• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.137-137
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• 2009

Thin-film transistors (TFTs) that can be prepared at low temperatures have attracted much attention due to the great potential for flexible electronics. One of the mainstreams in this field is the use of organic semiconductors such as pentacene. But device performance of the organic TFTs is still limited by low field effect mobility or rapidly degraded after exposing to air in many cases. Another approach is amorphous oxide semiconductors. Amorphous oxide semiconductors (AOSs) have exactly attracted considerable attention because AOSs were fabricated at room temperature and used lots of application such as flexible display, electronic paper, large solar cells. Among the various AOSs, a-IGZO was considerable material because it has high mobility and uniform surface and good transparent. The high mobility is attributed to the result of the overlap of spherical s-orbital of the heavy pest-transition metal cations. This study is demonstrated the effect of thickness channel layer from 30nm to 200nm. when the thickness was increased, turn on voltage and subthreshold swing were decreased. a-IGZO TFTs have used a shadow mask to deposit channel and source/drain(S/D). a-IGZO were deposited on SiO2 wafer by rf magnetron sputtering. using power is 150W, working pressure is 3m Torr, and an O2/Ar(2/28 SCCM) atmosphere at room temperature. The electrodes were formed with Electron-beam evaporated Ti(30nm) and Au(70nm) structure. Finally, Al(150nm) as a gate metal was evaporated. TFT devices were heat treated in a furnace at $250^{\circ}C$ in nitrogen atmosphere for an hour. The electrical properties of the TFTs were measured using a probe-station to measure I-V characteristic. TFT whose thickness was 150nm exhibits a good subthreshold swing(S) of 0.72 V/decade and high on-off ratio of 1E+08. Field effect mobility, saturation effect mobility, and threshold voltage were evaluated 7.2, 5.8, 8V respectively.

• Anxiety and mood
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• v.10 no.2
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• pp.95-102
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• 2014

Objective : Previous research showed that childhood trauma or domestic violence resulted in difficulties in controlling emotion and problem solving and vulnerability to psychiatric disorders. To understand the long term effect of childhood trauma, this study investigated their influences on cognitive processing of anger-evoking event and anger behavior among prisoners. Methods : All data were collected from 198 prisoners off our districts in Korea. After they consented to participate, prison officer distributed a questionnaire that included scales to demographic measure, childhood abuse (emotional abuse, physical abuse, and neglect), cognitive response of anger (attentional focus, suspicion, rumination, and hostile attitude) and behavior of anger (impulsive reaction, verbal aggression, physical confrontation, and indirect expression). For statistical analyses, SPSS 18.0 were used and path coefficients were evaluated from the structural equational modeling using LISREL 8.52. Results : Almost 50% of prisoners of our sample experienced one or more trauma during childhood. Then we tested the long term effect of childhood trauma on anger response by structural equation modeling. As expected, childhood trauma was associated with cognitive processing of anger-evoking event and anger behavior. More specifically, emotional abuse (${\beta}$=0.21, p<0.01) predicted suspicion which in turn associated with impulsive reaction (${\beta}$=0.73, p<0.001) and verbal aggression (${\beta}$=0.87, p<0.001). Emotional abuse (${\beta}$=0.24, p<0.01) also predicted hostile attitude which associated with physical confrontation (${\beta}$=0.80, p<0.001) and indirect expression (${\beta}$=0.80, p<0.001). Interestingly, physical abuse associated directly with impulsive reaction (${\beta}$=0.23, p<0.01) and indirect expression (${\beta}$=0.17, p<0.05). Neglect predicted rumination (${\beta}$=0.15, p <0.05) which associated with indirect expression marginally (${\beta}$=0.11, P<0.10). Conclusion : The results of this study, suggest longitudinal and harmful effect of childhood trauma on difficulties in controlling anger. Especially, it was revealed that childhood abuse related with processing anger evoking events more suspicious and hostile and then various anger-expressing behaviors.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.55-55
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• 2009

