• 한국식품과학회지
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• 제32권1호
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• pp.50-55
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• 2000

수용성 methyl-hesperidin(MH)분말을 원료 MH로부터 제조하였으며, 천연색소의 안정화를 검토하였다. 원료 MH (8%)를 중류수와 혼합한 다음 $45^{\circ}C$에서 24시간동안 교반하여 용해시켰고, 분말 활성탄으로 탈색한 다음 0.45m 막여과를 통해 정제하였다. MH분말을 0.1 또는 0.2%농도로 riboflavin, bixin, 그리고 paprika oleoresin색소용액에 첨가하여 10에서 24시간 동안 자연광에 노출시킨 후 색소용액의 흡광도를 측정하였다. 수용성 MH를 첨가하지 않은 색소용액은 시간 경과에 따라 완전히 퇴색된 반면 MH를 첨가한 경우는 색소의 퇴색을 지연시켰다. 대체로 수용성 MH의 첨가량이 증가함에 따라 더욱 우수한 색소 안정화 효과를 나타내었다. 특히, paprika색소용액에서 수용성 MH와 함께 첨가한 비타민 C는 자연광에 노출시 8시간까지는 뚜렷한 상승효과를 나타내었다. 상기 결과를 통해 수용성 MH는 태양광의 자외선에 대해 우수한 색소 안정화제로서 작용함을 알 수 있었다.

• 한국통신학회논문지
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• 제39C권11호
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• pp.1042-1049
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• 2014

군의 MicroWave 통신 환경에서 회선 설계를 위해 링크거리, 가용도, 전송용량은 중요한 요소이다. 현재 고정용 변조방식으로 운용, 미래 전송용량 증대가 가능한 변조방식으로 진화될 예정이다. 링크 거리에 따라 페이딩 발생확률의 증가로 장거리의 경우 고신뢰의 전송품질을 지속적으로 보장하기 어려울 수 있다. 대용량 전송을 위한 변조방식의 경우 장거리가 될수록 링크버짓에서 페이드 마진의 저하로 가용도가 감소되어 QoS 보장에 있어 제한사항이 발생할 수 있다. 본 논문에서는 군 MicroWave 무선 링크에서의 링크거리를 고려한 대역폭 가변 할당 및 우선순위 전송 용량 비율 설정을 이용한 우선순위 전송 기법을 통해 무선 전송 성능 향상기법을 제안하고 링크 설계를 위한 채널 전송 용량 산출방안을 제시한다.

• 한국산학기술학회논문지
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• 제16권6호
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• pp.4192-4200
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• 2015

본 논문에서는 방호 방폭 구조물용 스프레이 콘크리트 재료 개발을 위해 기포를 혼입하여 강섬유의 분산성을 향상시킴으로서 강섬유 혼입 고인성 셀룰러 스프레이 콘크리트 재료를 개발하였다. 강섬유의 분산성 향상을 위해 과다하게 투입된 기포는 스프레이를 통해 대부분 소산하여 최종적으로 3 % ~ 6 % 미만의 적정 혼입율을 만족하게 되며, 이 상태에서 압축강도 및 휨인성 특성에 대해 고찰하였다. 압축강도 시험결과 28일 및 56일 강도에서 우수한 강도성능을 나타냈으며, 휨강도 및 휨인성 특성 또한 우수한 성능을 보여 과다하게 투입된 기포는 강섬유의 분산성을 향상 시키지만, 강도저하를 유발하지는 않는 것으로 판단된다. 그러나 화상분석을 통한 공극구조 분석 결과 소요의 간격계수와 비표면적을 얻는데 실패하였으며, 이것은 스프레이에 의한 공기량 소산 효과가 너무 커 간격계수가 다소 크게 측정된 것으로 판단된다.

• 한국통신학회논문지
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• 제27권8A호
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• pp.786-795
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• 2002

본 논문에서는 계층적 은닉 마코프 모델을 이용한 히스토그램과 모우멘트 기반의 동영상 장면전환 검출 방법을 제안한다. 제안된 방법은 웨이블릿 변환된 영상의 저주파 부 밴드로부터 히스토그램을 추출하며, 고주파 부 밴드로부터는 방향성 모우멘트를 추출한다. 그리고 수동적으로 분할된 비디오로부터 추출한 히스토그램 차와 모우멘트 차를 관측값으로 사용하여 은닉 마코프 모델을 학습한다. 비디오 분할 과정은 두 단계로 구성되는데, 먼저 히스토그램 기반의 은닉 마코프 모델은 입력된 비디오에 대하여 셧, 컷, 그리고 점진적인 장면전환의 3개의 범주로 분할한다. 그리고 두 번째 단계에서는 모우멘트 기반의 은닉 마코프 모델을 사용하여 점진적인 장면 전환을 더 세밀하게 페이드와 디졸브로 분할한다. 실험결과 제안된 방법은 기존의 경계값 기반의 방법보다 더 효율적으로 동영상의 셧 경계를 분할하였음을 볼 수 있었다.

