• Journal of the Korean Institute of Telematics and Electronics D
• /
• v.36D no.3
• /
• pp.1-11
• /
• 1999

It is now common practice to utilize the quadrature RF coils to improve the signal-to-noise ratio (SNR) in the Magnetic Resonance Imaging (MRI) System. In addition, to make such an available SNR improvement, it is mandatory to use a well-designed quadrature coupler, which facilitates a perfect 3-dB coupling and quadrature-phase shift. However, the four ports matching condition has to be well considered during the RF excitation and the signal detection period. This work investigates the effects of such a mismatching condition (especially, due to patient) from the analysis, simulation, and real implementation and firstly proposes dynamic loading technique for a quadrature coupler and transmitting/receiving switch module to minimize a patient mismatching and enhance a system reliability. Also, we designed and implemented the quadrature coupler and transmitting/receiving switch module using microstrip. As a result, the SNR of our MRI system using the microstrip quadrature coupler and transmitting/receiving switch module with dynamic load increases 3 dB compared with the old one using USA quadrature switch. Also, the power capability of quadrature coupler and transmitting/receiving switch module is 5-kw peak power. Considering power loss and reduction of size, we used a RT/duroid 6010 substrate with high permittivity and for simulation we use Compact Software.

• Korean Journal of Optics and Photonics
• /
• v.26 no.1
• /
• pp.23-29
• /
• 2015

In this paper, we propose a microscope system for detecting both a tumor and blood vessels in brain tumor surgery as fluorescence images by using multiple light sources and a beam-splitter module. The proposed method displays fluorescent images of the tumor and blood vessels on the same display device and also provides accurate information about them to the operator. To acquire a fluorescence image, we utilized 5-ALA (5-aminolevulinic acid) for the tumor and ICG (Indocyanine green) for blood vessels, and we used a beam-splitter module combined with a microscope for simultaneous detection of both. The beam-splitter module showed the best performance at 600 nm for 5-ALA and above 800 nm for ICG. The beam-splitter is flexible to enable diverse objective setups and designed to mount a filter easily, so beam-splitter and filter can be changed as needed, and other fluorescent dyes besides 5-ALA and ICG are available. The fluorescent images of the tumor and the blood vessels can be displayed on the same monitor through the beam-splitter module with a CCD camera. For ICG, a CCD that can detect the near-infrared region is needed. This system provides the acquired fluorescent image to an operator in real time, matching it to the original image through a similarity transform.

• Korean Journal of Materials Research
• /
• v.5 no.7
• /
• pp.781-785
• /
• 1995

from the $K_{6}$P$_4$ $O_{13}$ flux using a temperature cooling method. According to SHG outpower measurement, phase matching angle is $\theta$=90$^{\circ}$, $\Phi$=23.3$^{\circ}$and angular acceptance of $\Phi$ direction is about 2 degree, Deviation of phase matching angle due to index inhomogeneity in KTP crystal is 0.17 degree. A 20mW green laser was obtained with the combination of a intracavity Nd ; YAG and KTP crystal.

• Journal of IKEEE
• /
• v.26 no.3
• /
• pp.456-461
• /
• 2022

In this paper, a two-stage single-ended power amplifier (PA) with broadband gain characteristics was presented by utilizing a radio frequency (RF) transformer (TF), which is essential for a differential amplifier. The bandwidth of a PA can be improved by designing TF to have broadband characteristics and then applying it to the inter-stage matching network (IMN) of a PA. For broadband gain characteristics while maintaining the performance and area of the existing PA, an IMN was implemented on an monolithic microwave integrated circuit (MMIC) and a multi-layer printed circuit board (PCB), and the simulation results were compared. As a result of simulating the PA module designed using InGaP/GaAs HBT model, it has been confirmed that the PA employing the proposed design method has an improved fractional bandwidth of 19.8% at a center frequency of 3.3GHz, while the conventional PA showed that of 11.2%.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.17 no.1
• /
• pp.11-19
• /
• 1999

Lately, with the development of the fields of computer and photogrammetry, Digital Photogrammetric Systems are widely used for the generation of GIS basemap, the acquisition of topographic information and DEM, the formation of digital orthophoto, three-dimensional viewing and so on. According as the demand for the systems is rapidly increasing, we suggest keenly the necessity of domestic technical development, because all of these systems depend on foreign technology until now. In this study, by using digital photogrammetry method, with Visual C++ language, we have developed Digital Photogrammetric Systems for Windows which is able to get three-dimensional coordinates through interior orientation, exterior orientation, epipolar line, image matching from a pair of aerial photos taken with metric camera. This system consists of not only a module which can revise digital map that is being made at National Geographic Institute as a part of data construction project of National Geographic Information System, but also a module which can view three-dimensional image on the screen monitor by using anaglyph for three-dimensional analysis. The digital photogrammetry modules developed in this study are expected to be used as primary modules for the effective management of the urban as well as main modules in developing professional digital photogrammetric systems.

