimental measurements of substrate concentrations characterizing the efficiency of polluted water purification by a drop biofilter. A model describing the process of purification based on the diffusion-kinetic approach is presented. A good agreement between the experimental and theoretically calculated characteristics of the purification process has been shown. A simple semiempirical relation for estimating the operation of the drop biofilter is given. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 82, No. 2, pp. 273–282, March–April, 2009.