• Journal of Korea Water Resources Association
• /
• v.48 no.3
• /
• pp.233-243
• /
• 2015

The bimodal flocculation of cohesive sediments in water environments describes the aggregation and breakage process developing a bimodal floc size distribution with dense flocculi and floppy flocs. A two class population balance equation (TCPBE) was tested for simulating the bimodal flocculation by a model-data fitting analysis with two sets of experimental data (low and high turbulent flows) from 1-D flocculation-settling column tests. In contrast to the Single-Class PBE (SCPBE), the TCPBE could simulate interactions between flocculi and flocs and the flocculation mechanism by differential settling in a low turbulent flow. Also, the TCPBE could perform the same quality of simulation as the elaborate Multi-Class PBE (MCPBE), with a small number of floc size classes and differential equations. Thus, the TCPBE was proven to be the simplest model that is capable of simulating the bimodal flocculation of cohesive sediments in water environments and water, wastewater treatment systems.

• Journal of the Korean Society of Combustion
• /
• v.15 no.4
• /
• pp.22-28
• /
• 2010

The Direct Quadrature Method of Moments (DQMOM) has been presented for the solution of population balance equation in the wide range of the multi-phase flows. This method has the inherently interesting features which can be easily applied to the multi-inner variable equation. In addition, DQMOM is capable of easily coupling the gas phase with the discrete phases while it requires the relatively low computational cost. Soot inception, subsequent aggregation, surface growth and oxidation are described through a population balance model solved with the DQMOM for soot formation. This approach is also able to represent the evolution of the soot particle size distribution. The turbulence-chemistry interaction is represented by the laminar flamelet model together with the presumed PDF approach and the spherical harmonic P-1 approximation is adopted to account for the radiative heat transfer.

• Environmental Engineering Research
• /
• v.19 no.2
• /
• pp.165-174
• /
• 2014

A model combining multi-dimensional discretized population balance equations with a computational fluid dynamics simulation (CFD-DPBE model) was developed and applied to simulate turbulent flocculation and sedimentation processes in sediment retention basins. Computation fluid dynamics and the discretized population balance equations were solved to generate steady state flow field data and simulate flocculation and sedimentation processes in a sequential manner. Up-to-date numerical algorithms, such as operator splitting and LeVeque flux-corrected upwind schemes, were applied to cope with the computational demands caused by complexity and nonlinearity of the population balance equations and the instability caused by advection-dominated transport. In a modeling and simulation study with a two-dimensional simplified pond system, applicability of the CFD-DPBE model was demonstrated by tracking mass balances and floc size evolutions and by examining particle/floc size and solid concentration distributions. Thus, the CFD-DPBE model may be used as a valuable simulation tool for natural and engineered flocculation and sedimentation systems as well as for flocculant-aided sediment retention ponds.

• Water for future
• /
• v.53 no.8
• /
• pp.48-54
• /
• 2020

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.40 no.6
• /
• pp.365-372
• /
• 2016

Using the computational fluid dynamics (CFD) technique, we simulated the fluid flow in a Taylor reactor considering the aggregation and breakage of particles. We calculated the population balance equation (PBE) to determine the particle-size distribution by implementing the quadrature method-of-moment (QMOM). It was used that six moments for an initial moments, the sum of Brownian kernel and turbulent kernel for aggregation kernel, and power-law kernel for breakage kernel. We predicted the final mean particle size when the particle had various initial volume fraction values. The result showed that the mean particle size and initial growth rate increased as the initial volume fraction of the particle increased.

• The Journal of Asian Finance, Economics and Business
• /
• v.7 no.10
• /
• pp.443-450
• /
• 2020

This study aims to add insight into the effectiveness of e-training, e-leadership, work-life balance, and work motivation on millennial generation employees' performance in today's work life amid the outbreak of the COVID-19 pandemic that requires to work more online. Unlike previous generations, millennials are technology-literate, intent on succeeding quickly, give up easily, and seek instantaneous gratification. The population in this study are millennial generation employees at one of Honda motorcycle dealers in Jakarta, Indonesia. The number of samples collected was 200. The sampling technique used is the side probability method, with proportional random sampling technique. The research method used is an associative quantitative approach through survey methods and Structural Equation Modeling. Data were collected through questionnaires distributed to millennial generation employees, with results then processed through the Lisrel 8.5 program. The results of this study show, first, that e-training, e-leadership, and work-life balance have positive effect on work motivation. Second, e-training, e-leadership, work-life balance, and work motivation have positive effect on employees' performance. The findings indicate that companies must pay attention to the factors of e-training, e-leadership, and work-life balance to keep employees motivated and to maintain optimal employee performance, especially during the COVID-19 pandemic through working online.

