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  • Authors: Sudiro, T. (Toto); Wismogroho, A. S. (Agus); Sebayang, P. (Perdamean); Simanjuntak, T. (Theresya); +2 Authors

    EFFECTS OF CURING TEMPERATURE AND ATMOSPHERE ON THE PROPERTIES OF ISOTROPIC BONDED NdFeB MAGNETS. The purpose of this paper was to synthesize the isotropic bonded NdFeB magnets at varying curing temperature and atmosphere, and to clarify their properties. For the aforesaid objective, the NdFeB powder was mixed with polyacrylate binder (3wt%) and compacted by hydraulic pressure with a compressive pressure of 30 MPa. The specimens were then separately cured at 100, 150, 180 and 200oC for 1 h in air and vacuum. The effects of curing temperature in air and vacuum on the bulk density and magnetic properties of isotropic bonded NdFeB magnets were studied. The results indicated that the bulk density and fluxmagnet density of bonded NdFeB magnets decreased with increase in curing temperature. This seems to be due to the binder vaporization and oxidation of element of NdFeB magnet. The bulk density of specimens cured in air was higher than that in vacuum for all temperatures. On the contrary, the magnetic flux density showed the opposite behavior. The optimum magnetic properties were achieved at curing temperature of 100oC for 1 h in vacuum with Br = 6,61 kG, HCJ = 8,841 kOe, and BHmax = 9,01 MGOe.

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  • Authors: Werner, D. (Dietrich);

    The major pools and turnover rates of the global carbon (C) cycles are presented and compared to the human production of CO2 from the burning of fossil fuels (e.g. coal and oil) and geothermal fuels (natural gases), both categorized as non-renewable energy resources which in amount reaches around 6.5 Gigatons C per year. These pools that serve as C-holding stallions are in the atmosphere, the land plant biomass, the organic soils carbon, the ocean carbon and the lithosphere. In another related case, the present focus in the area of nitrogen fixation is discussed with data on world production of grain legumes compared to cereals production and nitrogen fertilizer use. The focus to understand the molecular biology of the legume-rhizobia symbiosis as a major contributor to nitrogen fixation is in the areas of signal exchange between host plants and rhizobia in the rhizophere including the nod factor signalling, the infection and nodule compartmentation and the soils stress factors affecting the symbiosis. The use of the Legume-Rhizobia symbiosis as a biotest system for soil contaminants includes data for cadmium, arsenate, atrazine, lindane, fluoranthene, phenantrene and acenaphthene and also results on the mechanism, why the symbiotic system is more sensitive than test systems with plant growth parameters.

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  • Authors: Lestiani, D. D. (D); Santoso, M. (M);

    Urbanization and industrial growth have deteriorated air quality and are major cause to air pollution. Air pollution through fine and ultra-fine particles is a serious threat to human health. The source of air pollution must be known quantitatively by elemental characterization, in order to design the appropriate air quality management. The suitable methods for analysis the airborne particulate matter such as nuclear analytical techniques are hardly needed to solve the air pollution problem. The objectives of this study are to apply the nuclear analytical techniques to airborne particulate samples collected in Bandung, to assess the accuracy and to ensure the reliable of analytical results through the comparison of instrumental neutron activation analysis (INAA) and particles induced X-ray emission (PIXE). Particle samples in the PM2.5 and PM2.5-10 ranges have been collected in Bandung twice a week for 24 hours using a Gent stacked filter unit. The result showed that generally there was a systematic difference between INAA and PIXE results, which the values obtained by PIXE were lower than values determined by INAA. INAA is generally more sensitive and reliable than PIXE for Na, Al, Cl, V, Mn, Fe, Br and I, therefore INAA data are preffered, while PIXE usually gives better precision than INAA for Mg, K, Ca, Ti and Zn. Nevertheless, both techniques provide reliable results and complement to each other. INAA is still a prospective method, while PIXE with the special capabilities is a promising tool that could contribute and complement the lack of NAA in determination of lead, sulphur and silicon. The combination of INAA and PIXE can advantageously be used in air pollution studies to extend the number of important elements measured as key elements in source apportionment. Received: 20 November 2010; Revised: 09 August 2011; Accepted: 15 August 2011

