• Journal of Communications and Networks
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• v.18 no.3
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• pp.364-374
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• 2016

With vast amounts of spectrum available in the millimeter wave (mmWave) band, small cells at mmWave frequencies densely deployed underlying the conventional homogeneous macrocell network have gained considerable interest from academia, industry, and standards bodies. Due to high propagation loss at higher frequencies, mmWave communications are inherently directional, and concurrent transmissions (spatial reuse) under low inter-link interference can be enabled to significantly improve network capacity. On the other hand, mmWave links are easily blocked by obstacles such as human body and furniture. In this paper, we develop a multi-hop relaying transmission (MHRT) scheme to steer blocked flows around obstacles by establishing multi-hop relay paths. In MHRT, a relay path selection algorithm is proposed to establish relay paths for blocked flows for better use of concurrent transmissions. After relay path selection, we use a multi-hop transmission scheduling algorithm to compute near-optimal schedules by fully exploiting the spatial reuse. Through extensive simulations under various traffic patterns and channel conditions, we demonstrate MHRT achieves superior performance in terms of network throughput and connection robustness compared with other existing protocols, especially under serious blockage conditions. The performance ofMHRT with different hop limitations is also simulated and analyzed for a better choice of the maximum hop number in practice.

• Journal of the Korean Institute of Navigation
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• v.24 no.1
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• pp.13-22
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• 2000

The collisions at sea among marine casualties are not reduced as the tonnage and speed of ship's increase as well as the traffic quantity increase at sea, in spite of the improvement of nautical equipment, enforcement of crew's education and training as well as improvement of quality standard according to the implementation of ISM code. The measures to prevent the collisions at sea are simple, and are composed of six stage.: The first stage is that the officer on duty detect the target from his eye or radar information. The second stage is determining the type and kind of target-ship. The third stage is target tracking; calculation of target speed, course, CPA and TCPA from radar information or visual check. The fourth stage is determination of vessel in danger after calculation of third stage. The fifth stage is the judgement of situation if own ship is stand-on or give way vessel according to the 1972 COLREG. The last stage is to carry out proper action according to 1972 COLREG, under the circumstances. But by the case, the situations are so different under the different external conditions; for example, natural/navigational conditions, crew's human factors, ship's particular, rule or regulation, management system on board, the condition of watch keeping. Therefore the reasons and casualties are so complicated. This study aims to investigate the collision casualty at sea which needs to clarity all these causal factors of afore-mentioned, and to analyze the causes of problems so as to utilize them to establish the measures of preventing marine accidents. This study, described the concepts of causal factors into three groups; environmental factor, and company/on board management system and navigator's act. Also described how to investigate and analyzes the casual factors. Even though it was described in this paper how to detect the causal factors and reasons of collisions, and how to analyze the inter-relation of each causal factors, it is necessary to do further study how to analyze between the liability of concerned parties and the casual factors involved.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.3542-3547
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• 2015

There is commonly used the full depth excavation method of sewer pipeline maintenance in Korea. This induces couple of technical and social problems like increase of construction cost and time for excavation and backfill, increase of public complains and delay of traffic, and so force. In order to overcome these problems, lots of laboratory tests were carried out for sewer pipeline of maintenance materials with trenchless methods. The testing materials are liquid and hardened polyurethane, and polyurethane CIPP. The lab tests were followed by Korean Standard. There are no side effects, like harmless to the human body and air pollution with stink. Judging from the limited test results, all the items tested were satisfied the KS criteria.

• Health Policy and Management
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• v.25 no.3
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• pp.149-151
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• 2015

United Nations (UN) adopted 17 global sustainable development agenda to the year 2030 in the 68th general assembly on september, 2015. The global agendas and goals are important for 3 reasons: (1) to adopt the international standard for determining the health status; (2) to identify areas in need of attention; and (3) to advance international cooperation regarding health issues. In the area of infectious diseases, our goals include the eradication of human immunodeficiency virus infection and acquired immune deficiency syndrome, tuberculosis, and malaria as well as a substantial reduction of hepatitis by the year 2030. In the area of non-communicable diseases, our goal is to reduce premature mortality (${\leq}70years$) at least 30% by the year 2030. Preventive activities such as smoking cessation, alcohol abstinence, nutritional measures, and physical activities, should also be promoted intensively nationwide. It is also necessary to establish stringent policies for control hypertension, diabetes, obesity, and hypercholesterolemia. Additionally, environmental health, injury by traffic accident, mental health, and drug and alcohol abuse are important health policies. Furthermore, in the area of international health and cooperation, maternal and child health remain important areas of support for underdeveloped countries. Education and training towards the empowerment of health professionals in underdeveloped countries is also an important issue. The global agenda prioritize resources(manpower and budget) allocation of international organizations such as UN, World Health Organization, United Nations Development Programme, and World Bank. The global agenda also sets the contribution levels of Official Developmental Assistance donor countries. Health professionals such as professors and researchers will have to turn their attention to areas of vital international importance, and play an important role in implementation strategies and futhermore guiding global agenda.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.13 no.4
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• pp.57-62
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• 2014

Recently, research activities to develop services for providing safety information to the drivers in fast moving vehicles based on various wireless network technologies such as DSRC (Dedicated Short Range Communication), IEEE 802.11p WAVE (Wireless Access for Vehicular Environment) are widely being carried out. This paper presents a proof-of-concept model based on a robot-car for Dilemma Zone Decision Assistant Service using the wireless LAN technology. The proposed model system consists of a robot-car based on an embedded Linux OS equipped with a WiFi interface and an on-board unit emulator, an Android-based remote controller to model a human driver interface, a laptop computer to run a model traffic signal controller and signal lights, and a WiFi access point to model a road-side unit.

