• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.1
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• pp.17-25
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• 2000

ATM PON system is regarded as a solution of the next generation access network because it can cover various types of subscribers in a single platform. In this paper, we describe the merit of the ATM PON and the key protocols for its operation. Above all, the ranging is the most important protocol providing a mean of the time-division multiple access in the system. A problem in the protocol is that the window size, the time interval that ranging cell arrives, is too long. During the interval, user traffics cannot be send to the upstream, which makes the quality of service degraded. In this paper, we suggest a method to minimize the window size when the length of the optic fiber is known with some deviation. The window size can be reduced as 7 % of the conventional method when the deviation of the length is 1 Km.

• Journal of Power Electronics
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• v.15 no.1
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• pp.146-159
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• 2015

Since the power capacity needed for the propulsion of large ships is very large, a multiphase AC induction propulsion mode is generally adopted to meet the higher requirements of reliability, redundancy and maintainability. This paper gives a detailed description of the development of a 20MW fifteen-phase PWM driver for advanced fifteen-phase propulsion induction motors with a special third-harmonic injection in terms of the main circuit hardware, control system design, experiments, etc. The adoption of the modular design method for the main circuit hardware design can make the enclosed mechanical structure simple and maintainable. It can also avoid the larger switch stresses caused by the multiple turn on of the IGBTs in conventional large-capacity converter systems. The use of the distributed controller design method based on a high-speed fiber-optic ring net for the control system can overcome such disadvantages as the poor reliability and long maintenance times arising from the conventional centralized controller which is designed according to point-to-point communication. Finally, the performance of the 20MW PWM driver is verified by experimentation on a new fifteen-phase induction propulsion motor.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.9
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• pp.6254-6259
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• 2015

On the optical system and the system itself of the noise of the noise from the outside always present. This noise is to function as reducing performance of the optical system. Therefore, the probability of error, thereby changing the system. In this paper, the error probability of the optical system due to changes in various values by introducing the characteristic variable the value of the optical system was calculated using the ${\kappa}$-square method. Was confirmed also in accordance with the calculation result is an error probability of the optical system changes, it was confirmed that when the value of the holding case for holding the standard about 400 Lux on the probability of the optical system. This case was found to be an optical system using a light source with a low output, so that means the smaller output is no problem to maintain the error probability value of the optical system is large. This means that more effective and less expensive to implement because it means that the optical system does not require the use of pre-amplifier for amplifying the signal at the receiving end of an optical system using a light source with a low output when the normal case.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.1
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• pp.89-98
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• 2002

Optical current sensor and optical voltage sensor modules were designed and fabricated to improve measurement error and insulation in automatic power distributor By using Faraday effect, optical current sensor with an $\alpha$-iron core was designed and fabricated to minimize current induction of the other phase and was optimized to maintain linearity. Optical voltage sensor was fabricated owing to the pockets effect and adopted spatial electric field type because of small room in an automatic power distributor. To connect a distributor with an external terminal for signal processing, optical multi connector was designed, fabricated and tested for coupling loss and gas leakage. The linearity of optical current sensor for applied current maintains variation of smaller than 2.5% for applied current range from 20A to 700A. The linearity of optical voltage sensor was smaller than 1% for appling voltage from 6.6kV to 19.8kV. Since the measured characteristics are good, these devices can be considered as being applicable in practice.

• Smart Structures and Systems
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• v.6 no.5_6
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• pp.641-659
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• 2010

Structural Health Monitoring (SHM) gradually becomes a technique for ensuring the health and safety of civil infrastructures and is also an important approach for the research of the damage accumulation and disaster evolving characteristics of civil infrastructures. It is attracting prodigious research interests and the active development interests of scientists and engineers because a great number of civil infrastructures are planned and built every year in mainland China. In a SHM system the sheer number of accompanying wires, fiber optic cables, and other physical transmission medium is usually prohibitive, particularly for such structures as offshore platforms and long-span structures. Fortunately, with recent advances in technologies in sensing, wireless communication, and micro electro mechanical systems (MEMS), wireless sensor technique has been developing rapidly and is being used gradually in the SHM of civil engineering structures. In this paper, some recent advances in the research, development, and implementation of wireless sensors for the SHM of civil infrastructures in mainland China, especially in Dalian University of Technology (DUT) and Harbin Institute of Technology (HIT), are introduced. Firstly, a kind of wireless digital acceleration sensors for structural global monitoring is designed and validated in an offshore structure model. Secondly, wireless inclination sensor systems based on Frequency-hopping techniques are developed and applied successfully to swing monitoring of large-scale hook structures. Thirdly, wireless acquisition systems integrating with different sensing materials, such as Polyvinylidene Fluoride(PVDF), strain gauge, piezoresistive stress/strain sensors fabricated by using the nickel powder-filled cement-based composite, are proposed for structural local monitoring, and validating the characteristics of the above materials. Finally, solutions to the key problem of finite energy for wireless sensors networks are discussed, with future works also being introduced, for example, the wireless sensor networks powered by corrosion signal for corrosion monitoring and rapid diagnosis for large structures.

