• Journal of the Korean Applied Science and Technology
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• v.34 no.2
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• pp.280-288
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• 2017

Nanocarbon base materials such as, graphene and graphene hybrid with high electrochemical performances have great deal of attention to investigate flexible, stretchable display and wearable electronics in order to develop portable and high efficient energy storage devices. Battery, fuel cell and supercapacitor are able to achieve those properties for flexible, stretchable and wearable electronics, especially the supercapacitor is a promise energy storage device due to their remarkable properties including high power and energy density, environment friendly, fast charge-discharge and high stability. In this study, we have fabricated flexible supercapacitor composed of graphene/conductive polymer composite which could improve its electrochemical performance. As a result, specific capacitance value of the flexible supercapacitor (unbent) was $198.5F\;g^{-1}$ which decreased to $128.3F\;g^{-1}$ (65% retention) after $500^{th}$ bending cycle.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.3
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• pp.221-231
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• 1997

This paper presents an analysis of a hybrid direct-sequence/slow frequency hopped code division multiple access(DS/SFH-CDMA) system employing noncoherent M-ary frequency shift keying(MFSK) modulation in a multiple m-distribution fading environment. Multipath interfer- ence(MPI) and multiuser interference(MUI) is taken into accout and the spectral efficiency is calculated for uncoded as well as simple channel coding systems. The predetection multipath CCI canceller in conjunction with convolution coding is employed for improving the bit error rate(BER) performance. The BER of noncoherent hybrid system is obtained using a Gaussian interference approximation. From the results, we know that the error performance more deteriorates as the depth of fading becomes deeper. The DS part of the modulation combats the multipath interference, whereas the FH part is a predetection against large multiuser interference. It is shown that, for the con- sidered types of a channel coding, the use of a predetection coding is still essential for obtained a satisfactory bit error performance. The results show that the capacity of the DS/SFG-CDMA MFSK communication system increases in proportion to the length of PN code sequence in the presence of AWGN and MUI. In m-distribution fading environment the capacity increases in proportion to the fading index. The capacity is increased and error performance is improved when the CCI Canceller and Convolution code technique are adopted, respectively. From the results, it is known that the error performance of $4\times10^{-2}$ by adopting Canceller technique. Also convolutional coding technique is the improvement of error performance attains about $10^{-5}$ in code rate 1/2.

• Journal of Environmental Policy
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• v.8 no.1
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• pp.49-72
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• 2009

To analyze the direct and indirect $CO_2$ emission structure according to industries in Korea, a hybrid IO table quantifying the section of energy in the IO table is needed. However, the results of the recent researches revealed differences in the total amount of $CO_2$ emission by researchers in addition to significant standard deviation in industrial distribution. This study intends to make comparative analysis of the existing method of making an IO table for energy and environment and presents an improvement scheme to contribute to an improvement in calculation of the total amount of $CO_2$ emission and estimation of the emission by industries in Korea. For this purpose, division was made into use as raw materials of energy and that as fuel and a new hybrid IO table was made by removing confounding factors caused by the product tax and subsidies. As a result, the oil and coal industry emitted 5.2 times less $CO_2$ after removing energy inputted as raw materials from the transaction table than before. The amount of $CO_2$ emission estimated by using the IO table based on basic price was found to be 2.7% less than by using the IO table based on the producer price.

• Journal of the Korea Concrete Institute
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• v.19 no.2
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• pp.153-161
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• 2007

This paper investigates the lap splice performance of structural steel bars embedded in high performance fiber reinforced cementitious composite(HPFRCC) with various matrix ductilities. Matrix ductility is governed fiber type and fiber volume fraction. Fiber types were polypropylene(PP), polyethylene(PE) and hybrid fiber[polyethylene fiber+steel cord(PE+SC)]. The lap splice length$(l_d)$ was calculated according to the relevant ACI code requirements for reinforcing bars in normal concrete. As the result of tests, lap splice strength of HPFRCC using PE1.5 and hybrid fiber increased by up to $82{\sim}91$ percent more than that of concrete. Splice strength and energy absorption capacity of PE0.75+SC0.75 or PE1.5(fiber volume fraction 1.5%) specimen increased more than that of PP2.0(fiber volume fraction 2.0%) specimen. Therefore lap splice performance depends on fiber tensile strength and Young's modulus more than fiber volume fraction. Also, HPFRCC appear multiple crack and ductile postpeak behavior due to bridging of fiber in cementitious composite.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.3
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• pp.25-30
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• 2022

