• 대한치과보철학회지
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• 제44권3호
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• pp.333-342
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• 2006

Statement of problem. Although many studies have been carried out to investigate the correlation between the degree of conversion and the flexural strength of composite resins, there is minimal information in the literature attempting to compare degree of conversion, flexural strength and their correlation between restorative composite resins and flowable composite resins. Purpose. The purposes of this study were to measure the degree of conversion and flexural strength of composite resins with different rheological behavior and to correlate the two properties. Materials and methods. Four restorative (Vit-1-escence, Z-250, Tetric ceram, Esthet-X) and four flowable (Aeliteflo, Admiraflow, Permaflo, Revolution) light-curing composite resins were investigated. The degree of conversion(DC) was analyzed with Fourier transfer infra-red spectroscopy(FTIR) spectrum by a potassium bromide(KBr) pellet transmission method. The spectrum of the unpolymerized specimen had been measured before the specimen was irradiated for 60s with a visible light curing unit. The Poiymerized specimen was scanned for its in spectrum. The flexural strength(FS) was measured with 3-point bending test according to ISO 4049 after storage in water at $37^{\circ}C$ for 24 hours. The data were statistically analyzed by an independent sample t-test and one-way ANOVA at the significance level of 0.05. The dependence of flexural strength on the degree of conversion was also analyzed by regression analysis. Results. Mean DC and FS values ranged from 43% to 61% and from 84.7MPa to 156.7MPa respectively. DC values of the flowable composite resins were significantly higher than those of restorative composite resins (P < 0.05). The FS values of restorative composite resins were greater than those of flowable composite resins. No statistically significant correlation was observed between the DC and the FS tested in any of the composites. The dependence of FS on DC in restorative or flowable composite resins was not significant. Conclusion. It can be concluded that radical polymerization of the organic matrix is not a major factor in determining flexural strength of the commercially available composite resins.

• 한국전산구조공학회논문집
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• 제25권3호
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• pp.211-217
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• 2012

본 연구에서는 유리단섬유로 보강된 분사식 섬유보강 복합재료의 인장거동 평가를 위한 실험 및 해석연구를 수행하였다. 이를 위해 다양한 변형율속도(strain rate)에 따른 에폭시수지 및 분사식 섬유보강 복합재료의 인장강도 실험을 수행하였다. 본 연구에 사용된 분사식 섬유보강 복합재료는 15mm 길이로 절단된 유리단섬유가 25% 부피비율로 혼입된 보수 보강용 재료이다. 에폭시수지의 점탄성 특성을 고려하기 위해 역산모델링(inverse simulation)을 수행하여 변형율속도에 따른 점성변화를 함수식으로 제안하였다. 역산모델링을 통해 제안된 함수식을 미세역학 기반의 점탄성 손상모델(micromechanics-based viscoelastic damage model; Yang et al., 2012)에 적용하여 분사식 섬유보강 복합재료의 인장거동을 수치적으로 해석하였다. 분사식 섬유보강 복합재료의 인장거동 해석결과와 실험결과를 비교하여 미세역학 기반의 점탄성 손상모델의 정확성을 검증하였다.

• 한국정보통신학회논문지
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• 제25권1호
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• pp.56-62
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• 2021

미세먼지 예보에 대한 높은 정확도가 요구됨에 따라 기계 학습의 알고리즘을 적용하여 예측 정확도를 높이려는 다양한 시도들이 이루어지고 있다. 그러나 미세먼지의 특성과 불균형적인 농도별 발생 비율에 대한 문제로 예측 모델의 학습 및 예측이 잘 이루어지지 않는다. 이러한 문제를 해결하기 위해 특정 농도를 기준으로 미세먼지를 저농도와 고농도로 구분하여 예측을 수행하는 등 다양한 연구가 진행되고 있다. 본 논문에서는 미세먼지 농도의 불균형 특성으로 인한 예측 성능 향상의 문제를 해결하기 위한 미세먼지 농도의 이진 분류 모델을 제안하였다. 분류 알고리즘 중 logistic regression, decision tree, SVM 및 MLP를 이용하여 PM10에 대한 이진분류 모델들을 설계하였다. 오차 행렬을 통해 성능을 비교한 결과, 4가지 모델 중 MLP 모델이 89.98%의 정확도로 가장 높은 이진 분류 성능을 보였다.

