• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.02a
• /
• pp.257-257
• /
• 2010

One of the critical issues for applications of flexible organic thin film transistors (OTFTs) for flexible electronic systems is the electrical stabilities of the OTFT devices, including variation of the current on/off ratio ($I_{on}/I_{off}$), leakage current, threshold voltage, and hysteresis, under repetitive mechanical deformation. In particular, repetitive mechanical deformation accelerates the degradation of device performance at the ambient environment. In this work, electrical stabilities of the pentacene organic thin film transistors (OTFTs) employing multi-stack hybrid encapsulation layers were investigated under mechanical cyclic bending. Flexible bottom-gated pentacene-based OTFTs fabricated on flexible polyimide substrate with poly-4-vinyl phenol (PVP) dielectric as a gate dielectric were encapsulated by the plasma-deposited organic layer and atomic layer deposited inorganic layer. For cyclic bending experiment of flexible OTFTs, the devices were cyclically bent up to $10^5$ times with 5mm bending radius. In the most of the devices after $10^5$ times of bending cycles, the off-current of the OTFT with no encapsulation layers was quickly increased due to increases in the conductivity of the pentacene caused by doping effects from $O_2$ and $H_2O$ in the atmosphere, which leads to decrease in the $I_{on}/I_{off}$ and increase in the hysteresis. With encapsulation layers, however, the electrical stabilities of the OTFTs were improved significantly. In particular, the OTFTs with multi-stack hybrid encapsulation layer showed the best electrical stabilities up to the bending cycles of $10^5$ times compared to the devices with single organic encapsulation layer. Changes in electrical properties of cyclically bent OTFTs with encapsulation layers will be discussed in detail.

• Journal of Power Electronics
• /
• v.19 no.1
• /
• pp.190-200
• /
• 2019

The flyback converter, which can be regarded as a nonlinear time-varying system, has complex dynamics and nonlinear behaviors. These phenomena can affect the stability of the converter. To simplify the modeling process and retain the information of the output capacitor branch, a special sampled-data model of a peak current-mode (PCM) controlled flyback converter is established in this paper. Based on this, its dynamic behaviors are analyzed, which provides guidance for designing the circuit parameters of the converter. With the critical stability boundary equation derived by a Jacobian matrix, the stable operation range with a varied output capacitor, proportional coefficient of error the amplifier, input voltage, reference voltage and slope of the compensation ramp of a PCM controlled flyback converter are investigated in detail. Research results show that the duty ratio should be less than 0.5 for a PCM controlled flyback converter without ramp compensation to operate in a stable state. The stability regions in the parameter space between the output capacitor and the proportional coefficient of the error amplifier are enlarged by increasing the input voltage or by decreasing the reference voltage. Furthermore, the ramp compensation also can extend to the stable region. Finally, time-domain simulations and experimental results are presented to verify the theoretical analysis results.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.45 no.4
• /
• pp.57-63
• /
• 2008

In this paper, the dependence of MOSFET performance on the channel stress is characterized in depth. The tensile and compressive stresses are applied to CMOSFET using a nitride film which is used for the contact etch stop layer (CESL). Drain current of NMOS and PMOS is increased by inducing tensile and compressive stress, respectively, due to the increased mobility as well known. In case of NMOS with tensile stress, both decrease of the back scattering ratio ($\tau_{sat}$) and increase of the thermal injection velocity ($V_{inj}$) contribute the increase of mobility. It is also shown that the decrease of the $\tau_{sat}$ is due to the decrease of the mean free path ($\lambda_O$). On the other hand, the mobility improvement of PMOS with compressive stress is analyzed to be only due to the so increased $V_{inj}$ because the back scattering ratio is increased by the compressive stress. Therefore it was confirmed that the device performance has a strong dependency on the channel back scattering of the inversion layer and thermal injection velocity at the source side and NMOS and PMOS have different dependency on them.

• Women's Health Nursing
• /
• v.10 no.3
• /
• pp.190-199
• /
• 2004

This thesis explores the actual circumstances of Korean nursing by investigating its present situations. Ultimately, the intent of this study aims to establish a future direction of Korean Nursing. As such, the current conditions of Korean nursing is analyzed in the following categories: education, practice, research, nursing policy, expansion of nursing field, and entrepreneurship. In the final conclusion, an appropriate orientation of the future of Korean nursing is discussed. There are two primary Nursing programs, a three-year(63) and a four-year(53), in Korean Nursing education. Master's programs are available at 32 nursing schools or 32 professional graduate schools. A total of 15 nursing schools have a doctoral program in Korea. The ratio of graduates between the three-year and four year programs is 76:24. Hence, it is highly encouraged to expand four-year nursing programs, because it will help raise the social status of nursing professionals as well as the quality of nursing. In the clinical nursing field, independency and self regulation are critical. As such, organizational change, implementation of a standardized nursing m information system, appropriate workforce, and improvement of the reimbursement system in nursing is recommended. In community nursing, the following should be resolved to provide better nursing services: improvement of working condition and benefits, establishment of a law enforcing the hiring of nurses, and providing continuing education. The number of nursing research has increased and nursing studies are in great quantity. However, research in practices and theories are more in demanded. Hence, research that integrates theories and practices are very significant. Ultimately, it is critical to support nursing studies that will influence nursing policy. The Korean Nurses Association(KNA) is an organization that supervises the nation's nursing policy. The primary focus of KNA is to combine the three and four year undergraduate education systems into 4 years and to establish the Nursing Practice Act. The Ministry of Health and Welfare has adapted a system to educate and certify nurse specialists in 10 nursing areas in 21 nursing graduate schools expecting high-quality nursing services and a decrease of cost. The government also allowed nurses to operate facilities for health management or welfare agencies.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.8 no.4
• /
• pp.61-66
• /
• 2008