This study is a study on the filter bubble reinforcement phenomenon of SNS recommendation algorithm such as YouTube, which is a characteristic of the Russian-Ukraine war (2022), and the victory or defeat factors of the hybrid war. This war is identified as a hybrid war, and the use of New Media based on the SNS recommendation algorithm is emerging as a factor that determines the outcome of the war beyond political leverage. For this reason, the filter bubble phenomenon goes beyond the dictionary meaning of confirmation bias that limits information exposed to viewers. A YouTube video of Ukrainian President Zelensky encouraging protests in Kyiv garnered 7.02 million views, but Putin's speech only 800,000, which is a evidence that his speech was not exposed to the recommendation algorithm. The war of these SNS recommendation algorithms tends to develop into an algorithm war between the US (YouTube, Twitter, Facebook) and China (TikTok) big tech companies. Influenced by US companies, Ukraine is now able to receive international support, and in Russia, under the influence of Chinese companies, Putin's approval rating is over 80%, resulting in conflicting results. Since this algorithmic empowerment is based on the confirmation bias of public opinion by 'filter bubble', the justification that a new guideline setting for this distortion phenomenon should be presented shortly is drawing attention through this Russia-Ukraine war.

• Composites Research
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• v.19 no.1
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• pp.29-35
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• 2006

The avoidance of enemy's radar detection is very important issue in the modem electronic weapon system. Researchers have studied to minimize reflected signals of radar. In this research, two types of radar absorbing structure (RAS), 'C'-type shell and 'U'-type shell, were fabricated using fiber-reinforced composite materials and their radar cross section (RCS) were evaluated. The absorption layer was composed of glass fiber reinforced epoxy and nano size carbon-black, and the reflection layer was fabricated with carbon fiber reinforced epoxy. During their manufacturing process, undesired thermal deformation (so called spring-back) was observed. In order to reduce spring-back, the bending angle of mold was controlled by a series of experiments. The spring-back of parts fabricated by using compensated mold was predicted by finite element analysis (ANSYS). The RCS of RAS shells were measured by compact range and predicted by physical optics method. The measured RCS data was well matched with the predicted data.

• Industry Promotion Research
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• v.8 no.3
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• pp.175-180
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• 2023

On the day of 24 February 2022, Ukraine was invaded by Russia which signed to ensure definitely the Ukraine's national sovereignty, territorial integrity and security under the UN General Assembly Security Council A/49/765, named as the Budapest Agreement. This invasion is the 2nd invasion succeeded in Crimean Peninsula invasion of March 2014 after the Ukraine's national independence in 1991 from the USSR. However this invasion has been continuing for much more than one year. Although Ukraine President appealed the 'peace' toward Russia and claimed also to justify the Budapest Agreement of 1994 toward U.S.A., even any justifications were not appealed. The critical moment of the national abolition could be escaped from the unified desperate spirit of all nations including the president, political-social leaders and military members. Such patriotic and self-help spirits in Ukraine resulted in the active supports from the U.S.A., western and eastern free democratic countries, NATO and EU, and even the neutral countries. Furthermore these supports are increasing much more day-after-day. The lessons which the Ukraine War offers to the Korean national security should be cored with the development of self-reliant national defense capabilities, self-strenuous efforts and unity strengthening of the Korean-U.S. Alliance with the deep confidence.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.1
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• pp.21-27
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• 2016

