• Fire Science and Engineering
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• v.32 no.3
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• pp.76-87
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• 2018

This study describes the damage effects modeling for a quantitative prediction about the hazardous distances from pressurized chlorine saturated liquid tank, which has two-phase leakage. The heavy gas, chlorine is an accidental substance that is used as a raw material and intermediate in chemical plants. Based on the evaluation method for damage prediction and accident effects assessment models, the operating conditions were set as the standard conditions to reveal the optimal variables on an accident due to the leakage of a liquid chlorine storage vessel. A model of the atmospheric diffusion model, ALOHA (V5.4.4) developed by USEPA and NOAA, which is used for a risk assessment of Off-site Risk Assessment (ORA), was used. The Yeosu National Industrial Complex is designated as a model site, which manufactures and handles large quantities of chemical substances. Weather-related variables and process variables for each scenario need to be modelled to derive the characteristics of leakage accidents. The estimated levels of concern (LOC) were calculated based on the Gaussian diffusion model. As a result of ALOHA modeling, the hazardous distance due to chlorine diffusion increased with increasing air temperature and the wind speed decreased and the atmospheric stability was stabilized.

• Fashion & Textile Research Journal
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• v.10 no.6
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• pp.857-863
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• 2008

The purpose of this study is to analyze the types of Hibiscus patterns expressed on Aloha shirts. This study analyzed real data collected from man's aloha shirts displayed at the International Market Place in Waikiki of Hawaii during January 21-27, 2007. 35 pieces of Aloha shirts with Hibiscus Patterns were was analyzed. The total of each analysis means all number of patterns sampled or appeared to analyze the types of patterns. The motif of Hibiscus was sampled a total of 42 units for some shirts having several motifs. Its motif was divided into two groups, 20 units(47.62%) of natural type and 22 units(52.38%) of stylized type, according to modeling. Two types were much the same percentage. Hibiscus patterns were classified into three groups, isolated, band and arabesque type, by formation type. The isolated type was appeared most frequently. The layout of Hibiscus pattern was classified into three groups, engineered print, all over print and border print. All over print was appeared most frequently. The data of this study will be provided as a resource to promote using and developing of the pattern of Korean rose of Sharon.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.6
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• pp.1901-1913
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• 2014

The IEEE 802.15.6 is a communication standard for Wireless Body Area Networks (WBANs). This standard includes a prioritized slotted Aloha as a choice for medium access control. This protocol is different from the traditional version as it has integral considerations for certain priorities of users. It attempts to resolve collision by halving the probability of retransmission, lower bounded by to a minimum, in the alternate slots to follow. In this paper, we present an analytical model to compute the non-saturated throughput of this protocol in the presence of finite number of nodes. The model is validated against simulation.

• Korean Chemical Engineering Research
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• v.54 no.4
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• pp.582-585
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• 2016

This study intends to provide initial evacuation distances for the public in case of accidental releases of hydrogen fluoride (HF). HF is a very toxic chemical that is widely used in the chemical, electrical, and electronics industries. Consequence modeling programs, such as ALOHA and PHAST, were used to help formulate a contingency plan in case of an HF leak. For the purpose of this study, the release of entire quantity of HF in 10 min is defined as a worst-case scenario and the release from a partial line rupture is used as an alternative case scenario as National Institute of Chemical Safety (NICS) guidelines. Once the discharge rates were calculated based on the scenarios, the ERPG-2 endpoint distances have been obtained for representative daytime and nighttime weather conditions. This paper presents graphs that can be used to enact swift evacuation orders and emergency response plans in the case of accidental releases of HF.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.12A
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• pp.1852-1861
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• 1999

In this paper, CDMA Reservation ALOHA scheme which can reduce multiple access interference and packet collision is proposed to support multi-traffic such as voice and random data with and without priority. In this scheme, the time slot is divided into two stage, access and transmission stage. Only packets with spreading codes assigned from base station in access stage can transmit their packets in transmission stage, so MAI can be reduced. To reduce packer collision in access stage, the code reservation and access permission probability are used. Code reservation is allowed for voice traffic and continuous traffic with priority using piggyback and access permission probability based on the estimation of the number of contending users in the steady-state is adaptively applied to each traffic terminal. Also, we analyzed and simulated the numerical performances required for each traffic using Markov chain modeling in a single cell environment.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.4 no.2 s.7
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• pp.23-31
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• 2005

