• Clean Technology
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• v.17 no.3
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• pp.244-249
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• 2011

We synthesized low molecular-weight polymers bearing hydrophobic and hydrophilic parts in a chain through $CO_2$/propylene oxide copolymerization. When hydrophilic poly (ethylene glycol) bearing -OH group (s) at the end group (s) was added as a chain transfer agent in the $CO_2$/propylene oxide copolymerization catalyzed by a highly active catalyst, block polymers were formed. If poly (ethylene glycol) (PEG) bearing -OH group only at an end was fed, PEG-block-PPC diblock copolymer was obtained. When PEG bearing -OH group at both ends was fed, PPC-block-PEG-block-PPC triblock copolymer was obtained. We confirmed formation of block copolymers by $^1H$-NMR spectroscopy and GPC studies.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.1B
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• pp.8-15
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• 2008

Cognitive radio technology enables to share the spectrum dedicated to primary users. In CR network, it is of primary concern to protect the primary users. Thus, it is required to periodically sense the spectrums occupied by primary users and adapt the communication parameters used by CR users to protect the primary users. However, it is inevitable to experience the hidden node problem due to the primary users, that are not detected by spectrum sensing. To perfectly protect the primary users, it is essential to address the hidden node problem in CR network. In this paper, we propose a new approach to handle the hidden node problem and evaluate the performance of proposed scheme.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.12 no.1
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• pp.58-71
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• 2019

This paper proposes architecture of a cognitive radio engine platform and the allowable frequency channel reasoning method that enables acquisition of the allowable channels for the military tactical network environment. The current military tactical wireless communication system is increasing need to secure a supplementary radio frequency to ensure that multiple wireless networks for different military wireless devices coexist, so that tactical wireless communication between the same or different systems can be operated effectively. This paper presents the allowable frequency channel reasoning method based on cognitive radio engine for realizing DSA(Dynamic Spectrum Access) as an optimal available frequency channel. To this end, a case-based allowable frequency channel reasoning method for cognitive radio devices is proposed through modeling of primary user's traffic status and calculation of channel occupancy probability. Also through the simulation of the performance analysis, changing rate of collision probability between the primary users' occupancy channel and the available channel acquisition information that can be used by the cognitive radio device was analysed.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• v.15 no.2
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• pp.143-151
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• 2004

Objectives : Child and adolescent onset obsessive compulsive disorder(C-OCD) is known to be associated with poor drug response, high comorbid rate and strong genetic tendencies. Till now studies for C-OCD have been very rare in Korea. We conducted this study to investigate the informations about clinical features, familial psychiatric loading, treatment profiles and course of server C-OCD from the retrospective analysis of inpatient data of Seoul National University Children's Hospital. Method : Retrospective chart review and data analysis was performed. Twenty(male 16 : female 4) patients with final C-OCD diagnosis by DSM-IV at discharge from 1994 to 2002 were found and their medical chart, psychological data, family interview data and nursing reports were collected and analyzed. Results : 1) The sex ratio of C-OCD was male dominant(4:1). 2) Phenomenological, most common obsession was pathologic doubt, contamination fear, followed by aggressive obsession, need for symmetry, sexual obsession, most common compulsion was checking and washing, followed by breathing, movement, symmetry, repetitive asking, hoarding, mental compulsion. 3) Most common comorbid diagnosis was depression. Other axis-I diagnosis associated OCD were anxiety disorder, tic disorder, conduct and oppositional defiant disorder and psychosis. 4) Regarding psychiatric familial loadings, 17 patients(85%) had relatives with psychiatric disorders, OC-spectrum disorders(OCD or OCPD) were found in 9 patients(45%). 5) The majority of patients(75%) have received SSRI and antipsychotics treatment. The response rate above 'moderate improved" by CGI was 75%. 6) During follow-up period in outpatient clinic, five patients(25%) showed continuous complete remission, 10 patients (50%) did residual symptoms with chronic course. Conclusion : This seems to be the first systemic investigation of severe pediatric OCD patients in Korea. The children & adolescents with severe OCD in inpatient-setting showed the high comorbid rate, familial psychiatric loading, and combined pharmacotherapy with antipsychotics, As for symptoms, high rate of aggressive-sexual obsession and atypical compulsions like breathing and moving was reported in this study. Severe pediatric OCD patients, however, responded well to the combined SSRI and antipsychotics regimen.

