• 한국환경보건학회지
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• 제17권1호
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• pp.13-19
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• 1991

Interest in the studies of diesel exhaust emission has been increasing by the expected increase in the use of diesel powered automobiles out of concideration of fuel economy. It was well known that diesel exhaust emission was mutagenic in the bioassay as Ames test. The authors tried to find out the cytogenetic effect of diesel exhaust emission by the operational condition of engine such as speed and load. For the investigation of those effects, 66 male mice of ICR strain were used. The benzene-ethanol extracts of diesel exhaust emission were injected intra peritoneum 25rng/kg and 50mg/kg respectively. To evaluate the cytogenetic effect, mouse bone marrow micronucleus test was carried out. The frequency of micronucleus was different among the various groups according to the operational conditions of engine. The frequency of micronucleus in idling group was the highest of all the groups the subgroup of 50mg/kg showed the rate of 1.30%, 25rng/kg subgroup 0.55%. And the group of 2000rpm with 50% load showed the lowest rate of micronucleus appearance as 0.20% and 0.15%. In general, the frequency of micronucleus was shown higher in propotion to load and was shown inversely proportional to speed.

• Korea-Australia Rheology Journal
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• 제20권1호
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• pp.27-34
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• 2008

Clay suspensions in liquid polymers exhibit a time-dependent behaviour that includes viscoelastic as well as thixotropic features. Because of the presence of interacting clay platelets, particulate networks can develop, which are broken down during flow and rebuild upon cessation of the flow. Here, the use of thixotropic techniques in probing flow-induced structures in nanocomposites is explored with data on a hectorite-poly(isobutylene) model system. By means of fast stress jump measurements the hydrodynamic contributions to the steady state stresses are determined as well as those caused by the stretching of the clay floes. Flow reversal measurements do not provide a clear indication of flow-induced anisotropy in the present case. The recovery of the clay microstructure upon cessation of flow is followed by means of overshoot and dynamic measurements. The development of a particulate network is detected by the appearance and growth of a low frequency plateau of the storage moduli. The modulus-frequency curves after various rest times collapse onto universal master curves, regardless of the pre-shear history or temperature. The scaling factors for this master curve are the crossover parameters. The crossover moduli are nearly a linear function of the crossover frequency, the relation being identical for recovery after shearing at different shear rates. This function depends, however, on temperature.

• 한국의류학회지
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• 제23권3호
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• pp.361-372
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• 1999

The main objectives of this study were to investigate the characteristics of clothing buying behavior under the refund policy of stores (CCBBURPS) and the influence variables on CCBBURPS and to build the model of CCBBURPS. Additionally frequency and reasons for refund were researched. The interviews with 26 subjects the reviews of previous studies and the empirical investigation were processed for the study. The data was collected from 163 Korean females living in U.S. and analyzed by frequency mean factor analysis {{{{ chi ^2 }}-test, t-test and regression. The following results were found : the easyness of decision making (EDM) the loyalty of refund policy store (LRPS) and the increase of buying (IB) were found as the characteristics of clothing buying behaviors under the refund policy. EDM, LRPS and IB were influenced by clothing attitudes-shopping involvement and perceived buying risk-. The frequency of refund with 10 purchases was usually 0~1 times(38.7%) or 1~2 times (38.7%) The reasons for refund were : size unflattering appearance design com\ulcorner. The model of CCBBURPS was built based on the above findings(fig. 1)

• 한국의류학회지
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• 제47권1호
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• pp.35-51
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• 2023

This study used text mining to extract 2,842 keywords from 7,397 product names and organized them into categories in order to analyze the characteristics of keywords appearing in the product names of jeans after 2020. The item category included denim and Chungbaji [청바지], and Ilja [일자], while the silhouette category included wide and bootcut. In addition, high-waist and banding comprised the making sector, and the materials category consisted of napping, spandex, and soft blue. Denim surpassed the others in frequency, co-occurrence frequency, and centrality, and co-appeared with various other keywords. Also, the co-appearance of item and silhouette was prominent, and there were many keyword combinations that showed characteristics related to (a) high waist; (b) hemline detail; (c) rubber band; and (d) partial tearing. Furthermore, idiom expressions such as 'slim fit' and 'back tearing', which were not highlighted in the co-occurrence frequency, were additionally confirmed through correlation. Therefore, the product name analysis effectively identified the detailed characteristics of the silhouette and the making of jeans preferred by consumers.

