• 대한음성학회지:말소리
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• 제25_26호
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• pp.27-37
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• 1993

This paper deals with the nature and function of intensification in Korean in a wider scope of context which was not paid proper attention. Unobserved new areas of intensification are paid more attention like sound split of polysemy e.g. [s'eda], [kyongk'i] by n of intensification and north Korean application of intensification on [wonsu] and intensification of borrowed English. The recent phenomenon of 'gwua' intensification is experimented on two groups of people, young students and old people beyond 65 years old by means of sociolinguistic analysis. The result shows that its intensification is a form of student violent power and a mark of extreme solidarity among activist students. In conclusion, the nature of so called saisiot[t] e.g. intensification is voiceless tensed pause and its functions are the polarization of the original meaning of the word, sound split of polysemy and attachment of social values by intensification.

• 대한기계학회논문집A
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• 제26권5호
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• pp.924-931
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• 2002

Vacuum interrupters in order to be used in various switch-gear components such as circuit breakers, distribution switches, contactors, etc. spread the arc uniformly over the surface of the contacts. The electrodes of vacuum interrupters are made of sinter-forged Cu-Cr materials for good electrical and mechanical characteristics. Since the closing velocity is 1-2m/s and impact deformation of the electrode depends on the strain rate at that velocity, the dynamic behavior of the sinter-forged Cu-Cr is a key to investigate the impact characteristics of the electrodes. The dynamic response of the material at the high strain rate is obtained from the split Hopkinson pressure bar test using disc-type specimens. Experimental results from both quasi-static and dynamic compressive tests are Interpolated to construct the Johnson-Cook model as the constitutive relation that should be applied to simulation of the dynamic behavior of the electrodes. The impact characteristics of a vacuum interrupter are investigated with computer simulations by changing the value of five parameters such as the initial velocity of a movable electrode, the added mass of a movable electrode, the wipe spring constant, initial offset of a wipe spring and the virtual fixed spring constant.

• 한국전자파학회지:전자파기술
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• 제2권2호
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• pp.19-24
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• 1991

본 논문에서는 태극 모양의 새로운 방향성 결합기를 고안하여 높은 전력 분배율을 실현할 수 있음을 실험을 통하여 입증하였다. 제안돈 태극형 방향성 결합기는 하이브리드 링형 방향성 결합기의 $3\lambda/4$부분을 적극적으로 활용하기 위하여 태극 모양의 구조를 취했으며, 우수 기수 모드 해석법을 이용하여 완전정합과 분리 조건을 만족하는 각 지로의 어드미턴스를 구하였다. 그 결과 마이크로 스트립 라인으로 제작 가능한 저항의 범의 내에서 이미 발표된 연구 결과에서와 같은 크기의 회로 면적내에서도 훨씬 높은 전력 분배율(최대 28DB)을 실현할 수 잇음을 알았으며, CGP-502기판을 이용하영 중심 주파수 10GHz에서 0,8,16dB 전력 분배율을 갖는 태극형 방향성 결합기를 설계 제작하고 실험을 하여 이론의 타당성을 확인하였다.

• International Journal of Automotive Technology
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• 제8권6호
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• pp.799-806
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• 2007

One method for improving the torque capacity of the CVT is to use a split-powered CVT(SPCVT) to reduce the power transmitted into a continuously variable unit(CVU). A variable bridge SPCVT with two planetary gear units(PGUs), which are composed of a sun gear, a ring gear, and carrier and planetary gears, can minimize the power to the CVU. However, a SPCVT with a conventional CVT should possess a dual mode, which would allow the conventional CVT to be used at high speeds and an additional gear train to be used at low speeds. The inner-spherical CVU(ISCVU) with an inner and outer spherical contact mechanism developed in this study can cover the range from low to high speeds. The rated power and the overall speed ratios were 100 kW and $0.09{\sim}0.36$, respectively. Power efficiency was numerically calculated to be over 90% over the speed ratio range of $0.1{\sim}0.29$. The maximum shear stress at the two contact areas of the rotor pairs, the minimum life and the overall size were estimated to be 700 MPa, 276 kh and $350{\times}350{\times}400mm^3$, respectively. This study shows that an ISCVU and a variable bridge type PGU can realize the SPCVT with a single mode for a vehicle.

• Journal of Power Electronics
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• 제17권4호
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• pp.942-952
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• 2017

Modular multilevel converters (MMCs) have been receiving extensive research interest in high/medium-voltage applications due to its modularity, scalability, reliability, high-voltage capability, and excellent harmonic performance. Submodule capacitors are usually rather bulky because they have to withstand fundamental frequency voltage fluctuations. To reduce the capacitance of these capacitors, this study proposes a modified MMC with an active power decoupling circuit within each submodule. The modified submodule contains an auxiliary half bridge, with its capacitor split in two. Also, the midpoints of the half bridge and the split capacitors are connected by an inductor. With this modified submodule, the fundamental frequency voltage fluctuation can be suppressed to a great extent. The second-order voltage fluctuation, which is the second most significant component in submodule voltage fluctuations, is removed by the proper control of the second-order circulating current. Consequently, the submodule capacitance is significantly reduced. The viability and effectiveness of the proposed new MMC are confirmed by the simulation and experimental results. The proposed MMC is best suited for medium-voltage applications where power density is given a high priority.

