• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.8
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• pp.1972-1981
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• 1995

As a railway train enters a tunnel at high speed, a compression wave is formed in front of the train and propagates along the tunnel. The compression wave subsequently emerges from the exit of the tunnel, which causes an impulsive noise. The impulsive noise is closely related to the pressure gradient of the compression wave propagating the tunnel. In order to investigate the characteristics of the compression waves, in the present study an experiment was made using a shock tube. The results show that the strength of a compression wave decreases with the distance from the tunnel entrance and the nonlinear effect of compression wave appears to be significant if strength of the initial compression wave is greater than 7 kPa. Furthermore if the wave pattern is known, attenuation of the compression wave propagating in a tunnel can be reasonably predicted by a theoretical equation considering viscous action and heat transfer in boundary layer.

• Tuberculosis and Respiratory Diseases
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• v.65 no.6
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• pp.457-463
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• 2008

Background: The attenuation of the lung parenchyma increases on expiration as a consequence of decreased air in the lung. Expiratory CT scans have been used to show air trapping in patients with chronic airway disease and diffuse parenchymal disease and also in asymptomatic smokers. Although there have been several reports investigating the regional air trapping on a expiratory CT scan, there have been only a few reports evaluating the changes of whole lung attenuation with considering its clinical significance, and especially in healthy subjects. The purpose of this study was to evaluate the correlation of an expiratory increase of lung attenuation with age and smoking in healthy subjects. Methods: Asymptomatic subjects who underwent a low dose chest CT scan as part of a routine check-up and who showed normal spirometry and a normal inspiratory CT scan were recruited for this study. We excluded the subjects with significant regional air trapping seen on their expiratory CT scan. Lung attenuation was measured at 24 points of both the inspiratory and expiratory CT scans, respectively, for 100 subjects. The correlations between an expiratory increase of the lung attenuation and the amount of smoking, the patient's age and the results of spirometric test were assessed. Results: There were 87 men and 13 women included in this study. Their median age was 49.0 years old (range:25~71). Sixty current smokers, 24 ex-smokers and 16 non-smokers were included. As age increased, the expiratory increase of lung attenuation was reduced at every measuring points (r=-0.297~-0.487, Pearson correlation). The statistical significance was maintained after controlling for the effect of smoking. Smoking was associated with a reduction of the expiratory increase of lung attenuation. But the significance was reduced after controlling for the patient's age. The $FEV_1$, FVC, $FEV_1/FVC$ and $FEF_{25{\sim}75%}$ were not associated with an expiratory increase of lung attenuation. Conclusion: The expiratory increase of lung attenuation in subjects with a normal inspiratory CT scan was negatively correlated with age. It was also reduced in heavy smokers. It may reflect aging and the smoking related changes.

• The Korean Journal of Pain
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• v.27 no.2
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• pp.145-151
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• 2014

Background: The physician's hands are close to the X-ray field in C-arm fluoroscopy-guided pain interventions. We prospectively investigated the radiation attenuation of Proguard RR-2 gloves. Methods: In 100 cases, the effective doses (EDs) of two dosimeters without a radiation-reducing glove were collected. EDs from the two dosimeters-one dosimeter wrapped with a glove and the other dosimeter without a glove-were also measured at the side of the table (Group 1, 140 cases) and at a location 20 cm away from the side of the table (Group 2, 120 cases). Mean differences such as age, height, weight, radiation absorbed dose (RAD), exposure time, ED, and ratio of EDs were analyzed. Results: In the EDs of two dosimeters without gloves, there were no significant differences ($39.0{\pm}36.3{\mu}Sv$ vs. $38.8{\pm}36.4{\mu}Sv$) (P = 0.578). The RAD ($192.0{\pm}182.0radcm^2$) in Group 2 was higher than that ($132.3{\pm}103.5radcm^2$) in Group 1 (P = 0.002). The ED ($33.3{\pm}30.9{\mu}Sv$) of the dosimeter without a glove in Group 1 was higher than that ($12.3{\pm}8.8{\mu}Sv$) in Group 2 (P < 0.001). The ED ($24.4{\pm}22.4{\mu}Sv$) of the dosimeter wrapped with a glove in Group 1 was higher than that ($9.2{\pm}6.8{\mu}Sv$) in Group 2 (P < 0.001). No significant differences were noted in the ratio of EDs ($73.5{\pm}6.7%$ vs. $74.2{\pm}9.3%$, P = 0.469) between Group 1 and Group 2. Conclusions: Proguard RR-2 gloves have a radiation attenuation effect of 25.8-26.5%. The radiation attenuation is not significantly different by intensity of scatter radiation or the different RADs of C-arm fluoroscopy.

