• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.1 no.2
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• pp.87-91
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• 1997

Leaf discs were excised from spinach leaves (Spinacia oleracea L.) and floated in phosphate buffer (pH 6.8) containing paraquat solutions (0, 0.1, 1.0, 10, 20, 50 and 100 ppm), and incubated in the growth chamber under 5,500 lux illumination at $25^{\circ}C$ for 24 hr. Treatment with paraquat caused the formation of malondialdehyde (MDA), an indicator of lipid peroxidation in leaf discs. When 1.0, 10, 20, 50 and 100 ppm of paraquat solutions were applied to leaf discs, the contents of MDA were increased by 63, 86, 100, 140 and $150\%$ of the level without paraquat treatment respectively. 1.0, 10, 20, 50 and 100 ppm of paraquat treatments reduced the amounts of ascorbic acid in leaf discs by 23, 35, 38, 42 and $56\%$ of the level without paraquat treatment, respectively. Activities of superoxide dismutase (SOD) in leaf discs of 1.0, 10, 20, 50 and 100 ppm of paraquat treatments were decreased by 23, 42, 48, 61 and $70\%$ of the level of SOD in non-treated group, respectively. The results suggest that paraquat may cause peroxidation of membrane lipid in spinach leaves as a result of paraquat-induced destruction of physiological defense against oxygen phytotoxicity.

• Korean Journal of Materials Research
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• v.31 no.7
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• pp.386-391
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• 2021

The formation of CaCO₃ in microalgal culture is investigated and applied for effective separation of microalgae. The presence of several cationic ions in the culture medium mediates the formation of 3 types of mineral precipitates depending on the concentration of mineral precursors, Ca²⁺ and CO₃^2-, amorphous nano-flakes, rhombohedral calcites, and spherical vaterites. While amorphous phased precipitates are formed for all concentrations of mineral precursor, only calcites are formed for 30 mM solutions of mineral precursor, and mixtures of calcites and vaterites are formed for 50 and 100 mM solutions of mineral precursor. The harvesting efficiency is also dependent on the concentration of the mineral precursor: from 90 % for 10 mM to 99 % for 100 mM after 60 mins' of gravitational sedimentation. The formation of nano-flakes on the surface of microalgal cells induces the flocculation of microalgae by breaking the stable dispersion. The negatively charged surface of the microalgal cell is compatible not only with nano-flake attachment but also with the growth of calcitic crystals in which microalgal cells are embedded.

• Korean Journal of Plant Resources
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• v.17 no.2
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• pp.94-101
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• 2004

Commercial value of soybean sprouts should be affected by their morphology including the lateral roots. This study was carried out to determine the effect of benzyladenopurine (BA) concentration on growth and morphology of soybean sprouts in order to compare them with the selling products collected from the markets. Four cultivars (cv. Eunhakong, Pungsannamulkong, Sowonkong, and Junjery) were cultured for 6 days after imbibed for 5 hours into different BA solutions (0, 1,2,4, and 8 ppm). On the 6th day, hypocotyl length was measured to calculate the composition rate of ＞ 7 cm (A), 4 to 7 cm (B), ＜ 4 cm (C) and non-germination (D), and the ratio of hypocotyl to root length (H/R ratio) on the base of hypocotyl length as well as lateral root, hypocotyl diameter, and fraction fresh and dry weights. The composition rates classified with hypocotyl length showed big differences between 4 cultivars in class A and C; Class A, in which cv. Sowonkong and Junjery had higher rates than cv. Eunhakong and Pungsannamulkong, was decreased with BA concentration of higher than 4 ppm, but class C showed the reverse result to class A. Any lateral root was not formed in higher than 4 ppm BA solutions although fewer in cv. Pungsannamulkong and Junjery than in the two other cultivars. Hypocotyl and root lengths were decreased with increased BA concentrations, and in all BA concentration, hypocotyl length of cv. Junjery was the longest. Hypocotyl diameter, hypocotyl and total fresh weights were thicker and heavier in 2 to 4 ppm BA concentrations than in the other ones, although in case of BA application, cv, Eunhakong and Sowonkong were heavier. The H/R ratios were increased with increased BA concentration. The ratios of nearly all the selling products ranged from 1 to 2 ppm when compared to them from our experiment.

