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
The northern coast of Java,Indonesia,frequently experiences coastal flooding,including in Semarang City.On May 23,2022,a severe coastal flood led to an embankment breach,primarily driven by atmospheric phenomena such ...The northern coast of Java,Indonesia,frequently experiences coastal flooding,including in Semarang City.On May 23,2022,a severe coastal flood led to an embankment breach,primarily driven by atmospheric phenomena such as the Boreal Summer Intraseasonal Oscillation(BSISO)which intensified wind speeds and significant wave height(SWH)in the Java Sea.This study investigates wave characteristics during the flooding event using simulations from the Simulating Wave Nearshore(SWAN)model to assess the influence of these atmospheric drivers.The results reveal distinct wave patterns,with wind speed and wave height increasing significantly from May 19 to May 25,2022.Wind speeds peaked at 10.3 m/s on May 20 and reached 6.5 m/s at the time of the embankment breach on May 23,while SWH reached a maximum of 0.75 m on May 22 and was 0.6 m during the breach.The BSISO 1 and BSISO 2 indices indicated active intraseasonal atmospheric conditions that corresponded with enhanced wave development.These findings provide new insights into the influence of BSISO on wave amplification and coastal flooding in the Java Sea.The study contributes to disaster mitigation and coastal management efforts by highlighting the importance of incorporating intraseasonal atmospheric variability,particularly BSISO,into flood prediction and adaptation strategies.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 Kemendikbudristek under the research program of Penelitian Fundamental Reguler(PFR)2024,Research Grand Contract 036/E5/PG.02.00.PL/2024.
文摘The northern coast of Java,Indonesia,frequently experiences coastal flooding,including in Semarang City.On May 23,2022,a severe coastal flood led to an embankment breach,primarily driven by atmospheric phenomena such as the Boreal Summer Intraseasonal Oscillation(BSISO)which intensified wind speeds and significant wave height(SWH)in the Java Sea.This study investigates wave characteristics during the flooding event using simulations from the Simulating Wave Nearshore(SWAN)model to assess the influence of these atmospheric drivers.The results reveal distinct wave patterns,with wind speed and wave height increasing significantly from May 19 to May 25,2022.Wind speeds peaked at 10.3 m/s on May 20 and reached 6.5 m/s at the time of the embankment breach on May 23,while SWH reached a maximum of 0.75 m on May 22 and was 0.6 m during the breach.The BSISO 1 and BSISO 2 indices indicated active intraseasonal atmospheric conditions that corresponded with enhanced wave development.These findings provide new insights into the influence of BSISO on wave amplification and coastal flooding in the Java Sea.The study contributes to disaster mitigation and coastal management efforts by highlighting the importance of incorporating intraseasonal atmospheric variability,particularly BSISO,into flood prediction and adaptation strategies.