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  • Authors: Soehada, A. M. (Achmad); Sebayang, K. (Kerista); Sudiro, T. (Toto); Kurniawan, C. (Candra); +1 Authors

    EFFECTOFMn-Ti IONS DOPINGAND SINTERINGTEMPERATUREON PROPERTIESOF BARIUMHEXAFERRITE. Mn-Ti doped (0, 0.1, 0.4, 0.5, and 0.6 mole%-barium hexaferrite powders have been prepared from BaCO3, Fe2O3, TiO2 andMnO powder by mechanical alloying technique for 20 hours. The mixture powder were grinded and then dried at 100 °C for 24 hours, followed by calcined at 1,000 °C for 2 hours. The calcined powder was then crushed into 400 mesh (38 μm) in particle size. X-Ray Diffraction analysis was performed to determine the phase formed. The powder was mixed with 3 wt%Celuna WE -518 polymer, and compressed with applied force of 5 tons. The sintering process was done at temperatures of 1100 °C and 1150 °C for 2 hours. The microstructure of sintered samples was observed by Scanning Electron Microscope - Energy Dispersive X-Ray Spectroscopy (SEM-EDS). The magnetic properties and Reflection Loss (RL) was measured by permeagraph Magnet-Physik and Vector Network Analyzer (VNA), respectively. The results show that the remanance (Br) of samples are likely to decrease with increase in %mol of Mn-Ti and the optimum coercivity (HCJ) 4,42 kOe was achieved at 0,5 mole% Mn-Ti. The maximum reflection loss of -25,6 dB was obtained at 0,4mole%Mn-Ti with sintering temperature of 1100 °C for 2 hours. Accordingly, it can be potentially used for microwave absorption application.

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  • Authors: Ricky Dwi Septianto; Ferry Iskandar; Mikrajuddin Abdullah; Khairurrijal Khairurrijal; +1 Authors

    In this study, the effects of polystyrene (PS) latex addition on the particle morphology and the pore content of calcium oxide (CaO) were investigated. The CaO particles were prepared using an ultrasonic nebulizer-assisted spray-pyrolysis method with variation of the PS/Ca(NO3)2·4H2O mass ratio in the precursor. Good crystallinity of CaO was obtained at 825°C of synthesis temperature under 2 l/min of nitrogen gas flow, which was confirmed by Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). According to scanning electron microscope (SEM) characterization, the CaO particles synthesized with 0 and 25 wt% PS addition had an almost spherical shape with an average size of 1.58 and 1.48 µm, respectively. In addition, macropores were formed in the CaO particles prepared with 25 wt% PS addition that had an average pore diameter of 583.26 nm. Meanwhile, the CaO particles prepared with 75 wt% PS addition had a random shape and an average size of 1.41 µm. The mesopore content was investigated by Barret-Joyner-Halenda (BJH) analysis, which showed improvement of the pore size from 3.45 nm to 5.42 nm for 0 and 25 wt% PS addition, respectively, which is proportional to the pore volume, pore surface area, and the capacity of SO2 retention.

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  • Authors: Hanafi, N. H. (Nur); Hassim, M. H. (Mimi); Noor, Z. Z. (Zainura);

    Haze pollution is one of the major environmental issues caused by aerosols, having brought about a history of heavy smog pollution events like the London smog in 1952 and the Los Angeles smog in the 1960s. However, in Malaysia, haze events are attributed to forest and peat fires in Kalimantan and Southern Sumatra, Indonesia. The burned biomass basically contains concentrated particulate matters that are hazardous to health among susceptible population groups. Based on the extensive literature review conducted, the small number of available local studies on the health effects of air pollution in Malaysia conducted so far focused on air pollution sciences. In this paper, a comprehensive overview of studies done on the impacts of haze on health conditions among populations in Malaysia is presented. The result shows that the number of upper respiratory tract infection cases was directly proportional to the particulate matter concentration and Air Pollution Index value in Johor in the years 2014 and 2015. Particulate matteris the major contributor in the formation of heavy hazes and is more likely to initiate detrimental health effects compared to other inhalable particles due to their size, large area, and strong activity, making them more likely to carry harmful substances causing a higher number of infected patients with upper respiratory tract infections.

