• 대한수학회보
• /
• 제53권3호
• /
• pp.843-852
• /
• 2016

A vortex sheet is susceptible to the Kelvin-Helmhotz instability, which leads to a singularity at finite time. The vortex blob model provided a regularization for the motion of vortex sheets in an inviscid fluid. In this paper, we consider the blob model for viscous vortex sheets and present a linear stability analysis for regularized sheets. We show that the diffusing viscous vortex sheet is unstable to small perturbations, regardless of the regularization, but the viscous sheet in the sharp limit becomes stable, when the regularization is applied. Both the regularization parameter and viscosity damp the growth rate of the sharp viscous vortex sheet for large wavenumbers, but the regularization parameter gives more significant effects than viscosity.

• 한국주조공학회지
• /
• 제10권5호
• /
• pp.399-407
• /
• 1990

The effect of thermal cycling and isothermal exposure on the high temperature microstructural stability of unidirectionally solidified $Al-CuAl_2$ eutectic composite has been studied. A coarsening procedures of lamellar eutectic structures were initiated at growth fault region because of diffusion through low angle boundary at this region. It was considered that thermally induced residual stresses produced by thermal cycling were high enough to increase the dislocation density in Al-rich matrix phase. However, it was also considered that dislocations generated by these high thermal stresses were annihilated at high temperature by stress relaxation. Consequently, the thermal cycling up to 1440 cycles between 20 and $520^{\circ}C$ did not affect the microstructural stability.

• 한국공작기계학회논문집
• /
• 제13권2호
• /
• pp.40-46
• /
• 2004

Magnetic bearing has been adopted to support a rotor by electromagnetic force without mechanical contact and lubrication process. The recent growth of magnetic bearing applications in many industrial fields requires more accurate design of bearing-rotor system. Due to external forces and uncertainties of magnetic bearing system the actual performance and stability my be worse than it is designed. This paper describes the governing equations of rotor magnetic bearing systems and/or the designing of robust controller via standard $H_{\infty}$ control problem. The system stability and response characteristics are studied by simulations and verified with experimental results.

• 한국농공학회지
• /
• 제40권5호
• /
• pp.100-108
• /
• 1998

Compost stability represents the state of microbiological activity and measurements of respiration either through $CO_2$ evolution or $O_2$ uptake should provide the best indication of this state. Hog manure amended with sawdust was composted in a pilot-scale reactor vessels using continuous and intermittent aeration for 3 weeks. In this study we evaluated the $CO_2$ respiration rate effect of aeration method on the reduction of $CO_2$ evolution, and investigated the stability of fresh and finished compost for plant growth. The intermittently aerated composting is a practical proposition for a very stable compost making. The $CO_2$ respiration rate in the fresh and finished compost during intermittently aerated composting was maintained from 0.3 to 1.4 and was good for use in horticulture, while the continuously aerated composting was 7 to 23 and needed more time for compost curing.

• 한국연소학회지
• /
• 제18권2호
• /
• pp.42-50
• /
• 2013

Linear stability analysis of radiating counterflow diffusion flames is numerically conducted to examine the instability characteristics of cellular patterns. Lewis number is assumed to be 0.5 to consider diffusional-thermal instability. Near kinetic limit extinction regime, growth rates of disturbances always have real eigen-values and neutral stability condition of planar disturbances perfectly falls into quasi-steady extinction. Cellular instability of disturbance with transverse direction occurs just before steady extinction. However, near radiative limit extinction regime, the eigenvalues are complex and pulsating instability of planar disturbances appears prior to steady extinction. Cellular instability occurs before the onset of planar pulsating instability, which means the extension of flammability.

• 한국자원식물학회지
• /
• 제32권1호
• /
• pp.19-28
• /
• 2019

An efficient shoot regeneration condition for pea cv. 'Sparkle' was developed by using optimum explant, plant growth regulator concentrations, and pretreatment of BA onto explant. The average shoot number per explant showed the highest on two kinds of shoot induction media (MSB5 media containing 2 mg/L BA and a combination of 2 mg/L BA and 1 mg/L TDZ) when cotyledonary node explants were cultured. Moreover, the pretreatment of explant in 200 mg/L BA solution was found to be more effective in shoot induction than that of non-pretreatment. By histological study, cell division and proto-meristem were formed near the surface of the sub-epidermal and epidermal cell layers of cotyledonary node in earlier than 3 days after culture. The analysis of genetic stability of regenerants by using thirteen ISSR markers showed that in vitro regenerated plants showed polymorphism with 8.3% compared with their mother plants.