• The Journal of the Korea Contents Association
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• v.20 no.3
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• pp.613-626
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• 2020

This study reconsiders covenant theology through the relationship between law and grace. In order to do this, it first evaluates whether the Sinaitic Covenant is a covenant of grace or a covenant of works. This has been in discussion for a long period of time among theologians, yet is far from settled. Traditional studies form a wide spectrum, which can be divided into at least four major branches. First, the Sinaitic Covenant is the same as the covenant of grace. Second, the Sinaitic Covenant is the same as the covenant of works. Third, the Sinaitic Covenant forms a third, independent category of covenant. Fourth, the Sinaitic Covenant exists in harmony with the covenant of grace. Each category is summarized along with its representative proponents. Also, even though the term covenant of works is not accepted as prevalently among modern theologians, observations is made on how each category connects to and continues in modern theological discussions regarding law. Special emphasis is given to the fourth category and the fourth perspective on law with respect to how they differ from the others in viewing the relationship between law and gospel. Moreover, recognizing that the unique understanding of the fourth view grows out of a careful observation of the Biblical text, the structural similarities between the Sinaitic Covenant and other Biblical covenants are compared based on the Biblical text. Based on this comparison, it is observed that God's grace and human duty coexist in several Bible covenants including the Sinaitic and New Testament covenants. From this observation, it is proved that conditionality regarding covenant fulfillment exists in them all. This conditionality does not entail from exclusiveness on the part of God, but from the weakness on the part of humans. However, some unconditional covenants, albeit few in number, can be found in the Bible. Therefore, the difference between unconditional covenants and conditional covenants is discussed. Lastly, the proper place and role of grace in covenants is studied.

• Journal of Korean Library and Information Science Society
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• v.48 no.1
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• pp.373-396
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• 2017

The purpose of this study was to examine the trends of qualitative research in four representative journals in Korean LIS from 1970 to 2016. 73 papers(1.4%) were analyzed focusing on publication year, subject areas, research purposes, authors, qualitative methods, research participants, data collection methods, data analysis methods, and methods of validation. The findings are as follows: 1) Information behaviour(39.7%) was the most researched topics, followed by librarians work(20.5%), and bibliotherapy & reading education(13.6%). 2) The most frequently used research purpose was for understanding experiences(60.2%) and for improving current state(30.1%). 3) 'Grounded theory'(13.6%) and 'phenomenology'(10.9%), 'case study'(10.9%), were used frequently, while 'non-specified qualitative method' was 26.0% and 'not indicated' was 21.9%. 4) Librarians (41.0%) were the most researched participants, followed by professionals(13.6%). To collect qualitative data, in-depth interview(20.5%), interview(13.6%), and in-depth interview & internal documents(9.5%) were frequently used. There are 'loose qualitative research' group and 'scientific qualitative research' group. LIS researchers using qualitative research methods should consistently make efforts to increase qualitative theory and the philosophical assumptions, and to apply rigorous research method (data collection, analysis and interpretation, sampling, data saturation, validity and reliability). Institutionally, It is to provide 'qualitative research methods' course and to develop guidelines and standards for LIS qualitative research authors and reviewers.

