• Journal of the Society of Naval Architects of Korea
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• v.43 no.4 s.148
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• pp.431-439
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• 2006

Due to the limitation of size of the test section, blockage effects could not be avoided in the model test of yacht sails for common wind tunnels. In this paper, a numerical analysis is performed to investigate the blockage effects on the lift and drag forces measured from wind tunnel experiments for a 30 feet sloop yacht sail. Complex airflows around the jib and main sails including three-dimensional flow separations are calculated for various close-hauled conditions. It is found that the blockage of a wind tunnel changes the flow separation and consequently the lift and drag forces of the sails, especially the main sail, reduce and increase, respectively, due to the blockage effects.

• Journal for History of Mathematics
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• v.20 no.4
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• pp.1-21
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• 2007

We investigate the Gou Gu Shu(句股術) in Hong Jung Ha's Gu Il Jib(九一集) and Cho Tae Gu's Ju Su Gwan Gyun(籌書管見) published in the early 18th century. Using a structural approach and Tien Yuan Shu(天元術), Hong has obtained the most advanced results on the subject in Asia. Using Cho's result influenced by the western mathematics introduced in the middle of the 17th century, we study a process of a theoretical approach in Chosun mathematics in the period.

• Korean Journal of Oriental Medicine
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• v.14 no.2
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• pp.1-10
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• 2008

Noh Jungrye(盧重禮) can be cited as an representative royal doctor of early Chosun dynasty. He collaborated in the development of korean medicine out of the influence of chinese medicine. He made an systematical approach on supply and propagation of The Native Herb Medicine(鄕藥) which promoted the independence of Korean medicine. The edition of "HyangYakJibSungBang(鄕藥集成方)"(Compendium of Prescriptions from the Countryside) was the result of this effort establishing the originality of Korean medicine. He also strengthened in the medical support new born child editing "TaeSanYoRok(胎産要錄)" as their mortal rate was high in that time. In social-political aspect, being appointed in Dangsanggwan(堂上官) as a doctor, was controversial as even after his death this discussion kept on. On the other hand this designation prompt other doctors to devote in Korean medicine.

• Journal for History of Mathematics
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• v.25 no.2
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• pp.1-9
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• 2012

After disastrous foreign invasions in 1592 and 1636, Chosun lost most of the traditional mathematical works and needed to revive its mathematics. The new calendar system, ShiXianLi(時憲曆, 1645), was brought into Chosun in the same year. In order to understand the system, Chosun imported books related to western mathematics. For the traditional mathematics, Kim Si Jin(金始振, 1618-1667) republished SuanXue QiMeng(算學啓蒙, 1299) in 1660. We discuss the works by two great mathematicians of early 18th century, Cho Tae Gu(趙泰耉, 1660-1723) and Hong Jung Ha(洪正夏, 1684-?) and then conclude that Cho's JuSeoGwanGyun(籌 書管見) and Hong's GuIlJib(九一集) became a real breakthrough for the second half of the history of Chosun mathematics.

• Journal for History of Mathematics
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• v.27 no.3
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• pp.155-164
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• 2014

Tianyuanshu and Zengcheng Kaifangfa introduced in the Song-Yuan dynasties and their contribution to the theory of equations are one of the most important achievements in the history of Chinese mathematics. Furthermore, they became the most fundamental subject in the history of East Asian mathematics as well. The operations, or the mathematical structure of polynomials have been overlooked by traditional mathematics books. Investigation of GuIlJib (九一集) of Joseon mathematician Hong JeongHa reveals that Hong's approach to polynomials is highly structural. For the expansion of $\prod_{k=11}^{n}(x+a_k)$, Hong invented a new method which we name Hong JeongHa's synthetic expansion. Using this, he reveals that the processes in Zhengcheng Kaifangfa is not synthetic division but synthetic expansion.

• Journal for History of Mathematics
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• v.22 no.2
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• pp.1-12
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• 2009

Zhu Shi Jie's Suan Xue Qi Meng is one of the most important books which gave a great influence to the development of Chosun Mathematics. Investigating San Hak Gye Mong Ju Hae(算學啓蒙註解) published in the middle of the 19th century, we study the development of Chosun Mathematics in the century. The author studied western mathematics together with theory of equations in Gu Il Jib (九一集) written by Hong Jung Ha(洪正夏) and then wrote the commentary, which built up a foundation on the development of Algebra of Chosun in the century.

• Proceedings of the Korean Society of Crop Science Conference
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• 2000.04a
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• pp.344-345
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• 2000

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2014.06a
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• pp.232-233
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• 2014

TV홈쇼핑은 CATV, 위성TV, IPTV, DMB, 스마트폰 모바일로 생방송이 송출되고 있다. 여러 송출 매체 중 스마트폰 모바일 송출부분에서 방송 중 쇼호스트가 제품에 대해 설명하는 부분인 디테일부분에서 카메라의 워킹(Standard, Jimmy jib, Hand held, Dolly)에 따라 화질이 깨지는 현상(블록 현상)이 발생하고 소비자가 제품을 제대로 인식하지 못하는 불편이 있다. 본 논문에서는 카메라의 워킹에 따라 제품의 설명 중 화질의 변화하는 현상을 파악해 보고자 한다.

• Journal of the Korean Statistical Society
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• v.31 no.2
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• pp.261-276
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• 2002

Probability density or its derivatives may have a discontinuity/change point at an unknown location. We propose a method of estimating the location and the jump size of the discontinuity point based on kernel type density or density derivatives estimators with one-sided equivalent kernels. The rates of convergence of the proposed estimators are derived, and the finite-sample performances of the methods are illustrated by simulated examples.

• Communications for Statistical Applications and Methods
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• v.8 no.2
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• pp.327-336
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• 2001

This work concerns estimating a regression function, which is not linear, using aggregate data. In much of the empirical research, data are aggregated for various reasons before statistical analysis. In a traditional parametric approach, a linear estimation of the non-linear function with aggregate data can result in unstable estimators of the parameters. More serious consequence is the bias in the estimation of the non-linear function. The approach we employ is the kernel regression smoothing. We describe the conditions when the aggregate data can be used to estimate the regression function efficiently. Numerical examples will illustrate our findings.