• Smart Structures and Systems
• /
• v.4 no.5
• /
• pp.655-666
• /
• 2008

In the past 20 years, seismic isolation has see a variety of applications in design of structures to mitigate seismic hazard. In particular, isolation has been seen as a means of achieving enhanced seismic performance objectives, such as those for hospitals, critical emergency response facilities, mass electronic data storage centers, and similar buildings whose functionality following a major seismic event is either critical to the public welfare or the financial solvency of an organization. While achieving these enhanced performance objectives is a natural (and oftentimes requisite) application of seismic isolation, little attention has been given to the extension of current design practice to isolated buildings which may have more conventional performance objectives. The development of a rational design methodology for isolated buildings requires thorough investigation of the behavior of isolated structures subjected to seismic input of various recurrence intervals, and which are designed to remain elastic only under frequent events. This paper summarizes these investigations, and proposed a consistent probabilistic framework within which any combination of performance objectives may be met. Analytical simulations are presented, the results are summarized. The intent of this work is to allow a building owner to make informed decisions regarding tradeoffs between superstructure performance (drifts, accelerations) and isolation system performance. Within this framework, it is possible to realize the benefits of designing isolated buildings for which the design criteria allows consideration of multiple performance goals.

• Earthquakes and Structures
• /
• v.12 no.1
• /
• pp.35-45
• /
• 2017

The current paper investigates the effect of the seismic pounding of neighboring buildings on the response of structures isolated by Triple Friction Pendulum Bearing (TFPB). To this end, a symmetric three-dimensional single story building is modeled for analysis with two specified levels of top deck and base deck, to capture the seismic response of the base isolators and building's roof. Linear elastic springs with different level of gaps are employed to calculate the impact between the buildings. Nonlinear Dynamic Time History Analyses (NDTHA) are conducted for seismic evaluation. Also, five different sizes with four different sets of friction coefficients are assumed for base isolators to cover a whole range of base isolation systems with various geometry configurations and fundamental period. The results are investigated in terms of base shear, buildings' drift and top deck acceleration of the superstructure. The results also indicate the profound effect of the stiffness of the adjacent buildings on the value of the impact they impose to the superstructure. Also, in situations of potential pounding, the increment of the fundamental period of the TFPB base isolator could intensify the impact force up to nearly five-fold.

• Journal of Power Electronics
• /
• v.14 no.6
• /
• pp.1119-1129
• /
• 2014

This study proposes a novel five-level three-phase hybrid-clamped converter composed of only six switches and one flying capacitor (FC) per phase. The capacitor-voltage-drift phenomenon of the converter under the classical sinusoidal pulse width modulation (SPWM) strategy is comprehensively analyzed. The average current, which flows into the FC, is a function of power factor and modulation index and does not remain at zero. Thus, a specific modulation strategy based on space vector modulation (SVM) is developed to balance the voltage of DC-link and FCs by injecting a common-mode voltage. This strategy applies the five-segment method to synthesize the voltage vector, such that switching losses are reduced while optional vector sequences are increased. The best vector sequence is then selected on the basis of the minimized cost function to suppress the divergence of the capacitor voltage. This study further proposes a startup method that charges the DC-link and FCs without any additional circuits. Simulation and experimental results verify the validity of the proposed converter, modulation strategy, and precharge method.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.18 no.3
• /
• pp.264-268
• /
• 2005

A 2.2-inch QCIF+(176${\times}$RGB${\times}$220) TFT-LCD with integrated row driver was developed using a standard amorphous silicon TFT technology. At low temperature, the integrated row driver operation is dramatically effected by the electron drift mobility reduction(■50 %) and the threshold voltage shift (■1V) of the a-Si TFT. We studied the dependency of circuit design and found that higher on-current circuit is important to guarantee good operation in wide temperature range.

• 제어로봇시스템학회:학술대회논문집
• /
• 2005.06a
• /
• pp.720-723
• /
• 2005

Ship motion is a complex controlled process with several hydrodynamic parameters that vary in wide ranges with respect to ship load condition, speed and surrounding conditions (such as wind, current, tide, etc.). Therefore, to effectively control ships in a designed track is always an important task for ship masters. This paper presents an effective adaptive autopilot ships that ensure the optimal accuracy, economy and stability characteristics. The PID control methodology is modified and parameters of a PID controller is designed to satisfy conditions for an optimal objective function that comprised by heading error, resistance and drift during changing course, and loss of surge velocity or fuel consumption. Designing of the controller for course changing process is based on the Model Reference Adaptive System (MRAS) control theory, while as designing of the automatic course keeping process is based on the Self Tuning Regulator (STR) control theory. Simulation (using MATLAB software) in various disturbance conditions shows that in comparison with conventional PID autopilots, the designed autopilot has several notable advantages: higher course turning speed, lower swing of ship bow even in strong waves and winds, high accuracy of course keeping, shorter time of rudder actions smaller times of changing rudder direction.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.12 no.1
• /
• pp.46-52
• /
• 2012

