Magnetite (Fe<sub>3</sub>O<sub>4</sub>) crystals have been synthesized from the natural iron sands of Tegal Lenga Beach with HCl (37%) as a solvent. Tegal Lenga Beach is a stretch of beach loca...Magnetite (Fe<sub>3</sub>O<sub>4</sub>) crystals have been synthesized from the natural iron sands of Tegal Lenga Beach with HCl (37%) as a solvent. Tegal Lenga Beach is a stretch of beach located in Kalisada Village, Seririt District, Buleleng Regency, Bali Province, Indonesia. Iron sand samples were obtained by extracting local natural sand from Tegal Lenga Beach by magnetic separation method. The iron sand sample was ground with agate mortar for 15 hours, then washed and rinsed with deionized water (DI water). Furthermore, the fine powder sample of iron sand was dried on a hotplate at a temperature of 80˚C until all the water had evaporated. Eighty grams of fine iron sand powder dissolved in 200 mL HCl (37%) while stirring with a hot plate magnetic stirrer at a temperature of 100˚C with a rotating speed of 600 rpm for 30 minutes. This solution was filtered through Wattman filter paper No. 42;then the filtrate was dried using a hot plate at a temperature of 100˚C to form a crust. This crust is then ground in an agate mortar until it becomes a fine powder of iron sand. Furthermore, the iron sand fine powder filtrate sample was divided into four equal parts which were then calcined at temperatures of 300˚C, 400˚C, 450˚C, and 500˚C for 30 minutes, respectively. It was found that the fine powder of iron sand from the natural sand of the Tegal Lenga Beach consisted mostly of 84.26% metal oxide magnetite. The synthesized magnetite crystal has a tetrahedral structure with lattice parameters of a = b = (5.927 ± 0.0180) Åand c = (16.774 ± 0.0145) Å. Magnetite crystals have granular and lumpy grains with an average grain size of (94,560 ± 10,1397) μm. In relation to the values obtained from the hysteresis curve, namely the remanent magnetization of 9.6672 emu/gr, saturation magnetization of 45.3491 emu/gr, coercive magnetic field strength of 0.0242 T, and saturation magnetic field strength of 0, 2938 T, then this magnetite crystal is classified as a weak ferromagnetic material.展开更多
Urbanization in small-and medium-sized cities has often been overlooked in urban studies.Research on urbanization has predominantly focused on large metropolitan cities;however,urbanization in small-and medium-sized c...Urbanization in small-and medium-sized cities has often been overlooked in urban studies.Research on urbanization has predominantly focused on large metropolitan cities;however,urbanization in small-and medium-sized cities also contributes to the acceleration of urban sprawl.Urban growth boundary(UGB)is an ecological approach designed to limit urban development.This study aimedto analyze environmental protection priority zonesby combining ecological quality and sensitivity indices to identify the areas suitable for UGB implementation.Tegal City and its surrounding areas(including Tegal and Brebes regencies)of Indonesia were selected as the study area.The ecological quality index was calculated using the normalized difference vegetation index,humidity index,land surface temperature,and normalized difference bare soil index.These indices were subsequently subjected to principal component analysis(PCA)to extract orthogonal factors,which were summed to derive the final index value.In parallel,we mapped and evaluated ecological sensitivity based on spatial planning policies and regulations.The results revealed that ecological quality in Tegal and Brebes regencies was predominantly categorized as good and very good ecological quality,whereas TegalCity exhibited moderate and poor ecological quality.Additionally,over 45.00%of the area in Tegal and Brebes regencies demonstrated very high ecological sensitivity.Consequently,more than 50.00%of the area in Tegal and Brebes regencies,along with 27.00%of Tegal City,were classified as ecological constraint zone,making them potential regionsfor UGB development.The UGB is expected to curtail urban expansion,promote compact city planning,and preserve ecosystem services to achieve urban sustainability.This study implies that planningsmall-and medium-sized cities is important to prevent urban sprawl and maintain environmental health.Designing UGB to limit urban expansion should be enhanced by better knowledge about its ecological functions in supporting urban sustainability.展开更多
