• Title/Summary/Keyword: 위험 진동수

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Stiffness effect of the lamination pressing force for laminated rotor (적층된 로터에서 적층판 압착력의 강성 효과)

  • 김영춘;박철현;박희주;문태선
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2002.05a
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    • pp.565-568
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    • 2002
  • A lot of rotating machines are being used in the industrial world and electric motor and generator take the most part of it. When it comes to the electric motor and generator, we can not help thinking about the eddy current because it brings a loss of electric and can be a important reason of the heat generation. To attenuate eddy current. laminated silicon steel sheets are being used in general. Especially, laminated rotor is being used for rotating part of the electric motor and generator and it decreases electrical loss and heat generation but we can be faced with another problem. In general, most of the motor and generator can be normally operated under 3600rpm because they are designed to have the first critical speed more than that speed. But nowadays, they should be operated more than the first critical speed as usual with the trend of high speed. large scale and high precision in industrial world. The critical speed can be determined from the inertia and stiffness for the rotor and bearing of rotating systems. The laminated rotor stiffness can be hardly determined because it can be derived a lot factors for instance rotor material and shape. lamination material and shape. insulation material. lamination force and so on. In this paper, the change of the natural frequency of the motor was examined with the change of the lamination force as an experimental method.

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User Authentication Method using Vibration Cue on Smartphone (진동 큐를 이용한 스마트폰 사용자 인증 방식)

  • Lee, Jong-Hyeok;Choi, Ok-Kyung;Kim, Kang-Seok;Yeh, Hong-Jin
    • The KIPS Transactions:PartC
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    • v.19C no.3
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    • pp.167-172
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    • 2012
  • Mobile phone devices and memory card can be robbed and lost due to the carelessness that might be caused to leak personal information, and also company's confidential information can be disclosed. Therefore, the importance of user authentication to protect personal information is increasing exponentially. However, there are the limitations that criminals could easily obtain and abuse information about individuals, because the input method of personal identification number or the input method of password might not be safe for Shoulder Surfing Attack(SSA). Although various biometric identification methods were suggested to obstruct the SSA, it is the fact that they also have some faults due to the inconvenience to use in mobile environments. In this study, more complemented service for the user authentication was proposed by applying Keystroke method in the mobile environments to make up for the faults of existing biometric identification method. Lastly, the effectiveness and validity of this study were confirmed through experimental evaluations.

Study on real time monitoring to detect third party damage using vibration signal (진동신호를 이용한 타공사 조기 감시 기술 연구( I ))

  • Cho S.H.;Jeon K.S.;Park K.W.;Cho Y.B.;Li S.Y.;Kyo Y.T.
    • Journal of the Korean Institute of Gas
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    • v.4 no.1 s.9
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    • pp.1-8
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    • 2000
  • Third party damage is one of the causes intrimiting the safety of a buried pipelines and it is very important to detect third party damage on pipelines as soon as possible. The purpose of this study is whether third-party damage can be detected by accelerometer sensor and how far the third-party damage signal can propagate. And a pilot experiment was carried out in order to find third-party damage location. As a result, the detected signal's spectum is high frequency at short distances, as the distance is far, the signals in high frequency range are attenuated and those in low frequency range remain. It was also proved that third-party damage within 5.3km distance can be detected by monitoring vibration signals.

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Effects of Structural Parameter Variations on Dynamic Responses (해석(解析)모델의 구조변수(構造變數) 변동(變動)이 동적응답에 미치는 영향(影響))

  • Park, Hyung Ghee;Lim, Boo Young
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.13 no.3
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    • pp.59-67
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    • 1993
  • The variations of the natural frequencies and the peak response acceleration at the top of prestressed concrete reactor building due to random variability and/or model uncertainty of structural parameters are studied. The results may be used as essential input parameters in seismic probabilistic risk assessment or seismic margin assessment of the reactor building. The sensitivity test of each structural parameter is first performed to determine the most influential parameter upon the natural frequency of structure model. Then Monte Carlo simulation technique is applied to evaluate the effect of parameter variation on the natural frequencies and the peak response acceleration. The acceleration time history is obtained by direct integration scheme. As the study results, it is found that the fundamental natural frequency and the peak response acceleration at the top of the building are most strongly affected by Young's modulus among the structural parameters, in which the value of mean plus one standard deviation obtained by probabilistic approach deviates up to about (+)12% from the result of deterministic method. Considering the uncertainty of flexural rigidity, the structural responses vary in range of (-)4%~(+)14%.

