• Geomechanics and Engineering
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• v.8 no.3
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• pp.361-375
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• 2015

Constructions over soft and loose soils are one of the most frequent problems in many parts of the world. Cement and cement-lime mixture have been widely used for decades to improve the strength of these soils with the deep soil mixing method. In this study, to investigate the freeze-thaw effect of sand improved by polymers (i.e., styrene-acrylic-copolymer-SACP, polyvinyl acetate-PVAc and xanthan gum) and fly ash, unconfined compression tests were performed on specimens which were exposed to freeze-thaw cycles and on specimens which were not exposed to freeze-thaw cycles. The laboratory test results concluded that the unconfined compressive strength increased with the increase of polymer ratio and curing time, whereas, the changes on unconfined compressive strength with increase of freeze-thaw cycles were insignificant. The overall evaluation of results has revealed that polymers containing fly ash is a good promise and potential as a candidate for deep soil mixing application.

• 제어로봇시스템학회:학술대회논문집
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• 1999.10a
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• pp.274-277
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• 1999

This paper is concerned with estimating the mass of a loose part in the steam generator of a nuclear power plant. Although there is the basic principle known as “Hertz Theory”for estimating mass and energy of a spherical part impacted on an infinite flat plate, the theory is not directly applicable because real plants do not comply with the underlying ideal assumptions. (Say, the steam generator is of a cylindrical and hemisphere shape.) In this work, a practical method is developed based on the basic theory and considering amplitude and energy attenuation effects. Actually, the impact waves propagating along the plate to the sensor locations become significantly different in shape and frequency spectrum from the original waveform due to the plate and surrounding conditions, distance attenuation and damping loss. To show the validity of the present mass estimation algorithm, it has been applied to the mock-up impact test data and also to real plant data. The results show better performance comparing to the conventional Hertz schemes.

• Nuclear Engineering and Technology
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• v.55 no.10
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• pp.3716-3724
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• 2023

Loose parts monitoring and detecting alarm type in real Nuclear Power Plant have challenges such as background noise, insufficient alarm data, and difficulty of distinction between alarm data that occur during start and stop. Although many signal processing methods and alarm determination algorithms have been developed, it is not easy to determine valid alarm and extract the meaning data from alarm signal including background noise. To address these issues, this paper proposes a denoising autoencoder-based majority vote classification. Training and test data are prepared by acquiring alarm data from real NPP and simulation facility for data augmentation, and noisy data is reproduced by adding Gaussian noise. Using DAEs with 3, 5, 7, and 9 layers, features are extracted for each model and classified into neural networks. Finally, the results obtained from each DAE are classified by majority voting. Also, through comparison with other methods, the accuracy and the false alarm rate are compared, and the excellence of the proposed method is confirmed.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.10a
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• pp.284-289
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• 1997

원자력발전소 금속파편감시계통(LPMS : Loose Parts Monitoring System)은 내각재계통 내부에 존재하는 금속파편물을 조기에 탐지하여 관련 구조물 파손을 방지하므로써 불필요한 검사 및 보수로 인한 작업자 방사선 피폭를 최소화하며 원전 안전성 및 경제성을 제고시킨다. 현재 국내 원전에서 가동중인 금속파편감시설비중 영광 1,2호기와 고리 3,4호기에서 운영중인 Westinghouse사의 금속파편감시설비(상품명: Digital Matal Impact Monitoring System)는 70년대에 개발되어 설치된 설비로 기능의 낙후와 장기간 운영에 따른 노후화로 인해 발생될 수 있는 문제점을 방지하고자 하드웨어 및 금속충격파 검출 및 판별 알고리즘을 개발하여 영광 1,2호기에서 기존 설비와 병렬운전중이다.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.915-916
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• 2006

본 논문은 원자력 발전소의 금속파편감시계통(LPMS)에서 충격신호의 탐지를 위해 사용되는 하드웨어 구현에 관한 것이다. 본 논문에서 구현한 것은 LPMS의 하드웨어 중에서 입력된 신호를 디지털로 변환하여 충격신호의 트리거 판단기능을 하는 DAM(Data acquisition module)보드이다. 본 논문에서 구현한 DAM은 디지털 필터와 트리거 판단을 위한 알고리즘이 DSP에서 실시간으로 처리되어 LPMS의 기능을 업그레이드 하였다.