As the water distribution system which is one of the critical lifeline system is deteriorated and pipe failures occur frequently, the more efficient pipe monitoring system becomes a critical issue in the water industry. One of the pipe monitoring systems is called "Smart-pipe System" which is permanent, comprehensive and an automated SIM (Structural Integrity Monitoring) system and has superiorities to existing monitoring system. To implement a smart-pipe system on a water distribution system, assessment of its indirect benefit obtaining from smartpipe such as the ratio of preventing water main failures must be preceded. However, only some researches on this field have been performed. In this paper, the concept of smart-pipe system is compared with the current monitoring systems for a water distribution system, and a method to quantify its benefit using the inconvenient time for customers is suggested. The suggested method was applied to a real water distribution system to estimate its applicability and benefit.

• Progress in Superconductivity
• /
• v.11 no.1
• /
• pp.8-12
• /
• 2009

We investigated the effects of the irradiation of light-ions on the superconducting $MgB_2$ thin films fabricated by using HPCVD. Deuterium and helium ions were irradiated on $MgB_2$ thin films by various doses, from $1{\times}10^{10}cm^{-2}\;to\;8{\times}10^{15}cm^{-2}$. During these experiments some reasonable results and unpredictable results have been obtained. The reasonable results are that the peak of the reduced maximum pinning force shifts by increasing the pinning sites in $MgB_2$ films and the slightly change of critical current density of films. We obtained some unusual results, which are the increasing of the transition temperature and the change of residual resistance ratio. Among the data of deuterium and helium ion irradiation experiments, the results of helium ion irradiation have most notable points so we will discuss mainly about helium irradiation experiments.

• Korean Journal of Human Ecology
• /
• v.17 no.1
• /
• pp.105-114
• /
• 2008

This study aims on observing the social recognition and its aspects for men taking care of their outer appearances at current point where men are rapidly rising as the main consumer in the beauty industry while their interest for outer appearances are increasing. Therefore, we observed the overall trend and changes in social recognition for male looks by analyzing the contents of articles in fashion magazines that play the critical role of spreading the trend while suggesting and delivering the diverse trend changes to the public to correspond to the individual and concrete demands of certain class segmented into gender, age, hobby, and more. As a result, articles related to outer appearances were divided into fashion, cosmetic and skin, hair and scalp, body figure care, cosmetic surgery, and others, and among them, fashion category took up the highest ratio. Also, articles related to outer appearances increased even more according to the change in time, where articles related to fashion and hair increased while articles of other categories decreased.

• 한국초전도학회:학술대회논문집
• /
• v.9
• /
• pp.147-151
• /
• 1999

YBCO step-edge Josephson junction were fabricated on sapphire substrates. The steps were formed on R-plane sapphire substrates by using Ar ion milling with PR masks. The step angle was controlled in the wide range from 25$^{\circ}$ to 50$^{\circ}$ by adjusting both the Ar ion incident angle and the photoresist mask rotation angle relative to the incident Ar ion beam. CeO$_2$ buffer layer and in-situ YBa$_2Cu_3O_{7-{\delta}}$ (YBCO) thin films was deposited on the stepped R-plane sapphire substrates by pulsed laser deposition method. The YBCO film thickness was varied to obtain the ratio of film thickness to step height in the range from 0.5 to 1. The step edge junction exhibited RSJ-like behaviors with I$_cR_n$ product of 100 ${\sim}$ 300 ${\mu}$V, critical current density of 10$^3$ ${\sim}$ 10$^5$ A/ cm$^2$ at 77 K.

• Journal of the Optical Society of Korea
• /
• v.18 no.6
• /
• pp.633-638
• /
• 2014

We report experimental behaviors of condensed $^{87}Rb$ atoms responding to changes in the trap potential of the atomchip. The two-types of adiabatic and non-adiabatic overall changes were implemented by changing the ramp-down speed of the chip-wire current, which can dominantly modify the one-axis magnetic field gradient. Under the adiabatic process, a pure condensate stayed in the initial spin state and collectively oscillated with both monopole and dipole modes, while an atomic cloud above the critical temperature exhibited sound waves in a dense ultracold gas. On the other hand, Bose-Einstein condensate atoms with non-adiabatic perturbation were split into spatially different positions by spin states through spin-flip. We investigated the split ratio among spin states depending on final evaporation frequency. Potential changes, of course, cause collective oscillations regardless of the changing process.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.60 no.1
• /
• pp.27-31
• /
• 2011

In this paper, the electron transport characteristics in $CF_4$ has been analysed over the E/N range 1~300[Td] by a two-term approximation Boltzmann equation method and by a Monte Carlo simulation. The motion has been calculated to give swarm parameters for the electron drift velocity, longitudinal diffusion coefficient, the ratio of the diffusion coefficient to the mobility, electron ionization and attachment coefficients, effective ionization coefficient, mean energy, collision frequency and the electron energy distribution function. The electron energy distribution function has been analysed in $CF_4$ at E/N=5, 10, 100, 200 and 300[Td] for a case of the equilibrium region in the mean electron energy and respective set of electron collision cross sections. The results of Boltzmann equation and Monte Carlo simulation have been compared with experimental data by Y. Nakamura and M. Hayashi. The swarm parameter from the swarm study are expected to serve as a critical test of current theories of low energy electron scattering by atoms and molecules, in particular, as well as crucial information for quantitative simulations of weakly ionized plasmas.