Siti Nurul Khotimah

Measuring leaf chlorophyll concentration from its color: A way in monitoring environment change to plantations

Leaf colors of a plant can be used to identify stress level due to its adaptation to environmental change. For most leaves green-related colors are sourced from chlorophyll a and b. Chlorophyll concentration is normally measured using a spectrophotometer in laboratory. In some remote observation places, it is impossible to collect the leaves, preserve them, and bring them to laboratory to measure their chlorophyll content. Based on this need, measurement of chlorophyll content is observed through its color. Using CIE chromaticity diagram leaf_color information in RGB is transformed into wavelength (in nm). Paddy seed with variety name IR-64 is used in observation during its vegetation stage t (age of 0-10 days). Light exposure time τ is chosen as environmental change, which normally should be about 12 hours/day, is varied (0-12 hours/day). Each day sample from different exposure time is taken, its color is recorded using HP Deskjet 1050 scanner with 1200 dpi, and its chlorophyll content is obtained from a...

2-D granular model of composite elasticity using molecular dynamics simulation

Composite of two kinds of grains is modeled in two-dimension and the elasticity is calculated using molecular dynamics method implementing Gear predictor-corrector of fifth order. It has been observed that same composite concentration can be represented by several configurations of the two kinds of grains. Simulation results show a peak or maximum value of a parameter proportional to Youngs modulus, which quantitatively agrees with reported experiment results. Ratio of k1/k2 used in simulation has influenced average value of the mentioned parameter monotonically. It means that increase of the ratio will also increase the parameter.

Studying Brazil-Nut Effect History Line using Disk- Formed Objects, Scanner, and Web Browser

Grains configuration snapshots of Brazil-nut effect (BNE) in two-dimension are physically modeled using disk-formed objects, e.g., buttons and magnetic pin. These BNE configurations are artificially designed to mimic the real ones observed in experiments. A computer scanner is used to capture the configurations. Obtained images are then digitized using web browser running an HTML equipped with a JavaScript code, which is built mainly only for this work. From digitization process all grains positions (granular bed and intruder) are obtained, which is later analyzed using the simplest model, i.e., potential energy. Since the minimum energy principle (MEP) suggests that a closed system should go to its state with minimum internal energy, our BNE system must also obey it. Evolution of only the intruder seems to violate MEP but not for the whole system. Grains compaction plays an important role, so that the system can achieve its configuration with minimum potential energy.

Molecular Dynamics Simulation of Smaller Granular Particles Deposition on a Larger One Due to Velocity Sequence Dependent Electrical Charge Distribution

Deposition of smaller granular particles on a larger nucleus particle has been simulated in two‐dimension using molecular dynamics method. Variation of sequences of velocity of deposited particles is conducted and reported in this work. The sequences obey a normal distribution function of velocity with the same parameters. It has been observed that for velocity in range of 0 to 0.02 the densest deposited site (15–17 % number of grains) is located at about angle π/4 where location of injection point is π/4. And the less dense is about π/4 + π/4. Different sequences give similar result.

Budding yeast colony growth study based on circular granular cell

Yeast colony growth can be modelled by using circular granular cells, which can grow and produce buds. The bud growth angle can be set to regulate cell budding pattern. Cohesion force, contact force and Stokes force were adopted to accommodate the behaviour and interactions among cells. Simulation steps are divided into two steps, the explicit step is due to cell growing and implicit step for the cell rearrangement. Only in explicit step that time change was performed. In this study, we examine the influence of cell diameter growth time and reproduction time combination toward the growth of cell number and colony formation. We find a commutative relation between the cell diameter growth time and reproduction time to the specific growth rate. The greater value of the multiplication of the parameters, the smaller specific growth rate is obtained. It also shows a linear correlation between the specific growth rate and colony diameter growth rate.

Study of Internal Response of Epoxy due to Compressive Load via Experiment and Simulation Using Abaqus FEA Software

Epoxy is widely used primarily as a matrix material in the manufacture of Polymer Matrix Composites (PMC). Epoxy behavior under compression load has to be understood before the mechanical behavior of PMCs can be accurately predicted. Simulation model combined with experiment and image analysis are used to investigate internal response of epoxy resins polymeric materials subject to compressive loads. To investigate epoxy response to compressive load, small carbon-based material rods are inserted in the epoxy. The samples are held in one side and subjected to compressive load on the other side. All the samples swell at load sides. Image analysis on the carbon-based rods figures out the internal response, which seems to be isotropy in lateral direction. The results are compared to simulation results using Abaqus FEA. Similar condition is obtained when a brittle thin material is stuck to the top of the model.

