• 대한산업공학회지
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• 제42권4호
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• pp.290-295
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• 2016

This paper proposes a new method for the automatic detection of atrial fibrillation (AF), using Markov regime switching GARCH (1, 1) model. The proposed method is based on the observation that variability patterns of heart rate intervals during AF significantly differ from regular patterns. The proposed method captures the different patterns of heart rate intervals between two regimes : normal and AF states. We test the proposed method using Massachusetts Institute of Technology-Beth Israel Hospital (MIT-BIH) atrial fibrillation database, and demonstrate the effectiveness of the proposed method.

• 제어로봇시스템학회논문지
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• 제18권6호
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• pp.540-545
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• 2012

In this paper, we propose a fault diagnosis method using artificial neural network and SVM (Support Vector Machine) to detect and isolate faults in the nonlinear systems. The proposed algorithm consists of two main parts: fault detection through threshold testing using a artificial neural network and fault isolation by SVM fault classifier. In the proposed method a fault is detected when the errors between the actual system output and the artificial neural network nominal system output cross a predetermined threshold. Once a fault in the nonlinear system is detected the SVM fault classifier isolates the fault. The computer simulation results demonstrate the effectiveness of the proposed SVM and artificial neural network based fault diagnosis method.

• Nuclear Engineering and Technology
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• 제39권2호
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• pp.95-102
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• 2007

The conceptual design of the MIT modular pebble bed reactor is described. This reactor plant is a 250 Mwth, 120 Mwe indirect cycle plant that is designed to be deployed in the near term using demonstrated helium system components. The primary system is a conventional pebble bed reactor with a dynamic central column with an outlet temperature of 900 C providing helium to an intermediate helium to helium heat exchanger (IHX). The outlet of the IHX is input to a three shaft horizontal Brayton Cycle power conversion system. The design constraint used in sizing the plant is based on a factory modularity principle which allows the plant to be assembled 'Lego' style instead of constructed piece by piece. This principle employs space frames which contain the power conversion system that permits the Lego-like modules to be shipped by truck or train to sites. This paper also describes the research that has been conducted at MIT since 1998 on fuel modeling, silver leakage from coated fuel particles, dynamic simulation, MCNP reactor physics modeling and air ingress analysis.

• Current Optics and Photonics
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• 제5권4호
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• pp.351-361
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• 2021

Speckle imaging is capable of dynamic data acquisition at high spatiotemporal resolution, and has played a vital role in the functional study of biological specimens. The presence of various optical scatterers within the tissue causes alteration of speckle contrast. Thus structures like blood vessels can be delineated and quantified. Although laser speckle imaging is frequently used, an optimization process to ensure the maximum speckle contrast has not been available. In this respect, we here report an experimental procedure to optimize speckle contrast via applying different combinations of varying polarization of the illuminating laser light and multiple analyzer angles. Specifically, samples were illuminated by the p-polarization, 45°-polarization, and s-polarization of the incident laser, and speckle images were recorded without and with the analyzer rotated from 0° to 180° (Δ = 30°). Following the baseline imaging of a solid diffuser and a fixed brain sample, laser speckle contrast imaging (LSCI) was successfully performed to visualize in vivo mouse-brain blood flow. For oblique laser illumination, the maximum contrast achieved with p-polarized and s-polarized light was perpendicular to the analyzer's axis. This study demonstrates the optimization process for maximizing the speckle contrast, which can improve blood-flow estimation in vivo.

• 대한금속재료학회지
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• 제46권9호
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• pp.563-571
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• 2008

The influence of annealing treatment on dynamic deformation behavior of ultra-fine grained aluminum alloys was investigated in this study. After equal-channel angular pressing at $200^{\circ}C$, most of the grains were considerably reduced to nearly equiaxed grains of $0.3{\mu}m$ in size. With an increment of various annealing treatments for 1 hour, resultant microstructures were found to be fairly stable at temperatures up to $200^{\circ}C$, suggesting that static recovery would be dominantly operative, whereas grain growth was pronounced above $250^{\circ}C$. The tensile test results showed that yield and ultimate tensile strengths decreased, but elongation-to-failure and strain hardening rate increased with increasing annealing temperature. The dynamic deformation behavior retrieved with a series of torsional tests was explored with respect to annealed microstructures. Such mechanical response was analyzed in relation to resultant microstructure and fracture mode.

