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THE ANALITICAL SOLUTIONS OF THE LINEAR TWO CHANNELS DISSIPATION MODEL
Full text linkThe analytical solutions of the linear two channels dissipation model are presented in various forms. First we analyze the particular solutions of this model. Then the model is transformed into the Telegrapher Equation and further into the Klein Gordon Equation for which various families of solutions are known. The Fourier Transform is applied on the Telegrapher Equation, yielding solutions in Fourier representation. Finally we apply the method ofcharacteristics to find solutions of the initial value problem.Keywords : hyperbolic system, partial differential equation, exact solutio
FABRICATION OF ORGANIC LIGHT EMITTING DIODES (OLEDs) FOR FLAT PANEL DISPLAYS
Full text linkOrganic light emitting diodes (OLEDs) are thin film devices in which organic materials are sandwiched between two electrodes. These devices emit light when electricity is passed through them. OLEDs have gained much attention because their potential applications to full color flat panel displays. Generally, OLEDs are assembled using an heterojunction architecture between three or more organic molecular materials: an electron injection layer, the emitting one and finally the hole injection layer. There are two types of OLED devices, depend on the type of molecular materials used in the devices. The first type is Small Molecule OLED. The production of small-molecule OLEDs require vacuum deposition. The second type is Light-Emitting Polymer. In this technology, the organic thin films can be deposited by spin coating or by a technique derived from commercial inkjet printing. This paper discusses the fabrication of both types of OLEDs. A small molecule blue organic light emitting diode was fabricated using thermal evaporation system with ITO/2-TNATA/NPB/DPVBi:dopant/ Alq3/LiF/Al structure, where the emitting molecules is 4,4’-bis(2,2’-diphenylvinyl)-1,1’-biphenyl (DPVBi). The typical brightness, the power consumption and the turn-on voltage of the device were 30 cd/m2, less than 50 mW and 5.0 V respectively. For polymer light-emitting diode, device with structure of ITO/PHF/Al structure was fabricated, where PHF is poly (4, 4’-diphenylene diphenylvinylene). This device has turn-on voltage at 23.0 V. A reduction of turn-on voltage of this device is achieved by using a nanocomposite layer consisting of PHF and SiO2 nanoparticles as the emitting layer. A white OLED combines with colour filters is one of the approaches to obtained full colour flat screen display. White light emitting devices were fabricated with structure of ITO/PHF:rubrene/Al where the white light was optimized through variation of mixing concentrations of PHF and rubrene. The results show that the combination of 0.6 wt% PHF and 0.06 wt% rubrene produced the optimum white light at CIE coordinate of (0.31,0.31). The standard coordinate for white light is (0.33,0.33). The turn-on voltage of this device is 14.0 V and the brightness is 6541 cd/m2. The turn-on of this device was reduced to 8.0 V through an annealing process at 150°C.
Keywords : Organic light emitting diodes (OLEDs), small molecule device, polymer light-emitting diode, display
APPLICATION OF MICROCANONICAL TEMPERATURE TO THE SPIN CROSSOVER OF Fe-Co COMPOUNDS
Full text linkUsing the Rugh’s microcanonical approach to temperature we study the classical model of three dimensional spin-crossover of Fe-Co compounds. These compounds are characterized by magnetic ions that can be in a high-spin or low-spin state. We consider the case of diamagnetic low-spin state. The values of the magnetization average, and fraction of high-spin/low-spin are studied over a wide range of values for the system size, temperature, magnetic field, energy difference, nearest neighbor coupling and exchange interaction. We also address the metastability according to the relative values of interaction parameters and the phase diagram of the model.