• 무역학회지
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• 제47권6호
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• pp.247-267
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• 2022

Since the Korea-Vietnam FTA was signed in 2015, trade between the two countries has increased rapidly, accounting for 6.8% of Vietnam's exports and 17.9% of its imports in 2020. The two countries show differences in import and export items. Vietnam has a high export ratio of agri-food products or products with the low-middle level of technology, while Korea has a high export ratio of products with the upper-middle level. The purpose of this study is to present implications by analyzing changes in trade competitiveness between Vietnam and Korea by technology level (2002-2020). For this purpose, statistics from UN Comtrade were used, and methodologies such as market share, Export Market Share (EMS), Trade Specialization Index (TSI), Intra-Industrial Trade Index (IIT), Revealed Comparative Advantage (RCA), and BCG Matrix were used. The results of the study are as follows. First, when looking at Vietnam's trade structure with South Korea by technology level, it was analyzed that the trade deficit widened as it showed a competitive disadvantage in high-tech, ICT, middle- and low-level technology items, excluding low-end technology items. Second, in terms of market share, the market share of Vietnamese products in the Korean market is continuously increasing, while the Korean market share in Vietnam is gradually decreasing from 2017. Third, Vietnam's export competitiveness to Korea by technology level shows that low-level technologies are competitive, but they are inferior in competitiveness in all other technology level, and especially in areas with high technology level, the level of inferiority is high. In conclusion, the trade relationship between Vietnam and Korea has maintained a mutually complementary rather than competitive relationship, which is expected to continue in the future.

• Asian-Australasian Journal of Animal Sciences
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• 제21권7호
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• pp.1003-1010
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• 2008

The objective of the present study was to identify differences in the expression levels of liver proteins between healthy and ketotic cows, establish a liver metabolic interrelationship of ketosis and elucidate the metabolic characteristics of the liver during ketosis. Liver samples from 8 healthy multiparous Hostein cows and 8 ketotic cows were pooled by health status and the proteins were separated by two-dimensional-electrophoresis (2D-E). Statistical analysis of gels was performed using PDQuest software 8.0. The differences in the expression levels of liver proteins (p<0.05) between ketotic and healthy cows were identified by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF-TOF) tandem mass spectrometry. Five enzymes/proteins were identified as being differentially expressed in the livers of ketotic cows: expression of 3-hydroxyacyl-CoA dehydrogenase type-2 (HCDH), acetyl-coenzyme A acetyltransferase 2 (ACAT) and elongation factor Tu (EF-Tu) were down-regulated, whereas that of alpha-enolase and creatine kinase were up-regulated. On the basis of this evidence, it could be presumed that the decreased expression of HCDH, which is caused by high concentrations of acetyl-CoA in hepatic cells, in the livers of ketotic cows, implies reduced fatty acid ??oxidation. The resultant high concentrations of acetyl-CoA and acetoacetyl CoA would depress the level of ACAT and generate more ??hydroxybutyric acid; high concentrations of acetyl-CoA would also accelerate the Krebs Cycle and produce more ATP, which is stored as phosphocreatine, as a consequence of increased expression of creatine kinase. The low expression level of elongation factor Tu in the livers of ketotic cows indicates decreased levels of protein synthesis due to the limited availability of amino acids, because the most glucogenic amino acids sustain the glyconeogenesis pathway; thus increasing the level of alpha-enolase. Decreased protein synthesis also promotes the conversion of amino acids to oxaloacetate, which drives the Krebs Cycle under conditions of high levels of acetyl-CoA. It is concluded that the livers of ketotic cows possess high concentrations of acetyl-CoA, which through negative feedback inhibited fatty acid oxidation; show decreased fatty acid oxidation, ketogenesis and protein synthesis; and increased gluconeogenesis and energy production.

