• Journal of Satellite, Information and Communications
• /
• v.6 no.2
• /
• pp.125-130
• /
• 2011

In this paper, there was compared to the performance of the Auto Correlation Feature of each code using Spreading code for improving the data transmission technology in T-DMB disaster broadcasting. Generally, wireless mobile communication environment such as DMB occur the Inter Code Interference and the Multi-Path Interference in the process of the identification of the transmitter from the receiver. To solve this problem, spreading code technology was able to improve the security property. Also, it will be able to use in many fields of signal processing, because to control a period of the code can be variable. Therefore, in this paper, we studied to compare the performance of excellent orthogonal Golay code, Kasami code and ZCD(Zero Correlation Duration) code.

• Journal of the Korean Magnetics Society
• /
• v.13 no.2
• /
• pp.59-63
• /
• 2003

Superparamagnetic properties of self-aggregated cobalt nanoparticles in the perfluorinated ion-exchange polymeric membrane (MF-4SK) prepared by ion-exchange and recovery methods were investigated by transmission electron microscopy (TEM) and superconducting quantum interference device (SQUID) magnetometer at various temperatures. Our experimental results show that cobalt nanoparticles in MF-4SK for the concentration of $7.8{\times}10^{19}$ atoms per 1 g of polymer membrane exhibit superparamagnetic properties above the average blocking temperature ($T_{B}$), which is determined to be around 185 K at applied field of 500 Oe. The average particle radius of 4.0 nm achieved from Langevin function fit is in good agreement with TEM observations. This experimental evidence suggests that cobalt nanoparticles in polymer film obey a single domain theory. The results are discussed in the light of current theory for the superparamagnetic behavior of magnetic nanoparticles.

• Journal of the Korean Magnetics Society
• /
• v.3 no.2
• /
• pp.143-148
• /
• 1993

$Bi_{x}Dy_{3-x}Al_{1}Fe_{4}O_{12}$(x=1, 1.2, 1.5) magnetic garnet films were fabricated on the glass substrates by pyrolysis method. As the Bi content was increased, the saturation magnetization increased from 5 emu/cc to 11 emu/cc and all the films showed perpendicular magnetic anisotropy. As the content of Bi was increased, Faraday rotation angle (${\theta}_F$) at 780 nm of the films increased from $0.11^{\circ}/\mu\textrm{m}$ to $0.20^{\circ}/\mu\textrm{m}$ and the garnet crystallization temperature decreased from $660^{\circ}C$ to $630^{\circ}C$. Also, the coercivity ($H_{c}$) decreased from 1200 Oe to 600 Oe and the grain sizes increased. $H_{c}$ decreased from 1750 Oe to 1200 Oe and ${\theta}_F$ increased due to the interference of the reflected laser light as the thickness of the films increased from $2000\;{\AA}$ to $4000\;{\AA}$.

• The Journal of the Acoustical Society of Korea
• /
• v.15 no.1
• /
• pp.17-22
• /
• 1996

Planar array of acoustic transducer is normally used in a sonar system. Acoustic radiation makes beam pattern in underwater uses. The main source of the beam pattern is due to the transducer array. Therefore, estimation of the acoustic radiated power is necessary to predict the performance and efficiency of the transducer. As an example of the acoustic radiation power, nine acoustic transducers mounted to a rigid infinite baffle are considered in a theoretical model. Each piston's acoustic radiation consists of self- and mutual-radiation impedances. Total radiation impedances and acoustic radiation power of the transducers are extracted using on the theory of an equivalent electric circuit. The theoretical results reveal that acoustic radiation power of the transducer depends on the mutual coupling effects.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2016.10a
• /
• pp.973-975
• /
• 2016

In this paper, we propose a selective extended Kalman filter based accurate pose estimation of the rigid body using a sensor fusion method. The pose of a rigid body can be estimated roughly by the Gauss-Newton method using the acceleration data and geomagnetic data, which can be refined with vision information and the gyro sensor information. However strong external interference noise makes the rough pose estimation difficult. In this paper, according to the measurement level of the external interference noise, the extended Kalman filter selectively uses mostly vision and gyro sensor information to increase the estimation credibility under strong interference noise environment.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.11 no.3
• /
• pp.277-282
• /
• 2016

Effect of spectral drift in coherent fiber laser was investigated by injecting optical feedback to Fabry-Perot resonance loop. Er+3 doped fiber laser having unilateral optical feedback loop in Fabry-Perot configuration using two FBGs was fabricated. The optical feedback was found to be effective in linewidth reduction of fiber laser compared to the case without any optical feedback. The linewidth of three fiber lasers using above configuration were measured to be within 3kHz which is resolution-limited performance of self-heterodyne linewidth measurement set-up. The frequency drift measurement using Mach-Zehnder measurement set-up having 200m optical delay-line in one arm showed that the frequency drift rate of optical feedback fiber laser was measured as 300kHz/sec which was better than the case without optical feedback.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.30 no.5
• /
• pp.471-478
• /
• 2010