Global warming due to greenhouse gas emissions is considered as a major problem worldwide, and many countries are making great efforts to reduce carbon dioxide emissions. Many technologies in post-combustion, pre-combustion and oxy-fuel combustion $CO_2$ capture have been developed. Among them, a hybrid pre-combustion $CO_2$ capture system of a water gas shift (WGS) reactor and a membrane gas separation unit was investigated. The 2 stage WGS reactor integrated high temperature shift (HTS) with a low temperature shift (LTS) was used to obtain a higher CO conversion rate. A Pd/Cu dense metal membrane was used to separate $H_2$ from $CO_2$ selectively. The performance of the hybrid system in terms of CO conversion and $H_2$ separation was evaluated using a 65% CO, 30 % $H_2$ and 5% $CO_2$ gas mixture for applications to pre-combustion $CO_2$ capture. The experiments were carried out over the range of WGS temperatures ($200-400^{\circ}C$), WGS pressures (0-20bar), Steam/Carbon (S/C) ratios (2.5-5) in a feed gas flow rate of 1 L/min. A very high CO conversion rate of 99.5% was achieved with the HTS-LTS 2 stage water gas shift reactor, and 83% $CO_2$ was concentrated in the retentate using the Pd/Cu membrane.

• Journal of KIISE
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• v.43 no.3
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• pp.362-369
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• 2016

This study is directed toward the design of a hybrid algorithm for syllable-based Korean POS tagging. Previous syllable-based works on Korean POS tagging have relied on a sequence labeling method and mostly used only a machine learning method. We present a new algorithm integrating a machine learning method and a pre-analyzed dictionary. We used a Sejong tagged corpus for training and evaluation. While the machine learning engine achieved eojeol precision of 0.964, the proposed hybrid engine achieved eojeol precision of 0.990. In a Quiz domain test, the machine learning engine and the proposed hybrid engine obtained 0.961 and 0.972, respectively. This result indicates our method to be effective for Korean POS tagging.

• Prospectives of Industrial Chemistry
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• v.24 no.5
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• pp.1-14
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• 2021

유무기 하이브리드 금속-할라이드계 페로브스카이트(organic-inorganic metal halide perovskite) 페로브스카이트 반도체 소재는 광전자 소자와 소재 연구에 새로운 연구 흐름을 만들고 있다. 태양전지 성능이 불과 과거 몇 년 사이의 짧은 연구 기간에도 불구하고, 광-전 변환 소자 중에서도 단일 소자와 적층 소자(tandem)에서 높은 광-전 변환 효율을 나타내기 때문이다. 이러한 급격한 연구 성과와 성장에도 불구하고, 페로브스카이트 소재의 다양한 광전자 특성의 평가와 결과에 대한 논의가 필요한 상황이다. 특히 내부 이온 이동이 광전자 원거리 이동 특성 평가와 해석에 영향을 주는 경우, 페로브스카이트 소재를 기반으로 한 다양한 광전자 소자의 성능 향상과 해석에 여전히 모호함을 준다. 달리 얘기하면, 이 소재의 기초 특성을 이해하고자 적용하는 다양한 기존 특성 평가 분석법의 활용과 해석에도 복잡한 영향을 미치고 있다고 할 수 있다. 이러한 페로브스카이트 소재 내에서 광전자 원거리 이동을 측정하는 새로운 방법을 소개하고자 한다. 첫 번째 방법으로, Quasi-steady 상태에서 광전도도를 전기적 특성으로 측정하고, 광조사 하에 투과 및 반사를 광학적으로 측정하여, 전도도와 광전자 밀도를 동시에 평가하는 방법으로, photo-induced transmission and reflection (PITR) 분광분석법이다. 이 분광분석법은 실제 소자의 구동조건을 구현한 상태에서 광전자의 원거리 이동에서 발생하는 광전자 밀도 변화를 반영한 광전자 이동도 특성 평가라는 장점을 가지고 있다. 두 번째 방법으로, 기존의 연속 전압 인가 방법 대신 펄스형 전압 인가 방식을 도입하는 방법으로, pulsed voltage space charge limited current (PV-SCLC) 분석법이다. 이는 펄스형 전압 인가 방법으로 이온의 이동을 최소화하여, 전류-전압 측정에서 히스테리시스가 없고 측정결과의 재현성과 신뢰도가 매우 높은 장점이 있다.