• Journal of Applied Reliability
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• v.15 no.2
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• pp.90-100
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• 2015

Reliability growth rate (or reliability growth curve slope) have the two cases of trend as a constant or changing one during the reliability growth testing. The changing case is very common situation. The reasons of reliability growth rate changing are that the failures to follow the NHPP (None-Homogeneous Poisson Process), and the solutions implemented during test to break out other problems or not to take out all of the root cause permanently. If the changing were big, the "Goodness of Fit (GOF)" of reliability growth curve to test data would be very low and then reduce the accuracy of assessing result with test data. In this research, we are using Duane model and AMSAA model for assessing test data and projecting the reliability level of complex and repairable system as like construction equipment and vehicle. In case of no changing in reliability growth rate, it is reasonable for reliability engineer to implement the original Duane model (1964) and Crow-AMSAA model (1975) for the assessment and projection activity. However, in case of reliability growth rate changing, it is necessary to find the method to increase the "GOF" of reliability growth curves to test data. To increase GOF of reliability growth curves, it is necessary to find the proper parameter calculation method of interesting reliability growth models that are applicable to the situation of reliability growth rate changing. Since the Duane and AMSAA models have a characteristic to get more strong influence from the initial test (or failure) data than the latest one, the both models have a limitation to contain the latest test data information that is more important and better to assess test data in view of accuracy, especially when the reliability growth rate changing. The main objective of this research is to find the parameter calculation method to reflect the latest test data in the case of reliability growth rate changing. According to my experience in vehicle and construction equipment developments over 18 years, over the 90% in the total development cases are with such changing during the developing test. The objective of this research was to develop the newly assessing method and the process for GOF level increasing in case of reliability growth rate changing that would contribute to achieve more accurate assessing and projecting result. We also developed the new evaluation method for GOF that are applicable to the both models as Duane and AMSAA, so it is possible to compare it between models and check the effectiveness of new parameter calculation methods in any interesting situation. These research results can reduce the decision error for development process and business control with the accurately assessing and projecting result.

• Korean Business Review
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• v.22 no.2
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• pp.35-59
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• 2009

The drive for sustainable economic growth for the sub Saharan African region continues to occupy a central place in the debate of how to move the region forward. For decades, governments, policy makers, Non Governmental Organizations and world bodies including the World Bank, IMF, ADB, USIAD and the European Union have engaged policies aimed at bringing solutions to the horrendous poverty crisis to nations of this region. Despite these noble actions and intents, poverty and underdevelopment has prevailed in countries of the region such as Cameroon. Cameroon is mainly an agricultural economy with its products facing declining prices and competition from synthetic substitutes resulting to deficits of balance of trades. This has resulted to borrowing and debt. At the same time, it is a country blessed with an abundance of tourist resources. From the literature review, tourism potency to economic growth is overwhelming. This research was motivated by the quest to find answers to questions such as; why development policies during the last two decades not succeeded in achieving Economic growth in countries of this region particularly Cameroon and why the country/ region still beleaguered by poverty and debt despite haven implemented various economic development plans. In recent years, the role of tourism has become increasingly recognized in its role of economic growth and poverty alleviation. This study attempts to unveil tourism's contribution to economic growth and to push for Tourism development as an al ternative economic growth alternative to Cameroon. Previous economic policies have ignored to tie economic growth within the country's socio-economic, geo-political and environmental circumstances. Findings from this work suggest that any sound economic policy can not afford to ignore the country's stock of both human and fiscal capital. Findings presented herewith validate Tourism as a feasible indigenous economic growth alternative that helps bringing employment, capital investment and protect the environmental ruin.

