• Asia pacific journal of information systems
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• v.25 no.1
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• pp.61-81
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• 2015

Investment in research and development (R&D) is critical in the information technology (IT) firms, where newer and better technology is a quintessential goal that directly affects innovation and competitive advantage. This study investigates how R&D investment influences firm performance and value, and how the effect of R&D investment differs between IT hardware and software firms. We also analyze the relationship between firm age and R&D investment in order to identify learning effects on continuous R&D investment. The empirical investigation in this study, based on longitudinal archival data from 2001 to 2010, found a significant effect of R&D investment on firm performance in IT firms. Further, this study demonstrates causal relationship between firm age, and verifies that learning effects are present in R&D investment. Moreover, the results are found to differ between IT hardware and IT software firms.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.47.4-47.4
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• 2019

Recent observations on the double red clumps in the bulge validate the close connection in stellar populations between Galactic globular clusters (GCs) and the Milky Way (MW) bulge. Intriguingly, diverse phenomena observed in early-type galaxies (ETGs) and their GC systems are also indicating the similarities with Galactic GCs with multiple populations. Here, we present the population synthesis for the Galactic bulge and ETGs using stellar populations observed in the Galactic GCs with multiple populations. Our new models well explain observations of both the MW bulge and ETGs. Also, the inclusion of GC-originated population to the population synthesis model shows substantial impacts on the age-dating of stellar populations. The implication of this result for the interpretation of the formation history and the age-dating of ETGs will be discussed in detail.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.2
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• pp.29.1-29.1
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• 2018

With their complex structure that includes a thin disc, spiral arms, and often a bar, galaxies have been regarded as something beyond the human perceptions. Hence, the studies on galaxy formation in the 20th century have almost exclusively based on schematic scenarios. With markedly improved knowledge on cosmology over the last couple of decades, we have finally acquired a base from which galaxy formation can be studied from the first principles of physics. I review the modern history of the study of galaxy formation and present some preliminary results from the most recent numerical simulations that provide more realistic pictures of galaxy formation than was available ever before. In terms of galaxy formation, the age of scenarios is fading away, while the age of physical understanding is rising over the horizon.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.231-236
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• 2000

In this study, to present the use of the blase furnace slag fly ash derived from a large amount of the industrial products with the early strength reduction of it prevented, the initial strength is measured after a large quantity of fly ash and the required stimulus agent for the high development of the initial strength was added in blast furnace slag cement. As the results, in spite of the much addition of fly ash in blast furnace slag, the long-age strength of blast furnace slag cement was able to be improved by a proper amount of stimulus agent, and was as high as that of ordinary portland cement.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.50.3-50.3
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• 2020

We present deep UBVIc and Hα photometry for the young open cluster IC 1590 which is at the center of the HII region NGC 281. From Ha index, 39 Hα emission stars and 15 Hα emission candidates are selected. The reddening law toward IC 1590 is slightly abnormal (RV,cl = 3.6 ± 0.2). The distance modulus of IC 1590 obtained from the reddening-free (Q', QVλ) diagrams is 12.4 ± 0.1 mag (d = 3.02 ± 0.14 kpc), which is consistent with distance d = 2.91 ± 0.42 kpc from the parallax of Gaia DR2 catalogue within the error range. We also determined the age and mass function of IC 1590 using the stellar evolution models and PMS evolutionary tracks. The median age of PMS stars is 2.4 ± 2.2 Myr. The initial mass function (IMF) of IC 1590 is the Salpeter-type IMF with a slope of �� = -1.26 ± 0.14 for m > 1 M⊙ stars.