• Clinics in Shoulder and Elbow
• /
• v.25 no.4
• /
• pp.274-281
• /
• 2022

Background: In the present study, the age- and sex-adjusted Constant score (CS) in a normal Indian population was calculated and any differences with other population cohorts assessed. Methods: The study participants were patients who visited the outpatient department for problems other than shoulder and healthy volunteers from the local population. Patients without shoulder pain/discomfort during activity were included in the study. Subjects with any problem that might affect shoulder function (e.g., cervical, thoracic spine, rib cage deformity, inflammatory arthritis) were excluded. Constant scoring of all participants was performed by trained senior residents under the supervision of the senior faculty. Shoulder range of movement and strength were measured following recommendations given by the research and Development Committee of the European Society for Shoulder and Elbow Surgery (2008). A fixed spring balance was used for strength measurement; one end was fixed on the floor and the other end tied with a strap to the wrist of the participant, arm in 90° abduction in scapular plane with palm facing down. Results: Among the 248 subjects (496 shoulders), the average age was 37 years (range, 18-78 years), 65.7% were males (326 shoulders) and 34.3% females (170 shoulders). The mean CS was 84.6±2.9 (males, 86.1±3.0; females, 81.8±2.9). CS decreased significantly after 50 years of age in males and 40 years of age in females (p<0.05). The mean CS was lower than in previous studies for both males and females. Heavy occupation workers had higher mean CS (p<0.05). A linear standardized equation was estimated for calculating the adjusted CS for any age. Conclusions: Mean CS and its change with age differed from previous studies among various population cohorts.

• Journal of Microbiology and Biotechnology
• /
• v.12 no.3
• /
• pp.377-381
• /
• 2002

Recently, interests to remove nitrogen in the nitritation process have increased because of its economical advantages, since it could be a short-cut process to save both oxygen for nitrification and carbon for denitrification compared to a typical nitrification. However, the kinetics related with the nitritation process has not yet been fully understood. Furthermore, many useful models which have been successfully used for wastewater treatment processes cannot be used to estimate effluent nitrite concentration for evaluating performance of the nitritation process, since the process rate equations and population of microorganisms for nitrogen removal in these models have been set up only for the condition of full nitrification. Therefore, the present study was conducted to estimate an effluent nitrite concentration in the nitritation process with a concept of enzymatic inhibition kinetics based on long-term laboratory experiments. Using a nonlinear least squares regression method, kinetic parameters were accurately determined. By setting up a process rate equation along with a mass balance equation of the nitrite-oxidizing step, an effluent nitrite concentration in the nitritation process was then successfully estimated.

• Korean Journal of Environmental Agriculture
• /
• v.32 no.4
• /
• pp.294-303
• /
• 2013

BACKGROUND: It is well known that rice-fields can provide excellent foraging places for birds including seasonal migrants, wintering, and breeding and hence the high biodiversity of rice-fields may be expected. However, how environmental change including climate-changes on life-history and population dynamics in birds on rice-fields has not been fully understood. In order to investigate how climate-change affects population migratory patterns and migration timing, I modeled a population dynamics of birds in rice-fields over a whole year. METHODS AND RESULTS: I applied the Lotka-Volterra equation to model the population dynamics of birds that have been foraging/visiting rice-fields in Korea. The simple model involves the number of interspecific individuals and temperature, and the model parameters are periodic in time as the biological activities related to the migration, wintering and reproduction are seasonal. As results, firstly there was a positive relationship between the variation of seasonal population sizes and temperature change. Secondly, the reduced lengths of season were negatively related to the population size. Overall, the effects of the difference of lengths of season on seasonal population dynamics were higher than the effects of seasonal temperature change. CONCLUSION(S): Climate change can alter population dynamics of birds in rice-fields and hence the variation may affect the fitness, such as reproduction, survival and migration. The unstable balances of population dynamics in birds using paddy rice field as affected by climate change can reduce the population growth and species diversity in rice fields. The results suggest that the agricultural production is partly affected by the unstable balance of population in birds using rice-fields.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2008.05a
• /
• pp.75-81
• /
• 2008

The water shortage in mega cities in Asia, which face a rapid growth in urban population, is an outstanding problem. It is important, therefore, to accurately estimate the water balance in each city in order to use the limited water resources effectively. In this study, we estimated the potential water resources in し sixteen mega cities in Asia. The target cities were Delhi and Calcutta, India; Colombo, Sri Lanka; Dhaka, Bangladesh; Yangon, Myanmar; Bangkok, Thailand; Kuala Lumpur, Malaysia; Singapore; Jakarta, Indonesia; Hanoi, Vietnam; Beijing and Hong Kong, the People's Republic of China; Seoul, the People's Republic of Korea; Manila, the Philippines, and Sapporo and Tokyo, Japan. The potential water resources were estimated by subtracting the actual evaporation from the amount of rainfall. The actual evaporation was estimated using the potential evaporation obtained by Hamon's equation which requires the air temperature and the possible hours of sunshine. When the results of Hamon's and Penman's evaporation equations were compared, a considerable error appeared in the low latitude region. The estimation using Hamon's equation was corrected with the linear regression line of Hamon's and Penman's equations. A classification of the land cover was carried out based on satellite photographs of the target cities, and the volume of surface runoff for each city was obtained using the runoff ratios which depended on the land cover. As a result, the potential water resources in the above mega cities in Asia were found to be greater than the world average. However, the actual water resources which are available for one person to use are probably very limited.