• Title/Summary/Keyword: Protect Device

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Hysteresis Current Control with Self-Locked Frequency Limiter for VSI Control (자기동조 주파수 제한기를 갖는 전압원 인버터의 히스테리시스 전류제어)

  • Choe, Yeon-Ho;Im, Seong-Un;Gwon, U-Hyeon
    • The Transactions of the Korean Institute of Electrical Engineers B
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    • v.51 no.1
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    • pp.23-33
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    • 2002
  • A hysteresis control is widely used to control output current of inverter. A hysteresis bandwidth is affected by system parameters such as source voltage, device on/off time, load inductance and resistance. The frequency limiter is used to protect switching devices overload. In the conventional hysteresis controller, a lock-out circuit with D-latch and timer is used to device protection circuit. But switching delay time and harmonic components are appeared in output current. In this paper the performance of lock-out circuit is tested, and new circuit for switching device fault protection is proposed ad it's performance is simulated.

A Study on the Development of a Transient Voltage Blocking Device for Info-communication Facilities (정보통신기기용 과도전압 차단장치의 개발에 관한 연구)

  • 한주순
    • Journal of Advanced Marine Engineering and Technology
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    • v.23 no.2
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    • pp.159-167
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    • 1999
  • This paper presents a new transient voltage blocking device(TOBD)which low power and high frequency bandwidth to protect info-communication facilities from transient voltages. Conventional protection devices have some problems such as low frequency bandwidth low ener-gy capacity and high remnant voltage. in order to improve these limitations a hybrid type TOBD which consists of a gas tube avalanche diodes and junction type field effect transistor (JFETs) is developed. The TOBD differs from the conventional protection devices in configuration and JFETs are used as an active non-linear element and a high speed switching diode with low capacitance limited high current. Therefore the avalanche diode with low energy capacity are protected from the high current and the TOBD has a very small input capacitance. From the performance test using combination surge generator which can produce $1.2/50{\mu}m$ 4.2 kV/max, $8/20{\mu}m$ 2.1 kAmax it is confirmed that the proposed TOBD has an excellent protection per-formance in tight clamping voltage and limiting current characteristics.

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Study on Separation Distance to Protect Radio Service from Inductive System (유도성 시스템으로부터 무선기기 보호를 위한 이격 거리에 관한 연구)

  • Lee, Il-Kyoo;Shim, Yong-Sup;Min, Kyoung-Il;Cha, Jae-Sang;Lee, Kyong-Gun
    • Journal of Satellite, Information and Communications
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    • v.6 no.1
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    • pp.103-108
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    • 2011
  • This paper is related radio interference from inductive system to radio device in home and industrial environment according to increasing the usage of inductive system. In order to analyze interference from magnetic field strength of inductive system, interference model was suggested and explain the method to calculate separation distance by using conversion that from magnetic field strength to magnetic dipole moment based on suggested interference model. Also, scenario that interference occur between inductive system and radio device was shown and the separation distance between inductive system and radio device was calculate with that scenario. The suggested method in this paper will be used to secure the compatibility between inductive system and radio device.

Development of Protective Device for Quadcopter on Impact (외부충격 흡수를 위한 쿼드콥터의 보호 장치 개발)

  • Na, Yeong-Min;Park, Jong-Kyu;Lee, Hyun-Seok;Kang, Tae-Hun;Park, Tae-Gone
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.14 no.1
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    • pp.63-69
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    • 2015
  • Recently, research and interests in pilotless and radio-controlled quadcopters have increased due to military, hobby, and air-photo applications. However, quadcopters are fragile and can very easily to break when they crash. Therefore, it is necessary to create a protective device such that these devices can protect the main board, motor, and propellers from outside impacts. In this paper, a protective device for a quadcopter is designed in the form of a circle to disperse shock. Also, a dropping and impact simulation was performed to verify that the quadcopter can be efficiently protected when using the proposed device, created with the commercial finite element software Solidworks.

ITO-Ag NW based Transparent Quantum Dot Light Emitting Diode (ITO-Ag NW기반 투명 양자점 발광 다이오드)

  • Kang, Taewook;Kim, Hyojun;Jeong, Yongseok;Kim, Jongsu
    • Korean Journal of Materials Research
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    • v.30 no.8
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    • pp.421-425
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    • 2020
  • A transparent quantum dot (QD)-based light-emitting diode (LED) with silver nanowire (Ag NW) and indium-tin oxide (ITO) hybrid electrode is demonstrated. The device consists of an Ag NW-ITO hybrid cathode (-), zinc oxide, poly (9-vinylcarbazole) (PVK), CdSe/CdZnS QD, tungsten trioxide, and ITO anode (+). The device shows pure green-color emission peaking at 548 nm, with a narrow spectral half width of 43 nm. Devices with hybrid cathodes show better performances, including higher luminance with higher current density, and lower threshold voltage of 5 V, compared with the reference device with a pure Ag NW cathode. It is worth noting that our transparent device with hybrid cathode exhibits a lifetime 9,300 seconds longer than that of a device with Ag NW cathode. This is the reason that the ITO overlayer can protect against oxidization of Ag NW, and the Ag NW underlayer can reduce the junction resistance and spread the current efficiently. The hybrid cathode for our transparent QD LED can applicable to other quantum structure-based optical devices.

