Changes in the regulatory requirements and the forthcoming Disinfectant/Disinfection By-Products （D/DBP） Rule will require that drinking water treatment facilities be operated to achieve maximum removals of particle...Changes in the regulatory requirements and the forthcoming Disinfectant/Disinfection By-Products （D/DBP） Rule will require that drinking water treatment facilities be operated to achieve maximum removals of particles and disinfectant tolerant microorganisms as well as natural organic matter （NOM）. For drinking water production, the use of membrane filtration processes such as microfiltration and ultrafiltration （MF/UF） alone to satisfy the turbidity, particle and microorganism removal a requirement of the surface water treatment regulation （SWTR） is not enough. MF/UF treatment processes can achieve only nominal （10 percent） removal of disinfection by-products （DBP） precursors （James, et al., 1995）. On the other hand, too fast fouling can make the filtration processes more difficult to carry on. To solve these problems, many authors have been interested in installing coagulation pretreatment before membrane filtration to improve membrane performance. However, previous studies reported conflicting results. Some supported the effectiveness of coagulation pretreatment, while others contended that coagulation aggravated membrane performance. This research aims to identify the effects of coagulation pretreatment on membrane filtration through a pilot study using PVDF membrane in combination with analyzing the rationale of coagulation. Another objective of this research was to evaluate the different impacts on membrane performance of using different membrane modules （the submerged module and pressured module）. The results showed that coagulation pretreatment greatly improved the membrane performance, extending the filtration time as well as reducing the permeated organic level, and that the submerged module is much more efficient than the pressured module.展开更多
The present work aims to evaluate the increase in the number of spot welds in the 16 × 16 type fuel assembly structure that connects guide thimbles and spacer grids, in order to provide a proper joint for this co...The present work aims to evaluate the increase in the number of spot welds in the 16 × 16 type fuel assembly structure that connects guide thimbles and spacer grids, in order to provide a proper joint for this connection. This new and improved process can provide more stiffness to the whole structure, since the number of spots raised from four to eight. A 3-D geometric model of a guide thimble section was generated in a CAD （computer aided design） program （SolidWorks）. After that, the geometric model was imported to a CAE （computer aided engineering） program （ANSYS Mechanical APDL, Release 14.0）, where the finite element model was built, considering the guide thimble geometry assembled with the spacer grid through the welded connections. Boundaries conditions were implemented in the model in order to simulate the correct physical behavior due to the operation of the fuel assembly inside the reactor. The analysis covered specific loads and displacements acting on the entire structure. The method used to solve this finite element analysis was a linear static simulation in order to perform the connection between a spacer grid cell and a guide thimble section. Hence, four models was evaluated, differing on the spot weld number in the spacer grid and guide thimble connection. The rotational stiffness results of each model were compared. The results acquired from four and eight spot weld were validated with physical test results. The behavior of the structure under the acting force/displacement and the related results of the analysis, mainly the stiffness, were satisfied. The results of this analysis were used to prove that the increasing spot welds number is an improvement in the dimensional stability when submitted to loads and displacements required on the fuel assembly design. This analysis aid to get more information of extreme importance such as, the pursuance to develop better manufacturing process and to improve the fuel assembly performance due to the increasing of the bum-up.展开更多
Classes are the basic modules in Object-Oriented (OO) software, which consist of attributes and methods. Thus, in OO environment, the cohesion is mainly about how tightly the attributes and methods of classes cohere w...Classes are the basic modules in Object-Oriented (OO) software, which consist of attributes and methods. Thus, in OO environment, the cohesion is mainly about how tightly the attributes and methods of classes cohere with each other. This letter discusses the relationships between attributes and attributes, attributes and methods, methods and methods of a class,and the properties of these relationships. Based on these properties, the letter proposes a new framework to measure the cohesion of a class. The approach overcomes the limitations of previous class cohesion measures, which consider only one or two of the three relationships in a class.展开更多
The issue of CCF （common cause failure） in digital I ＆ C （instrumentation and control） systems is of great interest because an increasing number of such systems are implemented in nuclear power plants. For the mi...The issue of CCF （common cause failure） in digital I ＆ C （instrumentation and control） systems is of great interest because an increasing number of such systems are implemented in nuclear power plants. For the mitigation of ATWS （anticipated transients without scram） as well as CCF within the PPS （plant protection system） and the ESF-CCS （engineered safety feature-component control system）, the ADPS （advanced diverse protection system） has been developed by KEPCO E ＆ C （KEPCO Engineering and Construction） Company for new nuclear units in Korea. As compared to the DPS （diverse protection system） design of APR1400, the ADPS has a diverse safety injection function considering a LBLOCA （large break loss of coolant accident） concurrent with the CCF of the PPS and ESF-CCS. Besides the function of SIAS （safety injection actuation signal） initiation, several CCF avoidance features, such as the changes of software design classification, communication methods, equipment platform, and man-machine interfaces, are introduced to enhance the reliability of the ADPS. In addition, the ADPS has recently incorporated four redundant channels with 2-out-of-4 voting logics to enhance its fault tolerant capability. Therefore, it is expected that the ADPS can provide an enhanced reliability regarding possible CCFs in the safety-grade digital I ＆ C systems as well as the ADPS itself.展开更多
