• Proceedings of the KSME Conference
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• 2004.11a
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• pp.453-458
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• 2004

This study proposes a new two-level condensation scheme for the construction of a reduced system. In the first step, the candidate area is selected for the construction of the reduced system by energy estimation in element-level. In the second step, primary degrees of freedom are selected by sequential elimination from the candidate degrees of freedom linked to the selected elements. Numerical examples demonstrate that the proposed method saves the computational cost effectively and provides a reduced system which predicts the eigenvalues accurately. Moreover, the well-constructed reduced system can present the reliable behavior of the structure under arbitrary dynamic loads comparing to that of global system. Time integration in a reduced system can save the computing time remarkably. Through a few numerical examples, the efficiency and reliability of the proposed scheme are verified.

• Communications of Mathematical Education
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• v.18 no.2 s.19
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• pp.93-108
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• 2004

Wassily Leontief가 미국 경제의 모델에 선형 대수를 적용한 이론으로 1973년에 노벨 경제학상을 받은 후로는 인문${\cdot}$사회 과학(특히 상경(商經) 분야)을 전공하는 사람에게도 선형 대수는 큰 관심 분야가 되었다. 그래서 1980년대 부터는 대학의 기초 과목으로써 선형 대수를 가르치는 것은 유행처럼 퍼졌고 또 가르침에 관한 연구도 활발하여졌다. 현행 우리나라의 초${\cdot}$중${\cdot}$고등 학교의 수학과 교육과정(이른바 “제 7차 개정”) 속에는 선형대수의 내용이 어느 정도 있으나 학생들에게 확실한 개념을 갖도록 가르치고 있지 않다. 수직선, 순서 쌍, n-겹수, 직교 좌표, 벡터 등 해석기하적인 내용과 선형 방정식계의 풀이법(가우스${\cdot}$조르단 소거법을 쓰지 않는 풀이법) 등 일반 대수적인 내용은 다루지만 선형 변환, 벡터 공간의 구조 등은 다루지 않는다. m${\sim}$n 행렬은 수학II에 나와 있긴 하나 소개하는 정도에 그친다. 한편 과학 계열 고등학교 학생을 위한 "고급 수학"에는 비교적 많은 양의 선형 대수의 내용이 있다. 일반 계열 고등학교의 수학에서도 선형 대수의 내용을 확장하고 학생들에게 확실한 개념을 갖도록 가르쳐서 이들이 대학에 진학하여 전공 분야에서 아무 어려움이 없도록 하는 것이 바람직하다.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.7
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• pp.196-202
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• 2000

In the precision point synthesis of mechanisms, it is usually required to solve a system of polynomial equations. With the aid of efficient algorithms such as elimination, it is possible to obtain all the solutions of the equations in the complex domain. But among these solutions only real values can be used fur real mechanisms, while imaginary ones are liable to be discarded. In this article, a method is presented, which leads the imaginary solutions to real domain permitting slight alteration of prescribed positions and eventually increases the number of feasible mechanisms satisfying the desired motion approximately. Two synthesis problems of planar 4-bar path generation and spatial 7-bar motion generation are given to verify the proposed method.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2011.10a
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• pp.19-19
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• 2011

예비실험 중 한국의 울릉도에 자생하고 취나물로 이용되고 있는 섬쑥부쟁이(Aster glehni Franchet et Sckmidt, Compositae)가 페놀성 화합물 함량이 높고 peroxynitrite 소거효과가 높았기 때문에 이를 이용한 추출물의 제조를 통한 건강기능식품을 창출하고자 하였다. 건강식품을 위한 추출물 제조를 위하여 물과 에탄올만을 이용하여 페놀성 화합물 고함유 추출물의 제조가 가능하고 높은 peroxynitrite 소거효과를 나타내는 추출물을 결정하고자 하였다. 즉, 추출용매로 Water-EtOH 비율을 조절하여 추출하여 추출물의 함량, HPLC를 이용한 caffeoylquinic acid(CQ) 화합물의 함량분석 및 peroxynitrite 소거효과를 비교하였다. Water-EtOH (7:3)으로 추출한 섬쑥부쟁이 추출물은 CQ 함량이 높고, 높은 peroxynitrite 소거효과, 항경련효과, 진정효과 및 항비만효과 등이 나타났다. 건강기능식품을 위한 추출물 제조시 한국에서는 물과 에탄올만이 허용되기 때문에 CQ 함량이 높은 추출물의 제조가 가능하고 높은 peroxynitrite 소거효과를 유지할 수 있는가에 관한 실험 이외에 마우스에서 선택된 추출물의 진정효과 및 항경련효과 실험을 수행하였다. 진정효과와 항경련효과를 위하여 마우스에서 각각 pentobarbital로 유도한 수면연장효과와 PTZ로 유도한 경련에 대한 효과를 측정하여 유의성있는 활성이 확인되었으므로 이 추출물을 이용한 건강기능식품으로의 이용이 가능하다고 생각된다.

