Penelitian ini menyelidiki karakteristik komposit epoxy-serat bambu yang berkatian dengan sifat k... more Penelitian ini menyelidiki karakteristik komposit epoxy-serat bambu yang berkatian dengan sifat kekakuannya (modulus elastisitas komposit dengan pengujian tarik, pergeseran beam dalam arah sumbu Y pada berbagai titik dan dalam arah sumbu X sepanjang beam dengan menggunakan metode elemen hingga, penguatan yang ditimbulkan oleh serat bambu). Komposit ini memiliki ciri unisotropic. Serat bambu disusun dengan arah 0 o , 30 o , 45 o , 60 o dan 90 o menjadi bentuk beam sepanjang 300 mm. Hasil penelitian menunjukkan kontribusi serat arah 30 o paling besar dalam penguatan modulus elastisitas komposit sebesar 993 N/mm 2 dan defleksi terkecil sebesar 4,55 mm.
Objective: The purpose of this study was to evaluate the effect of herbal alternatives, extract o... more Objective: The purpose of this study was to evaluate the effect of herbal alternatives, extract of sidaguri (sida rhombifolia) combine with extract of jatropha sap (jatropha curcas) application on microhardness and morphology of tooth surface. Material and Methods: Twelve upper first premolar teeth were used in this study, prepared to Class I box cavities, and were then allocated into 4 groups (n=3). Group 1-3 were treated groups, applied with combined extracts of a small dose (5 mg), medium dose (25 mg), and high dose (50 mg), while group 4 was the control group. The cavities were restored with composite resin, immersed in artificial saliva, and stored at room temperature for 14 days. The fillings and extracts were removed and cleaned under running tap water. The teeth were cut in a vertical direction towards the apex, sectioned into 1 mm thickness, and evaluated using Laser Scanning Microscope (LSM), then were examined for microhardness test. Results: All treated groups showed significantly lower microhardness than the control group. Tooth porosity was observed, and its extensiveness was affected by doses of extracts. Conclusion: The application of herbal alternatives (extract of sidaguri and jatropha) lowered the microhardness of tooth structure and caused tooth porosities.
Aluminium matrix composite reinforced Carbon nanoTubes are widely developed because it can increa... more Aluminium matrix composite reinforced Carbon nanoTubes are widely developed because it can increase mechanical strength without reducing its ductility. One of the AMC / CNT manufacturing processes is through the stir casting method. The challenge of the Al / CNT manufacturing process is the occurrence of agglomeration and CNT not homogeneous so that the right casting parameters are needed to obtain optimal results. The purpose of this study was to analyse the effect of pouring temperature on the mechanical strength and microstructure of AA6061 by adding Carbon Nanotube (CNT) through the stir casting method. The CNT is added by 0.1% wt and pouring temperature at 700 °C, 730 °C and 760 °C. Mechanical tests carried out were tensile test, hardness test, and impact test. The highest value of hardness and tensile strength was obtained at the pouring temperature of 700 °C are78 HV and 80.97 MPa. Lower pouring temperature causes smaller grain size so that it has higher strength. The distrib...
Urban artisanal gold mining (UAGM) in Makassar, South Sulawesi, Indonesia, has been run by a numb... more Urban artisanal gold mining (UAGM) in Makassar, South Sulawesi, Indonesia, has been run by a number of urban gold workers with gold jewelry manufacture as its core activity. The wastes generated from goldsmiths' activities were further processed by the gold smelters to recover fine gold particles. Smelting gold doré, amalgamation, and burning out the amalgam were the mercury-based gold process usually applied in their work. While working the gold workers are, therefore, potentially exposed to a source of mercury pollution that may cause health problems because of working without proper protection. The aims of this research are to characterize the process of urban artisanal gold mining with the potential mercury exposures during the process, and to assess the health of the gold workers. The results showed that the gold workers had a low educational background, but a relatively high income. The total mercury concentration of gold workers was higher than the control group. They were exposed to intoxicatingly high levels of mercury with the average total mercury concentrations of 6.6 and 10.8 µg/g in the hair of indirect and direct exposed workers, respectively. The health assessment showed that 85% of the gold workers suffered neurological symptoms, such as tremors, and 44%-56% of them experienced restricted fields of vision, slow reflexes, sensory disturbances, unbalanced rigidity, and ataxia. The results also showed that the working years have reasonable correlation with the sum of the positive findings in the 10 neurological symptoms.
