Journal of Mathematical and Fundamental Sciences
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A Note on the Flare Stars in the Coalsack
Get PDFRingkasan. Didalam tulisan ini dilaporkan penemuan 5 buah "flare stars" di daerah Coalsack. Abstract. The discovery of 5 flare stars in the Coalsack is reported.
Poisson Bracket Relativistic
No full textAbstract. Classical Poisson Bracket is extended to the four dimensional space - time formalism in Special Relativity. This formulation gives the relativistic equation of motion appeared directly as its consequenced. Ringkasan. Dalam artikel ini dicoba memperluaskan notasi Poisson Bracket dalam Mekanika Klassik ke dalam ruang-waktu berdimensi empat dari Teori Relativistik Khusus. Formulasi ini, ternyata sangat menarik sekali karena memberikan persamaan-persamaan gerak relativistik muncul secara wajar sebagai konsekwensinya
Simple Method to Calculate the Oscillating Lift on a Circular Cylinder in Potential Flow
Get PDFAbstract. A simple potential flow model is presented to calculate the oscillating lift on a circular cylinder. In essence, the time dependent lift acting on a cylinder is due to the presence of a vortex shed off the separation point on the cylinder. The vortex strength and its trajectory is predicted employing the condition of zero force on the vortex and its feeding vortex sheet. The vortex breaks away from the cylinder and is convected by the fluid after the vortex strength reaches a maximum value, and another vortex is shed at the other side of the cylinder. Oscillating lift with the right order of magnitude of available experimental results was predicted. For subcritical flow, good agreement is obtained between the predicted Strouhal number and that found experimentally. Ringkasan. Suatu model aliran potensial sederhana diuraikan untuk menghitung gaya angkat yang berosilasi pada silinder lingkaran. Pada dasarnya, gaya angkat yang berosilasi ini disebabkan karena adanya vortex yang dilepaskan oleh silinder dari titik pemisahan. Kekuatan vortex dan lintasannya dihitung dengan menggunakan syarat bahwa gaya pada vortex dan bidang vortex yang menumbuhkannya harus sama dengan nol. Vortex ini terputus dari silinder pada waktu kekuatannya mencapai maksimum, dan vortex yang lain mulai dilepaskan pada sisi silinder yang lain. Hasil perhitungan menunjukkan harga gaya angkat maksimum yang mendekati harga yang diperoleh secara eksperimentil. Demikian pula, untuk aliran subkritis, diperoleh hasil perhitungan bilangan Strouhal yang mendekati harga yang diperoleh secara eksperimen
Geothermy and its Future in Indonesia
Get PDFAbstract. The basic concept of a commercial steamfield is discussed and defined in this paper. Based on this discussion potential areas are indicated in a map. It is found that not less 24 geotherrnal areas are prospectable. However, it is found that very little is known about the exact potential of Indonesia in the field of geothermy. Anticipating the rising demand in electricity within the context of the broader industrialisation program of Indonesia and the limitation of its fossil fuel reserve, it is suggested that all possibilities for utilising different kinds of energy, including geothermy should be explored as far as possible. Ringkasan. Konsep dasar dari suatu medan uap alam komersil diperbincangkan dan didefinisikan. Berdasarkan pada diskusi tersebut daerah-derah dengan potensi geothermy dicantumkan ke dalam peta. Ternyata bahwa tak kurang dari 24 medan hyperthermal tersebar di seluruh wilayah Indonesia yang berkemungkinan untuk dapat dieksplorasikan lebih lanjut. Saying sekali bahwa sangat sedikit yang diketahui mengenai potensi Indonesia sesuangguhnya dalam bidang ini. Menghadapi permintaan tenaga listrik yang semakin menanjak dalam rangka pengembangan program industrialisasi Indonesia, dan terbatasnya persediaan bahan bakar fossil, pengarang menganjurkan agar semua segi dan kemungkinan pemanfaatan segala macam sumber energi , termasuk geothermy, dijajaki sejauh mungkin