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외상 후 스트레스 장애의 평가

  • Kim Jeong-Beom
    • 대한불안의학회:학술대회논문집
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    • 2004.06a
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    • pp.185-213
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    • 2004
  • 우리는 살아가면서 흔히 개인적으로 극심한 스트레스를 겪거나 불행히도 어떤 뜻밖의 재난이나 큰 사고를 경험할 수 있다. 이런 외상적 사건들을 겪고 대부분의 사람들은 잘 극복할 수 있으나 일부 사람들은 심각한 의상 후 스트레스 반응을 보여 그런 외상이 지나감에도 불구하고 괴로운 기억 속에서 그것을 회상시키는 활동과 상황을 피하며 늘 불안한 마음으로 몸은 현재에 살고 있지만 마음은 실상 과거에 매달려 있고 과거의 고통 속에서 헤어 나오지 못하고 있다. 외상 후 스트레스 장애는 다른 불안 장애, 우울증처럼 흔한 질환으로 사회생활에 큰 지장을 주며 삶의 질을 손상시킨다. 그렇지만 외상을 당한 당사자들이 이런 이야기를 하기 꺼려하고, 이런 사람들을 진료실에서 종종 만날 수 있는 임상가들도 외상의 심각성과 외상 후 스트레스 장애에 대한 인식이 부족하여, 우리 주위에 많은 사람이 외상 후 스트레스 장애로 고생하고 있지만 외상 후 스트레스 장애로 진단되는 경우가 실제보다 훨씬 적다. 따라서 외상 후 스트레스 장애에 대한 평가를 배움으로써 더 많은 환자들을 정확히 진단하며 다른 질환과의 감별을 쉽게 할 수 있고, 환자들의 고통과 어려움이 과연 무엇인지 잘 알 수 있으며, 치료 표적과 치료 전략을 정하고, 치료 계획을 세우는 데 도움을 얻을 수 있다. 평가 방법으로는 구조화된 면담, 평가 척도, 정신 생리적 측정법, 치료자의 임상적인 결정 등이 있다. 향후에는 외상 후 스트레스 장애의 증상 정도뿐만 아니라 일상생활, 사회적 관계, 직업적, 사회적 적응 및 기능에 미치는 영향도 같이 평가하는 도구들이 개발되고, 현재 개발된 많은 평가 척도들이 새로이 수정되고 표준화되어, 이런 평가 척도들을 통해 외상 후 스트레스 장애의 경과와 외상 후 스트레스 장애로 인한 정신 사회적 영향을 더 잘 알 수 있는 자료들이 많이 수집되길 바란다. 대칭이, 작은대칭이, 펄조개는 저질이 니질인 곳에서 주로 서식하고 있었고 귀이빨대칭이는 사니질과 사질에 주로 서식하고 있었다. 특히 삽교호 수계 채집된 귀이빨대칭이는 사니질과 사질의 저질에서 출현하였다.및 내장낭 조직들이 중요한 에너지 저장소이며, 영양 공급 기관임을 알 수 있었으며, 폐각근 조직과 내장낭 조직들의 영양물질 함량 변화는 생식소의 에너지 요구에 따라 변하고 있음을 알 수 있었다.. 따른 신장 기능에 대한 영향을 평가해 보아야 한다.하를 조사한 결과, 연간 진동해역으로 유입되는 오염부하량은 부유물질 기준으로 전체 37,316 ton/yr로 추정되었고, 이중 육지기원 부하량이 9,809 ton/yr (26.3%) 였고, 해역의 침강량 23,576 ton/yr (63.2%), 양식생물의 배설량이 3,932 ton/yr (10.5%) 로 대부분이 해역의 침강량에 의한 것으로 조사되었다. 육지오염부하량이 변동이 없다는 전제 조건 아래, 진동만의 피조개 채묘장을 미더덕 양식장으로 품종전환시킬 경우, 전체 부하량은 산술적으로 약 196%가 증가한 72,998 ton/yr 가 되고, 양식생물의 배설량은 10배 정도 증가하게 되어 진동만의 오염부하를 가중하게 된다. 진동만은 여름철 빈산소수괴 및 적조가 빈번하게 발생하고 있으므로 미더덕 양식장을 새로이 시설할 경우 오염부하가 가중될 것으로 판단되어, 앞으로 진동만의 양식장 수용능력을 파악하여 적정량의 양식물량이 시설되어야 할 것이다.25 psu에서 가장 높게 나타났다.인 단백뇨는 진행성 경과의 위험성을 동시에 암시해 주는 매우 유용한 지표이다. 본 연구 결과 학교 신체 검사상에서 발견된 단독 단백뇨의 주된 원인은 기립성 단백뇨로 81.8%를 차지하였다. 그러나 지속성 단백뇨의 경우 비록 9.1%의 빈도를 보였지만, 신장 조직검사를 시행한 결과 진행성 경과를 취할 수 있는