Silicon Carbide (SiC) is a material with a wide bandgap (3.26eV), a high critical electric field (~2.3MV/cm), a and a high bulk electron mobility (${\sim}900cm^2/Vs$). These electronic properties allow high breakdown voltage, high frequency, and high temperature operation compared to Silicon devices. Although various SiC DMOSFET structures have been reported so far for optimizing performances. the effect of channel dimension on the switching performance of SiC DMOSFETs has not been extensively examined. In this paper, we report the effect of the interface states ($Q_s$) on the transient characteristics of SiC DMOSFETs. The key design parameters for SiC DMOSFETs have been optimized and a physics-based two-dimensional (2-D) mixed device and circuit simulator by Silvaco Inc. has been used to understand the relationship with the switching characteristics. To investigate transient characteristic of the device, mixed-mode simulation has been performed, where the solution of the basic transport equations for the 2-D device structures is directly embedded into the solution procedure for the circuit equations. The result is a low-loss transient characteristic at low $Q_s$. Based on the simulation results, the DMOSFETs exhibit the turn-on time of 10ns at short channel and 9ns at without the interface charges. By reducing $SiO_2/SiC$ interface charge, power losses and switching time also decreases, primarily due to the lowered channel mobilities. As high density interface states can result in increased carrier trapping, or recombination centers or scattering sites. Therefore, the quality of $SiO_2/SiC$ interfaces is important for both static and transient properties of SiC MOSFET devices.

• Journal of architectural history
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• v.10 no.4 s.28
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• pp.43-55
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• 2001

Living spaces are the results of social environment and also the reflection of the viewpoints by their residents toward human culture and society. Therefore, in studying living spaces, the true essence of the spaces could be easily distorted when cultural and symbolic motives and values are disregarded and only their apparent characteristics are looked into. Hence, it's necessary to simultaneously understand both physical dwelling spaces from architecture's view points and social ideas, simultaneously, of people who form and interact with the spaces. Hence, this paper tries to study housing religion which is one of shamanistic religions which, in turn, have been the fundamental element of ancient religions and came into existence on the basis of dwelling spaces. This study presumes that house religion may have been permeated with its creators' ideas about living and those ideas could be one of those factors which plays a role in organizing of dwelling spaces. As such, with these prior analyses, this thesis attempts to understand the meaning of various dwelling spaces via the characteristics and functionalities of various house spirits which are mentioned in a local house religion and also will find out spatial harmony of Korean traditional living spaces by way of corelations among living spaces, people, and personalized house spirits. Almost all traditional Korean houses have assigned a house spirit to their individual dwelling space. This means a traditional house was considered as a scared space in a secular world called human society and the space was actually intended to protect sacredness of dwelling places from earthliness outside. So when the hierarchy of house spirits in housing religion is projected to a Korean traditional house, it can be shown that a dwelling house as a building was personified to a respectable human status. In other words, it can be concluded that each space was synonymous with a dwelling place for each house spirit and was considered a sacred godly place. In a nutshell, not only each space in a Korean traditional house was a physical and functional space, but also it formed a scared spatial place along with the concept of house spirits intending to ward off disasters and enjoy a comfortable life through those religious symbols and meanings. Housing shamanistic religion which has long been existing with residents and their lives is seeped with the viewpoints of the residents toward life, and hence understanding the meanings and organization of Korean traditional housing can reveal commonly practiced principles of spatial organization of the traditional houses. Therefore an analysis of Korean traditional housing on the basis of humanistic social ideas will help learn Korea's traditional houses which need to be understood in various methods.

• Journal of Distribution Science
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• v.14 no.12
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• pp.71-78
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• 2016

Purpose - This paper is for the Analysis on the Hindrance Factors and Activation Scheme by the Type of Distribution Channel in Direct transaction of Agricultural Products. As the distribution structure of agricultural products has become changable, farmers seem to use the type of direct distribution in order to enhance the receiving price. This study aims to explore the hindrance factors and income variation rate in direct transaction of agricultural produces, specifically focusing on the 167 farmers. Research design, data, and methodology - To ascertain the hindrance factors exactly by the type of distribution channel, the managements were classified by four subcategories, that is high sales percentage with shopping malls, SNS, shopping malls and SNS, and off-line direct transaction. Results - As a result of the hypothesis test, hinderance factors in online direct deal activation were found to be in the order of the difficulty in continuous content production, the difficulty in shopping mall operation and maintenance, and the difficulty in card commission problems, and in the order of the difficulties in continuous content production, the difficulty in continuous content production, the difficulty in shopping mall operation and maintenance, and the difficulty in branding for the SNS group. Thus, it can be seen that the difficulty in continuous content production, shopping mall operation and maintenance were found to be the biggest obstacles. In addition, hindering factors in online direct deal activation were found to be in the order of the difficulty in credit card settlement, the difficulty in publicity, and the difficulty in dealing with unsold goods. The group with high sales rate in shopping mall was found to be increased by 23.9% in the gross income compared to the previous year, the group with high SNS sales ratio increased by 56.5%, the group with direct offline transaction increased by 37.1%, among which the group with the highest increase rate of SNS sales ratio was found to be the highest from the rate of increase/decrease of the income, which was statistically significant. Conclusions - It can be suggested that government and local government may provide agricultural management with supporting plan which in turn can activate direct transaction in any possible ways.

