The concentration and wavelength-dependent refractive index of sugar solution have been determined using Sellmeier Equation. The equations describe the refractive index as a function of wavelength parameter. They could be generalized as a function of material concentration by investigating the characteristic of their Sellmeier constants A and B. The three wavelengths used to identify the refractive index of sugar solutions were 455 nm, 525 nm, and 633 nm, while the concentration of the sugar solution ranged from 0 to 40%. This paper reported in this research performed the empirical expression of concentration-dependent of the sugar solution. The A and B Sellmeier constants were the main subjects to be concerned. A constant has a linear relationship with the sugar solution at 15% concentration to 40%. Under a concentration of 15%, the refractive index is quadratic towards engagement. The sellmeier B constant has a quadratic relation characteristic below the attention of 15%. Above 15%, the constant B and concentration of sugar solution were associated with the 4th order polynomial equation.
It has been determined by molecular dynamics simulation method the parameter potentials (
ε, σ
) of the Lennard-Jones potential based on the cohesive energy value for some pure metals. The LAMMPS molecular dynamics software was used to simulate and calculate the cohesive energy of the metals. To determine the best value of (
ε, σ
) we verified all calculations using the available experimental data of cohesive energy of the metals. The discrepancy of cohesive energy between simulation and experimental data were limited not more than 0.1 % to get best value of the Lennard-Jones parameter potentials (
ε, σ
).
Hard Disk Drive (HDD) as a data storage device when operated with high temperatures (around 66oC), its function will be constrained. The CoFe alloys have a large coercivity field and can be patterned in very small sizes that are suitable for HDD devices. In this study, Co1-x Fex cube alloy was used (x = 0.25; 0.30; 0.50; 0.75). Samples were treated with temperature changes to get the Curie temperature. The coercivity field value is obtained by giving the external field and temperature below Curie temperature and also above Curie temperature to the samples. The VAMPIRE software is a micromagnetic simulation program based on atomistic models. The results showed that Curie’s temperature decreased when Co content increased. The composition of Co0.25 Fe0.75 has the highest Curie temperature that is equal to 1075 K. The temperature Curie is not affected by the size of the cube. When the sample is given a temperature rise below the Curie temperature, the value of the coercivity field decreases. The value of the coercivity field is very difficult to determine when the temperature used is above the Curie temperature. The percentage of composition does not affect the coercivity field value. Therefore, cube-shaped CoFe material is very suitable for use as a material data storage device operated at temperatures below the Curie.
Indonesia’s geographical location supports the existence of various coffee commodities. As a plantation commodity, coffee has a high economic value. Coffee has a lot of substance that is beneficial to the body, one of is caffeine that serve to increase the stamina. Caffeine is naturally present in many types of plants as secondary metabolism. This research was done to know the content of caffeine in a local Arabica pure coffee with their variation of roasted temperatures. Coffee roasting is a stage of processing coffee beans into ready to grind, which can produce variations in the taste and content of coffee. The roasting process uses a roasting machine that automatically adjusts the roast temperature. Variations of roasted coffee are ground and used as a solution to determine the caffeine content. The determination of the coffee content is carried out using the spectrophotometric method, which measures the absorbance of caffeine in solution when it is passed by electromagnetic waves in the UV-Vis spectrum. The test results showed that the highest caffeine content was on samples of pure Arabica coffee with a roasted temperature of 195°C to 215°C with five levels of coffee roast. Caffeine content in sequential 3.217% and 2.597%.
Solar cell efficiency as a function of the energy gap has been simulated by calculating the output current characteristics of the devices based on the distribution of charge carriers, obtained from the solution of the Poisson equation and the Continuity equation. The hydrogenated amorphous silicon (a-Si:H) based solar cell, has simulated in the form of one-dimensional single junction p/i/n. The junction structure of a-SiC:H/a-Si:H/a-Si:H designed have the thickness of 0,015 μm/0,550 μm/0,030 μm, respectively. For simulation, the energy gap has considered constant in the p and n layers, whereas the i layer varies according to the empirical data of energy gap obtained from the deposition parameters of filament temperature. Simulations performed using the finite element method supported by FEMLAB software. Based on simulation results, obtained the highest efficiency of 9.35% corresponds to the lowest energy gap data of 1.706 eV for layer i. This appropriates to the filament temperature of 800oC and subsequently used as the optimum deposition parameters of the material. Keyword: Energy gap, efficiency, FEM, solar cell, hydrogenated amorphous silicon
The properties of GaAs material in zinc blende type was calculated using Hiroshima Linear Plane Wave program based on the Density Functional Theory. This calculation aims to determine electronic properties of GaAs material are based on Density of States and energy band structure. This simulation’s results are DOS shows that hybridization of s orbital of Ga with s orbital of As provides covalent properties. The simulation of energy band structure from GaAs material indicates that semiconductor properties of GaAs is direct band gap. The energy band gap results obtained for GaAs is 0.80 eV. The computational result of the energy band gap calculation form HiLAPW has better accuracy and prediction with good agreement within reasonable acceptable errors when compared to some other DFT programs and the results of the experimental obtained.
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