113 research outputs found
Stochastic Turing pattern formation in a model with active and passive transport
We investigate Turing pattern formation in a stochastic and spatially
discretized version of a reaction diffusion advection (RDA) equation, which was
previously introduced to model synaptogenesis in \textit{C. elegans}. The model
describes the interactions between a passively diffusing molecular species and
an advecting species that switches between anterograde and retrograde
motor-driven transport (bidirectional transport). Within the context of
synaptogenesis, the diffusing molecules can be identified with the protein
kinase CaMKII and the advecting molecules as glutamate receptors. The
stochastic dynamics evolves according to an RDA master equation, in which
advection and diffusion are both modeled as hopping reactions along a
one-dimensional array of chemical compartments. Carrying out a linear noise
approximation of the RDA master equation leads to an effective Langevin
equation, whose power spectrum provides a means of extending the definition of
a Turing instability to stochastic systems, namely, in terms of the existence
of a peak in the power spectrum at a non-zero spatial frequency. We thus show
how noise can significantly extend the range over which spontaneous patterns
occur, which is consistent with previous studies of RD systems.Comment: 26 pages, 8 figure
Fast Parameterless Ballistic Launch Point Estimation based on k-NN Search
This paper discusses the problem of estimating a ballistic trajectory and the launch point by using a trajectory similarity search in a database. The major difficulty of this problem is that estimation accuracy is guaranteed only when an identical trajectory exists in the trajectory database (TD). Hence, the TD must comprise an impractically great number of trajectories from various launch points. Authors proposed a simplified trajectory database with a single launch point and a trajectory similarity search algorithm that decomposes trajectory similarity into velocity and position components. These similarities are applied k-NN estimation. Furthermore, they used the iDistance technique to partition the data space of the high-dimensional database for an efficient k-NN search. Authors proved the effectiveness of the proposed algorithm by experiment.Defence Science Journal, Vol. 64, No. 1, January 2014, DOI:10.14429/dsj.64.295
Optimality of intercellular signaling: direct transport versus diffusion
Intercellular signaling has an important role in organism development, but
not all communication occurs using the same mechanism. Here, we analyze the
energy efficiency of intercellular signaling by two canonical mechanisms:
diffusion of signaling molecules and direct transport mediated by signaling
cellular protrusions. We show that efficient contact formation for direct
transport can be established by an optimal rate of projecting protrusions,
which depends on the availability of information about the location of the
target cell. The optimal projection rate also depends on how signaling
molecules are transported along the protrusion, in particular the ratio of the
energy cost for contact formation and molecule synthesis. Also, we compare the
efficiency of the two signaling mechanisms, under various model parameters. We
find that the direct transport is favored over the diffusion when transporting
a large amount of signaling molecules. There is a critical number of signaling
molecules at which the efficiency of the two mechanisms are the same. The
critical number is small when the distance between cells is far, which helps
explain why protrusion-based mechanisms are observed in long-range cellular
communications
System-reliability-based Disaster Resilience Evaluation of Cable-stayed Bridge under Fire Hazard Using Reliability-Redundancy Analysis
The 20th working conference of the IFIP Working Group 7.5 on Reliability and Optimization of Structural Systems (IFIP 2022) will be held at Kyoto University, Kyoto, Japan, September 19-20, 2022.The concept of disaster resilience recently emerged in efforts to gain holistic understanding of civil infrastructure systems exposed to various natural or human-made hazards. To effectively evaluate the resilience of complex infrastructure systems generally consisting of many interdependent structural components, Lim et al. (2022) proposed a system-reliability-based framework for disaster resilience. In the proposed framework, the disaster resilience of a civil infrastructure system is characterized by three criteria: reliability, redundancy, and recoverability. For comprehensive resilience analyses at the scale of individual structures, the reliability (β) and redundancy (π) indices were newly defined in the context of component- and system-level reliability analysis, respectively. Reliability-redundancy diagram, i.e., the scatter plot of the reliability and redundancy indices computed for each initial disruption scenario, was also proposed to help a decision-maker check whether the corresponding risk is acceptable for the society. In this paper, we demonstrate the framework through its application to a cable-stayed bridge in South Korea, the Seohae Grand Bridge under fire hazards. First, a probabilistic model is developed to describe the hazard of fire scenarios that may occur on the deck of the cable-stayed bridge. Next, finite element simulations are performed to compute the reliability and redundancy indices through component and system reliability analyses for the fire accident scenarios. An adaptive simulation method, AK-MCS (Echard et al. 2011), is employed to overcome the computational cost issue. The example successfully demonstrates that the reliability-redundancy analysis and diagram facilitate a comprehensive assessment of the disaster resilience of a complex civil infrastructure such as a cable-stayed bridge by using sophisticated computational simulations and advanced reliability methods
