The article discusses plot size standards applied in the government sites-and-services projects in Khartoum and probes into the possible alternative ways of re-establishing solid grounds for those standards. The parti...The article discusses plot size standards applied in the government sites-and-services projects in Khartoum and probes into the possible alternative ways of re-establishing solid grounds for those standards. The particular issue of plot size is a crucial factor in the whole housing policy as it directly affects the urban land use and consumption and extends its influence far into sustainability and affordability issues and the whole housing policy and supply process. The article, analysing the applied standards, argues that plot subdivision can substantially contribute to providing more access of housing to the low-income groups. Large plot sizes can be subdivided driven by the need to realize security of tenure, doubling the owner-occupier housing stock which is the base issue of self-help housing, increases housing finance, provides variety of housing choices and behind all it conforms to the legacy principles and some cultural attributes of the local community. The article underlined existence of a cumbersome regulatory system, subdivision procedures and development controls which need to be reformed.展开更多
In an object-based storage system,a novel scheme named EAP(extending attributes page) is presented to enhance the metadata reliability of the system by adding the user object file information attributes page for each ...In an object-based storage system,a novel scheme named EAP(extending attributes page) is presented to enhance the metadata reliability of the system by adding the user object file information attributes page for each user object and storing the file-related attributes of each user object in object-based storage devices.The EAP scheme requires no additional hardware equipments compared to a general method which uses backup metadata servers to improve the metadata reliability.Leveraging a Markov chain,this paper compares the metadata reliability of the system using the EAP scheme with that using only metadata servers to offer the file metadata service.Our results demonstrate that the EAP scheme can dramatically enhance the reliability of storage system metadata.展开更多
It is well known that static seals are usually designed to be used once. In this paper, we discuss the reusability of a type of static seal called the spring energized metal C ring, which is required to be reused 4-5 ...It is well known that static seals are usually designed to be used once. In this paper, we discuss the reusability of a type of static seal called the spring energized metal C ring, which is required to be reused 4-5 times without maintenance during the lifetime of the pump. A theoretical analysis based on the nonlinear finite element method and an experimental investigation of the reusability of the C ring are carried out. The effects of the elastic modulus of the ring material, the ring wall thickness, the amount of assembly interference between the spring and the C ring, the operating temperature and the compression ratio are discussed. The parameter S, which denotes the reaction force difference percentage, is determined to measure the reusability of the C ring. The results show that the ring wall thickness plays an important role in the reusability. Although the normal force of a thick wall decreases after the ring is reused eight times, the value is still higher than the first normal force of a thin wall. In contrast, the elastic modulus of the material has the lowest impact. Here, a pre-compression ratio of 18.2% not only produces a larger first normal force but also leads to a smaller reduction in the normal force when the ring is reused. A simulated experiment is carried out to investigate the influence of the coating of the C ring on its reusability. The results show that when plastic deformation occurs on the contact surface, the contact state of the C ring coating becomes a major factor that affects the seal performance. Aging treatment at high temperatures （250℃） reduces gized metal C ring, which leads to the deterioration in the reusability the binding force of the silver coating on the spring ener of the ring.展开更多
文摘The article discusses plot size standards applied in the government sites-and-services projects in Khartoum and probes into the possible alternative ways of re-establishing solid grounds for those standards. The particular issue of plot size is a crucial factor in the whole housing policy as it directly affects the urban land use and consumption and extends its influence far into sustainability and affordability issues and the whole housing policy and supply process. The article, analysing the applied standards, argues that plot subdivision can substantially contribute to providing more access of housing to the low-income groups. Large plot sizes can be subdivided driven by the need to realize security of tenure, doubling the owner-occupier housing stock which is the base issue of self-help housing, increases housing finance, provides variety of housing choices and behind all it conforms to the legacy principles and some cultural attributes of the local community. The article underlined existence of a cumbersome regulatory system, subdivision procedures and development controls which need to be reformed.
基金supported by the National Natural Science Foundation of China (No.60873028)the National Basic Research Program (973) of China (No.2004CB318201)+1 种基金the Program for New Century Excellent Talents in University (No.NCET-04-0693)the Innovational Group Project (No.IRT0725),China
文摘In an object-based storage system,a novel scheme named EAP(extending attributes page) is presented to enhance the metadata reliability of the system by adding the user object file information attributes page for each user object and storing the file-related attributes of each user object in object-based storage devices.The EAP scheme requires no additional hardware equipments compared to a general method which uses backup metadata servers to improve the metadata reliability.Leveraging a Markov chain,this paper compares the metadata reliability of the system using the EAP scheme with that using only metadata servers to offer the file metadata service.Our results demonstrate that the EAP scheme can dramatically enhance the reliability of storage system metadata.
基金supported by the National Key S&T Special Project(Grant No.2012ZX06901-022)
文摘It is well known that static seals are usually designed to be used once. In this paper, we discuss the reusability of a type of static seal called the spring energized metal C ring, which is required to be reused 4-5 times without maintenance during the lifetime of the pump. A theoretical analysis based on the nonlinear finite element method and an experimental investigation of the reusability of the C ring are carried out. The effects of the elastic modulus of the ring material, the ring wall thickness, the amount of assembly interference between the spring and the C ring, the operating temperature and the compression ratio are discussed. The parameter S, which denotes the reaction force difference percentage, is determined to measure the reusability of the C ring. The results show that the ring wall thickness plays an important role in the reusability. Although the normal force of a thick wall decreases after the ring is reused eight times, the value is still higher than the first normal force of a thin wall. In contrast, the elastic modulus of the material has the lowest impact. Here, a pre-compression ratio of 18.2% not only produces a larger first normal force but also leads to a smaller reduction in the normal force when the ring is reused. A simulated experiment is carried out to investigate the influence of the coating of the C ring on its reusability. The results show that when plastic deformation occurs on the contact surface, the contact state of the C ring coating becomes a major factor that affects the seal performance. Aging treatment at high temperatures （250℃） reduces gized metal C ring, which leads to the deterioration in the reusability the binding force of the silver coating on the spring ener of the ring.