• Korean Journal of Medicinal Crop Science
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• v.6 no.3
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• pp.181-187
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• 1998

This study was carried out to investigate the antioxidative activities of medicinal plants. Through the examination of methanol extracts from 30 species for radical scavenging effects using DPPH method, the extracts from Rhus javanica Linne, Smilax china Linne and Polygonum cuspidatum Siebold et Zucarinii showed strong antioxidative activity. Because of its highest antioxidative activity among 30 medicinal plants, radical scavenging effects of 4 different extract compartments (n- Hexane, EtOAc, BuOH and $H_2O$ extracts) from Galla Rhois MeOH extract of Rhus javanica Linne were examined by DPPH method and antioxidant effects on the 4 different extract compartments were tested by Ferric-Thiocyanate method. Antioxidative activities of n- Hexane, EtOAc and BuOH extracts were similar or even higher than that of natural (tocopherol) or synthetic antioxidants (BHA), suggesting that major fractions for the antioxidative activity of Rhus javanica Linne were the n- Hexane, EtOAc and BuOH extract compartments.

• Journal of Korean Ophthalmic Optics Society
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• v.6 no.2
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• pp.121-127
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• 2001

While SVD and Gaussian elimination method were applied to the additive damped least squares(DLS), the convergence and the stability of the optimization process were examined in a triplet-type camera lens-system where the condition number is well conditioned. DLS with SVD method generated a suitable merit function but this merit function may be trapped in a local minimum by the nonlinearity of error function. Therefore, the least camera lens-system was further designed by the global optimization method is grid method, and this method is adopted to get merit function that convergent to global minimum without local minimum trapping.

• Journal of Acupuncture Research
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• v.27 no.4
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• pp.1-8
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• 2010

목적 : 본 연구는 녹용약침액의 주름 개선 효과에 대하여 여러 가지 in vitro 실험을 통해 확인해 보고자 계획되었다. 방법 : 녹용약침액의 항산화효과를 DPPH(1,1-diphenyl-2-picrylhydrazyl) 자유라디칼 소거법을 이용하여 측정하였고, 또, elastase 억제 효과를 측정하였다. 그리고 녹용약침액이 사람 정상 섬유아세포 HS 68에서 UVB 조사 후 type I procollagen의 생산량 회복에 미치는 효과를 ELISA법을 이용하여 측정하였다. 결과 : 녹용약침액에서 우수한 DPPH 자유라디칼 소거 효과가 관찰되었다. 또한 통계적으로 유의한 elastase 활성 억제 효과를 관찰할 수 있었다. 사람 섬유아세포 HS 68을 이용한 실험에서는 녹용약침액 처치군에서 UVB 조사로 감소된 type I procollagen이 유의하게 회복되는 것이 관찰되었다. 결론 : 본 연구 결과에 의하면, 녹용약침액에는 유효한 주름개선 효과가 있어, 미용약침 소재로 개발할 수 있을 것으로 사료된다.

• Journal for History of Mathematics
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• v.26 no.2_3
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• pp.149-161
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• 2013

The history of finding solutions of linear equations went back to some thousand years ago, and has been steadily developed to solve systems of higher degree polynomials. The method to eliminate variables came into use around the 17th and 18th century. This technique has been extended to the resultant theory that was laid in the 19th century by outstanding mathematicians as Euler, Sylvester, and B$\acute{e}$zout. In this paper we discuss the historical reflection about the development of solving system of polynomials. We add a special emphasis on E. B$\acute{e}$zout who gave the first account on the resultant which is a generalization of discriminant and Gauss elimination method.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.4
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• pp.165-174
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• 2011

This research aims at the optimal constitution of sensors required to identify the structural shortcoming of roller-coaster. In this research we analyzed the dynamic characteristics of roller-coaster by three dimensional FE modelling, decided on the appropriate location and number of sensors through optimal transducer theory, abstracted the mathematical value of modal features before and after damage on the basis of optimally placed and numbered sensors. and then presented it as a primary information about the basic structure which would be applied to damage estimation. As a target structure, the roller-coater at Seoul Children's Grand Park was chosen and built as a model reduced by one twentieth in size. In order to consider the Kinetics features particular to the roller-coaster structure, we made an exact three-dimensional FE modelling for the model structure by means of Spline function. As for the proper location and number of sensors, it was done by applying EIM and EOT. We also estimated the damage from the combination of strength, flexibility, and model corelation after abstracting the value of modal features. Finally the optimal transducer theory presented here in this research was proved to be valid, and the structural damage was well identified through changes in strength and flexibility. As a result, we were able to present the optimal constitution of sensors needed for the analysis of dynamic characteristics and the development of techniques in dynamic characteristics, which would ultimately contribute to the development of health monitoring for roller-coaster.

• Journal of Life Science
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• v.23 no.7
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• pp.913-918
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• 2013

The applicability of the ultrasonic wave method to the extraction of useful components from seaweeds was investigated. Extracts from freeze-dried Ecklonia cava powder were prepared with hot water ($65^{\circ}C$), water ($24^{\circ}C$), 50% ethanol, and 100% ethanol, and ultrasonic extraction was also performed. The content of phenolic compounds and the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity and tyrosinase inhibitory activity of the extracts were analyzed, and differences in the data obtained by the ultrasonic extraction and the traditional extraction methods were compared. The phenolic content in the E. cava extract by ultrasonic extraction (142.80 mg/g) was approximately 14 times higher than the phenolic content in the hot water extract (10.03 mg/g). The DPPH radical scavenging and the tyrosinase inhibitory activities of the ultrasonic extract were approximately 4 times and 14 times higher than the hot water extracts, respectively. The correlation between the phenolic content and the DPPH radical scavenging activity ($R^2$=99.47) and between the phenolic content and the tyrosinase inhibitory activity ($R^2$=99.99) was very high. These results indicate that ultrasonic extraction is more suitable than traditional extraction for the extraction of useful components from E. cava.