ITS(Intelligent Transportation System) implementing information collection services and information support services for cars of moving fast needs a communication system of special aim such as RF-DSRC(Radio Frequency Dedicated Short Range Communication). Before RSE(Road Side Equipment) and OBE(On-Board Equipment) will be able to communicate RF-DSRC, OBE first have to request Link Initialization Access using ACTC(Activation Channel) in allocated ACTS(Activation Slot) by Slotted ALOHA. Even though Link Initialization Access is a important element to decide performance of communication system, optimal mathematic modeling study of Link Initialization Access which is adapted RF-DSRC characteristics is not enoush. So, in this paper, we propose mathematical modeling about Link Initialization Access of RF-DSRC. And then we computed Link Initialization Access probability defining offer load(G) which is adapted RF-DSRC characteristics for analyzing performance of modeling.

• Journal of Industrial Technology
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• v.12
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• pp.37-49
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• 1992

We proposed an integrated simulator scheme for communication networks. The network modeling and Analysis methologies are firstly discussed along the design procedure of a network simulator, and then, the structure, kernel, and user interfaces are defined for the simulator. Finally, for the verification of our approach, simulations are performed for a simple queueing network and a pure ALOHA system using Ptolemy, a multi-paradigm simulation enviroment.

• Journal of the Korean Institute of Gas
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• v.22 no.2
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• pp.90-96
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• 2018

Design techniques for minimizing the damage caused by leakage of $H_2S$ gas, contained in natural gas and petroleum, have been widely studied abroad in chemical plants that purify and process natural gas and petroleum. However, there is no domestic engineering practice and regulation of $H_2S$. In accordance with the circumstances, this study proposes the quantitative criteria of process equipment to install $H_2S$ toxic gas detector as 500 ppm and explains the valid basis. The $H_2S$ gas dispersion radius up to IDLH 100 ppm is calculated by ALOHA under previous $H_2S$ gas leak accident scenario. The weather conditions of modeling include the conditions of Ulsan, Yeosu and Daesan, the three major petrochemical complexes in Korea. The long radius up to 100 ppm was derived in order of Ulsan, Daesan, Yeosu. For emergency safety the dispersion radius up to 100 ppm of the $H_2S$ gas obtained in this study should be extended to apply the additional $H_2S$ toxic gas detector, and local climate conditions should be considered.

• Journal of Korean Society of Disaster and Security
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• v.16 no.3
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• pp.1-15
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• 2023

This study focuses on modeling the impact of ammonia leakage from the storage tank in a combined cycle power plant's flue gas denitrification facility. It employs accident impact assessments and diffusion models to determine the optimal scenarios for ammonia storage tank leakage accidents. The study considers the operating conditions of variables as standard conditions for predicting the extent of damage. The Taean combined cycle power plant is chosen as the target area, taking into account seasonal factors such as temperature, humidity, wind speed, atmospheric stability, and wind direction. By utilizing a Gaussian diffusion model, the concentration of ammonia gas at various locations is estimated to assess the potential extent of external damage resulting from a leak. The study reveals that in conditions of high temperature and stable atmosphere within the specified range, lower wind speeds contribute to increased damage to the human body due to ammonia diffusion.

• Journal of the Korean Institute of Gas
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• v.26 no.4
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• pp.27-35
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• 2022

When LPG leaks from the storage tank, the gas try to sink to the ground because LPG is heavier than air. The gas easily creates vapor clouds causing aggressive accidents in no airflow. Therefore, It is important to prevent in advance by analyzing the damaged range caused from LPG leakage and vapor clouds. So, this study analyzed the range of damaged by LPG leakage and vapor clouds with consideration of the cold air flow which is generated by the topographical characteristics and the land use status at night time in the Jeju Hagari. As a result of the cold air flow using KLAM_21, about 2 m/s of cold air was introduced in from the southeast due to the influence of the terrain. The range of damaged by LPG leakage and vapor cloud was analyzed using ALOHA. When the leak hole size is 10 cm at the wind speed of 2 m/s, the range corresponding to LEL 60 % (12,600 ppm) was 61 m which range is expected to influence in nearby residential areas. These results of this study can be used as basic data to prepare preventive measures of accidents caused by vapor cloud. Forward, it is necessary to apply CFD modeling such as FLACS to check the vapor cloud formation due to LPG leakage in a relatively narrow area and to check the cause analysis.