Analisis Data Magnetisasi Remanen Isotermal dengan Software IRMUNMIX

Telah dilakukan kajian kinerja software IRMUNMIX terhadap sampel yang terindikasi hanya memiliki satu komponen mineral magnetik. Hasil menunjukkan bahwa software IRMUNMIX mampu mendeteksi komponen mineral magnetik dengan kontribusi yang sangat minimal

Simulated Interannual Modulation of Intraseasonal Kelvin Waves in the Equatorial Indian Ocean

Outputs from a high-resolution ocean general circulation model (OGCM) for the period of 1990-2003 indicate an interannual modulation of intraseasonal Kelvin waves along the equatorial Indian Ocean. During normal conditions without IOD event, the first mode explains about 30-40% of the total variance in the western (60-65ºE) and central (75-80ºE) basin, while the second mode contributes up to 45% to the total variance in the central basin around the longitude of 82ºE. In contrast, during the 1997/98 IOD event, the fourth mode caused about 40% of the total variance in the central and eastern basin. During the 1994 IOD event, the contribution from the fourth baroclinic mode in the eastern basin caused 45% of the total variance. In the central basin, the second and the fourth baroclinic mode caused almost the same variance (~40%). The variations in the characteristics of the intraseasonal Kelvin waves are related to variations in the vertical stratification. During the IOD event, the pycnocline in the eastern basin was raised by about 50 m and the stratification at the upper level is strengthened, while it is weakened at lower levels. These changes lead to an increase in the contribution of higher-order baroclinic modes

Effect of Ground Vibration to Slope Stability, Case Study Landslide on The Mouth of Railway Tunnel, Gunung Gajah Village, Lahat District

Slope stability around railway tunnel in Gunung Gajah Village, Lahat District needs to be analysed due to landslide which occurred on January, 23th 2016. That analysis needs to be done so that the railway transportation system can run safely. The purposes of this research are: to find out the factors that cause slope instability, to find out peak acceleration caused by railway traffic and earthquakes and its effects to the safety factor of slope, and determine stabilization method in order to prevent the occurrence of further landslide. The research activities include surveying, sampling, laboratory testing and analyzing slope stability using pseudo-static approach. Based on research result, the main factors that cause slope instability are morphology, structural geology, and ground vibration caused by earthquakes. Ground vibration are correlated to the slope instability. It shows that the higher of peak acceleration the lower of safety factor of slope. To prevent the occurrence of further landslide around research area, stabilization method should be applied in accordance with the conditions in that area such as building a retaining wall to increase safety factor of slope, building draining channels to reduce run off and performing shotcrete in the wall of landslide in order to avoid weathering.Keywords: ground vibration, slope stability, stabilization metho

Efektivitas Elektroda pada Proses Elektrokoagulasi untuk Pengolahan Air Asam Tambang

Air limpasan dari aktivitas pertambangan batubara sangat berpotensi pada pembentukan air asam tambang. Air asam tambang yang berasal dari mine sump area tambang Air Laya PT. Bukit Asam (Persero), Tbk. mempunyai nilai pH rendah yaitu berkisar dari 3 sampai 5, kondisi ini akan melarutkan unsur-unsur logam seperti Fe dan Mn pada batuan yang dilalui oleh air asam tambang tersebut. Elektrokoagulasi merupakan metode untuk melakukan proses koagulasi dengan menggunakan tegangan listrik searah yang didasarkan pada peristiwa elektrokimia. Penelitian dilakukan dengan sistem batch skala laboratorium yaitu menggunakan volume air asam tambang 1,8 L, elektroda besi (Fe) 8 cm x 11 cm x 0,8 mm sebanyak 3 lempeng sebagai katoda dan elektroda aluminium (Al) 8 cm x 11 cm x 0,8 mm sebanyak 3 lempeng sebagai anoda. Percobaan dilakukan dengan interval waktu 15 menit, 30 menit, 45 menit dan 60 menit, lalu menggunakan tegangan 6 V, 12 V, dan 24 V untuk jarak elektroda yaitu 1,5 cm dan 2 cm. Dengan tetap mempertimbangkan faktor ekonomi maka diketahui waktu, jarak dan tegangan DC yang paling efektif digunakan untuk proses elektrokoagulasi adalah 12 Volt dan 45 menit yang akan menghasilkan persen peningkatan nilai pH = 32,96 ; persen penurunan logam Fe = 94,0111 ; dan persen penurunan logam Mn = 88,2878, akan tetapi faktor jarak antara elektroda tidak berpengaruh pada proses ini