• Journal of Ginseng Research
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• 제44권1호
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• pp.105-114
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• 2020

Background: Exploring the pharmacokinetic (PK) changes of various active components of single herbs and their combinations is necessary to elucidate the compatibility mechanism. However, the lack of chemical standards and low concentrations of multiple active ingredients in the biological matrix restrict PK studies. Methods: A putative multiple reaction monitoring strategy based on liquid chromatography coupled with mass spectrometry (LC-MS) was developed to extend the PK scopes of quantification without resorting to the use of chemical standards. First, the compounds studied, including components with available reference standard (ARS) and components lacking reference standard (LRS), were preclassified to several groups according to their chemical structures. Herb decoctions were then subjected to ultrahigh-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry analysis with appropriate collision energy (CE) in MS² mode. Finally, multiple reaction monitoring transitions transformed from MS² of ultrahigh-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry were used for ultrahigh-performance liquid chromatography coupled with triple quadrupole mass spectrometry to obtain the mass responses of LRS components. LRS components quantification was further performed by developing an assistive group-dependent semiquantitative method. Results: The developed method was exemplified by the comparative PK process of single herbs Radix Ginseng (RG), Radix Polygala (RP), and their combinations (RG-RP). Significant changes in PK parameters were observed before and after combination. Conclusion: Results indicated that Traditional Chinese Medicine combinations can produce synergistic effects and diminish possible toxic effects, thereby reflecting the advantages of compatibility. The proposed strategy can solve the quantitative problem of LRS and extend the scopes of PK studies.

• 한국가족복지학
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• 제23호
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• pp.263-302
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• 2008

본 연구는 홀어머니와 성인인 큰아들의 갈등에 대한 가족치료사례로써, 가족관계에서 발생하는 의사소통의 어려움과 자아분화의 문제에 대한 가족치료적 개입방법과 효과성을 제시하고자 한다. 홀어머니와 큰아들의 갈등에 대하여 부인(며느리)이 상담을 의뢰하여 시작되었고, 13회기동안 개인 및 가족상담으로 진행되었다. 본 연구는 상담 축어록과 치료자가 기록한 메모를 중심으로 한 내용을 부호화(coding)작업을 통하여 개념과 하위범주, 그리고 상위범주로 나누었다. 또한 코딩작업을 통하여 발견한 범주들을 Miles와 Huberman(1994)이 제시한 관계망(network)와 매트릭스(matrix)를 활용하여 관계를 나타내었다. 본 연구의 분석 결과에 따르면 아버지가 사망하자 어머니는 큰아들이 가족을 부양해주기를 원하였지만, 큰아들은 어머니의 기대와 달리 결혼을 하여 분가하였다. 이 과정에서 서로의 감춰진 불만이 드러나고 모자갈등이 표면화되었다. 이런 갈등의 저변에는 가족의 경계선문제, 미분화된 자아, 역기능적 의사소통방식, 어머니의 원가족 경험 등이 영향을 미치고 있었다. 치료자는 모자갈등의 악순환고리를 끊기 위하여 치료적 동맹관계를 형성하였고, 의사소통방식의 지도, 반복되는 패턴의 조명, 재명명, 비유법을 활용하였다. 결과적으로 어머니와 큰아들은 자아분화, 기능적 의사소통의 활성화, 인식의 변화, 경계선의 변화를 경험하였고, 모자갈등의 소거와 더불어 가족관계가 향상되었다. 본 연구는 책임감과 기대감으로 인해서 발생하는 홀어머니와 큰아들의 갈등에 대한 가족치료가 효과적이라는 점과 유효한 개입방법들을 보여준다.

• Fisheries and Aquatic Sciences
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• 제22권12호
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• pp.31.1-31.12
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• 2019

Background: The black-chinned tilapia, Sarotherodon melanotheron, is the most abundant fish species in the Nakwa (an open lagoon) and Brenu (a closed lagoon) in the Central Region of Ghana. Aspects of the life history characteristics and the ecology of the fish populations in both lagoons were studied to assess the bio-ecological status of this important resource. Methods: Fish samples were obtained from fishermen that fish on the Nakwa and Brenu lagoons using cast, drag and gill nets. The age of the fish was assessed from otoliths analysis and its growth modelled following the von Bertalanffy growth function. Morphometric characteristics of the fish populations were analysed using power regression and ANOVA for parameters comparisons, and Student's t test to determine whether species grew isometrically. The percentage occurrence method was used to analyse the stomach contents of the fish. Results: A total of 382 fish samples from both lagoons were measured, comprising 209 from Nakwa lagoon and 176 from Brenu lagoon. The size and weight of fish samples ranged between 3.9-11.5 cm total length and 1.0-27.3 g for Nakwa Lagoon and 5.6-12.8 cm total length and 3.2-29.8 g for the Brenu Lagoon. The estimated von Bertalanffy growth parameters were L∞ = 12.04 cm and K = 2.76/year for the Nakwa Lagoon samples and L∞ = 13.44 cm and K = 3.27/year for Brenu Lagoon samples. Daily otolith incremental rate ranged from 0.01-0.03 mm per day to 0.01-0.02 mm per day for Nakwa and Brenu lagoons, respectively. Stomach content analysis of the fish samples revealed that the species are planktivorous and the range of food varied between the lagoons. Green algae were the most prevalent food item in the stomachs of the fish samples from Nakwa with the frequency of 69% whilst diatoms (80.5%) were most prevalent phytoplanktonic food item for the fish in Brenu lagoon. Conclusions: The estimates of asymptotic length for the species in both lagoons are close to known values of the species length at first sexual maturity and points to intensive fishing pressure. As a consequence, a comprehensive sample-based survey is required in both lagoons to derive estimates of management reference points. The results of the stomach content analysis are beneficial to the construction of diet matrix for ecosystem models of the two systems.

