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Journal of Mathematical and Fundamental Sciences
Published by Institut Teknologi Bandung
ISSN : 23375760     EISSN : 23385510     DOI : https://doi.org/10.5614/j.math.fund.sci.
Core Subject : Science, Education,
Astronomy Chemistry Earth & Planetary Sciences Mathematics Physics
Journal of Mathematical and Fundamental Sciences welcomes full research articles in the area of Mathematics and Natural Sciences from the following subject areas: Astronomy, Chemistry, Earth Sciences (Geodesy, Geology, Geophysics, Oceanography, Meteorology), Life Sciences (Agriculture, Biochemistry, Biology, Health, Medical, Pharmacy), Mathematics, Physics, and Statistics.
Arjuna Subject : Matematika - Matematika (Lain-Lain)
Articles 6 Documents
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Search results for , issue "Vol. 31 No. 3 (1999)" : 6 Documents clear
Beban Kerut pada Pelat Sandwich Anisotropik Bambang Kismono Hadi
Journal of Mathematical and Fundamental Sciences Vol. 31 No. 3 (1999)
Publisher : Institute for Research and Community Services (LPPM) ITB

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Sari. Suatu metode baru untuk menganalisis kegagalan kerut pada struktur pelat sandwich komposit yang bersifat anisotropic dibahas, baik untuk moda simetri maupun moda tidak simetri. Untuk mendapatkan modus kegagalan ini, modulus geser dan normal transversal bagian inti dimasukkan ke dalam analisis. Pertama-tama, energi regangan total yang terjadi dalam sistem ini akan dihitung, dan dengan menggunakan metode Rayleigh-Ritz, sistem eigen yang didapat akan dipecahkan. Dari hasil yang diperoleh dapat disimpulkan bahwa beban kritis kerut dapat terjadi jauh di bawah beban kritis Euler, sehingga menjadi beban kritis yang lebih berbahaya dibandingkan dengan beban Euler. Beban kerut ini juga terjadi pada panjang gelombang yang jauh lebih pendek daripada beban Euler, sehingga bersifat katastropik. Hasil yang didapat juga menunjukkan bahwa analisis baru ini bersifat umum, yang dapat dipakai untuk menghitung beban kritis Euler maupun beban kritis kerut untuk pelat sandwich komposit anisotropik secara simultan. The Wrinkling of Anisotropic Sandwich PanelsAbstract. A new method to analyze the wrinkling failure of anisotropic sandwich panels was discussed, for both symmetrical and asymmetrical wrinkling. To calculate the wrinkling loads, both shear and transverse normal modulus of the core were included in the analysis. First, the total energy of the system was calculated, and then using the Rayleigh-Ritz method, the eigen-system was solved to get the critical buckling loads. The results show that wrinkling could occur far below their corresponding Euler loads, that make them more dangerous. Wrinkling also contain shorter waves, that may lead to catastrophic failures. The results also show that the new method presented in this article is so general and can be used to calculate both Euler buckling and wrinkling loads of anisotropic sandwich panels simultaneously.
Variasi Tekanan Oksigen dalam Penumbuhan Kristal Tunggal Superkonduktor Bi2Sr2CaCu2O8+δ Darminto Darminto; A.A. Nugroho; A.A. Menovsky; A. Rusydi; W. Loeksmanto
Journal of Mathematical and Fundamental Sciences Vol. 31 No. 3 (1999)
Publisher : Institute for Research and Community Services (LPPM) ITB

