• Fire Science and Engineering
• /
• v.33 no.6
• /
• pp.1-8
• /
• 2019

In this study, the effects of the characteristics of droplets of water spray on suppression of fire were analyzed numerically using fire dynamics simulator (FDS) 6.5.2. Additionally, the fire suppression characteristics by the water spray nozzle, including the extinguishing coefficient (EC), droplet size distribution function (SDF), median volumetric diameter (MVD), and droplets per second (DPS), were evaluated in terms of the decreasing normalized heat release rate (HRR) curve and cooling time. It was observed that with increase in the EC, the normalized HRR curve decreased rapidly, and the changing MVD affected the suppression of fire. In case of mono-disperse, the normalized HRR curve decreased slowly with the increase in DPS. On the contrary, in case of multi-disperse, the normalized HRR curve decreased rapidly even with a small increase in DPS.

• Fire Science and Engineering
• /
• v.26 no.6
• /
• pp.51-56
• /
• 2012

The onset of fire on the International Space Station (ISS) is a critical problem that can threaten the life of crew members onboard and thus instantaneous fire detection and extinguishment technology has been considered as one of the most important aspects in the ISS operation. In the present study, a numerical analysis was performed to better understanding of the characteristics of smoke behaviors and detection in a pressurized module of the ISS using the NIST Fire Dynamic Simulator (FDS). Numerical results indicate that the smoke flow patterns under zero-gravity condition are clearly different from those under normal gravity condition. In addition, the results obtained from numerical simulations coupled with the PM internal flows are expected to provide basic and useful information in designing the microgravity fire detection devices and establishing in fire response protocol for astronauts or the crew members.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.25 no.6
• /
• pp.1525-1540
• /
• 2015

Due to a rapid advancement in the electronic commerce technology, the payment method varies from cash to electronic settlement such as credit card, mobile payment and mobile application card. Therefore, financial fraud is increasing notably for a purpose of personal gain. In response, financial companies are building the FDS (Fraud Detection System) to protect consumers from fraudulent transactions. The one of the goals of FDS is identifying the fraudulent transaction with high accuracy by analyzing transaction data and personal information in real-time. Data mining techniques are providing great aid in financial accounting fraud detection, so it have been applied most extensively to provide primary solutions to the problems. In this paper, we try to provide an overview of the research on data mining based fraud detection. Also, we classify researches under few criteria such as data set, data mining algorithm and viewpoint of research.

• Fire Science and Engineering
• /
• v.27 no.6
• /
• pp.64-69
• /
• 2013

The Numerical simulation was performed on the flow field around the two-dimensional rectangular bluff body in order to simulate an engine nacelle fire and to complement the previous experimental results of the bluff body stabilized flames. Fire Dynamic Simulator (FDS) based on the Direct Numerical Simulation (DNS) was employed to clarify the characteristics of reacting flow around bluff body. The overall reaction was considered and the constant for reaction was determined from flame extinction limits of experimental results. The air used atmosphere and the fuel used methane. For both fuel ejection configurations against an oxidizer stream, the flame stability and flame mode were affected mainly by vortex structure near bluff body. In the coflow configuration, air velocity at the flame extinction limit are increased with fuel velocity, which is comparable to the experiment results. Comparing with the isothermal flow field, the reacting flow produces a weak and small recirculation zone, which is result in the reductions of density and momentum due to temperature increase by reaction in the wake zone.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.34 no.6
• /
• pp.18-28
• /
• 2006

Numerical analysis of high Mach number flow over a blunt-body poses many difficulties and various numerical schemes have been suggested to overcome the problems. However, the new schemes were used in the limited fields of applications because of the lack of field experience compared to more than 20 years old numerical schemes and the intricacies of modifying the existing code for the special application. In this study, some tips to overcome the numerical difficulties in solving the 3D high-Mach number flows by using Roe's scheme, the most widely used for the past 25 years and adopted in many commercial codes, were examined without a correction of the algorithm or a modification of the CFD code. The well-known carbuncle phenomena of Riemann solvers could be remedied even for an extremely high Mach number by applying the entropy fixing function and a unphysical solution could be overcome by applying a simply modified initial condition regardless of the entropy fixing and grid configuration.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.26 no.6
• /
• pp.1513-1526
• /
• 2016

