• Journal of ILASS-Korea
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• v.3 no.2
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• pp.34-41
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• 1998

The present experimental study investigates the effect of an initial disturbance on the breakup mechanism of a liquid column. With varying the maginitude of the inital disturbance, we measure the surface wave of liquid column with adopting laser shadow method and analyze the growth rate of liquid column and breakup frequency. The experimental results show that thebreakup characteristics of liquid column is significantly influenced by the frequency of the initial disturbance. We concluded that the most uniform droplet occurs when the frequency of initial disturbance coincides with the natural frequency of the liquid column.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.4
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• pp.708-716
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• 1989

The purpose of this study is to investigate the breakup mechanism of a liquid jet in a coaxial air flow. By using the high speed camera, measured were the instantaneous change of the wave length, amuplitude of disturbance, propagation velocity of wave and breakup length, and the relationships between those data were examined. The shape of the surface of the liquid jet appeared to be rather complicated and irregular. The growth rate of disturbance was not constant, and was changed at the moment of 3ms prior to the disintegration of the liquid jet. Simultaneously at this moment, the propagation velocities of the sequential waves were reversed and the wave length was rapidly decreased.

• Transactions on Control, Automation and Systems Engineering
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• v.4 no.4
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• pp.277-282
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• 2002

This paper proposes a nonlinear adaptive controller based on back-stepping method for tracking reference substrate concentration by manipulating dilution rate in a continuous baker's yeast cultivating process in stirred tank bioreactor. Control law is obtained from Lyapunov control function to ensure asymptotical stability of the system. The Haldane model for the specific growth rate depending on only substrate concentration is used in this paper. Due to the uncertainty of specific growth rate, it has been modified as a function including the unknown parameter with known bounded values. The substrate concentration in the bioreactor and feed line are measured. The deviation from the reference is observed when the external disturbance such as the change of the feed is introduced to the system. The effectiveness of the proposed controller is shown through simulation results in continuous system.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.74.3-74
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• 2001

This paper proposes a nonlinear adaptive controller based on back-stepping method for tracking reference substrate concentration by manipulating dilution rate in a continuous baker´s yeast cultivating process in stirred tank bioreactor. Control law is obtained from Lyapunov control function to ensure asymptotical stability of the system. The Haldane model for the specific growth rate depending on only substrate concentration is used in this paper. Due to the uncertainty of specific growth rate, it has been modified as a function including the unknown parameter with known bounded values. The substrate concentration in the bioreactor and feed line are measured. The deviation from the reference is observed when the external disturbance such as the change of the feed is introduced to the system ...

• Journal of the Korean Society of Environmental Restoration Technology
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• v.12 no.1
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• pp.82-91
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• 2009

Research was initiated to investigate vegetation characteristics of native ('Pureundle' and 'Sewon') and introduced ('Brilliant' and 'Midnight') Kentucky bluegrass (KB, Poa pratensis L.) varieties by soil-seed applying system on a cut-slope in May 17, 2008. There were no statistic differences observed in soil hardness and soil moisture content while significant differences were observed in surface coverage rate, height and disease occurrence in native and introduced KB varieties. The introduced 'Brilliant' KB was highest in the surface coverage rate from the early period of seeding to August 11, 2008. The surface coverage rate of introduced varieties were high when compared to native varieties in their early growth stage. But native varieties reached to equal surface coverage rate with the introduced varieties when three months after seeding. The height of 'Pureundle' and 'Brilliant' KBs were high compared with Midnight and Sewon KBs. 'Pureundle' and 'Brilliant' KBs were damaged by disease whereas there were no disease occurrence in 'Midnight' and 'Sewon' KBs. Probably, the disease occurrence was close related with the height of KBs not with native and introduced KB varieties. These results indicate that the growth of KB on a cut-slope are statistically affected by varieties in early growth stage of this experiment but reach equal rate between native and introduced KB varieties in three months after seeding. This growth characteristics implies the huge potential of native KB varieties seeding for cut-slope vegetation. Considering that native KB varieties are adapted to a environment and have no risk of causing disturbance to the ecosystem compared to the introduced KB varieties, the use of them as native varieties for a cut-slope vegetation can be increased.

• Journal of Practical Agriculture & Fisheries Research
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• v.25 no.4
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• pp.78-83
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• 2024

This study was carried out to analyze the effect of changes in the light environment caused by the daylight disturbance on the growth, flowering, and cut flower quality of spray chrysanthemums. The spray chrysanthemum 'Yellow Cap' and 'Pitch PangPang' cultivars for cut flowers were artificially shaded to interfere with 66% of sunlight compared to the non-shading, and then the growing and flowering characteristics, and cut flower yield were investigated accordingly. There was no significant difference in the cut flower yield per unit area between the shading and the non-shading treatments. However, the number of days to flowering was 72.1 days for the 'Yellow Cap' and 65.2 days for the 'Pitch PangPang', which were delayed by 14.1 and 8.9 days, respectively, compared to the non-shading light. In the shading treatment, the flower diameter and the number of flowers also decreased by 10% and 15%, and 30% and 28% for both 'Yellow Cap' and 'Pitch PangPang', respectively. The stem length also decreased by 10% and 20%, the stem diameter by 23% and 37%, and fresh weight by 32% and 33%, respectively. The shading treatment delayed the flowering of chrysanthemums and reduced the growth such as flower diameter, number of flowers, and the length and weight of cut flowers. Based on these results, the daylight disturbance by artificial buildings is expected to reduce the productivity and quality of cut flowers by limiting the light intensity needed for chrysanthemum growth, flower bud differentiation, and flower development. Therefore, further research is needed on the rate of decrease in yield and market value according to the degree of shading to relieve damage to chrysanthemum growers caused by the daylight disturbance.