• Journal of the Korean association of regional geographers
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• v.2 no.2
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• pp.93-102
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• 1996

The Korean Peninsula is located on the east coast of monsoon Asia of the midlatitude, where the Pacific polar front moves. As a result variations of spatial and temporal distribution of precipitation occur. A great variation of precipitation during the summer months created frequent droughts and floods. The purpose of this study is to identify distributional characteristics and to analyze synopic characteristics of summer droughts in Korea. The research methods used are ; (1) to identify droughts based on the anomaly of monthly precipitation during summer of 1994. (2) to analyze correlations between drought and weather systems by using the calender of rain days. (3) to compare a synoptic mechanism of summer droughts with that of typical normal summer. The characteristics of summer droughts of 1994 may be summarized as follows ; 1) While most regions were affected by the droughts some regions displayed specific characteristics. The southern part of the Korean Peninsula was severely affected during the month of June. August droughts severely affected east part of the Sobek Mountains, thus showing that the droughts of June and August are highly localized. 2) In the pressure anomaly of surface field. the positive anomaly appears in June around Korean Peninsula, but in July when all parts of the South Korea were under severe droughts, the anomaly changes and becomes negative. 3) Extracyclones occurred less frequently in the summer of 1994. Those that did occur were located in areas far off the Korean Peninsula having little consequences on the drought patterns. 4) The trough of westerly wave at 500hPa height patterns in June is located far from the eastern sea of Korean Peninsula, but in July and August Korean Peninsula belongs to ridge of westerly wave. 5) In June the positive height anomaly at 500hPa surface appears zonally from Siberia to the western Parts of North Pacific Ocean, and in July and August, the strong positive anomaly appears around Korean Peninsula. As a result the zonal index of westerlies at during each month of summer in Korean sector has a large value, which in turn implies that drought will prevails when zonal flow is strong.

• Journal of IKEEE
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• v.11 no.4
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• pp.158-164
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• 2007

In this study, three types of a novel Trench IGBTs(Insulated Gate Bipolar Transistor) are proposed. The first structure has P-collector which is isolated by $SiO_2$ layer to enhance anode-injection-efficiency and enable the device to have a low on-state voltage drop(Von). And the second structure has convex P-base region between both gates. This structure may be effective to distributes electric-field crowded to gate edge. So this structure can have higher breakdown voltage(BV) than conventional trench-type IGBT(TIGBT). The process and device simulation results show improved on-state, breakdown and switching characteristics in each structure. The first one was presented lower on state voltage drop(2.1V) than that of conventional one(2.4V). Also, second structurehas higher breakdown voltage(1220V) and faster turn off time(9ns) than that of conventional structure. Finally, the last one of the proposed structure has combined the two structure (the first one and second one). This structure has superior electric characteristics than conventional structure about forward voltage drop and blocking capability, turnoff characteristics.

• JSTS:Journal of Semiconductor Technology and Science
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• v.14 no.5
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• pp.601-608
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• 2014

