• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.202-207
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• 2006

The aeroacoustic noise from intake head of a vacuum cleaner is caused by complicated transient pressure fluctuation and it greatly affects the overall SPL of the vacuum cleaner. In this study, we intended to decrease the overall SPL by reducing the aeroacoustic noise from intake head. In the first the place, we analyzed the aeroacoustic noise from the unsteady fluid analysis of intake head. And then, we grasped the dominant frequency band from the aeroacoustic noise by comparing the spectrum distributions between examinations and analyses. Also, we systematically investigated the aeroacoustic noise sources from each part composing the intake head. Consequently, we redesigned each part of the dominant noise sources and suggested the modified intake head, resulting in the reduction ortho overall SPL by 3.6dB(A).

• Journal of Mechanical Science and Technology
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• v.19 no.3
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• pp.894-904
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• 2005

The flow structure inside the intake head greatly affects the working efficiency of a vacuum cleaner such as suction power and aero-acoustic noise. In this study, the flow inside intake heads of a vacuum cleaner was investigated using qualitative flow visualization and quantitative PIV (Particle Image Velocimetry) techniques. The aerodynamic power, suction efficiency and noise level of the intake heads were also measured. In order to improve the performance of the vacuum cleaner, inner structure of the flow paths of the intake head, such as trench height and shape of connection chamber were modified. The flow structures of modified intake heads were compared with that of the original intake head. The aero-acoustic noise caused by flow separation was reduced and the suction efficiency was also changed due to flow path modification of intake head. In this paper, the variations of flow fields for different intake heads are presented and discussed together with results of aerodynamic power, suction efficiency and noise level.

• Journal of computational fluids engineering
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• v.4 no.3
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• pp.21-27
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• 1999

In this paper, tile characteristics of flow resulting from the configurations of piston head and intake-port of the cylinder in a gasoline-direct-injection engine are investigated numerically. Calculations are carried out from intake process to the end of compression. GTT code which includes the third order upwind Chakravarthy-Osher TVD scheme and κ-ε turbulence model with the law of wall as a boundary condition. As a result, a piston head with a smaller radius of curvature and larger radius gives stronger reverse tumble. It is also shown that as the maximum tumble ratio increases by the configuration of the intake-port the tumble ratio at the end of compression stroke increases. It is concluded that flows at the end of compression stroke can be controlled by the optimum design of intake-port and piston head.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.6
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• pp.880-885
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• 2000

Flow patterns and steady flow characteristics of an intake 3valve cylinder head are not obviously declared. Thus, in the study, the characteristics and limitation of intake flow coefficient which applied to multi intake valve engine are introduced. The flow coefficient and tumble characteristics are investigated by means of the steady flow test and flow visualization method. As the results, it is found that the intake flow rate is dominated by effective valve open area. In addition, this paper shows that the mass flow rate of intake 3valve engine is greater than that of intake 2valve engine and tumble flow of intake 3valve engine is superior to that of intake 2valve engine.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.1
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• pp.59-72
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• 1998

This experimental study was carried out to investigate the characteristics of the in-cylinder eccentricity swirl flow generated by a 4 valve cylinder head with a tangential and a helical intake port. the measurements of the in-cylinder velocity field have been made by a two-channel LDA system. The mean flow coefficient(Cf(meam)), swirl ratio(Rs) and mass flowrate with valve eccentricity ratios and an intake port partition between the two intake ports were measured in the steady flow test fig using the ISM(impulse swirl meter). The experimental results indicated that the mass flowrate through the tangential intake port was 19% and 7.7% more than that of the helical intake port in case of with and without intake port partition respectively. There was a tendency to be a single rotation flow in swirl flow fields formed by a 4 valve cylinder head because of the interaction between the two intake ports. As the intake port partition was not set between flow coefficient(Cf(mean)) was 7.35%.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.1
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• pp.129-137
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• 2006

This paper studies the effects of the swirl for the variation of intake port configuration that is key parameters in the flow field of direct injection diesel engines. In-cylinder flow characteristics is known to have significant effects on air-fuel mixing, combustion, and emissions. To investigate the effects of the swirl flow, various rpm(250, 500, 750) and two different intake port were used. And to evaluate the swirl motion in the flow field visualization engine, steady state flow test was conducted. Helical port intake port and SCV(Swirl Control Valve) were selected as the design parameters to increase the swirl flow and parametric study was performed. In the case of non-SCV, intake flow rate and non-dimensional swirl ratio were higher than those of SCV for the swirl head type. So, we could strengthen the swirl in the flow field with the swirl head type and don't using SCV. From the results of steady state flow test, non-swirl head type has the most good advantage for intake flow rate, and also the flow rate could be increased by using the SCV slightly. The effects of the type of engine head on intake air flow capability are dominant with respect to the existence of the SCV. We could measure the qualitative grade of swirl by capturing the scattering signal of microballoon from ICCD camera in the visualization diesel engine.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.13 no.1
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• pp.18-22
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• 2002

Background and Objectives : It has been pointed out that alcohol intake in human beings induces changes in voice register and maximum phonation time. These changes supposedly result from injection of the vibratory vocal folds. The purpose of this study was to clarify the voice changes associated with alcohol intake and the changes of laryngeal mucosa. Materials and Methods : The subjects included 29 volunteers, including 20 men and 9 women ranging in age from 22 to 31 years. Alcohol intake was accomplished by oral administration of 23% soju 1 bottle (255cc). Serum alcohol concentration levels were evaluated hourly for 3 h after ingestion of alcohol. Seven measurements were performed at pre-alcohol intake and post-alcohol intake hourly : fundamental frequency, jitter, shimmer, noise to harmonic ratio as the acoustic analysis, maximal phonation time, mean flow rate, and subglottal pressure as the aerodynamic analysis. The changes of laryngeal mucosa were evaluated by flexible laryngoscope at each measurement. Results : By comparing the acoustic and aerodynamic data and laryngeal mucosa before and after alcohol intake, there were not remarkable changes (p>0.05). Conclusion : The voice and laryngeal mucosa have not remarkably changed according to alcohol concentration in this study. Furthermore studies on the voice change induced by multiple alcohol concentrations are required.

