• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.8
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• pp.937-942
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• 2007

A new, systematic, simplified design procedure for quasi-Yagi antennas is presented. The design is based on the simple impedance matching among antenna components: i.e., transition, feed, and antenna. This new antenna design is possible due to the newly developed ultra-wideband transition. As design examples, wideband quasi-Yagi antennas are successfully designed and implemented in Ku- and Ka-bands with frequency bandwidths of 53.2% and 29.1%, and antenna gains of $4{\sim}5 dBi$ and $ 5{\sim}5.6 dBi$, respectively. The design method can be applied to other balanced antennas and their arrays.

• Korean Journal of Materials Research
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• v.8 no.3
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• pp.224-228
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• 1998

Phase transition kinetics of nonstoichiometric amorphous titanium oxide thin films deposited by reactive sputtering was investigated after cooling down with various rate followed by l0min.-3hrs. annealing at $500^{\circ}C$~$600^{\circ}C$ After short duration and fast cooling. Magneli was the only crystalline phase because the oxidation rates of $TiO_{2-x}$, could be relatively slower than that of crystallization. When the films were cooled slowly between $500^{\circ}C$~$300{\circ}C$, Magneli was transformed into an anatase and stabilized, but directly into a rutile under fast cooling. Because the rutile also prevailed after cooling from $600^{\circ}C$, it was concluded that the rutile phase could be formed directly from Magneli as well as converted from the anatase. Changes in volume and surface morphology were observed related to crystallization and oxidation processduring heat treatment.

• Animal Bioscience
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• v.37 no.2_spc
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• pp.337-345
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• 2024

Ruminants possess a specialized four-compartment forestomach, consisting of the reticulum, rumen, omasum, and abomasum. The rumen, the primary fermentative chamber, harbours a dynamic ecosystem comprising bacteria, protozoa, fungi, archaea, and bacteriophages. These microorganisms engage in diverse ecological interactions within the rumen microbiome, primarily benefiting the host animal by deriving energy from plant material breakdown. These interactions encompass symbiosis, such as mutualism and commensalism, as well as parasitism, predation, and competition. These ecological interactions are dependent on many factors, including the production of diverse molecules, such as those involved in quorum sensing (QS). QS is a density-dependent signalling mechanism involving the release of autoinducer (AIs) compounds, when cell density increases AIs bind to receptors causing the altered expression of certain genes. These AIs are classified as mainly being N-acyl-homoserine lactones (AHL; commonly used by Gram-negative bacteria) or autoinducer-2 based systems (AI-2; used by Gram-positive and Gram-negative bacteria); although other less common AI systems exist. Most of our understanding of QS at a gene-level comes from pure culture in vitro studies using bacterial pathogens, with much being unknown on a commensal bacterial and ecosystem level, especially in the context of the rumen microbiome. A small number of studies have explored QS in the rumen using 'omic' technologies, revealing a prevalence of AI-2 QS systems among rumen bacteria. Nevertheless, the implications of these signalling systems on gene regulation, rumen ecology, and ruminant characteristics are largely uncharted territory. Metatranscriptome data tracking the colonization of perennial ryegrass by rumen microbes suggest that these chemicals may influence transitions in bacterial diversity during colonization. The likelihood of undiscovered chemicals within the rumen microbial arsenal is high, with the identified chemicals representing only the tip of the iceberg. A comprehensive grasp of rumen microbial chemical signalling is crucial for addressing the challenges of food security and climate targets.

• Journal of Intelligence and Information Systems
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• v.22 no.1
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• pp.1-18
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• 2016