Keywords: phase transition, dynamical temperature, spin crossove
PEMBUATAN, KARAKTERISASI DAN UJI AKTIVITAS KATALIS NiMo/Z DAN NiMo/Z-Nb2O5 PADA REAKSI HIDRORENGKAH FRAKSI SAMPAH PLASTIK MENJADI FRAKSI BENSIN
Full text linkActivity test of NiMo/active natural zeolite (Z) and NiMo/Z-Nb2O5 catalysts for hydrocracking of waste plastic fraction polyprophylene (PP) type were done. Catalysts were prepared by impregnation method, then were calcined at 500oC, oxidized and reduced at 400oC under nitrogen, oxygen and hydrogen stream, respectively. The characterization of catalysts including spesific surface area, average pore radius, and total pore volume were determined by gas sorption analyzer, amount of total acid sites was determined by gas sorption method, and acid site strength was confirmed by IR sepectroscopy. The hydrocracking process was carried out in a semi-flow reactor system at 360oC and catalyst/feed ratio 0.5 under hydrogen stream (150 mL/hour). The feed was vaporized from the pyrolisis reactor into the hydrocracking reactor. A liquid product was collected and analyzed by gas chromatography (GC) and gas chromatography-mass spectroscopy (GC-MS). The characterization results showed that spesific surface area, average pore radius, and total pore volume of the Z sample decreased after loading of the metal and Nb2O5. Amount of total acid sites of the catalysts were higher than that of the Z sample. The activity of catalysts followed the order of NiMo/Z>NiMo/Z-Nb2O5>Z (conversion of hydrocarbon C>12) and NiMoZ>NiMo/Z-Nb2O5>Z (total yield gasoline fraction). The selectivity of catalysts for C7-C8 product followed the order of NiMo/Z-Nb2O5>Z>NiMo/Z. Loading of Nb2O5 significantly affected the selectivity of C7-C8 product.
Keywords: activity, polyprophylene, catalyst, gasoline fractio
SOLIDIFICATION ANALYSIS OF BISMUTH BASED ALLOY IN CONTINUOUS CASTING PROCESS
Full text linkContinuous Casting is a manufacturing process for producing billets, slabs and flat products. It is used for casting non-ferrous and steel production to produce high quality products of slab or billet cast at reduced cost. A thin solidified metal shell is formed initially during continuous casting due to the intense cooling from the water cooled mould. Once the cast leaves the mould it goes through various cooling processes and in solid state will proceed to the further forming processes. To exploit the benefit of continuous casting process it is essential to develop close control of the production process. This is achieved through a good understanding of the influence of the various compositional and operational variables. The objective of the mathematical analysis presented here is to model the heat transfer during continuous casting of low melting point Bismuth alloy cast billets material for predicting the surface temperature. Good quality of the cast in conjunction with the surface quality of the cast is relied on the solidification temperature during continuous casting. In fact by simulating the solidification temperature of the continuous casting process through applying different operational casting parameters, the result are crucial for identifying the best operational casting parameters.Keywords: Continuous Casting, Solidification, Enthalpy Method, Simulatio
PARALLEL EXECUTION OF BLOCK RUNGE-KUTTA METHODS FOR SOLVING ORDINARY DIFFERENTIAL EQUATIONS
Full text linkThe objective of this paper is to exploit the favourable characteristics of block explicit Runge-Kutta and block diagonally implicit Runge-Kutta methods for sequential machines to parallel ones. Both methods are used to solve ordinary differential equations, codes based on the methods are execute in sequential and parallel. Numerical results based on the two modes of executions are tabulated and compared.Keywords: Block Explicit Runge-Kutta , Block Diagonally Implicit Runge-Kutta, sequential, parallel
KARAKTERISTIK BIODIESEL DARI MINYAK JELANTAH DAN SOLAR DI DALAM MESIN DIESEL