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  • Authors: Budiyono, Budiyono; Buchori, Luqman;

    Membrane technology has led to a new focus on water and wastewater treatment. This is due to severaldrawback of the conventional water treatment i.e release the toxic and carcinogenic materials. In thisresearch, the use Reverse Osmosis (RO) membrane for treating river and well water to obtain clean anddrinking water was studied. The variables studied were effect of pressure and operation time to themembrane flux. The pressure was varied from 1 to 7 bar and the operation time was varied from 15 to 60minutes. The content of Total Dissolved Solid (TDS) in the permeate product was analyzed. The resultsshown that the increase of pressure would increase the membrane flux and decrease TDS. The increaseof the operation time would decrease membrane flux and TDS. The reverse osmosis membrane wassuccessfully applied to treat the river and well water. The product fulfill national standard quality ofdrinking water by viewpoint of the TDS content

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  • Authors: Saptutyningsih, E. (Endah);

    The main purpose of this study is the calculation of implicit prices of the environmental level of air quality in Yogyakarta on the basis of housing property prices. By means of Geographical Information System, the housing property prices characterized from the area which have highest air pollution level in province of Yogyakarta. Carbon monoxide is used as the pollution variable. The methodological framework for estimation is based on a hedonic price model. This approach establishes a relationship between the price of a marketable good (e.g. housing) and the amenities and characteristics this good contains. Therefore, if variations in air pollution levels occur, then households would change their behavior in an economic way by offering more money for housing located in highly improved environmental areas. The hedonic regression results that the housing price decrease while increasing the level of air contamination such substance as carbon monoxide.

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  • Authors: Leyla, T. (Topal); Kirchner, C. N. (Carolina); Germer, W. (Wiebke); Zobel, M. (Marco); +1 Authors

    The effects of different temperatures (55, 65, 75 and 85 °C) and cathode gas compositions (O2, synthetic air, air and 90% synthetic air+10% CO2) on alkaline anion exchange membrane fuel cell (AAEMFC) were evaluated. Membrane electrode assemblies (MEA) were fabricated using commercial anion exchange membrane (AEM) in OH- form and Pt catalyst. Polarization curves and voltage responses during constant current were performed in order to describe the influences of temperature and gas composition on the AAEMFC performance. The experimental results showed that the fuel cell performance increases with elevating temperatures for all applied gas compositions. Highest power density of 34.7 mW cm-2 was achieved for pure O2 as cathode feed. A decrease to 20.3 mW cm-2 was observed when cathode gas composition was changed to synthetic air due to reduction of the O2 partial pressure. The presence of CO2 in atmospheric air applied to the cathode stream caused a further drop of the maximum power density to 15.2 mW cm-2 driven by neutralization of OH- ions with CO2.

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  • Authors: Sapiie, Benyamin; Rifiyanto, Arif;

    Cleats are natural fractures within coal seams. This paper presents the results of regional cleat mapping and characterization in relation to coalbed methane (CBM) exploration and development in the Barito Basin, South Kalimantan, Indonesia involving two major coal layers, namely the Late Eocene Tanjung Formation and Early to Middle Miocene Warukin Formation with thicknesses ranging from 2 to 50 m. The coal is classified as lignite to subbituminous with calorific values ranging from 6000-8000 Cal/gr with ash content 0.68-17.42%. We applied two methods of cleat measurement, i.e. scanline and window sampling using a 100 x 100 cm grid. More than 20,000 cleats were measured from 65 scanline and 37 window sampling locations. The results revealed that face and butt cleats are predominantly oriented in the WNW-ESE and NNE-SSW directions, respectively. The results showed that cleat density increases related to structural position such as fold hinge and fault zone. The formation of the cleats may be influenced by several geological processes, where the cleats, which form during coalification, are superimposed by later processes such as fluid pressure and tectonic stresses and are seemingly also affected by the composition of the coal.

