• Journal of Advanced Marine Engineering and Technology
• /
• v.27 no.3
• /
• pp.412-420
• /
• 2003

This study describes the merits of PWM control of hydraulic system using high speed on-off valves. Generally, Electro-hydraulic valves can be classified into two classification: valves which are controlled by analog signal and which are controlled by digital. The former includes hydraulic servo valves and proportional valves which require A/D converters as interface to digital computer and too costly and sensitive to oil contamination because of complexity in structures. The latter includes high speed on-off valves which do not require A/D converters because they are normally operated in a pulse width modulation(PWM) method, and are low in price and robust to oil contamination because of their simple structures. The objectives of this study is to analyze the limit cycle which regularly appear in the position control system using 2/2way high speed on-off valves and to give a criterion for the stability of this system. The nonlinear characteristics of PWM and cylinder friction of this system are described by harmonic linearization and the effects of parameter variations to the system stability are simulated.

• The Transactions of the Korean Institute of Electrical Engineers D
• /
• v.54 no.3
• /
• pp.206-214
• /
• 2005

In these days the virtual reality technology has been applied to treat such an anxiety disorders. And also a medical doctor can diagnose the patient in distance with the telemedicine system. In this thesis, an telemedicine assistant system for treatment of acrophobia using biomedical signals and virtual reality technique is proposed. I made two virtual reality simulations for treatment of acrophobia and telemedicine system for communication between doctor and patient using personal computer. Multimedia conference service, online questionary, signal transfer system are needed to configure such system. Virtual reality simulation system that composed of position sensor, head mount display, and audio system, is also included in this telemedicine system. I added virtual environment update system to this virtual reality telemedicine system for treatment of acrophobia. With this virtual environment update system, the doctors can change virtual reality simulation stage based on the status of each patient and symptom of phobia. We will apply this system to the acrophobia patient in distance and be able to offer better medical treatment for mental illness in near future.

• The Transactions of the Korean Institute of Electrical Engineers D
• /
• v.50 no.2
• /
• pp.72-79
• /
• 2001

In the GPS/DR integrated system, the GPS position(or velocity) is used to compensate the DR output and to calibrate errors of the DR sensor. This synergistic relationship ensures that the calibrated DR accuracy can be maintained even when the GPS signal is blocked. Because of the observability problem, however, the DR sensors are not sufficiently calibrated when the vehicle speed is low. This problem can be solved if we use a multi-antenna GPS receiver for attitude determination instead of conventional one. This paper designs a two-antenna GP receiver integrated with DR sensors. The proposed integration system has three remarkable features. First, the DR sensor can be calibrated regardless of the vehicle speed with the aid of two-antenna GPS receiver. Secondly, the search space of integer ambiguities in GPS carrier-phase measurements is reduced to a part of the surface of the sphere using DR heading. Thirdly, the detection resolution of cycle-slips in GPS carrier-phase measurements is improved with the aid of DR heading. From the experimental result, it is shown that the search space is drastically reduced to about 3/20 of the non-aided case and the cycle-slips of 1 or half cycle can be detected.

• Nuclear Engineering and Technology
• /
• v.54 no.2
• /
• pp.601-607
• /
• 2022

In recent years, monitoring of spent nuclear fuel inside dry cask storage has become an important area of national security. Muon tomography is a useful method for monitoring spent nuclear fuel because it uses high energy muons that penetrate deep into the target material and provides a 3-D structure of the inner materials. We designed a muon tomography system consisting of four 2-D position sensitive detector and characterized and optimized the system parameters. Each detector, measuring 200 × 200 cm², consists of a plastic scintillator, wavelength shifting (WLS) fibers and, SiPMs. The reconstructed image is obtained by extracting the intersection of the incoming and outgoing muon tracks using a Point-of-Closest-Approach (PoCA) algorithm. The Geant4 simulation was used to evaluate the performance of the muon tomography system and to optimize the design parameters including the pixel size of the muon detector, the field of view (FOV), and the distance between detectors. Based on the optimized design parameters, the spent fuel assemblies were modeled and the line profile was analyzed to conduct a feasibility study. Line profile analysis confirmed that muon tomography system can monitor nuclear spent fuel in dry storage container.

• Mycobiology
• /
• v.50 no.3
• /
• pp.181-187
• /
• 2022

To exploit insect-derived fungi, insects were collected from seven different regions in Korea, including Gyeongbuk, Goryeong, and several fungi were isolated from them. A fungal strain designated 21-64-D was isolated from riparian tiger beetle (Cicindela transbaicalica) and morphologically identified as a species belonging to the genus Oidiodendron. Phylogenetic analysis using the nucleotide sequences of internal transcribed spacer (ITS) regions and the partial sequence of the large subunit of the nuclear ribosomal RNA (LSU) gene revealed the distinct phylogenetic position of the isolate among recognized Oidiodendron species including its closest neighbors O. chlamydosporicum, O. citrinum, O. maius, and O. pilicola. The hyphal and conidial morphology of the strain, particularly club-shaped hyphae, clearly differentiated it from its close relatives. Results indicated that 21-64-D is a novel species in the genus Oidiodendron, for which the name Oidiodendron clavatum sp. nov. is proposed.

