• Journal of Korea Foundry Society
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• v.9 no.6
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• pp.483-489
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• 1989

In the stable eutectoid transformation of austenite in ductile cast iron, ferrite forms around the graphite spheroid. As carbon diffuses through the ferrite ring, the graphite spheroid must eularge and the ferrite ring must deform plastically to accomodate this growth. A model has been proposed to clarify this mechanism. The alloying effects of molybdenum, nickel and copper were studied in a series of heats cast into a range of casting section sizes. Regression analysis was used to illustrate the effects of alloying and cooling rate on the microstructure of ductile cast iron.

• The Korean Journal of Nuclear Medicine
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• v.36 no.4
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• pp.209-223
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• 2002

By considering the biological properties of a tumor, it should be possible to realize better results in cancer therapy. PET imaging offers the opportunity to measure tumor growth non-invasively and repeatedly as an early assessment of response to cancer therapy. Measuring cellular growth instead of energy metabolism showed offer significant advantages in evaluating therapy. Thymidine and its derivative nucleoside compounds can be changed to mono, di- and tri- phosphate compounds by thymidine kinase and then be incorporated into DNA. Their bindings are increased in highly proliferating cells due to the high DNA synthesis rate. To evaluate cell proliferation, many kinds of thymidine and uridine derivatives have been labeled with positron emitter and radioactive iodine. Compared to radiopharmaceuticals which have radioisotope labeled base ring such as pyirmidine, the radiopharmacuticals which have radioisotope labeled sugar ring are more stable in vivo and have metabolic resistance. The biological properties such as DNA incorporation ratios are highly dependent on their chemical structures and metabolic processes. This overview describes synthesis of radiopharmaceuticals and their biological properties for imaging of tumor cell proliferation.

• ETRI Journal
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• v.26 no.4
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• pp.332-343
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• 2004

One of the recent and most significant technical properties can be expressed as "digital convergence," which is helping lead the technical paradigm into a ubiquitous environment. As an initial trial of realizing a ubiquitous environment, the convergence between broadcasting and telecommunication fields is now on the way, where it is required to develop a scalable video coding scheme for one-source and multi-use media. Traditional scalable video coding schemes have, however, limitations for higher stable picture quality especially on the region of interest. Therefore, this paper introduces an adaptive scanning method especially designed for a higher regional-stable picture quality under a ubiquitous video coding environment, which can improve the subjective quality of the decoded video by most-preferentially encoding, transmitting, and decoding the top-priority image information of the region of interest. Thus, the video can be more clearly visible to users. From various simulation results, the proposed scanning method in this paper can achieve an improved subjective picture quality far better than the widely used raster scan order in conventional video coding schemes, especially on the region of interest, and without a significant loss of quality in the left-over region.

• Journal of the Korean Society of Safety
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• v.11 no.4
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• pp.84-89
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• 1996

The Oxidation of aflatoxin $G_1$ ($AFG_1$) with ozone in chloroform solvent gave the stable ozonide into ozonization of the double bond in the terminal furan ring, and this reaction have been carried out for 3hr at -78. 5$^{\circ}C$. The chloroform solvent was removed in a stream of nitrogen and the residue was separated by elution chromatography(EC). The structure of this compound have been identified by using MS, $^1H-NMR$, $^l3C-NMR$ and I. R spectroscopy, respectively. This compound was formed the normal stable AFG$_1$-ozonide into spontaneous rearrangement after unstable ozonide according to sigmatropic rearrange ment dependent upon cyclo addition by ozone.

• Electronics and Telecommunications Trends
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• v.34 no.5
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• pp.91-98
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• 2019

Optical frequency comb generators have been investigated as a signal source capable of generating highly stabilized ultrafast pulse lasers. The precise control of the optical frequency comb spacing by RF clock signals has led to a revolutionary paradigm shift in the precise measurement of time and frequency. Optical frequency combs also have advantages such as stable frequency spacing, stable number of lines, and robustness. Owing to these characteristics, optical frequency combs have been applied to the fields of high precision optical clock, communication, spectroscopy, waveform generation, and astronomy. In this article, we introduce the properties (i.e., generation methods, advantages, and so on) of various optical frequency combs, and discuss the expected future technological trends and applications.