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Sari. Dalam tulisan ini disajikan hasil pembuatan kristral tunggal bahan superkonduktor Bi2Sr2CaCu2O8+δ dengan metode travelling solvent floating zone (TSFZ) dalam atmosfer yang benvariasi, yaitu dalam udara dan dalam oksigen (O2) 1 bar dan 2,5 bar. Variasi kadar oksigen yang terjadi dalam kristal sebagai akibat variasi atmosfer telah menyebabkan perbedaan komposisi molar dalam kristal yang terbentuk dan pembentukan fasa takmurnian. Hasil karakterisasi menuniukkan bahwa meningkatnya kadar oksigen dalam Kristal yang bersangkutan menurunkan suhu kritis (Tc) dan parameter anisotropi (γ). Penurunan anisotropi selanjutnya memperbesar medan puncak kedua(H2p) dan menggeseer garis takreversibel (Hirr) ke arah suhu dan medan magnet yang lebih tinggi dalam diagram fasa H-T, yang menunjukkan peningkatan efek pinning vorteks sebagai akibat peningkatan kadar dopan oksigen. Variation of Oxygen Pressure in Growing Bi2Sr2CaCu2O8+δ Single Crystal Superconductors and its EffectsAbstract. This paper presents the results of growing Bi2Sr2CaCu2O8+δ single crystal superconductors by means of traveling  solvent floating zone (TSFZ) method in various atmospheres, namely in air and in oxygen (O2) of 1 and 2.5 bar. Variations of oxygen contents due to different atmospheres in the growing process lead to a variety of molar compositions of the as-grown crystals as well as formation of impurity phases. It is found from the result of sample characterization that the incrcase of oxygen content in the crystal lowers its critical temperature (Tc) and anisotropy (γ). Further the lowering of anisotropy incrcases the second peak field (H2p) and causes a shift of the irreversibility line (Hirr) to the higher temperature and magnetic field in the H-T phase diagram, signifying the enhancement of vortex pinning effect due to increasing concentration of oxygen dopant.
Linear Potential Sweep Voltammetry in Conjunction with Small Amplitude Cyclic Voltammetry Study for Chalcopyrite-Xanthate Electrochemical Flotation System Arief Sudarsono
Journal of Mathematical and Fundamental Sciences Vol. 31 No. 3 (1999)
Publisher : Institute for Research and Community Services (LPPM) ITB

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Abstract. The present study was undertaken to investigate the electrochemical aspects of reactions on platinum, copper, and chalcopyrite aqueous xanthate solution interfaces by the small amplitude cyclic voltammetry (SACV) technique. In the technique, the potential of an electrode is swept linearly with time within very narrow potential limits. Typically a 10 to 20 mV peak-to-peak triangular potential excitation has been used. Characteristic parameters of the observed current-potential response loop, like apparent polarization resistance, was used to analyze the surface reaction mechanism in the flotation of chalcopyrite minerals. The analysis of the electrochemical interaction between platinum, copper and xanthate ions has also been carried out by using linear potential sweep voltammetry (LPSV) techniques in different xanthate concentrations. The voltammograms obtained on platinum appear due to the possibility of the formation of dixanthogen from the oxidation of xanthate ions, and the formation of copper-xanthate species from elecbochemical reactions between xanthate ions and copper. Studi Voltametri Penyapuan Potensial Linier Dikaitkan dengan Voltametri Siklus Amplitudo Kecil untuk Sistem Flotasi Elektrokimia Kalkopirit-xantatSari. Penelitian ini memberikan gambaran reaksi elektrokimia pada antarmuka elektroda platina, tembaga, dan kalkopirit di dalam larutan encer xantat. Penelitian dilakukan dengan metode SACV (Small Amplitude Cyclic Voltammetry), dengan rentang eksitasi potensial segitiga yang sangat kecil, yaitu 10 mV sampai 20 mV eksitasi dipakai untuk menganalisis mekanisme reaksi flotasi mineral kolkopirit. Untuk mempertegas hasil SACV penelitian dilanjutkan dengan metode LPSV (Linear Potential Sweep Voltammetry). Voltammogram yang diperoleh menggambarkan terbentuknya dixantogen di permukaan elektroda platina, dan terbentuknya senyawa tembaga-xantat karena adanya reaksi permukaan antara ion xantat dengan tembaga.
Efek Perlakuan Rubratoksin B pada Tahap Praimplantasi terhadap Perkembangan Embrio Praimplantasi dan Fetus Mencit (Mus musculus) Swiss Webster Ramadhan Sumarmin; Tien W. Surjono; Sri Sudarwati
Journal of Mathematical and Fundamental Sciences Vol. 31 No. 3 (1999)
Publisher : Institute for Research and Community Services (LPPM) ITB