文摘Changes in the regulatory requirements and the forthcoming Disinfectant/Disinfection By-Products （D/DBP） Rule will require that drinking water treatment facilities be operated to achieve maximum removals of particles and disinfectant tolerant microorganisms as well as natural organic matter （NOM）. For drinking water production, the use of membrane filtration processes such as microfiltration and ultrafiltration （MF/UF） alone to satisfy the turbidity, particle and microorganism removal a requirement of the surface water treatment regulation （SWTR） is not enough. MF/UF treatment processes can achieve only nominal （10 percent） removal of disinfection by-products （DBP） precursors （James, et al., 1995）. On the other hand, too fast fouling can make the filtration processes more difficult to carry on. To solve these problems, many authors have been interested in installing coagulation pretreatment before membrane filtration to improve membrane performance. However, previous studies reported conflicting results. Some supported the effectiveness of coagulation pretreatment, while others contended that coagulation aggravated membrane performance. This research aims to identify the effects of coagulation pretreatment on membrane filtration through a pilot study using PVDF membrane in combination with analyzing the rationale of coagulation. Another objective of this research was to evaluate the different impacts on membrane performance of using different membrane modules （the submerged module and pressured module）. The results showed that coagulation pretreatment greatly improved the membrane performance, extending the filtration time as well as reducing the permeated organic level, and that the submerged module is much more efficient than the pressured module.
文摘The present work aims to evaluate the increase in the number of spot welds in the 16 × 16 type fuel assembly structure that connects guide thimbles and spacer grids, in order to provide a proper joint for this connection. This new and improved process can provide more stiffness to the whole structure, since the number of spots raised from four to eight. A 3-D geometric model of a guide thimble section was generated in a CAD （computer aided design） program （SolidWorks）. After that, the geometric model was imported to a CAE （computer aided engineering） program （ANSYS Mechanical APDL, Release 14.0）, where the finite element model was built, considering the guide thimble geometry assembled with the spacer grid through the welded connections. Boundaries conditions were implemented in the model in order to simulate the correct physical behavior due to the operation of the fuel assembly inside the reactor. The analysis covered specific loads and displacements acting on the entire structure. The method used to solve this finite element analysis was a linear static simulation in order to perform the connection between a spacer grid cell and a guide thimble section. Hence, four models was evaluated, differing on the spot weld number in the spacer grid and guide thimble connection. The rotational stiffness results of each model were compared. The results acquired from four and eight spot weld were validated with physical test results. The behavior of the structure under the acting force/displacement and the related results of the analysis, mainly the stiffness, were satisfied. The results of this analysis were used to prove that the increasing spot welds number is an improvement in the dimensional stability when submitted to loads and displacements required on the fuel assembly design. This analysis aid to get more information of extreme importance such as, the pursuance to develop better manufacturing process and to improve the fuel assembly performance due to the increasing of the bum-up.
基金Supported in part by the National Natural Science Foundation of China(NSFC)(No.60073012),Natural Science Foundation of Jiangsu (BK2001004).
文摘Classes are the basic modules in Object-Oriented (OO) software, which consist of attributes and methods. Thus, in OO environment, the cohesion is mainly about how tightly the attributes and methods of classes cohere with each other. This letter discusses the relationships between attributes and attributes, attributes and methods, methods and methods of a class,and the properties of these relationships. Based on these properties, the letter proposes a new framework to measure the cohesion of a class. The approach overcomes the limitations of previous class cohesion measures, which consider only one or two of the three relationships in a class.
文摘The issue of CCF （common cause failure） in digital I ＆ C （instrumentation and control） systems is of great interest because an increasing number of such systems are implemented in nuclear power plants. For the mitigation of ATWS （anticipated transients without scram） as well as CCF within the PPS （plant protection system） and the ESF-CCS （engineered safety feature-component control system）, the ADPS （advanced diverse protection system） has been developed by KEPCO E ＆ C （KEPCO Engineering and Construction） Company for new nuclear units in Korea. As compared to the DPS （diverse protection system） design of APR1400, the ADPS has a diverse safety injection function considering a LBLOCA （large break loss of coolant accident） concurrent with the CCF of the PPS and ESF-CCS. Besides the function of SIAS （safety injection actuation signal） initiation, several CCF avoidance features, such as the changes of software design classification, communication methods, equipment platform, and man-machine interfaces, are introduced to enhance the reliability of the ADPS. In addition, the ADPS has recently incorporated four redundant channels with 2-out-of-4 voting logics to enhance its fault tolerant capability. Therefore, it is expected that the ADPS can provide an enhanced reliability regarding possible CCFs in the safety-grade digital I ＆ C systems as well as the ADPS itself.