文摘Magnetite (Fe<sub>3</sub>O<sub>4</sub>) crystals have been synthesized from the natural iron sands of Tegal Lenga Beach with HCl (37%) as a solvent. Tegal Lenga Beach is a stretch of beach located in Kalisada Village, Seririt District, Buleleng Regency, Bali Province, Indonesia. Iron sand samples were obtained by extracting local natural sand from Tegal Lenga Beach by magnetic separation method. The iron sand sample was ground with agate mortar for 15 hours, then washed and rinsed with deionized water (DI water). Furthermore, the fine powder sample of iron sand was dried on a hotplate at a temperature of 80˚C until all the water had evaporated. Eighty grams of fine iron sand powder dissolved in 200 mL HCl (37%) while stirring with a hot plate magnetic stirrer at a temperature of 100˚C with a rotating speed of 600 rpm for 30 minutes. This solution was filtered through Wattman filter paper No. 42;then the filtrate was dried using a hot plate at a temperature of 100˚C to form a crust. This crust is then ground in an agate mortar until it becomes a fine powder of iron sand. Furthermore, the iron sand fine powder filtrate sample was divided into four equal parts which were then calcined at temperatures of 300˚C, 400˚C, 450˚C, and 500˚C for 30 minutes, respectively. It was found that the fine powder of iron sand from the natural sand of the Tegal Lenga Beach consisted mostly of 84.26% metal oxide magnetite. The synthesized magnetite crystal has a tetrahedral structure with lattice parameters of a = b = (5.927 ± 0.0180) Åand c = (16.774 ± 0.0145) Å. Magnetite crystals have granular and lumpy grains with an average grain size of (94,560 ± 10,1397) μm. In relation to the values obtained from the hysteresis curve, namely the remanent magnetization of 9.6672 emu/gr, saturation magnetization of 45.3491 emu/gr, coercive magnetic field strength of 0.0242 T, and saturation magnetic field strength of 0, 2938 T, then this magnetite crystal is classified as a weak ferromagnetic material.
基金funded by the Directorate of Research and Community Service, Ministry of Education, Culture, Research, and Technology, Indonesia (027/E5/PG.02.00.PL/2024)Bogor Agricultural University for their invaluable support and resources that made this research possibleDirectorate of Research and Community Service, Ministry of Education, Culture, Research, and Technology, Indonesia, for their financial and administrative support
文摘Urbanization in small-and medium-sized cities has often been overlooked in urban studies.Research on urbanization has predominantly focused on large metropolitan cities;however,urbanization in small-and medium-sized cities also contributes to the acceleration of urban sprawl.Urban growth boundary(UGB)is an ecological approach designed to limit urban development.This study aimedto analyze environmental protection priority zonesby combining ecological quality and sensitivity indices to identify the areas suitable for UGB implementation.Tegal City and its surrounding areas(including Tegal and Brebes regencies)of Indonesia were selected as the study area.The ecological quality index was calculated using the normalized difference vegetation index,humidity index,land surface temperature,and normalized difference bare soil index.These indices were subsequently subjected to principal component analysis(PCA)to extract orthogonal factors,which were summed to derive the final index value.In parallel,we mapped and evaluated ecological sensitivity based on spatial planning policies and regulations.The results revealed that ecological quality in Tegal and Brebes regencies was predominantly categorized as good and very good ecological quality,whereas TegalCity exhibited moderate and poor ecological quality.Additionally,over 45.00%of the area in Tegal and Brebes regencies demonstrated very high ecological sensitivity.Consequently,more than 50.00%of the area in Tegal and Brebes regencies,along with 27.00%of Tegal City,were classified as ecological constraint zone,making them potential regionsfor UGB development.The UGB is expected to curtail urban expansion,promote compact city planning,and preserve ecosystem services to achieve urban sustainability.This study implies that planningsmall-and medium-sized cities is important to prevent urban sprawl and maintain environmental health.Designing UGB to limit urban expansion should be enhanced by better knowledge about its ecological functions in supporting urban sustainability.