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  • Authors: Sudiro, T. (Toto); Wismogroho, A. S. (Agus); Sebayang, P. (Perdamean); Simanjuntak, T. (Theresya); +2 Authors

    EFFECTS OF CURING TEMPERATURE AND ATMOSPHERE ON THE PROPERTIES OF ISOTROPIC BONDED NdFeB MAGNETS. The purpose of this paper was to synthesize the isotropic bonded NdFeB magnets at varying curing temperature and atmosphere, and to clarify their properties. For the aforesaid objective, the NdFeB powder was mixed with polyacrylate binder (3wt%) and compacted by hydraulic pressure with a compressive pressure of 30 MPa. The specimens were then separately cured at 100, 150, 180 and 200oC for 1 h in air and vacuum. The effects of curing temperature in air and vacuum on the bulk density and magnetic properties of isotropic bonded NdFeB magnets were studied. The results indicated that the bulk density and fluxmagnet density of bonded NdFeB magnets decreased with increase in curing temperature. This seems to be due to the binder vaporization and oxidation of element of NdFeB magnet. The bulk density of specimens cured in air was higher than that in vacuum for all temperatures. On the contrary, the magnetic flux density showed the opposite behavior. The optimum magnetic properties were achieved at curing temperature of 100oC for 1 h in vacuum with Br = 6,61 kG, HCJ = 8,841 kOe, and BHmax = 9,01 MGOe.

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  • Authors: Werner, D. (Dietrich);

    The major pools and turnover rates of the global carbon (C) cycles are presented and compared to the human production of CO2 from the burning of fossil fuels (e.g. coal and oil) and geothermal fuels (natural gases), both categorized as non-renewable energy resources which in amount reaches around 6.5 Gigatons C per year. These pools that serve as C-holding stallions are in the atmosphere, the land plant biomass, the organic soils carbon, the ocean carbon and the lithosphere. In another related case, the present focus in the area of nitrogen fixation is discussed with data on world production of grain legumes compared to cereals production and nitrogen fertilizer use. The focus to understand the molecular biology of the legume-rhizobia symbiosis as a major contributor to nitrogen fixation is in the areas of signal exchange between host plants and rhizobia in the rhizophere including the nod factor signalling, the infection and nodule compartmentation and the soils stress factors affecting the symbiosis. The use of the Legume-Rhizobia symbiosis as a biotest system for soil contaminants includes data for cadmium, arsenate, atrazine, lindane, fluoranthene, phenantrene and acenaphthene and also results on the mechanism, why the symbiotic system is more sensitive than test systems with plant growth parameters.

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  • Authors: Lestiani, D. D. (D); Santoso, M. (M);

    Urbanization and industrial growth have deteriorated air quality and are major cause to air pollution. Air pollution through fine and ultra-fine particles is a serious threat to human health. The source of air pollution must be known quantitatively by elemental characterization, in order to design the appropriate air quality management. The suitable methods for analysis the airborne particulate matter such as nuclear analytical techniques are hardly needed to solve the air pollution problem. The objectives of this study are to apply the nuclear analytical techniques to airborne particulate samples collected in Bandung, to assess the accuracy and to ensure the reliable of analytical results through the comparison of instrumental neutron activation analysis (INAA) and particles induced X-ray emission (PIXE). Particle samples in the PM2.5 and PM2.5-10 ranges have been collected in Bandung twice a week for 24 hours using a Gent stacked filter unit. The result showed that generally there was a systematic difference between INAA and PIXE results, which the values obtained by PIXE were lower than values determined by INAA. INAA is generally more sensitive and reliable than PIXE for Na, Al, Cl, V, Mn, Fe, Br and I, therefore INAA data are preffered, while PIXE usually gives better precision than INAA for Mg, K, Ca, Ti and Zn. Nevertheless, both techniques provide reliable results and complement to each other. INAA is still a prospective method, while PIXE with the special capabilities is a promising tool that could contribute and complement the lack of NAA in determination of lead, sulphur and silicon. The combination of INAA and PIXE can advantageously be used in air pollution studies to extend the number of important elements measured as key elements in source apportionment. Received: 20 November 2010; Revised: 09 August 2011; Accepted: 15 August 2011

