• Journal of the Korean Society of Safety
• /
• v.12 no.3
• /
• pp.38-44
• /
• 1997

6063-T5 alloys are tested in laboratory air, water and 3% NaCl solution to investigate the effects of corrosive environment on the retardation behavior through single overload fatigue test. Also, the fatigue crack propagation and the crack closure behavior are studied. The results obtained in this experimental study are summarized as follows. 1) Behaviors of fatigue crack growth retardation are observed in water and 3% NaCl solution as they do in air. The number of delay cycles and the size of affected region by single overload decrease greatly in water and 3% NaCl compared with those in air. 2) In fractographic results, the overload marking by single overload appear remarkably in air, but indistinctly in water and 3% NaCl solution. 3) The effect of crack closure on crack propagation is most remarkable in the beginning of crack propagation. With crack propagation, the crack closure level and its effect decrease greatly.

• ETRI Journal
• /
• v.34 no.6
• /
• pp.911-921
• /
• 2012

In high-speed wireless communications, an analysis of the propagation characteristics is an important process. Information on the propagation characteristics suitable for each environment significantly helps in the design of mobile communications. This paper presents the analysis results of radio propagation characteristics in outdoor environments for a new mobile wireless system at 781 MHz. To avoid the interference of Korean DTV broadcasting, we measure the channel characteristics in urban, suburban, and rural areas on Jeju Island, Republic of Korea, using a channel sounder and $4{\times}4$ antenna. The path loss (PL) measurement results differ from those of existing propagation models by more than 10 dB. To analyze the frequency characteristics for Korean propagation environments, we derive various propagation characteristic parameters: PL, delay spread, angular spread, and K-factor. Finally, we verify the validity of the measurement results by comparing them with the actual measurement results and 3D ray-tracing simulation results.

• Journal of Digital Contents Society
• /
• v.8 no.4
• /
• pp.459-465
• /
• 2007

In this paper, we implemented a ray-tracing simulator with a ray-launching technique and generated the propagation path of each ray in a multiple-wall indoor environment. In this simulator, we adopted two dimension ray-tracing techniques considering the reflection and penetration were dominant propagation factor in the indoor channel. From the result, we verified that this ray-tracing simulator shows the similar path pattern and delay distribution with the experiment results of the previous research. Especially, impulse responses of the ray were corresponding to reference result in non-line of sight of multiple-wall indoor environment. Furthermore, we confirmed that channel profiles having respectively different departure angle 1 degree to 7 degree were similar between them.

• Proceedings of the IEEK Conference
• /
• 1998.10a
• /
• pp.779-782
• /
• 1998

This paper describes a high-speed Dual-modulus Prescaler (DMP) for RF mobile communication systems with pulse remover using selective latch technique. This circuit achieves high speed and low power consumption by reducing full speed flip-flops and using a selective latch. The proposed DMP consists of only one full speed flip-flop, a selective latch, conventional flip-flops, and a control gate. In order to ensure the timing of control signal, duty cycle problem and propagation delay must be considered. The failling edgetriggered flip-flops alleviate the duty cycle problem andthis paper shows that the propagation delay of control signal doesn't matter. The maximum operating frequency of the proposed DMP with 0.6um CMOS technology is up to 2.2㎓ at 3.3V power supply and the circuit consumes 5.24mA.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.3 no.4
• /
• pp.787-794
• /
• 1999

This paper presents an ENMODL(enhances NORA MODL) circuit and implements a high-speed 32 bit CLA(carry lookahead adder) with the new dynamic logics. The proposed logic can reduce the area and the Propagation delay of carry because output inverters and a clocking PMOS of second stage can be omitted in two-stage MODL(multiple output domino logic) circuits. The 32-bit CLA is implemented with 0.8um double metal CMOS Process and the carry propagation delay of the adder is about 3.9 nS. The ENMODL circuits can improve the performance in the high-speed computing circuits depending on the degree of recurrence.

• Proceedings of the KIEE Conference
• /
• 2005.05a
• /
• pp.194-196
• /
• 2005

The command processor in satellite handles the capability of the process of command transmitted from ground station and deliver the processed data to on board computer in satellite. The command processor is consisted of redundant box to increase the reliability and availability of the capability. At each command processor, the processing time of each command processor is different, so the mismatch of processing time makes it difficult to timely synchronize the reception to on board computer and even will be became worse under the command processor's fault. To minimize the tine loss induced by the command processor's fault on board computer must analyze the time distribution of command propagation. This paper presents the logic of minimizing the delay error of command propagation the logic of analyzing the output of command processor.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.1 no.1
• /
• pp.105-111
• /
• 1997

This Paper Proposes a new efficient system design strategies for the acoustic-based underwater multiple modem and media access control protocol. The system aims to establish the acoustic-based communication network of an underwater vehicles for deep sea mining, which ensures a certain level of maximum throughput regardless of the propagation delay of acoustic and allows fast data transmission through the acoustic-based multiple channel. A media access control protocol for integrated communication network and it's acoustic-based communication modems that allows 'peer-to-peer' communication between a surface mining plant multiple underwater system is designed, and the proposed media access control protocol is implemented for its verification. Furthermore, a proposed design strategies which make it possible to control the multiple vehicle for an underwater mining is presented in this paper.

• Proceedings of the IEEK Conference
• /
• 2003.07a
• /
• pp.314-317
• /
• 2003

In this paper, a measurement and analysis program is developed, that can be utilized to measure and analyze radio propagation characteristics. This program is able to control the measurement instruments including spectrum analyzer through a GPIB interface, and analyze the measured data to yield mean excess delay and RMS delay spread. The measured path loss can be compared with theoretical path loss in free space or inside tunnels. The measured and analyzed results can also be presented in the forms of graphs. As those tasks can be conducted on the measurement spot, this program is very helpful for performing and verifying measurements.

• Tunnel and Underground Space
• /
• v.4 no.1
• /
• pp.38-46
• /
• 1994

This paper concerns the design of blasts adjacent to structures and facilities. In order to investigate the site characteristics, measurements of in-situ wave propagation and laboratory tests of rock cores taken from the boreholes were carried out. Effects of rock media and delay intervals on ground vibration levels were identified from over sixty measurements of three times of test blasts. For practical use in the field, an empirical propagation equation was derived so as to reflect the characteristics of rock media and delay effects. Safe limits of vibration level for structures were conservatively established based on various suggested criteria. Safe limits for facilities were adopted so that vibration levels induced by blasting should not exceed the allowable limits specified in the manufacturer's installation condition. Suggested were blast pattern and operation to enhance the rock fracturing and to reduce the ground vibration levels under the restricted conditions.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2017.05a
• /
• pp.621-624
• /
• 2017

In this paper, we propose a protocol synchronizing to packet trains in a underwater acoustic networks with limitations such as long propagation delay, low data rate, high packet loss. The proposed protocol employs an one-way communication scheme to calculate packet arrival time differences of consecutively transferred packets and minimizes uncertain variation effect of long propagation delay. Simulation results shows the superiority of our protocol, compared with a previously proposed one under the given network conditions.