• Fire Science and Engineering
• /
• v.23 no.5
• /
• pp.110-116
• /
• 2009

This study is related with fire risk assessment for fire and smoke spread of double skin facade system by use of FDS (Fire Dynamics Simulator) which is a computational fluid dynamics (CFD) model of fire-driven fluid flow. For the study, fire scenario is intended to evaluate the impact of a fire spread for glazed office building. The major purpose of this study is to analyze the fire risk depending on the width of between inner skin and outer skin and to present fire prevention method regarding double skin facade system. The result of analysis presents fire spread more vertically as intermediate space becomes narrow. It is anticipated that fire can spread upper 2 stories above the fire floor if intermediate space with not more than 1m width. Therefore, prevention of vertical fire spread is required.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.9 no.1
• /
• pp.42-48
• /
• 2010

In this paper, we proposed analysis performance improvement technique for T-DMB watermarking based on MBOK spread spectrum. By applying the proposed scheme to T-DMB system, it allows additional data transmission and improves spectral efficiency of data transmission through watermarking spreading code. Using MBOK spread spectrum technique, data rate improved 2m-times existing direct sequence spread spectrum. However, since hardware complexity increase as the value of m becomes large, the method should be used with optimal situation. We analyze T-DMB watermarking techniques performance with MBOK spread spectrum and averaging. As a result, we confirm DER performance of MBOK spread spectrum scheme and it is shown system performance is improved as the number of averaging increases. The results of the paper can be applied to wireless multimedia digital broadcasting system.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
• /
• v.5 no.4
• /
• pp.47-63
• /
• 1994

An important parameter in characterizing mobile communication channel is delay spread. This paper presents the results of measured delay profiles and calculated distribution funcations of delay spread for typical cellular service environments at Taejon and vicinities. The measurement system uses 1023 chip length, 5 Mbps PN code and sliding correlation method. It has been evaluated by using commercial hardware channel simulator for reliability of out data. As results the value of mean delay spread is 2.08 $\mu\textrm{s}$for suburban area. 2.12 $\mu\textrm{s}$ for urban area and 1.3 $\mu\textrm{s}$ for national/local road. Delay spread is less then 3.4$\mu\textrm{s}$, 2.8$\mu\textrm{s}$ and 1.5 $\mu\textrm{s}$ for probability of 50% and 4.5$\mu\textrm{s}$, 4.2$\mu\textrm{s}$ and 2.9$\mu\textrm{s}$ for probability of 90% at each tested site. The difference of delay spread is within 7% between going and returning status along same street. In this experiment, we found delay spread for suburban area is larger than reported foreign test results.

• The Korean Journal of Pain
• /
• v.20 no.1
• /
• pp.46-49
• /
• 2007

Background: Cervical epidural injection, performed via the interlaminar approach, represents a useful interventional pain management procedure indicated in patients with a cervical herniated disk. Due to thedecreased epidural space in the cervical region, cervical epidural injections may result in potentially serious complications, especially during a large volume injection. Methods: Thirty-four patients with neck pain due to a cervical herniated disk that were referred to the pain clinic for cervical epidural steroid injection were randomized into two groups. One group received a cervical epidural injection of 4 ml drug and the other group received 2 ml drug. The injected mixture included triamcinolon, ropivacaine and omnipaque. Spread levels of the drug after injection were estimated with the use of C-arm fluoroscopy. Results: Spread levels to the cephalad for patients in the two groups were $4.88{\pm}0.78segments$ and $4.53{\pm}0.49segments$, respectively. Spread levels to the caudad for patients in the two groups were $4.59{\pm}0.93segments$ and $4.47{\pm}0.51segments$, respectively. The results showed no significant difference in the spread level between the two groups. Conclusions: Use of a small volume of drug (2 ml) can provide a sufficient spread level of the injected drug that is desirable for patients with a cervical herniated disk.

• Journal of the Korean Society of Safety
• /
• v.34 no.5
• /
• pp.15-21
• /
• 2019

A rack-type warehouse has the advantage of storing a large amount in a small area by loading goods vertically. But in terms of fire risk, the fire load is very high, which can cause massive damage in the event of a fire. In the United States, research has been actively conducted to minimize the spread of vertical fires, and relevant standards have been established and operated. In Korea, research and related standards are insufficient to prevent the vertical spread of rack-type warehouse fires. In this study, an experimental study was conducted to prevent the vertical spread of a rack-type warehouse fire using a horizontal barrier and in-rack sprinklers. As a result of the test, the horizontal barrier considering the continuous flame prevented the vertical spread of the flame for a certain time. However, the horizontal barrier with continuous flame did not show the effect of preventing continuous flame. The combination of the horizontal barrier and the in-rack sprinkler prevented the vertical spread of fire effectively. In addition, the heat collecting effect through the horizontal barrier was shown and helped the early operation of the in-rack sprinklers.