• Korean Chemical Engineering Research
• /
• 제62권1호
• /
• pp.112-117
• /
• 2024

Numerical simulations on the onset and the growth of viscous fingering during the miscible displacement due to the radial source flow were conducted. With introduction of a new stability criterion, the critical log-viscosity ratio, R_c, was found as a function of the Peclet number, Pe. Similar to the previous linear stability analyses, Pe made the system unstable, i.e., accelerated the onset of instability. For a large Pe system, the present numerical simulation yielded much stable results than the previous theoretical predictions This discrepancy was commonly encountered in the comparison between the theoretical prediction and the experimental finding. Additionally, the difference between the rectilinear system and the present one was also discussed. The present system was found more insensitive to the Peclet number than the rectilinear one.

• 한국세라믹학회지
• /
• 제56권6호
• /
• pp.589-595
• /
• 2019

The top-seeded solution growth (TSSG) method is an effective approach for the growth of high-quality SiC single crystals. In this method, the temperature gradient in the melt is the key factor determining the crystal growth rate and crystal quality. In this study, the effects of the aperture at the top of the hot-zone on the growth of the SiC single crystal obtained using the TSSG method were evaluated using multiphysics simulations. The temperature distribution and C concentration profile in the Si melt were taken into consideration. The simulation results showed that the adjustment of the aperture at the top of the hot-zone and the temperature gradient in the melt could be finely controlled. The surface morphology, crystal quality, and polytype stability of the grown SiC crystals were investigated using optical microscopy, high-resolution X-ray diffraction, and micro-Raman spectroscopy, respectively. The simulation and experimental results suggested that a small temperature gradient at the crystal-melt interface is suitable for growing high-quality SiC single crystals via the TSSG method.

• The Journal of Asian Finance, Economics and Business
• /
• 제8권4호
• /
• pp.11-19
• /
• 2021

This study aims to analyze the causality relationship between sectoral stock markets (agricultural, financial, industrial, and mining sectors) and economic growth in the short and long term as well as to analyze whether it has similar types or not. The data used is quarterly time-series data (first quarter 2009 to fourth 2019). To determine the causality relationship, this study conducts a variable and multivariate causality test. The results of the varying granger causality test show that there is only a one-way relationship, where the economic growth of the agriculture sector affects its shares. A one-way relationship also occurs in stocks of the industrial sector, which has an influence on economic growth. The multivariate causality test shows that the economic growth of the agricultural sector has a two-way causality relationship, and it also exists between the industrial sector and the financial sector stock markets. The two-way causality relationship between the stock market and sectoral economic growth is a convergence towards long-term equilibrium. The findings of this study suggest that the government through the Financial Services Authority and the Indonesia Stock Exchange have to maintain stability in the stock market as a supporter of the national economy.

• Asian Journal of Business Environment
• /
• 제13권2호
• /
• pp.21-28
• /
• 2023

Purpose: This study aims to analyze the determinants of Green Total Factor Productivity (Green TFP) growth in the agricultural sector in Indonesia from 1980-2018. Research design, data, and methodology: The growth of Green TFP in the agricultural sector is calculated using the Growth Accounting Method. Moreover, this study uses multiple linear regression to analyze the determinants of the growth of Green TFP in the agricultural sector in Indonesia. Results: The survey results show that the average growth of Green TFP in the agricultural sector in Indonesia is still negative, which indicates that the efficiency of production factor or mastery of technology is still low. Inflation and patent applications are variables that significantly affect the growth of Green TFP in the agricultural sector, where the inflation variable has a negative effect. In contrast, the variable growth of patent applications has a positive impact. Conclusions: The government needs to continue to improve efficiency by organizing various programs related to increasing mastery of technology in the agricultural sector. The government also needs to advance research and development by promoting patents to become research incentives and impact the improvement of new technologies, especially those related to the environment. Moreover, economic stability needs to be maintained through inflation control.