• Journal of Bio-Environment Control
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• v.7 no.1
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• pp.35-41
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• 1998

This experiment was conducted to find out the effect of artificial light sources(high-pressure sodium lamp, metal halide lamp and fluorescent lamp) on growth of crisphead lettuce(Lactuca sativa L.) in a plant factory. No significant differences in leaf fresh and dry weight were presented among them. Lettuce plants grown under fluorescent lamp showed the lowest growth. Considering the growth of lettuce and efficiency of lamps, it is worth using HPS(high-pressure sodium) lamp in plant factories. The leaves of lettuce plants grown under artificial light sources showed tipburn symptoms at 14th day after transplanting. The beginning of tipburn symptom have been seen on the ninth to tenth leaves from the cotyledons. It is estimated that the occurrence of tipburn was related to rapid growth and K uptake of the lettuce Plants. The Ca, Mg. Cu and Zn elements tended to be accumulated in the nutrient solutions but the T-N, P, Fe and Mn elements keep in balance in them.

• Korean Journal of Crystallography
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• v.7 no.1
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• pp.30-35
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• 1996

Calcite(CaCO3) single crystals were grown hydrothermally and transmittance of as grown crystals was measured. Instead of platinium, teflon was lined onto the wall of autoclave to prevent the corrosion of autoclave wall by acidic NH4Cl solution. Spontaneous nucleation and growth of calcite crystal on teflon was reduced considerably by addition of NaCl and /or CH3COOH and applying low temperature gradient. When the temperature gradient exceeded to a few degrees from the critical temperature gradient(6-7℃), spontaneous nucleation and growth was rapidly increased in any hydrothermal solutions. Precise temperature control is thought to be the most important factor for the growth of calcite single crystal by hydrothermal technique. As grown calcite single crytal showed high transmittance compared to natural one by UV-visible analysis.

• Journal of the Korean Ceramic Society
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• v.29 no.12
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• pp.963-969
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• 1992

This paper describes the feasibility for a direct production of zinc oxalate powders from zinc-loaded D2EHPA solutions combining the purification and the precipitation in one operation unit. This process has the potential as an alternative to conventional method for the synthesis of zinc oxide precursor particles from the hydrometal-lurgical processes. Zinc was extracted into D2EHPA in kerosene and then zinc-loaded D2EHPA solution was emulsified with oxalic acid-HCl solution to precipitate zinc oxalate powder, which was readily calcined to zinc oxide. The precipitation kinetics and yield were sensitive to experimental conditions. The morphology, size and size distribution of the zinc oxalate powders varied with zinc/oxalate ion riatio, temperature, and the presence of SPAN 60, which affected nucleation, growth, and the emulsion characteristics.

• Korean Membrane Journal
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• v.7 no.1
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• pp.51-57
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• 2005

Pervaporation with a membrane is one of the economic technologies for separation of liquid mixtures including organic/water mixtures. The ZSM-5 membrane was used fur pervaporation of dichloromethane, 1,2-dichloroethane and trans-1,2-dichloroethylene from their aqueous solutions since its physical property shows very hydrophobic. ZSM-5 crystals were hydrothermally grown and deposited on the inside of a porous sintered stainless steel tube by the secondary growth method. Fluxes of dichlorinated organic compounds were observed to be $50{\~}429\;g/m^2/h$ while separation factors were $15{\~}320$ depending on a mole fraction of a dichlorinated organic compound in a feed solution ranged from 0.0001 to 0.001 mole fraction and the operation temperature between $25^{\circ}C\;and\;35^{\circ}C$.

• Journal of the Korean Professional Engineers Association
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• v.42 no.6
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• pp.47-52
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• 2009

According to increasing demand of water mainly due to the growth of population and increased water consumption, many countries either face or worry about the shortage of fresh water. Proportionately, importance and efforts of each country to develop the potable water has been gradually increasing as well. Among others, desalination of seawater has been developed to one of the solutions mainly from the middle east and other arid regions to produce large quantity of fresh water from seawater. We installed beach seawater collector wells to develop the filtered seawater supply for desalination in a refinery. We came to a conclusion that the beach seawater collector well is one of the recommendable alternatives of seawater pre-treatment for desalination applications with lower operating cost and higher efficiency.