• Journal of Ocean Engineering and Technology
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• v.24 no.6
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• pp.76-80
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• 2010

Oil hydraulic piston pumps are being extensively used around the world, because of their simple design, light weight, effective cost, etc. An oil hydraulic pump is likely to have the serious problems of high leakage, friction, and low energy efficiency after a long period of use. In an oil hydraulic piston pump, the clearance between the valve block and piston plays an important role for volumetric and overall efficiency. In this study, the wear property of the SACM645 material with DLC coating used for a hydraulic piston pump was determined by experimentation with variable heat treatment. To investigate the effect according to the piston surface condition, five different types of specimens were prepared. The maximum tensile strengths of the QT and QT Nitration specimens had similar values of about 800 MPa, but the strains indicated a big difference. In a wear test, the wear characteristic of the DLC coating specimen was shown to be excellent. The QT, QT + IH, QT + Nitration, and matirx specimen showed similar wear characteristics. In the case of a dry condition without oil, the DLC coating specimen had good wear resistance, with no wear shown.

• Journal of Positioning, Navigation, and Timing
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• v.7 no.3
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• pp.155-163
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• 2018

This study examined methods to enhance navigation performance and reduce the divergence of navigation solutions that may occur in the event of global positioning system (GPS) failure by integrating the GPS/inertial navigation system (INS) with the three-dimensional (3D) magnetic vector measurements of a magnetometer. A magnetic heading aiding method that employs a magnetometer has been widely used to enhance the heading performance in low-cost GPS/INS navigation systems with insufficient observability. However, in the case of GPS failure, wrong heading information may further accelerate the divergence of the navigation solution. In this study, a method of integrating the 3D magnetic vector measurements of a magnetometer is proposed as a countermeasure for the case where the GPS fails. As the proposed method does not require attitude information for integration unlike the existing magnetic heading aiding method, it is applicable even in case of GPS failure. In addition, the existing magnetic heading aiding method utilizes only one-dimensional information in the heading direction, whereas the proposed method uses the two-dimensional attitude information of the magnetic vector, thus improving the observability of the system. To confirm the effect of the proposed method, simulation was performed for the normal operation and failure situation of GPS. The result confirmed that the proposed method improved the accuracy of the navigation solution and reduced the divergence speed of the navigation solution in the case of GPS failure, as compared with that of the existing method.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1174-1187
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• 2007

Monorail System has many advantages compared with other Urban Lightweight Transit Systems, such as the friendliness of the vehicle's appearance, slenderness of the bridge structures, it's low construction cost and short construction period. So, lots of city governments have reviewed or proposed the Monorail System as the attractive alternative system. And recently, Daegu Metropolitan City Government have chosen the Monorail System for the Urban Railroad Line 3. According to these trends on Urban Lightweight Transit Systems, this paper has introduced the outline of the planning and design of Monorail Bridges. At first, trends of overseas Monorail Bridges have been reviewed and the principal design criteria adopted in the basic design of the Urban Railroad Line 3 for Daegu have been introduced. And next, the methods of planning, design, fabrication of the guideway beams which are made of PSC Beam or Steel Beam have been explained. We hope this paper be helpful for the Engineers who are interested in the Monorail Bridges.

• Journal of Electrical Engineering and Technology
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• v.11 no.3
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• pp.609-617
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• 2016

Belt-driven Starter Generator (BSG) differs from other mild hybrid systems as the crankshaft of vehicle are not run off. Motor permits a low-cost method of adding mild hybrid capabilities such as start-stop, power assist, and mild levels of regenerative braking. Wound rotor synchronous motor (WRSM) could be adopted in BSG system for HEV e-Assisted application instead of the interior permanent magnet synchronous motor (IPMSM). In practice, adequate torque is indispensable for starter assist system, and energy conversion should be taken into account for the HEV or EV as well. Particularly, flux weakening control is possible to realize by adjusting both direct axis components of current and field current in WRSM. Accordingly, this paper present an off-line current acquisition algorithm that can reasonably combine the stator and field current to acquire the maximum torque, meanwhile the energy conversion is taken into consideration by losses. Besides, on account of inductance influence by non-uniform air gap around rotor, nonlinear inductances and armature flux linkage against current variation are proposed to guarantee the results closer to reality. A computer-aided method for proposed algorithm are present and results are given in form of the Look-up table (LUT). The experiment shows the validity of algorithm.