• Journal of the Korean Geotechnical Society
• /
• v.18 no.3
• /
• pp.51-59
• /
• 2002

This paper deals with development of a damage risk assessment system for adjacent buildings to under-passing tunnel face considering 3D-ground movement. The system consists of building and ground information module, monitoring data module, settlement evaluation module, and building damage risk assessment module. The major modules, settlement evaluation module and building damage assessment module, are based on settlement estimation model suggested by Attewell et al (1982) and the building damage assessment method by Mair et al. (1996). After estimating 3D-ground movements due to tunneling with settlement evaluation module, damage assessment far buildings is performed using building damage risk assessment module. The developed system has two major functions; 1) calculation of 3D-settlement with ground loss ($V_{s}$)or maximum settlement ($w_{max}$) and inflection point (i) using various empirical formulae, monitoring data, numerical results, and so on; 2) assessment of damage risk for adjacent buildings of arbitrary section with position change of tunnel face. The field data given by Boscadin and Cording (1989) leer the case of two-storied masonry building near the Metro tunnel in Washington D.C. was simulated to verify the applicability of the developed system.

• The KIPS Transactions:PartD
• /
• v.19D no.3
• /
• pp.221-228
• /
• 2012

This paper proposes a new forging work-in-process control system that guarantees independency of a specific device and provides cost-effectiveness. Until now, much research has been studied on improving the process productivity through efficient work-in-process or inventory controls. Especially, incorporating various IT technologies such as barcode, RFID, and image recognition has been done. However, those approaches cause many problems due to the characteristics of the forging work-in-process control environment. To overcome the limitations of the existing approaches, this paper proposes a novel forging work-in-process control system. The proposed system in this paper identifies and precisely manages positions of objects by using GPS information of smart mobile devices. Therefore, identification tags as well as specific devices for reading the tags do not been required. It resolves the problems of the previous approaches and enhances the productivity of the overall forging work-in-process control process.

• Journal of Korean Society on Water Environment
• /
• v.26 no.3
• /
• pp.406-412
• /
• 2010

Concentrations and speciations of Trihalomethanes (THMs) and Haloacetic acids ($HAA_5$) that can be formed during chlorine disinfection by-product (DBPs) in full-scale drinking water treatment plants were investigated. Jeon-ju D water treatment plant that adopted conventional water treatment processes was chosen for investigation. SUVA values according to water treatment process changes were observed from 1.3 to 2.1. The process average concentrations of THMs was 7.4 ppb, 9.0 ppb and 14.7 ppb respectively, while the average concentrations of $HAA_5$ by each process which are precipitation water, filterater water, treated water, were 15.5 ppb, 14.9 ppb and 25.8 ppb respectively. DBPs concentrations was lower in the winter than summer. The major species of THMs was chloroform and the second highest was bromodichloromethane (BDCM) and the third highest was dibromochloromethane (DBCM). In case of $HAA_5$, the rate of trichloroacetic acid (TCAA) was detected. The species disribution of THMs is related to the change of SUVA and species disribution of $HAA_5$ is related to the concentrations of bromine and injection position of chlorine and injection quantity.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.63 no.12
• /
• pp.1697-1703
• /
• 2014

In this paper, we propose an indoor RSSI (received signal strength indication)-based localization method that uses virtually overlapped visible light with an indoor LED lighting system. In our system, a photodiode (PD) measures the RSSI from LED lamps that blink in one row or column units. Subsequently, the RSSI is used to obtain the horizontal distances between the LED lamps and the receiver with the predetermined characteristics curve, R-D curve, that represents the relation between the RSSI and the horizontal distances. When the controlled LED lamps blink in one row or column units, the R-D curve at the border of the LED lamps is different because of the weak lighting, which results in the position sensing error of the receiver. The deviation of the optical power of each LED also causes the error. To solve these problems, we propose a method that overlaps the visible light through the numerical operation at the receiver side without any modification of the light source side. Our proposed method has been simulated in a room measuring $1.2{\times}1.2{\times}1.8m^3$ considering the effect of the error on the optical power of the LED. The simulation result shows that the proposed method eliminates the error condition with the R-D curve and achieves an average positioning error of 13.4 mm under the error rate 3% of the optical power.

• Journal of Advanced Navigation Technology
• /
• v.23 no.6
• /
• pp.526-534
• /
• 2019

Localization methods using radio signals should obtain range measurements from three or more anchors. However, a typical building consists of narrow, long hallways and corners, making it difficult to secure more than three light of sight anchors. The result is a multi-modal solution that makes it difficult to estimate the user's location. In order to overcome this problem, this paper proposes a method for estimating the location using artificial neural networks. Using the artificial neural network, even if a multi-modal solution occurs, the position can be estimated by acquiring user movement pattern information based on accumulated range measurements. The method does not require any additional equipment or sensors, and only anchor-based range measurements can estimate the user's location. In order to verify the proposed method, location estimation tests were performed in situations where the multi-modal solution occurred by installing an insufficient number of anchors in a building. As a result, it was confirmed that the location can be estimated even when the number of anchors is insufficient.