arXiv subjects

Byung Mook Weon

Publications and source records attributed to Byung Mook Weon.

18 recordsLinked to original sources

arXiv2022

Effects of adaptive acceleration response of birds on collective behaviors

Collective dynamics of many interacting particles have been widely studied because of a wealth of their behavioral patterns quite different from the individual traits. A selective way of birds that reacts to their neighbors is one of the main factors characterizing the collective behaviors. Individual birds can react differently depending on their local environment during the collective decision-making process, and these variable reactions can be a source of complex spatiotemporal flocking dynamics. Here, we extend the deterministic Cucker-Smale model by including the individual's reaction to neighbors' acceleration where the reaction time depends on the local state of polarity. Simulation results show that the adaptive reaction of individuals induces the collective response of the flock. Birds are not frozen in a complete synchronization but remain sensitive to perturbations coming from environments. We confirm that the adaptivity of the reaction also generates natural fluctuations of orientation and speed, both of which are indeed scale-free as experimentally reported. This work may provide essential insight in designing resilient systems of many active agents working in complex, unpredictable environments.

nlin.AO↗

arXiv2020

A logistic model for flowing particles

Counting how many particles pass through a specific space within a specific time is an interesting question in applied physics and social science. Here a logistic model is developed to estimate the total number of flowing particles. This model sheds light on a collective contribution of particle growth rate and transient probability within a specific space in particle counting. This model may offer a basic concept to understand transport dynamics of flowing particles.

physics.soc-ph↗

arXiv2019

Randomness is valid at large numbers

Randomness is a central concept to statistics and physics. Here, a statistical analysis shows experimental evidence that tossing coins and finding last digits of prime numbers are identical regarding statistics for equally likely outcomes. This analysis explains why randomness in equally likely outcomes can be valid only at large numbers.

stat.AP↗

arXiv2019

Extreme cavity expansion in soft solids: damage without fracture

Cavitation is a common damage mechanism in soft solids. Here, we study this using a phase-separation technique in stretched, elastic solids to controllably nucleate and grow small cavities by several orders of magnitude. The ability to make stable cavities of different sizes, as well as the huge range of accessible strains, allows us to systematically study the early stages of cavity expansion. Cavities grow in a scale-free manner, accompanied by irreversible bond breakage that is distributed around the growing cavity, rather than being localized to a crack tip. Furthermore, cavities appear to grow at constant driving pressure. This has strong analogies with the plasticity that occurs surrounding a growing void in ductile metals. In particular we find that, although elastomers are normally considered as brittle materials, small-scale cavity expansion is more like a ductile process. Our results have broad implications for understanding and controlling failure in soft solids.

cond-mat.soft↗

arXiv2016

Physical aging in article page views

Statistics of article page views is useful for measuring the impact of individual articles. Analyzing the temporal evolution of article page views, we find that article page views usually decay over time after reaching a peak, especially exhibiting relaxation with nonexponentiality. This finding suggests that relaxation in article page views resembles physical aging as frequently found in complex systems.

physics.soc-ph↗

arXiv2016

Short time dynamics of water coalescence on a flat water pool

Coalescence is an important hydrodynamic event that frequently takes place in nature as well as in industry. Here we provide an experimental study on short time dynamics of water coalescence, particularly when a water droplet comes in contact with a flat water surface, by utilizing high-resolution high-penetration ultrafast X-ray microscopy. Our results demonstrate a possibility that an extreme curvature difference between a drop and a flat surface can significantly modify the hydrodynamics of water coalescence, which is unexpected in the existing theory. We suggest a plausible explanation for why coalescence can be modified by an extreme curvature difference.

physics.flu-dyn↗

arXiv2013

Shedding new light on the mystery of wetting on soft solids

One of the most questionable issues in wetting is the vertical force balance that is excluded in Young's law. On soft deformable solids, such as biotic materials and synthetic polymers, the vertical force of liquid leads to a microscopic protrusion of the contact line, i.e. a "wetting ridge". The wetting principle that determines the geometry of the ridge-tip is at the heart of the issues over the past half century. Here, we reveal a universal wetting principle by directly visualizing ridge-tips with high spatio-temporal resolution using x-ray microscopy. We find that the tip-geometry is asymmetric and bent, and invariant during ridge growth or by surface softness. This singular geometry is explained by linking the macroscopic and microscopic contact angles to Young's and Neumann's laws, respectively. Our dual-scale model would be applicable to a general framework in wetting and give new clues to various issues in cell-substrate interaction and elasto-capillary problems.

