• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.11 no.6
• /
• pp.631-637
• /
• 2018

In 5G mobile communication, it is necessary to provide different mobility to user equipments(UE) that do not require mobility management or need limited mobility management. In this paper, we propose a two-layer mobility management system that classifies multiple MTC devices with similar mobility levels into c-MTC and m-MTC groups. In order to improve the energy efficiency and service life by reducing the number of control signals generated when TAU is performed, the group header typically performs a Tracking Area Update(TAU) request and adjusts the periodic TAU update period according to the mobility level. The TAU update period of the m-MTC is set to 54 minutes proposed by the 3GPP standard and the c-MTC is set to 12 minutes. Compared to when the UEs perform TAU individually, it is found that the number of control signals decreases by 33% when the MME is not changed and by 49% when the MME is not changed in the m-MTC or c-MTC group.

• Integrative Medicine Research
• /
• v.3 no.4
• /
• pp.204-210
• /
• 2014

The aim of this review was to understand the effects of ${\beta}$-adrenergic stimulation on oxidative stress, structural remodeling, and functional alterations in the heart and cerebral artery. Diverse stimuli activate the sympathetic nervous system, leading to increased levels of catecholamines. Long-term overstimulation of the ${\beta}$-adrenergic receptor (${\beta}AR$) in response to catecholamines causes cardiovascular diseases, including cardiac hypertrophy, stroke, coronary artery disease, and heartfailure. Although catecholamines have identical sites of action in the heart and cerebral artery, the structural and functional modifications differentially activate intracellular signaling cascades. ${\beta}AR$-stimulation can increase oxidative stress in the heart and cerebral artery, but has also been shown to induce different cytoskeletal and functional modifications by modulating various components of the ${\beta}AR$ signal transduction pathways. Stimulation of ${\beta}AR$ leads to cardiac dysfunction due to an overload of intracellular $Ca^{2+}$ in cardiomyocytes. However, this stimulation induces vascular dysfunction through disruption of actin cytoskeleton in vascular smooth muscle cells. Many studies have shown that excessive concentrations of catecholamines during stressful conditions can produce coronary spasms or arrhythmias by inducing $Ca^{2+}$-handling abnormalities and impairing energy production in mitochondria, In this article, we highlight the different fates caused by excessive oxidative stress and disruptions in the cytoskeletal proteome network in the heart and the cerebral artery in responsed to prolonged ${\beta}AR$-stimulation.

• Journal of Astronomy and Space Sciences
• /
• v.35 no.4
• /
• pp.253-261
• /
• 2018

Korea Astronomy and Space Science Institute (KASI) has been developing the space optical and laser tracking (SOLT) system for space geodesy, space situational awareness, and Korean space missions. The SOLT system comprises satellite laser ranging (SLR), adaptive optics (AO), and debris laser tracking (DLT) systems, which share numerous subsystems, such as an optical telescope and tracking mount. It is designed to be capable of laser ranging up to geosynchronous Earth orbit satellites with a laser retro-reflector array, space objects imaging brighter than magnitude 10, and laser tracking low Earth orbit space debris of uncooperative targets. For the realization of multiple functions in a novel configuration, the SOLT system employs a switching mirror that is installed inside the telescope pedestal and feeds the beam path to each system. The SLR and AO systems have already been established at the Geochang station, whereas the DLT system is currently under development and the AO system is being prepared for testing. In this study, the design and development of the SOLT system are addressed and the SLR data quality is evaluated compared to the International Laser Ranging Service (ILRS) tracking stations in terms of single-shot ranging precision. The analysis results indicate that the SLR system has a good ranging performance, to a few millimeters precision. Therefore, it is expected that the SLR system will not only play an important role as a member of the ILRS tracking network, but also contribute to future Korean space missions.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.41 no.4
• /
• pp.179-188
• /
• 2018

Recently, blockchain technology has been recognized as one of the most important issues for the 4th Industrial Revolution which can be represented by Artificial Intelligence and Internet of Things. Cryptocurrency, named Bitcoin, was the first successful implementation of blockchain, and it triggered the emergence of various cryptocurrencies. In addition, blockchain technology has been applied to various applications such as finance, healthcare, manufacturing, logistics as well as public services. Distributed consensus algorithm is an essential component in blockchain, and it enables all nodes belonging to blockchain network to make an agreement, which means all nodes have the same information. For example, Bitcoin uses a consensus algorithm called Proof-of-Work (PoW) that gives possession of block generation based on the computational volume committed by nodes. However, energy consumption for block generation in PoW has drastically increased due to the growth of computational performance to prove the possession of block. Although many other distributed consensus algorithms including Proof-of-Stake are suggested, they have their own advantages and limitations, and new research works should be proposed to overcome these limitations. For doing this, above all things, we need to establish an evaluation method existing distributed consensus algorithms. Based on this motivation, in this work, we suggest and analyze assessment items by classifying them as efficiency and safety perspectives for investigating existing distributed consensus algorithms. Furthermore, we suggest new assessment criteria and their implementation methods, which can be used for a baseline for improving performance of existing distributed consensus algorithms and designing new consensus algorithm in future.