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A Study on the Dynamic Characteristics of Axial Vibration Damper for Two Stroke Low Speed Diesel Engine (저속 2행정 디젤엔진의 종진동 댐퍼 동특성에 관한 연구)

  • 이돈출;김정렬;김의간
    • Journal of Advanced Marine Engineering and Technology
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    • v.18 no.2
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    • pp.113-121
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    • 1994
  • Since two oil shocks in 1970s, all of engine makers have persevered in their efforts to reduce specific fuel consumption and to increase engine power rate as much as possible in marine diesel engines. As a result, the maximum pressure in cylinders of these engines has been continuously increased. It causes direct axial vibration. The axial stiffness of crank shaft is low compared to old types of engine models by increasing the stroke/bore ratio and its major critical speed might occur within engine operation range. An axial damper, therefore, needs to be installed in order to reduce the axial vibration amplitude of the crankshaft. Usually the main critical speed of axial vibration for the propulsion shafting system with a 4-8 cylinder engine exists near the maximum continuous revolution(MCR). In this case, when the damping coefficient of the damper is increased within the allowance of the structural strength, its stiffness coefficient is also increased. Therefore, the main critical speed of axial vibration can be moved beyond the MCR. It has the same function as a conventional detuner. However, in the case of a 9-12 cylinder engine, the main critical speed of axial vibration for the propulsion shafting system exists below the MCR and thus the critical speed cannot be moved beyond the MCR by using an axial damper. In this case, the damping coefficient of an axial damper should be adjusted by considering the range of engine revolution, the location and vibration amplitude of the critical speed, the fore and aft vibration of the hull super structure. It needs to clarify the dynamic characteristics of the axial vibration damper to control the axial vibration appropriately. Therefore authors suggest the calculation method to analyse the dynamic characteristics of axial vibration damper. To confirm the calculation method proposed in this paper, it is applied to the propulsion shafting system of the actual ships and satisfactory results are obtained.

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Application of Electronic Deck Charge Blasting Method to a Vertical Shaft Excavation (수직구 굴착시 전자뇌관을 이용한 Deck-Charge 발파 시공사례)

  • Kim, Jae-Hong;Kim, Hee-Do;Lee, Jun-Won;Kim, Gab-Soo;Son, Young-Bok;Kim, Jae-Hoon
    • Explosives and Blasting
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    • v.31 no.1
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    • pp.64-75
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    • 2013
  • This case study deals with an excavation blasting carried out at "Sooseo-Pyeongtek ${\bigcirc}$-${\bigcirc}$ section construction site" in the vicinity of residential area. Originally, the sequential blasting (multi-stage blasting) using electric detonators was planed in this area. However, there was a concern that the sequential blasting method could increase the construction cost by delaying the construction period due to possible complaints from local residents. As an alternative, electronic deck blasting technique was taken in order to meet the ground vibration regulation (0.2cm/s, in apartment area) and to keep the construction schedule. The performance of the electronic deck charge blasting was two times better than the sequential blasting with electric detonators and the level of ground vibration was also within the regulatory value (0.2cm/s). In particular, it was shown that the use of electronic detonater eDevII, which was developed for tunnel, could provide more convenient and electrically safer working condition.