• Journal of Radiopharmaceuticals and Molecular Probes
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• v.1 no.2
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• pp.130-136
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• 2015

We evaluate the influence of MR contrast agent on positron emission tomography (PET) image using phantom, animal and human studies. Phantom consisted of 15 solutions with the mixture of various concentrations of Gd-based MR contrast agent and fixed activity of [$^{18}F$]FDG. Animal study was performed using rabbit and two kinds of MR contrast agents. After injecting contrast agent, CT or MRI scanning was performed at 1, 2, 5, 10, and 20 minutes. PET image was obtained using clinical PET/CT scan, and attenuation correction was performed using the all CT images. The values of HU, PET activity and MRI intensity were obtained from ROIs in each phantom and organ regions. In clinical study, patients (n=20) with breast cancer underwent sequential acquisitions of early [$^{18}F$]FDG PET/CT, MRI and delayed PET/CT. In phantom study, as the concentration increased, the CT attenuation and PET activity also increased. However, there was no relationship between the PET activity and the concentration in the clinical dose range of contrast agent. In animal study, change of PET activity was not significant at all time point of CT scan both MR contrast agents. There was no significant change of HU between early and delayed CT, except for kidney. Early and delayed SUV in tumor and liver showed significant increase and decrease, respectively (P<0.05). Under the condition of most clinical study (< 0.2 mM), MR contrast agent did not influence on PET image quantitation.

• Journal of Veterinary Clinics
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• v.38 no.3
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• pp.135-142
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• 2021

The aim of this study was to evaluate the contrast effect if a saline flush following low-volume contrast medium bolus improves vascular and parenchymal enhancement using a saphenous vein in abdominal CT for small animals. Six clinically healthy beagle dogs underwent abdominal contrast-enhanced CT. They were divided into nine groups (each group, n = 6), according to the volume of contrast medium 1, 2, and 3 mL/kg, and volume of the saline solution 0, 5, and 10 mL. Dynamic CT scanning was performed at the hepatic hilum level. The maximum contrast enhancement, time to maximum enhancement, and time to equilibrium phase were calculated from the time attenuation curves. Mean attenuation values for all groups were measured in the aorta, portal vein, and liver. After contrast enhancement, grading of image quality regarding surrounding artifacts and evaluation of the hepatic hilum structures was performed. For comparison of the effect of the contrast material and saline solution doses, differences in mean attenuation values between the contrast medium 2 mL/kg without saline flush group and the remaining groups, and between contrast medium 3 mL/kg without saline flush group and the remaining groups, were analyzed for statistical significance. There were no significant differences between with and without saline flushing at the same contrast medium dose groups. There were no significant differences in peak values between the 3 mL/kg dose of contrast medium alone and the 2 mL/kg dose of contrast medium with saline solution flush. However, there was a significant difference in peak values between the 3 mL/kg dose of the contrast medium without the saline flush group and the 2 mL/kg dose of the contrast medium alone group. Grades of the artifacts were not significantly different in the saline flush regardless of the dose of the contrast medium. Using 2 mL/kg of contrast medium with saline solution flush resulted in similar liver parenchyma attenuation, compared with using 3 mL/kg of contrast medium without saline solution flush. In CT evaluation of hepatic parenchymal diseases, using 2 mL/kg of contrast medium with saline solution flush may yield decreased risk of contrast nephropathy and cost-saving.

