• Journal of Communications and Networks
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• v.16 no.4
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• pp.397-406
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• 2014

Radio frequency (RF) jamming is a denial of service attack targeted at wireless networks. In resource-hungry scenarios with constant traffic demand, jamming can create connectivity problems and seriously affect communication. Therefore, the vulnerabilities of wireless networks must be studied. In this study, we investigate a particular type of RF jamming that exploits the semantics of physical (PHY) and medium access control (MAC) layer protocols. This can be extended to any wireless communication network whose protocol characteristics and operating frequencies are known to the attacker. We propose two efficient jamming techniques: A low-data-rate random jamming and a shot-noise based protocol-aware RF jamming. Both techniques use shot-noise pulses to disrupt ongoing transmission ensuring they are energy efficient, and they significantly reduce the detection probability of the jammer. Further, we derived the tight upper bound on the duration and the number of shot-noise pulses for Wi-Fi, GSM, and WiMax networks. The proposed model takes consider the channel access mechanism employed at the MAC layer, data transmission rate, PHY/MAC layer modulation and channel coding schemes. Moreover, we analyze the effect of different packet sizes on the proposed jamming methodologies. The proposed jamming attack models have been experimentally evaluated for 802.11b networks on an actual testbed environment by transmitting data packets of varying sizes. The achieved results clearly demonstrate a considerable increase in the overall jamming efficiency of the proposed protocol-aware jammer in terms of packet delivery ratio, energy expenditure and detection probabilities over contemporary jamming methods provided in the literature.

• The KIPS Transactions:PartA
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• v.16A no.1
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• pp.43-54
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• 2009

With the emergence of ubiquitous computing era, it has become increasingly important for a middleware which takes full advantage of HCI factors to support user-centric services. Many kinds of studies on HCI-friendly middleware for supporting user-centric services have been performed. However, previous studies have problems in supporting HCI factors, which are needed for user-centric services. In this paper, we present an agent-based intelligent middleware, which is called AIM, that provides user-centric services in ubiquitous HCI environments. We describe the middleware requirements for user-centric services by analyzing various HCI-friendly middleware and design AIM middleware which effectively supports various HCI factors such as context information management, pattern inference of user's behavior, and dynamic agent generation, etc. We introduce service scenarios based on the user's modalities in smart spaces. Finally, prototype implementation is illustrated as a manifestation of the benefits of the introduced infrastructure.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.3B
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• pp.91-99
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• 2008

In this paper, we design the function of ULSLE(Upper Layer Shared LAN Emulation) to provide both the efficient LAN service and compatibility with 802.1D bridge in Hybrid two-stage AWG based WDM-PON. The ULSLE layer lies above MAC control layer in order to provide a mean to interface WDM-PON and 802.1D bridge. It also performs LAN emulation based on PON-Tag which is only used to decide both the transmission mode and the destination of frames transmitted from ONUs. That is, the PON-Tag is not used for downstream frames but destination address field in original frame instead. This decreases the processing overhead and complexity caused by PON-Tag at OLT and ONU. The verification of designed ULSLE is performed according to the specific scenarios based on transmission mode and destination using OPNET.

• Perspectives in Nursing Science
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• v.5 no.1
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• pp.59-71
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• 2008

e-Health/u-Health has generally been considered as an expansion of current medical and medical relevant segments. However. as e-Health/u-Health has been known to have typical attributes and characteristics of services supporting a physically and mentally well-balanced life of its users, we can rationally assume that e-Health/u-Health can be not only an expansion of the existing medical field but also a result of the complex and sophisticated convergence among diverse industries such as the ICT industry. traditional care-relevant segments, etc. Thus, in this study, we carefully and cautiously consider e-Health/u-Health in accordance with both possible scenarios: 1) an expansion of a typical industry, and 2) a result of a convergence among various industries. The advent of new technologies, rapid development of current technologies, and convergence trends in various fields are creating dramatic innovations in the next generation health services market. Consumerism as a characteristic of c-Health/u-Health can be expected to find a solution of the existing healthcare service problems. In the initial phase. mainly due to the absence of a vanguard, as well as to various legalistic and regulative limitations, the role of the government would be immensely critical for the successful early settlement of the e-Health/u-Health industry. Both the government and private sector need to practice continuous and effective public education and publicity mainly to increase the overall recognition and usability of e-Health/u-Health services. Nursing as a unique professional discipline should be well aware of the new paradigm shift of the healthcare market, and make maximum use of the possibility of this trend to the advent of the professional nursing's new role.