• Proceedings of the Korean Magnestics Society Conference
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• 2002.12a
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• pp.186-187
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• 2002

Recently, there has been much interest in magnetic thin film patterned in submicron scale because of possible ultrahigh density storage media or logical device applications [1-3]. Various geometries such as rectangle, circle, ring and ellipse type dots have been studied to find the shape showing stable switching behavior from repeated cycles. However, rectangle and circle types may not be suitable for device applications because they have two uncontrollable different magnetization reversal modes: C state and S state, resulting in different coercivity and irreproducible switching[4]. (omitted)

• Bulletin of the Korean Chemical Society
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• v.20 no.5
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• pp.531-534
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• 1999

Irradiation (300 nm UV light) of dibenzoylmethane and 1,4-naphthoquinone in dichloromethane gave 1,5-dike-tone as the major product, along with β-hydroxyketone as the minor product. Anthraquinone and anthrone also added photochemically to dibenzoylmethane to give 1,5-diketones as the major products. In contrast, tetrahalo-1,4-benzoquinones added to dibenzoylmethane to give two types of 1,5-diketones via oxetane and cyclobutane intermediates. Comparison of the potential energy values of the photoproducts reveals that the 1,5-diketones are more stable than the corresponding oxetanes or cyclobutanes due to the ring-strain of the bicyclic compounds.

• Bulletin of the Korean Chemical Society
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• v.14 no.5
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• pp.631-635
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• 1993

The polarizability and the transition state energy of a cephalosporin are assumed to be theoretical indices of the permeability through the outer membrane and of reactivity of ${\beta}$ -lactam ring with penicillin binding proteins, respectively, in Gram-negative bacteria. They are computed by AM1 method and used as variables of quantitative structure-activity relationship study. The results justify quadratic dependence of the activity on the variables. The intersection of difference volumes between $\beta-lactamase$ stable cephalosporins and unstable ones manifests that the steric hindrance of 7-side chain is responsible for the ${\beta}$ -lactamase stability.

• Bulletin of the Korean Chemical Society
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• v.29 no.6
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• pp.1125-1130
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• 2008

A series of dihydroxylated chalcone derivatives with diverse substitution patterns on a phenyl ring B and the para-substituents on a phenyl ring A were prepared, and their radical scavenging activities were evaluated by simple DPPH test to determine quantitative structure-activity relationship in these series of compounds. The chalcone compounds with the ortho- (i.e. 2',3'- and 3',4'-) and para- (i.e. 2,5'-) substitution patterns show an excellent antioxidant activities (80-90% of control at the concentration of 50 $\mu$M) which are comparable to those of ascorbic acid and $\alpha$ -tocopherol as positive reference materials. On the contrary, the compounds with meta- (i.e. 2',4'-, 3',5'-) substitution pattern demonstrate very dramatic decrease in activities which are around 25% of the control even at the concentration of 200 $\mu$ M (IC50 > 200 $\mu$ M). These dramatic differences could be interpreted in terms of the ease formation of fairly stable semiquinone radicals from the ortho- and parasubstituted chalcone molecules through facilitating electron delocalization. Our results indicate that the substitution patterns of two hydroxyl groups on ring B are very important structural factors for their radical scavenging activity enhancement. Meanwhile, the substituents at para-position of the phenyl ring A of chalcones have no influence on the activity.

• Korean Journal of Breeding Science
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• v.40 no.1
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• pp.80-83
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• 2008

A new pink gerbera (Gerbera hybrida Hort.) cultivar 'Summer Ring' was developed from a cross between 'Grandeur' and 'Nova Zembla' followed by seedling and line selections at the Flower Breeding Research Institute, Gyeongnam Agricultural Research and Extension Services (ARES) in 2005. Characteristics of the new cultivar were evaluated three times from 2003 to 2004. 'Summer Ring' has semi-double type mini flower in good harmony with pink (RHS, 56-D) ray floret and green center. It has good stable flower shape and strong peduncle, and its vase life was 14.7 days. The average yield of 'Summer Ring' flower was 69 per plant/year in greenhouse yield trails during 2003 and 2004. This cultivar was registered for commercialization in 2005. Commercial production of 'Summer Ring' could be possible throughout the country under greenhouse condition.