arXiv subjects

Fisca Dian Utami

Publications and source records attributed to Fisca Dian Utami.

5 recordsLinked to original sources

arXiv2019

Second Order Phase Transition and Universality of Self-Buckled Elastic Slender Columns

Self-buckling is an interesting phenomenon that is easily found around us, either in nature or in objects made by human. Palm fronds which initially directed upward when they were short and turned into bending after appreciably longer is an example of the self-buckling phenomenon. We report here that the self-buckling of columns can be treated as a process of second order phase transition by considering the straight column as disorder state, the bending column as order state, and the temperature as the inverse of column length. The critical temperature corresponds to the inverse of critical length for buckling, 1/Lcr, and the deviation angle made by column free end relative to vertical direction satisfies a scaling relationship with a scaling power of 0.485. Changing of the column geometry from the vertically upward to the bending state can be considered as a transition from disorder state to order state.

physics.class-ph↗

arXiv2019

Landscape Geometry-based Percolation of Traffic in Several Populous Cities around the World

We described the average traffic congestion in several populous cities around the world from a new concept, namely landscape percolation. The ratio of the residential area size to road width is a fundamental parameter that controls the traffic congestion. We have compared the model with data extracted from several populous cities around the world (directly from Google Earth images) and demonstrated very consistent results. The criterion for a city landscape that makes a city is considered as congested or less congested has been identified. The model also explains remarkably well the consistency of the measured data with various reports on congestion levels (such as the recognized Tomtom congestion level or Numbeo traffic index) of some populous cities around the world. These findings may help in designing new cities or redesigning the infrastructure of congested cities, for example for deciding what is the maximum size of the residential area and how width the roads are. This work also shows the similarity of the problem in conducting composite (electric current flow), brine transport between icebergs (fluid flow), and traffic (vehicle flow)

physics.soc-ph↗

arXiv2018

How a Snake Can Raise its Neck High although its Body is Very Soft. Similarity with a Thin Plastic Tube Filled with Air

The bodies of snakes, such as king cobras, are very soft so that it is nearly impossible for them to raise their heads higher than around one meter. By direct measurement, we were only possible to hold the body of a freshly killed cobra vertically at around 0.05 m. Here, for the first time it is reported that the king cobra can control the effective elastic modulus of its body so that it can raise its head up to several tens of centimeters. The effective elastic modulus is enhanced by increasing the pressure of air trapped inside the respiration channel, which is similar to increasing the stiffness of a thin plastic tube by filling it with air at pressure above atmospheric pressure. The neck height increases with the effective elastic modulus according to a scaling relationship. It was also simply proved that the peak of force or constriction pressure is proportional to the snakes diameter. This work may provide a physical foundation underlying the mechanical properties of slender animals.

physics.bio-ph↗

arXiv2018

Brazil Nut Effect in Roads that Allow Cars and Motorbikes to Pass Through

In some countries, cars and motorbikes are allowed to pass through the same road. We observe a phenomenon similar to a Brazil nut effect (BNE) that frequently occurs on such roads, in which motorbikes (representations of small particles) segregate in front of cars (representations of large particles), although the motorbikes are initially located far behind the cars. Deep investigations of the BNE-like phenomena in such roads are reported here, where a combination of aerial views using a quad-copter camera and simulations is studied. We show for the first time that most phenomena observed in common BNEs are also observed in such roads.

physics.soc-ph↗

arXiv2018

Very high efficiency of low cost graphite-based solar cell by improving the fill factor using optimal ion concentration in polymer electrolyte

We report the development of graphite-based solar cells using a simple method and low cost materials. Suspension of graphite powder in mineral water was simply dropped onto the surface of fluorine-doped tin oxide glass (FTO) to form a thick film. Surprisingly, using mineral waters greatly improved the efficiency of the solar cell to reach the highest efficiency of 6.97%. Due to some minerals contained, the mineral water induced the development of fibrous structure between the graphite particles which is assumed to play a role as a bridge for the photoexcited electrons to quickly move to the electrode and suppress recombination with holes. This efficiency is very attractive when considering the materials used to develop the solar cell are all low cost. Economically this may challenge the present high efficiency semiconductor-based solar cells. We achieved the high efficiency by manipulating the cell fill factor through optimizing the ion concentration in PVA.LiOH polymer electrolyte. We also propose an equation to describe the effect of LiOH concentration and efficiency and we also provide strong correlation between the cell efficiency and the polymer conductivity

physics.app-ph↗