• Wind and Structures
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• v.24 no.6
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• pp.579-611
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• 2017

Bora is a strong, usually dry temporally and spatially transient wind that is common at the eastern Adriatic Coast and many other dynamically similar regions around the world. One of the Bora main characteristics is its gustiness, when wind velocities can reach up to five times the mean velocity. Bora often creates significant problems to traffic, structures and human life in general. In this study, Bora velocity and near-ground turbulence are studied using the results of three-level high-frequency Bora field measurements carried out on a meteorological tower near the city of Split, Croatia. These measurements are analyzed for a period from April 2010 until June 2011. This rather long period allows for making quite robust and reliable conclusions. The focus is on mean Bora velocity, turbulence intensity, Reynolds shear stress and turbulence length scale profiles, as well as on Bora velocity power spectra and thermal stratification. The results are compared with commonly used empirical laws and recommendations provided in the ESDU 85020 wind engineering standard to question its applicability to Bora. The obtained results report some interesting findings. In particular, the empirical power- and logarithmic laws proved to fit mean Bora velocity profiles well. With decreasing Bora velocity there is an increase in the power-law exponent and aerodynamic surface roughness length, and simultaneously a decrease in friction velocity. This indicates an urban-like velocity profile for smaller wind velocities and a rural-like velocity profile for larger wind velocities. Bora proved to be near-neutral thermally stratified. Turbulence intensity and lateral component of turbulence length scales agree well with ESDU 85020 for this particular terrain type. Longitudinal and vertical turbulence length scales, Reynolds shear stress and velocity power spectra differ considerably from ESDU 85020. This may have significant implications on calculations of Bora wind loads on structures.

• Journal of the Korea Society of Computer and Information
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• v.25 no.4
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• pp.189-195
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• 2020

The whole world is anxious that aircraft could be used as a tool for terrorism after 9/11. The disappearance of Malaysia Airlines is again adding to fears about aircraft. Because these aircraft attacks cause many human casualties, the purpose of the study is to analyze the problems in the current air security system and to present alternatives. The methodology of the study used a literature research methodology to review the current status of aircraft terrorism and related regulations, such as current aviation-related laws and anti-terrorism laws, and prior studies. The purpose of the Chapter is to present an aviation security system that promotes the safety of air traffic through the prevention of aircraft terror by presenting the roles and improvement measures of aviation security personnel, foreign police officers, intelligence agencies, and legal blind spots and flaws.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.6
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• pp.121-126
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• 2018

IEEE 802.1 TSN TG is developing standards for end-to-end delay bounds and zero packet loss based on Ethernet technology. We focus on packet forwarding techniques. TSN packet forwarding techniques can be classified into Synchronous and Asynchronous framework. Synchronous approach allocates fixed time period for a class, yet is complex for large networks. Asynchronous approach provides delay guarantee by regulator-scheduler pair, yet is unnecessarily complex, too. We propose network components for TSN Asynchronous architecture, which remove the complexity of maintaining flow state for regulation decisions. Despite such a simplicity, the proposed architecture satisfies the TSN's delay requirements provided the limited high priority traffic's maximum packet length.

• Smart Structures and Systems
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• v.24 no.2
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• pp.243-256
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• 2019

Determination of the most meaningful structural modes and gaining insight into how these modes evolve are important issues for long-term structural health monitoring of the long-span bridges. To address this issue, modal parameters identified throughout the life of the bridge need to be compared and linked with each other, which is the process of mode tracking. The modal frequencies for a long-span bridge are typically closely-spaced, sensitive to the environment (e.g., temperature, wind, traffic, etc.), which makes the automated tracking of modal parameters a difficult process, often requiring human intervention. Machine learning methods are well-suited for uncovering complex underlying relationships between processes and thus have the potential to realize accurate and automated modal tracking. In this study, Gaussian mixture model (GMM), a popular unsupervised machine learning method, is employed to automatically determine and update baseline modal properties from the identified unlabeled modal parameters. On this foundation, a new mode tracking method is proposed for automated mode tracking for long-span bridges. Firstly, a numerical example for a three-degree-of-freedom system is employed to validate the feasibility of using GMM to automatically determine the baseline modal properties. Subsequently, the field monitoring data of a long-span bridge are utilized to illustrate the practical usage of GMM for automated determination of the baseline list. Finally, the continuously monitoring bridge acceleration data during strong typhoon events are employed to validate the reliability of proposed method in tracking the changing modal parameters. Results show that the proposed method can automatically track the modal parameters in disastrous scenarios and provide valuable references for condition assessment of the bridge structure.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.1
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• pp.63-68
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• 2019

Emerging applications such as Smart factory, in-car network, wide area power network require strict bounds on the end-to-end network delays. Flow-based scheduler in traditional Integrated Services (IntServ) architecture could be possible solution, yet its complexity prohibits practical implementation. Sub-optimal class-based scheduler cannot provide guaranteed delay since the burst increases rapidly as nodes are passed by. Therefore a leaky-bucket type regulator placed next to the scheduler is being considered widely. This paper proposes a simple server that achieves both fair scheduling and traffic regulation at the same time. The performance of the proposed server is investigated, and it is shown that a few msec delay bound can be achieved even in large scale networks.