The Experts below are selected from a list of 1002396 Experts worldwide ranked by ideXlab platform
Kenichi Soga - One of the best experts on this subject based on the ideXlab platform.
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ureolytic activities of a urease producing bacterium and purified urease enzyme in the anoxic condition implication for subseafloor sand Production Control by microbially induced carbonate precipitation micp
Ecological Engineering, 2016Co-Authors: Ningjun Jiang, Hideyoshi Yoshioka, Koji Yamamoto, Kenichi SogaAbstract:Abstract Microbially induced carbonate precipitation (MICP) involves the hydrolysis of urea by indigenous or introduced urease-producing bacteria, which induces carbonate precipitation. By allowing this process to occur in the pores of unconsolidated sand, sand particles bond together, creating a sandstone like material. Although MICP has been explored recently for possible applications in civil and construction engineering, this study examines its application to sand Production Control during hydrate gas exploitation from subseafloor sediments. The major uncertainty is the ureolytic activities of bacteria and associated enzyme under the subseafloor condition. The main aim of this study was to quantify the ureolytic efficiency of a urease-producing bacterium and purified urease enzyme in the oxic and anoxic conditions. The purified urease enzyme and Bacillus megaterium were subject to bench shaking ureolyic activity tests in both conditions. Biochemical parameters including urea concentration, electric conductivity (EC), pH, and optical density at 600 nm (OD 600 ) of the solution at different time intervals were measured. As a quality Control procedure, dissolved oxygen concentration (DO) of the final solutions was also measured. Results show that the effect of oxygen availability on ureolytic efficiency of purified urease enzyme is marginal. However, anoxic ureolytic performance of B. megaterium is better than its oxic counterpart. It is also found that higher concentration of urease and multi-amendment of bacteria help raise ureolytic efficiency. In order to sustain ureolytic efficiency and facilitate its up-scaled field application, several practice measures can be implemented including growing bacteria aerobically to exponential stage before implemented into the subseafloor sites, injecting larger bacteria cell number, and repeatedly supplying fresh bacteria cells.
Ningjun Jiang - One of the best experts on this subject based on the ideXlab platform.
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ureolytic activities of a urease producing bacterium and purified urease enzyme in the anoxic condition implication for subseafloor sand Production Control by microbially induced carbonate precipitation micp
Ecological Engineering, 2016Co-Authors: Ningjun Jiang, Hideyoshi Yoshioka, Koji Yamamoto, Kenichi SogaAbstract:Abstract Microbially induced carbonate precipitation (MICP) involves the hydrolysis of urea by indigenous or introduced urease-producing bacteria, which induces carbonate precipitation. By allowing this process to occur in the pores of unconsolidated sand, sand particles bond together, creating a sandstone like material. Although MICP has been explored recently for possible applications in civil and construction engineering, this study examines its application to sand Production Control during hydrate gas exploitation from subseafloor sediments. The major uncertainty is the ureolytic activities of bacteria and associated enzyme under the subseafloor condition. The main aim of this study was to quantify the ureolytic efficiency of a urease-producing bacterium and purified urease enzyme in the oxic and anoxic conditions. The purified urease enzyme and Bacillus megaterium were subject to bench shaking ureolyic activity tests in both conditions. Biochemical parameters including urea concentration, electric conductivity (EC), pH, and optical density at 600 nm (OD 600 ) of the solution at different time intervals were measured. As a quality Control procedure, dissolved oxygen concentration (DO) of the final solutions was also measured. Results show that the effect of oxygen availability on ureolytic efficiency of purified urease enzyme is marginal. However, anoxic ureolytic performance of B. megaterium is better than its oxic counterpart. It is also found that higher concentration of urease and multi-amendment of bacteria help raise ureolytic efficiency. In order to sustain ureolytic efficiency and facilitate its up-scaled field application, several practice measures can be implemented including growing bacteria aerobically to exponential stage before implemented into the subseafloor sites, injecting larger bacteria cell number, and repeatedly supplying fresh bacteria cells.
Hideyoshi Yoshioka - One of the best experts on this subject based on the ideXlab platform.
