• 제어로봇시스템학회:학술대회논문집
• /
• 2000.10a
• /
• pp.118-118
• /
• 2000

This paper suggests the methodology to guarantee the rea1-time service over Ethernet and TCP/IP and to solve the problems such as re-transmission due to collision and platform-transparency and independence. This paper proposes a new mechanism called Real-time Ethernet protocol combined the centralized medium control mechanism with the token passing mechanism. The centralized medium control mechanism is used to get the token, the right to transmit the data, and the token passing mechanism is used to return the token to the token controller and to transmit data within the specified time interval. The proposed Real-Time Ethernet Protocol is based on Java and Java RMI(Remote Method Invocation). The presented protocol is believed to work enough in real-time applications considering latency occurred due to the Java RMI, which is less small than data transmission time.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.8 no.11
• /
• pp.3638-3654
• /
• 2014

Cognitive Radio (CR) users need to sense the environment or channel at regular time interval for sharing the spectrum band of the primary users (PUs). Once find the spectrum idle, CR users start their transmission through it. Even while transmitting, they need to continue the sensing process so that they can leave the spectrum immediately whenever find a PU wanting to use the band. Therefore, detecting PUs is one of the main functions of cognitive radio before transmission and higher the detection probability ensures better protection to the primary users. However, it is not possible to attain a high detection probability (or a low miss detection probability) and low false alarm probability simultaneously as there is a tradeoff between false alarm probability ($P_{fa}$) and the probability of detection ($P_d$). In this paper, the author has provided a comprehensive study on different sensing techniques and discussed their advantages and disadvantages. Moreover, it is expected that, with this article, readers can have a through understanding of sensing techniques in CR and the current research trends in this area.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.61 no.5
• /
• pp.676-682
• /
• 2012

To review application of HVDC (High Voltage Direct Current) transmission line to HVAC T/L in operation, reduced-scale model was designed and manufactured. The arms of model were designed to change height and interval of conductors. Electrical environmental interferences were estimated by various configuration of AC 345kV and DC 250kV T/L. The interferences such as electric field intensity and ion current density were measured and converted reduced-scale factor to full-scaled. Additionally, effects between AC and DC T/L were studied.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.24 no.2
• /
• pp.183-189
• /
• 1987

The performance of frame synchronization can be represented by the values of three characteristic variables-average misframe interval, average syncloss detection time, average reframe time. In this paper, we have analyzed the performance of frame synchronization of the standardized 90Mb/s optical transmission system by Markov chain method, with the suggestion of an extended algorithm for performance improvement. Maximum average reframe time of 1.18 ms can be obtained by the suggested algorithm, which is compared with that of 2.28 ms for the existing algorithm.

• MALSORI
• /
• no.43
• /
• pp.45-55
• /
• 2002

High reliability of automatic speaker recognition regardless of voice conditions is necessary for forensic application. Audio recordings in real cases are not consistent in voice conditions, such as duration, time interval of recording, given text or conversational speech, transmission channel, etc. In this study the variation of verification error rate of ASR system with the voice conditions was investigated. As a result in order to decrease both false rejection rate and false acception rate, the various voices should be used for training and the duration of train voices should be longer than the test voices.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.41 no.8
• /
• pp.924-927
• /
• 2016

In this paper, we consider a cumulative distribution function (CDF)-based opportunistic scheduling for downlink transmission in a cellular network consisting of a base station and multiple mobile stations. We present a closed-form formula for the average starvation period of each mobile station (i.e., the length of the time interval between two successive scheduling points of a mobile station) over Markov time-varying channels. Based on our formula, we investigate the starvation period of the CDF-based scheduling for various system parameters.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.13 no.9
• /
• pp.1941-1946
• /
• 2009

Wireless sensor networks do the monitoring and collecting information in the environment instead of human. Sensor networks are consisted of small sensor nodes with very limited hardware resource and very low network bandwidth. The wireless communication environment causes lots of communication errors so that the sensor network requires error correction technique to increase the reliability of network. The performance of error correction technique could be increased by the researches about the error pattern of CRC. In the paper, we did the performance evaluation - transmission interval, distance between sensor nodes, racket size, and RF power - that affects to the success ratio of data transmission in the indoor environment. we propose the performance metrics of system configuration based on the analysis of performance evaluation.

• Journal of Satellite, Information and Communications
• /
• v.6 no.1
• /
• pp.12-18
• /
• 2011

Signal fading due to rain is one of the most significant factors degrading link quality in satellite communication systems. Adaptive transmission is considered to be the most efficient means to countermeasure the rain attenuation. In order to develop and design a good adaptive transmission system, we need a dynamic rain attenuation model which can synthesize time series of rain attenuation. In this paper, we present a modeling technique for dynamic rain attenuation using a Markov process. We derive statistical fading properties of the rain attenuation data measured in second time interval and define four states in the Markov process. We synthesize the rain attenuation data using the 4-state Markov process, and compare statistical properties of the simulated data to those of the measured data.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.7 no.4
• /
• pp.611-621
• /
• 1995

The objectives of this study are to find out and to analyze the heat transmission characteristics of the conventional and prefabricated Ondol systems. To compare the thermal characteristics of these Ondol, a real sized Ondol model is set in a chamber. Hot water whose temperature is varied from $45^{\circ}C$ to $60^{\circ}C$ with $5^{\circ}C$ interval is supplied to each Ondol system. At that time the temperature distribution of floor surface, the amount of supplied heat, the heat radiation aspect and the heat loss from the floor to the underground are measured and analyzed simultaneously. As a result, even if the supplied hot water temperature to the prefabricated Ondol panel is lower by about $5^{\circ}C$ than that of the conventional Ondol panel, the net radiant effect is same. Heat radiation efficiency of the prefabricated Ondol panel is over 5% better than that of the conventional Ondol panel. It takes 12 hours for the conventional Ondol and 45 minutes for the prefabricated Ondol, respectively to reach steady state.

• Medical Lasers
• /
• v.10 no.4
• /
• pp.214-219
• /
• 2021

Background and Objectives To evaluate the difference in near-infrared (810 nm) laser energy transmission through teeth with and without cracks. Materials and Methods Extracted teeth were sectioned and examined visually for the presence of cracks with the aid of photographs and a trans-illuminator. Fourteen sections, each with cracks (Group A) and no cracks (Group B) were identified and placed 15 mm from the tip of a 300 micron fiber, prior to activation with an 810 nm diode laser (0.1W, 50 ms interval,100 ms duration). A power meter positioned behind the tooth recorded the average energy that was transmitted through the samples. Unpaired t-test analysis was used to determine if the tooth sections with cracks allowed higher power passage compared to sound teeth. Results The mean power recording for the cracked teeth (Group A) was significantly greater (p = 0.0005) than that for the non-cracked teeth (Group B). Conclusion Within the limitations of this study, it is evident that significantly higher laser energy passes through teeth with cracks in comparison to teeth without cracks. A recent clinical study has also shown that lasers could be used to assess symptomatic cracked teeth. Hence, further research is required to determine the relative increase in energy required to identify symptomatic cracked teeth.