• 한국세라믹학회지
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• 제20권2호
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• pp.153-160
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• 1983

This study was carried out to research the change of mineral phases and the characteristics(apparent specific gra-vity water absorption firing shrinkage modulus of rupture thermal expansion and specific dielectric constant) of the sintered bodies manufactured by kaolin and limestone. Samples were composed of the same theoretical composition as it of anorthite and fired up to 145$0^{\circ}C$ Investigated the change and micro-structure of the mineral phases by XRD and SEM the characterisdtics of the sintered bodies by TMA Automatic Capacitance Bridge and etc. The results were as follow. 1. Reactions of sintering are occurred between 860-95$0^{\circ}C$ and 1200-138$0^{\circ}C$ and state of bloating is occurred at 1410-145$0^{\circ}C$ 2. For the inclusion of feldspar and its fine particles of materials the temperature of producing and collapsing is decreased. 3. Pseudo-wollastonite and gehlenite are formed about 95$0^{\circ}C$ 4. At 114$0^{\circ}C$ anorthite are begin to forming and increase continuously to 138$0^{\circ}C$. Above 141$0^{\circ}C$ content of anorthite are decreased. 5. The variations of bending strength with sintering temperature reflect similar trend of sintered contraction and in-crease continuously from 120$0^{\circ}C$. At 145$0^{\circ}C$ reached about 680kg/cm2. 6. Specific dielectric constant$($\varepsilon$_s)$ of specimen sintered at 141$0^{\circ}C$ is 7.12 and that value is most favorable.

• Smart Structures and Systems
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• 제14권2호
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• pp.105-128
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• 2014

The stochastic damage locating vector (SDLV) method has been studied extensively in recent years because of its potential to determine the location of damage in structures without the need for measuring the input excitation. The SDLV method has been shown to be a particularly useful tool for damage localization in steel truss bridges through numerical simulation and experimental validation. However, several issues still need clarification. For example, two methods have been suggested for determining the observation matrix C identified for the structural system; yet little guidance has been provided regarding the conditions under which the respective formulations should be used. Additionally, the specific layout of the sensors to achieve effective performance with the SDLV method and the associated relationship to the specific type of truss structure have yet to be explored. Moreover, how the location of truss members influences the damage localization results should be studied. In this paper, these three issues are first investigated through numerical simulation and subsequently the main results are validated experimentally. The results of this paper provide guidance on the effective use of the SDLV method.

• 한국정보통신학회논문지
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• 제7권7호
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• pp.1442-1448
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• 2003

네트워크 관리는 메일, 화상회의, 웹, 데이터베이스 등이 작동하는 네트워크 환경에서 더욱 중요한 문제가 되고 있다. 패킷의 적절한 경로를 발견하기 위하여 라우터간에 정보를 교환하는 라우팅 프로토콜이 사용되고 있으나 관리자의 실수로 만들어진 비정상적인 라우팅 테이블로 인하여 데이터를 전송하는 브리지 또는 라우터가 네트워크 디자인의 관점에서 비효율적인 경로로 전송할 수 있다. 이 논문에서는 네트워크상에서 발생할 수 있는 우회 경로를 발견하는 문제를 논의한다. SNMP, MIB로부터의 정보를 사용 계층적 네트워크 구조 분석을 기반으로 우회경로 패스를 발견하는 새로운 알고리즘을 제시하고. 제안된 알고리즘을 검증하기 위해 미리 선언된 데이터를 이용한 시뮬레이션을 수행하였다.

• Journal of Power Electronics
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• 제13권3호
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• pp.419-428
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• 2013

The modular multilevel cascade converter (MMCC) is a new family of multilevel power converters with modular realization and a cascaded pattern for submodules. The MMCC family can be classified by basic configurations and submodule types. One member of this family, the Hexverter, is configured as Double-Delta Full-Bridge (DDFB). It is a novel multilevel AC/AC converter with direct power conversion and comparatively fewer required components. It is appropriate for connecting two three-phase systems with different frequencies and driving an AC motor directly from a utility grid. This paper presents the dq model of a Hexverter with both of its AC systems by state-space representation, which then simplifies the continuous time-varying model into a periodic discrete time-invariant one. Then a generalized multivariable optimal control strategy for regulating the Hexverter's independent currents is developed. The resulting control structure can be adapted to other MMCCs and is flexible enough to include other control criterion while guaranteeing the original controller performance. The modeling method and control design are verified by simulation results.

• 한국구조물진단유지관리공학회 논문집
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• 제10권6호
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• pp.113-123
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• 2006

사장교가 장경간으로 시공됨에 따라 대형화 되고 지진하중, 풍하중 및 차량하중 등 동적 하중에 의해 유발되는 진동현상에 취약한 단점이 나타난다. 이러한 하중 등에 의해 발생된 구조 손상은 구조물의 진동모드 특성에 영향을 미치게 된다. 기존의 정밀안전진단 기술을 이용하여 사장교의 구조 손상을 검색하고 평가하는 것은 상당한 비용과 시간이 소요될 뿐만 아니라 전체적인 구조거동 특성의 변화를 발견하기 어려울 것이다. 따라서 본 연구는 사장교에 대하여 구조손상 전의 진동모드 특성치와 구조손상 후의 진동모드 특성치를 이용하여 구조거동 특성의 변화를 검토하고 구조손상 검색을 수행하였다.