Full text linkTelah dilakukan penelitian karakterisasi biodisel dari minyak jelantah dan solar di dalam mesin diesel pada berbagai kecepatan putaran mesin (rpm). Pembuatan biodiesel (esterifikasi) dilakukan pada kondisi optimum yaitu suhu 55-60oC, katalisator NaOH 1%, metanol 20% dan waktu 1,5-2,0 jam. Biodiesel yang dihasilkan dengan spesifikasi tertentu dan solar dikarakterisasi menggunakan engine test bed, dimana mesin diletakkan pada suatu bantalan dan poros output mesin dihubungkan dengan sebuah poros dinamometer. Parameter yang diamati dalam penelitian ini adalah torsi, daya efektif dan pemakaian bahan bakar spesifik. Bahan bakar yang digunakan adalah solar murni, dan campurannya dengan biodiesel 5% (B5), 10% (B10), 15% (B15) dan 20% (B20). Hasil penelitian diperoleh bahwa torsi maksimal sebesar 121,163 Nm berada pada putaran 1950 rpm dengan bahan bakar solar murni dan campuran biodiesel B20. Daya efektif terbesar 35,288 kW pada putaran 3000 rpm untuk bahan bakar semua jenis campuran biodiesel. Konsumsi bahan bakar spesifik paling ekonomis sebesar 0,279 kg/kW-jam pada putaran 1650 rpm untuk bahan bakar solar murni dan campuran biodiesel B10.Kata kunci : biodiesel, solar, mesin diese
THE RECONSTRUCTION OF MULTIPLE ACOUSTIC SOURCES THAT FULFILL THE PREDETERMINED SOUND LEVEL ON A CERTAIN TARGET FIELD LOCATION
Full text linkoai:jurnal.ugm.ac.id:article/13744In noise level control, the surface acoustic property of noise sources is one of important initial information. The noise control will be more efficient and effective if we know not only the properties of noise source surface, but also know the most influential surface area to a certain target field location. If the dominant surface area of noise sources has been known, further treatment can be applied to the dominant surface area only. In order to be able to apply an appropriate further treatment, we must know how much acoustic quantity on the dominant area must be changed. Solving this problem needs inverse technique and optimization to obtain an optimal noise source characteristic. This paper presents a reconstruction method of multiple acoustic sources that fulfill the predetermined condition on a certain target field location using Boundary Element Method and Conjugate Gradient method. Test cases for radiation of multiple vibrating spherical shape sources in a certain area have been done for verifying the algorithm. Simulation results show that the proposed method could be used to reconstruct an optimal surface pressure of multiple acoustic sources. Keywords: acoustic, boundary element method, multiple source reconstructio
RESISTIVITY AND REFRACTION SEISMIC MAPPING IN PRAMBANAN TEMPLE AREA
Full text linkDue to the Yogyakarta’s earthquake of 5.9 Richter scale in May 2006, the Prambanan temple (Siwa temple) has deformation up to 5 cm in the body stone, and some of the surface rocks in the upper, middle, and foot of the temple body are collapsed. The effect of the earthquake will influence the stability of the rock or soil in the subsurface. Thus, It is very importance to study the condition of the subsurface rock of the Prambanan site by geophysical method, i.e., geo-electric and seismic technique. The acquisitions of resistivity and seismic data are carried out in January 16-17, 2007. Five seismic and resistivity lines have been measured and the Hagiwara method has been applied to estimate the interface depth and velocity from the seismic data. The resistivity configuration system of in line position is dipole-dipole arrangement. The processing and the modeling use RES2DMOD and RES3DMOD. Two points are measured by vertical electrical sounding (VES) in Schlumberger configuration (between Siwa and Nandi temples) to know the resistivities distribution of soil vertically. The Progress 3.0 software was used for data processing. The results show that the bodies of temples are supported by hard rock velocity is 400-500 m/s and the resistivity is > 200 ohm-m, whereas the depth of the hard rock is (4-8) m from the surface. The thickness of the seal soil is about 8 m in the south area and 4 m in the north area. The low resistivity in front of the Siwa, Wisnu and Brahma temple at east side, was estimated as a drainage system of the Prambanan temple area. For more than 13 m depth finds water saturated sandstone.
Keywords: Prambanan Temple, VLF, Seismi