cond-mat.soft↗

arXiv2013

Patterning droplets with durotaxis

Numerous cell-types have shown a remarkable ability to detect and move along gradients in stiffness of an underlying substrate -- a process known as durotaxis. The mechanisms underlying durotaxis are still unresolved, but generally believed to involve active sensing and locomotion. Here, we show that simple liquid droplets also undergo durotaxis. By modulating substrate stiffness, we obtain fine control of droplet position on soft, flat substrates. Unlike other control mechanisms, droplet durotaxis works without imposing chemical, thermal, electrical or topographical gradients. This enables a new approach to large-scale droplet patterning and is potentially useful for many applications, such as microfluidics, thermal control and microfabrication.

cond-mat.soft↗

arXiv2010

Mathematical link of evolving aging and complexity

Aging is a fundamental aspect of living systems that undergo a progressive deterioration of physiological function with age and an increase of vulnerability to disease and death. Living systems, known as complex systems, require complexity in interactions among molecules, cells, organs, and individuals or regulatory mechanisms to perform a variety of activities for survival. On this basis, aging can be understood in terms of a progressive loss of complexity with age; this suggests that complexity in living systems would evolve with age. In general, aging dynamics is mathematically depicted by a survival function, which monotonically changes from 1 to 0 with age. It would be then useful to find an adequate survival function to link aging dynamics and complexity evolution. Here we describe a flexible survival function, which is derived from the stretched exponential function by adopting an age-dependent exponent. We note that the exponent is associated with evolving complexity, i.e., a fractal-like scaling in cumulative mortality. The survival function well depicts a general feature in survival curves; healthy populations show a tendency to evolve towards rectangular-like survival curves, as examples in humans or laboratory animals. This tendency suggests that both aging and complexity would evolve towards healthy survival in living systems. Our function to link aging with complexity may contribute to better understanding of biological aging in terms of complexity evolution.

q-bio.PE↗

arXiv2009

Predicting Human Lifespan Limits

Recent discoveries show steady improvements in life expectancy during modern decades. Does this support that humans continue to live longer in future? We recently put forward the maximum survival tendency, as found in survival curves of industrialized countries, which is described by extended Weibull model with age-dependent stretched exponent. The maximum survival tendency suggests that human survival dynamics may possess its intrinsic limit, beyond which survival is inevitably forbidden. Based on such tendency, we develop the model and explore the patterns in the maximum lifespan limits from industrialized countries during recent three decades. This analysis strategy is simple and useful to interpret the complicated human survival dynamics.

q-bio.PE↗

arXiv2004

Introduction to new demographic model for humans

The Gompertz model since 1825 has significantly contributed to interpretation of ageing in biological and social sciences. However, in modern research findings, it is clear that the Gompertz model is not successful to describe the whole demographic trajectories. In this letter, a new demographic model is introduced especially to describe human demographic trajectories, for example, for Sweden (2002). The new model is derived from the Weibull model with an age-dependent shape parameter, which seems to indicate the dynamical aspects of biological systems for longevity. We will discuss the origin of the age-dependent shape parameter. Finally, the new model presented here has significant potential to change our understanding of definition of maximum longevity.

q-bio.PE↗

arXiv2004

Ultimate limit to human longevity

Are there limits to human longevity? We suggest a new demographic model to describe human demographic trajectories. Specifically, the model mathematically defines the limits of longevity. Through the demographic analysis of trends for Sweden (between 1751 and 2002), Switzerland (between 1876 and 2002) and Japan (between 1950 and 1999), which are the longest-lived countries, we would like to demonstrate whether or not there is the ultimate limit to longevity. We analyse the trends of new demographic indicators, the characteristic life and the shape parameter, and calculate the mathematical limits of longevity. We find out the surprising phenomenon that the mathematical limits of longevity decrease as the longevity tendency increases in recent decades. These paradoxical trends will be explained by the complementarity of longevity, which is attributable to the nature of biological systems for longevity. According to the regression analysis, the ultimate limit for humans is estimated to be approximately 124 years, which may be considered to be the biological limit for humans.

q-bio.PE↗

arXiv2004

Demographic trajectories for supercentenarians

A fundamental question in aging research concerns the demographic trajectories at the highest ages, especially for supercentenarians (persons aged 110 or more). We wish to demonstrate that the Weon model enables scientists to describe the demographic trajectories for supercentenarians. We evaluate the average survival data from the modern eight countries and the valid and complete data for supercentenarians from the International Database on Longevity (Robine and Vaupel, (2002) North American Actuarial Journal 6, 54-63). The results suggest that the Weon model predicts the maximum longevity to exist around ages 120-130, which indicates that there is an intrinsic limit to human longevity, and that the Weon model allows the best possible description of the demographic trajectories for supercentenarians.