• Journal of Electrical Engineering and Technology
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• 제9권2호
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• pp.523-531
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• 2014

Brushless Dual-Mechanical-Port Electrical Machine (BLDMPEM) is a new type of motor designed for Hybrid Electric Vehicle (HEV), which contains two mechanical ports and two electric ports. Compared with Dual-Mechanical-Port Electrical Machine (DMPEM), the brushless structure brings higher reliability and easier maintenance. In this paper, the model of BLDMPEM is discussed. In Chapter 2, the energy flow and mathematical model of BLDMPEM are analyzed. Then a novel three-phase half-bridge controlled rectifier topology and its control strategy for cruising mode of HEV based on BLDMPEM are proposed in Chapter 3. Compared with the Field Oriented Control (FOC) strategy of BLDMPEM, the proposed method does not require accurate motor parameters, and it is much simpler and easier to be implemented. At last, simulation and experiment results show the feasibility and validity of the proposed strategy.

• 한국군사과학기술학회지
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• 제15권6호
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• pp.754-760
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• 2012

To improve the efficiency and economics of national defence, the needs for defence M&S systems are greatly increased, but the lack of interoperability and reusability lowers the level of reliability in the existing simulations models. Recently, many research activities have been performed and some conceptual models, such as CMMS, DCMF, and KAMA, were introduced. However, these models don't support the whole process of defence M&S system development nor provide integrated domain knowledge and up-to-date data. In this paper, we analyzed the analysts' guidances and doctrines, which are the basic ingredients for the simulation system development, and proposed a systematic structure for all the defence M&S stakeholders to share the standardized domain knowledge, modeling algorithm and data. This will be a logical bridge between Mission Space and Simulation Space, and provide substantial data sets to build simulation systems.

• Journal of Power Electronics
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• 제15권2호
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• pp.356-365
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• 2015

This paper presents a new single phase front-end ac-dc bridgeless power factor correction (PFC) rectifier topology. The proposed converter achieves a high efficiency over a wide range of input and output voltages, a high power factor, low line current harmonics and both step up and step down voltage conversions. This topology is based on a non-inverting buck-boost (Zeta) converter. In this approach, the input diode bridge is removed and a maximum of one diode conducts in a complete switching period. This reduces the conduction losses and the thermal stresses on the switches when compare to existing PFC topologies. Inherent power factor correction is achieved by operating the converter in the discontinuous conduction mode (DCM) which leads to a simplified control circuit. The characteristics of the proposed design, principles of operation, steady state operation analysis, and control structure are described in this paper. An experimental prototype has been built to demonstrate the feasibility of the new converter. Simulation and experimental results are provided to verify the improved power quality at the AC mains and the lower conduction losses of the converter.

• Journal of Power Electronics
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• 제8권2호
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• pp.171-180
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• 2008

One of the major problems in electric power quality is the harmonic contents. There are several methods of indicating the quantity of harmonic contents. The most widely used measure is the total harmonic distortion (THD). Various switching techniques have been used in static converters to reduce the output harmonic content. This paper presents and compares the two harmonic optimization techniques, known as optimal minimization of the total harmonic distortion (OMTHD) technique and optimized harmonic stepped-waveform (OHSW) technique used in multi-level inverters with unequal dc sources. Both techniques are very effective and efficient for improving the quality of the inverter output voltage. First, we describe briefly the cascaded H-bridge multi-level inverter structure. Then, we present the switching algorithm for the inverter based on OHSW and OMTHD techniques. Finally, the results obtained for the two techniques are analyzed and compared. The results verify the effectiveness of the both techniques in multi-level voltage-source inverter with non-equal dc sources, clarifying the advantages of each technique.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2012년도 전력전자학술대회 논문집
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• pp.201-202
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• 2012

This paper presents a simple and cost-effective stand-alone rapid battery charging system of 30kW for electric vehicles. The proposed system mainly consists of active front-end rectifier of neutral point clamped 3-level type and non-isolated bi-directional dc-dc converter of multi-phase interleaved half-bridge topology. The charging system is designed to operate for both lithium-polymer and lithium-ion batteries. The complete charging sequence is made up of three sub-interval operating modes; pre-charging mode, constant-current mode, and constant-voltage mode. Each mode is operated according to battery states: voltage, current and State of Charging (SOC). The proposed system is able to reach the full-charge state within less than 16min for the battery capacity of 8kWh by supplying the charging current of 67A. The optimal discharging algorithm for Vehicle to the Grid (V2G) operation has been adopted to maintain the discharging current of 1C. Owing to the simple and compact power conversion scheme, the proposed solution has superior module-friendly mechanical structure which is absolutely required to realize flexible power expansion capability in a very high-current rapid charging system. Experiment waveforms confirm the proposed functionality of the charging system.