Subduction-zone structure and magmatic processes beneath Costa Rica constrained by local earthquake tomography and petrological modelling

A high-quality data set of 3790 earthquakes were simultaneously inverted for hypocentre locations and 3-D P-wave velocities in Costa Rica. Tests with synthetic data and resolution estimates derived from the resolution matrix indicate that the velocity model is well constrained in central Costa Rica to a depth of 70 km; northwestern and southeastern Costa Rica are less well resolved owing to a lack of seismic stations and seismicity. Maximum H2O content and seismic wave speeds of mid-ocean ridge basalt and harzburgite were calculated for metamorphic phase transformations relevant to subduction. Both the 3-D P-wave velocity structure and petrological modelling indicate the existence of low-velocity hydrous oceanic crust in the subducting Cocos Plate beneath central Costa Rica. Intermediate-depth seismicity correlates well with the predicted locations of hydrous metamorphic rocks, suggesting that dehydration plays a key role in generating intermediate-depth earthquakes beneath Costa Rica. Wadati-Benioff zone seismicity beneath central Costa Rica shows a remarkable decrease in maximum depth toward southeastern Costa Rica. The presence of asthenosphere beneath southeastern Costa Rica, which entered through a proposed slab window, may explain the shallowing of seismicity due to increased temperatures and associated shallowing of dehydration of the slab. Tomographic images further constrain the existence of deeply subducted seamounts beneath central Costa Rica. Large, low P-wave velocity areas within the lower crust are imaged beneath the southeasternmost volcanoes in central Costa Rica. These low velocities may represent anomalously hot material or even melt associated with active volcanism in central Costa Rica. Tomographic images and petrological modelling indicate the existence of a shallow, possibly hydrated mantle wedge beneath central Costa Ric

Sistem Rekrutmen, Seleksi Dan Penempatan Kepala Sekolah Menengah Pertama Negeri Pada Dinas Pendidikan Kota Banda Aceh

Recruitment, selection, and replacement of the principal conducted in accordance with competence can improve the quality of education management. This research aimed at figuring out the description of process of recruitment, selection, and replacement and also the obstacles in recruitment, selection and replacement of State Junior High School principal at Education Agency of Banda Aceh. This research employed descriptive qualitative method. Data was collected by using observation, interview, and documentation technique. Subject of the research was principal and teacher at State Junior High School. The result of the research showed that: first, the recruitment process, the Education Agency prepared a recruitment program comprising of implementation and technical guidance of recruitment implementation for the candidates of principal, then there was an official announcement from the Education Agency. Second, the selection process on the principal candidates comprised of administrative selection carried out through the assessment of the completeness of documents and academic selection carried out through the assessment of the leadership potential and initial mastery of toward competence of principal. Third, the replacement process of principal candidates was conducted because there was principal vacancy caused by the transfer, retirement, and dismissal. Fourth, the obstacles in recruitment, selection, and replacement of the principalwere lack of interest of the teachers to run for principal and lack of the budget for principal recruitment. It can be concluded that the recruitment, selection, and replacement of State Junior High School principal are still ineffective and inefficient

A Low-cost Rf Driver for Acousto-optic Modulator

Pada makalah ini kami melaporkan pembuatan rangkaian sederhana namun fungsional untuk mengoperasikan suatu modulator akusto-optik (AOM). Rangkaian ini dibuat sebagai alternatif menggantikan rangkaian yang tersedia di pasaran dengan harga yang mahal. Pembuatan rangkaian ini mengikuti petunjuk ARRL dalam perancangan transistor penguat daya pada frekuensi operasi 80 MHz dengan rangkaian LC sebagai penjodoh impedansi untuk memberikan daya sebesar 1 W baikkontinyu maupun terpulsakan pada beban 50 Ω. Perancangan harus dilakukan dengan seksama agar jangan sampai daya yang diberikan terlalu berlebih yang dapat merusak AOM. Rangkaian ini dapat mengoperasikan AOM untuk mendifraksikan sinar laser dengan efisiensi 80% untuk orde difraksi pertama. Sinar laser yang terdifraksikan ini digunakan sebagai sumber cahaya bagi interferometer heterodin serat optik untuk menghasilkan sinyal layangan pada frekuensi 80 MHz atau 160 MHz.We report in this paper the construction of a simple, low-cost, yet functional RF driver for an acousto-optic modulator (AOM). This circuit is built as an alternative to the relatively expensivecommercially available one. The construction follows the ARRL guide in designing an 80 MHz transistor power amplifier with an LC matching network to deliver about 1 W of power to a 50Ω load (the AOM) either continuously or pulsed. Care must be taken in the circuit construction in order not to generate too much power which can destroy the costly AOM. The finished circuit can drive an AOM to diffract a laser beam to a first-order with 80% efficiency. The diffracted beam is then used a light source in an optical fibre heterodyne interferometer to produce an 80 MHz or 160 MHz optical beat signal

