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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 4 Documents
 1 
Search results for , issue "Vol. 30 No. 2 (1998)" : 4 Documents clear
A New Approach to Analysis of Inverter Currents Pekik Argo Dahono
Journal of Mathematical and Fundamental Sciences Vol. 30 No. 2 (1998)
Publisher : Institute for Research and Community Services (LPPM) ITB

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Abstract

In this paper, a new approach to analysis of the average and rms currents in inverter switching devices and the rms value of the ripple component of inverter input current is presented. The proposed approach is based on the probability with which the inverter switching devices receive ON signals which can be obtained from the average value of the phase-to-dc midpoint voltages. As the knowledge of the exact switching pattern is not required, this approach is especially useful for inverters in which the exact switching patterns can not be predetermined. To show the general applicability of the proposed approach, the expressions for the average and rms currents in switching devices and the rms value of the ripple component of input current of three-phase hysteresis current-controlled and PWM inverters are derived. Experimental results are included to show the validity of the proposed method. Suatu Pendekatan Baru untuk Analisis Arus-arus InverterDalam makalah ini dipresentasikan, suatu pendekatan baru umtuk analisis arus rata-rata dan rms pada komponen-komponen switching inverter dan nilai rms riak arus masukan inverter. Pendekatan yang diusulkan berbasis pada peluang komponen-komponen switching inverter menerima sinyal ON yang didapatkan dari nilai rata-rata tegangan fasa keluaran. Karena pengetahuan detil tentang pola switching inverter tidak diperlukan, metoda yang diusulkan sangat cocok untuk analisis arus-arus pada inverter dengan pola switching yang tidak bisa ditentukan. Untuk menunjukkan luasnya daerah penerapan, persamaan-persamaan arus rata-rata dan rms komponen switching dan nilai rms riak arus masukan dari inverter yang menggunakan pengendali arus jenis hysteresis dan yang menggunakan pengendali PWM diturunkan. Hasil pengukuran disertakan untuk menunjukkan validitas metoda yang diusulkan.
Adaptive Algorithm for Virtual Connection on Feedback-Based Flow Control in WAN-ATM Network F. Ahmadi Djajasugita; Rendy Munadi
Journal of Mathematical and Fundamental Sciences Vol. 30 No. 2 (1998)
Publisher : Institute for Research and Community Services (LPPM) ITB

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Abstract

Algoritma pengendalian aliran yang bersifat adaptif dapat diterapkan pada jaringan ATM wilayah luas guna mengalokasikan kebutuhan lebar pita pada hubungan virtual. Pengendalian aliaran menggunakan mekanisme control lup tertutup, yaitu suatu mekanisme kontrol yang bersifat reaktif dan secara dinamis, mengatur kecepatan transmisi sel yang diizinkan untuk setiap hubungan virtual dengan menggunakan informasi umpan balik dari jaringan. Informasi umpan balik berupa bit yang dapat mengidentifikasi apakah panjang antrian di buffer berada di atas atau di bawah batas ambang yang diberikan. Dengan bit indikasi ini kecepatan sumber pengiriman dapat dikendalikan. Penelitian yang telah dilakukan sebelumnya terbatas pada jumlah hubungan sebanyak 24VC dan kecepatan transmisi 155 Mbps dengan batas ambang buffer 6.5 sel. Karena itu, dilakukan penelitian jika jumlah hubungan bertambah hingga 100 VC dan kecepatan transmisi 600 Mbps dengan batas ambang buffer dalam rentang yang lebar. Hasil simulasi algoritma adaptif menunjukkan bahwa dengan menggunakan kriteria kestabilan terhadap hubungan virtual tunggal akan diketahui rentang penggunaan parameter rasio penguatan terhadap peredaman yang tepat sehingga untuk hubungan virtual banyak akan lebih mudah ditunjukkan sifat keadilan terhadap setiap hubungan. Sifat kekokohan ditunjukkan melalui simulasi, yaitu dengan menambah jumlah hubungan yang mungkin dapat dilayani. Dari respon kecepatan aggregate terlihat bahwa terjadi penurunan pemanfaatan lebar pita jaringan (<90%). Keadaan ini dapat diatasi dengan memperbesar kecepatan transmisi, menambah waktu update, dan menambah panjang ambang batas antrian di buffer. Adaptive Algorithm for Virtual Connection on Feedback-Based Flow Control in WAN-ATM NetworkAdaptive flow control Algorithm can be applied into wide area ATM network to allocate lebar pita to virtual connection. Flow control uses closed loop control mechanism, i.e, a reactive control mechanism which dynamically controls permissible transmission speed for any virtual connection by using feedback information of the network. Information of the network is in the form of bit that can identify whether a queue length in buffer is above or below a given threshold. By this indication bit the source of cell sending can be controlled. The earlier investigation was limited to 24 VC connection and in 155 Mbps transmission speed with 6.5 cells buffer threshold. Considering that it was not enough, a further investigation was carried out with increasing connection up to 100 VC, 600 Mbps transmission speed, and buffer threshold in a wide range. Adaptive algorithm simulation results showed that by using stability criterion on single virtual connection we found the range of gain ratio parameter used on proper damping, hence, fairness can be made easier in multiple virtual connections. There are two parameters - each is important for every virtual connection, i.e minimum bandwith parameter and weight factor to gain bandwith share that provided by the network. Proper selection on the two parameters gives different service. Aggregate speed response showed that there is degradation of network bandwith use (<90%). This situation can be overcome by increasing the transmission speed, lengthening update time, and enlarging the buffer threshold.
Optimisation of Image Interpretability and Geometric Accuracy of Airborne Videography Irawan Sumarto
Journal of Mathematical and Fundamental Sciences Vol. 30 No. 2 (1998)
Publisher : Institute for Research and Community Services (LPPM) ITB