• CELLMED
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• v.3 no.4
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• pp.28.1-28.7
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• 2013

Careya arborea Roxb. (Lecythidaceae) is a significant medicinal plant known as kumbhi in Ayurveda. Though, most of the plant parts are used in traditional systems of medicine, bark and leaves constitute the important medicinal parts. The present review gives an account of the updated information on its phytochemical and pharmacological properties. The review reveals that numerous phytochemical constituents have been isolated from the plant possessing hepatoprotective, antioxidant, antimicrobial, anticoagulant, analgesic, antidiarrhoeal and various other important activities. Leaves are used in filaria, colic, loose motions and ulcers. Bark is used as an antipyretic, abortifacient, antipruritic and in smallpox, urinary discharges and rheumatic pain. Since last few decades, extensive exploration has been done to establish the biological activities and pharmacology of the extracts and plentiful chemical constituents including flavonoids, tannins, alkaloids, terpenoids and many other have been isolated.

• Journal of Institute of Convergence Technology
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• v.2 no.2
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• pp.20-24
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• 2012

In this paper, we perform a ANSYS simulation of assembly structure composed of three parts, bolt, nut, and coil spring, under the loading of a screw torque 640~800 ($N{\cdot}m$) derived from the given bolt tensile strength 10.9, which allows us to investigate a lock-nut mechanism for the prevention of bolt-loosening after three parts are fastened. And also we investigate the safety factor of each component with effective stress distribution obtained from the simulation, which enables us to estimate the structural safety of a new lock-nut structure. Both simulation and investigation shown in this paper will contribute to the development of a new lock nut structure.

• Journal of Korean Institute of Industrial Engineers
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• v.17 no.2
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• pp.75-86
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• 1991

This paper presents a methodology to enable the tolerances on mating parts of an assembly to be specified and be compatible to the precision of an assembly robot so as to achieve maximum system performance. The measure of performance is defined as the Probability of Successful Assembly (PSA). A typical loose fastener assembly, usually called peg-in-a-hole is investigated. The Geometric Tolerancing System is adopted to represent position tolerances of mating parts. Two models are presented by considering modifiers on a position tolerance, Regardless of Feature Size (RFS) and Maximum Material Condition (MMC). Using these models, it is analyzed how the Standard Limits and Fits recommended by ANSI influence the performance of an assembly robot. For this analysis, the Standard Limits and Fits are transformed to the representation scheme of the Geometric Tolerancing System. Due to low PSAs when the Standard Limits and Fits are taken into account, the effect of chamfers around a hole is also analyzed.

• The Journal of the Acoustical Society of Korea
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• v.15 no.1E
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• pp.5-19
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• 1996

This paper proposes a loose part monitoring system (LPMS) design with a signal processing method based on fuzzy logic. Considering fuzzy characteristics of metallic impact waveform due to not only interferences from various types of noises in an operating nuclear power plant but also complex wave propagation paths within a monitored mechanical structure, the proposed LPMS design incorporates the comprehensive relation among impact signal features in the fuzzy rule bases for the purposes of alarm discrimination and impact diagnosis improvement. The impact signal features for the fuzzy rule bases include the rising time, the falling time, and the peak voltage values of the impact signal envelopes. Fuzzy inference results based on the fuzzy membership values of these impact signal features determine the confidence level data for each signal feature. The total integrated confidence level data is used for alarm discrimination and impact diagnosis purposes. Through the perpormance test of the proposed LPMS with mock-up structures and instrumentation facility, test results show that the system is effective in diagnosis of the loose part impact event(i.e., the evaluation of possible impacted area and degree of impact magnitude) as well as in suppressing false alarm generation.

• ALGAE
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• v.20 no.4
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• pp.279-293
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• 2005

Two new species of Martensia (Delesseriaceae, Rhodophyta) are described from Jeju Island, Korea. Martensia palmata sp. nov. is characterized by the following traits: more or less linearly elongated lobes arising from the distal margin of the flabellate membranous section; intact latticework with coarse and loose mesh; numerous spine-like projections on the leading margin of the latticework; tetrasporangia produced in sori along the entire blade; spermatangia borne in sori on the membranous section and the longitudinal lamellae of the latticework; and cystocarps borne on the margins of the membranous section. Martensia projecta sp. nov. has the following characteristics: subdichotomously furcated blades, with terminal segments slightly attenuated toward the apex; blades with uneven surfaces; basal parts with a multi-layered parenchymatous construction; small and poorlydefined latticework; tetrasporangia and spermatangia produced in sori on the membranous section; and cystocarps borne on the marginal surfaces of the blades. The existence of M. projecta sp. nov. supports the proposal that the genus Opephyllum Schmitz in Schmitz et Hauptfleisch should be assigned to the genus Martensia.