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Influence of Crack on Dynamic Behavior of Simply Supported Beam with Moving Mass (이동질량을 가진 단순지지 보의 동특성에 미치는 크랙의 영향)

  • 윤한익;이용운;손인수
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.13 no.9
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    • pp.720-729
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    • 2003
  • An iterative modal analysis approach is developed to determine the effect of transverse open cracks on the dynamic behavior of simply supported Euler-Bernoulli beam with the moving mass. The influences of the depth and the position of the crack in the beam have been studied on the dynamic behavior of the simply supported beam system by numerical method. The crack section is represented by a local flexibility matrix connecting two undamaged beam segments i.e. the crack is modelled as a rotational spring. This flexibility matrix defines the relationship between the displacements and forces across the crack section and is derived by applying fundamental fracture mechanics theory. As the depth of the crack is increased the frequency of the simply supported beam with the moving mass is increased.

Experiment with Axiom Propeller in Cavitation Tunnel

  • Seo, Kwang-Cheol
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.20 no.3
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    • pp.296-303
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    • 2014
  • The Axiom propeller is a unique 3 bladed propeller and it enables to generate the same amount of thrust going ahead as it does going astern because of its 's' type skew-symmetric blade section. A earlier variant of the design (Axiom I propeller) performed a low propeller efficiency, maximum 35 % efficiency, and further blade outline design was carried out to achieve a higher efficiency. The optimized new blade outline (Axiom II propeller) has more conventional Kaplan geometry shape than Axiom I propeller. Model tests of open water performance and propeller cavitation for both propellers were conducted at Emerson Cavitation Tunnel in order to compare their performances. Experiment results revealed that Axiom II propeller provides a maximum 53 % efficiency and provides better efficiency and cavitation performance over the Axiom I propeller under similar conditions.

KTX Interior Noise Reduction Performance Comparison Using Multichannel Active Noise Control for Each Section (다중채널 능동소음제어기법을 이용한 KTX 실내소음의 구간별 저감성능 비교)

  • Jang, Hyeon-Seok;Kim, Young-Ming;Lee, Tae-Oh;Lee, Kwon-Soon
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.61 no.1
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    • pp.179-185
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    • 2012
  • Since the eco-era is getting closer, the importance of noise reducing in the passenger cars of high-speed train is very important. The active noise control is best choice to reduce low frequency noise because the passive one is too heavy for high speed trains where weight is so critical. Also ANC is able to reduce the ambient noise when the environmental-factor changes. To reduce a three-dimensional closed-space sound field like a car of a high-speed rail is hard to do using single channel ANC control system. We used multi-channel FXLMS algorithm which calculation speed is fast and the secondary path estimation is possible in order to take into account the physical delay in electro acoustic hardware control loudspeaker and power amplifier. Firstly, we have measured interior noise of KTX and estimated noise path in KTX test-bed. However there was some problem related to algorithm divergence and increasing the filter order. We have made a simulation of interior environment of KTX car by using three frequency bands of 120Hz, 280Hz, 360Hz as the most important for KTX ANC system. During this research the interior noise reduction of KTX car was made by using the multi-channel FXLMS algorithm. Reduction performance was evaluated and compared each other for open space section and tunnel section. in-situ experiment for the KTX noise reduction by proposed ANC was performed based on data obtained in simulation and they were compared for open space section and tunnel section as well.

Critical Loads of Eccentrically Loaded Struts with Thin-Walled Open Sections (편심하중을 받는 박벽개단면 압축재의 임계하중)

  • 나영진;이수곤
    • Computational Structural Engineering
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    • v.9 no.4
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    • pp.135-140
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    • 1996
  • Single angle or channel with thin-walled open section can be used as compression member for example as web member in truss. In this case the inevitable eccentricity due to fabrication is commonly neglected in structural design. However eccentricity effect should be considered in the member design, especially in case of compression member. The critical loads of compression members that buckle by twisting or by a combination of bending and twisting are to be determined by solving governing differential equations. In this paper, the investigations are limited to the rolled channels([), equal-leg angles(L), lipped channels(C) and the applied loads are assumed to have some eccentricities.

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Comprehensive Knowledge Archive Network harvester improvement for efficient open-data collection and management

  • Kim, Dasol;Gil, Myeong-Seon;Nguyen, Minh Chau;Won, Heesun;Moon, Yang-Sae
    • ETRI Journal
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    • v.43 no.5
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    • pp.835-855
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    • 2021
  • With the recent increase in data disclosure, the Comprehensive Knowledge Archive Network (CKAN), which is an open-source data distribution platform, is drawing much attention. CKAN is used together with additional extensions, such as Datastore and Datapusher for data management and Harvest and DCAT for data collection. This study derives the problems of CKAN itself and Harvest Extension. First, CKAN causes two problems of data inconsistency and storage space waste for data deletion. Second, Harvest Extension causes three additional problems, namely source deletion that deletes only sources without deleting data themselves, job stop that cannot delete job during data collection, and service interruption that cannot provide service, even if data exist. Based on these observations, we propose herein an improved CKAN that provides a new deletion function solving data inconsistency and storage space waste problems. In addition, we present an improved Harvest Extension solving three problems of the legacy Harvest Extension. We verify the correctness and the usefulness of the improved CKAN and Harvest Extension functions through actual implementation and extensive experiments.

