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
Because short pulse Nd:YAG laser of nanosecond pulse-width and high peak power has a unique capability to improve the mechanical properties of metal parts,a study on the development of high peak power short pulse from...Because short pulse Nd:YAG laser of nanosecond pulse-width and high peak power has a unique capability to improve the mechanical properties of metal parts,a study on the development of high peak power short pulse from Nd:YAG laser along with its peening application has been performed.The design scheme of laser and the characteristic of laser beam transmission are presented and discussed.A pulse energy of 25 J with 15 ns pulse-width and a maximum peak power of 1660 k W laser system which use one oscillation and eight amplifiers has been achieved.Laser beam has a max divergence angle of 0.03 mrad,a pulse-to-pulse pulse-width stability of±0.1 ns,and the pulse-to-pulse energy stability factors of less than±2.8%.A low value of divergence means an easier modification of a nearly hat-top laser beam intensity profile and an easier transmission of laser beam.To evaluate the performance of the laser system,several metal materials are processed.Laser peening quality and efficiency are analyzed by using an optical microscope,a transmission electron microscope,and an X-ray diffraction device.The processing results show that the performance of this laser system is excellent.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 Hi-Tech Research and Development Program of China("863"Project)(Grant No.2012AA041310)
文摘Because short pulse Nd:YAG laser of nanosecond pulse-width and high peak power has a unique capability to improve the mechanical properties of metal parts,a study on the development of high peak power short pulse from Nd:YAG laser along with its peening application has been performed.The design scheme of laser and the characteristic of laser beam transmission are presented and discussed.A pulse energy of 25 J with 15 ns pulse-width and a maximum peak power of 1660 k W laser system which use one oscillation and eight amplifiers has been achieved.Laser beam has a max divergence angle of 0.03 mrad,a pulse-to-pulse pulse-width stability of±0.1 ns,and the pulse-to-pulse energy stability factors of less than±2.8%.A low value of divergence means an easier modification of a nearly hat-top laser beam intensity profile and an easier transmission of laser beam.To evaluate the performance of the laser system,several metal materials are processed.Laser peening quality and efficiency are analyzed by using an optical microscope,a transmission electron microscope,and an X-ray diffraction device.The processing results show that the performance of this laser system is excellent.