Owing to the extensive use of Web media and the development of the IT industry, a large amount of data has been generated, shared, and stored. Nowadays, various types of unstructured data such as image, sound, video, and text are distributed through Web media. Therefore, many attempts have been made in recent years to discover new value through an analysis of these unstructured data. Among these types of unstructured data, text is recognized as the most representative method for users to express and share their opinions on the Web. In this sense, demand for obtaining new insights through text analysis is steadily increasing. Accordingly, text mining is increasingly being used for different purposes in various fields. In particular, issue tracking is being widely studied not only in the academic world but also in industries because it can be used to extract various issues from text such as news, (SocialNetworkServices) to analyze the trends of these issues. Conventionally, issue tracking is used to identify major issues sustained over a long period of time through topic modeling and to analyze the detailed distribution of documents involved in each issue. However, because conventional issue tracking assumes that the content composing each issue does not change throughout the entire tracking period, it cannot represent the dynamic mutation process of detailed issues that can be created, merged, divided, and deleted between these periods. Moreover, because only keywords that appear consistently throughout the entire period can be derived as issue keywords, concrete issue keywords such as "nuclear test" and "separated families" may be concealed by more general issue keywords such as "North Korea" in an analysis over a long period of time. This implies that many meaningful but short-lived issues cannot be discovered by conventional issue tracking. Note that detailed keywords are preferable to general keywords because the former can be clues for providing actionable strategies. To overcome these limitations, we performed an independent analysis on the documents of each detailed period. We generated an issue flow diagram based on the similarity of each issue between two consecutive periods. The issue transition pattern among categories was analyzed by using the category information of each document. In this study, we then applied the proposed methodology to a real case of 53,739 news articles. We derived an issue flow diagram from the articles. We then proposed the following useful application scenarios for the issue flow diagram presented in the experiment section. First, we can identify an issue that actively appears during a certain period and promptly disappears in the next period. Second, the preceding and following issues of a particular issue can be easily discovered from the issue flow diagram. This implies that our methodology can be used to discover the association between inter-period issues. Finally, an interesting pattern of one-way and two-way transitions was discovered by analyzing the transition patterns of issues through category analysis. Thus, we discovered that a pair of mutually similar categories induces two-way transitions. In contrast, one-way transitions can be recognized as an indicator that issues in a certain category tend to be influenced by other issues in another category. For practical application of the proposed methodology, high-quality word and stop word dictionaries need to be constructed. In addition, not only the number of documents but also additional meta-information such as the read counts, written time, and comments of documents should be analyzed. A rigorous performance evaluation or validation of the proposed methodology should be performed in future works.

• Journal of the Korean Applied Science and Technology
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• v.17 no.3
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• pp.158-166
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• 2000

A conductimetric study of foam formed from mixture of the protein, ${\beta}-lactoglobulin$, and the nonioinc surfactant, SML, revealed that their stability was reduced at concentrations of SML in the range $3{\sim}10mM$. The interaction of SML with ${\beta}-lactoglobulin$ was investigated by fluorimetry and a dissociation constant of $0.2{\mu}M$ was calculated for the complex. Surface tension studies confirmed the presence of interaction between the two components and provided evidence for the progressive displacement of ${\beta}-lactogloblin$ from the air/water interface with increasing SML concentration. Experiments using air-suspended microscopic thin liquid films revealed transitions in the chainage characteristics and thickness of the film at SML concentrations below that which resulted in destabilization of the foam. However, measurements of surface mobility of fluorescent-labeled ${\beta}-lactoglobulin$ by a photobleaching method identified that a transition to a mobile system occurred at a SML concentration which correlated with the onset of instability in the disperse phase. The results would indicate that maintenance of the viscoelastic properties of the surface is paramount importance in determining the stability of interfaces comprising mixtures of protein and surfactant.

• Macromolecular Research
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• v.9 no.2
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• pp.116-121
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• 2001

A series of poly(1,4-phenylenevinylene-alt-3-alkyl-2,5-thienylenevinylene)s (alkyl = hexyl [PPV-alt-6-TV] and octyl (PPV-alt-8-TV] group) have been synthesized by the Heck coupling reaction. These polymers were characterized using $^1$H-NMR, FT-IR spectroscopy, and thermogravimetric analysis (TCA). They are solvent processible and have obviously copolymeric structure. The photophysical properties of the polymers were investigated using UV-visible and steady-state photoluminescence(PL) spectroscopy. We studied the change of light-emitting properties by incorporating the thiophene group into the PPV polymer backbone using alternating copolymer system. The properties of two synthesized polymers are very similar, but they exhibited apparent changes of light-emitting properties compared with other PPV backbone based polymers. The broad absorption bands from 350 to 570 nm are due to $\pi$-$\pi$* transitions of the polyconjugated systems. The absorption maxima of the two polymers were found at about 452 and 448 nm for PPV-alt-6-TV and PPV-alt-8-TV, respectively. The copolymers showed broad PL spectra between 550 and 700 nm without vibronic bands and PL emission maxima of PPV-alt-6-TV and PPV-alt-8-TV are about 620 and 605 nm, respectively. The copolymers exhibited the red emission (PPValt-6-TV), but more red shifted emissions are needed to obtain real red color.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.6
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• pp.43-48
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• 2008

