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"In this study, modeling of the crossing point temperature (CPT) phenomenon in the low-temperature oxidation of coal was carried out using COMSOL Multiphysics®. Low-temperature oxidation can lead to spontaneous combustion of coal stockpiles. The CPT phenomenon was modeled with the kinetics data obtained from a prior laboratory experimental study. The coupling of the heat-transfer phenomenon through conduction and convection determined the thermal evolution model. In this case, coal received the initial heat of the oven temperature increases. As the coal temperature rose, the heat generated from oxidation was released into the environment via conduction and convection. Meanwhile, oxidation products and oxygen were transferred by convection and diffusion. The effects of moisture and the humidity were not considered. The outcomes of modeling were validated through comparison with the results of experimental tests, and the modeling result agreed well with the experiment tests, with temperature deviations of about 0.9%. The effects of airflow rate, oxygen concentration, porosity, and the initial temperature on low-temperature coal oxidation were also examined."

"In this study, modeling of the crossing point temperature (CPT) phenomenon in the low-temperature oxidation of coal was carried out using COMSOL Multiphysics®. Low-temperature oxidation can lead to spontaneous combustion of coal stockpiles. The CPT phenomenon was modeled with the kinetics data obtained from a prior laboratory experimental study. The coupling of the heat-transfer phenomenon through conduction and convection determined the thermal evolution model. In this case, coal received the initial heat of the oven temperature increases. As the coal temperature rose, the heat generated from oxidation was released into the environment via conduction and convection. Meanwhile, oxidation products and oxygen were transferred by convection and diffusion. The effects of moisture and the humidity were not considered. The outcomes of modeling were validated through comparison with the results of experimental tests, and the modeling result agreed well with the experiment tests, with temperature deviations of about 0.9%. The effects of airflow rate, oxygen concentration, porosity, and the initial temperature on low-temperature coal oxidation were also examined."

"Salah satu masalah paling utama bumi khususnya di perkotaan adalah meningkatnya suhu permukaan karena alih fungsi lahan vegetasi menjadi non-vegetasi. Terus berkembangnya Kota Semarang menjadi kota perdagangan dan kota jasa pariwisata menyebabkan peningkatan luas lahan terbangun dan penurunan luas area hijau. Penelitian ini bertujuan untuk menganalisis perubahan tutupan lahan di Kota Semarang tahun 2008-2018 menganalisis variasi Land Surface Temperature di Kota Semarang tahun 2008-2018 dan menganalisis korelasi antara Land Surface Temperature dengan tutupan lahan, Normalized Difference Vegetation Index, Normalized Difference Building Index dan Normalized Difference Water Index Kota Semarang tahun 2000-2018. Data yang digunakan adalah citra Landsat 5 dan Landsat 8 pada bulan kering. Metode pada penelitian ini berupa Supervised Classification, LST, NDVI NDBI dan NDWI. Uji akurasi data tutupan lahan menggunakan Producer Accuracy, User Accuracy, Overall Accuracy dan Kappa Coefficient. Survei lapang dilakukan untuk melakukan validasi data tutupan lahan dan pengukuran suhu. Hasil penelitian menunjukan bahwa tutupan lahan Kota Semarang dari tahun 2008, 2011, 2015 dan 2018 terus mengalami perubahan luas. Luas area terbangun di Kota Semarang terus meningkat diikuti dengan penurunan pada kelas tutupan lahan lainnya. Secara umum, LST Kota Semarang dari tahun 2008 hingga 2018 terus mengalami kenaikan. NDVI dan NDWI berkorelasi negatif dengan LST Kota Semarang sedangkan NDBI berkorelasi positif dengan LST Kota Semarang.

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One of the most important problems of the earth, especially in urban areas, is rising surface temperatures due to conversion of vegetation land to non-vegetation. The continued development of the City of Semarang as a city of trade and tourism services city led to an increase in the area of ​​built land and a decrease in the area of ​​green areas.