• Journal of Life Science
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• v.9 no.2
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• pp.182-193
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• 1999

In order to establish basic data of SAMP6 as an animal model for osteoporosis, present study has been designed to concentrate on the various biological aspects of SAMP6 such as growth index, hematology, blood biochemistry, biochemical characteristics, and bone and cortical thickness. Investigation period was for 15 months (3 months to 18 months of age) and biological characteristics have been examined throughout the study period. The results were summarized as follows : Decreased body weight of male SAMP6 was noticed from 7 months of age compared to from 18 months of age in female. Although there were no significant differences in organ weights, generally those of male mice were greater than those of females, especially in liver, kidney and lung. According to the analysis of blood biochemistry and hematology, the number of leukocytes in male mice was greater than that of female mice. There was a decrease in bone thickness in both male and female mice starting around from 7 months of age. Peak cortical thickness index was noticed at 5 months of age in both sexes. In femur, the highest $Ca^{2+}$ content for both sexes was noticed at 5 months of age, whereas the highest P$^{3+}$ content was noted at the age of 5 and 7 months in male and female mice, respectively. The contents of both elements were gradually decreased with age after peaks for both sexes. In summary, SAMP6 mice in KRICT colony show osteoporotic characteristics starting from 5 to 7 months of age, suggesting that at least 5 months of old animals should be used for studying the mechanism of osteoporosis or screening anti-osteoporosis drugs. This study also suggests that the cortical index thickness, $Ca^{2+}$ and P$^{3+}$ contents, and alkaline phosphatase activities can be used as indexes for drug screening.

• Korean Journal of Animal Reproduction
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• v.9 no.2
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• pp.124-132
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• 1985

The work was conducted to clarify the development of testes and histological changes of the Seminiferous tubules that is the Surface area, diameter, length of the tubules and the process of Spermatic cells growth in Seminal epithelium in relation to Sexual maturity of the meat-type cockerels. In addition the present experiments were planned to gain some basic data helpful for the study of reproductive physiology in meat-type cockerels and also to compare the histological changes Seminiferous tubules between egg and general purpose type cockerels. 1. The growth pattern of body weight, testes and comb was classified into four phase according to age. Body weight increased up to about 2kg at 2nd stage and to 4.3kg at 4th stage while at 3rd stage the growth rate of body weight was slower. The tests developed slowly until 22 weeks of age with no correlation to the growth of body weight. However, it grew rapidly afterwards, reaching 27.79$\pm$9.26gm and 42.46$\pm$5.33 gm at 24 and 28 weeks of age, respectively. The spermatozoa was seen first at 24 weeks of age. On the other hand, comb grew at similar rate to the testes, weighing on the average 21.78$\pm$6.48gm and 41.42$\pm$1.25gm at 24 and 28 weeks of age, respectively. 2. The areal rate of the Seminiferous tubules to interstitial tissues was 66%:34% at 2 weeks of age and the rate of the former increased in comparison to that of the latter as they grew older, becoming 94%:7% between at 24 weeks of age, when the testes weight increased rapidly too. 3. Diameter of Seminiferous tubules at 2 weeks of age was 42.76$\pm$1.04$\mu$m and then it gradually increased as the testes grew until 22 weeks of age, when it grew rapidly, increasing about 2.9 times of those of 2 weeks and at last increased up to 5 times at 24 weeks. 4. Length of Seminiferous tubules was 4.5cm at 2 weeks and then it was gradually increased. At 22 weeks old the length of tubules was icnreased rapidly being 321 meter and increased more than double, being 658 meter at 24 weeks old. 5. The cells of Seminal epithelium developed poorly and the number of cells were relatively few until 16 weeks old. Afterwards the cells increased rapidly in number and at 18 weeks, the number became twice of those of 16 weeks, reaching 140.43$\pm$43.6. At 24 weeks the cells increased more rapidly, reaching to 10 layers and Spermatozoa were first time seen.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.17 no.1
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• pp.13-18
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• 1981