Separate extraction of source ($R_S$) and drain ($R_D$) resistances caused by process, layout variations and long term degradation is very important in modeling and characterization of MOSFETs. In this work, we propose "Avalanche Hot-Source Method (AHSM)" for simple separated extraction of $R_S$ and $R_D$ in a single device. In AHSM, the high field region near the drain works as a new source for abundant carriers governing the current-voltage relationship in the MOSFET at high drain bias. We applied AHSM to n-channel MOSFETs as single-finger type with different channel width/length (W/L) combinations and verified its usefulness in the extraction of $R_S$ and $R_D$. We also confirmed that there is a negligible drift in the threshold voltage ($V_T$) and the subthreshold slope (SSW) even after application of the method to devices under practical conditions.

• Korean Journal of Materials Research
• /
• v.13 no.5
• /
• pp.313-316
• /
• 2003

The new epitaxial base cell as a high efficiency Si solar cell was fabricated and the effect of buried contact on the cell characteristics was investigated. In our experiments, the cell with buried contact showed the open circuit voltage of 0.62 V, the short circuit current of 40 mA, the fill factor of 0.7, and the efficiency of 10% under the incident light of AM-1 100 ㎽/$\textrm{cm}^2$. The insertion of buried contact in the epitaxial base structure brought the fabricated cell to the efficiency improvement of about 33%. The cell proposed in this paper has the structural superiority in the fabrication of high efficiency solar cell due to the carrier drift transport in the optical absorption region and the formation of back surface field by $p^{－}$ $p^{+}$ epitaxial base, and the reduction of emitter series resistance by n＋ buried contact.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.11a
• /
• pp.559-562
• /
• 2004

A 2.2-inch QCIF+ $(176{\times}RGB{\times}220)$ TFT-LCD with integrated row driver was developed using a standard amorphous silicon TFT technology. At low temperature $({\sim}-20^{\circ}C)$, the integrated row driver operation is dramatically effected by the electron drift mobility variation $({\sim}50%)$ and the threshold voltage shift $({\sim}1V)$ of the a-Si TFT. We studied the temperature dependency of the circuit design and found that higher on-current circuit is important to guarantee good operation in wide temperature range.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.5 no.1
• /
• pp.29-36
• /
• 1999

A field experiment of the leeway of person-in-water(man with wetsuit) was conducted during October 1997∼ April 1998. The experiment area was northeast side of Cho Do island in Pusan. The college students whose weight ranges 60∼87 kg, height 170∼178 cm were actually drifted for the experiment. The person-in-water wore 5 mm neoprene diving wetsuit to prevent heat loss of the body. The current near the target was measured using a colored vinyl bag. To compare the result a scuba diver equipped with scuba gear and with his BC(buoyancy compensator) fully inflated was drifted alongside. The average leeway speed of man with wetsuit and that of scuba diver were about 0.4 percent and 1.3% of the 10 m wind speed above the water respectively.

• Proceedings of the Optical Society of Korea Conference
• /
• 2000.02a
• /
• pp.284-285
• /
• 2000

광굴절률 현상은 optical signal processing과 홀로그램 기억소자로 널리 응용 될 수 있기 때문에 지금까지 광범위하게 연구되어져 왔다. 광굴절률 현상에서 중요한 변수는 빛이 있는 동안 drift, diffusion 과 photovoltaic current와 같은 전하 운반 메카니즘을 통해서 local charge의 재분포에 따른 공간전하장(Space-charge field, $E_{sc}$ )이다. 지금까지 single beam에 의한 공간전하장을 측정하는 방법으로 birefringenc $e^{1.2}$ 와 interference metho $d^{3}$을 이용하여 굴절률 변화를 측정함으로써 얻을 수 있었다. 그러나 이런 방법들은 공간전하장의 변화를 측정하기위해서 전기광학계수를 측정하여 얻는 간접적인 방법이고 또한 실험방법도 다소 복잡하다. 따라서 본 투고에서는 이미 발표된 광굴절률 현상시 제 2 고조파 세기(SHG)의 변화로부터 공간전하장을 간단하게 측정하는 방법을 이용하여 congruent, MgO가 4mole%, F $e_2$O가 0.1mole% 첨가된 LiNb $O_3$ 단결정의 공간전하장에 대해서 연구를 하였다. 이 방법은 전기광학물질인 LiNb $O_3$에서 SHG 위상정합조건이 dc 전기장에 의존하는 성질을 이용한 것이다. 그리고 온도가 일정할 경우 전기장의 변화에 따라 SHG의 크기가 변함을 이용하였다. (중략)