• Microbiology and Biotechnology Letters
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• v.21 no.4
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• pp.354-365
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• 1993

A novel control method with automatic tuning of PID controller parameters has been developed for efficient regulation of dissolved oxygen concentration in fed-batch fermentations of Escherichia coli. Agitation speed and oxygen partial pressure in the inlet gas stream were chosen to be the manipulated variables. A heuristic reasoning allowed improved tuning decisions from the supervision of control performance indices and it coule obviate the needs for process assumptions or disturbance patterns. The control input consisted of feedback and feedforword parts. The feedback part was determined by PID control and the feedforward part is determined from the feed rate. The proportional gain was updated on-line by a set of heuristics rules based on the supervision of three performance indices. These indices were output error covariance, the average value of output error, and input covariance, which were calculated on-line using a moving window. The integral and derivative time constants were determined from the period of output response. The specific growth rate was maintained at a low level to avoid acetic acid accumulation and thus to achieve a high cell density. The specific growthe rate was estimated from the carbon dioxide evolution rate. In fed-batch fermentation, the simutaneous control of dissolved oxygen concentration (at 0.2; fraction of saturated value) and specific growth rate (at 0.25$hr^{-1}$) was satisfactory for the entire culture period in spite of the changes in the feed rate and the switching of control input.

• Journal of Forest and Environmental Science
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• v.23 no.2
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• pp.93-100
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• 2007

This study was carried out to select the utilizable vegetations for the stabilization of slopes and river banks, landscape creation and water quality cleansing in dams, lakes and streams. In this study, 4 species were investigated for their survival and growth characteristics in the complete and partly flooding conditions with various flooding periods. The results are as followings; Acorus calamus var. angustatus showed the highest flooding tolerance based on survival rate and growth condition. Equisetum hyemale, Acorus gramineus and Salix gracilistyla followed after Acorus calamus var. angustatus in the order of flooding tolerance. Particularly, A. calamus var. angustatus and E. hyemale showed higher survival rate and grew well even when they were completely submerged in the water up to 120 days. As they were partially submerged longer, they grew better. This ascertained that they had strong flooding tolerance. When A. gramineus were completely submerged in the water, their growth was disturbed but they did not die in the complete submergence up to 120 days. A. gramineus had a small growth disturbance and showed the highest vitality of leaves among the species. Though S. gracilistyla showed somewhat low growth rate in the complete water submergence and died in 90 days, it also can grow back to normal with some changes of water level.

• The Korean Journal of Ecology
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• v.19 no.4
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• pp.305-320
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• 1996

It is necessary to obtain information about the productivity of the human-influenced forest and to understand the consumption of biomass resources in secondary forest in order to examine the resource flux by human activity in rural landscape. Thus the aims of this study were to elucidate the biomass and their use of secondary Pinus densiflora forests and to discuss sustainable utilization of secondary forests in rural landscape system. This study was carried out in Yanghwa-ri, Kongjugun, Chungcheongnam-do, central Korea. The changes of growth rate and aboveground biomass of a pine forest for 2 years were analyzed to understand forest management regimes in rural pine forests. Through allometric equations deduced from 25 sample trees, biomass was estimated. The biomass increase of pine forest was approximately 16.36 t/ha/yr in the unexploited stand and 12.24 t/ha/yr in the exploited stand. These were nearly equal to those of natural pine forests in central Korea. This result proved that human-influenced pine forest in rural landscape as well as the natural one has high potentiality to provide forest products. Making graveyard in forest-land was the important disturbance and land-use which currently occurring in rural landscape in the study area. Finally, we presented some forest management for stutainable and positive uses of secondary forests as one of the local energy resources in terms of the holistic landscape-ecological view.

• Journal of ILASS-Korea
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• v.3 no.4
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• pp.1-7
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• 1998

The measurement of breakup length of viscous liquid jet in stagnant air was conducted by a 3CCD digital video camera. The nozzle diameters of 4, 6, 8mm with L/d=50 were selected and the dynamic viscosity of viscous liquid made of glycerine and water was in the range of $1.061\times10^{-6}m^2/s$ to $4.935\times10^{-5}m^2/s$. The critical velocity is decreased and the breakup length is increased with the increase of nozzle diameter at the same dynamic viscosity of liquid. At the same nozzle diameter, the breakup length and the critical velocity are both increased with the increase of dynamic viscosity of liquid. It is found in the theoretical analysis that the initial disturbance level is the main cause of occurrance of critical Reynolds number in the stability curve. The comparison of experimental critical Reynolds number and the empirical correlation by Tanasawa and Toyota reveals the relatively good agreement.