• 수산해양기술연구
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• 제60권1호
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• pp.9-17
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• 2024

In this study, the seasonal distribution was surveyed using acoustic in the coastal waters around nuclear power plants. Acoustic surveys were conducted in June, September, December 2022, and March 2023 in the coastal waters of Uljin-gun. According to the results of this study, zooplankton were distributed at the depths from 0 m to 50 m in the waters around nuclear power plants. Zooplankton appeared in summer (June), autumn (September), and spring (March). In the survey area, fish were distributed at the depths from 25 m to 190 m, appearing in the summer (June), autumn (September), winter (December) and spring (March). The SV of zooplankton appearing in the survey area ranged from -98.0 dB to -78.0 dB, and it exhibited a one-class in the frequency distribution of SV. The SV of fish appearing in the survey area ranged from -36.0 dB to -35.0 dB and -98.0 dB to -53.0 dB, and it exhibited two-class in the frequency distribution of SV.

• 한국전자파학회논문지
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• 제30권3호
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• pp.215-222
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• 2019

주파수 도약신호는 전송시간 동안 반송파 주파수를 변경시켜 주파수 대역에서 확산 스펙트럼 특성을 가진다. 이러한 특성으로 주파수 도약신호는 무선채널환경에서 저피탐 및 항재밍 능력이 필요한 분야에 널리 활용된다. 본 논문에서는 미상의 주파수 도약신호에 대해 시작시간, 유지시간, 그리고 도약주파수를 포함하는 도약정보를 생성하는 기법을 제안한다. 제안한 블라인드 도약정보 생성 기법은 스펙트럼 데이터로부터 신호원에 대한 탐지정보를 생성하고, 이로부터 대상 주파수 도약신호의 출현, 유지, 그리고 종료 여부를 추정하는 동작 과정으로 도약정보를 추출한다. 또한, 시뮬레이션 결과를 통해 제안한 기법이 다양한 주파수 도약신호에 대하여 탐지 누락 없이 정확한 도약정보를 제공함을 확인하였다.

• 한국항공우주학회지
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• 제44권7호
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• pp.585-592
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• 2016

하이브리드 로켓의 연소실험에서 관찰된 500 Hz 대역의 연소압력과 연소반응 변동이 안정한 연소에서 발생하는 원인과 LFI로 발전하는 과정을 분석하기 위하여 $CH^*$ 화학발광 이미지와 PMT(photomultiplier tube)에 의한 광자방출 측정으로 연소반응 변화를 가시화하였다. 안정한 연소에서는 500 Hz 대역의 연소압력과 연소반응 변동의 위상차이가 180 도 정도를 이루며 전단층 유동을 따라서 정상적인 연소가 발생하였다. 그러나 불안정 연소가 발생하면, 500 Hz 주파수의 두 변동의 위상차는 60~70 도로 양의 관계(positive coupling)를 이루며 상하 대칭의 와류 발생과 국부적 소염이 나타나는 주기적 변화를 반복한다. 또한 천이구간에서는 매우 불규칙적인 와류와 상하 대칭의 전단층 유동 형상이 번갈아 관찰되고 있다. 이것은 연소의 영향으로 와류가 발생하는 것으로 보염기 후류에서 발생한 BVK 유동불안정과 유사한 특성을 보여준다, 따라서 하이브리드 로켓 연소의 저주파수 연소불안정은 500 Hz 대역의 연소반응 변동에 의한 와류의 발생과 이로 인한 국부적인 소염이 점진적으로 발전하여 완전한 주기적 소염으로 이어졌고, 20 Hz의 연소불안정으로 발전하는 것으로 판단하였다.