Corrosion loss of the shell plates of the steel vessels are measured and analyzed on the thirty cargo vessels and fifteen lumber carriers of which nationality belong to Korea. Thickness of the shell plates were determined at the every observed points set along the fore and aft line and perpendicular to it, by use of the ultrasonic thickness meter. Difference of the thickness between the original and the determined shell plates are given as the corrosion loss at the present age. The results obtained are summarized as follows: 1. On the cargo vessels, (1) The total mean of the corrosion loss is greatest at the light waterline, in every age class of the vessels. (2) The total mean of the corrosion loss on the fore and aft line shows little difference, even though it is slightly greater at the fore part, in every age class of the vessels. (3) Corrosion loss along the perpendicular line grows greater in the order of freeboard, load waterline, upper bilge line and light waterline, within the 16 of the age of the observed vessels. Its order varies to freeboard, upper bilge line, load waterline and light waterline in the age of 35. Corrosion loss at the light waterline and load waterline, in the age of 35, shows 3 times of it at the freeboard, and it at the upper bildge line shows twice of it at the freeboard. The fact significates the corrosion grows rapidly around the waterline. 2. On the lumber carriers, (1) The total mean of the corrosion loss is greatest at the upper bilge line, in the every age class of the vessels. (2) Total mean of the corrosion loss on the fore and aft line shows little difference, even though it is slightly greater at the fore part, in every age class of the vessels. (3) Corrosion loss along the perpendicular line is least at the freeboard and greatest at the upper bilge line, and its value at the upper bilge line shows twice of it at the freeboard. 3. The total mean of the corrosion loss of the lumber carriers shows almost twice of the cargo vessels.

• Journal of the Korean Home Economics Association
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• v.42 no.8
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• pp.169-185
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• 2004

This study was performed to investigate the characteristics of meal patterns among Koreans of different age groups. The study subjects consisted of preschool children (PC), elementary school children (EC), high school students (HS), college students (CS), and adults over 30 years old living in Seoul and the surrounding areas. A dietary survey was conducted using 24-hour recall method from 1996-1998 and data were collected from 2392 subjects. The subjects over 30 years old were classified as 30∼49 years, 50∼69 years, and over 70 years. EC, HS, and CS groups consumed less than 20％ of their total energy intake from breakfast. PC and EC consumed over 30％ of their energy from snacks. In all age groups, the proportion of subjects who skipped a meal was highest for breakfast and lowest for dinner. Especially, 31.4％ of the CS group skipped breakfast. Breakfast and snacks provided higher quality meals than the others when each meal was assessed by the index of nutritional quality (INQ). Especially, lunch of the HS group, each meal of the EC group and subjects over 70 years of age had a lower diet quality than the others did. The major snack items for PC, EC, HS, and CS groups were milk, ice cream, and snack cakes, but those for subjects over 30 years of age were fruits. The PC group obtained 35.5％ of their energy from snacks, but the proportion of snack energy decreased with increasing age. PC and EC groups obtained a great proportion of calcium, vitamin B2, fat, and cholesterol intake from snacks. Snack foods provided 53.2％, 42.4％, 45.4％, and 24.6％ of those nutrients, respectively, for the PC group and 54.2％, 43.5％, 37.4％, and 26.8％, respectively, for the EC group. These results suggested that each age group had specific meal patterns. Especially, breakfast and snack intake seemed to complement overall diet quality. However, more intervention is needed to improve overall dietary nutrition, e.g., efforts to decrease fat and cholesterol proportion and increase breakfast consumption. These dietary characteristics among different age groups present foundation data for the development of methods to resolve the nutritional problems of each age group.

• Economic and Environmental Geology
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• v.42 no.6
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• pp.541-548
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• 2009

The Dongrae thermal water area located at the southeastern marginal part of the Korean Peninsula is one of the oldest hot springs in Korea. The Dongrae thermal water shows Na-Cl type of water chemistry, whereas the shallow cold groundwater is Ca(-Na)-$HCO_3$ type. In this paper, we discuss the age of the Dongrae hot spring, i.e. groundwater cycle among meteoric water-surface water-shallow groundwater-hot spring water. The $^{87}Sr/^{86}Sr$ ratios of the thermal water in Dongrae area range from 0.705663 to 0.705688 and are lower than those of groundwater, surface water and rain water as well as aquifer bearing granite. These Sr isotopic signatures in the Dongrae thermal water indicate that the circulation rate between thermal water and current meteoric water including groundwater, surface water and rain water in the Dongrae area should be very slow. The $^{14}C$ age of the Dongrae hot spring water range from $1,271{\pm}36$ BP(before present) to $2,467{\pm}36$ BP whereas that of the shallow groundwater is $-495{\pm}33$ BP. This suggests that the period of groundwater cycle among meteoric water, surface water, shallow groundwater and hot spring should be more than 1,270 years. Then, it also indicates that the present Dongrae hot spring may be a mixed water between the old thermal water heated for at least 1,270 years and the present shallow cold groundwater.