q-bio.PE↗

arXiv2004

Complementarity principle on human longevity

In recent we introduced, developed and established a new concept, model, methodology and principle for studying human longevity in terms of demographic basis. We call the new model the "Weon model", which is a general model modified from the Weibull model with an age-dependent shape parameter to describe human survival and mortality curves. We demonstrate the application of the Weon model to the mortality dynamics and the mathematical limit of longevity (the mortality rate to be mathematically zero, implying a maximum longevity) in the Section I. The mathematical limit of longevity can be induced by the mortality dynamics in nature. As a result, we put forward the complementarity principle, which explains the recent paradoxical trends that the mathematical limit decreases as the longevity increases, in the Section II. Our findings suggest that the human longevity can be limited by the complementarity principle.

q-bio.PE↗

arXiv2004

Complementarity between survival and mortality

Accurate demographic functions help scientists define and understand longevity. We summarize a new demographic model, the Weon model, and show the application to the demographic data for Switzerland (1876-2002). Particularly, the Weon model simply defines the maximum longevity, which is induced in nature by the mortality dynamics. In this study, we reconsider the definition of the maximum longevity and the effectiveness for longevity by the combined effect of the survival and mortality functions. The results suggest that the mortality function should be zero at the maximum longevity, since the density function is zero but the survival function is not zero. Furthermore, the effectiveness for longevity can be maximized at the characteristic life by the complementarity between the survival and mortality functions, which suggests that there may be two parts of rectangularization for longevity. The historical trends for Switzerland (1876-2002) implies that there may be a fundamental limiting force to restrict the increase of the effectiveness. As a result, it seems that the density function is essential to define and understand the mortality dynamics, the maximum longevity, the effectiveness for longevity, the paradigm of rectangularization and the historical trends of the effectiveness by the complementarity between the survival and mortality functions.

q-bio.PE↗

arXiv2004

Analysis of trends in human longevity by new model

Trends in human longevity are puzzling, especially when considering the limits of human longevity. Partially, the conflicting assertions are based upon demographic evidence and the interpretation of survival and mortality curves using the Gompertz model and the Weibull model; these models are sometimes considered to be incomplete in describing the entire curves. In this paper a new model is proposed to take the place of the traditional models. We directly analysed the rectangularity (the parts of the curves being shaped like a rectangle) of survival curves for 17 countries and for 1876-2001 in Switzerland (it being one of the longest-lived countries) with a new model. This model is derived from the Weibull survival function and is simply described by two parameters, in which the shape parameter indicates 'rectangularity' and characteristic life indicates the duration for survival to be 'exp(-1)'. The shape parameter is essentially a function of age and it distinguishes humans from technical devices. We find that although characteristic life has increased up to the present time, the slope of the shape parameter for middle age has been saturated in recent decades and that the rectangularity above characteristic life has been suppressed, suggesting there are ultimate limits to human longevity. The new model and subsequent findings will contribute greatly to the interpretation and comprehension of our knowledge on the human ageing processes.

q-bio.PE↗

arXiv2004

Mortality decrease and mathematical limit of longevity

We wish to verify that the mortality deceleration (or decrease) is a consequence of the bending of the shape parameter at old ages. This investigation is based upon the Weon model (the Weibull model with an age-dependent shape parameter) for human survival and mortality curves. According to the Weon model, we are well able to describe the mortality decrease after the mortality plateau, including the mortality deceleration. Furthermore, we are able to simply define the mathematical limit of longevity by the mortality decrease. From the demographic analysis of the historical trends in Switzerland (1876-2001) and Sweden (1861-2001), and the most recent trends in the other eleven developed countries (1996-2001), we confirm that the bending of the shape parameter after characteristic life is correlated with the mortality deceleration (or decrease). As a consequence, this bending of the shape parameters and the mortality deceleration is associated with the mathematical limit on longevity. These results suggest that the mathematical limit of longevity can be induced by the mortality deceleration (or decrease) in nature. These findings will give us a breakthrough for studying the mortality dynamics at the highest ages.

q-bio.PE↗

arXiv2004

General functions for human survival and mortality

General functions for human survival and mortality may support a possibility of general mechanisms in human ageing. We discovered that the survival and mortality curves could be described very simply and accurately by the Weibull survival function with age-dependent shape parameter. The age-dependence of shape parameter determines the shape of the survival and mortality curves and tells the nature of the ageing rate. Especially, the progression of shape parameter with age may be explained by the increase of interaction among vital processes or the evolution of susceptibility to faults with age. Age-related diseases may be attributed to the evolution of susceptibility to faults with age.

q-bio.PE↗