Integrating Metal-Oxide-Decorated CNT Networks with a CMOS Readout in a Gas Sensor
We have implemented a tin-oxide-decorated carbon nanotube (CNT) network gas sensor system on a single die. We have also demonstrated the deposition of metallic tin on the CNT network, its subsequent oxidation in air, and the improvement of the lifetime of the sensors. The fabricated array of CNT sensors contains 128 sensor cells for added redundancy and increased accuracy. The read-out integrated circuit (ROIC) was combined with coarse and fine time-to-digital converters to extend its resolution in a power-efficient way. The ROIC is fabricated using a 0.35 μm CMOS process, and the whole sensor system consumes 30 mA at 5 V. The sensor system was successfully tested in the detection of ammonia gas at elevated temperatures
Biosensor system-on-a-chip including CMOS-based signal processing circuits and 64 carbon nanotube-based sensors for the detection of a neurotransmitter
We developed a carbon nanotube (CNT)-based biosensor system-on-a-chip (SoC) for the detection of
a neurotransmitter. Here, 64 CNT-based sensors were integrated with silicon-based signal processing
circuits in a single chip, which was made possible by combining several technological breakthroughs
such as efficient signal processing, uniform CNT networks, and biocompatible functionalization of CNTbased
sensors. The chip was utilized to detect glutamate, a neurotransmitter, where ammonia,
a byproduct of the enzymatic reaction of glutamate and glutamate oxidase on CNT-based sensors,
modulated the conductance signals to the CNT-based sensors. This is a major technological
advancement in the integration of CNT-based sensors with microelectronics, and this chip can be
readily integrated with larger scale lab-on-a-chip (LoC) systems for various applications such as LoC
systems for neural networks.We developed a carbon nanotube (CNT)-based biosensor system-on-a-chip (SoC) for the detection of
a neurotransmitter. Here, 64 CNT-based sensors were integrated with silicon-based signal processing
circuits in a single chip, which was made possible by combining several technological breakthroughs
such as efficient signal processing, uniform CNT networks, and biocompatible functionalization of CNTbased
sensors. The chip was utilized to detect glutamate, a neurotransmitter, where ammonia,
a byproduct of the enzymatic reaction of glutamate and glutamate oxidase on CNT-based sensors,
modulated the conductance signals to the CNT-based sensors. This is a major technological
advancement in the integration of CNT-based sensors with microelectronics, and this chip can be
readily integrated with larger scale lab-on-a-chip (LoC) systems for various applications such as LoC
systems for neural networks
Consolidation of Rural-Oriented Administrative Districts and It's Economic Effects
The purpose of the present study is to investigate the potential economic effects of consolidation of rural administrative districts even though municipal consolidation has been focused on urban areas in Korea. We utilize two methodologies to identify rural districts that can be consolidated. First, we identify rural districts suitable for the consolidation through cluster analyses. Second, we examine the economic effects of the consolidation based on a minimum cost approach. Following the methodologies, we identify four rural regions that are suitable for municipal consolidation. They are Yoenchoen- Dongduchoen, Gosung-Injae, Changnyeong-Uiryeng and Yangsan- Gijang. With respect to per capita expenditure savings projection, Gijang-Yangsan is expected to save the expenditure by 86% through the consolidation and 33% for Gosung-Injae, 23% for Yoenchoen-Dongduchoen and 21% was estimated for Changnyeong-Uiryeng. The results may cast important light on the necessity of consolidation in all four rural regions. While the present study entails limitations in data and empirical applications, it provides a theoretical basis and empirical implications for municipal consolidation in rural regions. The present study concludes with some policy implications and directions for future studies
Analysis on the Consumers’ Preferences for the Equestrian Service
This paper identifies horse riders' preference and measures marginal willingness to pay (MWTP) for equestrian attributes by using choice experiments. It was analyzed that regular riders' satisfaction increased with the following factors: a bigger equestrian facility, better accessibility, indoor and outdoor riding services, and lower riding fees. Additionally, warmbloods were the most preferred type of horses. The results of measuring consumers' MWTP for riding attributes show that they are willing to pay an extra KRW 100,000 a month to use a large-scale equestrian facility rather than a small one and an extra KRW 150,000 a month for an equestrian facility with better accessibility. In addition, horse riders were willing to pay an extra KRW 270,000 to ride a warmblood compared to a Halla horse. The marginal willingness to pay for outdoor riding was KRW 310,000 and that for indoor riding was KRW 390,000. The differences in the respondents' preference for riding attributes were identified through a latent class model, and they were classified into six groups with similar preferences. Each group differed in income levels, gender, and membership types
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