This study aims to analyze changes in land cover in the city of Semarang in 2008-2018 to analyze variations in Land Surface Temperature in the City of Semarang in 2008-2018 and analyze the correlation between Land Surface Temperature and land cover, Normalized Difference Vegetation Index, Normalized Difference Building Index and Normalized Difference Semarang City Water Index 2000-2018. The data used are Landsat 5 and Landsat 8 images on dry months.

The method in this research is Supervised Classification, LST, NDVI NDBI and NDWI. Test the accuracy of land cover data using Producer Accuracy, User Accuracy, Overall Accuracy and Kappa Coefficient. A field survey was conducted to validate land cover data and temperature measurements.

The results showed that the Semarang City land cover from 2008, 2011, 2015 and 2018 continued to experience extensive changes. The area built up in the city of Semarang continues to increase followed by a decrease in other land cover classes. In general, Semarang City LST from 2008 to 2018 continues to increase. NDVI and NDWI are negatively correlated with LST Semarang while NDBI is positively correlated with LST Semarang."

"Wilayah eksplorasi panas bumi Hu’u Daha merupakan salah satu wilayah yang dianggap potensial untuk dijadikan sumber energi alternatif berupa energi panas bumi. Dalam penelitian ini dilakukan korelasi hasil pengolahan data gravitasi dengan data Land Surface Temperature (LST) untuk memperkirakan adanya sumber panas bumi, di mana titik-titik dengan nilai gravitasi tinggi kemungkinan besar merupakan lokasi adanya sumber panas bumi dan memperkirakan suhu reservoir panas bumi di bawah permukaan tanah. Dalam pengolahan data tersebut, dilakukan tahapan filtering First Horizontal Derivative (FHD) dan Second Vertical Derivative (SVD) yang menunjukkan adanya 6 struktur geologi pada daerah Hu’u Daha dengan arah patahan barat laut-tenggara, barat-timur, hingga timur laut-barat daya yang mengontrol sistem panas bumi daerah penelitian yang ditandai oleh garis berwarna hitam. Kemudian dilakukan analisis patahan dan analisis 3D inversi yang dimana dugaan keterdapatan lapisan reservoir berupa batuan lava dan breksi berkomposisi andesit dan basalt serta sisipan batuan tufa dengan rerata kedalaman 633-1500 m dengan nilai densitas 3.4-3.33 gr/cm3 yang dilingkupi oleh lapisan cap rock berupa batuan lava hasil erupsi dengan kedalaman rata-rata 0-633 m dengan nilai densitas 3.51-3.44 gr/cm3, serta terdapat patahan-patahan yang mengontrol sistem panas bumi berdasarkan korelasi FHD dan SVD.

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The exploration area of Hu'u Daha geothermal field is considered to be a potential source of alternative energy in the form of geothermal energy. In this study, the correlation between gravity data and Land Surface Temperature (LST) was conducted to estimate the presence of geothermal sources. Points with high gravity values are likely locations of geothermal sources, and the temperature of the geothermal reservoir beneath the ground surface was estimated. The data processing involved the use of First Horizontal Derivative (FHD) and Second Vertical Derivative (SVD) filtering, which revealed the presence of six geological structures in the Hu'u Daha area, characterized by fault lines in the northwest-southeast, west-east, and northeast-southwest directions, controlling the geothermal system. Subsequently, fault analysis and 3D inversion analysis were performed, indicating the suspected presence of a reservoir layer consisting of andesite and basalt rock, as well as tufa rock, at an average depth of 633-1500 m with a density value of 3.4-3.33 g/cm3. This layer is covered by a cap rock layer of erupted lava rock at an average depth of 0-633 m with a density value of 3.51-3.44 g/cm3. The analysis also identified faults controlling the geothermal system based on the correlation of FHD and SVD."