Tujuan penelitian ini adalah menemukan temperatur dan waktu tahan efektif dimana atomatom karbon ... more Tujuan penelitian ini adalah menemukan temperatur dan waktu tahan efektif dimana atomatom karbon berdifusi ke dalam permukaan spesimen. Proses karburisasi menggunakan arang tongkol kelapa sawit sebagai media karburasi. Tongkol kelapa sawit dibakar dan digiling menjadi carbon kelapa sawit berukuran 100 mesh. Spesimen dikarburisasi di dalam furnace pada temperatur 800aG, 850 aC, 900°C selama waktu tahan 2, 3, dan 4 jam. Pengujian kekerasan dan metalografi dilakukan untuk mengetahui nilai kekerasan dan keberadaan atom-atom karbon pada permukaan material. Hasil penelitian menunjukkan kekerasan tertinggi adalah 39 HRC pada 4 jam di temperatur 900°C. Namun, pada waktu tahan 2 jam di temperatur ini, kekerasan naik secara berarti dari 7 HRC menjadi 37 HRC dan naik tipis hingga mencapai 39 HRC pada waktu tahan 4jam. Hasil uji metalografi menunjukkan atom-atom karbon dalam fasa pearlite terdispersi dipermukaan spesimen.
Red fluorescence lamellae in prismatic layers of Pinctada vulgaris shell were investigated. SEM-E... more Red fluorescence lamellae in prismatic layers of Pinctada vulgaris shell were investigated. SEM-EDS, XRD, and TG-DTA were utilized to characterize prismatic layers. We found that prismatic layers are calcitic prismatic (CP) layers with rich organic substances. Excitation spectrum for red fluorescence determined by a spectrophotometer indicates that the fluorescent matter in the organic substances is porphyrin compound derivatives. By using a fluorescence microspectroscope, the cross section of CP layers shows red fluorescence forming lamellar pattern. The lamellar pattern consists of red and black parallel zones with a modulation of emission intensity. Elemental mapping show a correlation of the fluorescence intensity decay with sulphur-rich zones occupying the CP layers in the black zones.
Red fluorescence lamellae in prismatic layers of Pinctada vulgaris shell were investigated. SEM-E... more Red fluorescence lamellae in prismatic layers of Pinctada vulgaris shell were investigated. SEM-EDS, XRD, and TG-DTA were utilized to characterize prismatic layers. We found that prismatic layers are calcitic prismatic (CP) layers with rich organic substances. Excitation spectrum for red fluorescence determined by a spectrophotometer indicates that the fluorescent matter in the organic substances is porphyrin compound derivatives. By using a fluorescence microspectroscope, the cross section of CP layers shows red fluorescence forming lamellar pattern. The lamellar pattern consists of red and black parallel zones with a modulation of emission intensity. Elemental mapping show a correlation of the fluorescence intensity decay with sulphur-rich zones occupying the CP layers in the black zones. 2014 Optical Society of America OCIS codes: (160.2540) Fluorescent and luminescent materials; (180.2520) Fluorescent microscopy; (999.9999) Shell.
Penelitian ini menyelidiki karakteristik komposit epoxy-serat bambu yang berkatian dengan sifat k... more Penelitian ini menyelidiki karakteristik komposit epoxy-serat bambu yang berkatian dengan sifat kekakuannya (modulus elastisitas komposit dengan pengujian tarik, pergeseran beam dalam arah sumbu Y pada berbagai titik dan dalam arah sumbu X sepanjang beam dengan menggunakan metode elemen hingga, penguatan yang ditimbulkan oleh serat bambu). Komposit ini memiliki ciri unisotropic. Serat bambu disusun dengan arah 0 o , 30 o , 45 o , 60 o dan 90 o menjadi bentuk beam sepanjang 300 mm. Hasil penelitian menunjukkan kontribusi serat arah 30 o paling besar dalam penguatan modulus elastisitas komposit sebesar 993 N/mm 2 dan defleksi terkecil sebesar 4,55 mm.
Objective: The purpose of this study was to evaluate the effect of herbal alternatives, extract o... more Objective: The purpose of this study was to evaluate the effect of herbal alternatives, extract of sidaguri (sida rhombifolia) combine with extract of jatropha sap (jatropha curcas) application on microhardness and morphology of tooth surface. Material and Methods: Twelve upper first premolar teeth were used in this study, prepared to Class I box cavities, and were then allocated into 4 groups (n=3). Group 1-3 were treated groups, applied with combined extracts of a small dose (5 mg), medium dose (25 mg), and high dose (50 mg), while group 4 was the control group. The cavities were restored with composite resin, immersed in artificial saliva, and stored at room temperature for 14 days. The fillings and extracts were removed and cleaned under running tap water. The teeth were cut in a vertical direction towards the apex, sectioned into 1 mm thickness, and evaluated using Laser Scanning Microscope (LSM), then were examined for microhardness test. Results: All treated groups showed significantly lower microhardness than the control group. Tooth porosity was observed, and its extensiveness was affected by doses of extracts. Conclusion: The application of herbal alternatives (extract of sidaguri and jatropha) lowered the microhardness of tooth structure and caused tooth porosities.