• Smart Structures and Systems
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• v.6 no.5_6
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• pp.595-618
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• 2010

This paper describes the application of a wireless sensor network to a 31 meter-tall medieval tower located in the city of Trento, Italy. The effort is motivated by preservation of the integrity of a set of frescoes decorating the room on the second floor, representing one of most important International Gothic artworks in Europe. The specific application demanded development of customized hardware and software. The wireless module selected as the core platform allows reliable wireless communication at low cost with a long service life. Sensors include accelerometers, deformation gauges, and thermometers. A multi-hop data collection protocol was applied in the software to improve the system's flexibility and scalability. The system has been operating since September 2008, and in recent months the data loss ratio was estimated as less than 0.01%. The data acquired so far are in agreement with the prediction resulting a priori from the 3-dimensional FEM. Based on these data a Bayesian updating procedure is employed to real-time estimate the probability of abnormal condition states. This first period of operation demonstrated the stability and reliability of the system, and its ability to recognize any possible occurrence of abnormal conditions that could jeopardize the integrity of the frescos.

• Proceedings of the KOSOMBE Conference
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• v.1998 no.11
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• pp.57-59
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• 1998

For medical students and doctors, knowledge of the three-dimensional (3D) structure of brain is very important in diagnosis and treatment of brain diseases. Two-dimensional (2D) tools (ex: anatomy book) or traditional 3D tools (ex: plastic model) are not sufficient to understand the complex structures of the brain. However, it is not always guaranteed to dissect the brain of cadaver when it is necessary. To overcome this problem, the virtual dissection programs of the brain have been developed. However, most programs include only 2D images that do not permit free dissection and free rotation. Many programs are made of radiographs that are not as realistic as sectioned cadaver because radiographs do not reveal true color and have limited resolution. It is also necessary to make the virtual dissection programs of each race and ethnic group. We attempted to make a virtual dissection program using a 3D image of the brain from a Korean cadaver. The purpose of this study is to present an educational tool for those interested in the anatomy of the brain. The procedures to make this program were as follows. A brain extracted from a 58-years old male Korean cadaver was embedded with gelatin solution, and serially sectioned into 1.4 mm-thickness using a meat slicer. 130 sectioned specimens were inputted to the computer using a scanner ($420\times456$ resolution, true color), and the 2D images were aligned on the alignment program composed using IDL language. Outlines of the brain components (cerebrum, cerebellum, brain stem, lentiform nucleus, caudate nucleus, thalamus, optic nerve, fornix, cerebral artery, and ventricle) were manually drawn from the 2D images on the CorelDRAW program. Multimedia data, including text and voice comments, were inputted to help the user to learn about the brain components. 3D images of the brain were reconstructed through the volume-based rendering of the 2D images. Using the 3D image of the brain as the main feature, virtual dissection program was composed using IDL language. Various dissection functions, such as dissecting 3D image of the brain at free angle to show its plane, presenting multimedia data of brain components, and rotating 3D image of the whole brain or selected brain components at free angle were established. This virtual dissection program is expected to become more advanced, and to be used widely through Internet or CD-title as an educational tool for medical students and doctors.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.9
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• pp.6221-6226
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• 2015

In this paper, waveguide analysis was interpreted as an optical waveguide using the feedback perturbation method simple and easy to apply compared to the analysis method, while the other almost identical to the numerical calculation method. In addition, efficient coupling with an optical transmission line of optical fiber and the waveguide form the thin film of different functional elements is required in order to achieve the full optical communication system. However, problems arise, such as the light field (field) and the decrease of the access efficiency due to inconsistency in the distribution characteristics of the connection surface by the difference in size of the cross section thereof when connecting the optical fiber and the waveguide directly to the combination of a thin film. Therefore propose a new type of connector structure to increase the efficiency of the connection when connecting the optical fiber waveguide and the thin film was analyzed by applying a coupled mode theory, the binding efficiency of the modified contactor. And by diffusing Ti on the $LiNbO_3$ substrate and a wide range of applications in the manufacture of integrated optical material made of a current low-loss Ti: $LiNbO_3$ optical waveguide and making the Y-branch waveguide, and the properties were confirmed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.2
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• pp.213-219
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• 2012

Recently, we are simultaneously exposed by various electromagnetic sources due to an increase of mobile communication services. However, EMF(Electric, Magnetic and Electromagnetic Field) study has been performed mainly about only single frequency. The objective of this paper is to develop an multiple-frequency exposure system for in vitro experiment. The exposure unit for in vitro experiments was designed by radial transmission line type to get broadband characteristics to generate signals of CDMA at 836.5 MHz and WCDMA at 1950 MHz frequency simultaneously. The modulated signals were delivered to the conical antenna through amplifier, digital attenuator and RF combiner. SAR values were obtained by the averaged values of 3 measured values at 9 points in petri dish using the fiber optic temperature probe. The measured return loss was under -15 dB. For 1 W input power, the mean value and standard deviation of SAR were $0.105{\pm}0.019$ for the CDMA frequency and $0.262{\pm}0.055$ for the WCDMA frequency.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.2
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• pp.25-31
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• 2020

In an optical system that serves as the backbone of an information transmission system, it is essential to evaluate the statistical characteristics of the signal and noise for a performance evaluation and optimization of the system. The optical receiver system improves the reception sensitivity by adopting an optical amplifier in front of the optical detector to improve the reception sensitivity, but some problems change the bandwidth of the electronic signal to the optical signal in the optical receiver due to the ASE noise added to the output of the optical detector. The problem of changing the ratio of the bandwidth of these signals varies according to the passband characteristics of the filter present at the output stage. The frequency response effect can be solved by constructing an infinite order filter, but it is almost impossible to implement it. In this paper, the Butterworth filter was implemented to evaluate the frequency response characteristics of an optical receiver system according to the filter order. The simulation results showed that the receiver sensitivity increases as the order of Butter-Worth filters increases. In addition, as a result of simulation of the change of various values, it was confirmed that the reception sensitivity increased with increasing. That is, the average photocurrent increases, and the dispersion decreases with increasing.