Journal of Mathematical and Fundamental Sciences
Not a member yet
737 research outputs found
Sort by
MHD Free Convective Flow along Vertical Oscillatory Plate with Radiative Heat Transfer in the Presence of Hall Current and Heat Source
Get PDFMHD free convective flow with oscillations of an infinite non-conducting vertical flat surface through a porous medium with Hall current in a rotating system was studied. The governing equations of the model were converted into dimensionless form. Analytical solutions for velocity and temperature were obtained with the help of the Laplace transform method. Graphs and tables are used in this paper to show the influence of various parameters on temperature, skin friction and velocity. It was observed that changes in plate oscillation, porous medium, radiation and Hall current have significant effects on fluid motion. Further, the skin friction near the surface is increased by the radiation parameter. The results obtained have large implications in the engineering and science fields
Polyelectrolyte Complex (PEC) of the Alginate-Chitosan Membrane for Immobilizing Urease
Get PDFPEC of the alginate-chitosan membrane as supporting material for immobilizing urease was produced. This study aimed to develop a supporting material for enzyme immobilization that has high stability, a fast response time and an easy and relatively inexpensive preparation procedure. An alginate-chitosan PEC membrane was produced by reacting alginate hydrosol and chitosan (1:1 in mass) at pH 5.28, followed by mixing and drying at room temperature. The FTIR spectra, XRD patterns and SEM assay confirmed that alginate-chitosan PEC was obtained. The color change of the BTB indicator proved that urease was trapped in the cavities of the alginate-chitosan PEC membrane while the immobilized urease still showed catalytic activity. Thus, the membrane of alginate-chitosan PEC has good characteristics as a matrix for urease immobilization
Effects of Substrate Temperature on Vacuum Deposited Thin Film of Disperse Red 1 on ITO Glass
Get PDFAbstract. Highly crystalline thin films of photorefractive Disperse Red 1 (DR 1) molecule have been fabricated on clean substrate of ITO (indium tin oxide) glass by means of physical vapor deposition at various substrate temperatures. In addition to molecular orientation and organization revealed by their XRD and FTIR spectral characteristic and the enhancement of those effects by substrate temperature, further analysis of FTIR spectrum around nitrobenzene absorption band indicates the formation of strong hydrogen bond resulting in a head-tail stacking of the molecules. The deposited films also show systematic reduction of light absorption in the visible region with increasing substrate temperature. This modification of the optical property is clearly favorable for long wavelength photonic applications of DR1 film. Pengaruh Suhu Substrat pada Film Tipis 'Disperse Red 1' yang Dideposisi pada Gelas ITO dalam VakumSari. Dalam eksperimen ini telah berhasil diperoleh melalui proses deposisi vakum sejumlah film tipis bahan fotorefraktif dari molekul "Disperse Red 1" (DR1) dengan krisalinitas tinggi di atas substrat gelas ITO ("indium tin oxide") pada berbagai suhu. Selain efek orientasi dan organisasi molekul yang ditunjukkan oleh karakteristik spectra XRD dan FTIR bersangkutan serta peningkatan efek tersebut dengan suhu substrat, analisis lebih lanjut dari data FTIR di sekitar pita absorpsi nitrobenzene telah mengungkapkan tanda embentukan ikatan hydrogen yang kuat yang menghasilkan susunan "head-tail" yang bertumpuk. Film yang terdeposisi juga memperkihatkan pengurangan absorpsi cahaya secara sistematik di daerah tampak, seiring dengan peningkatan suhu substrat. Perubahan sifat optik ini jelas bermanfaat bagi aplikasi film DR1 untuk devais fotonik dalam daerah gelombang panjang
Beban Kerut pada Pelat Sandwich Anisotropik
Get PDFSari. 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
Adaptive Algorithm for Virtual Connection on Feedback-Based Flow Control in WAN-ATM Network
No full textAlgoritma 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
Artocarpin ad Heteroflavanone-A, Two Bioactive Flavonoids from Artocarpus champeden
No full textSuatu senyawa flavon terisoprenilasi, yaitu 3-(y,y-dimetilalil)-6-(3-metil-1-butenil)-7-metoksi-5,2, 4-trihidroksiflavon atau artokarpin (1), bersama-sama dengan suatu senyawa flavanone langka, yakni 5-hidroksi-7,2,4,6-tetrametoksiflavanon atau heteroflavanon-A (2); telah ditemukan masing-masing pada kayu dan kulit batang tumbuhan Artocarpus champeden Spreng (Moraceae), suatu tumbuhan pangan yang endemik untuk Indonesia dan dikenal dengan nama cempedak. Struktur molekul kedua senyawa tersebut telah ditetapkan berdasarkan data fisika dan spektroskopi. Kedua senyawa flavonoid ini menghambat transportasi asam amino leusin melalui membran usus ulat sutera Bombyx mori, sedangkan artokarpin (1) juga menunjukkan toksisitas yang tinggi terhadap udang Artemia salina. Artocarpin ad Heteroflavanone-A, Two Bioactive Flavonoids from Artocarpus champedenAn isoprenylated flavone, 3-(γ,γ-dimethylallyl)-6-(3-methyl-1-butenyl)-7-methoxy-5,2',4'-trihydroxyflavone or artocarpin (1), together with rare flavanone derivative, 5-hydroxy-7,2',4',6'-tetramethoxyflavanone or heteroflavanone-A (2) were isolated from the wood and the tree bark of Arocarpus champeden Spreng (Moraceae), an endemic plant of Indonesia, locally known as cempedak. The structures of both compounds were elucidated based on physical and spectroscopic data. Both flavonoids inhibited the amino acid transport in Bombyx mori midgut, while artocarpin (1) also showed high toxicity against Artemia solina shrimp
Structure and Development of Laticifers in Embryos and Seedlings of Artocarpus heterophyllus Lam.