"An investigation to structural and wear behaviour of nitrided AISI 316 L stainless steel resulting from low temperature fluidized bed nitriding has been made in the present work It was found that the wear resistance of nitrided specimens was related to the formation of a preetpitation-free hardened layer on the austenitic surface. In the present laboratory experiments, the precipitation-free or S phase layer with a surface hardness of ~1350 H Va 5 was produced at a nitriding condition of 450'C for 6h. The formation of this S phase layer significantly improved wear resistance of the stainless steel. Wear track observation by SEM revealed that the specimens without formation of S phase layer produced heavy scars due to tearing and local plastic deformation. The present work also suggests that fluidized bed heat treatment furnace can be utilised for nitriding the austenitic stainless steels at low temperatures below 5 00 ?C to produce S' phase nitrdid layer without losing the stainless feature of this material."

"This report is focused on the linear region of I-V characteristics of nanoscale highly-doped p-i-n diodes fabricated within ultrathin silicon-on-insulator (SOI) structures with an intrinsic layer length of 200 nm and 700 nm under a forward bias at a temperature range from 50 K to 250 K. The doping concentrations of Boron and Phosphorus in SOI p-i-n diodes are high, 1×1020 cm-3 and 2×1020 cm-3, respectively. The linearity of I-V characteristics of the p-i-n diodes under a certain forward bias voltage range and temperature range from 50 K to 250 K indicate these devices are suitable for low temperature sensing purposes. We conclude that highly-doped p-i-n diodes produce a higher current as the temperature decreases under a certain bias voltage range. Nanoscale diodes with longer and wider intrinsic layers generate higher currents under a certain range of bias voltage and low temperature measurements."

"Growth response of five clonal cultues of alexandrium obtained from tropical and temperate waters were examined experiments were carried out in eighteen variable temperature-salinity conditions (temperatures of 15 oC,-20oC and 25oC;salinities between 5 to 30 psu) under constant illumination of 150 kurang lebih10.0 umol m2s1 at 15:9 light:dark photo-cycle...."

"Latar belakang: Hidroksiapatit merupakan salah satu bahan alloplast yang banyak digunakan di bidang kedokteran gigi. Komposisi hidroksiapatit sama dengan komposisi anorganik tulang dan gigi manusia sehingga bersifat biokompatibel dan bioaktif. Selain itu, hidroksiapatit juga bersifat osteokonduktif. Salah satu metode pembuatan hidroksiapatit yaitu metode disolusi-presipitasi dalam kondisi hidrotermal. Pembuatan blok hidroksiapatit dengan metode disolusi-presipitasi pada suhu 100°C selama 48 jam masih menghasilkan fasa lain selain hidroksiapatit, yaitu dicalcium phosphate anhydrous (DCPA). Fasa DCPA dan/atau fasa DCPD (dicalcium phosphate dehydrate) dapat terbentuk dalam pH asam. Sedangkan, hidroksiapatit dapat terbentuk pada pH basa. Oleh karena itu, pH dapat dijadikan indikator secara tidak langsung mengenai hasil fasa yang terbentuk. Gipsum dipilih sebagai prekursor karena mengandung ion kalsium (Ca2+). Sedangkan, larutan Na3PO4 digunakan karena mengandung ion fosfat (PO43-), bersifat tidak toksik, dan memiliki pH basa. Tujuan: Penelitian ini bertujuan untuk mengetahui pengaruh perbedaan suhu terhadap perubahan pH larutan Na3PO4 dalam pembuatan blok hidroksiapatit dari blok gipsum.Metode Penelitian: Penelitian ini menggunakan blok gipsum dan larutan Na3PO4 sebagai prekursor untuk membuat blok hidroksiapatit. Spesimen yang digunakan berupa 30 mL larutan 1 mol/L Na3PO4 sebanyak dua beaker glass larutan. Sebelum dilakukan perendaman, pH larutan diukur terlebih dahulu untuk mengetahui pH awal larutan 1 mol/L Na3PO4. Lima belas blok gipsum direndam dalam 30 mL larutan 1 mol/L Na3PO4 dengan suhu yang berbeda yaitu 100°C, 140°C, dan 180°C pada kondisi hidrotermal selama 48 jam. Setelah perendaman, blok dan larutan 1 mol/L Na3PO4 dipisahkan. Kemudian, pH larutan 1 mol/L Na3PO4 diukur kembali menggunakan pH meter Eutech Instruments pH 700 untuk mendapatkan pH larutan 1 mol/L Na3PO4 setelah digunakan untuk perendaman selama 48 jam. Hasil: Nilai pH larutan 1 mol/L Na3PO4 sebelum digunakan untuk perendaman yaitu 13,04. Sedangkan, nilai pH larutan 1 mol/L Na3PO4 setelah digunakan untuk perendaman pada suhu 100°C, 140°C, dan 180°C berturut-turut yaitu 12,72; 12,67; dan 12,30. Kesimpulan: Peningkatan suhu yang digunakan menyebabkan penurunan pH larutan 1 mol/L Na3PO4. Namun, pH akhir larutan masih cukup basa untuk hidroksiapatit terbentuk. Namun, penelitian lebih lanjut masih perlu dilakukan mengenai pengukuran pH larutan Na3PO4 dengan sampel yang lebih banyak.