• Korean Journal of Materials Research
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• v.9 no.7
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• pp.701-706
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• 1999

The crystal structure and magnetic properties of magnetic oxide system (F $e_2$ $O_3$)$_{5}$(A $l_2$ $O_3$)$_{4-x}$(G $a_2$ $O_3$)$_{x}$)SiO has been studied using X-ray diffraction and Mossbauer spectroscopy The changes of magnetic structure by the Ga ion substitution and the temperature variation have been investigated using Mossbauer spectroscopy, and the results are compared with those of the SQUIB measurements. Results of X-ray diffraction indicated that the crystal structures of the system change from a cubic spinel type to an orthorhombic via the intermediate region. This magnetic oxide system seems to be new kind of spinel type ferrites containing high concentration of cation vacancies. Various and complicated Mossbauer spectra were observed in the samples (x>0.2) at temperatures lower than room temperature. This result could be explained by freezing of the superparamagnetic dusters. On cooling and substitution, magnetic states of the system show various and multicritical properties. Unexpected dip in magnetization curves below 50K was observed in SQUID measurements. It was interpreted as an effect of spin canting including spin freezing or collective spin behavior.ior.r.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37B no.12
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• pp.1091-1101
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• 2012

Device-to-device (D2D) communication is expected to offer local area services with low transmit power and short link distance, even not via any infrastructures. These advantages will lead to the deployment of D2D systems in a massive scale, where the order of magnitude of D2D user density is higher than that of cellular user density. Network-assisted D2D systems, where D2D resources are managed by cellular networks, are unable to support the large number of D2D devices, due to the signaling overhead for control signals. In this case, no coordination can be an answer. This paper considers uncoordinated D2D systems, which is implemented with a number of D2D devices in a large scale. By analyzing the transmission capacity of D2D systems, we found a feasibility condition under which the uncoordinated D2D communications possibly coexist within cellular networks, sharing the uplink spectrum. In addition, we provide guidelines for the operational points of massive D2D communications, giving some knowledge about proper transmit power level and link distance of uncoordinated D2D.

• Journal of the Mineralogical Society of Korea
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• v.24 no.3
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• pp.151-164
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• 2011

Mineralogical and petrological characteristics were investigated on matrix of dense gray, vesiculate gray, brown and black pumice in Ulleung Island by using XRD, FT-IR, XRF, SEM and thermal analysis. According to the analysis, most of pumice matrix are amorphous and include very small amount of sanidine and anorthoclase. Since the adsorption moistures, which commonly observed as O-H peak in FT-IR spectrum, are not identified in thermal analysis, it seems reasonable to conclude that content of the adsorption moisture has very low level. Although pumice has a large specific surface area, with long time elapsed after eruption, pumice matrix shows very low degree of hydration alteration due to the low level of water content. In SEM images, most surfaces of pumice show morphological characteristics such as various shapes of vesicle with wrinkled and thin walls resulted from ductile coalescence. Dense gray pumice formed in the initial stage includes small vesicles less than $15{\mu}m$ in size with subangular to angular shapes, free of ovoid vesicle. These characteristics are interpreted to have related to the hydrous environment derived from phreato-plinian eruption. Submicron particles observed as amorphous alumina silicate assemblages in vesicle surface are considered as particles sticked to the matrix surface through rapidly cooling process during ascent of alkali phonolitic magma. It indicates that these particles coexisted partly with crystallized alkali feldspar.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.7
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• pp.1546-1553
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• 2015

In cognitive radio technology, the overall capacity of communications systems can be improved without allocating additional bands by allowing secondary system to utilize the band when a primary system who has right to use the band does not utilize it. Therefore, spectrum sensing to determine the existence of primary system is utmost important in the cognitive radio technology. In this work, we consider a novel cooperative spectrum sensing in cognitive cellular systems. Especially, we consider the case in which heterogeneous primary systems coexist, i.e., heterogenous transmission power and sensing requirement of primary system, such that only portion of users in cognitive cellular systems are able to detect the primary system. In this case, we propose new cooperative spectrum sensing with multiple sensing stages to properly detect the existence of primary systems in this kind of situations. Moreover, we analyze the performance of conventional cooperative spectrum sensing schemes such as OR-rule, AND-rule and MAJORITY-rule under the existence of heterogeneous primary systems. Finally, we investigate the performance of the proposed scheme through computer based simulations and show that the existence of primary systems can be determined accurately by using our proposed scheme.