• Management & Information Systems Review
• /
• v.4
• /
• pp.327-348
• /
• 2000

There are three major motives for M&A, financial synergy effect, operating & managerial synergy effect, and tax effect. The purpose of this study is to prove the operating & managerial synergy effect of M&A. To do this, we analyze the market-ripple effect of M&A, focusing on the increase in market power. Specifically we use cross-sectional data from 1985 to 1998 to show whether a market power of mergers is higher than that of a matched non-merging control group. we use time series data to show whether a market power of merger is higher than that of pre-merger. Also we use the event study using market model to show the stock price movement after mergers. The result is that although revenue increase after mergers, profit of the firms does not improve after mergers. Also there is sufficient evidence to say that there is a cumulative abnormal return for the firms after mergers.

• Proceedings of the KIEE Conference
• /
• 2006.07d
• /
• pp.2061-2062
• /
• 2006

a-Si(amorphous silicon) TFT(thin film transistor)는 TFT-LCD(liquid crystal display)의 화소 스위칭(switching) 소자로 폭넓게 이용되고 있다. 현재는 a-Si을 이용하여 gate drive IC를 기판에 집적하는 ASG(amorphous silicon gate) 기술이 연구, 적용되고 있는데 이때 가장 큰 제약은 문턱 전압(Vth)의 이동이다. 특히 고온에서는 문턱 전압의(Vth) 이동이 가속화 되고, Ioff current가 증가 하게 되고, 저온($0^{\circ}C$)에서는 전류 구동능력이 상온($25^{\circ}C$) 상태에서 같은 게이트 전압(Vg)에 대해서 50% 수준으로 감소하게 된다. 특히 ASG 회로는 여러 개의 TFT로 구성되는데, 각각의 TFT가 고온에서 Vth shift 값이 다르게 되어 설계시 예상하지 못 한 고온에서의 화면 무너짐 현상 즉 고온 노이즈 불량이 발생 할 수 있다. 고온 노이즈 불량은 고온에서의 각 TFT의 문턱전압 및 $I_D-V_G$ 특성을 측정한 결과 고온 노이즈 불량에 영향을 주는 인자가 TFT의 width와 기생 capacitor비 hold TFT width가 영향을 주는 것으로 실험 및 시뮬레이션 결과 확인이 되었다. 발생 mechanism은 ASG 회로는 AC 구동을 하기 때문에 Voff 전위에 ripple이 발생 되는데 특히 고온에서 ripple이 크게 증가 하여 출력 signal에 영향을 주어 불량이 발생하는 것을 규명하였다.

• Korean Journal of Optics and Photonics
• /
• v.15 no.3
• /
• pp.214-221
• /
• 2004

We theoretically and experimentally investigate the effect of apodization on the transmission characteristics of linearly chirped fiber Bragg gratings(CFBGs). Based on the UV beam scanning method along a phase mask, we fabricated several apodized CFBGs with different apodization profiles such as Gaussian, Raised-cosine, Blackman, and Hyperbolic tangent. During the UV beam scanning, the phase mask is dithered by a PZT(Piezoelectric transducer) which is precisely controlled by a computer program so that the apodization profiles can be flexibly applied to the grating. We measured the reflection spectra and group delay characteristics of CFBGs with the different apodization profiles, and compared them according to their properties such as reflectivity, sidelobes, and group delay ripple (GDR). The peak-to-peak of GDR could be suppressed to less than 20 ps.

• Journal of Advanced Navigation Technology
• /
• v.12 no.6
• /
• pp.611-618
• /
• 2008

The development of information society together with information telecommunication's influence on the human society is a ripple effect and getting wider. Among those ripple effects the disaster prevention is in the public eye in the present day. On the way to the ubiquitous society the main techniques to be concerned in ubiquitous sensor networks are the field of damage of storm and flood, safety facilities, traffic safety, industrial safety, energy safety, fire fighting, specific safety of radioactivity escape incident, environmental pollution, sea pollution, mountain and forrest disaster so on. In this paper the USN technique based on the disaster prevention communication technology service and its requirement technology and application are studied.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.9 no.4
• /
• pp.381-389
• /
• 2004

In this paper, it is suggested that instantaneous compensation PWM control for inverter without the smoothing capacitor Therefore, this inverter system has several advantages. It has small volume and low price to manufacture, decrease trouble rate of inverter, and has power factor correction effect because huge smoothing capacitor-less. And it has compact size control circuit to use analog integrator device. It could make the smoothing capacitor-less inverter for air-blower motor by using the instantaneous compensation PWM controller. This inverter system has small volume and value compare with the conventional VVVF control inverter.

