• Proceedings of the IEEK Conference
• /
• 2000.06a
• /
• pp.181-184
• /
• 2000

In this paper, performance of an optical CDMA system with PCCC and SCCC is simulated and compared. It is assumed that optical channel is an intensity modulated (IM) channel and direct-detection scheme is employed to detect the received optical signal. The modulation scheme used is pulse-position-modulation (PPM). The performance is evaluated in terms of bit error probability. From the simulation results, it is shown that turbo coding offers considerable coding gain with reasonable encoding/decoding complexity.

• Proceedings of the KIEE Conference
• /
• 2004.07c
• /
• pp.1787-1789
• /
• 2004

This paper deals with the lightning effects on aircraft. The effects are divided into two groups. The one is the direct effect due to the direct attachment of the lightning channel and/or conduction of lightning current. The other is the indirect effect like electrical transients induced by lightning in aircraft conductive components such as electric circuits. In this paper presents the analysis of lightning mechanism.

• 한국정보통신설비학회:학술대회논문집
• /
• 2009.08a
• /
• pp.112-114
• /
• 2009

In this paper, a PN code tracking loop with extended Kalman filter (EKF) is proposed for a direct-sequence spread-spectrum. EKF is used to estimate amplitude and delay in a multipath fading channel. It is shown that tracking error performance is significantly improved by EKF compared with a conventional tracking loop.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
• /
• 2000.11a
• /
• pp.154-157
• /
• 2000

One of the problems using DCR(Direct Conversion Receiver) type architecture are DC offset, Poor channel selectivity. APDP(Anti Parallel Diode Pair) can be mood candidate for the DCR frequency mixer due to its inherent 2nd harmonic suppression. APDP shows good IP2 and DC suppression. This paper describes single APDP LO power characteristics, IP2, and receiver structure utilizing APDP frequency mixer.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2006.10a
• /
• pp.193-194
• /
• 2006

• Design & Manufacturing
• /
• v.9 no.3
• /
• pp.34-40
• /
• 2015

In the study, Three-dimensional drawing parts for conformal cooling circuit cavity & core and their 3D Metal parts using DMLS(Direct MetalLaser Sintering) and NC integrated machining center were showned. For conformal cooling circuit cavity and core parts, I discussed its practicality to DMLS multiple machinins process introducing general manufacturing process and comparing with them.

• Journal of the Korean Institute of Telematics and Electronics S
• /
• v.34S no.5
• /
• pp.1-14
• /
• 1997

We consider transmission beamforming techniques for frequency-division-duplex (FDD) wireless communication systems using adaptive arrays to improve the signal quality of the array transmission link. We develop a simple effective transmission beamforming technique based on an approximated frequency tranlsation (AFT) to derive the tranmsiion beamforming weights from the uplink channel vector. This technique exploits the invariance of the short-time averaged fast fading statistics to small frequency translations. A simple approximate relationship that relates the transmission channel vector to the reception channel vector is derived. We have developed its practical alternative in which the frequency translation of the channel vector is performed at the principal angle of arrival (AOA) of the u;link synthestic angular spectrum instead of the mean AOA. To analyze the performance of the proposed methods, we consider the power loss incurred by applying the estimated channel vector instead of the true downlink channel vector. The performance is analyzed as a function of the mean AOA, the angular spread, the number of elements, frequncy difference between the uplink and the downlink, and the angle distribution. Their performance is also compared with that of the direct weight reuse method and the AOA based methods.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.7 no.2
• /
• pp.120-131
• /
• 2007

A comprehensive short channel analytical model has been proposed for High Electron Mobility Transistor (HEMT) to obtain higher cut-off frequency maintaining the reliability of the device. The model has been proposed to consider generalized doping variation in the directions perpendicular to and along the channel. The effect of field plates and different gate-insulator geometry (T-gate, etc) have been considered by dividing the area between gate and the high band gap semiconductor into different regions along the channel having different insulator and metal combinations of different thicknesses and work function with the possibility that metal is in direct contact with the high band gap semiconductor. The variation obtained by gate-insulator geometry and field plates in the field and channel potential can be produced by varying doping concentration, metal work-function and gate-stack structures along the channel. The results so obtained for normal device structure have been compared with previous proposed model and numerical method (finite difference method) to prove the validity of the model.

• Journal of Distribution Research
• /
• v.9 no.2
• /
• pp.29-43
• /
• 2004

This research analyzed multi-channel strategy from the viewpoint of the customer relationship management. We hypothesized that the purchase frequency, monetary, purchase quantity of the existing customers should have increased after they used multiple channels of a company for shopping, All the hypothesis were supported in an empirical test using the customer database of a Korean TV home-shopping company, The result showed that the multi-channel strategy can be used to increase the life-time value of existing customers. Still there were a lot of customers who insists using traditional channel, which calls for a new strategy inducing them to use multi- channel for shopping.

• Nuclear Engineering and Technology
• /
• v.40 no.2
• /
• pp.139-146
• /
• 2008

This paper presents two of the fuel channel designs being considered for the CANDU-SCWR, a pressure-tube type supercritical water cooled reactor. The first is an insulated pressure tube design. The pressure tube is thermally insulated from the hot coolant by a porous ceramic insulator. Each pressure tube is in direct contact with the moderator, which operates at an average temperature of about $80^{\circ}C$. The low temperature allows zirconium alloys to be used. A perforated metal liner protects the insulator from being damaged by the fuel bundles and erosion by the coolant. The coolant pressure is transmitted through the perforated metal liner and insulator and applied directly to the pressure tube. The second is a re-entrant design. The fuel channel consists of two concentric tubes, and a calandria tube that separates them from the moderator. The coolant enters between the annulus of the two concentric fuel channel tubes, then exits the fuel channel through the inner tube, where the fuel bundles reside. The outer tube bears the coolant pressure and its temperature will be the same as the coolant inlet temperature, ${\sim}350^{\circ}C$. Advantages and disadvantages of these designs and the material requirements are discussed.