On the Influence of Enso And IOD on Rainfall Variability Over The Musi Basin, South Sumatra

The southern Sumatera region experiences one rainy season and one dry season in a year associated with seasonal change in monsoonal winds. The peak of rainy season is occurring in November-December-January during the northwest monsoon season, while the dry season comes in June-July-August during the southeast monsoon season. This study is designed to evaluate possible influence of the coupled ocean-atmospheric modes in the tropical Indo-Pacific region, namely the El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) on the rainfall variability over the catchment area of the Music Basin, South Sumatera. The ENSO and IOD occurrences were reflected by the variability of sea surface temperature (SST) in the tropical Pacific and Indian Ocean, respectively. During El Niño and/or positive IOD episode, negative SST anomalies cover the eastern tropical Indian Ocean and western tropical Pacific including the Indonesian seas, leading to suppress convective activities that result in reduce precipitation over the maritime continent. The situation is reversed during La Niña and/or negative IOD event. The results revealed that the high topography area (e.g. Bukit Barisan) was shown to be instrumental to the pattern of rainfall variability. During the 2010 negative IOD co-occurring with La Niña event, the rainfall was significantly increase over the region. This excess rainfall was associated with warm SST anomaly over the eastern tropical Indian Ocean and the Indonesian seas. On the other hand, extreme drought event tends to occur during the 2015 positive IOD simultaneously with the occurrence of the El Niño events Investigation on the SST patterns revealed that cold SST anomalies covered the Indonesian seas during the peak phase of the 2015 positive IOD and El Niño event

Equatorial Oceanic Waves and the Evolution of 2007 Positive Indian Ocean Dipole

The role of equatorial oceanic waves on the evolution of the 2007 positive Indian Ocean Dipole (pIOD) event was evaluated using available observations and output from a quasi-analytical linear wave model. It was found that the 2007 pIOD event was a weak and short-lived event: developed in the mid-summer (July), matured in the early-fall (September), and terminated in the mid-fall (October). The evolution of the 2007 pIOD event was linked to the equatorial wave dynamics. The event development was associated with the generation of upwelling equatorial Kelvin waves (westward current anomalies) generated by easterly wind anomalies. The event termination was associated with the occurrence of eastward zonal current anomalies resulting from a complex interplay between the wind-forced down welling Kelvin waves and the eastern-boundary-reflected Rossby waves. Results from a quasi-analytical linear wave model show that during the event development and maturation, the wind-forced Kelvin waves played a dominant role in generating zonal current anomalies along the equatorial Indian Ocean, while the eastern-boundary-reflected Rossby waves tended to weaken the wind-forced Kelvin wave signals. During the event termination our model shows that the initiation of anomalous eastward current resulted from the reflected Rossby waves at the eastern boundary. The wind-forced Kelvin waves associated with the seasonal reversal of the monsoon further strengthened the eastward zonal currents generated by the boundary-generated Rossby waves in late-October/early-November. This highlights the importance of the eastern-boundary-reflected Rossby waves on the IOD event termination

