• ETRI Journal
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• v.37 no.6
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• pp.1065-1076
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• 2015

Network densification is regarded as the dominant driver for wireless evolution into the era of 5G. However, in this context, interference-limited dense small cell deployments are facing technical challenges in mobility management. The recently announced results from an LTE field test conducted in a dense urban area show a handover failure (HOF) rate of over 21%. A major cause of HOFs is the transmission failure of handover command (HO CMD) messages. In this paper, we propose two enhancements to HO performance in LTE networks - radio link failure-proactive HO, which helps with the reliable transmission of HO CMD messages while the user equipment is under a poor radio link condition, and Early Handover Preparation with Ping-Pong Avoidance (EHOPPPA) HO, which assures reliable transmission of HO CMD under a good radio link condition. We analyze the HO performance of EHOPPPA HO theoretically, and perform simulations to compare the performance of the proposed schemes with that of standard LTE HO. We show that they can decrease the HOF rate to nearly zero through an analysis, and based on the simulation results, by over 70%, without increasing the ping-pong probability.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.2
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• pp.242-247
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• 2010

This paper introduces a real-time load flow program for Korean energy management system(EMS). This study is concentrated on the following aspects. First, we propose the model of the real-time database and power system equipment for the real-time load flow. These models are extracted from the needs of load flow functions and are designed to the application common information. Second, several techniques are applied for the efficient convergence and computational speed. The generation/load mismatch is redistributed using generator participation factors which are separated to the reference bus. For the voltage control, the jacobian matrix is composed with the basic Y matrix elements and the voltage control elements. Through the optimally ordering, jacobian row and column for a column is changed. However all jacobian matrix entries have same order with the Y matrix. The proposed program is tested using the Korea Electric Power Corporation(KEPCO) system. Through the test, we verified that the proposed program can be effectively used to accomplish the Korean EMS system.

• International Journal of Railway
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• v.2 no.3
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• pp.99-106
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• 2009

Checks and tests before putting safety facilities into service as well as the results of these tests are essential, time consuming and may show great variations between each other. Economic constraints and the increasing complexity associated with the development of computerized tools tend to limit the capacity of the classic approval process (manual or automatic). A reduction of the validation cover rate could result in practice. This is not compatible with the French national plan to renew the interlocking systems of the national network. The method and the tool presented in this paper makes it possible to formally validate new computerized systems or evolutions of existing French interlocking systems with real-time functional interpreted Petri nets. The aim of our project is to provide SNCF with a method for the formal validation of French interlocking systems. A formal proof method by assertion, which is applicable to industrial automation equipment such as interlocking systems, and which covers equally the specification and its real software implementation, is presented in this paper. With the proposed method we completely verify that the system follows all safety properties at all times and does not show superfluous conditions: it replaces all the indoor checks (not the outdoor checks). The advantages expected are a significant reduction of testing time and of the related costs, an increase of the test coverage rate, an answer to the new demand of railway infrastructure maintenance engineering to modify and validate computerized interlocking systems. Formal methods mastery by infrastructure engineers are surely a key to prove that more safety is not necessarily more expensive.

• International Journal of Internet, Broadcasting and Communication
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• v.11 no.1
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• pp.27-38
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• 2019

Sensors collect information for Internet of Things (IoT)-based services. However, indoor construction sites have a poor communication environment and many interfering elements that make it difficult to collect sensor information. In this study, a network was constructed between a Bluetooth Low Energy (BLE)-based IoT device based on a serverless IoT framework and a router. This experimental environment was applied to large- and small-scale indoor construction sites. Experiments were performed to test the communication performance of BLE-based IoT devices and routers at indoor construction sites. An analysis of the received signal strength indication (RSSI) graph patterns collected from the communication between the BLE-based IoT devices and routers for different testbed site situation revealed areas with good communication performance and poor communication performance due to interfering factors. The results confirmed that structural components of the building as well as the materials, equipment, and temporary facilities used in indoor construction interfere with the communication performance. Construction project managers will require improved technical knowledge of IoT, such as optimizing the router placement and matching communication between the router and workers, to improve the communication performance for large-scale indoor construction.

• Journal of Korea Multimedia Society
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• v.24 no.2
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• pp.267-273
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• 2021

Recently, the small-size mobile robots with remote-control are rapidly growth which market of mobile is increased in the world. Especially, the smart-phones are widely used for interface device in the small size of a mobile robot. The research goal is control system design which is applied to miniaturization of a mobile robot using smart-phone and it can be confirmed performance for designed system. Meanwhile, the fabrication of mini-mobile robot can also be remote-control operation through the WIFI performance of a smart-phone. The smart-phone is used to remote-control for robot operation which control data transmit to robot via the WIFI network. To drive the robot, we can observe by the smart-phone screen and it can easily adjust the robot drive condition and direction by smart-phone button. Consequentially, there was no malfunction and images were printed out well. However, in drive, because of blind spot, robot was bumped into obstacle. Therefore, the additional test is necessary to sensor for blind spot which sensor can be equipment to mobile robot. In addition, the experiment with robot object recognition is needed.

