arXiv subjects

Mikrajuddin Abdullah

Publications and source records attributed to Mikrajuddin Abdullah.

At least 19 recordsLinked to original sources

arXiv2023

Theoretical foundation for the Pareto distribution of international trade strength and introduction of an equation for international trade forecasting

I propose a new terminology, international trade strength, which is defined as the ratio of a country's total international trade to its GDP. This parameter represents a country's ability to generate international trade by utilizing its GDP. This figure is equivalent to GDP per capita, which represents a country's ability to use its population to generate GDP. Trade strength varies by country. The intriguing question is, what distribution function does the trade strength fulfill? In this paper, a theoretical foundation for predicting the distribution of trade strength and the rate of change of trade strength were developed. These two quantities were found to satisfy the Pareto distribution function. The equations were confirmed using data from the World Integrated Trade Solution (WITS) and the World Bank by comparing the Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC) to five types of distribution functions (exponential, lognormal, gamma, Pareto, and Weibull). I also discovered that the fitting Pareto power parameter is fairly close to the theoretical parameter. In addition, a formula for forecasting a country's total international trade in the following years was also developed.

econ.GN↗

arXiv2023

A New Approach to Overcoming Zero Trade in Gravity Models to Avoid Indefinite Values in Linear Logarithmic Equations and Parameter Verification Using Machine Learning

The presence of a high number of zero flow trades continues to provide a challenge in identifying gravity parameters to explain international trade using the gravity model. Linear regression with a logarithmic linear equation encounters an indefinite value on the logarithmic trade. Although several approaches to solving this problem have been proposed, the majority of them are no longer based on linear regression, making the process of finding solutions more complex. In this work, we suggest a two-step technique for determining the gravity parameters: first, perform linear regression locally to establish a dummy value to substitute trade flow zero, and then estimating the gravity parameters. Iterative techniques are used to determine the optimum parameters. Machine learning is used to test the estimated parameters by analyzing their position in the cluster. We calculated international trade figures for 2004, 2009, 2014, and 2019. We just examine the classic gravity equation and discover that the powers of GDP and distance are in the same cluster and are both worth roughly one. The strategy presented here can be used to solve other problems involving log-linear regression.

econ.GN↗

arXiv2023

Magnetic Lens Made of a Single Solenoid for Controlling Bending of Two-Dimensional Ion Beam

The magnetic field inside an ideal solenoid cavity with an arbitrary cross-section is always constant, while it is always zero outside the solenoid. We can make a solenoid lens that can focus a parallel beam to a point behind it by adjusting the curvature of the solenoid circumference. In this paper, we discuss the design of magnetic lenses ranging from simple geometries to the general ones. We discovered that there are an infinite number of curvatures that can be used to focus the parallel beam to a specific focal point. Using this property, we also present the concept of a simple mass spectrometer by measuring the intensity of the ion captured by a detector placed at the focal point. This result is expected to enrich learning material in undergraduate courses, especially for the topic of electricity and magnetism.

physics.acc-ph↗

arXiv2023

Coulomb-like Model for International Trade Flow and Derivation of Distribution Function for Trade Flow Strength

To describe international trade flows, we propose the coulomb force formulation, in which the magnitude of the charge represents gross domestic product (GDP) and the distance between countries is the bilateral distance, the product of spatial distance and "dielectric constant," rather than the spatial distance as used in the gravitation model, allowing it to be time dependent. The "dielectric constant" is influenced by factors such as warfare, transportation disruptions, trade agreements, social, geography, politics, culture, and others. The GDP and distance power parameters were estimated using data from high-GDP countries' export-import transactions. We also developed a trade strength distribution equation that fits World Bank data reasonably well over a decade.

q-fin.GN↗

arXiv2022

Introducing Cashless Transaction Index based on the Effective Medium Approximation

The effective medium approximation (EMA) method is commonly used to estimate the effective conductivity development in composites containing two types of materials: conductors and insulators. The effective conductivity is a global parameter that measures how easily the composite conducts electric current. Currently, financial transactions in society take place in cash or cashless, and, in the cashless transactions the money flows faster than in the cash transactions. Therefore, to provide a cashless grading of countries, we introduce a cashless transaction index (CTI) which is calculated using the EMA method in which individuals who make cash transactions are analogous to the insulator element in the composite and individuals who make cash transactions are analogous to the conductor element. We define the CTI as the logarithmic of the effective conductivity of a country's transactions. We also introduce the time dependent equation for the cashless share. Estimates from the proposed model can explain well the data in the last few years.

econ.GN↗

arXiv2021

Physics of Bamboo Rifle

We conducted simple experiments and derived physics equations to explain the working principle of a bamboo rifle. This toy is often played by children in many places that have bamboo plants, such as in ASEAN countries. We identified two main physical processes: mechanics and thermodynamics of gas which controls the firing mechanism of such a rifle.

