• Transactions of the Korean Society of Mechanical Engineers B
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• 제35권2호
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• pp.205-213
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• 2011

The characteristics of noise generation in the suction nozzle of a vacuum cleaner are analyzed numerically and experimentally. First, the flow resistance induced by each element in the suction nozzle of a vacuum cleaner with a double-blade rotary fan is investigated numerically and its relation with flow-induced noise and suction performance is examined in an anechoic room. The flow resistance and vorticity in the suction nozzle are calculated, and it is found that they are closely related to flow-induced noise and that the upper limit of noise reduction is only 4 dBA. This upper limit can be achieved by changing the design of the brush nozzle. Two methods for noise reduction by enlargement of flow-inlet area and by optimization of the number of blades are tested. Finally, the effects of each method are verified experimentally.

• Fire Science and Engineering
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• 제33권4호
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• pp.83-88
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• 2019

This study examined the concentration of combustion gases while considering low ventilation and respiration frequency. A one-quarter-size ISO 9705 room corner test was performed. The concentrations of carbon monoxide and oxygen were measured in each case with the continuous inhalation of combustion gas with low ventilation (2, 6, and 10 LPM) and different respiration frequencies (2 s, 5 s, and infinity). The combustion of a gasoline pool fire in the compartment had a theoretical heat release rate of 5.34 kW. The results show that the deviation of the gas concentrations becomes higher as the low ventilation increases compared to the respiration frequency. In addition, as the respiration frequency increases, the variation in the minimum oxygen concentration is larger than the average value, while in the case of carbon monoxide, the variation in the average value is larger than the maximum value. These results show that the inhalation characteristics of refugees should be considered to investigate fires.

• Fire Science and Engineering
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• 제33권6호
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• pp.95-104
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• 2019

Smoke generated in a fire consists of gaseous substances and particulate matter, such as unburned carbon that adsorbed the gases. Human injury caused by inhalation of gaseous substances present in smoke is mostly short-term, whereas damage caused by inhalation of particulate matter is relatively a long-term phenomenon depending on the state of the gas-phase adsorption. The amount and location of the deposited smoke particles are important factors in estimating the damage caused to humans, which are affected by the breathing conditions as well as particle conditions, such as the size and concentration affected by the combustion conditions. In this study, in order to understand the characteristics of the deposition of smoke particles in the respiratory tract related to the study of human smoke inhalation injury, the number and mass concentration of smoke particles deposited in different areas of the respiratory tract for different fuel types, combustion conditions and breathing conditions were calculated. In addition, the amount of mass deposition of smoke in the respiratory tract for a certain period of inhalation was compared with the atmospheric standard of fine dust.

• Journal of Radiation Protection and Research
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• 제28권3호
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• pp.207-213
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• 2003

Carbon-14 is one of the major radionuclides released by CANDU Nuclear Power Plants(NPPs). It is almost always emitted as gas through the stack. From CANDU NPPs about 95% of all carbon-14 is released as carbon dioxide. Carbon-14 is a low energy beta emitter which, therefore, gives only a small skin dose from external radiation. As carbon dioxide Is physiologically rather inert gases for man's metabolism, the inhalation dose is probably less than 1 % of the ingestion dose. But this source of carbon-14, formed in a closed, nor-oxidative environment, was subsequently released into the workplace as an insoluble particulate when these systems were opened lip for re-tubing at CANDU NPPs. As a part of the improvement of dosimetry program at Wolsong Nuclear Power Plants, the carbon-14 metabolism based on references was investigated and studied to setup the internal dosimetry program due to inhalation of carbon-14.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 한국추진공학회 2009년도 제33회 추계학술대회논문집
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• pp.590-593
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• 2009

To identify the detailed 3D flow characteristics of a model scramjet engine, a unified 3D numerical analysis was performed. The numerical domain of concern includes the entire flow path of the model scramjet engine extending from the intake to the nozzle exhaust. Turbulent models($k-{\omega}$ SST and low Reynolds number k-e with Sarkar model) were applied with comparison of experiment result. Intake side wall's effect on flow characteristics was analyzed in view points of flow quality at inlet duct and near the flame holder as well. The code is paralleled with multi-block feature using MPI(Massage Passing Interface) library to speed up the 3D calculation.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• 제38권11호
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• pp.1067-1074
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• 2010

In this study, RBDO(Reliability Based Design Optimization) was performed for a supersonic double-wedge inlet. By considering uncertainty of design with given design space, the pressure recovery was transformed into the probabilistic constraint while the inlet drag was considered as a deterministic objective function. To save computational analysis cost and to search good design space, Latin-Hypercube design of experiment and the Kriging model were incorporated and then RBDO was performed. Monte-Carlo simulation was performed to verify the accuracy of AFORM(Advanced First Order Reliability Method). It was found that AFORM result agreed very well with the Monte-Carlo simulation result. The system reliability was guaranteed by considering uncertainty of the design variables. In case of considering diverse uncertainty of system design, RBDO was found to be useful.

• Journal of Radiation Protection and Research
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• 제31권3호
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• pp.135-140
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• 2006

Intakes of radionuclides through both inhalation and ingestion pathways may occur particularly in an incident involving unsealed radionuclides. If one assume only one intake path in this case, which is usual in routine monitoring, a significant error in the evaluated committed effective dose($E_{50}$) may result. In order to demonstrate the potential errors, variations of the resulting committed effective doses were analyzed for different fractions of the inhaled activities to the total intake of $^{241}Am$. Simulated bioassav measurements for the lungs, urine and feces were generated based on the biokinetic model and data of the radionuclide, 5 ${\mu}m$ AMAD and absorption type M for inhalation, for various inhalation fractions. The potential errors in $E_{50}$ due to the assumption of one intake path were in the range from -100% to as large as +34,000% when the bioassays were made 3 days after the intakes. Larger errors are expected when only the feces assay is applied while inhalation intake exists. A strategy which employs two types of bioassay was proposed to reduce the error caused by a misjudgement of the intake path.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 한국소음진동공학회 2014년도 춘계학술대회 논문집
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• pp.250-251
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• 2014

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 한국소음진동공학회 2014년도 춘계학술대회 논문집
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• pp.244-245
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• 2014

• Proceedings of the Korean Society of Precision Engineering Conference
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• 한국정밀공학회 2009년도 추계학술대회 논문집
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• pp.231-232
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• 2009