• The Journal of the Korea institute of electronic communication sciences
• /
• v.8 no.3
• /
• pp.487-498
• /
• 2013

A variety of location-based services applications, such as missing children search, emergency rescue requests and so on that requiring high-precision location information are increasing. Precision of GPS that can be used in most systems, however, is still low. In this paper, we design and propose a low cost differential global positioning system(DGPS) based on Web services using object-oriented modeling technique which can offer useable location service, variety device and safe service in wireless environment. The proposed system is designed with UML based on object-oriented modeling to maximize system recyclability and system scalability. In addition, we would like to improve the precision of the GPS in accordance with mobile station location when build low cost mobile station, location differential framework and server. We implement a communication interface based on web-service which is available in the form of a variety of services and can offer stable according to mobile environments. Finally, as performance evaluation results, we can obtain precision location within 1 ~ 2m through proposed system and 88.5% probability of less than 2m.

• Spatial Information Research
• /
• v.11 no.1
• /
• pp.41-60
• /
• 2003

It is noted that the paper mapping system for University Building Facility has many limitations in terms of data maintenance, real-time GIS data acquisition, and economic efficiency. The aim of this research was to evaluate an operational potential of an on site real-time mobile GIS technique to resolve the problem faced in the university. The idea is based upon the recent trends in the field of 'Telecommunication and Information Technology' that uses a PDA (personal Digital Assistants), wireless network computing, mobile computing, etc. A real time mobile GIS approach has been adopted, in which a PDA is linked to a wireless internet and field workers record data on the computer at the site and analyse data on site. While there should be a considerable number and variety of factors associated with real-time mobile GIS quality, this research focuses on three criteria that are identified as fundamental to customer requirements; (1) data quarry (2) spatial analysis (3) real-time GIS database building. 'Art--empirical study for a case study facility has been conducted to confirm the validity for the system. The system has been checked experimentally, enabled the field users to quarry the data required simply and execute spatial analysis (buffer, overlay etc.,) accommodating versatile alternatives on the site. Detailed visual maps can be generated over large areas quickly and easily. The PDA interface, in particular, were ideally suited for field users to interactively displaying positional information with attribute data. This system has shown to be quite convenient to maintaining a highly reliable database since it could playa crucial role in documenting at real-time basis temporal and spatial changes occurred in the facilities. It is anticipated that this research output will greatly serve to introduce the reliable and cost-effective facility mapping system in the university by overcoming serious constraints suffered from the past non-real time mobile GIS approach.

• Spatial Information Research
• /
• v.19 no.4
• /
• pp.11-20
• /
• 2011

In accordance with low carbon and green growth paradigm, a subway is one of major public transit systems for resolving traffic congestion and decreasing traffic accidents. In addition, as subway networks expand, passengers' travel pattern in the subway network change and consequently affect the urban structure. Generally, new subway route has been planned and developed, mainly considering a travel demand forecast. However, it is desired to conduct an empirical analysis on the forecast model regarding change of travel accessibility and passenger demand pattern according to new subway line. Therefore, in this paper, an alternative method, developed based upon a spatial syntax model, is proposed for evaluating new subway route in terms of passenger's mobility and network accessibility. In a case study, we constructed subway network data, mainly targeting the no 9 subway line opened in 2009. With an axial-map analysis, we calculated spatial characteristics to describe topological movement interface. We then analyzed actual modal shift and change on demand of passengers through the number of subway passenger between subway stations and the number of passenger according to comparative bus line from Smart Card to validate suggested methods. Results show that the proposed method provides quantitative means of visualizing passenger flow in subway route planning and of analyzing the time-space characteristics of network. Also, it is expected that the proposed method can be utilized for predicting a passengers' pattern and its impact on public transportation.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.24 no.6
• /
• pp.601-608
• /
• 2011

In order to design floating structures, it should be required to evaluate hydrodynamic motions and structural behavior under the wave loadings. Then, structural behavior of floating structures should be evaluated including the effects of wave-induced hydraulic pressure subjected to floating structures. However, there has been a problem to exactly evaluate structural behavior of floating structures since it was difficult to directly connect wave-induced hydraulic pressure resulting from hydrodynamic analysis with structural analysis model. In this study, in order to exactly evaluate structural behavior of floating structures under the wave loading, integrated analysis of hydrodynamic motion and structural behavior was carried out to the large-scaled floating structure. The wave-induced hydraulic pressure resulting from hydrodynamic analysis AQWA were directly mapped to structural analysis model ANSYS bia Workbench interface of ANSYS Inc.. As the results of this study, it was found that the integrated analysis of this study evaluate exactly structural behavior of floating structures under the wave loadings since this method can directly reflect wave-induced hydraulic pressure resulting from hydrodynamic analysis to structural analysis model. Also, as the results of structural behavior evaluation, it was found that the tensile stress on the top slab was maximized at the wave direction of $0^{\circ}$, and tensile stress on the bottom slab was maximized at the wave direction of $45^{\circ}$, respectively.