Since finance companies started e-banking services, those services have been diversified and use of them has continued to increase. Finance companies are implementing financial security policy for safe e-banking services, but e-Banking incidents are continuing to increase and becoming more intelligent. Along with the rise of internet banks and boosting Fintech industry, financial supervisory institutes are not only promoting user convenience through improving e-banking regulations such as enforcing Non-face-to-face real name verification policy and abrogating mandatory use of public key certificate or OTP(One time Password) for e-banking transactions, but also recommending the prevention of illegal money transfer incidents through upgrading FDS(Fraud Detection System). In this study, we assessed a blacklist based auto detection method suitable for overall situations for finance company, a real-time based suspicious transaction detection method linking with blacklist statistics model by each security level, and an alternative FDS model responding to typical transaction patterns of which information were collected from previous e-Banking incidents.

• Journal of the Korean Society of Safety
• /
• v.22 no.4
• /
• pp.1-6
• /
• 2007

In this study, we provided an index for the quantitative and systematic performance based fire risk assessment. A complex cinema was adopted for the fire scenario and the fire simulation was carried out by using FDS. Also evacuation time was calculated by using SIMULEX. We obtained a big different fire risk assessment result by the focus on the between space basis and the time basis. As a result of this study, performance based fire risk assessment should be performed on the basis of individual evacuee's path line.

• Journal of the Korean Society for Railway
• /
• v.9 no.6 s.37
• /
• pp.625-629
• /
• 2006

This paper describes the effect of the droplet breakup process on fire suppression using a water-mist system, which is considered as a alternative to sprinkler fire suppression system. In the evolution of the water-mist, the droplet breakup process is an important phenomenon because it may significantly affect the droplet evaporation rate. The Fire Dynamics Simulator (FDS, Ver. 4.0) code, which is widely used for the simulation of fire dynamics, is used for the present simulation, and it is modified to consider the droplet breakup phenomena. The Prediction by the modified code shows good agreement with experimental data for the temperature. The original FDS predicts higher temperature about $30^{\circ}C$ than experimental data. From the results, it is concluded that the droplet breakup phenomena must be considered for more precise simulation of fire suppression process.

• Journal of the Korean Society of Safety
• /
• v.23 no.5
• /
• pp.1-6
• /
• 2008

`SOS', Simulator Of Safety assessment for fire, was developed to simulate fire safety assessment for a structure which is geometrically complex. The program(SOS) is intended to use for searching as well as designing tools to analyse the evacuation safety through a wide range of structure conditions. The computer program has a function which importing FDS's calculating results to each individual resident in the structure. These attributes include a walking speed reduction by producing visibility reduction for each person on the fire. $A^*$ pathfinding algorithm is adopted to calculate the simulation of escape movement, overtaking, route deviation, and adjustments individual speeds in accordance with the proximity of crowd members. This SOS program contributes to a computer package that evaluates the fire safety assessment of individual occupants as they walk towards, and through the exits especially for building, underground spaces like a subway or tunnel.

• Nuclear Engineering and Technology
• /
• v.53 no.4
• /
• pp.1157-1166
• /
• 2021

In this study, a numerical sensitivity analysis was performed to determine the fire suppression time for a large number of water mist nozzles in a large fire compartment. Fire simulations were performed using FDS (Fire dynamics simulator) 6.5.2 under the same condition as the test scenario 5 of the International Maritime Organization (IMO) 1165 test protocol. The sensitivities of input parameters including cell size, extinguishing coefficient (EC), droplets per second (DPS), and peak heat release rate (HRR) of fuel were investigated in terms of the normalized HRR and temperature distribution in the compartment. A new method of determining the fire suppression time using FDS simulation was developed, based on the concept of the cut-off time by cut-off value (COV) of the heat release rate per unit volume (HRRPUV) and the cooling time by the HRR cooling time criteria value (CTCV). In addition, a method was developed to determine the average EC value for the simulation input, using the cooling time and cut-off time.