Mesodermal Competence of the Presumptive Ecto-Neuroderm at Various Developmental Stages, in Xenopus laevis (Daudin)
Get PDFAbstract. A comparative study on the reactive capacity of the presumptive ecto-neuroderm on mesoderm formation with increase of age has been done in Xenopus Laevis. It was proved that before gastrulation, mesoderm induction mainly produces dorsal mesodermal structures. During the gastrulation process the product of differentiation tends to shift from dorsaL to ventral mesodermal structures. The presumptive ecto-neuroderm has has already a competence for mesoderm formation at the early blastula stage and this competence starts to fade out at the horse-shoe-shaped blastopore stage. Ringkasan. Suatu studi perbandingan mengenai kapasitas berreaksi dalam membentuk mesoderm dari presumptive ekto-neuroderm dengan bertambahnya umur, telah dilakukan pada Xenopus laevis. Telah dibuktikan, bahwa sebelum gastrulasi induksi mesoderm terutama menghasilkan struktur-struktur mesoderm dorsal. Selama proses gastrulasi berlangsung, hasil differensiasi cenderung untuk menggeser dari struktur-struktur mesoderm dorsal ke struktur-struktur mesoderm ventral. Presumptif ekto-neuroderm telah mempunyai kompetensi untuk membentuk mesoderm pada stadium blastula muda dan kompetensi tersebut mulai menghilang pada stadium blastoporus berbentuk sepatu kuda.
Some Notes on the Energy Metabolism of Gadus callarias and Gadus virens in Relation to Body Size
No full textThe present work of oxygen consumption in Gadus callarias and Gadus virens shows that there is a connection between the body size and the acclimation time required for reaching a "normal" level of metabolism after being transferred to another aquarium (fig. : 1, 2, 3 & 4). The oxygen consumption under standard condition shows that there is a clear linear regression between the two variable used. However, the significant coefficient does not exclude the possibility of a difference in oxygen consumption in relation to the weight between small fish and bigger ones.
Geothermal System of the Dieng-Batur Volcanic Complex
Get PDFThis paper is mainly concerned with the evaluation of reports on geophysical and geochemical surveys made by Group Seven Inc. and Truesdell in the Dieng Mountains under contract with US-AID and on behalf of the Directorate General for Power and Electricity and the Indonesian Geological Survey and partly also with the author's own field observation on geothermy in the Dieng Mountains in Central Java. All the accumulated data lead to the conclusion that the geothermal system of eastern Dieng originated through the intersection of two major fracture zones. The high chloride content found in various streams gives good reason to accept that the geothermal system of the Dieng Mountains is a system of hot water and steam rather than a system of dry steam only. The hot springs in the Dieng Mountains might represent surface manifestation of a deep, neutral, hot water "reservoir". The distribution of geo-electric anomaly which resulted from two dipole mapping surveys delineated a belt of anomalously low resistivity in the eastern Dieng Mountains in which there are three areas of very low resistivity indicating systems of up-welling thermal water. These systems might be connected at great depth. The area with low resistivity anomaly might indicate a reservoir having a volume of 5 to 6 cubic kilometers at depth of 2 kilometers. An estimate based on geophysical data suggests that a power production rate of 200 megawatts could be supported for 25 years, or of 100 megawatts for 50 years. Based on all those data an exploratory deep drilling work is recommended which is due to start in June 1971.
On the Stratigraphic Positionof Pithecantropus Mandible- C.