• Journal of Forest and Environmental Science
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• 제15권1호
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• pp.1-9
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• 1999

천연활엽수림에서 자생하는 활엽수종 고유의 생장 특성을 감안하여, 18개 주요 상층 임관 구성 수종을 대상으로 임목 형질을 평가하는 한 방편으로서 임목(林木) 형질(形質) 지수(指數)(tree form index: TFI)를 추정하였다. 선정된 6개의 형질 속성을 4개의 급수로 나누고, 임목 개체의 전반적인 형질에 미치는 영향력을 고려하여 합당한 점수를 부여하였다. 18개 수종에 대하여 속성 별로 점수를 부여하고 백분률(百分率)로 환산한 후, 각 점수를 합하여 임목 형질 지수를 산출하였다. 각 쌍의 수종별 점수 차이와 $18{\times}6$ 행렬(行列)을 바탕으로 집락분석(集落分析)(cluster analysis) 을 시도하여 수종별로 어떠한 속성들이 공통적인가를 검토하였다. 연구 결과, 임목 형질이 가장 좋은 수종은 TFI 수치 80.8을 기록한 사시나무로 파악되었고, TFI 수치 46.3을 기록한 까치박달나무는 임목 형질이 가장 좋지 않은 수종으로 분석되었다. 70점 이상의 비교적 높은 지수를 획득한 상층 임관 수종들은 사시나무, 거제수나무, 들메나무, 느릅나무 등으로서, 통직하고 완만한 수간, 높은 지하고(枝下高), 좁은 수관(樹冠), 가는 가지 등의 특성을 갖는 장점을 지니고 있었다. 반면에, 60점 미만의 낮은 지수를 얻은 수종들은 팔배나무, 산벚나무, 복장나무, 가래나무, 까치박달나무 등으로서, 굽었거나 기울어진 수간, 낮은 지하고(枝下高), 넓은 수관, 굵은 가지 등의 성격을 갖는 경향이 있었다. 집락분석 결과에 의한 분류도(分類圖)에서 Euclidean 거리계수(距離係數) 임의의 값 10은 연구 대상 수종들을 4개의 뚜렷한 수종군(樹種群)으로 분류하였고, 각 수종군에 대한 임목 형질 특성을 검토하였다.

• Asian-Australasian Journal of Animal Sciences
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• 제29권9호
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• pp.1239-1246
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• 2016

The breeding of yaks is highly seasonal, there are many crucial proteins involved in the reproduction control program, especially in follicular development. In order to isolate differential proteins between mature and immature follicular fluid (FF) of yak, the FF from yak follicles with different sizes were sampled respectively, and two-dimensional gel electrophoresis (2-DE) of the proteins was carried out. After silver staining, the Image Master 2D platinum software was used for protein analysis and matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS) was performed for differential protein identification. The expression level of transferrin and enolase superfamily member 1 (ENOSF1) was determined by Western blotting for verification analysis. The results showed that 2-DE obtained an electrophoresis map of proteins from mature and immature yak FF with high resolution and repeatability. A comparison of protein profiles identified 12 differently expressed proteins, out of which 10 of them were upregulated while 2 were downregulated. Western blotting showed that the expression of transferrin and ENOSF1 was enhanced with follicular development. Both the obtained protein profiles and the differently expressed proteins identified in this study provided experimental data related to follicular development during yak breeding seasons. This study also laid the foundation for understanding the microenvironment during oocyte development.