In this paper, we have characterized the electrical properties related to gate leakage current in AlGaN/GaN MISHFETs with varying the thickness (0 to 10 nm) of $Al_2O_3$ gate insulator which also serves as a surface protection layer during high-temperature RTP. The sheet resistance of the unprotected TLM pattern after RTP was rapidly increased to $1323{\Omega}/{\square}$ from the value of $400{\Omega}/{\square}$ of the as-grown sample due to thermal damage during high temperature RTP. On the other hand, the sheet resistances of the TLM pattern protected with thin $Al_2O_3$ layer (when its thickness is larger than 5 nm) were slightly decreased after high-temperature RTP since the deposited $Al_2O_3$ layer effectively neutralizes the acceptor-like states on the surface of AlGaN layer which in turn increases the 2DEG density. AlGaN/GaN MISHFET with 8 nm-thick $Al_2O_3$ gate insulator exhibited extremely low gate leakage current of $10^{-9}A/mm$, which led to superior device performances such as a very low subthreshold swing (SS) of 80 mV/dec and high $I_{on}/I_{off}$ ratio of ${\sim}10^{10}$. The PF emission and FN tunneling models were used to characterize the gate leakage currents of the devices. The device with 5 nm-thick $Al_2O_3$ layer exhibited both PF emission and FN tunneling at relatively lower gate voltages compared to that with 8 nm-thick $Al_2O_3$ layer due to thinner $Al_2O_3$ layer, as expected. The device with 10 nm-thick $Al_2O_3$ layer, however, showed very high gate leakage current of $5.5{\times}10^{-4}A/mm$ due to poly-crystallization of the $Al_2O_3$ layer during the high-temperature RTP, which led to very poor performances.

• Journal of the Korean Vacuum Society
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• v.12 no.4
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• pp.239-250
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• 2003

The reliability degradation phenomena in the SiGe hetero-junction bipolar transistor (HBT) are investigated in this review. In the case of the SiGe HBT the decrease of the current gain, the degradation of the AC characteristics, and the offset voltage are frequently observed, which are attributed to the emitter-base reverse bias voltage stress, the transient enhanced diffusion, and the deterioration of the base-collector junction due to the fluctuation in fabrication process, respectively. The reverse-bias stress on the emitter-base junction causes the recombination current to rise, increasing the base current and degrading the current gain, because hot carriers formed by the high electric field at the junction periphery generate charged traps at the silicon-oxide interface and within the oxide region. Because of the enhanced diffusion of the dopants in the intrinsic base induced by the extrinsic base implantation, the shorter distance between the emitter-base junction and the extrinsic base than a critical measure leads to the reduction of the cut-off frequency ($f_t$) of the device. If the energy of the extrinsic base implantation is insufficient, the turn-on voltage of the collector-base junction becomes low, in the result, the offset voltage appears on the current-voltage curve.

• JSTS:Journal of Semiconductor Technology and Science
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• v.7 no.3
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• pp.196-208
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• 2007

An analytical model is proposed for an optically controlled Metal Semiconductor Field Effect Transistor (MESFET), known as Optical Field Effect Transistor (OPFET) considering the diffusion fabrication process. The electrical parameters such as threshold voltage, drain-source current, gate capacitances and switching response have been determined for the dark and various illuminated conditions. The Photovoltaic effect due to photogenerated carriers under illumination is shown to modulate the channel cross-section, which in turn significantly changes the threshold voltage, drainsource current, the gate capacitances and the device switching speed. The threshold voltage $V_T$ is reduced under optical illumination condition, which leads the device to change the device property from enhancement mode to depletion mode depending on photon impurity flux density. The resulting I-V characteristics show that the drain-source current IDS for different gate-source voltage $V_{gs}$ is significantly increased with optical illumination for photon flux densities of ${\Phi}=10^{15}\;and\;10^{17}/cm^2s$ compared to the dark condition. Further more, the drain-source current as a function of drain-source voltage $V_{DS}$ is evaluated to find the I-V characteristics for various pinch-off voltages $V_P$ for optimization of impurity flux density $Q_{Diff}$ by diffusion process. The resulting I-V characteristics also show that the diffusion process introduces less process-induced damage compared to ion implantation, which suffers from current reduction due to a large number of defects introduced by the ion implantation process. Further the results show significant increase in gate-source capacitance $C_{gs}$ and gate-drain capacitance $C_{gd}$ for optical illuminations, where the photo-induced voltage has a significant role on gate capacitances. The switching time ${\tau}$ of the OPFET device is computed for dark and illumination conditions. The switching time ${\tau}$ is greatly reduced by optical illumination and is also a function of device active layer thickness and corresponding impurity flux density $Q_{Diff}$. Thus it is shown that the diffusion process shows great potential for improvement of optoelectronic devices in quantum efficiency and other performance areas.