PENGGUNAAN PIRANTI LUNAK JUPYTER NOTEBOOK DALAM UPAYA MENSOSIALISASIKAN OPEN SCIENCE

Era keterbukaan dan perkembangan piranti komputer mendesak para ilmuwan untuk segera mempraktekkan open science. Sekarang ini, banyak pembaca jurnal ilmiah menghendaki suatu artikel ilmiah dapat ditelusuri ulang baik data yang dimuat maupun metodologi analisis data yang digunakan penulis di dalam menarik kesimpulannya. Jupyter Notebook adalah sebuah piranti lunak yang dapat digunakan untuk menampilkan dan menganalisis data dengan mudah. Makalah ini membahas tentang penggunaan Jupyter Notebook di bidang geofisika

Jupyter Notebook App: Alternatif Teknologi Pembelajaran Fisika Berbasis Web Browser

Dalam beberapa dekade ke belakang, perangkat keras dan perangkat lunak komputer mengalami perkembangan yang sangat cepat. Bagi sebagian besar pemerhati sejarah ilmu pengetahuan, perkembangan yang sangat cepat ini memposisikan komputasi sebagai pilar ketiga dari sains setelah teori dan eksperimen. Sebagai contoh, Perez dan Granger (2007) menciptakan aplikasi IPython Notebook berbasis web browser yang telah digunakan oleh banyak orang di bidang pendidikan dan penelitian. Aplikasi ini kini telah bertransformasi menjadi Jupyter Notebook App, dengan menggunakan bahasa pemograman utama yang lebih beragam, yaitu Julia, Python dan R. Shen (2014) memperkirakan satu juta peneliti dan pendidik telah menggunakan aplikasi ini untuk menunjang kegiatan profesinya. Makalah ini membahas pemanfaatan Jupyter Notebook App sebagai teknologi pembelajaran fisika khususnya di bidang fisika bumi dan fisika bahan dengan menggunakan bahasa pemograman python. Hasil survey terbaru menunjukkan bahwa Python kini telah menjadi bahasa pemograman favorit di beberapa perguruan tinggi ternama di Amerika Serikat (Guo, 2014)

EFFECT OF ARCHITECTURAL TREE MODEL TO THE NOISE LEVEL OF MOTOR VEHICLE ON DEMANG LEBAR DAUN STREET PALEMBANG

The research on the effect of architectural tree model to the noise level of motor vehicles on Demang Lebar Daun Street Palembang has been conducted. The purpose of this study was to analyze kind of architectural tree model can reduce the highest noise levels among the architectural tree models encountered and identify the architectural tree model. The method used was purposive sampling. Measurement of the noise level and architectural models were selected according to the type of the tree encountered on the left or right side of the street. The noise level measurement during the daylight was carried out simultaneously at a point of 1 meter in front of the tree, 1 and 5 meters behind the tree,for 10 minutes with the readings for every 5 seconds at 07:00, 10:00, 15:00 and 20:00. The results showed that The architectural model of Switenia magahoni tree was Rauh model, Lagerstroemia sp. tree was Troll model and Thyrsostachys siamensis tree was McClure model. The highest noise level reduction was from bamboo tree, respectively by 4,88 dB (A) and 8,52 dB (A) at the distances of 1 and 5 m. Keywords: noise level, reduction, architectural tree mode

Coupled Ocean-Atmosphere Mode in the Tropical Indian Ocean during 2011

Coupled ocean-atmosphere mode in the tropical Indian Ocean, so-called the Indian Ocean Dipole (IOD), occurred during boreal summer to fall 2011. In this study, data from satellite observations and atmospheric reanalysis datasets together with data from ocean current mooring were used to evaluate the evolution of the 2011 IOD event. It is shown that the 2011 IOD was a weak and short-lived event. It developed in July, peaked in September, decayed in October and terminated in November. During the peak phase, maximum negative sea surface temperature anomaly off Sumatera-Java reached -1.2 °C. As oceanic response to easterly wind anomalies along the equator, the observed zonal currents in the central and eastern equatorial Indian Ocean also showed prominent westward currents during the peak phase of the 2011 IOD event