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Atomic Layer Deposition of HfO2 Thin Films on Ultrathin SiO2 Formed by Remote Plasma Oxidation
Seokhoon Kim,전형탁,Hyungchul Kim,Inhoe Kim,Keunwoo Lee,Sanghyun Woo,Taeyong Park,Wooho Jeong 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.4
An ultrathin SiO₂ layer was grown on a H-terminated Si substrate by using remote plasma oxidation. The subsequent HfO₂ deposition on the ultrathin SiO₂ was achieved by a remote plasma atomic layer deposition (RPALD). During the HfO₂ film deposition and rapid thermal annealing (RTA), the ultrathin SiO₂ buffer layer effectively suppressed the formation of Hf silicate layers in the interfacial region. The Hf silicate layer in the interfacial region grew with increasing RTA temperature. The positive fixed oxide charges in the HfO₂ film were reduced with increasing RTA temperature. The thickness of the HfO₂ films with an ultrathin SiO₂ buffer layer showed a lower effective fixed oxide charge density (Qf,eff) due to the shift of the flat band voltage (VFB) toward the positive direction, compared to those with H-terminated Si. The thin interfacial layer of the HfO₂ films with a thin SiO₂ buffer layer resulted in a low equivalent oxide thickness (EOT) value. The leakage current densities of the HfO₂ films increased because of the crystallization of the HfO₂ film after RTA. An ultrathin SiO₂ layer was grown on a H-terminated Si substrate by using remote plasma oxidation. The subsequent HfO₂ deposition on the ultrathin SiO₂ was achieved by a remote plasma atomic layer deposition (RPALD). During the HfO₂ film deposition and rapid thermal annealing (RTA), the ultrathin SiO₂ buffer layer effectively suppressed the formation of Hf silicate layers in the interfacial region. The Hf silicate layer in the interfacial region grew with increasing RTA temperature. The positive fixed oxide charges in the HfO₂ film were reduced with increasing RTA temperature. The thickness of the HfO₂ films with an ultrathin SiO₂ buffer layer showed a lower effective fixed oxide charge density (Qf,eff) due to the shift of the flat band voltage (VFB) toward the positive direction, compared to those with H-terminated Si. The thin interfacial layer of the HfO₂ films with a thin SiO₂ buffer layer resulted in a low equivalent oxide thickness (EOT) value. The leakage current densities of the HfO₂ films increased because of the crystallization of the HfO₂ film after RTA.
Communicating Healthy Food Choice
Sang-Yeon Kim,Jennifer Morey Hawkins,Hayeon Song,Tae-Seop Lim,Emily McCarthy. Cramer,Seokhoon Ahn,Jihyun Kim,Hyun-Joo Kim,Junghyun Kim,Hiroshi Ota 한국언론학회 2016 Asian Communication Research Vol.13 No.1
This research examines cultural influence on the preference of promotive (i.e., trying to eat more healthy foods) and preventive (i.e., trying to avoid unhealthy foods) dietary practices. Survey data were collected from students and older adults in Korea (N = 287) and the U.S. (N = 245). Only students participated in the survey in Japan (N = 145). Consistent with the prediction, Study 1 shows Korean mature adults are more willing to adopt preventive dietary practices, while American counterparts favor promotive eating habits. The pattern of the data was inconsistent with the prediction among student participants across the three nations. Individual-level data from Study 2 (N = 284) confirm that independent self-construal affects promotive dietary practice via increasing promotive regulatory self-focus. The indirect impact of interdependent self-construal on preventive dietary practice was less apparent. Practical implications for doctor-patient communication are discussed.