Compressive elastic modulus of natural fiber based binary composites

The composites made of bamboo apus fiber – epoxy resin and charcoal – tapioca starch with several compositions have been synthesized. Bamboo fiber powder as the rest of cutting process was refined and filtered by mesh 40 before used. Epoxy resin 1021A and hardener 1021B has been used as resin. The synthesis of epoxy resin-based composites was carried out via simple mixing method by adding adequate 70% ethanol solution before drying. The 100 mesh-filtered dry charcoal was mixed with tapioca mixture before it was pressed and dried to produce briquette composites. To study the compressive elastic modulus of the composites, pressure tests using Mark 10 Pressure Test Machine have been carried out. It was found that all the composites show maximum compressive elastic modulus at certain component compositions. The maximum elastic modulus for bamboo fiber-epoxy resin, charcoal – epoxy resin and charcoal-tapioca starch were observed at 52.9%, 56.3%, and 25.0% of mass fraction of bamboo fiber, charcoal and tapioca ...

Molecular dynamics simulation of microorganism motion in fluid based on granular model in the case of multiple simple push-pull filaments

Microorganism model for simulating its motion is proposed in this work. It consists of granular particles which can interact to each other through linear and bending spring mimicking microorganism muscles. As some parts of the organism are moving, they will also push the surrounding fluid through Stokes’ force. Gravity influence is simply neglected. All these forces are used to get motion parameters of organism through molecular dynamics method with improved Euler algorithm. It is observed that the use of simplify to push-pull organ gives more effective motion than shrink- and swell-organs as reported in previous works. Comparison of use of single and multiple push-pull filaments are discussed here, where the single one requires phase difference between alternation of length of filament and drag coefficient of some sub-parts. It is observed that synchronization between locomotive organs is required in order to produce circular motion, while a value could produce no motion at all.

Preliminary study of Alzheimer's Disease diagnosis based on brain electrical signals using wireless EEG

This research aims to study brains electrical signals recorded using EEG as a basis for the diagnosis of patients with Alzheimers Disease (AD). The subjects consisted of patients with AD, and normal subjects are used as the control. Brain signals are recorded for 3 minutes in a relaxed condition and with eyes closed. The data is processed using power spectral analysis, brain mapping and chaos test to observe the level of complexity of EEGs data. The results show a shift in the power spectral in the low frequency band (delta and theta) in AD patients. The increase of delta and theta occurs in lobus frontal area and lobus parietal respectively. However, there is a decrease of alpha activity in AD patients where in the case of normal subjects with relaxed condition, brain alpha wave dominates the posterior area. This is confirmed by the results of brain mapping. While the results of chaos analysis show that the average value of MMLE is lower in AD patients than in normal subjects. The level of chaos associated with neural complexity in AD patients with lower neural complexity is due to neuronal damage caused by the beta amyloid plaques and tau protein in neurons.

Spectral and brain mapping analysis of EEG based on Pwelch in schizophrenic patients

The aim of this study is to investigate and analyze the differences of power spectral distribution in various frequency bands between healthy subjects and schizophrenic patients. Subjects in this study were 8 people consisting of 4 schizophrenic patients and 4 healthy subjects. Subjects were recorded from 12 electrodes with Electroencephalography (EEG). EEG signals were recorded during a resting eye-closed state for 4-6 minutes. Data were extracted and analyzed by centering and filtering, then performed using Welch Periodogram technique for the spectral estimation with a Hamming window. The results of this study showed that delta power spectral in schizophrenic patients increased ten times from healthy subjects; theta power spectral in schizophrenic patients increased three times from healthy subjects; alpha power spectral in schizophrenic patients decreased with an increase of one third of healthy subjects. These results were confirmed by Kolmogorov-Smirnov test showing there were significant differences between schizophrenic and healthy subjects on delta, theta and alpha brain wave. Based on the results of Brain Mapping analysis showed that there was significant increasing in the activity of delta waves and theta waves in frontal lobe of schizophrenics, whereas the alpha waves indicated a decrease in the occipital lobe in all schizophrenic patients.