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  • Authors: Soehada, A. M. (Achmad); Sebayang, K. (Kerista); Sudiro, T. (Toto); Kurniawan, C. (Candra); +1 Authors

    EFFECTOFMn-Ti IONS DOPINGAND SINTERINGTEMPERATUREON PROPERTIESOF BARIUMHEXAFERRITE. Mn-Ti doped (0, 0.1, 0.4, 0.5, and 0.6 mole%-barium hexaferrite powders have been prepared from BaCO3, Fe2O3, TiO2 andMnO powder by mechanical alloying technique for 20 hours. The mixture powder were grinded and then dried at 100 °C for 24 hours, followed by calcined at 1,000 °C for 2 hours. The calcined powder was then crushed into 400 mesh (38 μm) in particle size. X-Ray Diffraction analysis was performed to determine the phase formed. The powder was mixed with 3 wt%Celuna WE -518 polymer, and compressed with applied force of 5 tons. The sintering process was done at temperatures of 1100 °C and 1150 °C for 2 hours. The microstructure of sintered samples was observed by Scanning Electron Microscope - Energy Dispersive X-Ray Spectroscopy (SEM-EDS). The magnetic properties and Reflection Loss (RL) was measured by permeagraph Magnet-Physik and Vector Network Analyzer (VNA), respectively. The results show that the remanance (Br) of samples are likely to decrease with increase in %mol of Mn-Ti and the optimum coercivity (HCJ) 4,42 kOe was achieved at 0,5 mole% Mn-Ti. The maximum reflection loss of -25,6 dB was obtained at 0,4mole%Mn-Ti with sintering temperature of 1100 °C for 2 hours. Accordingly, it can be potentially used for microwave absorption application.

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  • Authors: Ricky Dwi Septianto; Ferry Iskandar; Mikrajuddin Abdullah; Khairurrijal Khairurrijal; +1 Authors

    In this study, the effects of polystyrene (PS) latex addition on the particle morphology and the pore content of calcium oxide (CaO) were investigated. The CaO particles were prepared using an ultrasonic nebulizer-assisted spray-pyrolysis method with variation of the PS/Ca(NO3)2·4H2O mass ratio in the precursor. Good crystallinity of CaO was obtained at 825°C of synthesis temperature under 2 l/min of nitrogen gas flow, which was confirmed by Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). According to scanning electron microscope (SEM) characterization, the CaO particles synthesized with 0 and 25 wt% PS addition had an almost spherical shape with an average size of 1.58 and 1.48 µm, respectively. In addition, macropores were formed in the CaO particles prepared with 25 wt% PS addition that had an average pore diameter of 583.26 nm. Meanwhile, the CaO particles prepared with 75 wt% PS addition had a random shape and an average size of 1.41 µm. The mesopore content was investigated by Barret-Joyner-Halenda (BJH) analysis, which showed improvement of the pore size from 3.45 nm to 5.42 nm for 0 and 25 wt% PS addition, respectively, which is proportional to the pore volume, pore surface area, and the capacity of SO2 retention.

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  • Authors: Hanafi, N. H. (Nur); Hassim, M. H. (Mimi); Noor, Z. Z. (Zainura);

    Haze pollution is one of the major environmental issues caused by aerosols, having brought about a history of heavy smog pollution events like the London smog in 1952 and the Los Angeles smog in the 1960s. However, in Malaysia, haze events are attributed to forest and peat fires in Kalimantan and Southern Sumatra, Indonesia. The burned biomass basically contains concentrated particulate matters that are hazardous to health among susceptible population groups. Based on the extensive literature review conducted, the small number of available local studies on the health effects of air pollution in Malaysia conducted so far focused on air pollution sciences. In this paper, a comprehensive overview of studies done on the impacts of haze on health conditions among populations in Malaysia is presented. The result shows that the number of upper respiratory tract infection cases was directly proportional to the particulate matter concentration and Air Pollution Index value in Johor in the years 2014 and 2015. Particulate matteris the major contributor in the formation of heavy hazes and is more likely to initiate detrimental health effects compared to other inhalable particles due to their size, large area, and strong activity, making them more likely to carry harmful substances causing a higher number of infected patients with upper respiratory tract infections.