• Journal of Korean Library and Information Science Society
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• v.23
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• pp.1-27
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• 1995

The purpose of this study is twofold: to investigate into general characteristics of the networks in Korea as a new information technology and to discuss general directions of development of the use of the Internet. This study is designed to achieve the purpose by gathering and analysing data related to the use of Internet of librarians those who work in public libraries and research and development libraries and university libraries. The major conclusions made in this study is summarized as follows. (1) From this survey, received detailed response from 69 librarians, the majority (42) from research and development libraries. The majority (56) were from Library and Information Science subject area, half of them (37) hold advanced degrees. (2) Majority (40) have accessed Internet for one year or less, 9(17%) respondents for two years, 17(32%) spend every day Internet related activity. (3) 44.9% of the respondents taught themselves. 28.9% learned informally from a colleague. Formal training from a single one-hour class to more structured learning was available to 30.4%. (4) The most common reason respondents use the Internet are to access remote database searching(73.9%), to communicate with colleagues and friends and electronic mail(52.2%), to transfer files and data exchange(36.2%), to know the current research front(23.2%). They search OPACs for a variety of traditional task-related reasons(59.4%) and to see what other libraries are doing with their automated systems(31.9%). (5) Respondents for the most part use the functions : WWW (68. 1%), E-Mail(59.4%), FTP(52.2%), Gopher(34.8%), Wais(7.2%). (6) Respondents mentioned the following advantages : access to remote log-in database, an excellent and swift communications vehicle, reduced telecommunication cost, saving time. (7) Respondents mentioned the following disadvantages : low speed of communication, difficult of access to the relevant information and library materials, and shortage of database be distributed within Korea.

• Journal of Advanced Navigation Technology
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• v.21 no.3
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• pp.272-278
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• 2017

In order to meet performance requirements specified by the ICAO in drone operation, a system that provides augmentation information such as SBAS is needed. However, the operating range of the drone is limited in situation where the drone can not received the SBAS message continuously. In this paper, we propose a system to transmit SBAS augmentation message using a separate communication channel assuming the SBAS satellite signal to the drone has been shielded. We implemented the proposed system and verified its performance in the static environment. The DGPS positioning results showed that the accuracy difference is about 10cm, which means the accuracy performance was very similar. In addition, the protection level calculated by the system also shows the difference within 2m from the value calculated by the airborne receiver.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.6
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• pp.895-902
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• 2018

Energy consumption in buildings is close to 40% of the total national energy consumption in developed countries such as US and Japan, and Korea accounts for 24% of total energy consumption. In buildings, HVAC can't freely control the cooling flow rate according to the required calorie, so energy is not used efficiently. Therefore, by using the energy saving valve, the flow rate can be controlled by the required amount of heat and the energy can be saved. In this paper, we define basic conditions and develop control and monitoring boards for building energy saving valves based on PIC processor with low power and high cost-effectiveness. The designed board displays and transmits in real time information about two temperature values, flow values and calculated calories for temperature difference measurement. The developed board will be useful for real - time monitoring of the state of the valve in the future and development of the valve for the offshore.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.34 no.2
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• pp.207-215
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• 2016

The demand for spatial data service technologies is increasing lately with the development of realistic 3D spatial information services and ICT (Information and Communication Technology). Research is being conducted on the real-time provision of spatial data services through a variety of mobile and Web-based contents. Big data or cloud computing can be presented as alternatives to the construction of spatial data for the effective use of large volumes of data. In this paper, the process of building HLM (Hyper Live Map) using multi-source data to acquire stereo CCTV and other various data is presented and a big data service architecture design is proposed for the use of flexible and scalable cloud computing to handle big data created by users through such media as social network services and black boxes. The provision of spatial data services in real time using big data and cloud computing will enable us to implement navigation systems, vehicle augmented reality, real-time 3D spatial information, and single picture based positioning above the single GPS level using low-cost image-based position recognition technology in the future. Furthermore, Big Data and Cloud Computing are also used for data collection and provision in U-City and Smart-City environment as well, and the big data service architecture will provide users with information in real time.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.6
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• pp.1479-1485
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• 2012

The parking management system can increase driver's convenience with detailed parking information service in the parking lot. At the same time, parking management system consumes non-negligible electrical energy with large amount of sensors, displays and control modules. With the increase in the demand for green and sustainable building design all over the world, it becomes a meaningful issue for parking management system to reduce operating power. This paper presents the preliminary design and estimated results of a parking management system which is optimized to reduce the power consumption mainly on detectors and displays. The system design is based on pre-developed wireless parking detectors, Park Tile and Park Disk. The system has a number of parking space detectors, vehicle count detectors, information displays, guidance terminals and other control units. We have performed system architecture design, communication network design, parking information service scenario planning, battery life regulation and at last operating power estimation. The estimated operating power was 0.93KW per parking-slot, which is 20% of traditional systems. The estimated annual maintenance cost was 18% of traditional systems.

• The Journal of the Korea institute of electronic communication sciences
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• v.6 no.3
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• pp.337-341
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• 2011

This paper presents the design of a novel integrated mobile antenna for vehicles. The proposed antenna fabricated on a low cost easily available FR4 substrate, which effectively covers both dual band operation. The proposed mobile antenna is a modified G-type patch antenna that can operate in various frequency bands, GSM (880~960 MHz), AMPS (824~894MHz), DCS (1710~1880MHz), PCS (1850~1990MHz), UMTS (1920~2170). Experimental results indicate that the impedance bandwidth (VSWR 1:2.5) of the proposed mobile antenna agree that of the simulation results. It was validated that the configuration can meet the demands of Mobile frequency bands and effectively enhanced the impedance bandwidth to 36.46% for the lower band and 27.84% for the upper band. This paper also presents and discusses the 3D radiation patterns and gains according to the results of the experiment.