• Korean Management Science Review
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• v.30 no.1
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• pp.73-89
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• 2013

This paper develops an investment algorithm based on Markowitz's Portfolio Selection Theory, using historical stock return data, and empirically evaluates the performance of the proposed algorithm in the U.S. and the Hong Kong stock markets. The proposed investment algorithm is empirically tested with the 30 constituents of Dow Jones Industrial Average in the U.S. stock market, and the 30 constituents of Hang Seng Index in the Hong Kong stock market. During the 6-year investment period, starting on the first trading day of 2006 and ending on the last trading day of 2011, growth rates of 12.63% and 23.25% were observed for Dow Jones Industrial Average and Hang Seng Index, respectively, while the proposed investment algorithm achieved substantially higher cumulative returns of 35.7% in the U.S. stock market, and 150.62% in the Hong Kong stock market. When compared in terms of Sharpe ratio, Dow Jones Industrial Average and Hang Seng Index achieved 0.075 and 0.155 each, while the proposed investment algorithm showed superior performance, achieving 0.363 and 1.074 in the U.S. and Hong Kong stock markets, respectively. Further, performance in the U.S. stock market is shown to be less sensitive to an investor's risk preference, while aggressive performance goals are shown to achieve relatively higher performance in the Hong Kong stock market. In conclusion, this paper empirically demonstrates that an investment based on a mathematical model using objective historical stock return data for constructing optimal portfolios achieves outstanding performance, in terms of both cumulative returns and Sharpe ratios.

• Microbiology and Biotechnology Letters
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• v.18 no.4
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• pp.394-400
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• 1990

Maximization of productivity of recombinant cell fermentations requires consideration of the inverse relationship between the host cell growth rate and product formation rate. The problem of maximizing a weighted performance index was solved by using optimal control theory for recombinant E. coli fermentation. Concentration of a growth inhibitor was used as a control variable to manipulate the specific growth rate, and consequently the cloned-gene expression rate. Using a simple unstructured model to describe the main characteristics of this system, theoretical analysis showed that the optimal control profile results in an initial high growth rate phase followed by a low growth rate and high product formation rate phase. Numerical calculations were done to determine optimal switching times from the growth to the production stage for two representative cases corresponding to different dependency of the product formation rate on the growth rate. For the case when product formation rate is sensitive to the specific growth rate, the optimized operation yields about 60% increase in the final product concentration compared with a simple batch fermentation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1995.05a
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• pp.47-49
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• 1995

We report the spectroscopic properties of column-III nitrifies of GaN, GaInN, and AlGaN. The column-III nitride semiconductors are promising materials to realize the current-injection-type blue-and ultraviolet (UV)-light-emitting devices with high performance. To acheive the lasing with low threshold, the devices are must constructed to double heterostructure by succesive epitaxial growth technique, and we must confine the carriers in the potential barrier and optical confinement in wave guide between barrier and active layers has different refractive index. The refractive index of column-III nitride semiconductors, however, are rarely reported. The measured refractive index was 2.9, and the observed characteristic peak near the enrgy gap was analysed using a dielectric function and may due to excitonic contribution.

• Journal of Forest and Environmental Science
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• v.33 no.1
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• pp.22-32
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• 2017

An experiment was set to assess the effect of mixed plantings on initial growth and biomass yield of two common plantation tree species of Bangladesh namely Acacia auriculiformis (A) and Gmelina arborea (G). Study was carried out in the nursery bed of the Seed Research Laboratory and Nursery of Institute of Forestry and Environmental Sciences, Chittagong University (IFESCU), Bangladesh during February to November, 2015. The treatments consisted of two pure planting plots (100% A and 100% G) and five mixed planting plots (50%A: 50%G, 35%A: 65%G, 25%A: 75%G, 65%A: 35%G and 75%A: 25%G) of these two species. In nursery, seedlings were raised in a randomized blocks with four replicates of seven treatment plots. Periodic increments on height (cm), collar diameter (cm) and leaf/phyllode number of the seedlings was taken in every month and continued up to 10 months. The growth and biomass yield of seedlings were measured 10 months after the first seed was emerged. The effects of mixed plantation on growth and biomass were compared to that of seedlings grown in pure plantation. At the age of 10 months it was found that G. arborea seedlings were significantly tallest (240.13 cm) when planted with A. auriculiformis in a proportion of 25%A: 75%G, whereas A. auriculiformis were tallest in the pure 100% A plot, with an average mean height of 135.36 cm. Maximum collar diameter (1.38 cm) was recorded for G. arborea in the mixed plots 75%A: 25%G. Fresh and dry weight of shoots and roots of the seedlings were found significantly (p<0.05) highest in 50%A: 50%G plot for G. arborea. G. arborea also showed highest quality index when mixed with A. auriculiformis in a proportion of 50:50, with an average value of 8.96. The results revealed a positive correlation between seedling growth and various planting patterns.

• Journal of Forest and Environmental Science
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• v.30 no.1
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• pp.120-125
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• 2014

Halophytes are plants of saline habitats that grow under conditions that may vary in extremes of temperatures (freezing to very hot), water availability (drought to water logging) and salinity (mild to almost saturation). Halophytes may also face sudden micro-environmental variations within their habitats. In this study, we examine some of the factors that determine the ability of seeds of Artemisia fukudo to germinate when conditions are optimal for seedling growth and survival. Germination percentage was the highest at 77.5% when treated in 0% seawater and seedling growth was best in 0% seawater plug cell tray. Physiological quality (chlorophyll contents) and mean germination time were best in the condition in which seeds were treated with 0% seawater (control). Germination performance index in the control group showed the highest value to 3.8. Seedling growth, seedling vigor index in the length of seedling growth andthe relative growth rate were the highest values of 0.76 cm, 1.43, 0.0099, respectively.