• Tribology and Lubricants
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• 제17권4호
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• pp.267-275
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• 2001

Friction and wear properties of brake friction materials containing different metal fibers (Al, Cu or Steel fibers) were investigated. Based on a simple experimental formulation, friction materials with the same amount of metal fibers were tested using a pad-on-disk type friction tester. Two different materials (gray cast iron and aluminum metal matrix composite (MMC)) were used for disks rubbing against the friction materials. Results front ambient temperature tests revealed that the friction material containing Cu fibers sliding against gray cast iron disk showed a distinct negative $\mu$-v (friction coefficient vs. sliding velocity) relation implying possible stick-slip generation at low speeds. The negative $\mu$- v relation was not observed when the Cu-containing friction materials were rubbed against the Al-MMC counter surface. Elevated temperature tests showed that the friction level and the intensity of friction force oscillation were strongly affected by the thermal conductivity and melting temperature of metallic ingredients of the friction couple. Friction materials slid against cast iron disks exhibited higher friction coefficients than Al-MMC (metal matrix composite) disks during high temperature tests. On the other hand, high temperature test results suggested that copper fibers in the friction material improved fade resistance and that steel fibers were not compatible with Al-MMC disks showing severe material transfer and erratic friction behavior during sliding at elevated temperatures.

• Tribology and Lubricants
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• 제30권6호
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• pp.323-329
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• 2014

The friction-reducing properties of lubricants containing ionic liquids based on ammonium dithiocarbamate are studied. The ionic liquids are produced through the following two steps: the synthesis of sodium alkyl dithiocarbamates via the substitution reaction of dialkylamine and carbon disulfide and their subsequent conversion into ammonium dithiocarbamate-based ionic liquids through an ion-exchange reaction with a quaternary alkyl ammonium halide salt. The structures of the ionic liquids are characterized by NMR spectroscopy and Fourier transform infrared spectroscopy. The isolated yields of the ionic liquids, which are viscous and pale yellow, are approximately 92%. The Brookfield viscosities and pour points of the ionic liquids are determined. Further, their wear resistances are measured through the four-ball wear test and the Schwingung Reibung Ver-schleiss (oscillation, friction, wear) test. The wear scar diameter of the lubricants containing 1 wt of the quaternary alkyl ammonium dithiocarbamate-based ionic liquids (0.475-0.631 mm) is significantly lower than that of the base oil (0.825 mm), proving that the ammonium dithiocarbamate-based ionic liquids have good friction-reducing characteristics. However, these friction-reducing characteristics fade significantly after long-term storage, owing to the degradation of the ionic liquids.

• 한국정보통신학회논문지
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• 제12권2호
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• pp.223-230
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• 2008

본 논문에서는 지하철용 2.4GHz대 무선영상 전송 신호의 신호 성능을 파악하기 위하여 신호 변화 현상이 크게 발생하는 지하철역 플랫폼을 중심으로 신호 레벨을 측정하여 지하철 역 내부 구조에 따른 페이딩 특성을 분석한다. 측정 결과에 대한 분석 결과, 직선역 구간에서 다수의 강한 다중경로파가 생성되어 곡선역 구간에 비해 신호 레벨의 변화가 심하게 나타났다. 경로손실 지수는 직선역 구간인 신흥역에서 2.5, 곡선역 구간인 판암역과 대동역에서는 각각 1.6와 1.9으로 나타났다. 50% 지점의 페이드 깊이와 넓이는 직선역 구간인 신흥역에서 가장 심하였으며, 레벨 교차율은 짧은 페이드가 빈번하게 발생하는 판암역에서 가장 심하게 나타났다. 따라서 신호 성능에 영향을 주는 페이딩 현상은 곡선역에 비해 직선역에서 더욱 심하게 발생하는 것을 알 수 있다.