• BMB Reports
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• v.42 no.2
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• pp.106-112
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• 2009

The bio-complex "reaction pattern in vertebrate cells"(RiV) is mainly represented by characteristic exosome-like particles - probably as reaction products of cells to specific stress. The transcription factor NF-kappaB plays a central role in inflammation. We tested the hypothesis that RiV particle preparations (RiV-PP) reduce cellular adhesion molecule (CAM) expression (ICAM-1, VCAM-1, E-selectin) by the attenuation of NF-kappaB translocation in human umbilical vein endothelial cells (HUVEC). After 4 hours, pre-incubation of HUVEC with RiV-PP before stimulation with TNF-alpha significantly reduced ICAM-1 (65.5${\pm}$10.3%) and VCAM-1 (71.1${\pm}$12.3%) mRNA expression compared to TNF-alpha-treated cells (100%, n=7). ICAM-1 surface expression was significantly albeit marginally reduced in RiV/TNF-alpha- treated cells (92.0${\pm}$5.6%, n=4). No significant effect was observed on VCAM-1 surface expression. In RiV/TNF-alpha-treated cells (n=4), NF-kappaB subunits p50 (85.7${\pm}$4.1%) and p65 (85.0${\pm}$1.8%) nuclear translocation was significantly reduced. RiV-PP may exert an anti-inflammatory effect in HUVEC by reducing CAM mRNA expression via attenuation of p50 and p65 translocation.

• Explosives and Blasting
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• v.28 no.2
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• pp.69-75
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• 2010

Excavations by blasting in urban area have caused lots of complaints. Hence, special attentions need to be paid to controlling the ground vibrations in designing blasting for those areas. In this study, among the various parameters that can affect the propagation characteristics of ground vibrations, the effect of the priming location of explosive on the ground vibration level was studied for two types of emulsion explosives that had different detonation velocities. Three priming locations of top, middle, and bottom were considered in a charged hole. In the experiment on the effect of detonation velocity, the ground vibration caused by the explosive with a lower detonation velocity showed larger attenuation in the amplitude. The priming locations also affected the ground vibrations levels. The ground vibration level produced from middle priming was found to be larger than the other priming methods under the same blast conditions, but the attenuation of amplitude was also larger in this case. In contrast, the ground vibration level from bottom priming was not larger than the middle priming, but the attenuation was smaller so that the ground vibration was detected at a longer distance.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.3
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• pp.251-260
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• 2001

Damage Profess of CFRP laminates under monotonic tensile test was characterized by the correlation between Acoustic Emission(AE) and Ultrasonic Test(UT). The amplitude distribution of AE signal from a specimens is an aid to the determination of the extent of the different fracture mechanism such as matrix crack, debonding, fiber pullout and fiber fracture as load is increased. In addtion, the characteristics of ultrasonic amplitude attenuation are useful lot analysis of the different type of fracture mechanism. Different orientation of carbon fiber reinforced plastic specimens were used to investigate the AE amplitude range and ultrasonic amplitude attenuation. Finally, loading-unloading tests were carried out to check Felicity effect. During the tests, ultrasonic amplitude attenuation was investigated at the same time and compared with AE parameters. The result showed that two parameters of both AE and UT could be effectively used for analysis of fracture mechanism in CFRP laminates.

• Journal of the Society of Naval Architects of Korea
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• v.59 no.2
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• pp.64-71
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• 2022

In this paper, we simulate the collision of a solitary wave on a vertical wall in a uniform water channel and investigate the effect of damping on the amplitude attenuation. In order to take into account the damping effect, we introduce the Stokes damping whose dissipation is dependent on the velocity of wave motion on the surface of a thin layer of oil. That is, we use the improved Boussinesq equation with Stokes damping to describe the damped wave motion. Our work mainly focuses on the amplitude attenuation of a propagating solitary wave, which may depend on the Stokes damping together with the initial position and initial amplitude of the wave. We utilize the method of images and a powerful numerical tool (functional iteration method) for solving the improved Boussinesq equation, yielding an effective numerical simulation. This enables us to find the amplitudes of the incident wave and reflected one, whose ratio is a measure of the (wave) amplitude attenuation. Accordingly, we have shown that the reflection of a solitary wave by a vertical wall is dependent on not only the initial amplitude and position of a solitary but the Stokes damping.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.97-98
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• 2008