• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.6
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• pp.514-520
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• 2002

In this paper, the study of a design and fabrication of the receiver MMIC mixer for L-band application is described. The mixer is composed of active LO and RF balun to integrate on a chip and applied a newly proposed bias circuit to compensate the process variations of active devices. The conversion gain of the mixer is -14 dB, IIP3 is approximately 4 dBm and port-to-port isolation is over 25 dB. The newly proposed bias circuit is composed of a few FETs and resistors, and can compensate the variation of the threshold voltage by the process variations, temperature changes and etc. The designed chip size is $1.4\;mm{\times}1.4\;mm$.

• Journal of Gifted/Talented Education
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• v.9 no.1
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• pp.85-126
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• 1999

본 연구에서는 4세 영재아들이 유아교육 기관에서 일반 유아들과 생활하는 과정을 문화기술적(ethnographic) 연구방법을 통하여 분석해 보고자 하였다. 본 연구는 서울시에 위치한 유치원의 만 4세 남자 유아와 전주시에 위치한 어린이집에 다니는 만 4세 여자 유아를 대상으로 선정하였다. 1999년 4월 2일 - 1999년 6월 18일까지 14주 동안 진행되었다. 관찰은 1주일에 2-3회 1시간 정도씩 참여하였다. 교사와의 면담은 6차례에 걸쳐 총 2시간 10분 동안의 면담을 녹음하여 분석하였다. 부모와의 면담은 4차례에 걸쳐 실시되었으며, 영재아를 지도해 본 교사 6명에게 설문지를 실시하였다. 수집된 사례는 부호화하고 범주화 한 뒤 분석하였다. 본 연구는 결과를 요약하면 다음과 같다. 첫째, 유아교육기관에서 4세 영재아들은 풍부한 지식과 우수한 기억력, 부한한 상상력, 문제해결 능력과 논리적 추리 능력, 흥미와 집착, 다른 장난과 배회, 포기와 합리화의 특징을 가지고 있었다. 둘째, 4세 영재아들의 또래 친구들과 자기 중심적 사고와 자기 주장, 갈등과 화합, 놀이 주도자와 창안자의 관계를 갖고 있었다. 셋째, 부모들은 자녀에 대해 강력한 지지자, 정원사와 같은 신념과 양육태도를 가지고 있었다. 넷째, 교사들을 영재아 지도에 대해 놀라운 아이, 방해하는 아이로 인식하였으며, 논리적 설득과 중재, 제재와 격리의 방법으로 지도 하고 있었으며, 수용 혹은 지나친 인정, 그리고 방치하는 것에 대해 갈등을 갖고 있었다.

• Journal of the Korean Society of Clothing and Textiles
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• v.28 no.12 s.138
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• pp.1545-1553
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• 2004

This study assumes a bidimensional model of acculturation theory in order to understand the acculturation patterns of Korean-Americans and their fashion and shopping behavior. Bidimensional models of acculturation suggest that acculturating individuals may possess the components of both the heritage culture and the new, host culture. A combination of email and paper and pencil surveys was conducted with a convenience sample of Korean-Americans who are living in Seattle and vicinity area (n=108). The questionnaire included questions related to the respondents' and their parents' demographic information, the respondents perceived relationship with their parents, self-reported ethnic identification, ethnicity-related behaviors/attitudes, clothing involvement, shopping motivations, and fashion reference groups. The results support the bidimensional models of acculturation process as opposed to the linear model. Three different groups among Korean-Americans based on their ethnic identification pattern were found: a group with dominant Korean identity(Segregation group), a group with dominant American identity(Assimilation group), and a group with dual identity(Integration group). According to the results of MANOVA and subsequent Duncan and Scheffe tests, the Integration group showed distinct characteristics from Segregation group or Assimilation group, in terms of their ethnicity-related behaviors/attitudes, clothing involvement, shopping motivations, and fashion reference group influence.

• Journal of the Korean earth science society
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• v.44 no.6
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• pp.629-642
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• 2023

Currently, low and intermediate level radioactive waste is being disposed of at the Gyeongju disposal site for permanent isolation. Since 2006, the Korea Radioactive Waste Agency has been conducting site characteristics surveys continuously verifying changes in the site based on the site monitoring and investigation plan. The hydrogeochemical environment of the disposal site is considered for the evaluation of natural barriers. However, the seawater must be considered because of the regional characteristics of Gyeongju, which is near the East Sea. Therefore, this study, collected 30 samples for deriving the groundwater quality data from seven wells and compared with two seawater samples collected from October 2017 to June 2022. Additionally, the study explores the groundwater monitoring method using statistical tools such as clustering and background concentration analysis. The groundwater samples in the study area were classified into two to four clusters depending on their chemical constituents-especially, EC, HCO₃, Na, and Cl-using statistical analysis, molar ratio, and K-means clustering.

• Korean Chemical Engineering Research
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• v.51 no.2
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• pp.263-266
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• 2013

It was investigated the electrochemical characteristics of the Ni-MH battery by hydrophilic process. For adopting the Ni-MH battery in water-electrolyte, polyolefin separator was processed the hydrophilic treatment. No treatment sample did not meet KS standard (KSC 8544) but hydrophilic treatment ones satisfied with the KS standard in electrochemical characteristics, such as discharge performance, retention capacity, and cycle performance. All hydrophilic treatment samples showed similar battery performances. Among them, sulfonation treatment sample exhibited the highest value in aspect of capacity retention rate (> 88%). Furthermore, fluoride treatment sample showed the best cycle performance during battery test. This sample maintained a good cycling performance until $1,480^{th}$ cycle, which was about 3 times as compared with that of KS standard (500 cycle).