• 비교문화연구
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• 제27권
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• pp.415-434
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• 2012

The Hanja used in Korean are traditional Chinese characters, but what Chinese people use now is simplified characters. So, there are differences in pronunciation and meaning between the characters used by Korean and Chinese. More than 70% of the Korean language vocabulary derived from or were influenced by hanja. For the inheritance and development of traditional culture,and for the communication among countries of the Chinese characters cultural circle in Northeast Asia, should we build up an authentic Chinese education system. But the government hasn't pay much attention to this work, and the government's policy can't implement the efficient education. Consequently, in these days, there are more and more Korean people who are functionally illiterate in Chinese. Recently, proficiency tests of Chinese characters are expected to promote the development of Chinese education. But, most Koreans' motives for Chinese study are usually to pass the college entrance exam or to compete for jobs. However, after passing the test, the motive for studying gradually fade away. It is the basic problem faced by Korean Chinese character education. Since the 1950s, various character education methods have been studied in China, the research results were appliedin their textbooks and other materials. Therefore, a well-organized and efficient learning-by-step education system was built up. At present, China's literacy education in the textbooks utilizes a range of methods including revisional centralized and distributed. Unfortunately, there is still one shortcoming worthy of concerns: how to solve the problems due to the simplification of traditional Chinese characters? Is it possible to revive traditional Chinese characters? Before adopting the results of research on China's literacy education and applying them to our character education, we should consider our specific situation carefully. Adopting the research results with cautious review and objective criticism should have a positive impact on Korean Chinese character education.

• 한국환경교육학회지:환경교육
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• 제11권1호
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• pp.275-290
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• 1998

Nowadays, mankind is suffering from serious pollutions. In proportion to industrial modernization, polltional problems have been increased and arised new one endlessly. Todays, we are cope with a newkind pollution materials threatening the life of mankind with root out. It is Environmental Hormon, that is, Endocrine Disrupting Chemical(EDs). EDs was made by dioxin, PCB, DDT, cadmium, lead, ether and even diethylstillbestrol(DES) that used to contraceptive pill etc. These EDs makes changing from normal human hormon to abnormal one and it kill off or fade out spermatozoa. Then the spermatozoa was infected with EDs makes man imposex, sexual malformations and infertility also. It is the more critical phenomenons that EDs invade into the field of wild-life; birds, invertebrate animals, fishes, mammalia especially. England TV(BBC) journalist Cadury, D. introduced a lot of case studies that many kind of male animals was changed feminization by EDs in her book (The Feminization of Nature;1997). Otherwise, Gibbs, P.E. and Bryan, G. W. reported about dog-whelk snail (a sort of sea shell) was changed gender from male to female by EDs in their study. Briefly speaking, Environmental Hormon (EDs) stem from polluted materials maloperate human and animal informational codes of hormon. It is a significant event to an individual ontogeny and ecological system. To overcome these problem WHO, OECD, UNEP held many work-shops, international seminars and researches but it is not enough yet. On May of 1997, the International Meeting of Environmental Administrators makes a $\ulcorner$Declaration on EDs Problems$\lrcorner$ for solving it fortunately and NHK(japan) reported Super Critical Fluid as a new materials for decrease toxicity of dioxin in recent. Key Words : Environmental Hormon, EDs, imposex feminization, gender, DES, spermatozoa. Super Critical Fluid.

• 천문학회보
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• 제43권2호
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• pp.42.2-43
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• 2018

When galaxy clusters interact, the intergalactic gas collides, forming shocks that are characterized by a low sonic Mach number (~3) but a comparatively high Alfvenic Mach number (~30). Such shocks behave differently from the more common astrophysical shocks, which tend to have higher sonic Mach numbers. We wish to determine whether these shocks, despite their low sonic Mach number, are capable of accelerating particles and thereby contributing to the cosmic ray spectrum. Using the PIC-MHD method, which separates the gas into a thermal and a non-thermal component to increase computational efficiency, and relying on existing PIC simulations to determine the rate at which non-thermal particles are injected in the shock, we investigate the evolution of galaxy cluster shocks and their ability to accelerate particles. Depending on the chosen injection fraction of non-thermal particles into the shock, we find that even low-Mach shocks are capable of accelerating particles. However, the interaction between supra-thermal particles and the local magnetic field triggers instabilities and turbulence in the magnetic field. This causes the shock to weaken, which in turn reduces the effectiveness of the supra-thermal particle injection. We investigate how this influences the shock evolution by reducing the particle injection rate and energy and find that a reduction of the particle injection fraction at this stage causes an immediate reduction of both upstream and downstream instabilities. This inhibits particle acceleration. Over time, as the instabilities fade, the shock surface straightens, allowing the shock to recover. Eventually, we would expect this to increase the efficiency of the particle injection and acceleration to previous levels, starting the same series of events in an ongoing cycle of increasing and decreasing particle acceleration.