• Journal of IKEEE
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• v.22 no.4
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• pp.1234-1237
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• 2018

For 4H-SiC trench MOSFET which can reduce on-resistance and switching losses compared to 4H-SiC planar MOSFET, the optimization study for decrease of sub-trench was carried out. In order to decrease sub-trench, Ar reshape process was used and trench shapes were observed as a function of temperature and process time. As a result, it was confirmed that the process conditions for $1500^{\circ}C$ and 20 min were most effective for the suitable trench profiles. In addition, dry/wet oxidation was performed at the Ar reshaped-samples to observe the oxidation thickness with different crystal orientations.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.3
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• pp.929-946
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• 2022

Free viewpoint video (FVV) service is an immersive media service that allows a user to watch it from a desired location or viewpoint. It is composed of various forms according to the direction of the viewpoint of the provided video, and includes zoom in/out in the service. As consumers' demand for active watching is increasing, the importance of FVV services is expected to grow gradually. However, additional considerations are needed to seamlessly stream FVV service. FVV includes a plurality of videos, video changes may occur frequently due to movement of the viewpoint. Frequent occurrence of video switching or re-request another video can cause service delay and it also can lower user's quality of service (QoS). In this case, we assumed that if a video showing an object that the user wants to watch is selected and provided, it is highly likely to meet the needs of the viewer. In particular, it is important to provide an object-oriented FVV service when zooming in. When video zooming in in the usual way, it cannot be guaranteed to zoom in around the object. Zoom function does not consider about video viewing. It only considers the viewing screen size and it crop the video view as fixed screen location. To solve this problem, we propose a zoom in/out method of object-centered dynamic adaptive streaming of FVV in this paper. Through the method proposed in this paper, users can enjoy the optimal video service because they are provided with the desired object-based video.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.5
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• pp.959-968
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• 2022

In this paper, we intend to develop a cart with the convenience of moving objects or items that are difficult to hold by the hand of the disabled and the elderly from outdoor activities to a moving location. Using GPS module, DC motor, Bluetooth module, magnetometer sensor, and Blynk application, the smart follow cart was programmed to accurately know the owner's location while following the cart. The values of latitude and longitude of the magnetometer sensor are set so that the correct leverage value can be obtained in the lead for fine adjustment of the start and stop angles so that the user's position can be freely detected. The above motor driver L298n was connected to the motor to drive the DC motor at a fine angle. A smart follow cart was implemented that receives location signals according to the direction of the owner by turning on/off the mobile phone app as a switching role by connecting the GPS through Bluetooth wireless communication using a smartphone.

• Journal of Aerospace System Engineering
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• v.17 no.1
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• pp.10-15
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• 2023

Wet multi-disk clutch, a power switching device of the ducted fan, was optimized and results were analyzed. The clutch was divided into two types depending on whether a mechanical lock-up was applied or not. It was optimized under each design condition. Transfer torque capacity, friction material surface pressure, friction surface temperature, and drag torque were calculated as factors to optimize the clutch. The volume of separator plate and drag torque were used as the objective function for optimization. In the case of Type 1, which did not include a mechanical lock-up, the clutch could be operated regardless of the pitch angle of the ducted fan. However, the outer diameter of the friction surface was doubled, the volume was increased by 5~7 times, and the drag torque was increased by 7~12 times compared to those of Type 2, which included a mechanical lock-up.

• Journal of the Korean Institute of Telematics and Electronics
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• v.23 no.1
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• pp.1-9
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• 1986

This is the third part of the four-part paper describing the development of a packet-switched computer communication network named the KORNET. In this paper we describe the design and implementation of the X.25 protocol connecting packet mode data terminal equipments(PDTE's) with data circuit terminating equipments(DCE's). In the KORNET, the X.25 protocol has been implemented on the line processing module-A(LPMA) of the network node processor(NNP). In the implementation of X.25, we have divided the software module according to the service function, and have determined the the rules that interact between the modules. Each layer protocol has been developed using the technique of the finite state machine. Before the actual coding of softwares, we hafve used formal software development tools based on the specification and description language (SDL) and program design languate (PDL) recommended by the CCITT. In addition, for the efficient operation of the X.25 protocol system we have analyzed the system performance and the service scheduling method of each module. The results will also be given.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.5B
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• pp.471-477
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• 2010

In this study, the variability of the Horton index which is ratio of vaporization and wetting water is investigated using a conceptual soil water balance model. From the proposed model, the steady-state soil water probabilistic density function is derived through meteorological and watershed characteristics and then the sensitivity of Horton index to the precipitation occurrence rate and the mean of wet day precipitation is examined. As a result, the inter-annual variability of the Horton index is lower than that of precipitation and they showed the strong negative correlation. It is also shown that although precipitation is not varied, the Horton index can be varied due to the fluctuation of the precipitation occurrence rate and the mean of wet day precipitation. In addition, it is presented that there is a non-linear relationship which has a critical point switching proportional or inverse relationship between the Horton index and two main characteristics of precipitation process.