• The Journal of the Acoustical Society of Korea
• /
• v.42 no.3
• /
• pp.169-180
• /
• 2023

The performance of underwater acoustic communication is greatly affected by multipath propagation and Doppler spread. This paper proposes a new communication technique, the Triangle Spread Carrier (TSC) technique, by modifying the existing Sweep Spread Carrier (SSC) technique that is strong in a multipath propagation environment. The proposed TSC technique is a form in which the up-chirp and down-chirp signals have repeated carriers, and each correlation function characteristic is used to estimate and correct the Doppler shift frequency of the receiving signal. To demonstrate the performance of the proposed TSC technique, we present the results of simulations using underwater channel simulators and sea trial conducted in the East Sea. When demodulating using only the estimated Doppler shift frequency as a result of the sea trial, the uncoded bit error rate was up to 0.194, but when the proposed method was applied, the uncoded bit error rate was reduced to 0.001.

• The Journal of the Acoustical Society of Korea
• /
• v.41 no.2
• /
• pp.184-191
• /
• 2022

Underwater acoustic wave in shallow water is propagated through multipath that has a large delay spread causing Inter-Symbol Interference (ISI) and these characteristics deteriorate the performance in the communication system. In order to analyze the communication performance and investigate the correlation with multipath delay spread in a reverberant environment, an underwater acoustic communication experiment using Binary Phase-Shift Keying (BPSK) signals with symbol rates from 100 sym/s to 8000 sym/s was conducted in a 5 × 5 × 5 m³ water tank. The acoustic channels in a well-controlled tank environment had the characteristics of dense multipath delay spread due to multiple reflections from the interfaces and walls within the tank and showed the maximum excess delay of 40 ms or less, and the Root Mean Squared (RMS) delay spread of 8 ms or less. In this paper, the performances of Bit Error Rate (BER) and output Signal-to-Noise Ratio (SNR) were analyzed using four types of communication demodulation techniques. And the parameter, Symbol interval to Delay spread Ratio in reverberant environment (SDR_rev), which is the ratio of symbol interval to RMS delay spread in the reverberant environment is defined. Finally, the SDR_rev was compared to the BER and the output SNR. The results present the reference symbol rate in which high communication performance can be guaranteed.

• Journal of Sasang Constitutional Medicine
• /
• v.18 no.2
• /
• pp.50-54
• /
• 2006

1. Objectives The purpose of this study was to investigate the spread of Sasang constitution in $4{\sim}6$ years old. 2. Methods The voices of 529 children in $4{\sim}6$ years old were analyzed with PSSC-2004. and the result of the spread of Sasang constitution was examined. 3. Results (1) Group of total was composed with 276 boys and 253 girls. In total group, it was composed with 269 Soeumins, 32 Soyangins, and 228 Taeumins. (2) The spread of Sasang constitution according to age was composed with 72 Soeumins, 5 Soyangins, and 59 Taeumins in 4 years old. It was composed with 154 Soeumins, 17 Soyangins, and 131 Taeumins, In 5 years old. It was composed W with 43 Soeumins, 10 Soyangins, and 38 Taeumins, In 6 years old. 4. Conclusions From above result, wε observed the spread of Sasang constitution in $4{\sim}6$ years old. there is a necessary to study the spread of Sasang constitution specifically according to the age at which one's voice changes, and to conduct follow-up survey of the a age at the same child's voice changes.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.14 no.7
• /
• pp.3482-3486
• /
• 2013

In the case of the Pilot Symbol Assisted Modulation (PSAM) method predicting and compensating amplitude and phases caused on fading channels, there can be severe performance deterioration by Doppler spread on fast fading channels. In this paper, the fading compensation method suggested so as to improve occurring problems as well as analyze them. Doppler spread is the major cause of the bit error rate(BER) performance deterioration. Compared to the existing PSAM method, the more performance deterioration occurs, the larger Doppler spread appears but performance shows well its less $10^{-2}BER$ performance than the existing PSAM method in the suggested method whereas the existing PSAM method has about $10^{-1}BER$ its considerable performance deterioration that caused by Doppler spread within a symbol cycle with the level of delay wave interference.

• Journal of IKEEE
• /
• v.15 no.1
• /
• pp.23-28
• /
• 2011

This paper describes design and implementation of a spread spectrum clock generator(SSCG). The proposed architecture generates the spread spectrum clock controlling a input voltage signal for VCDL(Voltage Controlled Delay Line). Spread charge pump is controlled by the SSC modulation logic block provides a control signal to VCDL through LPF in DLL. By using this architecture, chip area and power consumption can be reduced because it is not necessary additional circuit to control modulation rate. This circuit has been designed and fabricated using the UMC 0.25um CMOS technology. The chip occupies an area of 290${\times}$120um^2.