• Journal of the Korea Society of Computer and Information
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• v.20 no.5
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• pp.41-51
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• 2015

In order to hide their identities, intruders on the Internet often attack targets indirectly by staging their attacks through intermediate hosts known as stepping stones. In this paper, we propose a brute-force technique to detect the stepping stone behavior on a Linux server where some shell processes remotely logged into using interactive services are trying to connect other hosts using the same interactive services such as Telnet, Secure Shell, and rlogin. The proposed scheme can provide an absolute solution even for the encrypted connections using SSH because it traces the system calls of all processes concerned with the interactive service daemon and their child processes. We also implement the proposed technique on a CentOS 6.5 x86_64 environment by the ptrace system call and a simple shell script using strace utility. Finally the experimental results show that the proposed scheme works perfectly under test scenarios.

• Journal of the Korea Society for Simulation
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• v.20 no.3
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• pp.119-127
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• 2011

Overhaul and repair service means the sequential processes of disassembly, repair and reassembly for a product which has been used for a long time. Overhaul is required for the companies producing airplanes, ships, trains, military weapons and heavy industrial equipments which are very expensive and have a long life cycle. The most important performance measure of the overhaul repair shop is usually the lead time. Thus, how to design the manufacturing system to meet the delivery date is a major concern in overhaul repair shop. This paper introduces the case study of an overhaul repair shop producing military weapon systems with the 3D simulation tool, $QUEST^{TM}$. At first, the characteristics of overhaul shop and what should be considered for simulation modeling are explained. Then, various simulation scenarios including two types of disassembly systems, one is flow line system and the other is cell system, are discussed with the results of simulation experiments.

• Journal of the Korea Convergence Society
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• v.11 no.3
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• pp.37-43
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• 2020

Smartphone-based localization has been widely studied in many different scenarios. But as far as we know, few work has addressed the problem of localization in underground public transportation systems, where GPS signal and wireless infrastructure are not always available. Knowing the location of a train is necessary to develop a useful service for subway passengers. And so, estimation of motion state and stop station by using sensors on a smartphone is being studied for subway passengers. This paper proposes a localization method that uses a barometer and a magnetic sensor on a smartphone. The method proposed in this paper first estimates whether the train runs or stops according to the change in air pressure and the strength of the magnetic field. The altitude value and the magnetic field value are then used to estimate the exact stop station of the train. We evaluated the proposed method using data from the Seoul's subway line 5. Compared with previous methods, the proposed method achieves higher accuracy.

• Computers and Concrete
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• v.20 no.4
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• pp.369-380
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• 2017

The effects of the vertical component of a ground motion on the earthquake performances of semi-ductile high-rise R/C structures were investigated in the present study. Linear and non-linear time-history analyses were conducted on an existing in-service R/C building for the loading scenarios including and excluding the vertical component of the ground motion. The ratio of the vertical peak acceleration to the horizontal peak acceleration (V/H) of the ground motion was adopted as the main parameter of the study. Three different near-source earthquake records with varying V/H ratio were used in the analyses. The linear time-history analyses indicated that the incorporation of the vertical component of a ground motion into analyses greatly influences the vertical deflections of a structure and the overturning moments at its base. The lateral deflections, the angles of rotation and the base shear forces were influenced to a lesser extent. Considering the key indicators of vertical deflection and overturning moments determined from the linear time-history analysis, the non-linear analyses revealed that the changes in the forces and deformations of the structure with the inclusion of the vertical ground motion are resisted by the shear-walls. The performances and damage states of the beams were not affected by the vertical ground motion. The vertical ground motion component of earthquakes is markedly concluded to be considered for design and damage estimation of the vertical load-bearing elements of the shear-walls and columns.

• The KIPS Transactions:PartA
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• v.12A no.6 s.96
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• pp.485-492
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• 2005

Currently workflows in business processes and distributed computing environments have provided service automation by connecting many tasks with rules and/or orderings. The services in ubiquitous computing environments have to automatically provide users with adaptive services according to dynamically changing contort information, which is obtained from both the users and their environment. To adapt these workflows to ubiquitous computing, we must specify the situation information on the transition conditions. In this paper, we propose uWDL, Ubiquitous Workflow Description Language, based on Web Services to use the situation information on the transition constraints of workflow's services. uWDL can select adaptive services according to contexts, profiles, and events information, which are situation information. Furthermore, we verified the execution of a scenario document described with uWDL using the parser and the context handler for uWDL. The scenario developers can use the uWDL scenario editor for a design of scenarios, and they can easily specify the transition condition of the services according the situation information of ubiquitous environments using the uWDL.

• Journal of Satellite, Information and Communications
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• v.6 no.2
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• pp.51-59
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• 2011

To support seamless IPTV services in IP-based wireless network, delay or interruption time must be minimized because noticeable interruption will make IPTV service users unhappy. A number of protocols have been proposed for solving mobility problem. However effective seamless handover mechanism to support mobile IPTV services yet to be solved. Mobile WiMAX offers a wireless solution in the access networks that can support IPTV services. Goal of this paper is to identify some reasons of delay time during handover process in an IPv6 capable Mobile WiMAX and to perform handover delay of some optimization scenarios given by existing standardization and proposed improvement.