• The Journal of the Korea institute of electronic communication sciences
• /
• v.5 no.6
• /
• pp.672-677
• /
• 2010

Recently, the efficient management system for large-scale sensor data has been required due to the increasing deployment of large-scale sensor networks. In this paper, we propose a cloud-based sensor data management system with low cast, high scalability, and efficiency. Sensor data in sensor networks are transmitted to the cloud through a cloud-gateway. At this point, outlier detection and event processing is performed. Transmitted sensor data are stored in the Hadoop HBase, distributed column-oriented database, and processed in parallel by query processing module designed as the MapReduce model. The proposed system can be work with the application of a variety of platforms, because processed results are provided through REST-based web service.

• The KIPS Transactions:PartC
• /
• v.9C no.3
• /
• pp.351-358
• /
• 2002

Recently, personal business styles have been rapidly changed into e-business due to the rapid progress and deployment of Internet. As a result of the change, new and safe ways of payment such as electronic wallet, electronic money and electronic check have been developed and introduced. In this paper a secure and user-friendly payment method is addressed. One of most important reasons why newly developed safe payment methods are not widely used in e-business is lack of convenience for the users. On the other hand credit card based payment, which is traditional one, is the most prevailing due to the user-friendliness. However this payment also has some problem in sense of security. In this paper, we design and implement a secure credit card-based payment system using one-time credit information. The main features are "payment information must be new", "can use the old credit system", and "do not require client software".

• Journal of the Korean Operations Research and Management Science Society
• /
• v.23 no.3
• /
• pp.135-151
• /
• 1998

The demand of large capacity in coming cellular systems makes inevitable the deployment of small cells, rendering more frequent handoff occurrences of calls than in the conventional system. The key issue is then how effectively to reduce the chance of unsuccessful handoffs, since the handoff failure is less desirable than that of a new call attempt. In this study, we consider the control policies which give priority to handoff calls by limiting channel assignment for the originating new calls, and allow queueing the new calls which are rejected at their first attempts. On this system. we propose the problem of finding an optimal call control strategy which optimizes the objective function value, while satisfying the requirements on the handoff/new call blocking probabilities and the new call delay. The objective function takes the most general form to include such well-known performance measures as the weighted average carried traffic and the handoff call blocking probability. The problem is formulated into two different linear programming (LP) models. One is based on the direct employment of steady state equations, and the other uses the theory of semi-Markov decision process. Two LP formulations are competitive each other, having its own strength in the numbers of variables and constraints. Extensive experiments are also conducted to show which call control strategy is optimal under various system environments having different objective functions and traffic patterns.

• Korean Management Science Review
• /
• v.23 no.1
• /
• pp.21-41
• /
• 2006

Given the growing deployment of mobile offices, we need to understand the fectors which affect their successful use and implementation. We in this paper present a parsimonious model which integrates the IS success model and the TAM. The main feature of the model is that it allows one to explore the role of mobility of mobile office systems in determining the level of system usage and dependence. Although the mobility is the key property of any mobile system, there is little research effort exerted to understand how mobility affects the traditional IS factors such as perceived ease of use and usefulness. In addition to the system usage, this model also uses dependence as the dependent variable. This is expected to provide richer understanding of the study context. We collected survey data from 1,614 field service workers of a major domestic electronic company. They use PDAs to retrieve information regarding the specifics of the customer service requests and to report what has been done for each service job. The results from SEM analysis show that mobility improves the perceived ease of use which then leads the field service workers to depend more on the PDA systems. Interestingly enough, however, the workers' satisfaction does not cause more frequent use of the system.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.5A
• /
• pp.517-525
• /
• 2008

In this paper, we cary out system level simulations to investigate the effect of cell shape(i.e., different base station displacements in the two directions defined by the street grid) on minimizing transmitter power, interference power, and blocking probability for CDMA system in urban microcellular environments. In urban microcell, path loss to the base station depends on the orientation of the street where the mobile is located. Interference from mobile stations to the base station in the reference cell is considered up to second tier. The wrap around method is used to include the second tier interference with realistic computational complexity without reducing the accuracy of interference calculations. The investigation shows that the transmitter power, interference power, and blocking probability in a cell can be reduced by proper selection of the efficient cell shape.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.18 no.9
• /
• pp.2272-2279
• /
• 2014

Mobile applications are software systems running on handheld devices, such as smartphones, PDAs, tablets and so on. The market of mobile application has rapidly expanded in the past few years. In this paper, we present a novel approach to track smartphone application usage from a event logs on the mobile device and analyzed both on client system and usage analysis server. We implemented our client system on Android device based usage analytics platform. Based on the analysis server system, we obtained over 47,000 user base, and we get the user's app usage informations on realtime. In this paper, we describe a large scale deployment-based research for a smartphone usage patterns and usage information visualization techniques.

