• Journal of Adhesion and Interface
• /
• v.3 no.1
• /
• pp.43-51
• /
• 2002

Advanced adhesive technologies and demanding applications of adhesive joints can no longer be developed successfully by the traditional "trial and error" approach. Appropriate technical solutions require reference to a reliable basis of well-established scientific knowledge about the elementary mechanisms of adhesion (i.e. the 'fundamental adhesion') as they are responsible for the capability of the compound w transmit mechanical force between the adhesive and the substrate surface (i.e. the 'practical adhesion'). Adhesion mechanisms also influence the formation of polymer structure in the adhesive and the resulting macromolecular dynamics in the interphase that is formed in the adhesive near to the substrate. These manifold molecular factors rule the macroscopic behaviour of an adhesive bond line in terms of mechanical and other physical properties as well as in terms of durability. This paper reviews the level of refinement that understanding of fundamental adhesion has achieved up to now.

• Nuclear Engineering and Technology
• /
• v.55 no.3
• /
• pp.1152-1166
• /
• 2023

The bubbly flow of air or steam in subcooled water are investigated here in several test cases, characterized by different pipe sizes, bubble dimensions and flow rates, by means of CFD using a Eulerian-Eulerian approach. The performance of models that differ for the turbulence closure in the continuous phase, as well as for the description of the lift force on the dispersed phase, are compared in detail. When air is considered, the space of the experimental parameters leading to a reasonable performance for the selected models are identified and discussed, while the issues left in the modelling of the concurrent condensation are highlighted for the cases where steam is used.

• Journal of the Korean Institute of Gas
• /
• v.26 no.5
• /
• pp.58-65
• /
• 2022

Gas explosion accidents could cause a catastrophe. we need specialized and systematic accident investigation techniques to shed light on the cause and prevent similar accidents. In this study, we had performed LPG explosion simulation using AUTODYN which is the commercial explosion program and predicted the damage characteristics of the structures by LNG explosive power. In the first step, we could get LPG's physical and chemical explosion properties by calculation using TNT equivalency method. And then, by applying TNT equivalency value about the explosion limit concentration of LPG on the 2D-AUTODYN simulation, we could get the explosion pressure wave profiles (explosion pressure, explosion velocity, etc.). In the last step, we performed LPG explosion simulation by applying to the explosion pressure wave profiles as the input data on the 3D-AUTODYN simulation. As a result, we had performed analyzing of the explosion characteristics of LPG in accordance with concentration through the 3D-AUTODYN simulation in terms of the explosion pressure behavior and structure destruction and damage behavior. The analyses showed that the generated stresses of the structures were lower than the compressive strengths in cases 1(two lane) and 2(four lane), while the generated stress in case 3(six lane) was 8.68e3 kPa, which exceeded the compressive strength of 5.89e3 kPa.

• Asian-Australasian Journal of Animal Sciences
• /
• v.24 no.5
• /
• pp.616-622
• /
• 2011

This study evaluated the fermentation characteristics and protein degradation dynamics of wet green tea grounds (WGTG) silage. The WGTG was ensiled with distilled water (control), or lactic acid bacteria (LAB), enzyme (E), formic acid (FA) and formaldehyde (FD) prior to ensiling. Three bag silos for each treatment were randomly opened at 0, 3, 7, 14, 28 and 60 days after anaerobic storage. For all the treatments, except for FA, there was a rapid decline in pH during the first 7 days of ensiling. LAB treatment had higher lactic acid content, lower ammonia-N ($NH_3$-N) and free-amino nitrogen (FAA-N) contents than other treatments (p<0.05). E treatment had higher lactic acid, water-soluble carbohydrates (WSC) and non-protein nitrogen (NPN) content than the control (p<0.05). FA treatment had higher $NH_3$-N and FAA-N content than the control (p<0.05). FD treatment had lower NPN and FAA-N content than the control, but it did not significantly inhibit the protein degradation when compared to LAB treatment (p>0.05). Results indicate that LAB treatment had the best effect on the fermentation characteristics and protein degradation of WGTG silage.

• Korean Journal of Applied Biomechanics
• /
• v.22 no.3
• /
• pp.295-304
• /
• 2012

This study, through biomechanical analysis, conducts a risk assessment of injury occurrence in ballet dancers while they perform running and jumping movements. The participants were nine female collegiate students majoring in ballet(age: $20.89{\pm}1.17years$; height: $160.89{\pm}7.01cm$; mass: $48.89{\pm}3.26$). Descriptive data were expressed as $mean{\pm}standard$ deviation(SD) for all variables. An independent t-test was conducted to determine how the following variables differed: duration time, position of the center of gravity, angle of the hip, torque of the hip, and muscle activity. All comparisons were made at the p<0.05 significance level. The results show that the jump time was two times longer than the run time in the duration time. The jump length was also longer than the run. The angle of the hip and the torque at the hip were higher in the right. The vastus medialis muscle was most frequently used. These findings demonstrate that participants' jumps may require more biomechanical variables for performance of better and more correct $jet{\acute{e}}$.

