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Curvature homogeneity for four-dimensional manifolds
Sekigawa, Kouei,Suga, Hiroshi,Vanhecke, Lieven Korean Mathematical Society 1995 대한수학회지 Vol.32 No.1
Let (M,g) be an n-dimensional, connected Riemannian manifold with Levi Civita connection $\nabla$ and Riemannian curvature tensor R defined by $$ R_XY = [\nabla_X, \nabla_Y] - \nabla_{[X,Y]} $$ for all smooth vector fields X, Y. $\nablaR, \cdots, \nabla^kR, \cdots$ denote the successive covariant derivatives and we assume $\nabla^0R = R$.
Pharmacoat Coating in an Aqueous System : The Dissolution Behavior and Reduction in Coating Time
Sekigawa Fujio,Muto Hiroaki,Araume Kiyoshi The Korean Society of Pharmaceutical Sciences and 1990 Journal of Pharmaceutical Investigation Vol.20 No.3
It is sometimes said lately that the pH of the human gastric juice is significantly different among individuals. Thus, the dissolution behavior of coated solid dosage forms should preferably be independent of the pH of the test solution. With these points as a background, the effect of pH on the dissolution velocity of coated tablets was studied to compare that of Pharmacoat with other gastric soluble film coating materials. Three viscosity types of Pharmacoat have been available(3, 6 and 15cP) until now. the 6cP type has been considered to be the most suitable for a tablet coating amongst the three types. The 3 cP type with a low degree of polymerization, is capable of providing high concentration, but the film strength is so inferior that sometimes cracking of the film may occur. On the other hand, in the case of the 15cP type, high polymer concentration cannot be achieved because of the high dgree of polymerization, and thus it is uneconomical for coating. Now, there is a strong demand to reduce the coating time even when HPMC is used in the 6cP type in order to reduce the coating cost. In order to improve this problem, we have concentrated our attention on reducing the viscosity value of HPMC to an allowable lower limit from 6cP. As a result of this study, it was found that the reduction of the viscosity value to around 4.5cP enabled the use of a higher solution concentration and an incidental shorter coating time without giving any substantial adverse effects on the properties of coated preparations. These experiment results are presented in the later part of this presentation. Based on this study, we have added the viscosity type of 4.5cP as one of the Pharmacoat products as Pharmacoat-645.
Enhancement of the luminescence efficiency of Li2TiO3:Mn4+ red emitting phosphor for white LEDs
K. Sekigawa 한양대학교 세라믹연구소 2013 Journal of Ceramic Processing Research Vol.14 No.S1
A red-emitting Li2TiO3:Mn4+ phosphor has excellent luminescence property. To enhance the optical absorption in the blue light region and to apply the phosphor to tri-color LEDs, we tried that a part of the Li+ and Ti4+ sites in the Li2TiO3:Mn4+ phosphor was substituted with alkaline metal ions (A = Na, K and Rb) and Ge4+ ions, respectively. The resulting phosphor exhibited efficient red emission and the luminescence intensity was about 3 times higher than that of Li2(Ti0.99Mn0.01)O3. The relative emission intensity of the phosphor was approximately 70%, compared with that of YAG:Ce3+ (P46) when the phosphors were excited at 460 nm. These results indicate that the red-emitting (Li0.97Rb0.03)2(Ti0.70Ge0.30)O3:Mn4+ phosphor is a promising candidate for white LEDs
(Fujio Sekigawa) 한국약제학회 1993 PROCEEDINGS OF THE FIP POST-SATELLITE SYMPOSIUM `9 Vol.- No.-
These days, it is not uncommon that a same kind of drug is circulated globally. However, the qualities of excipients used in the same drug have to be sometimes different depending on the different requirements in the qualities stipulated by each country. For a supplier of pharmaceutical excipients, it is generally necessary to carry out different tests on the same kind of testing criteria depending on the country of destination. Thus, the discrepancies between compendium requirements of pharmaceutical excipients create severe problems in various area of industrial activities. The decision of the United States Pharmacopoeia, European Pharmacopoeia and Japanese Pharmacopoeia Commissions to harmonize the requirements is a unique chance for the industries to overcome these problems. On the other hand, discrepancies of general test methods and requirements in each monograph of pharmaceutical excipient between the compendia valid at present are in most cases extensive. Consequently their harmonization needs a lot of detailed work requiring strong support from the industry. Based on these circumstances, pharmaceutical excipients councils have been established first in U.S.A. and successively in Europe and in Japan to contribute to the harmorization process. We should like to review here the progress since the Orlando Conference in 1991 and comment about the matters at issue with regard to the international harmonization of pharmaceutical excipients.
Pharmacoat Coating in an Aqueous System : The Dissolution Behavior and Reduction in Coating Time
Fujio Sekigawa,Hiroaki Muto,Kiyoshi Araume 한국약제학회 1990 Journal of Pharmaceutical Investigation Vol.20 No.3
It is sometimes said lately that the pH of the human gastric juice is significantly different among individuals. Thus, the dissolution behavior of coated solid dosage forms should preferably be independent of the pH of the test solution. With these points as a background, the effect of pH on the dissolution velocity of coated tablets was studied to compare that of Pharmacoat with other gastric soluble film coating materials. Three viscosity types of Pharmacoat have been available(3, 6 and 15cP) until now. The 6cP type has been considered to be the most suitable for a tablet coating amongst the three types. The 3 cP type with a low degree of polymerization, is capable of providing high concentration, but the film strength is so inferior that sometimes cracking of the film may occur. On the other hand, in the case of the 15cP type, high polymer concentration cannot be achieved because of the high degree of polymerization, and thus it is uneconomical for coating. Now, there is a strong demand to reduce the coating time even when IIPMC is used in the 6cP type in order to reduce the coating cost. In order to improve this problem, we have concentrated our attention on reducing the viscosity value of HPMC to an allowable lower limit from 6cP. As a result of this study, it was found that the reduction of the viscosity value to around 4.5cP enabled the use of a higher solution concentration and an incidental shorter coating time without giving any substantial adverse effects on the properties of coated preparations. These experiment results are presented in the later part of this presentation. Based on this study, we have added the viscosity type of 4.5cP as one of the Pharmacoat products as Pharmacoat-645.
A REMARK ON QUASI CONTACT METRIC MANIFOLDS
박정형,Kouei Sekigawa,신원민 대한수학회 2015 대한수학회보 Vol.52 No.3
As a natural generalization of the contact metric manifolds, Kim, Park and Sekigawa discussed quasi contact metric manifolds based on the geometry of the corresponding quasi K¨ahler cones. In this paper, we show that a quasi contact metric manifold is a contact manifold.
Curvature identities derived from an integral formula for the first Chern number
이정찬,박정형,Kouei Sekigawa 대한수학회 2013 대한수학회보 Vol.50 No.4
We establish an integral formula for the first Chern number of a compact almost Hermitian surface and derive curvature identities from the integral formula. Further, we provide some results as applications of the identities.