• 한국산학기술학회논문지
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• 제14권5호
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• pp.2244-2250
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• 2013

우리나라 청소년을 위한 구강보건교육 프로그램을 기획하는데 있어 기초자료를 제공하고자 2008년, 2009년, 2010년의 청소년건강행태온라인조사 원시자료를 이용하여 중학생 및 고등학생의 일일 잇솔질 평균 횟수를 분석하였다. 자료 분석은 조사에 참여한 표본이 우리나라 청소년의 대표성을 갖도록 지정된 가중치를 적용하였으며 자료는 SPSS 통계 프로그램을 이용하여 빈도분석, t-test 및 교차분석을 실시하였다. 우리나라 청소년의 잇솔질 평균 횟수는 2008년도에 3.92회, 2009년도에 3.96회 2010년도에 3.99회로 조금씩 증가하는 경향을 보였다. 우리나라 청소년이 학교에서 점심식사 후 잇솔질을 하는 대상자는 2008년 34.5%, 2009년 38.0%, 2010년 40.8%로 나타났으며 점심식사 후 잇솔질을 하지 않은 이유는 '칫솔, 치약 등을 가지고 다니기 귀찮아서'라는 응답이 가장 높게 나타났다. 따라서 우리나라 청소년의 체계적인 구강 건강 증진 프로그램을 기획하는데 있어 매 식후와 취침 전에 하도록 지도하여 잇솔질 횟수에 관한 지침을 마련해야 할 것이다.

• 한국음향학회지
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• 제10권1호
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• pp.12-19
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• 1991

기포 진동 시스템에 대한 수치해석이 수행되었다. 수학적 모델은 기포역학에 대해서는 Keller의 식을, 기포내부 해석을 위해서는 Prosperetti의 식을 채택하였다. Prosperetti는 기포내부 해석을 위해 에너지 방정식을 도입하였으며 매우 정확한 해석을 가능케 하였다. 수치해석결과 기포진동의 주파수 응답곡선에 있어 전형적인 비선형 현상들을 볼 수 있었다. 이러한 비선형 현상들에는 점프현상(jump phenomena), 공진주파수의 변화, 그리고 superharmonic 공진점의 발생등이 있다. 비선형 주파수 응답은 기포진동 시스템의 초기조건에 따라 달라지는데 이에 의해 어느 가진 주파수 대역에서는 두개 이상의 해가 존재할 수 있게 된다. 기포진동 시스템에서 비선형 진동현상은 Duffing 방정식과 비교가 되는데 두 시스템은 비슷한 비선형 현상들을 가지고 있다고 볼 수 있다.

• 한국치위생학회지
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• 제12권2호
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• pp.379-389
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• 2012

Objectives : The purpose of this study was to improve the practice level on dental hygienists'infection prevention by examining the actual condition of dental hygienists'infection control and analyzing factors of having influence upon this. Methods : A questionnaire survey was carried out from July 18, 2011 to August 26 targeting dental hygienists who work at medical institutions where are located in Daegu, Busan and Ulsan Metropolitan Cities and Gyeongsangnam buk-do. After then, the following conclusions were obtained. Results : 1. As a result of surveying practice by item in the practice level of infection prevention, the items with high practice level in the management of infectious diseases were surveyed to be 12 months(89.6%) for health-checkup cycle and to be having experience of vaccination(78.0%) for hepatitis type B. The items with high practice level in the management and practice of washing hands were indicated to be in order of regularly paper towel(87.7%) and hands cleaning after regular medical examination(80.5%). In the item of the practice on wearing and managing individual protection equipment, regularly wearing(93.1%) rubber globes given washing implements was indicated to be high. 2. As a result of analyzing working career, working institution, working region, and practice level of infectious-disease management, the appearance of fulfilling infection control guidelines at medical institution and the experience of education for infection control were indicated to have difference depending on working institution. Regularly health checkup was indicated to have difference depending on respondents' working career and working institution. 3. The whole average in the practice level of infection prevention according to working career, working institution, and working region was indicated to be 2.55 out of 3-point perfection. 4. Wearing latex gloves was indicated to have statistically significant difference depending on working institution(p<0.001) and working region(p<0.001). The exchange of latex gloves every patient and the use of paper apron had statistically significant difference depending on working region(p<0.001). 5. As a result of comparing the frequency of using protection equipment for preventing infection according to the management of infectious diseases, the statistically significant difference was shown depending on the appearance of infection control guidelines at medical institution(p<0.001), the appearance of having experience of health checkup(p<0.01), and the appearance of having experience of vaccination for hepatitis type B(p<0.05). Conclusions : The above-mentioned findings showed that the denture satisfaction of the denture-wearing senior citizens was linked to their subjective oral health awareness. Therefore it will be possible to improve denture-wearing elderly people's quality of life when oral health plans geared toward boosting their denture satisfaction are carried out.