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ureolytic activities of a urease producing bacterium and purified urease enzyme in the anoxic condition implication for subseafloor sand Production Control by microbially induced carbonate precipitation micp
Ecological Engineering, 2016Co-Authors: Ningjun Jiang, Hideyoshi Yoshioka, Koji Yamamoto, Kenichi SogaAbstract:Abstract Microbially induced carbonate precipitation (MICP) involves the hydrolysis of urea by indigenous or introduced urease-producing bacteria, which induces carbonate precipitation. By allowing this process to occur in the pores of unconsolidated sand, sand particles bond together, creating a sandstone like material. Although MICP has been explored recently for possible applications in civil and construction engineering, this study examines its application to sand Production Control during hydrate gas exploitation from subseafloor sediments. The major uncertainty is the ureolytic activities of bacteria and associated enzyme under the subseafloor condition. The main aim of this study was to quantify the ureolytic efficiency of a urease-producing bacterium and purified urease enzyme in the oxic and anoxic conditions. The purified urease enzyme and Bacillus megaterium were subject to bench shaking ureolyic activity tests in both conditions. Biochemical parameters including urea concentration, electric conductivity (EC), pH, and optical density at 600 nm (OD 600 ) of the solution at different time intervals were measured. As a quality Control procedure, dissolved oxygen concentration (DO) of the final solutions was also measured. Results show that the effect of oxygen availability on ureolytic efficiency of purified urease enzyme is marginal. However, anoxic ureolytic performance of B. megaterium is better than its oxic counterpart. It is also found that higher concentration of urease and multi-amendment of bacteria help raise ureolytic efficiency. In order to sustain ureolytic efficiency and facilitate its up-scaled field application, several practice measures can be implemented including growing bacteria aerobically to exponential stage before implemented into the subseafloor sites, injecting larger bacteria cell number, and repeatedly supplying fresh bacteria cells.
Koji Yamamoto - One of the best experts on this subject based on the ideXlab platform.
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ureolytic activities of a urease producing bacterium and purified urease enzyme in the anoxic condition implication for subseafloor sand Production Control by microbially induced carbonate precipitation micp
Ecological Engineering, 2016Co-Authors: Ningjun Jiang, Hideyoshi Yoshioka, Koji Yamamoto, Kenichi SogaAbstract:Abstract Microbially induced carbonate precipitation (MICP) involves the hydrolysis of urea by indigenous or introduced urease-producing bacteria, which induces carbonate precipitation. By allowing this process to occur in the pores of unconsolidated sand, sand particles bond together, creating a sandstone like material. Although MICP has been explored recently for possible applications in civil and construction engineering, this study examines its application to sand Production Control during hydrate gas exploitation from subseafloor sediments. The major uncertainty is the ureolytic activities of bacteria and associated enzyme under the subseafloor condition. The main aim of this study was to quantify the ureolytic efficiency of a urease-producing bacterium and purified urease enzyme in the oxic and anoxic conditions. The purified urease enzyme and Bacillus megaterium were subject to bench shaking ureolyic activity tests in both conditions. Biochemical parameters including urea concentration, electric conductivity (EC), pH, and optical density at 600 nm (OD 600 ) of the solution at different time intervals were measured. As a quality Control procedure, dissolved oxygen concentration (DO) of the final solutions was also measured. Results show that the effect of oxygen availability on ureolytic efficiency of purified urease enzyme is marginal. However, anoxic ureolytic performance of B. megaterium is better than its oxic counterpart. It is also found that higher concentration of urease and multi-amendment of bacteria help raise ureolytic efficiency. In order to sustain ureolytic efficiency and facilitate its up-scaled field application, several practice measures can be implemented including growing bacteria aerobically to exponential stage before implemented into the subseafloor sites, injecting larger bacteria cell number, and repeatedly supplying fresh bacteria cells.
Ali Gharbi - One of the best experts on this subject based on the ideXlab platform.