Energy Efficient MAC Scheme for Wireless Sensor Networks with High-Dimensional Data Aggregate
Kim, Seokhoon,Joh, Hangki,Choi, Seungjun,Ryoo, Intae Hindawi Limited 2015 Mathematical problems in engineering Vol.2015 No.-
<P>This paper presents a novel and sustainable medium access control (MAC) scheme for wireless sensor network (WSN) systems that process high-dimensional aggregated data. Based on a preamble signal and buffer threshold analysis, it maximizes the energy efficiency of the wireless sensor devices which have limited energy resources. The proposed group management MAC (GM-MAC) approach not only sets the buffer threshold value of a sensor device to be reciprocal to the preamble signal but also sets a transmittable group value to each sensor device by using the preamble signal of the sink node. The primary difference between the previous and the proposed approach is that existing state-of-the-art schemes use duty cycle and sleep mode to save energy consumption of individual sensor devices, whereas the proposed scheme employs the group management MAC scheme for sensor devices to maximize the overall energy efficiency of the whole WSN systems by minimizing the energy consumption of sensor devices located near the sink node. Performance evaluations show that the proposed scheme outperforms the previous schemes in terms of active time of sensor devices, transmission delay, control overhead, and energy consumption. Therefore, the proposed scheme is suitable for sensor devices in a variety of wireless sensor networking environments with high-dimensional data aggregate.</P>
Traffic management in the mobile edge cloud to improve the quality of experience of mobile video
Kim, Seokhoon,Kim, Dae-Young,Park, Jong Hyuk Elsevier 2018 Journal of Computer Communications Vol.118 No.-
<P><B>Abstract</B></P> <P>The use of mobile network traffic is increasing due to the development of communication devices such as smart phones. Data traffic accounts for more than voice traffic. Video traffic accounts for the largest proportion of mobile data traffic and this proportion is increasing. However, various mobile environments affect the status of the mobile network and limit the provision of video services using the Internet. Therefore, a method for improving the quality of experience (QoE) of a video service in mobile environments is required. This paper presents a traffic management method using the mobile edge cloud. The mobile edge cloud is placed in the mobile edge network and monitors the status of mobile terminals. Through the mobile edge cloud, it becomes possible to effectively manage the traffic of mobile terminals by the network. The proposed method manages video traffic from the content server on the Internet according to the edge network status and mobility of a mobile terminal, and provides video traffic to mobile terminals. This method, using the mobile edge cloud, leads to improvement of the QoE for mobile video users. The superiority of this method compared to currently available systems was validated by computer simulation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> This paper provides a traffic management method using the mobile edge cloud. The mobile edge cloud is placed in the mobile edge network and monitors the status of mobile terminals. Through the mobile edge cloud, it becomes possible to manage the traffic of mobile terminals effectively by the network. </LI> <LI> The proposed method manages video traffic from the content server in the Internet according to the edge network status and mobility of a mobile terminal and provides the video traffic to the mobile terminals. </LI> <LI> The proposed method using the mobile edge cloud leads to improvement of the QoE of mobile video users. </LI> <LI> By computer simulation, the superiority is validated. </LI> </UL> </P>
Adaptive data rate control in low power wide area networks for long range IoT services
Kim, Dae-Young,Kim, Seokhoon,Hassan, Houcine,Park, Jong Hyuk Elsevier 2017 Journal of computational science Vol.22 No.-
<P><B>Abstract</B></P> <P>Internet of Things (IoT) technologies can provide various intelligent services by collecting information from objects. To collect information, Wireless Sensor Networks (WSNs) are exploited. The Low Power Wide Area Network (LPWAN), one type of WSN, has been designed for long-range IoT services. It consumes low power and uses a low data rate for data transmission. The LPWAN includes several communication standards, and Long Range Wide Area Network (LoRaWAN) is the representative standard of the LPWAN. LoRaWAN provides several data rates for transmission and enables adaptive data rate control in order to maintain network connectivity. In the LoRaWAN, the wireless condition is considered by the reception status of the acknowledgement (ACK) message, and adaptive data rate control is performed according to the wireless condition. Because the judgment of the wireless condition by the reception status of ACK messages does not reflect congestion, adaptive data rate control can lead to inefficiency in data transmission. For efficient data transmission in long-range IoT services, this paper proposes a congestion classifier using logistic regression and modified adaptive data rate control. The proposed scheme controls the data rate according to the congestion estimation. Through extensive analysis, we show the proposed scheme’s efficiency in data transmission.</P> <P><B>Highlights</B></P> <P> <UL> <LI> In this paper, the necessity of congestion estimation in long range IoT applications is described. Congestion Classifier using Logistic Regression and the modified adaptive data rate control scheme is designed. </LI> <LI> For the validation of the efficiency of the data transmission, analysis on the transmission delay is carried out. Results show that the proposed method outperforms state of the art methods. </LI> <LI> In this way, the proposal improves transmission efficiency in aspect of the transmission delay in wireless environment where congestion occurs. </LI> <LI> Our proposed method predicts congestion status by learning and determines whether a node drops data rate or not. Thus, it leads to avoiding unnecessary change of data rate. </LI> <LI> Through analysis on transmission delay, the proposed scheme has shown that it is the proper data rate control method for IoT networking in congestion environment. </LI> </UL> </P>