Pengembangan Material Tapak Roda Kereta Api Impor Dengan Penambahan Paduan Dan Perlakuan Panas Normalisasi Pendinginan Kipas

Roda kereta api adalah satu-satunya komponen kereta api yang masih diimpor seluruhnya. Kebutuhankomponen ini cukup besar yaitu sekitar 30.000 keping pertahunnya, dan diprediksi akan meningkat terus.Pembuatan roda kereta api menurut standar Association of American Railroads (AAR) dapat melalui prosestempa atau pengecoran. Di Indonesia pembuatan komponen ini yang paling memungkinkan adalah denganproses pengecoran. Penelitian ini adalah penelitian terapan yang dimulai dengan analisa material roda kereta apiimpor dan dilanjutkan dengan pengembangan material dan proses untuk membuat prototipe roda kereta api.Dari hasil pengujian kekerasan prototipe tapak roda kereta api hasil normalisasi dengan pendinginan kipas,diperoleh kekerasan sebesar 36 HRC dimana lebih tinggi dibandingkan kekerasan tapak roda kereta api imporyang hanya 26 HRC. Struktur mikro prototipe tapak roda kereta api hasil normalisasi dengan pendinginan kipasadalah aggregate bainite di bagian bawah permukaan hingga 1 mm, dan pearlite yang sangat halus di bagiandalam antara 1 mm hingga 10 mm dari permukaan. Unsur molibden dan nikel sebagai bainite promotormenyebabkan terbentuknya aggregate bainite, sedangkan unsur mangan, krom dan tembaga berperan sebagaipartition elements diantara ferrite dan cementite yang menghambat pertumbuhan pearlite, sehingga dihasilkanpearlite yang halus. Selain itu laju pendinginan yang cepat dari pendinginan kipas memperlambat difusi karbon didalam austenite sehingga cenderung menghasilkan aggregate bainite di bagian permukaan serta pearlite halusdi bagian dalam tapak prototipe roda kereta api hasil normalisasi dengan pendinginan kipas

Sejarah masa revolusi fisik Daerah Sulawesi Tenggara

Buku ini berisi tentang sejarah masa revolusi fisik di daerah Sulawesi Tenggara. mulai dari keadaan Sulawesi Tenggara pada masa pemerintahan Jepang, sebelum dan sesudah proklamasi kemerdekaan, hingga perjuangan kemerdekaan menentang sekutu dan belanda, serta keadaan menjelang akhir revolusi kemerdekaa

Sampling Assistance Using the Poct Cholesterol Tool for Patients with Diabetes Mellitus in the Working Area of Puskesmas Ome

Diabetes has now become the seventh cause of death in all age groups in Indonesia. There is a tendency for non-communicable diseases such as Diabetes Mellitus (DM) to increase. This is due to unhealthy lifestyle behaviors that continue to develop in society. DM patients have the potential to suffer various complications if their glucose levels are not controlled. The rapid pace of technology has caused many laboratory equipment manufacturers to create a tool that can be used by both the health community and the non-health community. However, in preparing samples for examination, a phlebotomy technique is needed. Poor phlebotomy technique will affect the examination results issued by the portable device. This community service activity aims to provide knowledge and health checks related to sampling using a poct cholesterol tool for people with Diabetes Mellitus in the Work Area of the Ome Health Center. The methods used in this community service are lectures, question and answer and health checks, practicum (demonstrations), posttests and monitoring evaluations which are carried out 2 weeks later. The results of this community service resulted in the ability to use the POCT tool independently