• Korean Journal of Optics and Photonics
• /
• v.19 no.2
• /
• pp.122-126
• /
• 2008

Dual backlight unit incorporating a single light source integrated with a beam splitting reflector was demonstrated, providing a surface light beam for both the keypad and the display section simultaneously. The reflector was realized by aligning a groove substrate with a matching cover, and a light guiding module comprising a stack of light guide panels and prism/diffuser sheets was attached to both sides of the reflector. A light emanating from the light source-placed in the middle of the substrate-undergoes a series of reflections through the reflector to reach the input of the light guiding module. Then it is transformed into a surface light beam, which is used to irradiate the keypad and display sections simultaneously. As for the accomplished dual surface light sources, the measured average luminance and the spatial luminance uniformity were respectively about $420\;cd/m^2$ and 69% for the keypad section, and $640\;cd/m^2$ and 79% for the display section.

• Journal of Sensor Science and Technology
• /
• v.24 no.4
• /
• pp.228-231
• /
• 2015

Ultrasonic motors provide high torques and quick responses compared to their magnetic counterparts; therefore, they are widely used in small-scale applications such as mobile phones, microrobots, and auto-focusing modules in digital cameras. To determine the feasibility of lead-free piezoceramics for ultrasonic motor applications, we fabricated a ring-type piezoceramic with a KNN-based lead-free piezoceramic (referred to as CZ5), intended for use in an auto-focusing module of a digital camera. The vibration of the lead-free stator was observed at 45.1 kHz. It is noteworthy that the fully assembled lead-free ultrasonic motor exhibited a revolution speed of 5-7 rpm, even though impedance matching with neighboring components was not considered. This result suggests that the tested KNN-based piezoceramic has great potential for use in ultrasonic motor applications, requiring minimal modifications to existing lead-based systems.

• Journal of KIISE:Computing Practices and Letters
• /
• v.15 no.11
• /
• pp.831-835
• /
• 2009

Volunteer computing is a computing paradigm in which the operations of a large-scale application are processed using idle resources of Internet-connected computers. The redundant-work distribution techniques used in the volunteer computing environment cause some problems like delay of the work completion time or inefficiency of the work execution due to continuous requests of the work redistribution because the techniques do not consider the characteristics of works and dynamic resources. To cope with such problems this paper suggests a P2P based regional matchmaking technique which can redistribute works in consideration of the characteristics of the works and the participant resources. The techniques consist of the profiles for works/resources, the module for monitoring the available resources spaces, the protocols for the matching request/reply, the module for match-ratio calculation, and so on.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.20 no.2
• /
• pp.15-21
• /
• 2010

The user authentication using fingerprint information not only provides the convenience but also high security. However, the fingerprint information for user authentication can cause serious problems when it has been compromised. It cannot change like passwords, because the user only has ten fingers on two hands. Recently, there is an increasing research of the fuzzy fingerprint vault system to protect fingerprint information. The research on the problem of fingerprint alignment using geometric hashing technique carried out. This paper proposes the hardware architecture fuzzy fingerprint vault system based on geometric hashing. The proposed architecture consists of software and hardware module. The hardware module has charge of matching between enrollment hash table and verification hash table. Based on the experimental results, the execution time of the proposed system with 36 real minutiae is 0.2 second when 100 chaff minutiae, 0.53 second when 400 chaff minutiae.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.21 no.3
• /
• pp.29-34
• /
• 2021

For the purpose of Application to the small radar sensor, the MMIC Chips, which are the core component of the W-band, was designed in Korea according to the characteristics of the transceiver and manufactured by 60nm GaN and 0.1㎛ GaAs pHEMT process. The output power of PA is 28 dBm at center frequency of W-band and Noise figure is 6.7 dB of switch and LNA MMIC. Output power and Noise figure of MMIC chips developed in domestic was applied to the transmitter and receiver module through W-band waveguide low loss transition structure design and impedance matching to verify the performance after the fabrication are 26.1~27.7 dBm and 7.85~10.57 dB including thermal testing, and which are close to the analysis result. As a result, these are judged that the PA and Switch and LNA MMICs can be applied to the small radar sensor.