Parameter identification for the bubble point measurement of Liquid Acquisition Device (액체포집장치의 기포점 측정을 위한 변수식별)

  • Jeon, Sang-Eon;Park, Soo-Hyung;Byun, Yung-Hwan;Jung, Young-Suk;Oh, Seung-Hyub
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2012.05a
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    • pp.416-423
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    • 2012
  • Liquid acquisition device in the liquid propellant supply system is required to protect entrance of gas bubble into the propulsion system. The device exploits the capillary effect of micro-sized poles in a screen and supplies pure liquid-phase propellant to the propulsion system. The bubble point is the most important performance parameter in the design of a liquid acquisition device. In this paper, performance parameters affecting the bubble point are identified through literature survey, in order to develop the experimental setup for the bubble point measurement.

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A Interval Distance Calculation and Forward Collision Warning Algorithm for Vehicle Safety Communications on a Highway (고속도로에서 차량 안전 통신을 위한 거리 계산과 전방충돌사고경보 알고리즘)

  • Oh, Sang Yeob
    • Journal of Digital Convergence
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    • v.10 no.10
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    • pp.295-300
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    • 2012
  • Various forward collision warning algorithms have studied in order to protect a car accident. For this, in general, algorithms using an external device such as a camera and sensor generate a forward collision warning. However, if using the external device, it can occur errors due to device characteristics when there is rain or fog. Also, the prevention of a chain-reaction collision is insufficient because the system generates a warning in case of only vehicle having a forward collision danger. If it combines the vehicle safety communications, the method becomes a solution to protect a chain-reaction collision. So, In this paper, we proposes a improved forward collision warning algorithm using the wireless communication technique, driver's information, breaking distance, and velocity. And we compare and analyze our algorithm and previous algorithms.

An Effective Technique for Protecting Application Data using Security Enhanced (SE) Android in Rooted Android Phones (루팅된 안드로이드 폰에서 SEAndroid를 이용한 효과적인 앱 데이터 보호 기법)

  • Jeong, Youn-sik;Cho, Seong-je
    • Journal of KIISE
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    • v.44 no.4
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    • pp.352-362
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    • 2017
  • This paper analyzes security threats in Security Enhanced (SE) Android and proposes a new technique to efficiently protect application data including private information on rooted Android phones. On an unrooted device, application data can be accessed by the application itself according to the access control models. However, on a rooted device, a root-privileged shell can disable part or all of the access control model enforcement procedures. Therefore, a root-privileged shell can directly access sensitive data of other applications, and a malicious application can leak the data of other applications outside the device. To address this problem, the proposed technique allows only some specific processes to access to the data of other applications including private information by modifying the existing SEAndroid Linux Security Module (LSM) Hook function. Also, a new domain type of process is added to the target system to enforce stronger security rules. In addition, the proposed technique separates the directory type of a newly installed application and the directory type of previously installed applications. Experimental results show that the proposed technique can effectively protect the data of each application and incur performance overhead up to or less than 2 seconds.

A Design Method on Power Sensefet to Protect High Voltage Power Device (고전압 전력소자를 보호하기 위한 센스펫 설계방법)

  • Kyoung, Sin-Su;Seo, Jun-Ho;Kim, Yo-Han;Lee, Jong-Seok;Kang, Ey-Goo;Sung, Man-Young
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2008.06a
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    • pp.6-7
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    • 2008
  • Current sensing in power semiconductors involves sensing of over-current in order to protect the device from harsh conditions. This technique is one of the most important functions in stabilizing power semiconductor device modules. The sense FET is very efficient method with low power consumption, fast sensing speed and accuracy. In this paper we have analyzed the characteristics of proposed sense FET and optimized its electrical characteristics to apply conventional 450V power MOSFET devices by numerical and simulation analysis. The proposed sense FET has the n-drift doping concentration $1.5\times10^{14}cm^{-3}$, size of $600{\mu}m^2$ with 4.5 $\Omega$, and off-state leakage current below 50 ${\mu}A$. We offer the layout of the proposed sense FET to process actually. The offerd design and optimization methods is meaningful, which the methods can be applied to the power devices having various breakdown voltages for protection.

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Study on the Hybrid Passivation layer of OLEDs using the Organic/Inorganic Thin Film (유/무기 복합 박막을 이용한 유기발광 소자의 보호층에 관한 연구)

  • Bae, Sung-Jin;Lee, Joo-Won;Lee, Young-Hoon;Kang, Nam-Soo;Kim, Dong-Young;Hwang, Sung-Woo;Kim, Jai-Kyung;Ju, Byeong-Kwon
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2006.04a
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    • pp.78-80
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    • 2006
  • The hybrid thin-film (HTF) passivation layer composed of the Ultra Violet (UV) curable acrylate layer and MS-31 (MgO:$SiO_2$=3:1wt%) layer was adopted in organic light emitting device (OLEO) to protect organic light emitting materials from penetrations of oxygen and water vapors. The results showed that the HTF layer possessed a very low WVTR value of lower than $0.007gm/m^{2+}day$ at $37.8^{\circ}C$ and 100% RH. This value was within the limited range of the sensitivity of WVTR measurements. And the lifetime of the HTF passivated device became almost three times longer than that of the bare device. The HTF on the OLEO was found to be very effective in protect what from the penetrations of oxygen and moisture.

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