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.8
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• pp.1621-1628
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• 2003

Packaging structures to block the propagation of higher­order modes in the shielded microstrip lines are designed. Packaging for microwave circuits is necessary, basically, to isolate and protect circuits from outside environments both physically and electrically. The drawback of packaging is the possibility of higher­order mode propagation, similar to waveguide modes, as the operating frequency increases. One of Possible choices for the higher­order mode suppression is to insert diaphragms to the housing structure. The shielding effects of diaphragms are analyzed using an FEM code. Several parameters such as dispersion, mode conversion, and higher­order mode transmission and reflection are analyzed. The effect of higher­order mode suppression is eminent as the depth or width of a diaphragm is increased in the air region of the microstrip line. It is shown that inductive diaphragm structure can lower ${S_21}$ for the second­order mode incidence by 30㏈, comparing with the conventional capacitive diaphragm structure. Packaging structure analyzed in this paper can be applied usefully to the design of the microwave system in a package such as transmit/receive modules.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.2
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• pp.245-251
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• 2017

The proposed variable pawer divider in this paper is composed of one equal power 2-way Wilkinson power divider, two variable phase shifters with 90-degree phase variation to be connected two output paths of the 2-way power divider, and one branchline coupler to combine output signals of two variable phase shifter. The proposed variable power divider can theoretically have an arbitrary power division ratio ranging from ${\infty}:1$ to ${\infty}:1$ due to 90-degrees phase variation of two phase shifter. The proposed power divider circuit fabricates on laminated TLX-9(h=20 mil, er=2.5; Taconic) with a center frequency of 1.7 GHz. The power division ratio of the fabricated prototype varies from about 1:100 to 200:1, with an input reflection characteristic(S11) of below -16 dB, an insertion loss of about -1.0 dB, and an isolation characteristic of below -17 dB between two output ports in the range 1.65-1.75 GHz.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.2
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• pp.253-259
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• 2016

This paper introduces a new variable power divider circuit with an arbitrary power division ratio ranging from $1:{\infty}$ to ${\infty}:1$. The proposed power divider circuit consists of one branch-line coupler to be a good input matching characteristic, two variable phase shifters with 90-degree phase variation to be connected two output paths of the branch-line coupler, and one ring-hybrid coupler to combine output signals of two variable phase shifter. The power division ratio between the two output ports of the proposed power divider can be easily controlled by the phase variation of the two phase shifter. The proposed power divider circuit fabricates on laminated RF-35 (h = 20 mil, er=3.5; Taconic) with a center frequency of 2 GHz. The power division ratio of the fabricated prototype varies from about 1:1000 to 5000000:1, with an input reflection characteristic(S11) of below -20 dB, an insertion loss of about -1.0 dB, and an isolation characteristic of below -17 dB between two output ports in the range 1.9-2.1 GHz.

• Journal of the Korea Organic Resources Recycling Association
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• v.30 no.4
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• pp.67-83
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• 2022

Biochar is a carbon material produced through the pyrolysis of agricultural biomass with limited oxygen condition. It has been suggested to enhance the carbon sequestration and mineralization of soil carbon. Objective of this study was to investigate soil potential carbon mineralization and carbon dioxide(CO₂) emissions in different soils cooperated with barely straw and livestock manure biochars in the closed chamber. The incubation was conducted during 49 days using a closed chamber. The treatments consisted of 2 different biochars that were originated from barley straw and livestock manure, and application amounts were 0, 5, 10 and 20 ton ha^-1 with different soils as upland, protected cultivation, converted and reclaimed. The results indicated that the TC increased significantly in all soils after biochar application. Mineralization of soil carbon was well fitted for Kinetic first-order exponential rate model equation (P<0.001). Potential mineralization rate ranged from 8.7 to 15.5% and 8.2 to 16.5% in the barely straw biochar and livestock manure biochar treatments, respectively. The highest CO₂ emission was 81.94 mg kg^-1 in the upland soil, and it was more emitted CO₂ for barely straw biochar application than its livestock biochar regardless of their application rates. Soil amendment of biochar is suitable for barely straw biochar regardless of application rates for mitigation of CO₂ emission in the cropland.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.2
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• pp.260-265
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• 2012

Soil respiration under flooded conditions is considered to be very small compared with aerobic soil respiration of soil organic matter. However, anaerobic decomposition of soil plays a key role in carbon cycling in flooded ecosystems. On the other hand, coal-ash wastes, such as fly ash and bottom ash, are known to function as a soil amendment for mitigating $CO_2$ emission and enhancing carbon sequestration in up land soils. In this study, we investigated bottom ash as a soil amendment for mitigating $CO_2$ emission, and thus enhancing carbon sequestration under anaerobic conditions. We observed that amendment of bottom ash without external organic source led to significant reduction in $CO_2$ emission rate and in total cumulative $CO_2$ emission flux over the incubation period, which was proportional to the amount of bottom ash applied. We also found that soil microbial biomass increased in response to application of bottom ash. These results suggest that bottom ash can be utilized to store $CO_2$ as a stable soil organic carbon in flooded ecosystems, as in aerobic situations.