A Study on the Anomaly Prediction System of Drone Using Big Data (빅데이터를 활용한 드론의 이상 예측시스템 연구)

  • Lee, Yang-Kyoo;Hong, Jun-Ki;Hong, Sung-Chan
    • Journal of Internet Computing and Services
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    • v.21 no.2
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    • pp.27-37
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    • 2020
  • Recently, big data is rapidly emerging as a core technology in the 4th industrial revolution. Further, the utilization and the demand of drones are continuously increasing with the development of the 4th industrial revolution. However, as the drones usage increases, the risk of drones falling increases. Drones always have a risk of being able to fall easily even with small problems due to its simple structure. In this paper, in order to predict the risk of drone fall and to prevent the fall, ESC (Electronic Speed Control) is attached integrally with the drone's driving motor and the acceleration sensor is stored to collect the vibration data in real time. By processing and monitoring the data in real time and analyzing the data through big data obtained in such a situation using a Fast Fourier Transform (FFT) algorithm, we proposed a prediction system that minimizes the risk of drone fall by analyzing big data collected from drones.

미세현미경 성대수술시 Weerdar개폐식 후두경을 통한 고빈도 제트환기

  • 김현정;이국현;이상철;김광현
    • Proceedings of the KOR-BRONCHOESO Conference
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    • 1995.04a
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    • pp.92.1-92
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    • 1995
  • Weerdar 개폐식 후두경은 Kleinsasser 후두경과 Killian-Lynch 현가 후두경의 장점을 혼합하여 개발한 것으로서 광학장치, 흡인관, injection cannula 등을 후두경에 부착할 수 있다. 그리고 후두경 내강에 injection cannula를 장치하여 고빈도 제트환기법, 고빈도 진동법, 고빈도 양압환기법을 시행할 수 있다. 이 경우 기관내 삽관을 배제하여 cannula선단이 성대 위에 위치하기 때문에 성대의 후교련까지 시야를 확보할 수 있고, 후두경 양측에 넓은 틈이 있기에 수술조작이 용이하며, 레이저 사용시에 화재의 위험을 최소로 할 수 있다. 이에 성대수술시 cannula를 통한 제트환기 중 시간 경과에 따른 활력징후, 동맥혈산소화, 이산화탄소의 배출상태 변화를 관찰하였다. 그 결과 수슬시간 30분까지 동맥혈 산소분압의 감소나 이산화탄소 축적은 관찰되지 않았기에 30분 이내의 성대수술시 기관내 삽관없이도 시행할 수 있는 안전한 마취관리의 한 방법이라 생각한다.

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The Critical Speed Analysis of the Differential Planetary Gear Train of a Concrete Mixer Truck Mixer Reducer (콘크리트 믹서 트럭용 믹서 감속기의 차동 유성 기어 트레인에 대한 위험속도 해석)

  • Bae, Myung Ho;Bae, Tae Yeol;Kim, Dang Ju
    • Journal of Drive and Control
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    • v.14 no.1
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    • pp.1-7
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    • 2017
  • The power train of a concrete truck mixer reducer includes differential planetary gears to get a large reduction ratio for operating the mixer drum in a compact structure. These differential planetary gears are a very important part of the mixer reducer where strength problems are the main concern. Gear bending stress, gear compressive stress and scoring failure are the main concerns. Many failures in differential planetary gears are due to the insufficient gear strength and resonance problems caused by major excitation forces such as gear mating failure in the transmission. In the present study, where the excitation frequencies are the gear tooth passing frequencies of the mating gears, a Campbell diagram is used to calculate differential planetary gear critical speeds. Mode shapes and natural frequencies of the differential planetary gears are calculated by CATIA V5. These are used to predict gear resonance failures by comparing the working speed range with the critical speeds due to the gear transmission errors of the differential planetary gears.