Get PDFAbstract. Up to now almost all of Java's Early as well as Middle Pliestocene hominids are surface finds. As a result, the relative age of determinations of these specimens are matters of speculations. Pithecantropus C is also a surface find and obtained from the surface of the Lower Pleistocene Putjangan beds from the Sangiran area (Central Java, Indonesia). Within the encrusting matrix of the Pithecantropus mandible have been collected a fauna of smaller foraminifera. Based on comparison of this faunal assemblage with the faunal associations of small foraminifera from the Putjangan beds, the stratigraphic position of the mandible can be established and in this way its relative age is supposed to be Late Lower Pleistocene. Ringkasan. Hampir semua fosil-fosil hominidae berumur Plestosen Bawah dan Plestosen Tengah dipula Djawa merupaka penemuan-penemuan dipermukaan tanah. Hal ini menjebabkan penentuan umur relatip fosil-fosil itu suatu hal jang spekulatip. Pithecanthropus C merupakan pula suatu penemuan diatas permukaan tanah dari lapisan-lapisan Putjangan diderah Sangiran (Djawa Tengah, Indonesia) jang berumur Plestosen Bawah. Didalam batuan jang melekat pada rahang bawah Pithecanthropus itu terdapat fauna foraminifera ketjil. Berdasarkan perbandingan antara fauna foraminifera ketjil ini dengan fauna foraminifer ketjil jang terdapat didalam lapisan-lapisan Putjangan diatas, maka dapatlah ditentukan posisi stratigrafi rahang bawah itu didalam lapisan-lapisan Putjangan tersebut, sehingga dengan demikian dapat diperkirakan bahwa umur relatip Pithecanthropus C itu adalah Plestosen Bawah Muda
Metode untuk Menghitung Gangguan Kilat oada Kawat Transmisi Tegangan Tinggi
Get PDFIchtisar. Metode AIEE1 jang lebih dari sepuluh tahun terachir ini dipakai untuk menghitung gangguan kilat pada kawat transmisi, ternjata tidak dapat lagi dipakai untuk kawat transmisi tegangan tinggi (150 Kv atau lebih). Metode ini memberikan hasil jang terlampau rendah. Metode2 jang lain (Teori Gelombang Berdjalan2, Teori Medan3,4 dan Metode Computer Monte Carlo5) telah ditjoba dan memberikan hasil jang lebih memuaskan. Berdasarkan teori2 jang disebut diatas penulis mentjoba menguraikan satu metode analitis jang dapat dipergunakan untuk computer atau dengan pertolongan mistar hitung.Abstract. AIEE method for calculating the lightning outages of transmission lines has been accepted and applied for more than a decade. It is realized that for extra high voltages (150Kv and higher) this method can no longer be applied. It gives too low values compared to observations. Some other methods (Traveling Wave Theory, Field Theory and Monte Carlo Computer Method) have been tried and give more satisfactorily results. Based on the theories mentioned above the writer tries to outline an analytical method that can be applied to either computer or by mean of slide rules
Diagram Vektor Arus dan Tegangan Saluran Transmisi
No full textIchtisar. Untuk saluran2 transmisi pendek untuk membuat suatu diagram vector jang menjatakan hubungan antara tegangan dan arus daripada udjung awal dan udjung achir, adalah suatu hal jang sederhana. Untuk saluran listrik jang pandjang prosedur ini adalah rumit, karena adanja kapasitansi2 shunt jang didistribusikan. Akan tetapi dengan merubah persamaan2 untuk saluran pandjang, hal ini dapat dilakukan dengan tjara relatif praktis. Untuk maksud itu, bagi tiap besaran dipakailah harga2 per unit berdasarkan tegangan pada udjung achir dan arus beban karakteristik. Suatu lingkaran, sebagai locus daripada tegangan awal sesuai dengan factor daja = 1, djuga diturunkan dari uraian itu. Abstract. For short transmission lines it is a simple matter to construct a vector diagram showing the phase relationships between the sending-end and receiving-end voltages and currents. For an electrically long line the procedure is complicated because of the presence of the distributes shunt capacitances. By transforming the equations of a long line, however, it is possible to accomplish this in a relatively practical way. For that purpose per unit quantities are used with the receiving-end voltage and the surge-impedance-load current taken as basis. A circle as locus of sending-end voltage corresponding to unity sending "“end power factor is also derived from the consideration