• Journal of English Language & Literature
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• v.56 no.3
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• pp.501-517
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• 2010

This paper examines the British imperialism found in Edith Nesbit's fantasy stories by looking at the function of magic and of the hierarchical relationships seen in the books. Although Edith Nesbit is relatively unknown in Korea, she is widely recognized as having had a great influence on the 20th century British literary world, and is also well-known for her political position as a socialist. Nesbit's fantasy books are commonly differentiated from other Victorian children's books written before her in that she created realistic and liberal children characters and rejected the adult didactic tone. While Nesbit's books have been recognized as revolutionary and being distinguished from other Victorian children's books, I suggest that the ideas found in her fantasy novels largely include the dominant Victorian message of British imperialism. This imperial ideology is delivered by the logic of magic and the multilateral hierarchies. The two magic creatures (The Psammead and the Phoenix) and the two magic items from an Oriental background (the Carpet and the Amulet) all have a magic power to grant people's wishes, wholeheartedly exercising their power and knowledge for the sake of the British characters. While the magic agents serve to fulfill the children's wishes, the children aim to please their parents and to benefit their family, showing layered hierarchies among the characters. Also, there is a hierarchical distinction between the magic items and the magic creatures in that the magic items have no voice to express themselves but only serve and obey the British children. The foreign characters that the children encounter in their adventures also cooperate with the British characters to help them to fulfill their goals. In short, magic frees the children from the adult-centered world but ultimately their free adventures serve their parents and other adults, and represent the ideals and hierarchical concepts of British imperialism. Thus, Nesbit's position as a modern writer seems to be ambiguous, switching between modern characterization and style, and the old Victorian imperial messages that also exist in her fantasy novels.

• Advances in nano research
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• v.15 no.6
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• pp.521-531
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• 2023

Quantum-dot cellular automata (QCA) has shown great potential in the nanoscale regime as a replacement for CMOS technology. This work presents a specific approach to static random-access memory (SRAM) cell based on 2:1 multiplexer, 4-bit SRAM array, and 32-bit SRAM array in QCA. By utilizing the proposed SRAM array, a single-layer 16×32-bit SRAM with the read/write capability is presented using an optimized signal distribution network (SDN) crossover technique. In the present study, an extremely-optimized 2:1 multiplexer is proposed, which is used to implement an extremely-optimized SRAM cell. The results of simulation show the superiority of the proposed 2:1 multiplexer and SRAM cell. This study also provides a more efficient and accurate method for calculating QCA costs. The proposed extremely-optimized SRAM cell and SRAM arrays are advantageous in terms of complexity, delay, area, and QCA cost parameters in comparison with previous designs in QCA, CMOS, and FinFET technologies. Moreover, compared to previous designs in QCA and FinFET technologies, the proposed structure saves total energy consisting of overall energy consumption, switching energy dissipation, and leakage energy dissipation. The energy and structural analyses of the proposed scheme are performed in QCAPro and QCADesigner 2.0.3 tools. According to the simulation results and comparison with previous high-quality studies based on QCA and FinFET design approaches, the proposed SRAM reduces the overall energy consumption by 25%, occupies 33% smaller area, and requires 15% fewer cells. Moreover, the QCA cost is reduced by 35% compared to outstanding designs in the literature.

• Journal of the Korea Society of Computer and Information
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• v.28 no.12
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• pp.231-238
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• 2023

For boost PFC (Power Factor Correction) converters, various control methods are being studied to achieve unity power factor and low THD (Total Harmonic Distortion) of AC input current. Among them, average current mode control, which controls the average value of the inductor current to follow the current reference, is the most widely used. However, nowadays, as advanced digital control becomes possible with the development of digital processors, predictive control of boost PFC converters is receiving attention. Predictive control is classified into predictive current mode control, which generates duty in advance using a predictive algorithm, and model predictive current control, which performs switching operations by selecting a cost function based on a model. Therefore, this paper simply explains the average current mode control, predictive current mode control, and model predictive current control of the boost PFC converter. In addition, current control under entire load and disturbance conditions is compared and analyzed through simulation.

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.5
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• pp.463-470
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• 2006

This paper deals with a new 3-phase power quality disturbance generator. The proposed generator can provide phase jump as well as voltage sag, swell, outage, unbalance, and over and under voltage. The operating principle of the generator is described in each mode of disturbance. The magnitude of the phase jump is analysed and it is found that the magnitude is the function of the turn-ratios of the transformers consisting the generator. The scheme has simple structure compared with the conventional one, and the major components of the proposed scheme are SCR thyristor and transformer, which guarantees high reliability and cost-effective implementation of the generator. Furthermore, high efficiency can be obtained because there is no PWM switching of the semiconductor devices, and it is easy to control the system. Simulations are carried out to confirm the operation in each disturbance mode, and experiments has been done with 5kVA power rating. The usefulness of the proposed scheme is verified through simulation and experimental results. It is expected that the scheme can be applied to the performance test of the custom power devices such as UPS, DVR, DSTATCOM, and SSTS with cost-effective system.