Central RF frequency measurement of the HLS-Ⅱ storage ring

Central RF frequency is a key parameter of storage rings. This paper presents the measurement of central RF frequency of the HLS-Ⅱ storage ring with the sextupole modulation method. Firstly, the basis of central RF frequency measurement of the electron storage ring is briefly introduced. Then, the error sources and the optimized measurement method for the HLS-Ⅱ storage ring are discussed. The workflow of a self-compiled Matlab script used in central RF frequency measurement is also described. Finally, the results achieved by using two data processing methods to cross-check each other are shown. The measured value of the central RF frequency demonstrates that the circumference deviation of the HLS-Ⅱ storage ring is less than 1 mm.

A comparative study on four major cities in Northeastern Thailand using urban land density function

Urban land density is an important factor to understand how cities expand.An“Inverse S-shape Rule”was implemented for the first time to analyze urban land density in Northeastern Thailand using the four cities Khon Kaen,Udon Thani,Nakhon Phanom,and Nong Khai as study sites.Land density function was tested using different data classification techniques from previous studies.Each city was investigated over two different time periods between 2002 and 2015.Declining pattern characteristics of metropolitan area density outward from city centers can be quantified by fitting the parameters to urban land density functions.An inverse S-shape function was identified as the best data fit.The four selected cities showed conventional density variation for decline in urban land area from city centers to outlying areas.Overall trend indicated that cities became more compact over time since the density differences between the urban core and urban fringe were greater with increasing infilling growth within the urban boundary.All four cities increased in size over time;however,the increasing amount of built-up land in the surrounding rural areas did not follow the same trend in each case.Some functional parameters required careful interpretation because of the linear shape of the city as in the case of Nakhon Phanom.Using highly detailed urban data resulted in lower densities of urban areas compared to the conventional pixel-based classification,and this affected the overall shape of the inverse S-shape function.The fitted parameters and their changing trends indicated that the urban land density function was useful for understanding urban form and urban sprawl in Thailand.Results can be used to develop a specific framework for other cities with similar attributes in the future.