No full textPada Artocarpus heterophyllus, pemula latisifer dibentuk dalam embrio pada awal perkembangan kotiledon. Pemula latisifier tersebut terdapat di tepi luar prokambium di daerah nodus kotiledon. Vesikula dalam berbagai ukuran merupakan komponen yang paling jelas dalam pemula latisifier tersebut. Selanjutnya pemula latisifier memanjang dan tumbuh secara intrusive sejajar dengan sumbu embrio kea rah radikula dan kotiledon. Dalam latisifier terjadi pembelahan inti tanpa diikuti sitokinesis, menghasilkan protoplas embrio kea rah radikula dan kotiledon. Dalam latisifer terjadi pembelahan inti tanpa diikutin sitokinesis, menghasilkan protoplas berinti banyak. Latisifer bercabang ke arah korteks dan empulur. Lateks dibentuk di dalam sitoplasma dan disimpan di dalam vakuola. Struktur latisifer adalah tak beruas dan bercabang. Tidak terjadi anastomosis di antara sel-sel latisifer yang letaknya berdekatan. Plasmodesmata jarang ditemukan pada dinding sel latisifer. Structure and Development of Laticifers in Embryos and Seedlings of Artocarpus heterophyllus Lam.In Artocarpus heterophyllus, laticifer initials are formed in the embryo at the beginning of the development of the cotyledons. The laticifer initials are located at the outer periphery of the procambium at the cotvledonary node. Vesicles of various sizes are the most conspicuous components in the laticifer initial. At subsequent growth, laticifer initials elongate parallel to the axis of the embryo and then grow intrusively towards the radicula and cotyledons. Nuclear division is not followed by cytokinesis and therefore a multinucleate protoplast is produced. The laticifers branch towards the cortex and the pith. Latex was built in the cytoplasm and stored in the vacuole. The structure of the laticifer are non-articulated and branched. No anastomosis occurs between adjacent laticifer cells. Plasmodesmata are rarely seen in the laticifer walls
Perhitungan Gangguan Kilat pada Saluran Udara Tegangan Menengah
Get PDFSari. Perhitungan gangguan kilat saluran udara tegangan menengah baru dilakukan secara intensif pada tahun-tahun terakhir 1960an, antaral ain oleh Uehara dkk. (1968) dan Auer dkk. (1969). Perhitungan-perhitungan tersebut menggunakan model geometris dari saluran dan generator surja, misalnya yang dilakukan oleh Auer dkk. (1969). Berdasarkan teori-teori yang sudah dikembangkan oleh Rusck (1958), Whitehead (1977), Razevig (1979), dan lain-lain, penulis mencoba menguraikan suatu metode analitis yang sederhana dengan perhitungan tangan dengan menggunakan alat hitung elektronik. Abstract. The calculations of lightning outages of medium voltage overhead lines have not been intensively conducted until late in the 1960s, among others by Uehara et al (1968) and Auer et al (1969). Those calculations use a geometric model of the line and a surge generator as conducted by Auer et al (1969). Based on the theories developed by Rusck (1958), Whitehead (1977), Razevig (1979), and others, the writer tries to outline a simple analytical method that can be calculated manually by using an electronic calculator