physics.ed-ph↗

arXiv2021

Slope of Dry Granular Materials Surface is Generally Curved

As if it has become a consensus that the slope of the granular heap is straight, and from that, an angle of repose is defined. However, closer inspection shows that the slopes are not truly straight, instead, more often they have convex shapes, although with small convexity. Similar curvature is observed on the sand dunes' surfaces. We derive equations together with experiments on 10 types of granular materials to show that, in general, the slope of the granular heap is convex while the straight slope is a critical state that rarely occurs. The angle of repose is allowed to vary within a narrow range around a critical value. If the angle of repose is slightly greater (smaller) than the critical value, the slope is convex (concave). The model also answers why the surfaces of granular heaps, including sand dunes, are more often convex rather than concave or straight, and advocate the simultaneous estimation of the coefficient of friction on the grain and the type of packing in the heap. The results might open new understandings related to granular material properties as well as sand transport and geological records in several deserts.

cond-mat.soft↗

arXiv2020

Bending of Spaghetti Beams and Columns Exposed to Hot Steam Reveals Several Physical Properties of the Spaghetti

In this paper, we show that bending of spaghetti beams and columns exposed to hot steam reveals the time evolution of young modulus, the diffusion coefficient of water molecules penetrating the spaghetti, the partial Fickian behavior of water diffusion, and a logistic-like evolution of column bending angle. The bending geometries were timely recorded and the Young moduli were obtained by processing the images. We applied two equations proposed by us previously, one equation was applied for beam bending and the other for column bending, to estimate the Young moduli. The experiment was conducted by exposing the freely-hung cantilever spaghetti beams and columns using hot steam from boiling water so that the images were recorded in realtime while the beam or column bent undisturbedly. Surprisingly, the estimated diffusion coefficient of water molecules matched well the experimental data reported by others. This method may become an alternative for estimating the diffusion coefficient of vapor molecules penetrating the materials.

physics.class-ph↗

arXiv2020

Sarong rolled around a body demonstrates the force for separating two sheets joined by folding and rolling is very large

There are a lot of new sciences that have been inspired by common phenomena and even by old traditions practiced in our daily lives. Eventually, it may induce unexpected new technologies after deeply explored. In this paper, inspired by the wearing of traditional cloth, named sarong, by the community in the South East Asian countries and others, we investigated the behavior of sheets folded like rolling of sarong around the stomach. Simple equipment was designed to qualitatively collect the data and combined with simple modeling. Rolling of the sarong around the stomach generates the joining force of two sheets, increasing proportionally to the square of the number of rolling. This finding is potentially applied for developing a method for strongly joining sheets by simply rolling and releasing the join by simply unrolling. This work can also be simply duplicated elsewhere so that it is worthy of teaching materials at undergraduate levels. Both scientific and teaching contents can be extracted simultaneously.

physics.class-ph↗

arXiv2020

Why the same key can open different padlocks?

We accidentally observed that one key can open two padlocks from different brands. Based on this observation, here we derived equations to estimate the number of different padlocks that can be produced. We focus on simple padlocks that are usually used in most households. It is made of a rectangular block of metal and crafted at any position. Different keys have different sizes and positions of the crafting (hole) and un-crafting (hill) portions. We limit the study to only padlocks having a maximum of four holes. This is the typical architecture of household padlocks. We observed that the number of different padlocks depends on the minimum size of the holes and hills. We also observe a scaling relationship between the number of different padlocks that can be produced with the size of holes or hills.

physics.pop-ph↗

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↗

arXiv2019

Minimal Tools for Accurately Measuring the Coefficient of Kinetic Friction

Measuring the coefficient of kinetic friction is much more difficult than that of the static counterpart. Here we report a simple method using minimal tool to accurately measuring the coefficient of kinetic friction. We employed an inclined plane, the tool for measuring time, and a protractor. This method is much simpler and cheaper than other methods reported by some authors previously. The results are consistent with the date reported elsewhere.

physics.ed-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

Experiment and Modeling of Rice Winnowing: Granular Segregation Method in Ancient Traditions

Rice winnowing is a process of separation of small and large rice grains by air flow practiced since the ancient human history especially in societies where rice is the main source of carbohydrate (in Asia, Africa, and Latin America). Indeed, this process contains rich of scientific rule but has never been documented by the old society. We report here experimental investigation of the rice winnowing and develop a physical model to explain the process of segregation of rice grains having different size or density. Flapping the tray in the winnowing process, generates a vortex centered at position around the tray free end. We demonstrated numerically that the effectiveness of segregation is strongly depended on the different in grain sizes (for grain from the same material), the initial position of the grain, and the angular velocity of the vortex generated by flapping the tray. We obtained a phase diagram describing different final conditions of winnowing process (either the small grains move towards the tray fee end or move toward the inner end of the tray, able or unable to leave the tray at the free end). The result can be useful to design a new method in separating grains based on size or density.

cond-mat.soft↗

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↗

arXiv2018

Stability of Granular Tunnel

We demonstrated the stability of tunnels made of granular matters is strongly dependent on the grain size, tunnel diameter, and water content in the granules. Larger tunnel radius, larger grain size, and too much water content tend to destabilize the tunnel. We also develop a model to describe such findings. We identified a phase diagram of stability which greatly controlled by granular bond order. For granular bond order of larger than unity, we can always made a stable tunnel. However, for granular bond order of less than unity, we obtain a general expression for maximum tunnel thickness that can be made. To best of our knowledge, this is the first exploration regarding the granular tunnel stability.

cond-mat.soft↗