• Journal of Service Research and Studies
• /
• v.8 no.3
• /
• pp.1-23
• /
• 2018

This study suggests a way through Hong Kong as an alternative strategy for Korean companies to enter Chinese service market which is rapidly expanding due to China's recent policy switch toward service economy. Service market is generally more regulated, labor-intensive, and domestic demand-oriented than goods market, which makes opening of domestic markets to foreigners slow. In case of China, market control and regulations by the State is tighter than other economies. Therefore, it is important to find ways to avoid regulations from the Chinese government if possible. In this sense, this study investigates the China-Hong Kong CEPA and draws its strategic value for entering Chinese service market by comparing it with the Korea-China FTA service sector. In addition, utilizing the difference in tax agreements between Korea-China and China-Hong Kong, and the human network of Hong Kong entrepreneurs in China may play an important role in reducing the risk that might arise in China.

• Journal of Korean Society of Rural Planning
• /
• v.25 no.3
• /
• pp.45-57
• /
• 2019

This study aims to explore the policy directions to apply and activate the appropriate technology in rural areas from the perspective of the endogenous and sustainable regional development theories. To this end, according to the analysis framework based on ideas, values, and strategies that are common to both endogenous regional development strategic theories and sustainable regional development theories, in this paper, various surveys and reviews were conducted on the study areas to explore the possibility of localization of the appropriate technology. The policy implications derived from research results are as follows; first, rural areas have high potential and scalability to apply and activate the appropriate technology, particularly in the field of renewable energy, due to their nature based on local resources. Second, for the practical application of the appropriate technology, first of all, together with the establishment of the role of public sector, it is necessary to plan the projects based on the cooperation network of the relevant innovation entities within and outside the regions and to build the implementation systems. Third, the training system for high skilled manpower and indigenous entrepreneurs should be stably built in order to create independent conditions, which are key elements for growth of the appropriate technology. Fourth, there is a need to find the market and establish policies that can solve the typical economic problems of rural areas such as aging population, depopulation and decline in youth, economic unrest. Fifth, in order for the appropriate technology to contribute to socio-economic innovations and the revitalization of the virtuous circle economy in the region, technical items and various business items suitable for the industrial infrastructures and autonomous conditions of rural areas are essential.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.30 no.6
• /
• pp.326-336
• /
• 2018

Continuous measurement of nearshore waves around Korea over long period is very demanding to setup plans for prevention of disasters of port and coastal structures. In this respect, a new web-based system, termed as WINK, was established, which collects nearshore wave data from Korea Meteorological Agency (KMA), Korea Hydrographic and Oceanographic Agency (KHOA), and Ministry of Oceans and Fisheries (MOF) and provide them after quality control of the data. This paper describes technical aspects regarding collection and selection of the wave observation data, construction of wave hindcasting data, the methodology of quality control for the selected wave data, and overall process of building the web-based data providing system.

• Korean Journal of Remote Sensing
• /
• v.37 no.1
• /
• pp.85-95
• /
• 2021

Recently, as data mining and artificial neural network techniques are developed, analyzing large amounts of data is proposed to reduce the dimension of the data. In general, empirical orthogonal function (EOF) used to reduce the dimension in the ocean data and recently, Self-organizing maps (SOM) algorithm have been investigated to apply to the ocean field. In this study, both algorithms used the monthly Sea level anomaly (SLA) data from 1993 to 2018 around the East Asia Coasts. There was dominated by the influence of the Kuroshio Extension and eddy kinetic energy. It was able to find the maximum amount of variance of EOF modes. SOM algorithm summarized the characteristic of spatial distributions and periods in EOF mode 1 and 2. It was useful to find the change of SLA variable through the movement of nodes. Node 1 and 5 appeared in the early 2000s and the early 2010s when the sea level was high. On the other hand, node 2 and 6 appeared in the late 1990s and the late 2000s, when the sea level was relatively low. Therefore, it is considered that the application of the SOM algorithm around the East Asia Coasts is well distinguished. In addition, SOM results processed by SLA data, it is able to apply the other climate data to explain more clearly SLA variation mechanisms.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.19 no.3
• /
• pp.73-82
• /
• 2009

This paper proposes an efficient and secure user authentication and key agreement scheme instead of the HTTP digest and TLS between the SIP UA and server. Although a number of security schemes for authentication and key exchange in SIP network are proposed, they still suffer from heavy computation overhead on the UA's side. The proposed scheme uses the HTIP Digest authentication and employs the Diffie-Hellman algorithm to protect user password against dictionary attacks. For a resource-constrained SIP UA, the proposed scheme delegates cryptographically computational operations like an exponentiation operation to the SIP server so that it is more efficient than the existing schemes in terms of energy consumption on the UA. Furthermore, it allows the proposed scheme to be easily applied to the deployed SIP networks since it does not require major modification to the signaling path associated with current SIP standard.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.14 no.12
• /
• pp.4946-4960
• /
• 2020

In a device-to-device (D2D) underlaid cellular network, there exist two types of co-channel interference. One type is inter-layer interference caused by spectrum reuse between D2D transmitters and cellular users (CUEs). Another type is intra-layer interference caused by spectrum sharing among D2D pairs. To mitigate the inter-layer interference, we first derive the interference limited area (ILA) to protect the coverage probability of cellular users by modeling D2D users' location as a Poisson point process, where a D2D transmitter is allowed to reuse the spectrum of the CUE only if the D2D transmitter is outside the ILA of the CUE. To coordinate the intra-layer interference, the spectrum sharing criterion of D2D pairs is derived based on the (signal-to-interference ratio) SIR requirement of D2D communication. Based on this criterion, D2D pairs are allowed to share the spectrum when one D2D pair is far from another sufficiently. Furthermore, to maximize the energy efficiency of the system, a resource allocation scheme is proposed according to weighted graph coloring theory and the proposed ILA restriction. Simulation results show that our proposed scheme provides significant performance gains over the conventional scheme and the random allocation scheme.