• KCI Concrete Journal
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• 제13권1호
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• pp.53-60
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• 2001

Tests of cylindrical concrete specimens under lateral confining pressure of up to 5,000 psi were conducted for two different axial loading cases: monotonic compression and monotonic tension. The purpose of this experimental investigation is to provide stress-strain characteristics of plain concrete in triaxial stress conditions. Lateral confining pressure levels, loading rates, and strength of concrete specimens are varied as parameters. The loading rates are $34.75$\times$10^{-5}$ in/in/sec for fast, $\times$$6.95x10^{-5}$ in/in/sec for normal. and $0.579$\times$10^{-5}$ in/in/sec for slow loading cases. The concrete specimens used in the experiment have compressive strength of 3,500 psi and 6,500 psi, respectively. Findings of this experiment include dependency of the stress-strain behavior of concrete on the above parameters under two different types of loading conditions. The parametric study includes a series of 106 triaxial tests.

• ETRI Journal
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• 제25권4호
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• pp.238-246
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• 2003

This paper introduces the modeling and analysis of a discrete-time, two-phase queueing system for both exhaustive batch service and gated batch service. Packets arrive at the system according to a Bernoulli process and receive batch service in the first phase and individual services in the second phase. We derive the probability generating function (PGF) of the system size and show that it is decomposed into two PGFs, one of which is the PGF of the system size in the standard discrete-time Geo/G/1 queue without vacations. We also present the PGF of the sojourn time. Based on these PGFs, we present useful performance measures, such as the mean number of packets in the system and the mean sojourn time of a packet.

• 대한화학회지
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• 제16권2호
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• pp.70-73
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• 1972

It has been postulated that acetylcholine exhibits both nicotine and muscarinic activity because of its ability to present two patterns of essential atoms to the receptors. These two patterns arise from the ability of the molecule to exist in more than one preferred conformation. The molecule S(+)-acetyl-${\beta}$-methylacetylcholine exhibits only muscarinic activity. Calculations using molecular orbital theory predict that this molecule prefers only the muscarinic conformation. This is offered as an explanation for the exclusive role of the molecule and as evidence supporting the twoconformation, two-activities hypothesis.

• 한국결정학회:학술대회논문집
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• 한국결정학회 2002년도 정기총회 및 추계학술연구발표회
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• pp.4-4
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• 2002

PDZ domains bind to short segments within target proteins in a sequence-specific fashion. GRIP/ABP family proteins contain six to seven PDZ domains and interact via its sixth PDZ domain (class Ⅱ) with the C-termini of various proteins, including liprin-α. In addition the PDZ456 domain mediates the formation of homo- and heteromultimers of GRIP proteins. To better understand the structural basis of peptide recognition by a class Ⅱ PDZ domain and DZ-mediated multimerization, we determined the crystal structures of the GRIPI PDZ6 domain, alone and in complex with a synthetic C-terminal octapeptide of human liprin-α, at resolutions of 1.5 Å and 1.8 Å, respectively. Remarkably, unlike other class Ⅱ PDZ domains, Ile736 at αB5 rather than conserved Leu732 at αB1 makes a direct hydrophobic contact with the side chain of the Tyr at the -2 position of the ligand. Moreover, the peptide-bound structure of PDZ6 shows a slight reorientation of helix αB, indicating that the second hydrophobic pocket undergoes a conformational adaptation to accommodate the bulkiness of the Tyr's side chain, and forms an antiparallel dimer through an interface located at a site distal to the peptide-binding groove. This configuration may enable formation of GRIP multimers and efficient clustering of GRIP-binding proteins.

• Food Science and Biotechnology
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• 제16권3호
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• pp.415-420
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• 2007

The aim of this study was to determine the various bioactive components of five olive oil varieties, as well as to assess their contribution to the oxidative stability of the oils. Fatty acids, ${\alpha}$-tocopherol, ${\beta}$-carotene, total flavonoids, total phenols, and certain phenolic compounds of extra virgin olive oils (EVOO; blended, arbequina, hojiblanca, and picual) and pure olive oil (POO) were examined. Oxidation stability was evaluated by the peroxide value (POV). The total content of all the studied antioxidant compounds was significantly higher in the EVOOs than the POO (p<0.05). Among the EVOOs, picual had the highest levels of ${\alpha}$-tocopherol ($10.18{\pm}0.40\;mg/100\;g$), ${\beta}$-carotene ($557{\pm}8\;{\mu}g/100\;g$), and total phenols ($110.7{\pm}1.3\;mg/g$), which correlated strongly with antioxidative capacity. Furthermore, the lowest POV occurred in picual EVOO and correlated with the highest monounsaturated fatty acid (MUFA, C16:1 and C18:1) and lowest polyunsaturated fatty acid (PUFA, C18:2 and C18:3) compositions, suggesting the ratio of MUFA to PUFA is a critical parameter for the oxidative stability of olive oil. Our results indicate that the oxidative stability and antioxidant potential of EVOO depends not only on the antioxidant vitamins, but also on the amount of phenolic compounds and fatty acid profile of the oil.