• Smart Structures and Systems
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• v.6 no.5_6
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• pp.481-504
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• 2010

Wireless smart sensor networks (WSSNs) have been proposed by a number of researchers to evaluate the current condition of civil infrastructure, offering improved understanding of dynamic response through dense instrumentation. As focus moves from laboratory testing to full-scale implementation, the need for multi-hop communication to address issues associated with the large size of civil infrastructure and their limited radio power has become apparent. Multi-hop communication protocols allow sensors to cooperate to reliably deliver data between nodes outside of direct communication range. However, application specific requirements, such as high sampling rates, vast amounts of data to be collected, precise internodal synchronization, and reliable communication, are quite challenging to achieve with generic multi-hop communication protocols. This paper proposes two complementary reliable multi-hop communication solutions for monitoring of civil infrastructure. In the first approach, termed herein General Purpose Multi-hop (GPMH), the wide variety of communication patterns involved in structural health monitoring, particularly in decentralized implementations, are acknowledged to develop a flexible and adaptable any-to-any communication protocol. In the second approach, termed herein Single-Sink Multi-hop (SSMH), an efficient many-to-one protocol utilizing all available RF channels is designed to minimize the time required to collect the large amounts of data generated by dense arrays of sensor nodes. Both protocols adopt the Ad-hoc On-demand Distance Vector (AODV) routing protocol, which provides any-to-any routing and multi-cast capability, and supports a broad range of communication patterns. The proposed implementations refine the routing metric by considering the stability of links, exclude functionality unnecessary in mostly-static WSSNs, and integrate a reliable communication layer with the AODV protocol. These customizations have resulted in robust realizations of multi-hop reliable communication that meet the demands of structural health monitoring.

• Journal of Aerospace System Engineering
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• v.15 no.5
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• pp.24-32
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• 2021

Personal Air Vehicle (PAV), Cargo UAS (Cargo UAS), and existing manned and unmanned aircraft are key vehicles for urban air mobility (UAM), and should demonstrate compatibility for the design of aircraft systems. The safety assessment required by for certification to ensure safety and reliability should be systematically performed throughout the entire cycle from the beginning of the aircraft development process. However, with the increasing complexity of safety critical aviation systems and the application of state-of-the-art systems, conventional experience-based and procedural-based safety evaluation methods make ir difficult to objectively assess safety requirements and system safety. Therefore, Model-Based Safety Assessment (MBSA) using modeling and simulation techniques is actively being studied at domestic and foreign countries to address these problems. In this paper, we propose a Model-Based Safety Evaluation framework utilizing modeling and simulation-based integrated flight simulators. Our case studies on the Traffic Collision Availability System (TCAS) and Wheel Brake System (WBS) confirmed that they are practical for future safety assessments.

• Journal of Aerospace System Engineering
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• v.15 no.5
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• pp.98-105
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• 2021

This study presented the results of the static load tests conducted to verify the structural robustness of the composite oxidant tank for a space launch vehicle. First, we introduced the test equipment used in the static load test of the composite oxidant tank, and then described the test requirements that the composite oxidant tank must satisfy. In addition, we presented a test set-up diagram consisting of the static load test fixture, hydraulic pressure, control equipment, and data acquisition equipment, and the load profile of the static load test of the composite oxidant tank consisting of shear, equivalent compression, bending, and combination tests. As a result of load control, we verified the reliability of this test by showing the errors between the input load and the feedback load in each channel according to the increase of the test load, and the feedback error between the channel A and channel B of load cell in each load actuator. As a result of the static load test, the load of the actuator was properly controlled within the allowable error range in each test, and we found that the test specimen did not cause damage or buckling that causes significant structural defects in the required load.

• The Journal of the Korea Contents Association
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• v.19 no.1
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• pp.404-412
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• 2019

The purpose of this study is to develop the usability evaluation contents based on the needs of different stakeholder's related to the usability of the product, and to derive the design direction and apply it as the evaluation standard by applying the product design based on the results. I created a stakeholder map for a fire detector product and identified stakeholders related to usability. Based on 3 factors(Physical, cognitive, emotional) of the usability evaluation, I conducted survey on the building users and the building managers who have different requirements. There are 12 directions (ease of installation, durability, maintainability, additional functionality, effectiveness, attractiveness, visibility, consistency of information, environmental harmony, consistency, Image suitability, reliability). Through weighted analysis of three usability evaluation factors, I found factors were ranked in the same order of importance, but they were different in importance figure. Based on the results of the survey, overall product usability aspects were improved but effectiveness and environmental coordination aspects needed to be improved.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.5
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• pp.542-549
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• 2019

Maritime accidents, such as the collision of a fishing boat in Incheon's Yeongheung Island, result in several casualties and property damage, even if they occur just once. To prevent such accidents, the Incheon Metropolitan Government is implementing safety management policies; further, they will provide ship collision warning services to prevent collisions on WAVE (Wireless Access in Vehicular Environment) communication-based ship safety operation pilot projects. However, to realize these objectives, a service standardization method is required that defines specific service types, configurations, and systems, which should be prepared based on user requirement analyses. In this study, a standardization method of WAVE communication-based collision warning service was developed by analyzing the requirements of the vessel operators subject to the services and related authorities. This will help improve the quality of service, ensuring professionalism and reliability through continuous improvement and efforts for standardization, as well as data derived from demonstration projects. Therefore, it is expected to help prevent maritime accidents to a considerable extent.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.2
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• pp.238-246
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• 2021