• Korean Journal of Head & Neck Oncology
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• v.17 no.2
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• pp.131-138
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• 2001

Objectives: Alcohol intake has been reported to be a risk factor of laryngeal cancer. Since the aldehyde dehydrogenase 2 (ALDH2) genotype is a major determinant of personal alcohol drinking habit, there is a possibility that ALDH2 genotype would be a risk factor for laryngeal cancer. N-Acetyltransferase 2 (NAT2) is a detoxifying enzyme and its polymorphism has been reported to be related to the risk of many environmental cancers. However, studies on the associations between these two genotypes and laryngeal cancer risk are scarce. We have assessed the effects of alcohol intake and the genotype of ALDH2 and NAT2 on the risk of laryngeal cancer in Koreans. Materials and Methods: Eighty-four pathologically proven laryngeal cancer patients and 168 age matched controls were included as the study subjects. Information about alcohol intake and smoking habit was collected using a self administered questionnaire. ALDH2 and NAT2 genotypes were analyzed using PCR-RFLP methods. Results: Alcohol intake was significant as a risk factor for laryngeal cancer (OR : 2.58, 95% CI : 1.24, 5.36), especially for supraglottic laryngeal cancer (OR : 3.24, 95% CI : 1.02, 10.31). Personal drinking habit was closely related with personal smoking habit, which was a potent risk factor of laryngeal cancer. In a stratified analysis according to the level of cumulative smoking amount, drinking was significant neither in light smokers (equal or less than 30 pack-years) nor in heavy smoker (over 30 pack-years). The ALDH2 genotype was significantly associated with the risk of laryngeal cancer in a univariate analysis. The statistical significance, however, disappeared after adjusting alcohol intake using a multiple conditional logistic model. The NAT2 genotype was not significant as a risk factor for laryngeal cancer. Conclusion: Alcohol drinking and ALDH2 genotype would have indirect effects on laryngeal cancer by their correlations with cigarette smoking or with alcohol drinking. It is less likely that the NAT2 genotype would be a potent risk factor of laryngeal cancer.

• Asian-Australasian Journal of Animal Sciences
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• v.14 no.10
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• pp.1383-1388
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• 2001

To explore the factors restricting animal performance in relation to sward structure under a strip-grazing system, measurements of sward factors, herbage intake and milk production at 3 levels of herbage allowance were made on perennial ryegrass (Latium perenne L.) sward for 3 experimental periods. About 29%, 36% and 52% of the biomass offered was removed by grazing in high $(42kg\;OM{\cdot}day^{-1}{\cdot}head^{-1})$, medium $(30kg\;OM{\cdot}day^{-1}{\cdot}head^{-1})$ and low $(18kg\;OM{\cdot}day^{-1}{\cdot}head^{-1})$ herbage allowance plots. Live leaf material was much more affected by grazing under different herbage allowance levels than dead material or leaf sheath. Grazing with a low herbage allowance decreased the proportion of live lamina by 93% and live lamina density by 96% before grazing. The density of dead material plus sheath was decreased by 17% after grazing at a low allowance, while it slightly increased or remained constant in the plots applied with high and medium allowances, respectively. The highly significant (p<0.01) correlations between herbage allowance and proportion (r=0.94) and density (r=0.91) of live lamina in residual sward after grazing were observed. Daily herbage intakes in the plots with high and medium levels of herbage allowance were not significantly different at $15.3kg\;OM{\cdot}head^{-1}$ in average, whereas with low level it decreased to $13.9kg\;OM{\cdot}head^{-1}$. Daily milk production was significantly (p<0.05) declined from $22.3kg{\cdot}head^{-1}$ (at high herbage allowance) to $19.7kg{\cdot}head^{-1}$ (at low herbage allowance). The data obtained clearly indicated that herbage intake and milk production were highly affected by the characteristics of residual sward, which were closely related to the level of herbage allowance.

• Journal of the Korean Society of Safety
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• v.25 no.6
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• pp.22-27
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• 2010

Flow Coefficients of intake port in an engine cylinder head were measured by a newly designed flow rig. In measuring the flow coefficient with traditional method, the valve lift was manually varied by technician with adjusting a micrometer which is directly connected to the intake valve of the cylinder head. The cam shaft of the cylinder head is directly rotated by a step motor and the valve lift was automatically varied with cam shaft profile in the newly designed flow rig. The measurement of the flow coefficient was automated by rotating the cam shaft with the step motor. Automatic measurement of the flow coefficient could be safely measured by separating a technician from the noise and vibration of the traditional flow rig. Also, the automatic measurement of the flow coefficient reduce the measurement time and provide meaningful statistical data.