• Composites Research
• /
• v.30 no.2
• /
• pp.84-93
• /
• 2017

This study investigates thermal and mechanical characterization of environmental barrier coating on the $SiC_f-SiC$ composites. The spherical environmental barrier coating (EBC) powders are prepared using a spray drying process for flowing easily during coating process. The powders consisting of mullite and 12 wt% of Ytterbium silicate are air plasma sprayed on the Si bondcoat on the LSI SiC fiber reinforced SiC composite substrate for protecting the composites from oxidation and water vapor reaction. We vary the process parameter of spray distance during air plasma spray of powders, 100, 120 and 140 mm. After that, we performed the thermal durability tests by thermal annealing test at $1100^{\circ}C$ for 100hr and thermal shock test from $1200^{\circ}C$ for 3000 cycles. As a result, the interface delamination of EBC never occur during thermal durability tests while stable cracks are prominent on the coating layer. The crack density and crack length depend on the spray distance during coating. The post indentation test indicates thermal tests influence on the indentation load-displacement mechanical behavior.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.8 no.5
• /
• pp.119-128
• /
• 2008

Sewer rehabilitation is performed to improve the problem for urban drainage sewer system recently. However the data for the sewer system is not stored enough so that the sewer system is difficult to be managed systematically. In this study, a maintenance management system for urban drainage system is developed to store the data efficiently and manage the system systematically. In the developed system, a hydraulic and hydrologic analysis module is included to test the carrying capacity of a sewer pipe and estimate the amount of combined sewer overflows. The I/I and superannuation evaluation module is included in this system. The module distribute the total inflow/infiltration observed at the several sampling points in a drainage area to the individual pipes of the entire sewer system. Then the superannuation of a sewer pipe is evaluated according to the amount of I/I of the pipe. And in the developed system, the optimal rehabilitation priority module is included to determine the optimal priority and support the decision making for the sewer rehabilitation. The maintenance management system which is developed in this study is constructed by the association with the developed modules and the system is formed as graphical user interface system.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.21 no.6
• /
• pp.618-629
• /
• 2001

This paper presents a result of failure analysis and reliability evaluation for high voltage ceramic capacitors. The failure modes and failure mechanisms were studied in two ways in order to estimate component life and failure rate. The causes of failure mechanisms for zero resistance phenomena under withstanding voltage test in high voltage ceramic capacitors molded by epoxy resin were studied by establishing an effective root cause failure analysis. Particular emphasis was placed on breakdown phenomena at the ceramic-epoxy interface. The validity of the results in this study was confirmed by the results of accelerated testing. Thermal cycling test for high voltage ceramic capacitor mounted on a magnetron were implemented. Delamination between ceramic and epoxy, which might cause electrical short in underlying circuitry, can occur during curing or thermal cycle. The results can be conveniently used to quickly identify defective lots, determine $B_{10}$ life estimation each lot at the level of inspection, and detect major changes in the vendors processes. Also, the condition for dielectric breakdown was investigated for the estimation of failure rate with load-strength interference model.

• Journal of the Korean Ceramic Society
• /
• v.41 no.8
• /
• pp.599-604
• /
• 2004

The LTCCs (Low-Temperature Co-fired Ceramics) are very important for electronic industry to build smaller RF modules and to fulfill the necessity for miniaturization of devices in wireless communication industry. The dielectric materials with sintering temperature $T_{sint}$＜90$0^{\circ}C$ are required. In this study, BaO-N $d_2$ $O_3$-Ti $O_2$ (BNT ： 20∼40 wt％) for ceramic materials and L $a_2$ $O_3$- $B_2$ $O_3$-Ti $O_2$ (LBT ： 80∼60 wt％) for crystallizable glasses were used. The glass/ceramic composites were investigated for sintering behavior, phase evaluation, densities, interface reaction and microwave dielectric properties. It was found that the addition LBT glass frist significantly lowered the sintering temperature to below 90$0^{\circ}C$ and the densification with increasing addition LBT glass frist developed rapidly which was meant to be namely 90％ of relative density. The sintered bodies ekhibited applicable dielectric properties, namely 15 for $\varepsilon$$_{r}$,, 10000 GHz for Q＊ $f_{0}$. The results suggest that the composites have good potential as a new candidate for LTCC materials.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.32 no.5A
• /
• pp.317-325
• /
• 2012

In this study, to evaluate the shrinkage behavior of ultra high performance fiber reinforced concrete (UHPFRC) under restrained condition, restrained shrinkage test was performed according to ring-test mostly used at home and abroad. Ring-test was performed with the various thicknesses and radii of inner steel ring to give different degree of restraint. Free shrinkage and tensile tests were carried out simultaneously to estimate the degree of restraint, stress relaxation, and shrinkage cracking potential. Test results indicated that the average steel strain and residual tensile stress were reduced as the thicker inner steel ring was used, whereas degree of restraint was increased. The steel strain, residual tensile stress and degree of restraint were hardly affected by the size of radius of inner ring. In the case of all ring specimens, shrinkage crack did not occur because the residual tensile stress was lower than the tensile strength. About 39~65% of the elastic shrinkage stress was relaxed by the sustained interface pressure, and the maximum relaxed stress was increased as the thicker inner ring was applied. Finally, the degree of restraint with age was predicted by performing non-linear regression analysis, and it was in good agreement with the test results.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.22 no.5
• /
• pp.91-101
• /
• 2014

In this study, we presented a timing verification method for a passenger car diesel engine management system (EMS) using measurement-based worst-case execution time (WCET) analysis. In order to cope with AUTOSAR-compliant software architecture, a development process model is proposed. In the process model, a runnable is regarded as a test unit and its temporal behavior (i.e. maximum observed execution time, MOET) is obtained along with on-target functionality evaluation results during online unit test. Furthermore, a cost-effective framework for online unit test is proposed. Because the runtime environment layer and the standard calibration environment are utilized to implement test interface, additional resource consumption of the target processor is minimized. Using the proposed development process model and unit test framework, the MOETs of 86 runnables for diesel EMS are obtained with 213 unit test cases. Using the obtained MOETs of runnables, the WCETs of tasks are estimated and the schedulability is evaluated. From the schedulability analysis results, the problems of the initially designed schedule table is recognized and it is fixed by redesigning of the runnable mapping and task offset. Through the various test scenarios, the proposed method is validated.