• Smart Structures and Systems
• /
• v.13 no.4
• /
• pp.587-614
• /
• 2014

In recent years the interest in online monitoring of lightweight structures with ultrasonic guided waves is steadily growing. Especially the aircraft industry is a driving force in the development of structural health monitoring (SHM) systems. In order to optimally design SHM systems powerful and efficient numerical simulation tools to predict the behaviour of ultrasonic elastic waves in thin-walled structures are required. It has been shown that in real industrial applications, such as airplane wings or fuselages, conventional linear and quadratic pure displacement finite elements commonly used to model ultrasonic elastic waves quickly reach their limits. The required mesh density, to obtain good quality solutions, results in enormous computational costs when solving the wave propagation problem in the time domain. To resolve this problem different possibilities are available. Analytical methods and higher order finite element method approaches (HO-FEM), like p-FEM, spectral elements, spectral analysis and isogeometric analysis, are among them. Although analytical approaches offer fast and accurate results, they are limited to rather simple geometries. On the other hand, the application of higher order finite element schemes is a computationally demanding task. The drawbacks of both methods can be circumvented if regions of complex geometry are modelled using a HO-FEM approach while the response of the remaining structure is computed utilizing an analytical approach. The objective of the paper is to present an efficient method to couple different HO-FEM schemes with an analytical description of an undisturbed region. Using this hybrid formulation the numerical effort can be drastically reduced. The functionality of the proposed scheme is demonstrated by studying the propagation of ultrasonic guided waves in plates, excited by a piezoelectric patch actuator. The actuator is modelled utilizing higher order coupled field finite elements, whereas the homogenous, isotropic plate is described analytically. The results of this "semi-analytical" approach highlight the opportunities to reduce the numerical effort if closed-form solutions are partially available.

• THE INTERNATIONAL COMMERCE & LAW REVIEW
• /
• v.13
• /
• pp.69-81
• /
• 2000

Under the co-sponsorship of UNIDROIT and I.C.A.O., a preliminary draft Convention on International Interests in Mobile Equipment and a preliminary draft Protocol on Matters Specific to Aircraft Equipment has been prepared. The purpose of the Convention is to provide for the creation and effect of a new international interest in mobile equipment. The Convention's approach is quite novel in that it purports to create an international interest based upon the convention itself. The Convention is intended to be supplemented by Protocols, each of is intended to provide equipment-specific rules necessary to adapt the rules of the Convention to fit the special pattern of financing for different categories of equipment. To date, two sessions of governmental experts were held in Rome and Montreal. Korean delegations attended the two sessions. One of the members of the Korean delegation published a report on the first session. He expressed his objection to the so called self-help remedy contemplated by the current preliminary draft of the Convention which enables the holder of a security interest to repossess and dispose of the subject of the security interest by private sale rather than public auction on the occurrence of an event of default of the debtor. His view is based upon his understanding that under Korean law, the only remedy available to the holder of a security interest in mobile equipment, such as an airplane, is to apply to the competent court for a public auction. In my view, his understanding is not quite correct and is inconsistent with the current practice in Korea. Under Korean law, the parties' agreement for private sale is in principle valid unless there is an interested party who has acquired a security interest after the creation of the prior security interest or a creditor who has caused the subject of the security interest to be attached by a competent court. In this article, I discuss the current Korean law and practice relating to the enforcement of security interests by private sale in more detail.

• Journal of Advanced Navigation Technology
• /
• v.19 no.1
• /
• pp.15-21
• /
• 2015

WA-DGNSS is a system to service for users using a satellite which received correction data from ground station that calculates the relative errors of the tracked GNSS signals and sends to a satellite. Users are guaranteed the reliability of the GNSS signal and the accuracy of positioning. ICAO recommends the application of WA-DGNSS for the airplane taking off and landing process. In this paper, we suggests methods to verify of the pre-developed WA-DGNSS reference software constituting modules and an integration test process refer to the RTCA DO-278 which is a document for the development process of an aeronautics software. Also, we statistically verified the reference software test through our methods. And then, we confirmed to performance the function of the reference software properly.

• Journal of Advanced Navigation Technology
• /
• v.24 no.1
• /
• pp.28-36
• /
• 2020

Korea augmentation satellite system (KASS) is the Korean satellite based augmentation system (SBAS) developed by ministry of land, infrastructure, and transport (MOLIT) since 2014. Since KASS is the safety critical system that can affect to the safety of airplane, the software of KASS is developed according to the DO178B software level induced from safety analysis. In case of KASS control station (KCS), most of the software of KCS get assigned software level E in DO178B. In that case, ECSS-Q-ST-80C category D is assigned as a software product assurance standard. In this paper, the software related standard ECSS-E-ST-40C, ECSS-Q-HB-80-04A are analyzed to satisfy ECSS-Q-ST-80C and as a result the software product assurance activities regarding software life cycle and the software quality model, metric is proposed for the product assurance of the KCS software.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2007.10a
• /
• pp.589-592
• /
• 2007

Ubiquitous environment means the environment in which users can access the Internet at anytime and anywhere. Network mobility support is needed for seamless Internet service in ubiquitous environment. When users try to access the Internet in public transportation such as bus, train, airplane, to support network mobility by composing several sub-networks is more efficient than to support host mobility. IETF established 'Network Mobility(NEMO)' working group to research and develop network mobility technology. In this paper, we investigate the concept of network mobility, trends of research in NEMO and developed technology on the basis of 'Network Mobility Basic Support Protocol' standardized by IETF.