Collision of small vessels such as fishing boats cause great personal injury. Prior to this study, the collision prevention algorithm was developed to assess the collision risk and make the collision alarm. However, a service provided for safety, such as a collision warning, not only prevents risks, but also requires a certain degree of user satisfaction to function effectively. In this study, the collision prevention algorithm for small vessels was improved to be more practical, and the effects of the improvement were confirmed by applying the algorithm. A survey conducted on the users of the collision warning service confirmed the user requirements for improving the accuracy of the collision warning system and reducing the volume and number of alarms. Accordingly, the algorithm was improved for user satisfaction, and the actual vessel experiment was performed applying the improved algorithm in an actual maritime environment. As a result, the frequency of alarm occurrence decreased compared to former algorithm, but the alarm was relatively steadily generated in dangerous situations. It was analyzed that the accuracy and practicality of the collision alarm were improved. If the practicality and reliability of the improved algorithm are verified in the further study, it will be able to effectively contribute to the prevention of collisions of small vessels.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.5
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• pp.417-424
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• 2021

The S-band telemetry and telecommand formats for geostationary orbit satellites should have sufficient reliability, since they transmit massive satellite health data and receive the mission commands in the 36,000km of the geostationary orbit. Also, they have to efficiently manage the large quantity of satellite health data under the limited data transmission rate. Cheollian-2A and 2B satellites were developed by Korea Aerospace Research Institute and launched at 2018 and 2020, respectively. Their missions are to conduct continuously the mission of Cheollian-1, which was the first geostationary orbit satellite of Korea. Therefore, the fundamental S-band data format design for Cheollian-2A and 2B should meet the requirements of Cheollian-1. Meanwhile the latest remote data processing techniques for these newest geostationary orbit satellites should be implemented. In this paper, the advanced S-band space data formats and management methods are proposed for more efficient data transmission, reception and operation with the limited data rate of the geostationary orbit satellites. The implemented results in the flight software of Cheollian-2A and 2B are described in detail.

• The Journal of Bigdata
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• v.5 no.2
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• pp.241-255
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• 2020

In Korea, utilizing and protecting the ocean from the sea on three sides can be considered the basis of national power. Recently, it has been distributed to IOT and 5G networks, and attempts to provide various information based on telecommunication infrastructure are continuing in the public and private sectors. In this study, an online survey was conducted with the aim of improving the services of marine information services (KOMC, safe and open seas) provided by the Government Agency for Oceanographic Research. Through an online survey, the survey was conducted on sites that are mainly used to survey people's need for marine information and to collect information. In addition, the survey was conducted on the UX, UI problems and improvements of KOMC, open and safe sea sites provided by the National Oceanographic Research Institute. The awareness and experience of marine information service by the Korea Oceanographic Research Institute were confirmed. Later, the previous steps of FGI also examined the usability of various users after allowing them to use the actual service. Here, the experience of collecting marine information from actual users was investigated, not just by looking at and evaluating the design of the service website and application. As a result, users presented a variety of opinions related to marine information services, including accessibility, reliability of information, providing media, and importance of information provided. The findings could be used as data to identify ocean-related data and ways to provide information required by users of various age groups and occupational groups.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.12
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• pp.417-425
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• 2020

Recently, the development of weapons systems in conjunction with the Fourth Industrial Revolution has increased the number of weapon systems that integrate individual commercial systems by actively incorporating the superior fields of private commercial technologies. In the case of such commercial product-based weapons systems, however, the development of ILS elements across all areas, such as technical manual, military field maintenance support equipment, interactive electronic technical manual (IETM), and Computer Based Training (CBT) development, and weapons system Reliability, Availability, Maintainability(RAM) target values, and logistics support analysis (LSA) was requested to expand the level of development by developers. The commercial product-based System Integration (SI) weapon system will be able to complete the comprehensive military balance for complementing and effective maintenance of the military and developers only when the ILS development, which is limited to the essential elements of the required group, Request For Proposal (RFP) and Post-Logistics Support (PLS) directions were applied in the framework of outsourcing maintenance implementation. As a result, by checking the operation status of current weapons systems, the logistics support of commercial product-based weapon systems selected outsourcing as the basic policy that is decided based on the development requirements, focusing on maintaining operation through a rational decision-making process, and presented a plan for applying the development plan to the RFP for the determined core elements and PLS.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.26 no.3
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• pp.185-200
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• 2021

The Marine Environment QA/QC management system has been operated since 2010 to secure the reliability of data and improve the analysis capabilities of measurement and analysis institutions. From 2010 to 2020, the cumulative number of measurement and analysis institutions participated in the QA/QC management system was 266. And the number of certificates issued by the ministry of oceans and fisheries is 182. A total of 32 reference materials for proficiency testing and interlaboratory comparisons have been developed. They were first developed focusing on items (Nutrients, COD) commonly analyzed in marine environmental measuring network, marine pollution impact surveys, sea area utilization impact assessment, deepsea water surveys, and information network on fishing ground environments. In addition, it is time to expand the filed of the QA/QC management system, such as seawater temperature, salinity, PCBs and PAHs in sediments, which are mainly analyzed in most monitoring programs. On-site assessment has been conducted for 162 laboratories according to ISO/IEC 17025 to evaluate their conformity of the quality management system and deficiency. In terms of management and technology requirements, about 4.2% of organizations showed insufficient division of duties among employees 8.7% of them revealed the lack of employee training. By test item, about 6.3% of organizations showed the lack of standard substance management and the state of the cleaning glassware was pointed out in about 5.4% of them. The QA/QC management system should be continuously supplemented by identifying the causes of nonconformities and area for improvement.