Aluminium matrix composite reinforced Carbon nanoTubes are widely developed because it can increa... more Aluminium matrix composite reinforced Carbon nanoTubes are widely developed because it can increase mechanical strength without reducing its ductility. One of the AMC / CNT manufacturing processes is through the stir casting method. The challenge of the Al / CNT manufacturing process is the occurrence of agglomeration and CNT not homogeneous so that the right casting parameters are needed to obtain optimal results. The purpose of this study was to analyse the effect of pouring temperature on the mechanical strength and microstructure of AA6061 by adding Carbon Nanotube (CNT) through the stir casting method. The CNT is added by 0.1% wt and pouring temperature at 700 °C, 730 °C and 760 °C. Mechanical tests carried out were tensile test, hardness test, and impact test. The highest value of hardness and tensile strength was obtained at the pouring temperature of 700 °C are78 HV and 80.97 MPa. Lower pouring temperature causes smaller grain size so that it has higher strength. The distrib...
Urban artisanal gold mining (UAGM) in Makassar, South Sulawesi, Indonesia, has been run by a numb... more Urban artisanal gold mining (UAGM) in Makassar, South Sulawesi, Indonesia, has been run by a number of urban gold workers with gold jewelry manufacture as its core activity. The wastes generated from goldsmiths' activities were further processed by the gold smelters to recover fine gold particles. Smelting gold doré, amalgamation, and burning out the amalgam were the mercury-based gold process usually applied in their work. While working the gold workers are, therefore, potentially exposed to a source of mercury pollution that may cause health problems because of working without proper protection. The aims of this research are to characterize the process of urban artisanal gold mining with the potential mercury exposures during the process, and to assess the health of the gold workers. The results showed that the gold workers had a low educational background, but a relatively high income. The total mercury concentration of gold workers was higher than the control group. They were exposed to intoxicatingly high levels of mercury with the average total mercury concentrations of 6.6 and 10.8 µg/g in the hair of indirect and direct exposed workers, respectively. The health assessment showed that 85% of the gold workers suffered neurological symptoms, such as tremors, and 44%-56% of them experienced restricted fields of vision, slow reflexes, sensory disturbances, unbalanced rigidity, and ataxia. The results also showed that the working years have reasonable correlation with the sum of the positive findings in the 10 neurological symptoms.
Tujuan penelitian ini adalah menemukan temperatur dan waktu tahan efektif dimana atomatom karbon ... more Tujuan penelitian ini adalah menemukan temperatur dan waktu tahan efektif dimana atomatom karbon berdifusi ke dalam permukaan spesimen. Proses karburisasi menggunakan arang tongkol kelapa sawit sebagai media karburasi. Tongkol kelapa sawit dibakar dan digiling menjadi carbon kelapa sawit berukuran 100 mesh. Spesimen dikarburisasi di dalam furnace pada temperatur 800aG, 850 aC, 900°C selama waktu tahan 2, 3, dan 4 jam. Pengujian kekerasan dan metalografi dilakukan untuk mengetahui nilai kekerasan dan keberadaan atom-atom karbon pada permukaan material. Hasil penelitian menunjukkan kekerasan tertinggi adalah 39 HRC pada 4 jam di temperatur 900°C. Namun, pada waktu tahan 2 jam di temperatur ini, kekerasan naik secara berarti dari 7 HRC menjadi 37 HRC dan naik tipis hingga mencapai 39 HRC pada waktu tahan 4jam. Hasil uji metalografi menunjukkan atom-atom karbon dalam fasa pearlite terdispersi dipermukaan spesimen.
Red fluorescence lamellae in prismatic layers of Pinctada vulgaris shell were investigated. SEM-E... more Red fluorescence lamellae in prismatic layers of Pinctada vulgaris shell were investigated. SEM-EDS, XRD, and TG-DTA were utilized to characterize prismatic layers. We found that prismatic layers are calcitic prismatic (CP) layers with rich organic substances. Excitation spectrum for red fluorescence determined by a spectrophotometer indicates that the fluorescent matter in the organic substances is porphyrin compound derivatives. By using a fluorescence microspectroscope, the cross section of CP layers shows red fluorescence forming lamellar pattern. The lamellar pattern consists of red and black parallel zones with a modulation of emission intensity. Elemental mapping show a correlation of the fluorescence intensity decay with sulphur-rich zones occupying the CP layers in the black zones.
Red fluorescence lamellae in prismatic layers of Pinctada vulgaris shell were investigated. SEM-E... more Red fluorescence lamellae in prismatic layers of Pinctada vulgaris shell were investigated. SEM-EDS, XRD, and TG-DTA were utilized to characterize prismatic layers. We found that prismatic layers are calcitic prismatic (CP) layers with rich organic substances. Excitation spectrum for red fluorescence determined by a spectrophotometer indicates that the fluorescent matter in the organic substances is porphyrin compound derivatives. By using a fluorescence microspectroscope, the cross section of CP layers shows red fluorescence forming lamellar pattern. The lamellar pattern consists of red and black parallel zones with a modulation of emission intensity. Elemental mapping show a correlation of the fluorescence intensity decay with sulphur-rich zones occupying the CP layers in the black zones. 2014 Optical Society of America OCIS codes: (160.2540) Fluorescent and luminescent materials; (180.2520) Fluorescent microscopy; (999.9999) Shell.
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