• The KIPS Transactions:PartD
• /
• v.10D no.1
• /
• pp.125-132
• /
• 2003

The Internet reservation service is one of the most utilized internet services, specifically the agent efficiently supports this reservation services. The Agent will replace the repetitious reservation process and selectively offering the most proper service information. In this study, the user assisting agent system that can enable people to make reservation of public transportations through the internet is designed and implemented. This system consists of multiple agents that are Interface agent, 4ask agents and filtering agent. The interface agent is an arbitrator of this system that analyzes user's demand and integrate agent's result. And it has user-adaptive capability using case-based reasoning. There are three task agents if this system, it executes information gathering and information-change monitoring of each. Filtering agent extracts information only about reservation status in gathered information. Finally, this system is to offer integrated information of the reservation status about train and airplane and execute the simple-repetitious works for the reservation instead of user by agents.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.35 no.4
• /
• pp.57-70
• /
• 2007

As a basic element of Jeju landscape, Oreum offers a beautiful and aesthetic view. Considering topographical and geological research achievements, however, an effort to discover implicit value in terms of landscape characteristics and value has been ignored. This paper has investigated the characteristics and value of landscape by Oreum focusing on Jeju landscape characteristics and eco-touristic value and discussed a scheme to maximize the values. Under a theme of 'Sustainable Development' of the RIO Declaration, tour industry has recently changed its focus from eco-tourism to gee-tourism. Fortunately, Jeju Oreum has very distinctive and unique landscape with depressed crater at a crest. Nevertheless, it's very difficult to see a true aspect of Oreum from the street or over the car window. Therefore, it's urgent to begin a research on how to make advantage of and preserve Oreum landscape in order to maximize its landscape values and improve its potential as a tourist attraction. Through diverse programs such as sky leisure sports(ex: light airplane and helicopter riding, paragliding), sky watching, and mountain hiking, in particular, a possibility that Oreum can succeed as LBD(Learning by Doing)-based tour program with volcanic features needs to be examined. Besides, it's also a good idea to develop Oreum tour program or Oreum Museum as an alternative plan. Above all, however, it's most urgent to protect the existing Oreum and restore ecological and landscape beauty of Oreum through proper land use.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.2
• /
• pp.642-648
• /
• 2016

As 3D solid modeling prevails, a range of applications have become possible and intensive research on the integration of CAD/CAM has been conducted. As a consequence, methods to recognize the machining features from CAD models have been developed. On the other hand, generating a machining sequence using the machining features is still a problem due to a combinatorial problem with a large number of machining features. This paper proposes a new method that utilizes the precedence constraints through which the number of the combinations is reduced drastically. This method can automatically generate machining sequences requiring the lowest amount of machining time. An airplane part was used to test the usefulness of the proposed method.

• Journal of the Institute of Convergence Signal Processing
• /
• v.12 no.4
• /
• pp.303-308
• /
• 2011

Vehicle black boxes that have similar functions as airplane black boxes are currently being used due to the loss of many lives and properties arising from vehicle accidents. Both black-box products and Event Data Recorder(EDR) systems are currently available in the market. Most of the existing in-vehicle black boxes, however, record only external videos and images and cannot show the vehicle's driving status, whereas EDR products record only the driving status and not external videos. To address the problem of black boxes that can record only videos and images and that of EDR systems that can record only driving data, an integrated vehicle state and video recording system that uses MOST(Media-oriented System Transport) and OBD-II(Onboard Diagnostics II) and CAM (camera) and GPS (global positioning system).

• Journal of the Korean Society of Propulsion Engineers
• /
• v.20 no.2
• /
• pp.11-17
• /
• 2016

Powder metallurgy nickel based superalloy has been used in a high temperature part of turbine engine for airplane. The fatigue crack growth behavior was investigated using CT specimens for the materials at room temperature(R.T.), $600^{\circ}C$ and $700^{\circ}C$. The direct current potential drop(DCPD) method suggested by ASTM E647 was used to measure the crack length during fatigue crack growth at various stress ratios. The fatigue crack growth rate at R=0.5 was faster than that at R=0.1 for all temperature conditions and increased with the increase of stress ratio and temperature. Fractography was conducted for analysis of fracture mechanism.