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Abstract

Airborne video images which have several advantages over satellite images and aerial photographs were captured over some selected areas. After they were refined to increase their interpretability, the images were assessed in accordance with the existing map accuracy specifications. Four algorithms of image refinement were tested. These include projective, row duplication, row interpolation and statistical correlation function. Numerous test points were selected on the image and their coordinates were compared to their ground positions. The results suggest that a solid-state video camera can provide images that are sufficiently accurate for medium-scale topographic mapping.Ketelitian Geometrik dan Optimalisasi Tingkat Ketajaman Citra VideoCitra video, yang mempunyai beberapa keuntungan dibandingkan dengan citra satelit dan foto udara, diperoleh dari hasil penerbangan di atas suatu daerah. Setelah citra tersebut direstorasi untuk meningkatkan tingkat ketajamannya, dilakukan proses fotogrametri untuk mengevaluasi tingkat ketelitian geometriknya. Restorasi citra dilakukan secara digital dengan empat macam teknik, yaitu projektif, interpolasi baris, duplikasi baris, dan kolerasi statistic. Evaluasi keteletian geometrik dilakukan dengan membandingkan koordinat sejumlah titik yang diamati pada citra video dengan posisi seharusnya di lapangan. Hasil pengujian mengindikasikan bahwa kamera video dapat digunakan pada pemotretan udara bagi keperluan pemetaan topografi skala menengah.
Three Flavan-3-ols from Artocarpus reticulates Sjamsul Arifin Achmad; Murniana Murniana; Silvester Sigit Udjiana; Euis Holisotan Hakim; Lukman Makmur; Norio Aimi
Journal of Mathematical and Fundamental Sciences Vol. 30 No. 2 (1998)
Publisher : Institute for Research and Community Services (LPPM) ITB

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Abstract

Tiga senyawa turunan flavan-3-ol, yakni afzelekin-3-O-a-L-ramnosida (1), katekin (2), dan afzelekin (3), telah ditemukan pada kulit batang dan kulit akar tumbuhan Artocarpus reticulatus Miq. (Moraceae), suatu tumbuhan langka yang berasal dari Sulawesi dan endemik untuk Indonesia, serta dikenal dengan nama daerah maumbi. Struktur molekul ketiga senyawa tersebut telah ditetapkan berdasarkan data fisika dan spektroskopi. Three Flavan-3-ols from Artocarpus reticulatesThree flavan-3-ol derivatives, namely afzelechin-3-O-α-L-rhamnoside (1), catechin (2) and afzelechin (3), were isolated from the tree and the root barks of Artocarpus reticulaltus Miq. (Moraceae), a rare species found in Sulawesi and endemic to lndonesia, locally known as maumbi. The structures of all these compounds were elucidated based on physical and spectroscopic data.

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