Thin films play an important role in many technological applications including microelectronic devices, magnetic storage media, MEMS and surface coatings. It is well known that a thin film's material properties can be very different from the corresponding bulk properties and thus there has been a strong need for the development of a reliable test method to measure the mechanical properties of a thin film. We have developed an alternative and convenient test method to overcome the limitations of previous membrane deflection experiment and uniaxial tensile test by adopting a white light interferometer having sub-nanometer out-of-plane displacement resolution. The freestanding aluminium specimens are tested to verity the effectiveness of the test method developed and get the tensile properties. The specimens are 0.5 rum wide, $1{\mu}m$ thick and fabricated through MEMS processes including sputtering. 1 to 5 specimens are fabricated on Si dies. The membrane deflection experiments are carried out by using a homemade tester consisted of a motor-driven loading tip, a load cell, and 6 DOF alignment stages. The test system is compact enough to set it up beneath a commercial white light interferometric microscope. The white light fringes are utilized to align a specimen with the tester. The Young's modulus and yield point stress of the aluminium film are 62 GPa and 247 MPa, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.23 no.7
• /
• pp.1797-1806
• /
• 1998

Future satellite communication systems will be developed at Ka-band (20/30 GHz) owing to the relatively wide frequency allocation and current freedom from terrestrial interference for multimedia services. A serious disadvantage of the Ka-band, however, is the very high atmospheric attenuation in rainy weather. Synchronous CDMA drastically redces the effect of self-noise with several interesting features of CDMA for mobile communications such as fixible freuqncy rese, the capability of performin soft-handover and a lower sensitivity to interference. This paper evaluates the performance of a synchronous CDMA reture link for a Ka-band geostationary satellite communication system. For a fixed satellite channel whose characteristics depend on weather conditions, the signal envelope and phase for this channel is modelled as Gaussian. The bit error and outage probability, and the detection loss due to imperfect chip timing synchronization is analytically evaluated and the system capacity degaradation due to the weather condition is estimated. The two cases consist of the general case in which all users are affected by rain condition, and the worst case in which the reference user is only affected by rain attenuation. the results for two cases of rain condition clearly show that synchronous CDMA eases the power control requirements and has less sensitivity to imperfect power control.

• Korean Journal of Social Welfare Studies
• /
• no.39
• /
• pp.83-113
• /
• 2008

The purpose of the study is to explore the mental health social workers' experiences concerning client's self-determination by grounded theory, one of the qualitative method. Although a lot of previous studies has proved that the practitioners have suffered from the ethical considerations in their practice, on which the matter of client's self-determination is centered, little attention is paid to deep exploration of practitioners' real experience about those aspects. To carry out the research question, first, through literature reviews focusing on clarify the underlying issues about client's self-determination, three intrinsic clues are found out; incompetence, medical benefits, the harm to the third party. Data obtained by in-depth interview with 10 participants are analyzed by employing the methode developed by Corbin and Strauss, which could categorize the raw data into several high-level concepts and constructs. The findings of the study show that most practitioners would consider the clients as the intrinsic subject of self-determination. Therefore, in practice, they are trying to support the client's self-determination even within the some constraints. In addition, they also experience the clients' latent potential in actualizing autonomy and self-determination, and identifies the positive effect of self-determination not only on the client's self-help and mental health but also on the practitioners themselves. The results of the study clearly suggests that it is critical to provide the practitioners with adequate ethical education and training to help them to overcome their ethical suffering concerning clients self-determination.

• Journal of KIISE:Software and Applications
• /
• v.36 no.10
• /
• pp.825-835
• /
• 2009

The advance in medical technology has decreased death rates from diseases such as tubercle, pneumonia, malnutrition, and hepatitis. However, death rates from cardiac diseases are still increasing. To prevent cardiac diseases and quantify cardiac function, magnetic resonance imaging not harmful to the body is used for calculating blood volumes and ejection fraction(EF) on routine clinics. In this paper, automatic left ventricle(LV) segmentation is presented to segment LV and calculate blood volume and EF, which can replace labor intensive and time consuming manual contouring. Radial threshold determination is designed to segment LV and blood volume and EF are calculated. Especially, basal slices which were difficult to segment in previous researches are segmented automatically almost without user intervention. On short axis cardiac MRI of 36 subjects, the presented algorithm is compared with manual contouring and General Electronic MASS software. The results show that the presented algorithm performs in similar to the manual contouring and outperforms the MASS software in accuracy.