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Sari. Rubratoksin B adalah metabolit sekunder yang dihasilkan oleh Penicillium rubrum dan Penicillium purpurogenum, yaitu kapang yang acapkali terdapat sebagai pencemar serealia, terutama pada bahan makanan dan pakan ternak. Rubratoksin B dosis tunggal 0,8 dan 0,9 mg/kg berat badan diberikan secara intraperitoneal pada mencit Swiss Webster umur kebuntingan 0 hari atau 2 hari (tahap praimplantasi). Mencit kontrol hanya diberi propilen glikol sebagai pelarut rubratoksin B. Efek perlakuan terhadap perkembangan embrio praimplantasi diamati pada umur kebuntingan 3,5 hari, sedangkan terhadap fetus pada umur kebuntingan 18 hari. Hasil pengamatan menunjukkan bahwa perkembangan embrio praimplantasi terhambat, ditandai oleh berkurangnya jumlah blastosista akhir dan jumlah sel penyusunnya, rerta masih adanya tahap perkembangan awal. Pada tahap pascaimplantasi tampak bahwa jumlah implantasi dan jumlah fetus hidup menurun, kematian intrauterus meningkat, dan muncul kelainan berupa langit-langit bercelah pada fetus. Secara umum, hasil pengamatan yang diperoleh berbeda nyata dari kontrol dan sejalan dengan besarnya dosis rubratoksin B yang diberikan. Pada perlakuan umur kebuntingan 0 hari, embrio lebih banyak terhambat pada tahap 1-8 sel dan morula tidak mampat, sedangkan pada perlakuan umur kebuntingan 2 hari terjadi pergeseran hambatan ke tahap yang lebih tua, terutama pada morula mampat. Terbukti bahwa perlakuan rubratoksin B pada tahap praimplantasi menghambat perkembangan embrio praimplantasi yang mengakibatkan penurunan jumlah implantasi dan jumlah fetus hidup, serla mampu memunculkan kelainan perkembangan pada fetus. Effects of Preimplantation Treatments of Rubratoxin B on the Development of Preimplantation Embryos and Fetuses of Swiss Webster Mouse (Mus Musculus)Abstract. Rubratoxin B is a secondary metabolite of Penicillium rubrum and Penicillium purpurogenum, which moulds are often contaminating cereals, particularly food and feed. Single dosages of rubratoxin B 0.8 and 0.9 mg/kg body weight were administered intraperitoneally to Swiss Webster mice on day 0 or day 2 of gestation (preimplantation stage). Control mice were given propylene glycol only as rubratoxin B solvent. The effects of those treatments on preimplantation embryos were observed on gestation day 3.5, whereas those on fetuses were observed on day 18 of gestation. The results revealed that the development of preimplantation embryos was inhibited, shown by the decreased number of late blastocysts and the presence of earlier developmental stages. In the postimplantation stage these occurred: reduction in the number of implantation sites and live fetuses, increased intrauterine death, and cleft palate in the fetuses. In general, the results of the parameters obtained differed significantly compared to the controls and were dose related. In the treatment on gestation day 0, most of the preimplantation developmental delays occurred at earlier stages, i.e. 1-8 cells stage and uncompacted morulae, whereas in the groups treated on gestation day 2 inhibition shifted to older stages, predominantly at compacted morulae. It is concluded that preimplantation treartments of rubratoxin B inhibit the preimplantation development of the embryos, and consequently decrease the number of implantation sites, as well as the number of live fetuses, and is able to induce fetal malformation. 
Minimisasi Riak Arus Keluaran Penyearah Daya-besaran dengan Menggunakan Filter Aktif Pekik Argo Dahono
Journal of Mathematical and Fundamental Sciences Vol. 31 No. 3 (1999)
Publisher : Institute for Research and Community Services (LPPM) ITB