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Background: Hydroxyapatite is one of the alloplastic materials that is widely used in dentistry. The composition of hydroxyapatite is similar with the inorganic composition of human bone so that it is biocompatible and bioactive. Besides, hydroxyapatite is also osteoconductive. One of the fabrication methods of hydroxyapatite is the dissolution-precipitation method under hydrothermal conditions. The fabrication of hydroxyapatite block with the dissolution-precipitation method at 100°C for 48 hours still produced other phase except hydroxyapatite, specifically dicalcium phosphate anhydrous (DCPA). DCPA and/or dicalcium phosphate dehydrate (DCPD) phase can be obtained if the pH is acidic. Meanwhile, hydroxyapatite can be fabricated on the alkaline pH condition. Therefore, the pH value can be the indirect indicator to predict the phase product. Gypsum was chosen as a precursor because it has calcium ions (Ca2+). Na3PO4 solution was used because it contained phosphate ions (PO43+), non-toxic, and has an alkaline pH value.

Objective: This study aimed to determine the effect of temperature differences on changes of the pH value of Na3PO4 solution in the fabrication of hydroxyapatite block from gypsum block.

Methods: This study used gypsum block and Na3PO4 solution as precursors to fabricate hydroxyapatite block. The specimens of this study were two beaker glasses of 30 mL of 1 mol/L Na3PO4 solution. Before the immersion, the pH value of the solution was measured first to determine the initial pH value of 1 mol/L Na3PO4 solution. Fifteen specimens of gypsum blocks were immersed in 30 mL of 1 mol/L Na3PO4 solution with different temperatures specifically 100°C, 140°C, and 180°C under the hydrothermal condition for 48 hours. After the immersion, the blocks and the 1 mol/L Na3PO4 solution were separated. Then, the pH value of 1 mol/L Na3PO4 solution was measured using Eutech Instruments pH 700 pH meter to obtain the pH of 1 mol/L Na3PO4 solution after being used for immersion for 48 hours.

Results: The pH value of 1 mol/L Na3PO4 solution before being used for the immersion was 13,04. Meanwhile, the pH value of 1 mol/L Na3PO4 solution after being used for the immersion at 100°C, 140°C, and 180°C respectively were 12.72, 12.67, and 12.30.

Conclusions: The increase in the temperature caused the derivation of the pH value of 1 mol/L Na3PO4 solution. Nevertheless, the final pH value was still alkaline enough for hydroxyapatite to be formed. However, further research still needs to be done to measure the pH value of the Na3PO4 solution with more samples."