• Applied Chemistry for Engineering
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• v.32 no.4
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• pp.423-430
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• 2021

In order to evaluate the fire risk and fire risk rating of wood for construction materials, this study focused on fire performance index-III (FPI-III), fire growth index-III (FGI-III), and fire risk index-IV (FRI-IV) according to Chung's equations-III and -IV. Western red cedar, needle fir, ash, and maple were used as the specimens. The fire characteristics were investigated using a cone calorimeter (ISO 5660-1) equipment on the specimen. The FPI-III measured after the combustion reaction was 0.86 to 12.77 based on polymethylmethacrylate (PMMA). The FGI-III was found to be 0.63 to 5.26 based on PMMA. The fire rating according to the FRI-IV, which is the fire rating index, was 0.05 to 6.12, and the western red cedar was 122.4 times higher than that of the maple. The fire risk rating according to the FRI-IV increased in the order of maple, ash, needle fir, PMMA and western red cedar. The CO peak concentration of all specimens was measured as 103 to 162 ppm, and it was 2.1 to 3.2 times higher than 50 ppm, the permissible exposure limits of the US occupational safety and health administration. Materials such as western red cedar, which have a low bulk density and contain a large amount of volatile organic substances, have a low FPI-III and a high FGI-III, so they have a high fire risk rating.

• Applied Chemistry for Engineering
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• v.35 no.1
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• pp.29-36
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• 2024

The fire risk and fire safety of four types of wood were comprehensively evaluated according to Chung's equation-XII. White ash, willow, fraxinus mandshurica, and sagent cherry trees were selected as test specimens. A cone calorimetery (ISO 5660-1) was used to examine the combustion characteristics of the test piece, and finally, the fire risk rating (FRR) was predicted using the fire risk index-XII (FRI-XII). The predicted fire performance index-X (FPI-X) and fire growth index-X (FGI-X) ranged from 469.03 to 1109.73 s²/kW and 0.0009 to 0.0280 kW/s², respectively. Additionally, the fire performance index-XI (FPI-XI) and fire growth index-XI (FGI-XI) ranged from 0.41 to 0.97 and 1.11 to 3.11, respectively. The fire risk index-XII (FRI-XII), representing a fire risk rating, showed that the fire risk of frasxinus mandsurica tree (FM) was very high at 7.60 (fire risk rating: D). And it was compared with Chung's equation-IX, fire risk index-IX (FRI-IX). The fire risk ratings according to FRI-IX and FRI-XII were generally high for willow and frasxinus mandsurica trees. Additionally, the results of FRI-XII and FRI-IX had a similar relationship, and the size of each fire safety rating closely matched each other.

• Survey Research
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• v.7 no.1
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• pp.55-84
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• 2006

This study has classified development stages (Embryonic-Growth-Maturity) of mobile telecommunication industry based on Industry Life Cycle theory. There are two steps to be analyzed in this study, In the first step, cluster was investigated through cluster analysis using mobile density to categorize development stages of mobile telecommunication industry. In the second step, we compared on indexes of market structure, market efficiency and market performance to find out characteristics of each stage of development. The results are as follows. First, HHI is higher at embryonic stage than at growth and maturity stages, Second, ARPU(Average Revenue Per User) and RPM(Revenue Per Minute) are getting higher as the stages move on. Third, EBITDA margins, an index of market performance, is decreasing along the three stages. Finally, this study presents a clue to define the stage of development of mobile telecommunication industry and build a proper strategy for the market change.

• Journal of Digital Convergence
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• v.17 no.10
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• pp.169-176
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• 2019

Recently, the Korean economy is congested with Japan's economic retaliation, the US-China trade war, the Bank of Korea's 0.25% base rate cut and Korea's economic growth forecast revision. The purpose of this study is to analyze the KOSPI, CPI, Treasury bonds(3 years) Interest rate & sales performance of all industries, and examine the impact of each index on the KOSPI. The analysis period is from January 2003 to June 2019, and the effect of each index on the KOSPI is analyzed. In numerical analysis, we performed correlation coefficients and regression analysis. In the model analysis, the distribution, quadrant, scatter, box-plot and impulse response were examined. This study examined the volatility and dynamic characteristics of each index. As a result, the KOSPI showed a high correlation with sales and Treasury bonds, but showed a very low correlation with the CPI. The KOSPI will continue to be affected by sales and interest rates.

• Journal of Korea Port Economic Association
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• v.35 no.1
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• pp.77-96
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• 2019

Logistics and transportation are increasingly playing a crucial role in international trade relations. Logistics services provide sectoral connections within the local economy. The efficient logistics services facilitate the flow of products; besides ensuring safety and speed of movement, they can reduce the cost of cross-border trade. The Logistics Performance Index (LPI) evaluates the efficiency of customs, quality of transportation service, and infrastructure for overland and maritime transport in each country it covers. The objective of this article is to analyze the impact of the various LPI indicators of Korea's trading partners. The impact of LPI on trade varies according to the income level of the trading partners. The results show that an improvement in any of the components of the LPI can lead to significant growth in a country's trade flow. Exports to Korea will increase as the LPI of the trading partner country is higher. This index has a greater impact on the exports of low-income countries.