• Geomechanics and Engineering
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• v.37 no.3
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• pp.253-262
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• 2024

Dynamic properties are pivotal in soil analysis, yet their experimental determination is hampered by complex methodologies and the need for costly equipment. This study aims to predict dynamic soil properties using static properties that are relatively easier to obtain, employing machine learning techniques. The static properties considered include soil cohesion, friction angle, water content, specific gravity, and compressional strength. In contrast, the dynamic properties of interest are the velocities of compressional and shear waves. Data for this study are sourced from 26 boreholes, as detailed in a geotechnical investigation report database, comprising a total of 130 data points. An importance analysis, grounded in the random forest algorithm, is conducted to evaluate the significance of each dynamic property. This analysis informs the prediction of dynamic properties, prioritizing those static properties identified as most influential. The efficacy of these predictions is quantified using the coefficient of determination, which indicated exceptionally high reliability, with values reaching 0.99 in both training and testing phases when all input properties are considered. The conventional method is used for predicting dynamic properties through Standard Penetration Test (SPT) and compared the outcomes with this technique. The error ratio has decreased by approximately 0.95, thereby validating its reliability. This research marks a significant advancement in the indirect estimation of the relationship between static and dynamic soil properties through the application of machine learning techniques.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.6
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• pp.1313-1319
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• 2011

VoIP service by taking advantage of the current PSTN network and internet over the existing telephone network at an affordable price allows you to make voice calls to the service is being expanded. However, the security of public must be maintained for security vulnerabilities in Smart Phone VoIP case problems arise, and is likely to be attacked by hackers. In this paper, the Internet, using wired and Smart Phone VoIP services may occur during analysis of the type of incident and vulnerability analysis, the eavesdropping should conduct an attack. Smart Phone VoIP with institutional administration to analyze the vulnerability OmniPeek, AirPcap the equipment is installed in a lab environment to conduct eavesdropping attack. Packet according to the analysis and eavesdropping attacks, IP confirmed that the incident as an attack by the eavesdropping as to become the test proves. In this paper, as well as Smart Phone VoIP users, the current administration and the introduction of Smart Phone service and VoIP service as a basis for enhanced security will be provided.

• Progress in Medical Physics
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• v.28 no.4
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• pp.197-206
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• 2017

We develop guidelines for the quality assurance of radiation treatment planning systems (TPS) by comparing and reviewing recommendations from major countries and organizations, as well as by analyzing the AAPM, ESTRO, and IAEA TPS quality assurance guidelines. We establish quality assurance items for acceptance testing, commissioning, periodic testing, system management, and security, and propose methods to perform each item within acceptable standards. Acceptance includes tests of hardware and network environments, data transmission, software, and benchmarking as specified by the system supplier, and apply the IAEA classification criteria. Commissioning includes dosimetric and non-dosimetric items for assessing TPS performance by applying the AAPM classification criteria and the latest technical items from the IAEA. Periodic quality assurance tests include daily, weekly, monthly, yearly, and occasional items by applying the AAPM classification criteria. System management and security items include the state and network connectivity of TPS, periodic data backup, and data access security. The guidelines for TPS quality assurance proposed in this study will help to improve the safety and quality of radiotherapy by preventing incidents related to radiotherapy.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.41
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• pp.29.1-29.10
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• 2019

Background: Reduction in postoperative complications is of vital considerations in impacted third molar teeth surgery. The aim of this study was to compare postoperative complications of impacted third molar surgeries for bone removal using laser, piezoelectric equipment, and conventional rotary instruments. Methods: To address the research purpose, the investigator designed the prospective double-blind clinical trial study. The sample size was determined 20 (40 teeth) by sampling formula in any kind of operation. The data of patients were obtained in the different periods in terms of pain, trismus, swelling, ecchymosis, and patient's satisfaction and then analyzed using SPSS 20 software via paired t test and Wilcoxon and McNemar's tests. Results: The pain immediately after surgery and 2 days and 7 days after surgery was higher in the laser group. The swelling immediately after surgery was more in the laser group but not significant. The amount of mouth opening immediately after surgery and 2 days and 7 days after surgery was significantly lower in the laser group than in the piezosurgery group. The total duration of surgery and duration of osteotomy were significantly longer in the laser group. The patient's satisfaction from surgery with piezosurgery was more than that with laser, but this difference was not significant. Conclusion: Due to the rising demand for impacted wisdom tooth surgery, the present study suggests that hard tissue laser surgery and piezosurgery can clear the future of impacted molar surgery, and these approaches are more efficient in reducing postoperative complications compared to the conventional surgeries.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.13 no.6
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• pp.523-529
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• 2020

Power distribution management system is essential for the efficient management and operation of power distribution networks. The power distribution system is a system that manages the distribution network based on IT, and has been evolving along with the development of the power industry. The current power distribution system is designed to operate at a relatively low network transmission speed based on the independent operation of the main equipment. However, due to distributed resources such as photovoltaic or energy storage devices, which are rapidly increasing in popularity in recent years, the operation of future distribution environments is becoming more complex, and various information needs to be collected in real time. In this study, the requirements of the next-generation power distribution system were derived to overcome the limitations of the existing power distribution system, and based on this, the communication network system and performance requirements for the distribution system were defined. In order to verify the performance of the designed system, a software-based terminal device simulator was developed because it takes excessive time and cost to introduce a large-scale system such as a power distribution system. Using the simulator, a test environment similar to the actual operation was established, and the number of terminal devices was increased up to 1,000. The proposed system was shown to satisfy the requirements to support the functions of the next-generation power distribution system, recording less than 10 % of the communication network bandwidth.