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Sari. Suatu metode baru untuk meminimisasi riak arus keluaran penyearah daya besar dengan menggunakan filter aktif diusulkan dalam tulisan ini. Karena filter aktif terhubung parallel dengan beban, maka kapasitas arus filter aktif yang diperlukan menjadi sangat kecil, yaitu sebesar riak arus yang akan dikompensasi. Selain itu, karena filter aktif dihubungkan seri dengan filter kapasitor yang ada, maka kapasitas tegangan filter aktif juga sangat kecil, yaitu sebesar riak tegangan yang dikompensasi. Teknik kendali filter aktif yang diusulkan dijelaskan dalam tulisan ini. Validitas metode yang diusulkan diuji dengan simulasi dan percobaanOutput Current Ripple Minimization of High-Power Rectifiers by using Active FilterAbstract. A new method to minimize the output current ripple of high-power rectifiers by using a dc active power filter is presented in this paper. Because the active filter is connected in paralled to the load, the current rating of the filter is very small, that is as small as the ripple which is going to be compensated. Moreover, because the active filter is series connected to the existing passive filter capacitor, the voltage rating of the active filter is also very small, that is as small as the voltage ripple which is going to be compensated. A control technique for the active filter is proposed in this paper. Validity of the proposed method is verified by simulated and experimental results.
Analisis Penggunaan Autotrafo Penggeser Fasa sebagai minimisator Harmonisa Arus di Sistem Distribusi Tenaga Listrik Syafrudin Syafrudin; Pekik A. Dahono; Sukisno Sukisno; T.M. Soelaiman
Journal of Mathematical and Fundamental Sciences Vol. 31 No. 3 (1999)
Publisher : Institute for Research and Community Services (LPPM) ITB

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Sari. Meningkatnya aplikasi beban nonlinier di sistem distribusi tenaga listrik telah menyebabkan arus sistem menjadi sangat terdistorsi dengan kandungan harmonisa arus yang sangat tinggi (THD). Persentase THD arus sistem yang tinggi dapat menyebabkan beberapa persoalan harmonisa yang serius. Tulisan ini mengusulkan metode baru untuk meminimisasi harmonisa arus di sistem distribusi tenaga listrik, yaitu dengan menggunakan autrafo penggeser fasa sebagai minimisator.Dalam kasus ini, autotrafo bertindak sebagai penggeser sudut fasa tegangan suplai beban. Akibat penggeseran sudut fasa ini, beberapa komponen arus harmonisa yang signifikan pada sisi sumber tegangan sistem dapat dieleminir, sehingga harmonisa arus yang terdapat di sistem menjadi sangat minim. Secara detail, mekanisme minimisasi harmonisa arus sistem dengan menffunakan autotrafo dijelaskan, dan diberikan beberapa konfigurasi autotrafo penggeser fasa yang dapat digunakan sebagai minimisator harmonisa arus sistem. Hasil eksperimen laboratorium diberikan untuk menunjukkan validitas metode yang diusulkan. Analysis of Phase Shifting Autotransformer as Current Harmonic Minimisator on Power Distribution SystemAbstract. The increasing use of nonlinear loads has made the currents in power distribution system highly distorted with high level harmonic currents content (TIID) and created serious harmonics problems. This paper proposed a new method to minimize current harmonics in power distribution system by using phase shifting autotransformer. The loads of system are devided into two parts which are supplied by autotransformer with 30° phase shifting. The effects of the phase shifting which causes harmonic currents are cencelled, and the resulting currents harmonic in power distribution system are minimized. Detailed mechanism of current harmonic minimization is presented. Several configurations of phase shifting autotransformer are discussed and compared. The influence of load operating conditions are discussed. Experimental results are shown to verify this proposed method.

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