• Pediatric Infection and Vaccine
• /
• v.30 no.2
• /
• pp.73-83
• /
• 2023

Purpose: This study aimed to investigate the viral load dynamics in children with underlying malignancies diagnosed with symptomatic coronavirus disease 2019 (COVID-19). Methods: This was a retrospective longitudinal cohort study of patients <19 years old with underlying hemato-oncologic malignancies that were diagnosed with their first symptomatic severe acute respiratory syndrome coronavirus 2 polymerase chain reaction (PCR)-confirmed COVID-19 infection during March 1 to August 30, 2022. Review of electronic medical records and telephone surveys were undertaken to assess the clinical presentations and transmission route of the patients. Thresholds of negligible likelihood of infectious virus was defined as E gene reverse transcription (RT)-PCR cycle threshold (Ct) value ≥25. Results: During the 6-month study period, a total of 43 children with 44 episodes of COVID-19 were included. Of the 44 episodes, the median age of the patients included was 8 years old (interquartile range [IQR], 4.9-10.5), and the most common underlying disease was acute lymphoid leukemia (n=30, 68.2%), followed by patients post-hematopoietic stem cell transplantation (n=8, 18.2%). Majority of the patients had mild COVID-19 (n=32, 72.7%), and three patients (7.0%) had severe/critical COVID-19. Furthermore, 2.3% (n=1) died of COVID-19 associated acute respiratory distress syndrome. The largest percentage of the patients showed E gene RT-PCR Ct value ≥25 between 15-21 days (n=13, 39.4%), followed by 22-28 days (n=10, 30.3%). In 15.2% (n=5), E gene RT-PCR Ct value remained <25 beyond 28 days after initial positive PCR. Refractory malignancy status (β, 67.0; 95% confidence interval, 7.0-17.0; P=0.030) was significantly associated with prolonged duration of E gene RT-PCR <25. A patient with prolonged duration of E gene RT-PCR Ct value <25 was suspected to have infectivity shown by the transmission of the virus to his mother at day 86 after his initial positive test. Conclusions: Children that acquire symptomatic COVID-19 during refractory malignancy state are at a high risk for prolonged shedding warranting PCR-based transmission precautions in this cohort of patients.

• Journal of Korean Society of Water and Wastewater
• /
• v.28 no.2
• /
• pp.225-233
• /
• 2014

This paper presents a Computational Fluid Dynamics(CFD) based simulation and experimental tracer test of flow pattern and turbulent energy dissipation inside a serpentine flocculation basin with continuous operation. Research focused on the evaluation of a specific flow pattern on the hydraulic behavior on the flocculation basin. From the results of CFD simulation and actual tracer test, both results were in good accordance with each other. Also, each Morill index were calculated as 1.5 from CFD simulation and 1.7 from actual tracer test, respectively. Especially, turbulence energy was dissipated relatively higher in the vicinity of inlet to the flocculation basin than other region. The differences between the CFD simulation and actual tracer test were 1.4 min in $T_{50}$, and 1.3 min in $T_p$, respectively.

• International Journal of Vascular Biomedical Engineering
• /
• v.2 no.2
• /
• pp.16-26
• /
• 2004

The object of this study is to develop a mathematical model of the hemodialysis system including the mechanism of solute kinetics, water exchange and also cardiovascular dynamics. The cardiovascular system model used in this study simulates the short-term transient and steady-state hemodynamic responses such as hypotension and disequilibrium syndrome (which are main complications to hemodialysis patients) during hemodialysis. It consists of a 12 lumped-parameter representation of the cardiovascular circulation connected to set-point models of the arterial baroreflexes, a kinetic model (hemodialysis system model) with 3 compartmental body fluids and 2 compartmental solutes. We formulate mathematically this model in terms of an electric analog model. All resistors and most capacitors are assumed to be linear. The control mechanisms are mediated by the information detected from arterial pressoreceptors, and they work on systemic arterial resistance, heart rate, and systemic venous unstressed volume. The hemodialysis model includes the dynamics of urea, creatinine, sodium and potassium in the intracellular and extracellular pools as well as fluid balance equations for the intracellular, interstitial, and plasma volumes. Model parameters are largely based on literature values. We have presented the results on the simulations performed by changing some model parameters with respect to their basal values. In each case, the percentage changes of each compartmental pressure, heart rate (HR), total systemic resistance (TSR), ventricular compliance, zero pressure filling volume and solute concentration profiles are represented during hemodialysis.

• Tunnel and Underground Space
• /
• v.21 no.4
• /
• pp.274-280
• /
• 2011

Evacuation and Fatalities Simulation is one of the core technologies for performance based design. Recently, developed programs in foreign countries have limitations such as simple fatality calculation and coarse visual interface. This study developed an advanced evaluation program for evacuation and fatalities to overcome limitations of existing programs and improve various applications, i.e., an evacuation algorithm using elevators as well as evacuation stairs. In addition, the evaluation program can let users make a decision of fatalities from fire by coupling with FDS (Fire Dynamics Simulator) from NIST and realizes three-dimensional virtual space using a graphic module.

• Journal of Institute of Control, Robotics and Systems
• /
• v.21 no.9
• /
• pp.818-826
• /
• 2015

This paper presents a novel methodology for estimating vehicle ego-motion, i.e. tri-axis linear velocities and angular velocities by using stereo vision sensor and 2G1Y sensor (longitudinal acceleration, lateral acceleration, and yaw rate). The estimated ego-motion information can be utilized to predict future ego-path and improve the accuracy of 3D coordinate of obstacle by compensating for disturbance from vehicle movement representatively for collision avoidance system. For the purpose of incorporating vehicle dynamic characteristics into ego-motion estimation, the state evolution model of Kalman filter has been augmented with lateral vehicle dynamics and the vanishing point estimation has been also taken into account because the optical flow radiates from a vanishing point which might be varied due to vehicle pitch motion. Experimental results based on real-world data have shown the effectiveness of the proposed methodology in view of accuracy.