A Structural Approach for the Construction of the Open Instruction Model in Mathematics (열린 수학 수업 모델 구성을 위한 구조적 접근)

  • 백석윤
    • Journal of Educational Research in Mathematics
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    • v.8 no.1
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    • pp.101-123
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    • 1998
  • The purpose of this study is to construct the "open" instructional model that might be used properly in mathematics classroom. In this study, the core philosophy of "openness" in mathematics instruction is looked upon as the transference itself from pursuing simply strengthening the function of instruction such as effectiveness in the management of educational environment into the understanding of the nature of mathematics learning and the pursuing of true effectiveness in mathematics learning. It means, in other words, this study is going to accept the "openness" as functional readiness to open all the possibility among the conditions of educational environment for the purpose of realizing maximum learning effectiveness. With considering these concepts, this study regards open mathematics education as simply one section among the spectrum of mathematics education, thus could be included in the category of mathematics education. The model for open instruction in mathematics classroom, constructed in this study, has the following virtues: This model (1) suggests integrated view of open mathematics instruction that could adjust the individual and sporadic views recently constructed about open mathematics instruction; (2) could suggest structural approach for the construction of open mathematics instruction program; (3) could be used in other way as a method for evaluation open mathematics instruction program.thematics instruction program.

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Screening for the Hormonal Properties of the Chloroform Extract of Carica papaya Linn. Seeds for Antifertility Investigation

  • Mishra, P.K.;Pathak, N.;Manivannan, B.;Lohiya, N.K.
    • Natural Product Sciences
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    • v.6 no.1
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    • pp.5-10
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    • 2000
  • The chloroform extract of the seeds of Carica papaya has been screened for the hormonal properties using ovariectomized female rats for estrogenicity, estrogen primed immature rats for progestogenicity and castrated adult male rats for androgenicity. The results revealed that the extract lacks progestogenicity and androgenicity as evident from the failure of the extract treated animals to mimic progestogen and androgen related changes in the target tissues. The increased weight of vagina and uterus, open status of vagina, cornified and epithelial cells in the vaginal smears and hypertrophy in the uterine epithelium, endometrium and stroma with increased glycogen and sialic acid content in the uterus of the chloroform extract treated animals, which are comparable to those of the ovariectomized estrogen treated animals, suggest that the chloroform extract possesses mild estrogenic activity.

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Dynamic Response Analysis of Composite H-type Cross-section Beams (복합재료 H-형 단면 보의 동적응답 해석)

  • Kim, Sung-Kyun;Song, Oh-Seop
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.20 no.6
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    • pp.583-592
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    • 2010
  • Equations of motion of thin-walled composite H-type cross-section beams exposed to concentrated harmonic and non-harmonic time-dependent external excitations, incorporating a number of nonclassical effects of transverse shear, primary and secondary warping, and anisotropy of constituent materials are derived. The forced vibration response characteristics of a composite H-type cross-section beam exhibiting the circumferentially asymmetric stiffness(CAS) configuration are exploited in connection with the structural bending-torsion coupling resulting from directional properties of fiber reinforced composite materials.

Invitation to Levitotion Contro: Problems Expecting a Smart Solution

  • Kim, Kook-Hun
    • 제어로봇시스템학회:학술대회논문집
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    • 1993.10b
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    • pp.316-320
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    • 1993
  • Electromagnetic suspension (E.M.S) type levitation system is studied in the control system design viewpoint. Dynamic characteristics in theoretical analysis as well as hardware implementation is considered. Open loop unstable, non-linear and timevarying characteristics are reviewed in the theoretcal section, while levitation control system for multi-vehicle train as well as magnet drive system is reviewed in the practical section. This paper suggests not only some well-known problem appearing in levitation control system design but also a subtle problem and solution candidates. But there exist many unmentioned problems wating for a smart problem solver.

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Geometrical Construction of the S Matrix and Multichannel Quantum Defect Theory for the two Open and One Closed Channel System

  • Lee, Chun-Woo
    • Bulletin of the Korean Chemical Society
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    • v.23 no.7
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    • pp.971-984
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    • 2002
  • The multichannel quantum defect theory (MQDT) is reformulated into the form of the configuration mixing (CM) method using the geometrical construction of the S matrix developed for the system involving two open and one closed channels. The reformulation is done by the phase renormalization method of Giusti-Suzor and Fano. The rather unconventional short-range reactance matrix K whose diagonal elements are not zero is obtained though the Lu-Fano plot becomes symmetrical. The reformulation of MQDT yields the partial cross section formulas analogous to Fano's resonance formula, which has not easily been available in other's work.