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  • Authors: Budiyono, Budiyono; Buchori, Luqman;

    Membrane technology has led to a new focus on water and wastewater treatment. This is due to severaldrawback of the conventional water treatment i.e release the toxic and carcinogenic materials. In thisresearch, the use Reverse Osmosis (RO) membrane for treating river and well water to obtain clean anddrinking water was studied. The variables studied were effect of pressure and operation time to themembrane flux. The pressure was varied from 1 to 7 bar and the operation time was varied from 15 to 60minutes. The content of Total Dissolved Solid (TDS) in the permeate product was analyzed. The resultsshown that the increase of pressure would increase the membrane flux and decrease TDS. The increaseof the operation time would decrease membrane flux and TDS. The reverse osmosis membrane wassuccessfully applied to treat the river and well water. The product fulfill national standard quality ofdrinking water by viewpoint of the TDS content

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  • Authors: Saptutyningsih, E. (Endah);

    The main purpose of this study is the calculation of implicit prices of the environmental level of air quality in Yogyakarta on the basis of housing property prices. By means of Geographical Information System, the housing property prices characterized from the area which have highest air pollution level in province of Yogyakarta. Carbon monoxide is used as the pollution variable. The methodological framework for estimation is based on a hedonic price model. This approach establishes a relationship between the price of a marketable good (e.g. housing) and the amenities and characteristics this good contains. Therefore, if variations in air pollution levels occur, then households would change their behavior in an economic way by offering more money for housing located in highly improved environmental areas. The hedonic regression results that the housing price decrease while increasing the level of air contamination such substance as carbon monoxide.

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  • Authors: Leyla, T. (Topal); Kirchner, C. N. (Carolina); Germer, W. (Wiebke); Zobel, M. (Marco); +1 Authors

    The effects of different temperatures (55, 65, 75 and 85 °C) and cathode gas compositions (O2, synthetic air, air and 90% synthetic air+10% CO2) on alkaline anion exchange membrane fuel cell (AAEMFC) were evaluated. Membrane electrode assemblies (MEA) were fabricated using commercial anion exchange membrane (AEM) in OH- form and Pt catalyst. Polarization curves and voltage responses during constant current were performed in order to describe the influences of temperature and gas composition on the AAEMFC performance. The experimental results showed that the fuel cell performance increases with elevating temperatures for all applied gas compositions. Highest power density of 34.7 mW cm-2 was achieved for pure O2 as cathode feed. A decrease to 20.3 mW cm-2 was observed when cathode gas composition was changed to synthetic air due to reduction of the O2 partial pressure. The presence of CO2 in atmospheric air applied to the cathode stream caused a further drop of the maximum power density to 15.2 mW cm-2 driven by neutralization of OH- ions with CO2.

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  • Authors: Sapiie, Benyamin; Rifiyanto, Arif;

    Cleats are natural fractures within coal seams. This paper presents the results of regional cleat mapping and characterization in relation to coalbed methane (CBM) exploration and development in the Barito Basin, South Kalimantan, Indonesia involving two major coal layers, namely the Late Eocene Tanjung Formation and Early to Middle Miocene Warukin Formation with thicknesses ranging from 2 to 50 m. The coal is classified as lignite to subbituminous with calorific values ranging from 6000-8000 Cal/gr with ash content 0.68-17.42%. We applied two methods of cleat measurement, i.e. scanline and window sampling using a 100 x 100 cm grid. More than 20,000 cleats were measured from 65 scanline and 37 window sampling locations. The results revealed that face and butt cleats are predominantly oriented in the WNW-ESE and NNE-SSW directions, respectively. The results showed that cleat density increases related to structural position such as fold hinge and fault zone. The formation of the cleats may be influenced by several geological processes, where the cleats, which form during coalification, are superimposed by later processes such as fluid pressure and tectonic stresses and are seemingly also affected by the composition of the coal.

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