• 대한전기학회논문지:전력기술부문A
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• 제54권1호
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• pp.43-50
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• 2005

The presence of transmission congestion may reduce the market size and split the bulk power system into smaller systems. Consequently, this can be a key factor to the increase in market price. This paper analyzes the effect of exercising local market power on the market price, and derives a range of indices which quantify the degree and incentive of local market power through statistical analysis in an electricity market with uniform pricing scheme. The applicability and effectiveness of the derived indices on competitive electricity markets are demonstrated on the Korea electricity market.

• Journal of electromagnetic engineering and science
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• 제16권4호
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• pp.199-205
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• 2016

We present a novel schematic using a 3-dB coupler to transmit radiofrequency (RF) power to two receivers selectively. Whereas previous multiple receiver supporting schemes used hardware-switched methods, our scheme uses a soft power-allocating method, which has the advantage of variable power allocation in real time to each receiver. Using our scheme, we can split the charging area and focus the RF power on the targeted areas. We present our soft power-allocating method in three main points. First, we propose a new power distribution hardware structure using a FPGA (field-programmable gate array) and a 3-dB coupler. It can reconfigure the transmitting power to two receivers selectively using accurate FPGA-controlled signals with the aid of software. Second, we propose a power control method in our platform. We can variably control the total power of transmitter using the DC bias of the drain input of the amplifier. Third, we provide the possibility of expansion in multiple systems by extending these two wireless power transfer systems. We believe that this method is a new approach to controlling power amplifier output softly to support multiple receivers.

• 한국항해항만학회지
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• 제26권3호
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• pp.289-294
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• 2002

본 논문에서는 디지털 TV 중계기용 고출력 광대역의 3-Way 전력결합기를 설계.제작하였다. 대역폭 증가와 고출력을 동시에 이루기 위하여 Wilkinson 형태의 전력분배기를 채택하였다. 우선 Wilkinson 전력분배기를 균등(1 : 1) 및 비균등(2 : 1) 분배시켜, 동위상 4 포트 전력결합기를 시뮬레이션 하였다. 시뮬레이션 결과에 따라서 두께 120 mil인 유전체 기판을 사용하여 제작된 전력결합기는 디지털 TV 중계기 주파수 470~806 MHz 대역에서 삽입손실 -6.53dB 이하, 반사계수 -13dB 이하, 포트 간 분리도 -15 dB 이하, 출력 포트 간 위상차가 13$^{\circ}$이하의 특성을 보였다. 새롭게 만든 전력결합기는 회로에서의 고 임피던스로 인한 마이크로스트립 선로 폭의 한계와 고출력의 경우 선로간의 상호작용으로 인한 전력의 손실 및 협대역의 문제를 동시에 개선이 가능함을 알 수 있었다. 나아가서, 제작된 3-Way 결합기의 삽입손실, 반사계수, 포트간의 분리도 및 위상차가 디지털 TV 중계주파수 470~806 MHz에서 양호한 특성을 나타내는 것을 확인함으로써 고출력 및 광대역화가 실현가능하다는 것을 알 수 있었다.

• International Journal of Control, Automation, and Systems
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• 제3권4호
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• pp.533-541
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• 2005

In this paper, a wind turbine with power splitting transmission, which is realized through a novel three-shaft planetary, is presented. The input shaft of the transmission is driven by the rotor of the wind turbine, the output shaft is connected to the grid via the main generator (asynchronous generator), and the third shaft is driven by a control motor with variable speed. The dynamic models of the sub systems of this wind turbine, e.g. the rotor aerodynamics, the drive train dynamics and the power generation unit dynamics, were given and linearized at an operating point. These sub models were integrated in a multidisciplinary dynamic model, which is suitable for control syntheses to optimize the utilization of wind energy and to reduce the excessive dynamic loads. The important dynamic behaviours were investigated and a wind turbine with a soft main shaft was recommend.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.174-177
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• 2001

The dependence of modern life upon the continuous supply of electrical energy makes system reliability and power quality topics of the utmost importance in the power systems. Power quality is the combination of voltage quality and current quality. But in this paper, voltage quality and harmonic distortion are focused. Transient phenomena and current quality are not included. Voltage quality is split into voltage sags. voltage swells, and short interruptions. These voltage variations are studied on their definitions, origins, the effect on electric equipment. Related industrial standards and guidelines are summarized. Harmonic voltage and current distortion are strongly linked. The concepts and contributions of harmonic distortions are studied. Typical symptoms of harmonic problems and a summary of the trends and guidelines are given.