The Effectivenes of Modeling Instruction Learning on Students’ Conceptual Understanding of Rotational Dynamic

Rotational Dynamics is one of the physics topics which is quite difficult for students. Several previous studies showed students’ difficulties on this topic, one of which is the aspect of students’ conceptual understanding. Modeling instruction is the effective approach to improve students’ understanding. This model is in line with constructivist theory and cognitive model theory. This research aimed to examine the effectiveness of modeling instruction that we developed to improve students' conceptual understanding of rigid body mechanics, where the knowledge of particle mechanics serve as anchor or bridging to develop model of rigid body. This research used mixed method with embedded experimental design. It used one group pretest-posttest design and involved 65 students of a high school in Malang as the subject. Data were gathered using test consisting of 17 multiple-choice items with explanation. The students’ scores were analyzed quantitatively using t-test and N-gain to measure the improvement of students’ understanding, while the students' reasons were analyzed qualitatively. The results showed the average students’ score increased from 1.62 to 9.92 with N-gain of 0.54 (in upper medium category). We concluded that the modeling instruction was effective to improve students’ conceptual understanding.

Analysis of Tsunami Inundation due in Pangandaran Tsunami Earthquake in South Java Area Based on Finite Faults Solutions Model

On July 17, 2006 an earthquake with a magnitude of 7.7 triggered a tsunami that struck 500 km of the coast in the south of the island of Java. The tsunami generated is classified as an earthquake tsunami because the waves generated were quite large compared to the strength of the earthquake. The difference in the strength of the earthquake and the resulting tsunami requires a tsunami modeling study with an estimated fault area in addition to using aftershock and scaling law. The purpose of this study is to validate tsunamis that occur based on the estimation of the source mechanism and the area of earthquake faults. Determination of earthquake source mechanism parameters using the Teleseismic Body-Wave Inversion method that uses teleseismic waveforms with the distance recorded waveform from the source between Whereas, tsunami modeling is carried out using the Community Model Interface for Tsunami (commit) method. Fault plane parameters that obtained were strike , dip , and rake with dominant slip pointing up to north-north-west with a maximum value of 1.7 m. The fault plane is estimated to have a length of 280 km in the strike direction and a width of 102 km in the dip direction. From the results of the tsunami modeling, the maximum inundation area is 0.32 km2 in residential areas flanked by Pangandaran bays and the maximum run-up of 380.96 cm in Pasir Putih beach area. The tsunami modeling results in much smaller inundation and run-up from field observations, it was assumed that the fault plane segmentation had occurred due to the greater energy released than the one from the fault area, causing waves much larger than the modeling results.

Reconstruction of High Resolution Medical Image Using General Regression Neural Network (GRNN)

Low image resolution has deficiencies in the diagnostic process, this will affect the quality of the image in describing an object in certain tissues or organs, especially in the process of examining patients by doctors or physicians based on the results of imaging medical devices such as CT-scans, MRIs and X-rays. Therefore, this study had developed a General Regression Neural Network (GRNN) type artificial neural network system to reconstruct a medical image so that the image has a significant resolution for the analysis process. The GRNN input layer uses grayscale intensity values with variations in the image position coordinates to produce an optimal resolution. There are four layers in this method, the first is input layer, the second is hidden layer, the third is summation, and the last layer is output. We examined the two parameters with different interval values of 0.2 and of 0.5. The result shows that the interval value of 0.2 is the optimal value to produce an output image that is identical to the input image. This is also supported by the results of the intensity curve of the RGB pattern matched between target and output.

Design of low-cost and simple reconstruction method for Three Dimensional Electrical Impedance Tomography (3D-EIT) Imaging

Electrical impedance tomography is a non-invasive imaging modality that uses the electrical conductivity distribution to reconstruct images based on potential measurements from the object's surface. The proposed study was to design and fabricate a low-cost and simple reconstruction method for 3D electrical impedance tomography imaging. In this study, we have been successfully developed 3 Dimensional Electrical Impedance Tomography (3D-EIT) system using 16 copper electrodes (Cu) to detect and reconstruct the presence of objects in the Phantom. 3D-EIT was developed using Phantom as a test object with PVC pipe material, with an inner diameter of 7.2 cm and a height of 5.4 cm. Electrodes were arranged in two rings, with each ring having eight electrodes arranged in a planar line. Furthermore, the Gauss-Newton algorithm and Laplace prior regularization were used to image reconstruction of objects inside the Phantom using voltage measurement produced from sequential pairs of neighboring electrodes. The voltage is obtained from the injection of a constant current of 1 mA at 20 kHz into the system's electrode pairs. The objects used in this research are PVC pipe, solid aluminum, PVC pipes filled with wax glue, and copper trusses. The results obtained show that the reconstruction results can provide information about the position, the electrical properties, and the shape of real objects. Finally, the system can detect the location, height, and electrical properties of objects for all variations of angle and height variations.

The Existence of Fourier Coefficients and Periodic Multiplicity Based on Initial Values and One-Dimensional Wave Limits Requirements

Physical systems in partial differential equations can be interpreted in a visual form using a wave simulation. In particular, the interpretation of the differential equations used is in the nonlinear hyperbolic model, but in its completion, there are some limitations to the stability requirements found. The aim of this study is to investigate the analytical and numerical analysis of a wave equation with a similar unit and fractal intervals using the Fourier coefficient. The method in this research is to use the analytical solution approach, the spectral method, and the finite difference method. The hyperbolic wave equation's analytical solution approach, illustrated in the Fourier analysis, uses a pulse triangle. The spectral method minimizes errors when there is the addition of the same sample grid points or the periodic domain's expansion with a trigonometric basis. Meanwhile, different ways offer a more efficient solution. Based on the research results, the information obtained is that the Fourier analysis illustrates the pulse triangle use to solve the solution. These results are also suitable for adding sample points to the same spectra. Fourier analysis requires a relatively long time to solve one pulse triangle graph to need another solution, namely the finite difference method. However, its use is still limited in terms of stability when faced with more complex problems.

Effect of Sintering and Concentration of Dymethylformamide on Surface Properties of Hydroxyapatite Coating on Titanium Substrate Fabricated by Electrophoretic Deposition

Hydroxyapatite (HAp) coating on metallic implant was developed to increase bioactivity of orthopaedic implant. In this work, hydroxyapatite was successfully deposited on commercially pure titanium (CP-Ti) substrate by electrophoretic deposition (EPD). This work aims to determine the effect of dimethylformamide (DMF) as dispersant for EPD suspension followed by heat treatment, on the surface morphology of the HAp coating. HAp powder was suspended in an ethanol-DMF solution with the amount of DMF designed at 0, 5, 10, and 15% per 100 mL suspension. EPD was then performed successfully on all samples. After EPD, the specimens were sintered at 800 °C for 120 minutes in argon atmosphere. Surface morphology, composition, and phase of HAp coating before and after sintering were characterized by Scanning Electron Microscope, Fourier Transform Infrared Spectrometer, and X-ray Diffractometer. X-ray and IR spectra confirmed that sintering had a little effect on the chemical structure and the phase of the deposited HAp. The morphology of the surface is denser across all samples and shows distinguishable features as the amount of DMF in the system was increased. The 15% DMF sample exhibits the mostly grooved surface after sintering. Further analysis showed that sintering reduced the EPD-related shrinkage on the surface and enhanced the size of the pores. Microstructural indication referring to previous research suggested that this type of microscopic surface is very sought after in promoting a good biological interaction between the implant and the host. Further testing must be done to confirm the effect of DMF-modified structure in living tissue.