• Journal of Ship and Ocean Technology
• /
• v.8 no.3
• /
• pp.18-25
• /
• 2004

Sound reception system is required to detect the sound and the quadrantal direction of the other ship's horn sound, to overcome the effects of enclosed wall for navigation space, functioning as a sound barrier. However, the realized systems can only provide quadrantal information of the other ship. This paper presents a new arrangement of microphones, having geometrically symmetric deployment with the same distances between sensors and the same angles between adjacent sensors with respect to the geometrical center. The sound pressures received at microphones are transformed into the related envelope signals by applying Hilbert transform. The time delays between microphones are estimated by the correlation functions between the derived envelope signals. This envelope base processing mitigates the noises related to the reflection by ship and sea surface. Then, the directional information is easily defined by using the estimated time delays. The suggested method is verified by the generated signals using boundary element method for a small ship model with sea surface wave. The estimated direction is quite similar to the true one and therefore the proposed approach can be used as an efficient sound reception system.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.12 no.12
• /
• pp.6098-6122
• /
• 2018

Cache-based side-channel attacks have achieved more attention along with the development of cloud computing technologies. However, current host-based mitigation methods either provide bad compatibility with current cloud infrastructure, or turn out too application-specific. Besides, they are defending blindly without any knowledge of on-going attacks. In this work, we present CacheSCDefender, a framework that provides a (Virtual Machine Monitor) VMM-based comprehensive defense framework against all levels of cache attacks. In designing CacheSCDefender, we make three key contributions: (1) an attack-aware framework combining our novel dynamic remapping and traditional cache cleansing, which provides a comprehensive defense against all three cases of cache attacks that we identify in this paper; (2) a new defense method called dynamic remapping which is a developed version of random permutation and is able to deal with two cases of cache attacks; (3) formalization and quantification of security improvement and performance overhead of our defense, which can be applicable to other defense methods. We show that CacheSCDefender is practical for deployment in normal virtualized environment, while providing favorable security guarantee for virtual machines.

• ETRI Journal
• /
• v.42 no.6
• /
• pp.837-845
• /
• 2020

The objective of this study was to implement an in vitro exposure system for 28 GHz to investigate the biological effects of fifth-generation (5G) communication. A signal source of 28 GHz for 5G millimeter-wave (MMW) deployment was developed, followed by a variable attenuator for antenna input power control. A power amplifier was also customized to ensure a maximum output power of 10 W for high-power 28-GHz exposure. A 3-dB uniformity over the 80 mm × 80 mm area that corresponds to four Petri dishes of three-dimensional cell cultures can be obtained using a customized choke-ring-type antenna. An infrared camera is employed for temperature regulation during exposure by adjusting the airflow cooling rate via real-time feedback to the incubator. The reported measurement results confirm that the input power control, uniformity, and temperature regulation for 28-GHz exposure were successfully accomplished, indicating the possibility of a wide application of the implemented in vitro exposure system in the fields of various MMW dose-response studies.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.45 no.2
• /
• pp.1-11
• /
• 2022

In this paper, we investigate the requirements of QPA(Quality Process Audit), which is a process quality audit system for secondary defense contractors, compared with those of DQMS(Defense Quality Management System). And evaluate whether the deployment of QPA meets the DQMS certification requirements through the case example of Company H. The evaluation items of QPA are composed of five categories such as Material Management, Incoming Inspection, Manufacturing Process, Product Evaluation, and Packaging Management. The QPA requirements are mainly related to the chapter 7(support) and chapter 8(operation) of DQMS standards. In this view point, QPA can be expected as an effective audit for suppliers preparing for DQMS certification. In the case example, we evaluate the results and effects of improvement due to QPA and compare it with the case of DQMS. QPA can be used as appropriate quality management standards of secondary and tertiary defense contractors and can provide the basis guidelines for the preparation of implementation steps in DQMS certification.