Power consumption during test can be much higher than that during normal operation since test vectors are determined independently. In order to reduce the power consumption during test process, a new BIST(Built-In Self Test) architecture is proposed. In the proposed architecture, test vectors generated by an LFSR(Linear Feedback Shift Resister) are transformed into the new patterns with low transitions using Bit Generator and Bit Dropper. Experiments performed on ISCAS'89 benchmark circuits show that transition reduction during scan testing can be achieved by 62% without loss of fault coverage. Therefore the new architecture is a viable solution for reducing both peak and average power consumption.

• Journal of IKEEE
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• v.27 no.4
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• pp.573-578
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• 2023

This paper introduces a new locking technique applicable to high-performance digital Phase-Locked Loops (DPLL). The study employs additional thermometer codes to reduce quantization errors in LC-based Digital Controlled Oscillators (DCO). Despite not implementing the entire DCO codes in thermometer mode, this method effectively reduces quantization errors through enhanced linearity. In the initial locking phase, binary codes are used, and upon completion of locking, the system transitions to thermometer codes, achieving high frequency linearity and reduced jitter characteristics. This approach significantly reduces the number of switches required and minimizes the oscillator's area, especially in applications requiring low DCO gain (Kdco), compared to the traditional method that uses only thermometer codes. Furthermore, the jitter performance is maintained at a level equivalent to that of the thermometer-only approach. The efficacy of this technique has been validated through modeling and design at the RTL level using SystemVerilog and Verilog HDL.

• Korean Journal of Mineralogy and Petrology
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• v.35 no.1
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• pp.65-73
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• 2022

The proper estimation of physical and chemical properties of Earth materials and their structures at high pressure and high temperature conditions is key to the full understanding of diverse geological processes in Earth and planetary interiors. Multi-anvil press - high-pressure generating device - provides unique information of Earth materials under compression, mainly relevant to Earth's upper mantle. The quantitative estimation of the relationship between the oil load within press and the actual pressure conditions within the sample needs to be established to infer the planetary processes. Such pressure-load calibration has often been based on the phase transitions of crystalline earth materials with known pressure conditions; however, unlike at high temperature conditions, phase transitions at low (or room) temperatures can be sluggish, making the calibration at such conditions challenging. In this study, we explored the changes in Al coordination environments of permanently densified pyrope glasses upon the cold compression using the high-resolution ²⁷Al MAS and 3QMAS NMR. The fractions of highly coordinated Al in the cold compressed pyrope glasses increase with increasing oil load and thus, the peak pressure condition. Based on known relationship between the peak pressure and the Al coordination environment in the compressed pyrope glasses at room temperature, we established a room temperature pressure-load calibration of the 14/8 HT assembly in 1,100-ton multi-anvil press. The current results highlight the first pressure-load calibration of any high pressure device using high-resolution NMR. Irreversible structural densification upon cold compression observed for the pyrope glasses provides insights into the deformation and densification mechanisms of amorphous earth materials at low temperature and high pressure conditions within the subducting slabs.

• Journal of The Korean Astronomical Society
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• v.34 no.3
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• pp.157-166
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• 2001

The molecular cloud associated with the H II region S301 has been mapped in the J = 1-0 transitions of $^{12}CO$ and $^{13}CO$ using the 13.7 m radio telescope of Taeduk Radio Astronomy Observatory. The cloud is elongated along the north-south direction with two strong emission components facing the H II region. Its total mass is $8.7 {\times} 10^3 M{\bigodot}$. We find a velocity gradient of the molecular gas near the interface with the optical H II region, which may be a signature of interaction between the molecular cloud and the H II region. Spectra of CO, CS, and HCO+ exhibit line splitting even in the densest part of the cloud and suggests the clumpy structure. The radio continuum maps show that the ionzed gas is distributed with some asymmetry and the eastern part of the H II region is obscured by the molecular cloud. We propose that the S301 H II region is at the late stage of the champagne phase, but the second generation of stars has not yet been formed in the postshock layer.