• Journal of IKEEE
• /
• v.20 no.3
• /
• pp.314-317
• /
• 2016

Recently, efforts to maximize battery life in progress with an increase in the demand for portable devices. In this paper, we propose multi-phase buck converter with fast transient response. Multi-phase buck converter may be used for the output capacitor of small size because the ripple cancellation effect, it is possible to use an inductor having an inductance less. The portable device for quick change from standby mode to active 4-phase design structure was given a fast transient response. The proposed multi-phase buck converter was fabricated using a 0.18 um CMOS process and the supply voltage ranges from 2.7V to 3.3V, the maximum load current is 500mA and settling time is 10us.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.48 no.9
• /
• pp.476-483
• /
• 1999

In this paper, electromagnetic forces acting on the rotor surface of a BLDC motor for hard disk drive are calculated by the finite element field analysis. The frequency characteristics of torque ripple, local force and unbalanced magnetic force as a source of mechanical vibration area analyzed. Ring-type permanent magnets for the brushless DC motor are apt to have different magnetization levels at each pole because of the unbalanced air gap between the magnet surface and the magnetizer fixture during the multi-poles magnetizing process. This paper discusses the effect of the unsymmetric magnetization distribution in the permanent magnet on the brushless DC motor performances. As a result, the unbalanced magnetic force acting on the rotor surface and the torque ripple are examined for the motor with an unsymmetric magnetization distribution, and compared with those of an ideally symmetric motor.

• Journal of Power Electronics
• /
• v.13 no.3
• /
• pp.349-361
• /
• 2013

As a result of the advantages such as high efficiency, continuous current and high stability margin, push-pull converter with continuous current (PPCWCC) is competitive for battery discharge regulator (BDR) which plays an important role in power conditioning unit (PCU). Leakage inductance yields current spike in low-ripple current of PPCWCCs. The operating modes are added due to leakage inductance. Therefore the steady state performance is affected, which is embodied in the spike of low-ripple current. PPCWCCs which are suitable for BDR can be separated into three types by current spike characteristics. Three representative topologies IIs1, IIcb2 and Is3 are analyzed in order to investigate the factors on the magnitude and duration of spike. Equivalent current sampling method (ECSM) which eliminates the sampling time delay and achieves excellent dynamic performance is adopted to prevent the spike disturbance on current sampling. However, ECSM reduces the sampling accuracy and telemetry accuracy due to neglecting the spike. In this paper, ECSM used in PPCWCCs is summarized. The current sampling error is analyzed in quality and quantity, which provides the foundation for offsetting and enhancing the telemetry accuracy. Finally, current sampling error rate of three topologies is compared by experiment results, which verify the theoretical analysis.

• Journal of Power Electronics
• /
• v.19 no.1
• /
• pp.220-233
• /
• 2019

This work aims to study and analyze the various operating modes of universal power converter which is powered by solar and thermoelectric generators. The proposed converter is operated in a DC-DC (buck or boost mode) and DC-AC (single phase) inverter with high efficiency. DC power sources, such as solar photovoltaic (SPV) panels, thermoelectric generators (TEGs), and Li-ion battery, are selected as input to the proposed converter according to the nominal output voltage available/generated by these sources. The mode of selection and output power regulation are achieved via control of the metal-oxide semiconductor field-effect transistor (MOSFET) switches in the converter through the modified stepped perturb and observe (MSPO) algorithm. The MSPO duty cycle control algorithm effectively converts the unregulated DC power from the SPV/TEG into regulated DC for storing energy in a Li-ion battery or directly driving a DC load. In this work, the proposed power sources and converter are mathematically modelled using the Scilab-Xcos Simulink tool. The hardware prototype is designed for 200 W rating with a dsPIC30F4011 digital controller. The various output parameters, such as voltage ripple, current ripple, switching losses, and converter efficiency, are analyzed, and the proposed converter with a control circuit operates the converter closely at 97% efficiency.

• Asia-Pacific Journal of Business
• /
• v.13 no.3
• /
• pp.343-359
• /
• 2022

We analyze the regional ripple effects of both the sale prices and cheonsei prices using the global VAR(GVAR) model. The interest rate shock causes the regional sale prices to fall. Moreover, the greatest responses to the shock are those of Gangnam-gu, etc. because of there were many transactions for investment purpose. When interest rate rose, the cheonsei price in Gangnam-gu reacted greatly. Conversely, if interest rates fall, the cheonsei demand to live in Gangnam-gu increases. Furthermore, the response of sale price to the interest rate shock are greater than those of the cheonsei prices. Whereas, a positive shock on the sale price in Gangnam-gu increases the sale price there. It also raises the sale prices of the surrounding area in a similar pattern. The shock on the sale price in Gangnam-gu also increases the cheonsei price in Gangnam-gu. In addition, an increase in the sale price in Gangnam-gu leads to increases of cheonsei prices in other regions. Therefore, the recent rise of the base rate can negatively affect the sale prices, and thus a decrease in the sale price spreads to the surrounding areas. Accordingly, it is time for policy alternatives to make a soft landing in sale prices.