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joint optimal Production Control preventive maintenance policy for imperfect process manufacturing cell
International Journal of Production Economics, 2012Co-Authors: K Dhouib, Ali Gharbi, M Ben N AzizaAbstract:Abstract Production, maintenance, and quality are often modeled as separate problems, despite the strong link that exists between these primary components of any manufacturing system. This paper deals with an integrated approach for the joint optimization of Production-inventory Control and preventive maintenance policy for a manufacturing cell comprising an imperfect process where the ‘in-Control’ period has a general deterioration distribution. The Production-inventory Control policy based on the hedging point policy consists of building and maintaining a security stock of finished products in order to respond to demand and to avoid shortages during restoration actions. Restoration actions are planned when the system switches to the ‘out-of-Control’ state and starts producing non-conforming items. The manufacturing cell is also subject to an age-based preventive maintenance policy in order to reduce the shift rate to the ‘out-of-Control’ state. The main objective of this paper is to determine the joint optimal policy that minimizes the overall cost, which is comprised of setup, maintenance, inventory holding, and shortage costs, as well as the cost incurred by producing non-conforming items. A mathematical model is proposed, and the expression of the overall incurred cost is derived and used as a basis for the optimal determination of the joint Production-inventory Control and preventive maintenance policy. These issues are illustrated using numerical examples. It is found that performing preventive maintenance will yield reductions in the overall incurred cost. Sensitivity analyses are also carried out in order to illustrate the robustness of the proposed methodology.
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maintenance scheduling and Production Control of multiple machine manufacturing systems
Computers & Industrial Engineering, 2005Co-Authors: Ali Gharbi, Jean-pierre KennéAbstract:This paper deals with the Production and preventive maintenance Control problem for a multiple-machine manufacturing system. The objective of such a problem is to find the Production and preventive maintenance rates for the machines so as to minimize the total cost of inventory/backlog, repair and preventive maintenance. A two-level hierarchical Control model is presented, and the structure of the Control policy for both identical and nonidentical manufacturing systems is described using parameters, referred to here as input factors. By combining analytical formalism with simulation-based statistical tools such as experimental design and response surface methodology, an approximation of the optimal Control policies and values of input factors are determined. The results obtained extend those available in existing literature to cover non-identical machine manufacturing systems. A numerical example and a sensitivity analysis are presented in order to illustrate the robustness of the proposed approach. The extension of the proposed Production and preventive maintenance policies to cover large systems (multiple machines, multiple products) is discussed.
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stohastic optimal Production Control problem with corrective maintenance
Computers & Industrial Engineering, 2004Co-Authors: Jean-pierre Kenné, Ali GharbiAbstract:Abstract We consider a Production Control problem in a manufacturing system with failure-prone machines and a constant demand rate. The objective is to minimise a discounted inventory holding and backlog cost over an infinite planning horizon. The availability of the machines is improved through a corrective maintenance strategy. The decision variables are the Production and the machine repair rates, which influence the inventory levels and the system capacity, respectively. It is shown that, for constant demand rates and exponential failure and repair times distributions of the machines, the hedging point policy is optimal. Such a policy is modified herein and parameterised by factors representing the thresholds of involved products and switching inventory levels for corrective maintenance. With the obtained policy, simulation experiments are combined to experimental design and response surface methodology to estimate the optimal Production and corrective maintenance policies, respectively. The usefulness of the proposed approach is illustrated through a numerical example.
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optimal Production Control problem in stochastic multiple product multiple machine manufacturing systems
Iie Transactions, 2003Co-Authors: Ali Gharbi, Jean-pierre KennéAbstract:Abstract This paper deals with the issue of Production Control in a manufacturing system with multiple machines which are subject to breakdowns and repairs. The Control variables considered are the Production rates for different products on the machines. Our objective is to minimize the expected total discounted cost due to the finished good inventories and backlogs. Based on the structure of the hedging point policy, a parameterized near-optimal Production policy for a multiple-product manufacturing system is proposed. The analytical formalism is combined with simulation-based statistical tools, such as experimental design and response surface methodology. The aim of such a combination is to provide an approximation of the optimal Control policy. In the proposed approach, the parameterized near-optimal Control policy is used as an input for the simulation model. For each entry consisting of a combination of parameters, the cost incurred is obtained. The significant effects of the Control variables are de...
